U.S. patent application number 10/258906 was filed with the patent office on 2003-09-11 for method for measuring particle size of inclusion in metal by emission spectrum intensity of element constituting inclusion in metal, and method for forming particle size distribution of inclusion in metal, and apparatus for executing that method.
This patent application is currently assigned to NSK LTD.. Invention is credited to Nagasawa, Wataru.
Application Number | 20030168132 10/258906 |
Document ID | / |
Family ID | 26610701 |
Filed Date | 2003-09-11 |
United States Patent
Application |
20030168132 |
Kind Code |
A1 |
Nagasawa, Wataru |
September 11, 2003 |
Method for measuring particle size of inclusion in metal by
emission spectrum intensity of element constituting inclusion in
metal, and method for forming particle size distribution of
inclusion in metal, and apparatus for executing that method
Abstract
An electron probe microanalyzer determines the particle size of
intermetallic inclusions in a master while scanning an area of
.phi.5 mm located at an arbitrary location on the surface of the
master. A calibration curve representative of the relationship
between the particle size of intermetallic inclusions and the
emission spectrum intensity of an constituent element constituting
intermetallic inclusions is generated based on the determined
particle size of the intermetallic inclusions. Intermetallic
inclusions existing on emission spots on the surface of a test
sample are specified based on data of emission spectrum intensity
of an element existing on the emission spots, and a particle size
of the specified intermetallic inclusions is determined based on
the data of emission spectrum intensity and the generated
calibration curve.
Inventors: |
Nagasawa, Wataru;
(Fujisawa-shi, JP) |
Correspondence
Address: |
FRISHAUF, HOLTZ, GOODMAN & CHICK, PC
767 THIRD AVENUE
25TH FLOOR
NEW YORK
NY
10017-2023
US
|
Assignee: |
NSK LTD.
Tokyo
JP
|
Family ID: |
26610701 |
Appl. No.: |
10/258906 |
Filed: |
January 21, 2003 |
PCT Filed: |
March 6, 2002 |
PCT NO: |
PCT/JP02/02085 |
Current U.S.
Class: |
148/508 ;
266/79 |
Current CPC
Class: |
G01N 15/02 20130101;
G01N 21/66 20130101; G01N 15/14 20130101; G01N 15/0227 20130101;
G01N 21/63 20130101 |
Class at
Publication: |
148/508 ;
266/79 |
International
Class: |
C21B 007/24 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 6, 2001 |
JP |
2001-062099 |
Sep 7, 2001 |
JP |
2001-271723 |
Claims
1. A particle size-determining method for determining a particle
size of intermetallic inclusions based on an emission spectrum
intensity of a constituent element of the intermetallic inclusions,
the particle size-determining method comprising the steps of:
determining a particle size of the intermetallic inclusions, which
is known, in a predetermined area of a reference sample;
determining an intensity of emission spectra emitted from the
constituent element of the intermetallic inclusions, from a
relationship thereof to an intensity of emission spectra from spark
discharge spots within the predetermined area, through emission
spectral analysis of the reference sample; and forming an inclusion
particle size-intensity calibration curve representative of
relationship between the particle size of the intermetallic
inclusions and the emission spectrum intensity of the constituent
element of the intermetallic inclusions.
2. A particle size-determining method according to claim 1, wherein
the particle size of the intermetallic inclusions, which is known,
in the predetermined area of the reference sample is determined
through surface analysis by an electron probe microanalyzer.
3. A particle size-determining method for determining a particle
size of intermetallic inclusions based on an emission spectrum
intensity of a constituent element of the intermetallic inclusions,
the particle size-determining method comprising the steps of:
determining an intensity of emission spectra emitted from a
principle component having an already known concentration and
contained in a reference sample having an already known
concentration in spark discharge spots within a predetermined area
of the reference sample, through emission spectral analysis of the
reference sample; forming a principle component known
concentration-intensity calibration curve representative of
relationship between the emission spectrum intensity of the
principle component having an already known concentration and the
known concentration of the principle component; determining an
intensity of emission spectra emitted from a principle component
contained in a real steel material-reference sample in spark
discharge spots within a predetermined area of the real steel
material-reference sample, and an intensity of emission spectra
emitted from a constituent element of intermetallic inclusions
contained in the real steel material-reference sample, through
emission spectral analysis of the real steel material-reference
sample; calculating a concentration of the principle component
contained in the real steel material-reference sample from the
emission spectrum intensity of the principle component of the real
steel material-reference sample, based on the principle component
known concentration-intensity calibration curve; calculating a
concentration of the constituent element of the intermetallic
inclusions contained in the real steel material-reference sample,
based on the calculated concentration of the principle component of
the real steel material-reference sample; forming a real steel
material-contained intermetallic inclusion constituent element
concentration-intensity calibration curve representative of
relationship between the concentration of the constituent element
of the intermetallic inclusions and the emission spectrum intensity
of the constituent element of the intermetallic inclusions;
determining an intensity of emission spectra emitted from a base
element of a real steel material-pure base sample in spark
discharge spots within a predetermined area of the real steel
material-pure base sample, and a base element evaporation amount
indicative of mass of the base element having been evaporated due
to spark discharge thereon, through emission spectral analysis of
the real steel material-pure base sample; and forming a base
element evaporation amount-intensity calibration curve
representative of relationship between the base element evaporation
amount and the intensity of emission spectra emitted from the base
element.
4. A particle size-determining method according to claim 3,
comprising the steps of: calculating a base element evaporation
volume indicative of a volume of the evaporated base element, from
the base element evaporation amount based on a density of the base
element, and calculating, from the base element evaporation volume,
a particle size of the intermetallic inclusions as a diameter
thereof corresponding to the base element evaporation volume, based
on a formula of calculating a spherical volume; determining a known
concentration of the principle component from the emission spectrum
intensity of the base element, based on the principle component
known concentration-intensity calibration curve; calculating a
concentration of the constituent element of the intermetallic
inclusions based on the determined known concentration of the
principle component; determining an intensity of emission spectra
of the constituent element of the intermetallic inclusions from the
calculated concentration of the constituent element of the
intermetallic inclusion, based on the real steel material-contained
intermetallic inclusion constituent element concentration-intensity
calibration curve; and forming an intermetallic inclusion particle
size-intensity calibration curve representative of relationship
between the calculated particle size of the intermetallic
inclusions and the determined emission spectrum intensity of the
constituent element of the intermetallic inclusions.
5. A particle size distribution-generating method for generating a
particle size distribution of intermetallic inclusions, comprising
the steps of: executing a data sorting process for counting a
number of data items of emission spectra of a constituent element
of the intermetallic inclusions in a test sample; and generating a
particle size distribution based on the counted number of the data
items and the particle size of the intermetallic inclusions in the
test sample, which have been determined by the particle
size-determining method according to any of claims 1 to 4.
6. A particle size distribution-generating method according to
claim 5, wherein in the data sorting process, the data items of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample are rearranged in order of intensity,
and then the number of the rearranged data items is counted.
7. A particle size distribution-generating method according to
claim 5 or 6, wherein in the data sorting process, it is determined
whether or not an emission spectrum intensity of the constituent
element of the intermetallic inclusions in the test sample is
larger than a threshold value, and then data items of intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample to be rearranged in order of
intensity are extracted based on a result of the determination.
8. A particle size distribution-generating method according to
claim 5 or 6, further comprising the step of determining an
intensity of emission spectra emitted from a principle component
contained in the test sample; and wherein in the data sorting
process, the data items of intensity of emission spectra of the
constituent element of the intermetallic inclusions in the test
sample to be rearranged in order of intensity are extracted based
on a result of comparison between the intensity of emission spectra
emitted from the principle component contained in the test sample
and the intensity of emission spectra of the constituent element of
the intermetallic inclusions in the test sample.
9. A particle size distribution-generating method according to any
of claims 5 to 8, further comprising the steps of: forming an
intensity correction curve representative of relationship between a
number of times of generation of spark discharge for emission
spectral analysis and an amount of attenuation of an intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample after carrying out the spark
discharge; and correcting the intensity of emission spectra of the
constituent element of the intermetallic inclusions in the test
sample according to the number of times of generation of spark
discharge for emission spectral analysis, based on the generated
intensity correction curve.
10. A particle size distribution-generating method according to any
of claims 5 to 9, wherein a kind of the constituent element of the
intermetallic inclusions contained in the test sample is identified
based on a result of comparison between the intensity of emission
spectra emitted from the principle component contained in the test
sample and the intensity of emission spectra of the constituent
element of the intermetallic inclusions in the test sample.
11. A particle size-determining apparatus for determining a
particle size of intermetallic inclusions based on an emission
spectrum intensity of a constituent element of the intermetallic
inclusions, the particle size-determining apparatus comprising:
acquiring means for acquiring a particle size of the intermetallic
inclusions, which is known, in a predetermined area of a reference
sample; acquiring means for acquiring an intensity of emission
spectra emitted from the constituent element of the intermetallic
inclusions, from a relationship thereof to an intensity of emission
spectra from spark discharge spots within the predetermined area,
through emission spectral analysis of the reference sample; and
forming means for forming an inclusion particle size-intensity
calibration curve representative of relationship between the
particle size of the intermetallic inclusions and the emission
spectrum intensity of the constituent element of the intermetallic
inclusions.
12. A particle size-determining apparatus according to claim 11,
comprising acquiring means for acquiring the particle size of the
intermetallic inclusions, which is known, in the predetermined area
of the reference sample through surface analysis by an electron
probe microanalyzer.
13. A particle size-determining apparatus for determining a
particle size of intermetallic inclusions based on an emission
spectrum intensity of a constituent element of the intermetallic
inclusions, the particle size-determining apparatus comprising:
acquiring means for acquiring an intensity of emission spectra
emitted from a principle component having an already known
concentration and contained in a reference sample having an already
known concentration in spark discharge spots within a predetermined
area of the reference sample, through emission spectral analysis of
the reference sample; forming means for forming a principle
component known concentration-intensity calibration curve
representative of relationship between the emission spectrum
intensity of the principle component having an already known
concentration and the known concentration of the principle
component; acquiring means for acquiring an intensity of emission
spectra emitted from a principle component contained in a real
steel material-reference sample in spark discharge spots within a
predetermined area of the real steel material-reference sample, and
an intensity of emission spectra emitted from a constituent element
of intermetallic inclusions contained in the real steel
material-reference sample, through emission spectral analysis of
the real steel material-reference sample; calculating means for
calculating a concentration of the principle component contained in
the real steel material-reference sample from the emission spectrum
intensity of the principle component of the real steel
material-reference sample, based on the principle component known
concentration-intensity calibration curve; calculating means for
calculating a concentration of the constituent element of the
intermetallic inclusions contained in the real steel
material-reference sample, based on the calculated concentration of
the principle component of the real steel material-reference
sample; forming means for forming a real steel material-contained
intermetallic inclusion constituent element concentration-intensity
calibration curve representative of relationship between the
concentration of the constituent element of the intermetallic
inclusions and the emission spectrum intensity of the constituent
element of the intermetallic inclusions; acquiring means for
acquiring an intensity of emission spectra emitted from a base
element of a real steel material-pure base sample in spark
discharge spots within a predetermined area of the real steel
material-pure base sample, and a base element evaporation amount
indicative of mass of the base element having been evaporated due
to spark discharge thereon, through emission spectral analysis of
the real steel material-pure base sample; and forming means for
forming a base element evaporation amount-intensity calibration
curve representative of relationship between the base element
evaporation amount and the intensity of emission spectra emitted
from the base element.
14. A particle size-determining apparatus according to claim 13,
comprising: calculating means for calculating a base element
evaporation volume indicative of a volume of the evaporated base
element, from the base element evaporation amount based on a
density of the base element, and calculating, from the base element
evaporation volume, a particle size of the intermetallic inclusions
as a diameter thereof corresponding to the base element evaporation
volume, based on a formula of calculating a spherical volume;
acquiring means for acquiring a known concentration of the
principle component from the emission spectrum intensity of the
base element, based on the principle component known
concentration-intensity calibration curve; calculating means for
calculating a concentration of the constituent element of the
intermetallic inclusions based on the determined known
concentration of the principle component; acquiring means for
acquiring an intensity of emission spectra of the constituent
element of the intermetallic inclusions from the calculated
concentration of the constituent element of the intermetallic
inclusion, based on the real steel material-contained intermetallic
inclusion constituent element concentration-intensity calibration
curve; and forming means for forming an intermetallic inclusion
particle size-intensity calibration curve representative of
relationship between the calculated particle size of the
intermetallic inclusions and the determined emission spectrum
intensity of the constituent element of the intermetallic
inclusions.
15. A particle size distribution-generating apparatus for
generating a particle size distribution of intermetallic
inclusions, comprising: data sorting means for executing a data
sorting process for counting a number of data items of emission
spectra of a constituent element of the intermetallic inclusions in
a test sample; and generating means for generating a particle size
distribution based on the counted number of the data items and the
particle size of the intermetallic inclusions in the test sample,
which have been determined by the particle size-determining
apparatus for determining a particle size of intermetallic
inclusions based on an emission spectrum intensity of a constituent
element of the intermetallic inclusions, according to any of claims
11 to 14.
16. A particle size distribution-generating apparatus according to
claim 15, wherein said data sorting means rearranges the data items
of emission spectra of the constituent element of the intermetallic
inclusions in the test sample counts the number of the rearranged
data items.
17. A particle size distribution-generating apparatus according to
claim 15 or 16, wherein said data sorting means determines whether
or not an emission spectrum intensity of the constituent element of
the intermetallic inclusions in the test sample is larger than a
threshold value, and then extracts data items of intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample to be rearranged in order of
intensity, based on a result of the determination.
18. A particle size distribution-generating apparatus according to
claim 15 or 16, further comprising acquiring means for acquiring an
intensity of emission spectra emitted from a principle component
contained in the test sample; and wherein said data sorting means
extracts the data items of intensity of emission spectra of the
constituent element of the intermetallic inclusions in the test
sample to be rearranged in order of intensity, based on a result of
comparison between the intensity of emission spectra emitted from
the principle component contained in the test sample and the
intensity of emission spectra of the constituent element of the
intermetallic inclusions in the test sample.
19. A particle size distribution-generating apparatus according to
any of claims 15 to 18, further comprising: forming means for
forming an intensity correction curve representative of
relationship between a number of times of generation of spark
discharge for emission spectral analysis and an amount of
attenuation of an intensity of emission spectra of the constituent
element of the intermetallic inclusions in the test sample after
carrying out the spark discharge; and correcting means for
correcting the intensity of emission spectra of the constituent
element of the intermetallic inclusions in the test sample
according to the number of times of generation of spark discharge
for emission spectral analysis, based on the generated intensity
correction curve.
20. A particle size distribution-generating apparatus according to
any of claims 15 to 19, comprising identifying means for
identifying a kind of the constituent element of the intermetallic
inclusions contained in the test sample, based on a result of
comparison between the intensity of emission spectra emitted from
the principle component contained in the test sample and the
intensity of emission spectra of the constituent element of the
intermetallic inclusions in the test sample.
Description
TECHNICAL FIELD
[0001] This invention relates to a method of determining particle
sizes of non-metallic inclusions dispersed in metal materials
(hereinafter referred to as an "intermetallic inclusions") based on
emission spectrum intensities of constituent elements of the
intermetallic inclusions, and a method of generating particle size
distributions of the intermetallic inclusions, as well as to
apparatuses for performing the methods, and more particularly to a
method of determining particle sizes of intermetallic inclusions
based on emission spectrum intensities of constituent elements of
the intermetallic inclusions by using an emission spectral analysis
method, and a method of generating particle size distributions of
intermetallic inclusions, as well as to apparatuses for performing
the methods.
BACKGROUND ART
[0002] In general, a steel material contains various kinds of
intermetallic inclusions dispersed therein. The compositions as
well as the particle sizes of the compositions and the particle
size distribution of these intermetallic inclusions seriously
affect the quality of the steel material, particularly the pureness
of roller bearings when the steel material is used as a material
for the roller bearings. Therefore, to maintain the pureness of the
steel material, it is important to identify the composition of each
intermetallic inclusion in the steel material and determine the
particle size distribution of intermetallic inclusions existing in
a predetermined area of the steel material, i.e. to determine or
measure the number of intermetallic inclusions existing in the
steel material for each predetermined particle size. For example,
when a steel material for roller bearings contains a large number
of intermetallic inclusions having relatively large particle sizes
of more than 3 .mu.m, peeling or the like easily occurs at these
intermetallic inclusions, which results in considerable
deterioration in the pureness of products, such as roller
bearings.
[0003] Therefore, the reduction of the number of intermetallic
inclusions, i.e. high pureness, is demanded of steel materials, and
hence it is essential to accurately and quickly determine the
compositions and particle sizes of intermetallic inclusions and a
particle size distribution of intermetallic inclusions in a steel
material.
[0004] Conventionally, as a method of determining the compositions
and particle sizes of intermetallic inclusions and a particle size
distribution of the intermettalic inclusions, there are known a
method using an electron probe microanalyzer (EPMA) and a method
using emission spectral analysis. Particularly, the method using
emission spectral analysis identifies respective compositions of
intermetallic inclusions by separating an emission spectrum emitted
from intermetallic inclusions contained in a steel material which
was subjected to spark discharge, into emission spectra specific to
respective elements, and therefore, the method is advantageous in
that the composition of each intermetallic inclusion can be
identified speedily, and therefore, a number of methods using
emission spectral analysis have been disclosed e.g. in "Iron and
Steel vol. 73 (1987) S696, S670", "CAMP-IsIJ vol. 7 (1994) 1292,
1293", and Japanese Laid-Open Patent Publications (Kokai) Nos.
4-238250 and 9-43150.
[0005] Of these methods, a method described in Japanese Laid-Open
Patent Publication (Kokai) No. 4-238250 measures, in time sequence,
ones of emission spectra obtained by spark discharge which
correspond to zero to several hundreds of pulses corresponding to
an initial stage of the spark discharge, and then determines the
number of intermetallic inclusions and the compositions and
contents of intermetallic inclusions, based on ones of the measured
emission spectra falling within a predetermined intensity range,
using predetermined equations.
[0006] However, the method using an EPMA requires a complicated
procedure including operations of electronic probing and various
arithmetic operations, and hence this method cannot speedily
determine the composition and particle size distribution of each of
intermetallic inclusions contained in a large amount of samples cut
out from steel materials.
[0007] Further, the method described in Japanese Laid-Open Patent
Publication (Kokai) No. 4-238250 separates emission spectra emitted
from intermetallic inclusions contained in a steel material
subjected to a spark discharge generated under discharge conditions
adapted to the steel material, into emission spectra specific to
respective elements, identifies the composition of the
intermetallic inclusions based on the wavelength and/or intensity
of the obtained emission spectra inherent to the respective
elements, and then determines the concentration of each constituent
element and the particle sizes of the intermetallic inclusions.
However, as is distinct from the present invention which is
directed to a real steel material by using a calibration
relationship in a high-concentration region, the disclosed method
carries out extrapolation of a calibration relationship in a trace
concentration region. The extrapolation makes it difficult for the
disclosed method to correctly determine the particle sizes and the
particle size distribution.
[0008] Further, when it is required to perform quick and accurate
determination of particle sizes and a particle size distribution of
intermetallic inclusions, there has been used a calibration curve
concerning concentrations e.g. of not more than 500 ppm of a
specific metal element constituting the intermetallic inclusions,
i.e. a calibration curve concerning concentrations of a specific
metal element of the intermetallic inclusions, which is obtained
from a trace amount of a master, and hence when it is necessary to
carry out the identification even in a high concentration region
where the concentration of the metal element of the intermetallic
inclusions is high, as in the case of determining particle sizes
and a particle size distribution of the intermetallic inclusions,
there is no choice but to estimate the calibration relationship up
to the high concentration region by extrapolation used in the low
concentration region, which makes the calibration relationship
inaccurate. For this reason, the use of an alloy as a master which
has a high concentration of a certain metal element falling within
a known range in intermetallic inclusions, e.g. the use of an
Al-based alloy as the master in the case of Al being a constituent
element of intermetallic inclusions, may be contemplated so as to
obtain a calibration relationship in a region where the
concentration of the metal element in intermetallic inclusions is
high. However, when it is necessary to obtain an Al calibration
curve, since the background of the Al-based alloy is not iron (Fe),
it is difficult to accurately determine Al contained in the
intermetallic inclusions existing in the steel. Moreover, due to
existence of a high emission spectrum intensity of an element, such
as Mg, whose emission wavelength is close to that of Al, it is
difficult to correctly identify the concentration of Al.
[0009] Further, there is another conventional determination method
in which after a steel material is cut out as test samples, the
surface of the steel material is polished to form a mirror finished
surface, and then the formed mirror finished surface is inspected
by an optical microscope and then the inspection results are
subjected to image analysis to thereby determine the average
particle size of Al.sub.2O.sub.3 or other intermetallic inclusions
and the particle size distribution of the intermetallic inclusions.
However, since the mirror finished surface is thus formed by
polishing the surface of the steel material and then the particle
sizes and particle size distribution of the Al.sub.2O.sub.3 or
other intermetallic inclusions are determined on the mirror
finished surface, a surface of an Al.sub.2O.sub.3 or other
intermetallic inclusion corresponding to its particle size (real
particle size) may not be exposed on the mirror finished surface.
Therefore, although the manner of preparing test samples is simple,
the determination can be performed easily, and a passably accurate
average particle size can be determined (see FIG. 4) so long as an
appropriate averaging method and an appropriate statistical method
are used, the average particle size obtained by the method may be
estimated as a smaller apparent particle size than the real
particle size.
[0010] From the viewpoint that the real particle size (obtained by
calculating a spherical diameter from the volume of an
intermetallic inclusion particle), such as the maximum particle
size and the average particle size, is the very size closely
related to the rolling life, the average particle size of the
Al.sub.2O.sub.3 or other intermetallic inclusions, obtained through
the image analysis is estimated to be smaller than the real
particle size as described above. Since the correlation between the
average particle size thus estimated to be smaller and the real
particle size cannot be clearly determined, the relationship
between the average particle size estimated to be smaller and the
rolling life may not be accurately determined.
[0011] Methods for directly determining the particle size of
intermetallic inclusions include a method in which intermetallic
inclusions e.g. of Al.sub.2O.sub.3 are extracted from a steel
material providing test samples, by an electron beam elution method
or a chemical extraction method, into grains. However, it is
difficult to carry out these methods conveniently, since the
electron beam elution method necessitates an apparatus for
performing the same method, and/or it takes time to effect the
elution or extraction.
[0012] It is an object of the present invention to provide a method
of determining particle sizes of intermetallic inclusions based on
emission spectrum intensities of constituent elements of the
intermetallic inclusions, and a method of generating a particle
size distribution of the intermetallic inclusions, as well as
apparatuses for performing the methods, which are capable of
identifying what form is assumed by the intermetallic inclusions
from the constituent elements of the intermetallic inclusions, and
quickly and accurately determining the particle sizes and particle
size distribution of the intermetallic inclusions.
[0013] It is another object of the invention to provide a method of
determining particle sizes of intermetallic inclusions based on an
emission spectrum intensities of constituent elements of the
intermetallic inclusions, and a method of generating a particle
size distribution of the intermetallic inclusions, as well as
apparatuses for performing the methods, which are capable of
quickly and accurately determining real particle sizes and a
particle size distribution of the intermetallic inclusions.
DISCLOSURE OF INVENTION
[0014] To attain the first-mentioned object, a particle
size-determining method as recited in claim 1 is characterized by
comprising the steps of determining a particle size of the
intermetallic inclusions, which is known, in a predetermined area
of a reference sample, determining an intensity of emission spectra
emitted from the constituent element of the intermetallic
inclusions, from a relationship thereof to an intensity of emission
spectra from spark discharge spots within the predetermined area,
through emission spectral analysis of the reference sample, and
forming an inclusion particle size-intensity calibration curve
representative of the relationship between the particle size of the
intermetallic inclusions and the emission spectrum intensity of the
constituent element of the intermetallic inclusions.
[0015] Preferably, the particle size of the intermetallic
inclusions, which is known, in the predetermined area of the
reference sample is determined through surface analysis by an
electron probe microanalyzer.
[0016] To attain the above other object, a particle
size-determining method as recited in claim 3 is characterized by
comprising the steps of determining an intensity of emission
spectra emitted from a principle component having an already known
concentration and contained in a reference sample having an already
known concentration in spark discharge spots within a predetermined
area of the reference sample, through emission spectral analysis of
the reference sample, forming a principle component known
concentration-intensity calibration curve representative of the
relationship between the emission spectrum intensity of the
principle component having an already known concentration and the
known concentration of the principle component, determining an
intensity of emission spectra emitted from a principle component
contained in a real steel material-reference sample in spark
discharge spots within a predetermined area of the real steel
material-reference sample, and an intensity of emission spectra
emitted from a constituent element of intermetallic inclusions
contained in the real steel material-reference sample, through
emission spectral analysis of the real steel material-reference
sample, calculating a concentration of the principle component
contained in the real steel material-reference sample from the
emission spectrum intensity of the principle component of the real
steel material-reference sample, based on the principle component
known concentration-intensity calibration curve, calculating a
concentration of the constituent element of the intermetallic
inclusions contained in the real steel material-reference sample,
based on the calculated concentration of the principle component of
the real steel material-reference sample, forming a real steel
material-contained intermetallic inclusion constituent element
concentration-intensity calibration curve representative of the
relationship between the concentration of the constituent element
of the intermetallic inclusions and the emission spectrum intensity
of the constituent element of the intermetallic inclusions,
determining an intensity of emission spectra emitted from a base
element of a real steel material-pure base sample in spark
discharge spots within a predetermined area of the real steel
material-pure base sample, and a base element evaporation amount
indicative of mass of the base element having been evaporated due
to spark discharge thereon, through emission spectral analysis of
the real steel material-pure base sample, and forming a base
element evaporation amount-intensity calibration curve
representative of the relationship between the base element
evaporation amount and the intensity of emission spectra emitted
from the base element.
[0017] Preferably, the particle size-determining method comprising
the steps of calculating a base element evaporation volume
indicative of a volume of the evaporated base element, from the
base element evaporation amount based on a density of the base
element, and calculating, from the base element evaporation volume,
a particle size of the intermetallic inclusions as a diameter
thereof corresponding to the base element evaporation volume, based
on a formula of calculating a spherical volume, determining a known
concentration of the principle component from the emission spectrum
intensity of the base element, based on the principle component
known concentration-intensity calibration curve, calculating a
concentration of the constituent element of the intermetallic
inclusions based on the determined known concentration of the
principle component, determining an intensity of emission spectra
of the constituent element of the intermetallic inclusions from the
calculated concentration of the constituent element of the
intermetallic inclusion, based on the real steel material-contained
intermetallic inclusion constituent element concentration-intensity
calibration curve, and forming an intermetallic inclusion particle
size-intensity calibration curve representative of the relationship
between the calculated particle size of the intermetallic
inclusions and the determined emission spectrum intensity of the
constituent element of the intermetallic inclusions.
[0018] To attain the first-mentioned object, a particle size
distribution-generating method as recited in claim 5 is
characterized by comprising the steps of executing a data sorting
process for counting a number of data items of emission spectra of
a constituent element of the intermetallic inclusions in a test
sample, and generating a particle size distribution based on the
counted number of the data items and the particle size of the
intermetallic inclusions in the test sample, which have been
determined by any of the particle size-determining methods
described above.
[0019] Preferably, in the data sorting process, the data items of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample are rearranged in order of intensity,
and then the number of the rearranged data items is counted.
[0020] More preferably, in the data sorting process, it is
determined whether or not an emission spectrum intensity of the
constituent element of the intermetallic inclusions in the test
sample is larger than a threshold value, and then data items of
intensity of emission spectra of the constituent element of the
intermetallic inclusions in the test sample to be rearranged in
order of intensity are extracted based on a result of the
determination.
[0021] More preferably, the particle size distribution-generating
method as recited in claim 8 further comprising the step of
determining an intensity of emission spectra emitted from a
principle component contained in the test sample, and in the data
sorting process, the data items of intensity of emission spectra of
the constituent element of the intermetallic inclusions in the test
sample to be rearranged in order of intensity are extracted based
on a result of comparison between the intensity of emission spectra
emitted from the principle component contained in the test sample
and the intensity of emission spectra of the constituent element of
the intermetallic inclusions in the test sample.
[0022] More preferably, the particle size distribution-generating
method further comprising the steps of forming an intensity
correction curve representative of the relationship between a
number of times of generation of spark discharge for emission
spectral analysis and an amount of attenuation of an intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample after carrying out the spark
discharge, and correcting the intensity of emission spectra of the
constituent element of the intermetallic inclusions in the test
sample according to the number of times of generation of spark
discharge for emission spectral analysis, based on the generated
intensity correction curve.
[0023] More preferably, a kind of the constituent element of the
intermetallic inclusions contained in the test sample is identified
based on a result of comparison between the intensity of emission
spectra emitted from the principle component contained in the test
sample and the intensity of emission spectra of the constituent
element of the intermetallic inclusions in the test sample.
[0024] To attain the first-mentioned object, a particle
size-determining apparatus as recited in claim 11 is characterized
by comprising acquiring means for acquiring a particle size of the
intermetallic inclusions, which is known, in a predetermined area
of a reference sample, acquiring means for acquiring an intensity
of emission spectra emitted from the constituent element of the
intermetallic inclusions, from a relationship thereof to an
intensity of emission spectra from spark discharge spots within the
predetermined area, through emission spectral analysis of the
reference sample, and forming means for forming an inclusion
particle size-intensity calibration curve representative of the
relationship between the particle size of the intermetallic
inclusions and the emission spectrum intensity of the constituent
element of the intermetallic inclusions.
[0025] Preferably, the particle size-determining apparatus
comprises acquiring means for acquiring the particle size of the
intermetallic inclusions, which is known, in the predetermined area
of the reference sample through surface analysis by an electron
probe microanalyzer.
[0026] To attain the above other object, a particle
size-determining apparatus as recited in claim 13 is characterized
by comprising acquiring means for acquiring an intensity of
emission spectra emitted from a principle component having an
already known concentration and contained in a reference sample
having an already known concentration in spark discharge spots
within a predetermined area of the reference sample, through
emission spectral analysis of the reference sample, forming means
for forming a principle component known concentration-intensity
calibration curve representative of the relationship between the
emission spectrum intensity of the principle component having an
already known concentration and the known concentration of the
principle component, acquiring means for acquiring an intensity of
emission spectra emitted from a principle component contained in a
real steel material-reference sample in spark discharge spots
within a predetermined area of the real steel material-reference
sample, and an intensity of emission spectra emitted from a
constituent element of intermetallic inclusions contained in the
real steel material-reference sample, through emission spectral
analysis of the real steel material-reference sample, calculating
means for calculating a concentration of the principle component
contained in the real steel material-reference sample from the
emission spectrum intensity of the principle component of the real
steel material-reference sample, based on the principle component
known concentration-intensity calibration curve, calculating means
for calculating a concentration of the constituent element of the
intermetallic inclusions contained in the real steel
material-reference sample, based on the calculated concentration of
the principle component of the real steel material-reference
sample, forming means for forming a real steel material-contained
intermetallic inclusion constituent element concentration-intensity
calibration curve representative of the relationship between the
concentration of the constituent element of the intermetallic
inclusions and the emission spectrum intensity of the constituent
element of the intermetallic inclusions, acquiring means for
acquiring an intensity of emission spectra emitted from a base
element of a real steel material-pure base sample in spark
discharge spots within a predetermined area of the real steel
material-pure base sample, and a base element evaporation amount
indicative of mass of the base element having been evaporated due
to spark discharge thereon, through emission spectral analysis of
the real steel material-pure base sample, and forming means for
forming a base element evaporation amount-intensity calibration
curve representative of the relationship between the base element
evaporation amount and the intensity of emission spectra emitted
from the base element.
[0027] Preferably, the particle size-determining apparatus
comprises calculating means for calculating a base element
evaporation volume indicative of a volume of the evaporated base
element, from the base element evaporation amount based on a
density of the base element, and calculating, from the base element
evaporation volume, a particle size of the intermetallic inclusions
as a diameter thereof corresponding to the base element evaporation
volume, based on a formula of calculating a spherical volume,
acquiring means for acquiring a known concentration of the
principle component from the emission spectrum intensity of the
base element, based on the principle component known
concentration-intensity calibration curve, calculating means for
calculating a concentration of the constituent element of the
intermetallic inclusions based on the determined known
concentration of the principle component, acquiring means for
acquiring an intensity of emission spectra of the constituent
element of the intermetallic inclusions from the calculated
concentration of the constituent element of the intermetallic
inclusion, based on the real steel material-contained intermetallic
inclusion constituent element concentration-intensity calibration
curve, and forming means for forming an intermetallic inclusion
particle size-intensity calibration curve representative of the
relationship between the calculated particle size of the
intermetallic inclusions and the determined emission spectrum
intensity of the constituent element of the intermetallic
inclusions.
[0028] To attain the first-mentioned object, a particle size
distribution-generating apparatus as recited in claim 15 is
characterized by comprising data sorting means for executing a data
sorting process for counting a number of data items of emission
spectra of a constituent element of the intermetallic inclusions in
a test sample, and generating means for generating a particle size
distribution based on the counted number of the data items and the
particle size of the intermetallic inclusions in the test sample,
which have been determined by the particle size-determining
apparatuses described above.
[0029] Preferably, data sorting means rearranges the data items of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample counts the number of the rearranged
data items.
[0030] More Preferably, the data sorting means determines whether
or not an emission spectrum intensity of the constituent element of
the intermetallic inclusions in the test sample is larger than a
threshold value, and then extracts data items of intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample to be rearranged in order of
intensity, based on a result of the determination.
[0031] More preferably, the particle size distribution-generating
apparatus further comprises acquiring means for acquiring an
intensity of emission spectra emitted from a principle component
contained in the test sample, and the data sorting means extracts
the data items of intensity of emission spectra of the constituent
element of the intermetallic inclusions in the test sample to be
rearranged in order of intensity, based on a result of comparison
between the intensity of emission spectra emitted from the
principle component contained in the test sample and the intensity
of emission spectra of the constituent element of the intermetallic
inclusions in the test sample.
[0032] More preferably, the particle size distribution-generating
apparatus further comprises forming means for forming an intensity
correction curve representative of the relationship between a
number of times of generation of spark discharge for emission
spectral analysis and an amount of attenuation of an intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample after carrying out the spark
discharge, and correcting means for correcting the intensity of
emission spectra of the constituent element of the intermetallic
inclusions in the test sample according to the number of times of
generation of spark discharge for emission spectral analysis, based
on the generated intensity correction curve.
[0033] More preferably, the particle size distribution-generating
apparatus comprises identifying means for identifying a kind of the
constituent element of the intermetallic inclusions contained in
the test sample, based on a result of comparison between the
intensity of emission spectra emitted from the principle component
contained in the test sample and the intensity of emission spectra
of the constituent element of the intermetallic inclusions in the
test sample.
BRIEF DESCRIPTION OF DRAWINGS
[0034] FIG. 1 is a diagram schematically showing an emission
spectrometer for performing a particle size-determining and
particle size distribution-generating method according to a first
embodiment of the present invention;
[0035] FIG. 2 is a flowchart of a particle size-determining and
particle size distribution-generating process executed according to
the particle size-determining and particle size
distribution-generating method according to the first
embodiment;
[0036] FIG. 3 is a flowchart of a calibration curve A-forming
process, which is executed in a step S201 in FIG. 2, for forming a
calibration curve A representative of the relationship between the
Al.sub.2O.sub.3 particle size and the emission spectrum intensity
of Al;
[0037] FIG. 4 is a view schematically illustrating a surface
analysis result image of Al existing in Al.sub.2O.sub.3;
[0038] FIG. 5 is a diagram illustrating the calibration curve A
representative of the relationship between the Al.sub.2O.sub.3
particle size and the emission spectrum intensity of Al, which is
formed in a step S308 in FIG. 3;
[0039] FIG. 6 is, FIG. 6 is a flowchart of a particle size
distribution-generating process which is executed in a step S202 in
FIG. 2;
[0040] FIGS. 7A to 7E are diagrams illustrating distributions of
data items of emission spectrum intensities of Fe, O, Al, Ca and C,
which are arranged in time sequence, for comparison performed in a
step S605 in FIG. 6;
[0041] FIG. 8 is a flowchart of a data sorting process which is
executed in a step S606 in FIG. 6;
[0042] FIG. 9 is a continued part of the flowchart of the data
sorting process which is executed in the step S606 in FIG. 6;
[0043] FIG. 10 is a still continued part of the flowchart of the
data sorting process which is executed in the step S606 in FIG.
6;
[0044] FIG. 11 is a flowchart of a data sorting process which is
executed according to a variation of the particle size-determining
and particle size distribution-generating method according to the
first embodiment;
[0045] FIG. 12 is a flowchart of a particle size-determining and
particle size distribution-generating process which is executed
according to a particle size-determining and particle size
distribution-generating method according to a second embodiment of
the present invention;
[0046] FIG. 13 is a flowchart of a calibration curves B, C-forming
process which is executed in a step S1201 in FIG. 12 for forming a
calibration curve B representative of the relationship between the
Fe emission spectrum intensity and the Fe concentration and then
forming a calibration curve C representative of the relationship
between the Al emission spectrum intensity and the Al concentration
based on the calibration curve B;
[0047] FIG. 14 is a diagram illustrating the calibration curve B
representative of the relationship between the Fe emission spectrum
intensity and the Fe concentration, which is formed in the step
S1201 in FIG. 12;
[0048] FIG. 15 is a cross-sectional view taken on a section
orthogonal to the axis of a steel material for actual use, for
example, from which a real steel master is cut out in a step S1306
in the FIG. 13;
[0049] FIG. 16 is a flowchart of a calibration curve D-forming
process for forming a calibration curve D concerning the Fe
emission spectrum intensity and the Fe evaporation loss in a step
S1202 in FIG. 12;
[0050] FIG. 17 is a view useful for explaining a method of
determining a particle size of an intermetallic inclusion in a step
S1605 in FIG. 15;
[0051] FIG. 18 is a diagram illustrating a calibration curve D
representative of the relationship between the Fe evaporation
amount and the Fe emission spectrum intensity, which is formed in
the step S1202 in FIG. 12;
[0052] FIG. 19 is a flowchart of a calibration curve E-forming
process which is executed in a step S1203 in FIG. 12 for forming a
calibration curve E representative of the relationship between the
Al emission spectrum intensity and the Al particle size;
[0053] FIG. 20 is a flowchart of a particle size
distribution-generating process which is executed in a step S1204
in FIG. 12;
[0054] FIG. 21 is a diagram illustrating the calibration curve A
representative of the relationship between the Al.sub.2O.sub.3
particle size and the Al emission spectrum intensity, which is
formed in a step S1907 in FIG. 19;
[0055] FIG. 22 is a flowchart of a particle size-determining and
particle size distribution-generating process according to a third
embodiment of the present invention;
[0056] FIG. 23 is a flowchart of an intensity correction
curve-forming process which is executed in a step S2201 in FIG.
22;
[0057] FIG. 24 is a diagram illustrating an intensity correction
curve which is formed in the step S2201 in FIG. 22;
[0058] FIG. 25 is a flowchart of a particle size
distribution-generating process which is executed in a step S2202
in FIG. 22;
[0059] FIGS. 26A and 26B are diagrams useful in comparison between
an Al.sub.2O.sub.3 particle size distribution (a) generated by
execution of the FIG. 2 process and an Al.sub.2O.sub.3 particle
size distribution (b) generated by an EPMA; and
[0060] FIGS. 27A and 27B are diagrams useful in comparison between
the Al.sub.2O.sub.3 particle size distribution (a) generated by
execution of the FIG. 12 process and an Al.sub.2O.sub.3 particle
size distribution (b) generated by the image analysis method.
BEST MODE OF CARRYING OUT THE INVENTION
[0061] A particle size-determining and particle size
distribution-generating method according to a first embodiment of
the present invention will now be described in detail with
reference to the drawings.
[0062] The particle size-determining and particle size
distribution-generating method of the first embodiment is carried
out by an emission spectrometer shown in FIG. 1, described
hereinbelow, in generating a particle size distribution of
intermetallic inclusions contained in a test sample cut out from a
steel material.
[0063] The emission spectrometer for carrying out the particle
size-determining and particle size distribution-generating method
of the first embodiment will be described with reference to the
drawings.
[0064] FIG. 1 is a diagram schematically showing the arrangement of
the emission spectrometer for performing the particle
size-determining and particle size distribution-generating method
according to the first embodiment.
[0065] In FIG. 1, the emission spectrometer 100 is comprised of a
light-emitting section 101, a light-emitting stand 102, a spectral
section 103, a photometric section 104, an interface 105, a data
processing section 106, and a terminal unit 107.
[0066] The light-emitting section 101 is provided with a counter
electrode, not shown, while the light emitting stand 102 contains a
test sample or a master (reference sample) serving as an electrode.
The spectral section 103 is comprised of a condensing lens 108, a
light shielding plate 111 formed with an entrance slit 109 and a
plurality of exit slits 110, a concave diffraction grating 112, a
plurality of photomultipliers 113, and an oil rotary pump 114. The
terminal unit 107 includes a CRT, a printer, and a keyboard.
[0067] The light emitting stand 102 is connected to the interface
105 via the light-emitting section 101, and the photomultipliers
113 are connected to the interface 105 via the photometric section
104. The interface 105 is connected to the terminal unit 107 via
the data processing section 106.
[0068] The light-emitting section 101 is arranged at a location
where the counter electrode can generate a spark discharge on the
test sample or the master. The light emitting stand 102 is arranged
on an optical axis passing through the condensing lens 108, the
entrance slit 109, and the concave diffraction grating 112, and at
the same time on a surface of the spectral section 103. In the
spectral section 103, the exit slits 110 are arranged on optical
beams rotated about the concave diffraction grating 112 through
angles of diffraction specific to a plurality of elements,
respectively, from the optical axis passing through the condensing
lens 108, the entrance slit 109, and the concave diffraction
grating 112, and at the same time on the light shielding plate 111.
The photomultipliers 113 are positioned on the optical axes of the
respective optical beams.
[0069] Further, at least a space between the light-emitting section
101 and the light emitting stand 102 is filled with an inert rare
gas (e.g. argon gas).
[0070] The counter electrode of the light-emitting section 101
generates a spark discharge on the test sample or the master which
is held in the light emitting stand 102, and the test sample or the
master which is subjected to the spark discharge emits light of
emission spectra (emission spectra emitted respectively by iron
(Fe) or other main constituents of the test sample or the master
(hereinafter referred to as "ground")) and intermetallic
inclusions) containing information on a plurality of elements. The
condensing lens 108 converges the emitted light of emission spectra
and irradiates the concave diffraction grating 112 with the
converged light via the entrance slit 109. The concave diffraction
grating 112 separates the emitted light of emission spectra into
emission spectra specific to the respective elements by utilizing
the respective angles of diffraction specific thereto, and the
separated emission spectra enter the photomultipliers 113 via the
respective exit slits 110. The separated beams of the emission
spectra specific to the respective elements contain respective
pieces of optical information specific to the elements.
[0071] The photomultipliers 113 each detect the incoming emission
spectrum, convert the intensity of the detected emission spectrum
to an electric current value and transmit the converted current
value to the photometric section 104. The photometric section 104
converts the received current value to a digital value, and then
transmits the converted digital value to the data processing
section 106 via the interface 105. On the other hand, the
light-emitting section 101 and the light emitting stand 102
transmits data of the number of times and timing of generation of
spark discharge and data of positions on the surface of the test
sample or the master which were subjected to spark discharge to the
data processing section 106 via the interface 105.
[0072] The data processing section 106 carries out processing
including identification of the composition of each intermetallic
inclusion, based on the received digital values and so forth. The
CRT and a print printed by the printer display and indicates the
result of determination of the particle size distribution of
intermetallic inclusions.
[0073] Next, a particle size-determining and particle size
distribution-generating process which is executed on intermetallic
inclusions by the FIG. 1 emission spectrometer 100 will be
described with reference to the drawings.
[0074] FIG. 2 is a flowchart of the particle size-determining and
particle size distribution-generating process executed by the
particle size-determining and particle size distribution-generating
method of the first embodiment.
[0075] In FIG. 2, first, a calibration curve A-forming process for
forming a calibration curve A, described hereinbelow with reference
to FIG. 3, is executed (step S201), and then a particle size
distribution-generating process, described hereinafter with
reference to FIG. 6, is executed (step S202), followed by
terminating the process.
[0076] FIG. 3 is a flowchart of the calibration curve A-forming
process executed in the step S201 in FIG. 2, for forming the
calibration curve A representative of the relationship between the
Al.sub.2O.sub.3 particle size and the emission spectrum intensity
of Al.
[0077] The calibration curve A-forming process is executed by the
emission spectrometer 100 at least once before the particle size
distribution-generating process is repeatedly carried out on
intermetallic inclusions in the test sample by the emission
spectrometer 100.
[0078] In FIG. 3, first, steel materials of SUJ2 (high-carbon
chromium bearing steel, Type 2) containing Al.sub.2O.sub.3, for
example, having a particle size approximately equal to 4 to 18
.mu.m, which is a normal range of particle sizes of Al.sub.2O.sub.3
(alumina) contained in the test sample, are prepared, and masters
having a cylindrical shape with a diameter of .phi.40 mm are cut
out from the steel materials. After each master is held on a sample
stage of an EPMA (step S301), an area e.g. of .phi.5 mm is
arbitrarily set at an arbitrary location on the surface of the
master, and the location of the area is determined. Then, the area
is scanned by the EPMA for surface analysis thereof, whereby, when
the intermetallic inclusion concerned is Al.sub.2O.sub.3, the
location of Al is determined by the surface analysis, and then the
particle size of Al is determined by a method of determining an
average particle size of the intermetallic inclusion from an image
showing the location of Al, as described hereinbelow with reference
to FIG. 4 (step S302).
[0079] In the above example, it is assumed that the intermetallic
inclusion concerned is Al.sub.2O.sub.3, and Al is employed as an
element for identifying the intermetallic inclusion. Similarly, if
Ca is employed as an identifying element for CaO (calsia), Mg for
MgO (magnesia), Si for SiO.sub.2, Ca or S for CaS, Ti or N for TiN,
or Mn or S for MnS, and surface analysis using such an identifying
element provides a surface analysis result image concerning the
metal element of a corresponding intermetallic inclusion, thereby
similarly making it possible to determine the average particle size
thereof.
[0080] FIG. 4 schematically illustrates a surface analysis result
image of Al in Al.sub.2O.sub.3.
[0081] A description will be given of the method which is employed
in the step S302 in FIG. 3, for determining the particle size of an
intermetallic inclusion, with reference to FIG. 4.
[0082] In FIG. 4, the EPMA determines a major diameter d.sub.max of
an intermetallic inclusion 400 and a minor diameter d.sub.min of
the same, and based on these sizes, an average diameter d.sub.ave
is calculated as the particle size of the intermetallic inclusion
400 by using the following equation (1):
d.sub.ave=(d.sub.max+d.sub.min)/2 (1)
[0083] Referring again to FIG. 3, data of the location and particle
size of the intermetallic inclusion determined by surface analysis
and the identified constituent element of the intermetallic
inclusion are input to the data processing section 106 (step S303),
and the data processing section 106 stores the input data in a
memory, not shown.
[0084] Then, after the same master that was scanned by the EPMA is
held in the light emitting stand 102 (step S304), the counter
electrode of the light-emitting section 101 generates spark
discharge e.g. one hundred times at a surface area (set e.g. to
.phi.5 mm) of the surface of the master which is the same area that
was operated by the EPMA (step S305). The master subjected to the
spark discharge produces emission spectra containing information on
a plurality of elements. The intermetallic inclusion in the surface
of the master has a dielectric property, and hence at this time,
the spark discharge is selectively guided to the intermetallic
inclusion in the surface of the master by the dielectric property
(electrification) thereof. Accordingly, the emission spectra
generated by the master are emitted from respective discharge spots
(e.g. .phi.30 .mu.m) thereof containing the intermetallic
inclusion.
[0085] The above process will be explained by taking a case in
which the intermetallic inclusion is Al.sub.2O.sub.3, as an
example.
[0086] Since the size of Al.sub.2O.sub.3 is proportional to the
intensity of the emission spectrum of Al, emission spectrum
intensities of Al arranged in order in which the intensity of Al
decreases correspond respectively to average particle sizes of
Al.sub.2O.sub.3 which are obtained by the above-mentioned surface
analysis by the EPMA and arranged in order in which the size of
Al.sub.2O.sub.3 decreases. The data of the emission spectrum
intensities and the average particle sizes obtained earlier by the
EPMA are input to the memory of the data processing section 106,
and then these data are processed according to the intensity of Al
by the data processing section 106, whereby the calibration curve
A, referred to hereinafter in a step S308 and shown in FIG. 5, can
be obtained. Then, in a step S309, referred to hereinafter, the
obtained calibration curve A is stored in the memory of the data
processing section 106.
[0087] Referring again to FIGS. 3 and 4, an area (emission spot)
within the surface (the aforementioned area of .phi.5 mm) of the
master, on which spark discharge is effected once, is a circle of
.phi.30 .mu.m (the size is always held constant), and since this
emission spot has the diameter of .phi.30 .mu.m which is larger
than the average particle size d.sub.ave of general intermetallic
inclusions, the emission spot can always contain at least one
intermetallic inclusion therein, so that all the respective
emission spectrum intensities of elements constituting
intermetallic inclusions in the master can be obtained. This makes
it possible to properly associate the intermetallic inclusions from
which the emission spectra were obtained with the intermetallic
inclusions having the respective average particle sizes d.sub.ave,
which were obtained by the EPMA method.
[0088] This will be explained by referring again to FIG. 3. each of
emission spectra emitted by the master is separated into emission
spectra specific to the respective elements by the concave
diffraction grating 112, and the separated emission spectra enter
respective ones of the photomultipliers 113 via the corresponding
exit slits 110 (step S306).
[0089] Each photomultiplier 113 detects the incoming emission
spectrum, converts the intensity of the detected emission spectrum
to an electric current value, and transmits the current value
obtained by the conversion to the photometric section 104. The
photometric section 104 converts each of the received current
values to a digital value, and then transmits the digital values
obtained by the conversion to the data processing section 106 via
the interface 105 (step S307). On the other hand, the light
emitting stand 102 transmits data of the locations of emission
spots in the area of .phi.5 mm on the surface of the master, i.e.
the locations of intermetallic inclusions to the data processing
section 106 via the interface 105. Thus, the data of the respective
intensities of emission spectra of the elements constituting each
of the intermetallic inclusions and the data of the locations of
the intermetallic inclusions are transmitted to the data processing
section 106, and stored in the memory of the same.
[0090] Then, based on the data of the locations and particle sizes
of the intermetallic inclusions and the data of the constituent
elements of the intermetallic inclusions and the emission spectrum
intensities of the constituent elements, which are stored in the
memory, the data processing section 106 generates the FIG. 5
calibration curve A, described hereinbelow, which represents the
relationship between the emission spectrum intensity and particle
size of one of the elements constituting the intermetallic
inclusions as described hereinabove (step S308). Further, the data
processing section 106 stores the generated calibration curve A in
the memory (step S309), followed by terminating the process.
[0091] FIG. 5 is a diagram illustrating the calibration curve A
formed in the step S308 in FIG. 3. The calibration curve A
indicates the relationship between the Al.sub.2O.sub.3 particle
size and the emission spectrum intensity of Al.
[0092] In FIG. 5, the ordinate represents Al.sub.2O.sub.3 particle
sizes determined by the surface analysis by the EPMA, while the
abscissa represents the emission spectrum intensities of Al
contained in Al.sub.2O.sub.3, which correspond to the respective
Al.sub.2O.sub.3 particle sizes.
[0093] In FIG. 5, the data of the particle sizes of the
intermetallic inclusions determined by the surface analysis by the
EPMA method and the data of the emission spectrum intensities of
the constituent element existing in the intermetallic inclusions
are related to each other via the data of the locations and the
data on the constituent element of the intermetallic inclusions.
The data of the particle sizes of intermetallic inclusions are
represented by the ordinate, and the data of the emission spectrum
intensities of one of the elements forming the intermetallic
inclusions are represented by the abscissa. In the step S307, if
the determination by surface analysis is carried out on Al by using
masters containing Al.sub.2O.sub.3, it is possible to obtain a
calibration curve concerning Al.sub.2O.sub.3, and if the
determination by surface analysis is carried out on Ca by using
masters containing CaO, it is possible to obtain a calibration
curve concerning CaO. FIG. 5 shows the calibration curve concerning
Al.sub.2O.sub.3, which shows that the particle size of
Al.sub.2O.sub.3 is larger as the emission spectrum intensity of Al
is higher.
[0094] It should be noted that the particle sizes of intermetallic
inclusions determined by the EPMA method and the emission spectrum
intensity of metal elements existing in the same intermetallic
inclusions can be associated with each other not only by the above
method using correspondence between the size-decreasing order and
the intensity-decreasing order, but also by a method using position
coordinates of intermetallic inclusions within the .phi.5 mm area.
The FIG. 5 calibration curve A can be formed by either of these
methods.
[0095] Further, intermetallic inclusions contained in a test sample
are not limited to Al.sub.2O.sub.3, but calibration curves
concerning CaO, MgO, SiO, CaS, TiN, MnS, and so forth can also be
formed similarly to the FIG. 5 calibration curve. Therefore, it is
preferable to store the calibration curves thus formed as well in
the memory of the data processing section 106.
[0096] According to the FIG. 3 process, since an area of .phi.5 mm
at an arbitrary location on the surface of a master is scanned by
the EPMA (step S302), it is possible to determine particle sizes of
intermetallic inclusions contained in emission spots having a
diameter of 30 .mu.m within the .phi.5 mm area of the master
containing the intermetallic inclusions having particle sizes of 4
to 18 .mu.m, and based on the determined particle sizes of the
intermetallic inclusions, the calibration curve A representative of
the relationship between the particle size of the intermetallic
inclusions and the emission spectrum intensity of an element
constituting the intermetallic inclusions is formed (step S308), so
that data of particle sizes in a range of 4 to 18 .mu.m (i.e. a
target particle size range of the test sample, described
hereinafter) or in its vicinity indicated by the generated
calibration curve A can be made accurate.
[0097] Consequently, when particle sizes of intermetallic
inclusions whose particle sizes are within a range of 4 to 18
.mu.m, which is substantially the same as the range of those in a
test sample, are determined based on such a calibration curve A as
shown in FIG. 5, it is possible to determine the particle sizes of
the intermetallic inclusions and a particle size distribution
thereof more accurately than in the conventional case where
particle sizes of Al.sub.2O.sub.3 inclusions are determined based
on the relationship between the particle size and the emission
spectrum intensity thereof obtained by extrapolation based on a
calibration curve determined based on a trace concentration of Al
solid-solved in steel.
[0098] FIG. 6 is a flowchart of the particle size
distribution-generating process which is executed in the step S202
in FIG. 2.
[0099] The present process is executed by the emission spectrometer
100 whenever a particle distribution of intermetallic inclusions in
a test sample is repeatedly generated after the FIG. 3 process by
the emission spectrometer 100 is executed at least once.
[0100] In FIG. 6, first, a cylindrical test sample of .phi.40 mm
cut out from a steel material of SUJ2 is held in the light emitting
stand 102 (step S601), and then spark discharge is generated e.g.
one thousand times at a measurement area (.phi.5 mm) on the surface
of the test sample by the counter electrode of the light-emitting
section 101 (step S602). The test sample subjected to spark
discharge emits light of emission spectra.
[0101] Then, the light of emission spectra emitted from the test
sample is separated into emission spectra specific to respective
elements by the concave diffraction grating 112, and the separated
emission spectra enter respective ones of the photomultipliers 113
via the corresponding exit slits 110 (step S603).
[0102] The photomultipliers 113 each detect the incoming emission
spectrum and convert the intensity of the detected emission
spectrum into an electric current value and transmit the current
value to the photometric section 104. The photometric section 104
converts the received current value to a digital value, and then
transmits the digital value to the data processing section 106 via
the interface 105 (step S604). On the other hand, the light
emitting stand 102 transmits data of the location of each emission
spot within the measurement area on the surface of the test sample
and the number of times of generation of spark discharge to the
data processing section 106 via the interface 105.
[0103] Thus, the data of the respective emission spectrum
intensities of elements existing in emission spots, the locations
of the emission spots, and the number of times of generation of
spark discharge are transmitted to the data processing section 106,
and the data processing section 106 stores the data in its
memory.
[0104] Then, the data processing section 106 arranges the data of
the respective emission spectrum intensities of the elements in a
time sequence order to generate diagrams as shown in FIGS. 7A to
7E, described hereinbelow, each illustrating a distribution of the
data of the emission spectrum intensities. Further, the data
processing section 106 compares data of the respective intensities
of the emission spectra of the elements emitted from the same
emission spot, to thereby determine whether or not there exist
intermetallic inclusions within the emission spot, and when there
exist intermetallic inclusions, the data processing section 106
identifies the intermetallic inclusions (step S605).
[0105] FIGS. 7A to 7E are diagrams showing data of the respective
time-sequential emission spectrum intensity distributions of Fe, O,
Al, Ca and C, which are compared in the step S605 in FIG. 6.
[0106] In FIGS. 7A to 7E, a broken line in each of the diagrams
related, respectively, to O, Al, Ca and C indicates a threshold
value for use in determining whether or not the corresponding
element is solid-solved in a material (matrix). When an emission
spectrum intensity is smaller than the corresponding threshold
value, it can be considered that an element which emitted the
emission spectrum does not form an intermetallic inclusion, but
forms a background representing the matrix.
[0107] For example, when the data of the emission spectrum
intensities of O and Al in the same timing (i.e. in the same
emission spot) are larger than the respective threshold values, it
means that Al.sub.2O.sub.3 exists as an intermetallic inclusion in
the emission spot, and when the data of the emission spectrum
intensities of O and Ca in the same emission spot are larger than
the respective threshold values, it means that CaO exists as an
intermetallic inclusion in the emission spot. Further, when the
data of the emission spectrum intensities of O, Al and Ca in the
same emission spot are larger than the respective threshold values,
it means that Al.sub.2O.sub.3 and CaO exist as intermetallic
inclusions in the emission spot.
[0108] Referring again to FIG. 6, the data processing section 106
executes a data sorting process described hereinafter with
reference to FIGS. 8 to 10, to rearrange the data of the emission
spectrum intensities of an element specific to each of the
intermetallic inclusions identified in the step S605 in
intensity-increasing order (step S606). In executing the
rearrangement of the data in the step S606, the data processing
section 106 deletes data of emission spectrum intensities whose
values are smaller than the corresponding threshold value.
[0109] Then, the emission spectrum intensities of Al are
substituted into the data of the rearranged emission spectrum
intensities and the calibration curve A representative of the
relationship between the Al.sub.2O.sub.3 particle size and the
emission spectrum intensity of Al, which was formed by the FIG. 3
process, whereby the Al.sub.2O.sub.3 particle sizes are calculated
(step S607), and based on the calculated Al.sub.2O.sub.3 particle
sizes and the number of the data, a particle distribution of the
intermetallic inclusions is generated. The generated data of the
particle size distribution is displayed on the CRT or the printer.
According to the FIG. 6 process, intermetallic inclusions existing
in an emission spot on the surface of a test sample is identified
based on the data of the respective emission spectrum intensities
of elements existing in the emission spot (step S605), and then the
particle sizes of the identified intermetallic inclusions are
calculated, based on the data of the emission spectrum intensities
and the calibration curve A formed by the FIG. 3 process (step
S607). This makes it possible to perform quick and accurate
determination of the particle sizes and particle size distribution
of the intermetallic inclusions.
[0110] FIGS. 8 to 10 are a flowchart of the data sorting process
which is executed in the step S606 in FIG. 6.
[0111] In the data sorting process in FIGS. 8 and 9, the data
processing section 106 rearranges data I.sub.x(i) of a row I.sub.x
of emission spectrum intensities specific to a constituent element
X as one of the constituent elements of the intermetallic inclusion
identified in the step S605 e.g. in intensity-increasing order,
into a row AL.sub.x while deleting data items I.sub.x(i) whose
values are smaller than the threshold value for the constituent
element X.
[0112] A description will be given of the data sorting process in
FIGS. 8 to 10.
[0113] In FIG. 8, first, a count i indicative of the number of data
items in the row I.sub.x, which were read from the memory, is set
to 1, and a count ii indicative of the number of data items of the
row I.sub.x whose values are smaller than the threshold value is
set to 0 (step S801), and thereafter one data item is fetched at
random as a data item I.sub.x(i) from the row I.sub.x of data items
stored in the memory corresponding in number to the number of times
J (1000) of generation of spark discharge, and it is determined
whether or not the value of the fetched data item I.sub.x(i) is
equal to or larger than the threshold value for the constituent
element X (step S802).
[0114] If the value of the fetched data item I.sub.x(i) is equal to
or larger than the threshold value for the constituent element X in
the step S802, a count K indicative of the number of data items
I.sub.x(i) whose values are determined to be equal to or larger
than the threshold value for the constituent element X is
calculated by using the following equation (2) (step S803):
K=i-ii (2)
[0115] The fetched data item I.sub.x(i) is substituted for a data
item A.sub.x(K) in a row A.sub.x as a set of data items I.sub.x(i)
which are equal to or larger than the threshold value for the
constituent element X (step S804). Further, the count K is regarded
as the maximum value of the current count i at the present time and
substituted for K.sub.max (step S805).
[0116] If the fetched data item I.sub.x(i) is determined to be
smaller than the threshold value for the constituent element X in
the step S802, the count ii is incremented by 1 (step S806),
followed by the process proceeding to a step S807.
[0117] Then, it is determined whether or not the present count i is
smaller than the number of times J (1000 times) of generation of
spark discharge (step S807).
[0118] If the count i is determined to be smaller than the number
of times J of generation of spark discharge in the step S807, the
present count i is incremented by 1 (step S808), followed by the
process returning to the step S802, whereas if the present count i
is determined to be equal to or larger than the number of times J
of generation of spark discharge, the process proceeds to a step
S901 (FIG. 9).
[0119] In FIG. 9, arithmetic operations are carried out for
rearranging the set of data items I.sub.x(i) of the row data
AL.sub.x(K) obtained in FIG. 8, which are equal to or larger than
the threshold value for the constituent element X in
intensity-increasing order.
[0120] First, an index l is set to 1 (step S901), and the count K
is set to 1 (step S902), whereby an initial minimum value in the
row A.sub.x in the case of K=1 is calculated by using the following
equation (3) (step S903):
.DELTA.A.sub.x(K)=A.sub.x(K)-A.sub.x(K+1) (3)
[0121] To determine which row data A.sub.x is the smaller on the
right side of the equation (3), it is determined whether or not
.DELTA.A.sub.x(K) is equal to or smaller than 0 (step S904).
[0122] If step 9, A.sub.x(K).ltoreq.A.sub.x(K+1) holds, it is
determined whether or not K is larger than 1 (step S905). If it is
determined in the step S905 that K=1 holds (during an initial
operation), the data item A.sub.x(K) in the row A.sub.x is
substituted for a variable B.sub.x(l) (step S906), and the variable
B.sub.x(l) is substituted for a minimum value in a row data
AL.sub.x(l) in which data items I.sub.x(i) are rearranged in
value-increasing order with respect to the value l (step S907).
Then, an initial value of a provisional minimum value in the row
Al.sub.X is set by setting AL.sub.x(l)=B.sub.x(l), and K is set by
setting KK=K (step S908). More specifically,
AL.sub.x(l)=B.sub.x(l)=A.sub- .x(K), and KK=K=1 are set. Then, the
process proceeds to a step S912.
[0123] Further, if .DELTA.A.sub.x(K) is determined to be larger
than 0 in the step S904, the data item A.sub.x(K+1) in the row
A.sub.x is substituted for the variable B.sub.x(l) (i.e. the value
of the variable B.sub.x(l) is updated) (step S909), and the
variable B.sub.x(l) is substituted for the minimum value in the row
data AL.sub.x(l) in which data items I.sub.x(i) are rearranged in
value-increasing order with respect to 1 (step S910). Then, e.g.
when K=1 holds, the initial provisional minimum value AL.sub.x(1)
is set by setting AL.sub.x(1)=B.sub.x(1)=A.sub.x(2), and KK=K+1 is
set, e.g. KK=K+1=2 is set (step S911). Then, the process proceeds
to the step S912.
[0124] The value KK in the steps S908 and S911 is a count for
replacing the minimum value B.sub.x(l) (=A.sub.x(KK)) selected from
the row A.sub.x by a value of .infin. for the next value of the
index l, to prevent the original A.sub.x(K) value from being
selected again, while allowing an arithmetic operation to be
carried out in a step S913, referred to hereinafter.
[0125] After completion of these arithmetic operations, it is
determined in a step S912 whether or not the count K is smaller
than K.sub.max.
[0126] If the count K is determined to be smaller than K.sub.max in
the step S912, the count K is incremented by 1 (K=K+1) (step S913),
and then it is determined whether or not a data item A.sub.x(K)
newly fetched from the row A.sub.x is .infin. (step S914). If the
data item A.sub.x(K) is determined to be .infin. in the step S914,
the process returns to the step S904, whereas if the data item
A.sub.x(K) is not determined to be .infin., the process proceeds to
a step S915, wherein a minimum value in the row A.sub.x at the
present value of the count K is calculated by using the following
equation (4):
.DELTA.A.sub.x(K)=AL.sub.x(l)-A.sub.x(K+1) (4)
[0127] This operation is carried out in order to compare the value
of the data item A.sub.x(K+1) with the minimum value AL.sub.x(l)
which has been provisionally selected from the row A.sub.x.
[0128] Then, the process returns to the step S904, wherein a
determination as to the value of .DELTA.A.sub.x(K) is carried out
again. If .DELTA.A.sub.x(K) is determined to be equal to or smaller
than 0 in the step S904, and K is determined to be larger than 1 in
the step S905, the process proceeds to a step S916, wherein
AL.sub.x(l)=B.sub.x(l) is set so as to maintain the provisional
minimum value obtained in the preceding operation.
[0129] If the value of .DELTA.A.sub.x(K) is not equal to or smaller
than 0 in the step S904, the process proceeds to the steps S909 et
seq., wherein the count KK for causing the minimum value B.sub.x(l)
(=A.sub.x(KK)) selected from the row A.sub.x to be replaced by
.infin. for the next value of the index l is updated to K+1. On the
other hand, if K is equal to or smaller than 1, the process
proceeds to the step S906, wherein the count KK to be replaced by
.infin. is held at K.
[0130] An arithmetic operation of the index l is completed when it
is determined in the step S912 that the count K is equal to or
larger than K.sub.max, and hence the process proceeds to a step
S917, wherein the data item A.sub.x(KK) selected from the row
A.sub.x is finally set to .infin. (A.sub.x(KK)=.infin.). As a
result, this value cannot be repeatedly fetched again for the next
arithmetic operation for the index l. The index l is incremented by
1 in a step S918, followed by the process proceeding to a step
S919.
[0131] In the step S919, it is determined whether or not the
incremented index l is smaller than K.sub.max. This step is
executed in order to determine whether or not the arithmetic
operations for all values of the index l have been completed.
[0132] If the incremented index l is determined to be smaller than
K.sub.max in the step S919, the steps S902 to S919 are repeatedly
executed with the incremented index l.
[0133] If the incremented index l is determined to be equal to or
larger than K.sub.max in the step S919, i.e. if arithmetic
operations have been completed for all the values of the index l,
the process proceeds to a step S1001 (FIG. 10).
[0134] In the steps S1001 et seq. in FIG. 10, arithmetic operations
are carried out for determining a frequency C.sub.x(l) indicative
of a number (m) of data items AL.sub.x(l) having the same value in
the row AL.sub.x of data items AL.sub.x(l) which are all equal to
or larger than the threshold value for the constituent element X,
i.e. for determining the number (m) of intermetallic inclusions
exist for each particle size [.mu.m].
[0135] First, in the step S1001, the index l is incremented by 1,
and then 1 is substituted for an arbitrary value n in the index l
(step S1002 ). Further, the count m of a counter which calculates
the number of intermetallic inclusions which have the same particle
size as that of AL.sub.x(l) existing in K.sub.max is set to 1 (step
S1003) Then, .DELTA.AL.sub.x(l) representative of the difference
between the value of the data AL.sub.x(l) for the index l in the
row AL.sub.x and the value of the data item AL.sub.x(n) with the
arbitrary value n substituted in the index l is calculated by using
the following equation (5) (step S1004):
.DELTA.AL.sub.x(l)=AL.sub.x(l)-AL.sub.x(n) (5)
[0136] Then, it is determined whether or not the calculated
.DELTA.AL.sub.x(l) is equal to 0 (step S1005).
[0137] If .DELTA.AL.sub.x(l) is not determined to be equal to 0 in
the step S1005, the process proceeds to a step S1006. In the step
S1006, the count m representative of the number of the data items
AL.sub.x(n) having the same value is held at m, and the process
proceeds to a step S1010.
[0138] If .DELTA.AL.sub.x(l) is determined to be equal to 0 in the
step S1005, it is determined whether or not the arbitrary value n
is equal to 1 (step S1007).
[0139] If the arbitrary value n is determined to be equal to 1 (the
index l is 1, and the calculated difference .DELTA.AL.sub.x(l) is
0) in the step S1007, the data count m is set to 1 (step S1008 ),
whereas if the arbitrary value n is not determined to be equal to
1, the data count m is incremented by 1 (step S1009).
[0140] In the following step S1010, the arbitrary value n is
incremented by 1, and then it is determined whether or not the
arbitrary value n is smaller than the maximum value K.sub.max of
the index l (step S1011).
[0141] If the arbitrary value n is determined to be smaller than
the maximum value K.sub.max of the index l in the step S1011, the
process returns to the step S1004, wherein the steps S1004 et seq.
are repeatedly executed until the arbitrary value n has covered all
the values of the index l. On the other hand, if the arbitrary
value n is equal to or larger than the maximum value K.sub.max of
the index l, it means that the arbitrary values n has covered all
the values of the index l, and hence the data count m at this time
is set to the number C.sub.x(1) of the data items AL.sub.x(n) (step
S1012).
[0142] Then, the index l is incremented by 1 (step S1013), and this
value of the index l is regarded as the present maximum value
l.sub.max of the index l, and it is determined whether or not the
present maximum value l.sub.max is smaller than K.sub.max (step
S1014). If the present maximum value l.sub.max is smaller than
K.sub.max, the process returns to the step S1002, whereas if the
present maximum value l.sub.max is equal to or larger than
K.sub.max, the present process is terminated.
[0143] According to the FIG. 10 process, if the data items
AL.sub.x(l), AL.sub.x(i) having the same value, which were fetched
from the row AL.sub.x of the data items AL.sub.x(l) each having a
value equal to or larger than the threshold value for the
constituent element X, are each converted from the emission
spectrum intensity of the constituent element X (e.g. Al) to a
particle size of the intermetallic inclusion by using FIG. 5,
described hereinbefore, or FIG. 21, described hereinafter (step
S607), this means that the frequency C.sub.x(l) indicative of the
number (m) of intermetallic inclusions existing for each particle
size [.mu.m] is obtained. Therefore, it is possible to display or
output a diagram shown in FIG. 26A, described hereinafter, based on
the particle sizes [.mu.m] and the row data C.sub.x(l)
representative of frequencies, in the same manner as a diagram
shown in FIG. 26B, which is obtained by the EPMA.
[0144] Next, a variation of the particle size-determining and
particle size distribution-generating method according to the first
embodiment of the invention will be described in detail with
reference to the drawings.
[0145] The variation of the particle size-determining and particle
size distribution-generating method according to the first
embodiment is distinguished from the particle size-determining and
particle size distribution-generating method of the first
embodiment in that by utilizing the fact that in general, in an
emission spot (corresponding to timing T.sub.i in each of FIGS. 7A
to 7E) where the intensity of an emission spectrum emitted e.g. by
Fe as an element forming the ground of a test sample is equal to or
smaller than the threshold value, there exist intermetallic
inclusions other than Fe, the data sorting process of FIGS. 8 to 10
is executed with Fe as a trigger concerning the timing T.sub.i.
[0146] In the following, points which distinguish the particle
size-determining and particle size distribution-generating method
according to the present variation of the method according to the
first embodiment will be described with reference to the
drawings.
[0147] Referring first to FIG. 4, an emission spot on the surface
of a test sample has a circular shape of .phi.30 .mu.m. When no
intermetallic inclusion exists in the surface of a measurement area
of the test sample, an Fe emission spectrum, for example, emitted
from Fe as a metal element which forms the ground of the test
sample and has conductivity is obtained. When there exists an
intermetallic inclusion in the surface of the measurement area of
the test sample, an element X as a constituent element of the
intermetallic inclusion emits light, which makes the intensity of
the Fe emission spectrum lower than that in the case of no
intermetallic inclusion existing in the surface of the measurement
area of the test sample.
[0148] Further, referring to FIGS. 7A to 7E, when no intermetallic
inclusion exists in the surface of the measurement area of the test
sample, the emission spectrum intensity of Fe forming the ground of
the test sample assumes a larger value than the corresponding
threshold value. On the other hand, when there exists intermetallic
inclusions in the surface of the measurement area of the test
sample, for the reason described above, the emission spectrum
intensity of Fe becomes lower than the threshold value, while the
emission spectrum intensity of the element X as the constituent
element of the intermetallic inclusions assumes a larger value than
the corresponding threshold value.
[0149] In FIGS. 7A to 7E, emission spots which are identical in the
number of times of generation of spark discharge generated thereat
are indicated as timing T.sub.i by broken lines.
[0150] For example, in timing T.sub.1 indicated by broken lines, it
is estimated that there exists an intermetallic inclusion of
Al.sub.2O.sub.3 which is a compound composed of Al and O, except
the case where there exist elements other than an element or
elements to be determined and the lens is deteriorated, referred to
hereinafter. Similarly, in timing T.sub.2 indicated by broken
lines, it is estimated that there exists intermetallic inclusions
of Al.sub.2O.sub.3 and CaO each of which is a compound composed of
more than one element selected from Al, O and Ca. Further,
similarly, in timing T.sub.5 indicated by broken lines, where only
the emission spectrum intensity of C is equal to or larger than the
corresponding threshold value, it is estimated that there exists an
intermetallic inclusion composed of a carbide which does not
include Fe, O, Al and/or Ca as constituent elements.
[0151] FIG. 11 is a flowchart of a data sorting process which is
executed by the variation of the particle size-determining and
particle size distribution-generating method according to the first
embodiment.
[0152] The FIG. 11 data sorting process is distinguished from the
FIG. 8 data sorting process in that a row A.sub.x is generated by
deleting data of emission spots where the emission spectrum
intensities of Fe are smaller than the threshold value specific to
Fe (hereinafter referred to as "the threshold value Fe") from each
row I.sub.x of data items of emission spectrum intensities specific
to each of elements X as constituent elements of the intermetallic
inclusions.
[0153] A description will be given of points distinguishing the
FIG. 11 data sorting process from the FIG. 8 data sorting process
executed by the particle size-determining and particle size
distribution-generating method according to the first
embodiment.
[0154] As shown in FIG. 11, first, a count i indicative of the
number of data items in a row I.sub.Fe in which are arranged data
of the emission spectrum intensities of Fe, fetched from the
memory, is set to 1, and a count ii indicative of the number of
data items in the row I.sub.Fe whose values are larger than the
threshold value Fe is set to 0 (step S1101). Thereafter, one data
item is fetched at random as a data item I.sub.Fe(i) from the rows
I.sub.Fe stored in the memory in number corresponding to the number
of times J (1000) of generation of spark discharge, and it is
determined whether or not the fetched data item I.sub.Fe(i) is
equal to or smaller than the threshold value Fe (step S1102). If
the fetched data item I.sub.Fe(i) is determined to be larger than
the threshold value Fe in the step S1102, the count ii is
incremented by 1 (step S1103), followed by the process proceeding
to a step S1110.
[0155] If the fetched data item I.sub.Fe(i) is determined to be
equal to or smaller than the threshold value Fe in the step S1102,
a count K indicative of the number of data items I.sub.Fe(i) whose
values were determined to be equal to or smaller than the threshold
value Fe is calculated by using the following equation (6) (step
S1104):
K=i-ii (6)
[0156] Then, in a step S1105, one of elements (e.g. O, Ca, C, Ti,
Mn, S and N) existing in the surface of measurement area of the
test sample is selected as a constituent element X, and then data
items I.sub.x(i) of the emission spectrum intensities of the
constituent element X corresponding to emission spots of the
fetched data items I.sub.Fe(i) are read out from a row I.sub.x of
data of the emission spectrum intensities specific to the
constituent element X, which are stored in the memory (step
S1106).
[0157] Then, the fetched data items I.sub.x(i) are substituted for
data items A.sub.x(K) in the row A.sub.x (step S1107), and it is
determined whether or not all the constituent elements existing in
the surface of the measurement area have been selected. If not all
the constituent elements have been selected in the step S1108, the
process returns to the step S1105, whereas if all the constituent
elements have been selected, the count K is regarded as a present
maximum value of the count i at the time point that the data item
I.sub.Fe(i) was read out at random, and substituted for K.sub.max
(step S1109).
[0158] Then, it is determined whether or not the present count i is
smaller than the number of times J (1000) of generation of spark
discharge (step S1110).
[0159] If the count i is smaller than the number of times J of
generation of spark discharge, the count i is incremented by 1
(step S1111), followed by the process returning to the step S1102,
whereas if the count i is equal to or larger than the number of
times J of generation of spark discharge, a constituent element X
which is one of the elements constituting the intermetallic
inclusion identified in the step S605 is selected, followed by the
process proceeding to the step S901 (FIG. 9).
[0160] It should be noted that when the count i is determined to be
equal to or larger than the number of times J of generation of
spark discharge in the step S1110, if the data row data A.sub.x(K)
of the constituent element X have to be subjected to the
threshold-comparison process executed in the step S802 in FIG. 8 of
the first embodiment, the process may proceed to the step S801 in
FIG. 8 and be subjected to the processing in FIG. 8, and then
proceed to the step S901 (FIG. 9).
[0161] However, the gist of the present variation of the particle
size-determining and particle size distribution-generating method
according to the first embodiment is as follows.
[0162] As the threshold value for data items I.sub.Fe(i) is set to
a lower value in the step S1102 in FIG. 11, the values of the data
row data A.sub.x(K) which are equal to or larger than the threshold
value in the step S1107 become larger than the values of the data
items I.sub.x(i) and sufficiently exceed the threshold value in the
step S802 in FIG. 8 (fully satisfy the condition of
I.sub.x(i).gtoreq.threshold value in the step S802 in FIG. 8). In
other words, so long as the threshold value for data items
I.sub.Fe(i) in the step S1102 in FIG. 11 is properly set, the need
for carrying out the threshold-comparison process executed in the
step S802 in FIG. 8 can be substantially eliminated. As a result,
the process can directly proceed to the step S901 (FIG. 9) without
passing through the FIG. 8 process, so that it is possible to
shorten the processing time required for generation of a particle
size distribution and so forth.
[0163] According to the FIG. 11 process, the data items I.sub.x(i)
of emission spectrum intensities corresponding to the respective
emission spots of the data items I.sub.Fe(i) whose values are equal
to or smaller than the threshold value Fe are taken out from each
of the rows I.sub.x (X=O, Ca, C, Ti, Mn, S, N, and so forth) of the
emission spectrum intensities of all the elements existing in the
measurement area on the surface of a test sample, which are stored
in the memory, before execution of the data sorting process in
FIGS. 9 and 10, which makes it possible to reduce the number of
data items to be used in subsequent processing.
[0164] In particular, when the particle sizes and particle size
distributions (frequencies) of a plurality of intermetallic
inclusions are to be determined, by executing the FIG. 11 process
once, it is possible to obtain rows A.sub.x of a reduced number of
data items of emission spectrum intensities of all the elements
existing in the measurement area. Therefore, it is possible to
eliminate the need for repeatedly carrying out the process in FIGS.
8 to 10 for executing the rearrangement in the step S607 in FIG. 6,
thereby enabling quicker and more accurate determination of the
particle sizes of the intermetallic inclusions and the particle
size distribution of the intermetallic inclusions.
[0165] In the present process, when the data items I.sub.x(i) of
the intensities of the emission spectra of an element X as a
constituent element of an intermetallic inclusion include no data
items A.sub.x(K) whose values are equal to or larger than the
threshold value, it can be considered that there exist elements
other than the element to be determined (e.g. a constituent element
of a carbide, other than carbon) or the lens is stained or
deteriorated.
[0166] A correction process related to the stain/deterioration of
the lens will be described in detail as part of a third embodiment,
given hereinafter. Needless to say, it is preferable that the
correction process according to the third embodiment is executed
together with the variation of the particle size-determining and
particle size distribution-generating method according to the first
embodiment.
[0167] Next, a particle size-determining and particle size
distribution-generating method according to a second embodiment of
the invention will be described in detail with reference to
drawings.
[0168] A bearing steel actually used as a material for rolling
members, such as a roller bearing, contains various kinds of
intermetallic inclusions formed e.g. of Al.sub.2O.sub.3, MgO, MnS,
CaO, and SiO.sub.2. Among these intermetallic inclusions, the
Al.sub.2O.sub.3 inclusion, which is an oxide-based inclusion, most
seriously affects the rolling life of the bearing steel. The
particle sizes and particle size distribution of the
Al.sub.2O.sub.3 inclusion, or the number of Al.sub.2O.sub.3
particles existing per unit area or volume, i.e. abundance thereof,
are so closely related to the rolling life or the like of the
bearing steel that so-called persons skilled in the art are very
much interested in the particle sizes and particle size
distribution and/or abundance of the Al.sub.2O.sub.3 inclusion
(though the relationship between those and the rolling life of the
bearing steel may be determined by another method).
[0169] The method of determining the particle sizes and particle
size distribution or abundance of the Al.sub.2O.sub.3 inclusion
includes two kinds of method, one of which is a three-dimensional
method in which intermetallic inclusions are extracted from a
sample of the bearing steel and the determination is carried out on
the extracted intermetallic inclusions in a three-dimensional
manner, such as an electron-beam elution method, and the other is a
two-dimensional method in which the surface of a sample of the
bearing steel is polished and the surface is subjected to the
determination by a combination of an optical microscope and an
image analyzer. However, the former method requires a large-scale
apparatus for extraction of the Al.sub.2O.sub.3 inclusion, while
the latter method is simple, but it is not capable of obtaining
real particle sizes of the Al.sub.2O.sub.3 inclusion.
[0170] The particle size-determining and particle size
distribution-generating method according to the second embodiment
is also implemented by the FIG. 1 emission spectrometer 100 to
determine the particle sizes and particle size distribution of
intermetallic inclusions contained in a test sample cut out from a
steel material.
[0171] As is distinct from the conventional EPMA method and a like
method using a special master for determining the concentration of
a trace amount of Al, the present method uses a real steel master
cut out from a real steel material. The present method makes it a
precondition that a calibration curve C, described hereinbelow,
representative of the relationship between the concentration of Al
and the emission spectrum intensity of Al is generated by using the
FIG. 1 emission spectrometer 100.
[0172] It should be noted that inclusions contained in the bearing
steel are not only the Al.sub.2O.sub.3 inclusion as described
above, but since the Al.sub.2O.sub.3 inclusion is most closely
related to the rolling life of the bearing steel, the following
description will be given by taking the Al.sub.2O.sub.3 inclusion
as an example. It goes without saying that other kinds of
intermetallic inclusions can be dealt with similarly to the
Al.sub.2O.sub.3 inclusion.
[0173] The particle size-determining and particle size
distribution-generating method of the second embodiment is
distinguished from that of the first embodiment in which the
particle size of Al.sub.2O.sub.3 actually existing in the steel is
determined by surface analysis by the EPMA method, in that the
emission spectrometer 100 is used to determine the real particle
size of the Al.sub.2O.sub.3 inclusion.
[0174] Further, the use of the calibration curve C representative
of the relationship between the concentration of Al and the
emission spectrum intensity of Al is effective in that it is
possible to determine the particle sizes and particle size
distribution of Al.sub.2O.sub.3 particles actually existing in a
steel based on Al concentration (volume %) at least in a range of
the order of 500 ppm to the order of percent.
[0175] A description will be given of a particle size-determining
and particle size distribution-generating process executed by the
FIG. 1 emission spectrometer 100 to implement the particle
size-determining and particle size distribution-generating method
of the second embodiment, with reference to the drawings.
[0176] FIG. 12 is a flowchart of the particle size-determining and
particle size distribution-generating process executed according to
the particle size-determining and particle size
distribution-generating method of the second embodiment.
[0177] In FIG. 12, first, a calibration curves B, C generating
process (step S1201), described hereinafter with reference to FIG.
13, and then a calibration curve D-forming process (step S1202),
described hereinafter with reference to FIG. 16, a calibration
curve E-generating process (step S1203), described hereinafter with
reference to FIG. 19, and a particle size distribution-generating
process (step S1204), described hereinafter with reference to FIG.
20, are executed, followed by terminating the process.
[0178] Next, the particle size-determining and particle size
distribution-generating method of the second embodiment will be
described in detail with reference to the drawings.
[0179] In the particle size-determining and particle size
distribution-generating method according to the second embodiment,
an EPMA is not used, but the real particle sizes of intermetallic
inclusions contained in a reference sample equivalent to a test
sample is determined by using the emission spectrometer 100, and a
particle size distribution is generated based on the determined
real particle sizes of the intermetallic inclusions.
[0180] In the following, the intermetallic inclusion particle
size-determining process and the particle size
distribution-generating process executed by the FIG. 1 emission
spectrometer 100 will be described with reference to the
drawings.
[0181] FIG. 13 is a flowchart of the calibration curves B, C
generating process which is executed in the step S1201 in FIG. 12
for forming the calibration curve B representative of the
relationship between the emission spectrum intensity of Fe and the
concentration of Fe, and then forming the calibration curve C
representative of the relationship between the emission spectrum
intensity Al and the concentration of Al by the use of the
calibration curve B.
[0182] The present calibration curve-forming process is carried out
by the emission spectrometer 100 at least once before the method of
determining the particle sizes of intermetallic inclusions and
generating a particle size distribution is repeatedly executed on a
test sample by the emission spectrometer 100. Seventeen types of Fe
concentration masters (examples 1 to 17 shown in Table 1) are
prepared whose Fe concentrations are already quantitatively
determined e.g. by chemical analysis, such as an atomic absorption
analysis method, and thus already known concentration values, and
different from each other. These masters may be formed of an alloy
steel, such as M50, 5Cr, SUH330, SUH310, or M50NiL. Alternatively,
commercial masters sold by an external testing organization may be
employed.
1TABLE 1 Fe Concentration Example [Mass %] Emission Spectrum 1
46.13 7760 2 51.27 8802 3 59.63 9846 4 62.70 10098 5 65.57 10782 6
70.02 11634 7 77.69 12633 8 82.12 13570 9 85.04 13957 10 89.36
14769 11 93.28 15798 12 94.32 15854 13 95.34 15823 14 96.73 16033
15 97.39 16025 16 99.04 16246 17 99.59 16202
[0183] After each of these Fe concentration masters is held in the
light emitting stand 102 of the emission spectrometer 100 of the
present invention (step S1301), the counter electrode of the
light-emitting section 101 generates spark discharge e.g. ten
times. The Fe concentration masters subjected to spark discharge
emit emission spectra (on a master-by-master basis) (step
S1302).
[0184] Thereafter, the light of emission spectra emitted by each
master is separated by the concave diffraction grating 112 into
emission spectra specific to Fe as the ground of the Fe
concentration master (step S1303), and the split Fe emission
spectra are caused to enter the respective corresponding
photomultipliers 113 via the exit slits 110.
[0185] Each photomultiplier 113 detects the incoming Fe emission
spectrum and converts the intensity of the detected Fe emission
spectrum to an electric current value and transmits the current
value to the photometric section 104. The photometric section 104
converts the received current value to a digital value and then
transmits the digital value obtained by the conversion to the data
processing section 106 via the interface 105 (step S1304). On the
other hand, the light emitting stand 102 transmits data of the
positions of emission spots of .phi.30 .mu.m in an arbitrary
measurement area on the surface of the Fe concentration master and
the number of times of generation of spark discharge to the data
processing section 106 via the interface 105.
[0186] Thus, data of the intensities of the emission spectra of Fe
existing in the emission spots, the positions of the emission
spots, and the number of times of generation of spark discharge are
transmitted to the data processing section 106, and stored in the
memory of the same.
[0187] Since the Fe concentration masters have already known Fe
concentration values, these known concentration values are input to
the data processing section 106 as data of Fe concentration. The
data processing section 106 forms the calibration curve B (FIG. 14)
representative of the relationship between the concentration of Fe
and the emission spectrum intensity of Fe, based on the input data
of Fe concentration [mass %] and the stored data of the emission
spectrum intensity of Fe (step S1305).
[0188] The number of times of generation of spark discharge caused
per Fe concentration master in the step S1302 is set to 10 times by
way of example because it is preferable that the emission spectrum
intensity is determined as an average value of emission spectrum
intensities obtained ten times in this step. This makes it possible
to make the average value of the emission spectrum intensities
correspond to the Fe concentration of the one Fe concentration
master.
[0189] Then, steps S1306 to S1313 in FIG. 13 are executed to form
the calibration curve C representative of the relationship between
the emission spectrum intensity of Al and the concentration of
Al.
[0190] First, cylindrical real steel masters of .phi.40 mm are cut
out from a steel material for actual use, e.g. SUJ-2 in the form of
a solid round rod, as shown in FIG. 15, and then held in the light
emitting stand 102 (step S1306).
[0191] In the following, description will be given of properties of
the steel material for actual use.
[0192] FIG. 15 is a cross-sectional view of a steel material, taken
along a section orthogonal to the axis of the steel material for
actual use, from which the real steel masters are cut out in the
step S1306 in the FIG. 13.
[0193] In FIG. 15, the steel material 700 for actual use is
produced by a method of blooming an ingot or a continuous method.
When a molten material is cooled and solidified into the steel
material 700 during the process of producing the same, in the core
portion of the steel material 700, where the cooling rate is
smaller than in the outer peripheral portion of the same, there
occurs a phenomenon that intermetallic inclusions 400 are
concentrated (center segregation). As shown in FIG. 15, the center
segregation is conspicuous in an area (center segregated portion
500) within a range of 0.5 D with respect to the diameter D of the
steel material 700, i.e. within a range of .+-.0.25 D from the
center of the steel material 700, and more conspicuous toward the
center even in this center segregated portion 500.
[0194] The center segregation is known to be correlated with the
distance from the core portion, and hence by cutting out a portion
of the steel material 700 including the core portion, along a plane
perpendicular to the axis of the steel material 700, it is possible
to obtain a real steel master containing Al.sub.2O.sub.3 inclusions
varying in size with the distance from the core portion. The
Al.sub.2O.sub.3 inclusions of various sizes contained in the real
steel master include ones having Al concentrations at least in a
range from the order of 500 ppm to the order of percent. Therefore,
it is preferable to obtain a real steel master containing
Al.sub.2O.sub.3 inclusions having various sizes by cutting out a
portion of the steel material 700 including the core portion, along
a plane perpendicular to the axis of the steel material 700, so as
to obtain a calibration curve in an Al concentration region ranging
from a low concentration to a high concentration thereof.
[0195] It should be noted that a plurality of real steel masters
500 containing Al.sub.2O.sub.3 inclusions of various sizes may be
obtained by cutting out from the steel material 700 a plurality of
pieces of the center segregated portion 500 in parallel with the
axis of the steel material 700. Further, the steel material 700 may
also contain intermetallic inclusions other than
Al.sub.2O.sub.3.
[0196] Referring again to FIG. 13, after the real steel master is
held (step S1306), the counter electrode of the light-emitting
section 101 generates spark discharge e.g. one thousand times at an
arbitrary location on a measurement area (.phi.5 mm) on the surface
of the real steel master such that the diameter of each spot is
held to .phi.30 .mu.m (it is important that once arbitrarily set,
the spot diameter should be held constant), the real steel master
subjected to spark discharge emits emission spectra (step S1307).
The intermetallic inclusions in the surface of the real steel
master are dielectric, and hence at this time, the spark discharge
is selectively guided to the intermetallic inclusions in the
surface of the real steel master by the dielectric property
thereof. Accordingly, the emission spectra generated by the real
steel master are selectively emitted from the intermetallic
inclusions. Therefore, when Al.sub.2O.sub.3 intermetallic
inclusions exist in the surface of the real steel master, emission
spectra containing information on Al and O as element information
on Al.sub.2O.sub.3 can be obtained.
[0197] It should be noted that a description will be given of the
following steps on the assumption that the intermetallic inclusions
are Al.sub.2O.sub.3, and hence only emission spectrum intensities
from respective emission spots each containing only Fe, Al and O
are selected, and emission spectral information from emission spots
containing Ca, Si, Mn, Mg, etc. is excluded later.
[0198] Thereafter, the emission spectra emitted from
Al.sub.2O.sub.3 as the intermetallic inclusions of the real steel
master are separated into emission spectra specific to the
respective elements Fe, Al and O by the concave diffraction grating
112 (step S1308), and the separated emission spectra of the
respective elements enter the respective photomultipliers 113 via
the corresponding exit slits 110.
[0199] The photomultipliers 113 detect the incoming emission
spectra of Fe, Al and O and convert the intensities of the detected
emission spectra of the respective elements to electric current
values and transmit the current values to the photometric section
104. The photometric section 104 converts each of the received
current values to a digital value, and then transmits the digital
value obtained by the conversion to the data processing section 106
via the interface 105 (step S1309). On the other hand, the light
emitting stand 102 transmits data of the positions of emission
spots of .phi.30 .mu.m on the measurement area of .phi.5 mm on the
surface of the real steel master or the distance from the center
portion and the number of times of generation of spark discharge to
the data processing section 106 via the interface 105.
[0200] Thus, data of the respective emission spectrum intensities
of the elements Fe, Al and O existing in the emission spots of
.phi.30 .mu.m, described above are transmitted to the data
processing section 106 whenever spark discharge is carried out, and
the data processing section 106 stores the received data in the
memory thereof.
[0201] It should be noted that in the case where the intermetallic
inclusions are Al.sub.2O.sub.3, even if information on elements
other than Fe, Al and O is obtained at each time of generation of
spark discharge, only the data on Fe, Al and O stored in the memory
of the data processing section 106 may be used(the other data is
excluded).
[0202] Then, by applying the intensities of the Fe emission spectra
emitted from the real steel master to the FIG. 14 calibration curve
B formed in the step S1305, Fe concentration data [mass %]
concerning the Fe concentrations [mass %] of the real steel master
is generated, and then the generated Fe concentration data is
stored (e.g. in a manner associated with spot positions in a
sequence of times of spark discharge) in the memory of the data
processing section 106 such that the stored data can be read out
for use when the calibration curve C representative of the
relationship between the Al concentration and the Al emission
spectrum intensity is formed in steps S1311 to S1312, referred to
hereinbelow (step S1310).
[0203] Then, Al concentration data [mass %] of Al within
Al.sub.2O.sub.3 as the intermetallic inclusions is calculated from
the Fe concentration data generated in the step S1310 (step S1311).
This arithmetic operation is carried out using the following
equation (7) stored in the data processing section 106:
Al concentration=(100-Fe concentration).times.54/102 (7)
[0204] wherein 54 represents the atomic weight
(.apprxeq.26.8.times.2) of Aluminum in Al.sub.2O.sub.3, 102
represents the formula weight (.apprxeq.28.8.times.2+16.0.times.3)
of Al.sub.2O.sub.3, and the Fe concentration represents a data item
of Fe concentration data generated in the step S1310 which was
obtained by the same spark discharge corresponding to one of
particles of Al.sub.2O.sub.3 which was generated at that time.
[0205] As is apparent from the right side of the equation (7),
simply by substituting one of the Fe concentration data items
generated in the step S1310 into the equation (7), it is possible
to calculate one of the data items of Al concentration in the
Al.sub.2O.sub.3 inclusions existing in an emission spot of .phi.30
.mu.m subjected to the same spark discharge.
[0206] For example, when Fe concentration data items generated
based on the calibration curve B concerning emission spots
corresponding to respective spark discharges are 80, 45, and 20
[mass %], respectively, the concentration data items of Al in the
Al.sub.2O.sub.3 inclusion existing in the respective emission spots
as 10.6, 34.5 and 42.4 [mass %], respectively.
[0207] It should be noted that although the above equation (7) is
for calculating Al concentration data in the case of the
intermetallic inclusions being Al.sub.2O.sub.3, when the
intermetallic inclusions are SiO.sub.2, CaO or MgO, the atomic
weight of a corresponding one of SiO.sub.2, CaO and MgO and the
formula weight of the oxide inclusions can be applied to the
equation (7) so as to calculate the corresponding one of Si
concentration, Ca concentration and Mg concentration.
[0208] If spark discharge is generated one thousand times, it is
expected that approximately one thousand data items of the Al
concentration data calculated as above are obtained. In short, a
very large number of data items of Al concentration can be obtained
with such a large number of times of generation of spark discharge.
Then, the calibration curve C representative of the relationship
between the Al concentration and the Al emission spectrum intensity
is formed based on the Al concentration data items [mass %] and the
emission spectrum intensities of Al (emitted from the real steel
masters) at times of generation of spark discharge when the
respective Al concentration data items were obtained (step S1312).
Particularly in the present process, when a test sample of the
center segregated portion 500 is used, a calibration curve C
representative of the relationship between the Al concentration and
the Al emission spectrum intensity in emission spots where the Al
concentration is higher can be obtained, whereas when a test sample
from a portion other than the center segregated portion 500 is
used, a calibration curve C representative of the relationship
between the Al concentration and the Al emission spectrum intensity
in emission spots where the Al concentration is lower can be
obtained.
[0209] Further, this real steel master has a ground composed of Fe,
which is preferable in that Al can be more correctly identified.
Thereafter, the formed calibration curve B is stored in the memory
of the data processing section 106 (step S1313), followed by
terminating the process.
[0210] According to the FIG. 13 process, it is possible to directly
obtain a calibration curve C covering a range from a trace Al
concentration in Al.sub.2O.sub.3 in the order of ppm to a
considerably large concentration in the order of percent, not by
extrapolation, but by using a real steel master.
[0211] Further, if the data of the Al.sub.2O.sub.3 particle sizes
of the calibration curve A determined as described earlier with
respect to the first embodiment, and the data of the Al emission
spectrum intensities of the calibration curve C are stored in the
memory of the data processing section 106, it is possible to use
these data as desired when an Al.sub.2O.sub.3 particle size
distribution is formed. The calibration curve C is used when the
calibration curve A is applied to an embodiment which is a
combination of the particle size-determining and particle size
distribution-generating method according to the first embodiment
and the particle size-determining (using a calibration curve E
described hereinafter with reference to FIG. 21) and particle size
distribution-generating method according to the second
embodiment.
[0212] Moreover, when the real steel master is used, the Al
concentration data are determined based on the Fe concentration
data, and as a result, even when the ground of the real steel
master contains Mg whose emission wavelength is close to that of
Al, it is possible to distinguish Al in an emission spectrum of
Al-contained inclusions from M therein, and hence form a
calibration curve C more accurately than when an Al alloy
containing more Mg is used as a master.
[0213] FIG. 16 is a flowchart of the calibration curve D-forming
process which is executed in the step S1202 in FIG. 12 to form the
calibration curve D concerning the emission spectrum intensity of
Fe and the evaporation loss of Fe.
[0214] The present calibration curve forming process is executed by
the emission spectrometer 100 at least once before the method of
determining particle sizes and a particle size distribution of
intermetallic inclusions contained in a test sample is repeatedly
carried out by the emission spectrometer 100.
[0215] In FIG. 16, first, a pure master formed of a steel material
containing no Al.sub.2O.sub.3 is held in the FIG. 1 emission
spectrometer 100 (step S1601), and spark discharge is generated on
the pure master held in Ar (step S1602), whereby spots of .phi.30
.mu.m (which is always held constant once set to the diameter, as
described above) are generated. Then, emission spectra of Fe from
the spots are separated (step S1603), and data of the emission
spectrum intensities of Fe are transmitted (step S1604). It is
preferred that the pure master is formed of pure iron. At the time
of emission, it is possible to form spot marks having various sizes
in the master by changing the discharge voltage from 10 kV by
.+-.30%.
[0216] Then, spot marks 800 (FIG. 17) having various sizes formed
at the time of the emission are observed three-dimensionally by a
SEM to thereby measure the depth and diameter of each spot mark 800
(step S1605) and determine the volume thereof. Then, the mass
(evaporation loss) of Fe which existed in each emission spot is
calculated based on the volume of the spot mark 800 and the density
of Fe (7.86 g/cm.sup.3), and the evaporation loss of Fe is input
(step S1606).
[0217] The evaporation loss of Fe is proportional to the emission
spectrum intensity of Fe obtained under a discharge condition which
caused the Fe evaporation loss (FIG. 18). Therefore, the
proportional relationship is adopted as a calibration curve D (step
S1607), and the calibration curve D is stored in the memory of the
data processing section 106 (step S1608). The formation of the
calibration curve D is carried out at least once.
[0218] It should be noted that data obtained by averaging data
items obtained when at most ten spark discharges are generated
under the same spark charging-condition is sufficient to form the
calibration curve D. The calibration curve D shows that the
emission spectrum intensity of Fe is proportional to the
evaporation loss of Fe.
[0219] The real particle size (particle size D) of an intermetallic
inclusion, such as Al.sub.2O.sub.3, in an emission spot of .phi.30
.mu.m formed by a single spark discharge generated on a test sample
(an object to be inspected) containing the intermetallic inclusion,
such as Al.sub.2O.sub.3, can be calculated by using the calibration
curve D. In the following, the calculation method will be
explained.
[0220] FIG. 19 is a flowchart of the calibration curve E-forming
process which is executed in the step S1203 in FIG. 12 to form the
calibration curve E representative of the relationship between the
emission spectrum intensity of Al and the Al particle size.
[0221] In the present calibration curve E-generating process,
intensities of Al and Fe emission spectra emitted from the same
emission spot of .phi.30 .mu.m whenever spark discharge is
generated once at an area of .phi.5 mm on the test sample surface
of .phi.40 mm are used to obtain the particle size D (radius) as
the real particle size of an intermetallic inclusion
(Al.sub.2O.sub.3) existing in the emission spot formed by the
single spark discharge by utilizing the calibration curve C formed
in the step S1312 in FIG. 13 and the calibration curve D formed in
the step S1607 in FIG. 16. In the following, a description will be
given by taking the case in which the intermetallic inclusions are
Al.sub.2O.sub.3 as an example.
[0222] In FIG. 19, first, respective data items of the emission
spectrum intensities of Fe, Al, (O) as information on the same
emission spot transmitted in a step S604 in FIG. 20 are fetched
(step S1901), and the fetched data item of Fe emission spectrum
intensity is substituted into the calibration curve D stored in the
memory of the data processing section 106 in the step S1202 in FIG.
12, whereby an evaporation loss [ng] of Fe is calculated (step
S1902).
[0223] Then, the data item of Al emission spectrum intensity
emitted from the same emission spot is substituted into the
calibration curve C stored as an Al calibration curve in the memory
of the data processing section 106 in the step S1201 in FIG. 12,
whereby an Al concentration [mass %] is calculated (step
S1903).
[0224] The mass M of Al.sub.2O.sub.3 is calculated from the
evaporation loss [ng] of Fe and the Al concentration [mass %]
determined as above, by using the following equation (8) (step
S1904):
Al concentration [%].times.10.sup.-2=M/(M+Fe evaporation loss)
(8)
[0225] Then, the volume V of Al.sub.2O.sub.3 is calculated from the
mass M of Al.sub.2O.sub.3 existing in a spot mark of .phi.30 .mu.m
corresponding to a unit volume and the density of Al.sub.2O.sub.3
(3.90 g/cm.sup.3), by using the following equation (9) (step
S1905):
V=M/3.90 (9)
[0226] Next, the Al.sub.2O.sub.3 particle having the volume V is
regarded as a perfect sphere, and the particle size D (diameter) of
the Al.sub.2O.sub.3 particle regarded as the perfect sphere is
calculated by using the following equation (10):
D/2=(3V/4.pi.).sup.1/3 (10)
[0227] In the FIG. 19 process, similarly to the first embodiment,
the concentration of Al contained in intermetallic inclusions can
be determined based on the Al emission spectrum intensity obtained
by emission spectral analysis, from the calibration curve C
representative of the relationship between the Al emission spectrum
intensity and the Al.sub.2O.sub.3 particle size, so that it is
possible to obtain the particle size D of the Al.sub.2O.sub.3
particle regarded as the perfect sphere. The Al.sub.2O.sub.3
particle size can be determined based on the corresponding Al
emission spectrum intensities by forming the calibration curve E,
i.e. this relationship which is a correspondence between the
concentration of Al as a constituent element of the intermetallic
inclusions and the Al.sub.2O.sub.3 particle size.
[0228] The mass M of Al.sub.2O.sub.3 calculated by the data
processing section 106 based on the relationship expressed by the
equation (8) can be also expressed by an equation (8') given
hereinbelow by rearranging the equation (8) as described below.
[0229] First, as described hereinbefore as to the step S1903, the
Al concentration [%] on the left side is determined as a
concentration [%] of Al existing in the spot mark of .phi.30 .mu.m
corresponding to the unit volume, by substituting the emission
spectrum intensity of Al emitted from the spot mark into the
calibration curve C.
[0230] Similarly, as described hereinbefore as to the step S1902,
the Fe evaporation loss [ng] on the right side is determined as an
evaporation loss [ng] of Fe which existed in the spot mark of
.phi.30 .mu.m corresponding to the unit volume, by substituting the
emission spectrum intensity of Fe emitted from the spot mark into
the calibration curve D obtained based on the spark discharge at
emission spots having the same diameter.
[0231] Now, the concentration [%] of Al existing in the spot mark
of .phi.30 .mu.m corresponding to the unit volume can be converted
to the mass A [ng] of Al. In the calibration curve C, the
concentration of Al is determined for each spot of .phi.30 .mu.m,
and this is the same with a test sample, so that the weight of Al
existing within an area of .phi.30 .mu.m can be considered both for
the calibration curve C and for the test sample.
[0232] The mass A [ng] of Al can be obtained as a ratio of the mass
A [atomic weight of 26.8, formula weight of 54] of Al.sub.2 to the
mass M of Al.sub.2O.sub.3 (formula weight of 102) as follows:
A=0.53M (11)
[0233] Using 0.53 in the above equation (11), the equation (8) can
be rearranged for the mass M of Al.sub.2O.sub.3 as follows:
M=Al concentration [%].times.Fe evaporation loss/(0.53-Al
concentration [%]).times.10.sup.-4 (8')
[0234] In this way, the mass M of Al.sub.2O.sub.3 existing in the
spot mark of .phi.30 .mu.m corresponding to the unit volume can be
determined.
[0235] As described above, the calibration curve E (FIG. 21) for
use in calculating Al.sub.2O.sub.3 particle sizes based on the
emission spectrum intensity of Al as a constituent element of the
intermetallic inclusions can be formed (step S1907). The formed
calibration curve E is stored (step S1908), followed by terminating
the calibration curve E-forming process which is executed in the
step S1203 in FIG. 12. By storing the calibration curve E in the
memory of the data processing section 106 in the step S1203 in FIG.
12, it is possible to dispense with arithmetic operations by the
equations (8) to (10).
[0236] It should be noted that as emission spectrum intensities of
the test sample used in forming the calibration curve E in the FIG.
19 process, emission spectrum intensities measured in steps S601 to
S604 in FIG. 20, hereinafter referred to, may be utilized. Needless
to say, when the calibration curve E has already been stored, it is
possible to easily calculate the particle sizes D of intermetallic
inclusions contained in the test sample from the emission spectrum
intensities of the test sample measured in a FIG. 20 process,
described below, based on the calibration curve E.
[0237] FIG. 20 is a flowchart of the particle size
distribution-generating process which is executed in the step S1204
in FIG. 12.
[0238] It should be noted that steps S601 to S605 and steps S607 to
S608 are identical to those of the FIG. 6 particle size
distribution-generating process of the first embodiment.
[0239] In FIG. 20, first, a test sample (an object to be inspected)
is held (step S601), and spark discharge is generated e.g. one
thousand times (step S602), emission spectra are separated (step
S603), and data of emission spectrum intensities are transmitted
(step S604). Then, similarly to the processing in the step S605 in
FIG. 6, intermetallic inclusions are identified (step S605). Since
this example is a case where attention is paid to the
Al.sub.2O.sub.3 inclusions as intermetallic inclusions, from the
emission spectrum intensities of lots of elements emitted by the
spark discharge, only data containing information on Al, O, and Fe
alone are extracted as follows.
[0240] Now, when a spark discharge is generated once, an area of
.phi.30 .mu.m containing Al.sub.2O.sub.3 is selectively changed
into an emission (discharge) spot due to the dielectric property of
Al.sub.2O.sub.3. In the spot mark, only Fe as the ground has
evaporated to disappear, whereas only Al.sub.2O.sub.3 having a
higher melting point than that of Fe remains without being
evaporated. It should be noted that out of the intensities of
emission spectra of lots of elements emitted by the spark
discharge, attention is paid to only data containing information on
Al, O, and Fe alone, and hence it can be considered that only
Al.sub.2O.sub.3 except for Fe exists in the emission spot of
.phi.30 .mu.m subjected to a single spark discharge.
[0241] Thereafter, an intermetallic inclusion particle
size-calculating process for calculating the particle size D of the
Al.sub.2O.sub.3 from the Al emission spectrum intensity based on
the calibration curve E is (step S2006). Then, the obtained
particle size D of the Al.sub.2O.sub.3 is input as A.sub.x(K) in
the FIG. 8 data sorting process, described hereinbefore, and after
execution of the FIG. 9 data sorting process for rearranging
particle sizes in size-increasing order and the FIG. 10 data
sorting process for determining frequencies (step S607), the data
processing section 106 generates a diagram shown in FIG. 27A and
stores the same in the memory, and at the same time displays the
FIG. 27A diagram on the terminal unit(step S608).
[0242] According to the FIG. 20 process, not the apparent diameter
but the particle size D as the real particle size (sphere diameter)
is determined, and as a result, it is possible to determine the
particle sizes of intermetallic inclusions more accurately and
generate a more accurate particle size distribution of the
intermetallic inclusions.
[0243] According to the second embodiment, as shown in the FIG. 27A
diagram of Al.sub.2O.sub.3 particle size distribution, it is
possible to extract lots of Al.sub.2O.sub.3 inclusions having small
particle sizes in a particle size distribution from a steel as a
material for roller bearings, and to extract lots of
Al.sub.2O.sub.3 inclusions within a particle size range of 3 to 13
.mu.m which affect the rolling life of the roller bearings, as well
as to extract a large number of intermetallic inclusions as a
whole. This makes it possible to determine particle sizes more
accurately and generate a more accurate particle size distribution.
These merits can be utilized as a correct index for predicting the
rolling life of the roller bearings and for determining how to set
the pureness of a steel material for a longer rolling life
thereof.
[0244] In the process of the step S605 in FIG. 20, when the data of
the intensities of the emission spectra of the elements X as
constituent elements of intermetallic inclusions include no data
items whose values are equal to or larger than the respective
corresponding threshold values, it is presumed that there exist
elements not to be determined (e.g. elements composing carbides,
other than carbon), or that the lens is stained or
deteriorated.
[0245] The correction process related to the stain/deterioration of
the lens will be described in detail in the description of the
third embodiment, given hereinafter. Needless to say, it is
preferable that the correction process according to the third
embodiment is executed in combination with the second
embodiment.
[0246] Next, a particle size-determining and particle size
distribution-generating method according to the third embodiment
will be described in detail with reference to the drawings.
[0247] Next, a particle size-determining and particle size
distribution-generating method according to the third embodiment
will be described in detail with reference to the drawings.
[0248] The particle size-determining and particle size
distribution-generating method of the third embodiment is also
carried out by the FIG. 1 emission spectrometer 100, in generating
a particle size distribution of intermetallic inclusions contained
in a test sample cut out from a steel material.
[0249] The particle size-determining and particle size
distribution-generating method of the third embodiment is
distinguished from the particle size-determining and particle size
distribution-generating method of the first and second embodiments
in that compensation is made for attenuation of emission spectrum
intensities due to stains on the condensing lens 108.
[0250] A description will now be given of the intermetallic
inclusion particle size-determining and particle size
distribution-generating process executed by the FIG. 1 emission
spectrometer 100 with reference to the drawings.
[0251] FIG. 22 is a flowchart of the intermetallic inclusion
particle size-determining and particle size distribution-generating
process according to the third embodiment.
[0252] In FIG. 22, first, the FIG. 2 calibration curve A-forming
process in the first embodiment is executed (step S201), a
correction curve generating process, described hereinafter with
reference to FIG. 23, is executed (step S2201), and a particle size
distribution-generating process, described hereinafter with
reference to FIG. 25, is executed (step S2202).
[0253] It should be noted that the process in the step S201 has
been described with reference to FIG. 2, and hence description
thereof is omitted. Further, as the calibration curve A, there may
be used one used at least once in the FIG. 3 calibration curve
A-forming process and stored in the memory of the data processing
section 106.
[0254] FIG. 23 is a flowchart of the intensity correction
curve-generating process which is executed in the step S2201 in
FIG. 22.
[0255] The present process is also executed by the emission
spectrometer 100 at least once before the particle size
distribution-generating process for generating a particle size
distribution of intermetallic inclusions in a test sample is
repeatedly carried out by the emission spectrometer 100 (e.g. when
the emission spectrometer 100 is installed in a quality inspection
line).
[0256] In FIG. 23, first, after a master cut out from a steel
material formed e.g. of SUJ2 containing Al.sub.2O.sub.3 is held in
the light emitting stand 102 (step S2301), the surface of the
master is scanned by the EPMA to thereby determine particle sizes
of Al.sub.2O.sub.3 existing in the surface of the master (step
S2302). Further, an Al.sub.2O.sub.3 particle whose particle size is
the closest to 15 .mu.m of all the determined particle sizes is
selected (step S2303), and data of the location of the selected
Al.sub.2O.sub.3 particle is transmitted to the data processing
section 106 (step S2304), and the data processing section 106
stores the received data of the location in the memory thereof.
[0257] Then, spark discharge is repeatedly generated on the
selected Al.sub.2O.sub.3 particle by the counter electrode of the
light-emitting section 101, and whenever spark discharge is
generated one thousand times, the intensity of an emission spectrum
then emitted from the selected Al.sub.2O.sub.3 particle is measured
(step S2305). Data of the measured emission spectrum intensity is
transmitted to the data processing section 106 via the interface
105 (step S2306). On the other hand, the light emitting stand 102
transmits data of the number of times of generation of spark
discharge to the data processing section 106 via the interface 105.
Thereafter, the data processing section 106 stores the data of the
emission spectrum intensity and the data of the number of times of
generation of spark discharge which have been received in the
memory thereof.
[0258] Then, the data processing section 106 forms a intensity
correction curve, described hereinafter with reference to FIG. 14,
which is representative of the relationship between the number of
times of generation of spark discharge and the amount of
attenuation of emission spectrum intensity, based on the data of
the number of times of generation of spark discharge and the
emission spectrum intensities which have been stored in the memory
(step S2307), and stores the formed intensity correction curve in
the memory (step S2308), followed by terminating the present
process.
[0259] FIG. 24 is a diagram showing the intensity correction curve
formed in the step S2201 in FIG. 22.
[0260] In FIG. 24, the amount of attenuation of emission spectrum
intensity is calculated as the difference between an emission
spectrum intensity corresponding to a 0-th spark discharge and an
emission spectrum intensity corresponding to each 1000-th spark
discharge, and indicated as a correction value on the ordinate.
When the number of times of generation of spark discharge is
represented by i, an emission spectrum intensity before correction
by I(i), and an emission spectrum intensity after correction by
I'(i), I'(i) is expressed by the following equation (12):
I'(i)=I(i)+0.107i (12)
[0261] It should be noted that a test sample can contain
intermetallic inclusions other than Al.sub.2O.sub.3, it is
desirable that the FIG. 25 intensity correction curve should be
also formed for each of the other intermetallic inclusions, such as
CaO.
[0262] According to the FIG. 23 process, an Al.sub.2O.sub.3
particle whose particle size is as large as the size of an
Al.sub.2O.sub.3 particle contained in a test sample and the closest
to 15 .mu.m is selected (step S2303), and the intensity of an
emission spectrum emitted from the selected Al.sub.2O.sub.3
particle is measured whenever spark discharge is generated one
thousand times (step S2305), whereby the intensity correction curve
representative of the relationship between the number of times of
generation of spark discharge and the amount of attenuation of
emission spectrum intensity is formed based on the data of the
number of times of generation of spark discharge and the emission
spectrum intensity (step S2307). Therefore, the formed intensity
correction curve is based on the Al.sub.2O.sub.3 particle having a
particle size closest to that of the Al.sub.2O.sub.3 particle
contained in the test sample. This enables the correction of the
intensity of emission spectra condensed by the condensing lens 108
to provide a reliable emission spectrum intensity after the
correction. Further, even if the condensing lens 108 is not cleaned
over a predetermined time period (corresponding to approximately
3000 times of generation of spark discharge), it is possible to
accurately predict an emission spectrum intensity which could be
obtained if the emission spectrum were condensed by the clean
condensing lens 108, based on the number of times of generation of
spark discharge.
[0263] FIG. 25 is a flowchart of the particle size
distribution-generating process which is executed in the step S2202
in FIG. 22.
[0264] The present process is executed by the emission spectrometer
100 whenever particle size distribution of intermetallic inclusions
contained in a test sample is repeatedly generated after the FIG.
23 process by the emission spectrometer 100 is executed at least
once.
[0265] In FIG. 25, steps S601 to S605 and steps S606 to S608 are
identical to those of the FIG. 6 process, and hence description
thereof is omitted.
[0266] First, the steps S601 to S605 are executed. Then, the data
processing section 106 corrects data of the emission spectrum
intensity of each element stored in the memory, based on the data
of the number of times of generation of spark discharge and the
intensity correction curve stored in the memory (step S2501), and
stores the corrected data of the emission spectrum intensity of
each element in the memory. Then, the steps S606 to S608 are
executed, followed by terminating the present process.
[0267] According to the FIG. 25 process, the data processing
section 106 corrects the data of the emission spectrum intensity of
each element stored in the memory, based on the data of the number
of times of generation of spark discharge and the intensity
correction curve stored in the memory (step S2501), it is possible
to correct the emission spectrum in real time.
[0268] Although in the above described third embodiment, the
attenuation of emission spectrum intensity due to stains on the
condensing lens 108 is corrected based on the particle
size-determining and particle size distribution-generating method
according to the first embodiment, it may be corrected based on the
particle size-determining and particle size distribution-generating
method according to the variation of the first embodiment or the
second embodiment.
[0269] In the first to third embodiments of the invention, in the
processes in FIGS. 3, 12 and 19, the data processing section 106
may store calibration curves for intermetallic inclusions other
than the Al.sub.2O.sub.3 (e.g. CaO, SiO, MnS, etc.), or
alternatively in the FIG. 23 process, the data processing section
106 may store calibration curves and intensity correction curves
for the intermetallic inclusions other than Al.sub.2O.sub.3, to
thereby generate particle size distributions of a plurality of
kinds of intermetallic inclusions contained in the test sample at a
time. Further, by providing sufficient calibration curves and
intensity correction curves for intermetallic inclusions, when it
is found that intermetallic inclusions contained in a test sample
are composed of two or more kinds of elements, it is possible to
more easily identify whether constituent elements are single
substances, or form a compound or a mixture.
[0270] Further, although in the above embodiments of the present
invention, in the FIG. 9 data sorting process, the row AL.sub.x in
which the data items I.sub.x are rearranged in intensity-increasing
order is obtained, this is not limitative, but a row AL.sub.x in
which the data items I.sub.x are rearranged in intensity-decreasing
order may be obtained.
[0271] Moreover, although the arithmetic operations, such as the
data sorting, are carried out by the emission spectrometer 100 and
the data processing section 106, this is not limitative, but the
arithmetic operations may be carried out by an arithmetic
processor, a storage medium, or any other device which is capable
of storing program modules for the arithmetic operations or
executing programs for the arithmetic operations, in place of the
emission spectrometer 100 and the data processing section 106, or
alternatively, a combination of these devices may be used.
[0272] In the following, a first example of the present invention
will be described in detail.
[0273] In the first example of the present invention, the particle
size-determining and particle size distribution-generating method
according to the first embodiment was carried out.
[0274] A material of SUJ2 having a relatively high degree of
pureness was prepared, and a cylindrical test sample having a
diameter of .phi.40 mm was cut out from the prepared SUJ2 material.
Then, after the FIG. 2 process was executed to thereby generate a
particle size distribution of Al.sub.2O.sub.3 existing in an area
of .phi.5 mm at an arbitrary location on the surface of the test
sample, the determined area of .phi.5 mm was scanned by the EPMA as
well, whereby the particle size distribution of Al.sub.2O.sub.3 was
generated and confirmed.
[0275] FIGS. 26A and 26B are diagrams for comparison between the
Al.sub.2O.sub.3 particle size distribution (a) generated by
execution of the FIG. 2 process and the particle size distribution
(b) generated by the EPMA.
[0276] As is apparent from FIGS. 26A and 26B, it was recognized
that there is a close agreement between the Al.sub.2O.sub.3
particle size distribution (a) generated by execution of the FIG. 2
process and the particle size distribution (b) generated by the
EPMA, and hence it was found that the intermetallic inclusion
particle size distribution-generating method of the present
invention is as accurate as the conventional method utilizing the
EPMA.
[0277] Further, it was found that in the method in which the
Al.sub.2O.sub.3 particle size distribution is generated by
execution of the FIG. 2 process, it takes only 60 seconds (one
minute) or so to generate the distribution, which means that the
intermetallic inclusion particle size distribution-generating
method of the present invention is capable of quickly generating a
particle size distribution of intermetallic inclusions.
[0278] A second example of the invention will now be described in
detail.
[0279] In the second example of the present invention, the particle
size-determining and particle size distribution-generating method
according to the second embodiment was carried out.
[0280] Cylindrical test samples each having a diameter of .phi.40
mm were cut out, respectively, from different steel materials of 17
types, of which the Fe concentration had been previously determined
and thus known, and the emission spectrum intensity of Fe contained
in each of the test samples was measured for execution of the
calibration curve B-forming process in the step S1201 in FIG. 12
(Examples 1 to 17). The results of the measurements are shown in
Table 1 given hereinbefore and FIG. 14. It should be noted that
intermetallic inclusions contained in the 17 types of steel
materials were not limited to Al.sub.2O.sub.3 and the ground
thereof was Fe.
[0281] From Table 1 and FIG. 14, it was found that it is possible
to obtain a calibration relationship (calibration curve B) between
the Fe concentration [mass %] and the Fe emission spectrum
intensity, as shown in FIG. 14, even from different types of steel
materials so long as each steel material has Fe as the ground,
particularly when the Fe concentration is low, i.e. when the
concentration of intermetallic inclusions is high.
[0282] According to the process which is executed in the step S1201
in FIG. 12, the calibration curve B can be obtained even when Fe
concentration is low, i.e. when the concentration of intermetallic
inclusions is high, and it is possible to determine Al
concentration with ease when there is no intermetallic inclusion
other than Al.sub.2O.sub.3. Therefore, the calibration curve B and
the calibration curve C can be directly obtained by the emission
spectrometer 100 alone, without using the calibration curve A as
shown in FIG. 5, which is formed by using the EPMA, more
specifically, by using a steel material for actual use and without
extrapolating a calibration curve covering a range of Al
concentration in Al.sub.2O.sub.3 from a trace concentration in the
order of ppm to a considerably large concentration in the order of
percent.
[0283] After the execution of the step S1201 in FIG. 12, a
cylindrical test sample having a diameter of .phi.40 mm was further
cut out from a steel material containing no Al.sub.2O.sub.3, and
the step S1202 in FIG. 12 was executed. Then, discharge voltage to
be applied to the test sample for emission spectral analysis was
changed from 10 kV by .+-.30% to thereby determine the volumes of
spot marks through the three-dimensional SEM observation, and the
relationship between the amount of evaporation of Fe calculated
based on the volumes of the spot marks and the density of Fe and
the spot diameter of the spot marks was examined. The results of
the examination are shown in Table 2 and FIG. 18.
2TABLE 2 Spot Diameter Evaporation Loss Emission Spectrum [.mu.m]
[ng] Intensity 5 0.30 1406 10 0.50 2836 15 0.90 5121 20 1.20 7187
25 1.40 9003 30 1.65 10872 35 1.90 13569 40 2.10 16419
[0284] It was proved from Table 2 and FIG. 18 that there is a
proportional relationship (calibration curve D) between the amount
of Fe evaporation caused by a single spark discharge and the
emission spectrum intensity of Fe.
[0285] According to the above process, it was proved that it is
possible to obtain perfect-sphere radiuses (particle sizes D) of
intermetallic inclusions, such as Al.sub.2O.sub.3, contained in the
test sample (an object to be inspected) in which intermetallic
inclusions, such as Al.sub.2O.sub.3, exist, based on the
calibration curve D and the Al concentration determined from the
above calibration curve C.
[0286] Further, in the process which is executed in the step S1204
in FIG. 12, a cylindrical test sample (an object to be inspected)
having a diameter of .phi.40 mm was cut out from a SUT-2 material
to be actually examined, and the particle size distribution of
Al.sub.2O.sub.3 existing in an area of .phi.5 mm at an arbitrary
location on the surface of the object to be inspected was generated
by execution of the FIG. 12 process. Then, a particle size
distribution of Al.sub.2O.sub.3 in the determined area of .phi.5 mm
was also generated by the image analysis method and confirmed.
[0287] FIGS. 27A and 27B are diagrams for comparison between the
Al.sub.2O.sub.3 particle size distribution (a) generated by
execution of the FIG. 12 process and the particle size distribution
(b) generated by the image analysis method.
[0288] As is apparent from FIGS. 27A and 27B, the comparison
between the Al.sub.2O.sub.3 particle size distribution (a)
generated by execution of the FIG. 12 process and the particle size
distribution (b) generated by the image analysis method showed that
the Al.sub.2O.sub.3 particle size distribution (a) generated by
execution of the FIG. 12 process is more accurate than the particle
size distribution (b) generated by the image analysis method in
that lots of Al.sub.2O.sub.3 particles having small particle sizes
are extracted in the particle size distribution concerning the
Al.sub.2O.sub.3 inclusion in the steel as a material for roller
bearings; lots of Al.sub.2O.sub.3 particles within a range of 3 to
13 .mu.m which affect the rolling life of the roller bearings are
extracted; and a larger number of intermetallic inclusions are
extracted as a whole.
[0289] This shows that the FIG. 12 process gives more accurate
results than the conventional extrapolation method in which high Al
concentrations in the order of percent are extrapolated into a
calibration curve, since the execution of the former provides the
calibration curve B indicative of the concentration of Al in
intermetallic inclusions covering up to high Al concentrations in
the order of percent by using the actually used SUJ-2 material and
the calibration curve D which estimates the real particle sizes of
intermetallic inclusions, such as Al.sub.2O.sub.3,
three-dimensionally and correctly. Further, since the FIG. 12
process is executed simply by using the emission spectral analysis,
without preparing special masters or using the EPMA method, it is
possible to provide a simple and easy particle size-determining and
particle size distribution-generating method.
[0290] Industrial Applicability
[0291] According to the invention as claimed in claims 1 and 11, an
intermetallic inclusion particle size-intensity calibration curve
representative of the relationship between particle size of
intermetallic inclusions and emission spectrum intensity of a
constituent element of the intermetallic inclusions is formed. This
makes it possible to identify what form is assumed by the
intermetallic inclusions from elements constituting the
intermetallic inclusions and quickly and accurately determine or
measure particle sizes and particle size distribution of the
intermetallic inclusions.
[0292] According to the apparatuses as claimed in claims 2 and 12,
the particle size of the intermetallic inclusions in the
predetermined area of the reference sample is determined through
surface analysis by an electron probe microanalyzer. This enables
quick and accurate determination or measurement of the particle
size and particle size distribution of the intermetallic
inclusions.
[0293] According to the invention as claimed in claims 3 and 13,
there are formed a principle component known
concentration-intensity calibration curve representative of the
relationship between the emission spectrum intensity of the
principle component having an already known concentration and the
known concentration of the principle component, a real steel
material-contained intermetallic inclusion constituent element
concentration-intensity calibration curve representative of the
relationship between the concentration of the constituent element
of the intermetallic inclusions and the emission spectrum intensity
of the constituent element of the intermetallic inclusions, and a
base element evaporation amount-intensity calibration curve
representative of the relationship between the base element
evaporation amount and the intensity of emission spectra emitted
from the base element. This enables quick and more accurate
determination or measurement of real particle sizes and particle
size distribution of the intermetallic inclusions.
[0294] According to the invention as claimed in claims 4 and 14,
there is formed an intermetallic inclusion particle size-intensity
calibration curve representative of the relationship between the
calculated particle size of the intermetallic inclusions and the
determined emission spectrum intensity of the constituent element
of the intermetallic inclusions. This enables quicker and more
accurate determination of real particle sizes and particle size
distribution of the intermetallic inclusions.
[0295] According to the invention as claimed in claims 5 and 15, a
data sorting process for counting the number of data items is
executed to thereby generate a particle size distribution of the
intermetallic inclusions in the test sample. This makes it possible
to identify what form is assumed by the intermetallic inclusions
from elements constituting the intermetallic inclusions and quickly
and accurately determine or measure particle sizes and particle
size distribution of the intermetallic inclusions.
[0296] According to the invention as claimed in claims 6 and 16,
the data items of emission spectra of the constituent element of
intermetallic inclusions in the test sample are rearranged in order
of intensity, and then the number of the rearranged data items is
counted. This makes it possible to facilitate processing of the
data.
[0297] According to the invention as claimed in claims 7 and 17,
data items of emission spectrum intensity of a constituent element
of intermetallic inclusions in the test sample to be rearranged in
order of intensity are extracted by determining whether or not an
emission spectrum intensity of the constituent element of the
intermetallic inclusions in the test sample is larger than a
threshold value. This makes it possible to reduce the number of the
data.
[0298] According to, according to the invention as claimed in
claims 8 and 18, the data items of emission spectrum intensity of
the constituent element of the intermetallic inclusions in the test
sample to be rearranged in order of intensity are extracted based
on a result of comparison between the emission spectrum intensity
of a principle component of the test sample and the emission
spectrum intensity of the constituent element of the intermetallic
inclusions in the test sample. This makes it possible to reduce the
number of the data and quickly extract data items to be rearranged
in order of intensity.
[0299] According to the invention as claimed in claims 9 and 19,
emission spectrum intensity of a constituent element of the
intermetallic inclusions in the test sample is corrected according
to the number of times of generation of spark discharge. This
enables quicker and more accurate determination or measurement of
particle sizes and particle size distribution of the intermetallic
inclusions.
[0300] According to the invention as claimed in claims 10 and 20, a
kind of the constituent element of the intermetallic inclusions is
identified based on a result of comparison between the intensity of
emission spectra of a principle component of the test sample and
the intensity of emission spectra of the constituent element of the
intermetallic inclusions in the test sample. This makes it possible
to positively reduce the number of data items and more quickly and
more accurately determine or measure particle sizes and particle
size distribution of the intermetallic inclusions.
* * * * *