U.S. patent application number 12/312567 was filed with the patent office on 2010-03-04 for machining steel superior in manufacturability.
Invention is credited to Jun Aoki, Masayuki Hashimura, Seiji Ito, Kenichiro Miyamoto, Atsushi Mizuno.
Application Number | 20100054984 12/312567 |
Document ID | / |
Family ID | 39467977 |
Filed Date | 2010-03-04 |
United States Patent
Application |
20100054984 |
Kind Code |
A1 |
Hashimura; Masayuki ; et
al. |
March 4, 2010 |
MACHINING STEEL SUPERIOR IN MANUFACTURABILITY
Abstract
The present invention provides machining steel superior in
machinability, accompanied with little melt loss of plate
refractories of continuous casting sliding nozzles, and superior in
ductility in hot rolling and able to prevent deterioration of the
surface properties due to hot rolling, containing, by mass %, C:
0.005 to 0.2%, Si: 0.001 to 0.5%, Mn: 0.3 to 3.0%, P: 0.001 to
0.2%, S: 0.30 to 0.60%, B: 0.0003 to 0.015%, O: 0.005 to 0.012%,
Ca: 0.0001 to 0.0010%, and Al.ltoreq.0.01%, having an N content
satisfying N.gtoreq.0.0020% and
1.3.times.B-0.0100.ltoreq.N.ltoreq.1.3.times.B+0.0034, and having a
balance of Fe and unavoidable impurities, wherein, regarding the
MnO in the steel, in a cross-section of the steel material
perpendicular to the rolling direction, the area of MnO of a circle
equivalent diameter of 0.5 .mu.m or more being 15% or less of the
area of the total Mn-based inclusions.
Inventors: |
Hashimura; Masayuki; (Tokyo,
JP) ; Mizuno; Atsushi; (Tokyo, JP) ; Miyamoto;
Kenichiro; (Tokyo, JP) ; Aoki; Jun; (Tokyo,
JP) ; Ito; Seiji; (Tokyo, JP) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
39467977 |
Appl. No.: |
12/312567 |
Filed: |
November 27, 2007 |
PCT Filed: |
November 27, 2007 |
PCT NO: |
PCT/JP2007/073277 |
371 Date: |
May 14, 2009 |
Current U.S.
Class: |
420/84 ;
420/87 |
Current CPC
Class: |
C22C 38/004 20130101;
C22C 38/60 20130101; C22C 38/02 20130101; C22C 38/002 20130101;
C22C 38/04 20130101; C22C 38/06 20130101; C21D 6/005 20130101; C22C
38/001 20130101; C22C 38/008 20130101 |
Class at
Publication: |
420/84 ;
420/87 |
International
Class: |
C22C 38/60 20060101
C22C038/60; C22C 38/00 20060101 C22C038/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2006 |
JP |
2006-319895 |
Claims
1. Machining steel superior in manufacturability containing, by
mass %, C: 0.005 to 0.2% Si: 0.001 to 0.5% Mn: 0.3 to 3.0% P: 0.001
to 0.2% S: 0.30 to 0.60% B: 0.0003 to 0.015% O: 0.005 to 0.012% Ca:
0.0001 to 0.0010%, and Al.ltoreq.0.01%, having an N content
satisfying N.gtoreq.0.0020% and
1.3.times.B-0.0100.ltoreq.N.ltoreq.1.3.times.B+0.0034, and having a
balance of Fe and unavoidable impurities, wherein further,
regarding the MnO in the steel, in a cross-section of the steel
material perpendicular to the rolling direction, the area of MnO of
a circle equivalent diameter of 0.5 .mu.m or more being 15% or less
of the area of the total Mn-based inclusions.
2. Machining steel superior in manufacturability as set forth in
claim 1, wherein, regarding the sulfides mainly comprised of MnS,
in a cross-section of the steel material perpendicular to the
rolling direction, a density of sulfides of a circle equivalent
diameter of 0.1 to 0.5 .mu.m is 10000/mm.sup.2 or more.
3. Machining steel superior in manufacturability as set forth in
claim 1, further containing, by mass %, one or more of V: 0.05 to
1.0% Nb: 0.005 to 0.2% Cr: 0.01 to 2.0% Mo: 0.05 to 1.0% W: 0.05 to
1.0% Ni: 0.05 to 2.0% Cu: 0.01 to 2.0% Sn: 0.005 to 2.0% Zn: 0.0005
to 0.5% Ti: 0.0005 to 0.1% Zr: 0.0005 to 0.1% Mg: 0.0003 to 0.005%
Te: 0.0003 to 0.2% Bi: 0.005 to 0.5% Pb: 0.005 to 0.5%.
Description
TECHNICAL FIELD
[0001] The present invention relates to low carbon machining steel
used for automobiles, general machinery, etc. where machinability
is required more than strength characteristics, more particularly
relates to machining steel superior in tool life at the time of
machining, finished surface roughness, chip evacuation, and other
machinability, accompanied with little melt loss of plate
refractories of the continuous casting sliding nozzles, and
superior in manufacturability with good ductility in hot
rolling.
BACKGROUND ART
[0002] General machinery and automobiles are manufactured by
assembling a large number of types of parts. The parts are in most
cases produced through machining processes from the viewpoint of
the required precision and manufacturing efficiency. At that time,
reduction of costs and improvement of production efficiency are
demanded. Improvement of the machinability is being demanded from
the steel as well. In particular, low carbon sulfur machining steel
SUM23 and low carbon sulfur-lead composite machining steel SUM24L
have been invented stressing the machinability. Up to now, to
improve the machinability, it has been known that addition of S,
Pb, and other machinability improving elements is effective.
However, depending on the user, sometimes use of Pb is avoided due
to the environmental load. The amount of use is being reduced as a
general direction.
[0003] Up to now as well, when desiring not to add Pb, the
technique has been used of forming inclusions such as sulfides
mainly comprised of MnS which become soft under the machining
environment so as to improve the machinability. However, the low
carbon sulfur-lead composite machining steel SUM24L has the same
amount of S added to it as low carbon sulfur machining steel SUM23.
Therefore, it is necessary to add an amount of S greater than the
past. However, with the addition of a large amount of S, just
making the sulfides mainly comprised of MnS coarse was not
effective for improving the machinability. Further, the problems
arise that it is not possible to make the matrix sufficiently
brittle and deterioration of the finished surface roughness along
with the phenomena of pieces of the built-up cutting edge breaking
off and chips not being removed and that chip evacuation becomes
poor due to insufficient removal of chips. Furthermore in the
rolling, forging, and other production processes, coarse sulfides
mainly comprised of MnS become starting points of breakage and
cause numerous problems in production such as rolling defects.
There are limits with just the increase of the amount of S.
Further, addition of machinability improving elements other than S
such as Te, Bi, P, N, etc. can also improve the machinability to a
certain extent, but at the time of rolling or hot forging,
deterioration of the surface properties such as cracks and defects
are caused, so it is considered desirable that these be as small as
possible. It is not possible to achieve both machinability and
manufacturability.
[0004] Japanese Patent Publication (A) No. 11-222646 proposes the
method of introducing 30 or more independent sulfides of 20 .mu.m
or more or groups of sulfides of lengths of a plurality of sulfides
connected in substantially straight lines of 20 .mu.m or more in a
1 mm.sup.2 field of the cross-section in the rolling direction so
as to improve the chip evacuation. However, in actuality, no
allusion is made, including of the method of production, of the
dispersion of submicron level sulfides most effective for
machinability. Further, this cannot be expected from the
ingredients either.
[0005] There have been examples of attempts to use inclusions other
than sulfides to improve the machinability up to now as well. For
example, Japanese Patent Publication (A) No. 9-17840, Japanese
Patent Publication (A) No. 2001-329335, Japanese Patent Publication
(A) No. 2002-3991, and Japanese Patent Publication (A) No.
2000-178683 are art using BN to improve the machinability. However
these are not intended for improving the finished surface
roughness. In Japanese Patent Publication (A) No. 9-17840, Japanese
Patent Publication (A) No. 2001-329335, and Japanese Patent
Publication (A) No. 2000-178683, the object is the improvement of
the tool life, while in Japanese Patent Publication (A) No.
2002-3991, the object is the improvement of the chip evacuation. In
applications in the chemical ingredients of the ranges of the
examples disclosed in these, a sufficient effect cannot be obtained
in improvement of the finished surface roughness. Specifically,
unless the matrix is made uniform by the fine dispersion of BN in
the steel, the effect of improvement of the finished surface
roughness cannot be obtained, but these patent documents do not
describe this art.
[0006] The art disclosed in Japanese Patent Publication (A) No.
2004-176176 is also an example of attempted use of BN for
improvement of the machinability. This considers the balance with
the amount of addition of N. However, in this art, the balance of
the chemical ingredients of the steel for completely suppressing
the occurrence of rolling defects while securing the
machinability--an opposite property--and the method of suppressing
the amount of oxides of B with a high affinity with oxygen to make
B precipitate as BN were not discovered.
[0007] Japanese Patent Publication (A) No. 5-345951 is art
improving the machinability by increasing the concentration of
oxygen in the steel so as to make the MnS larger in size. However,
in this art, the reduction of MnS due to the increase in the oxygen
and the accompanying reduction of the machinability are not alluded
to at all. Furthermore, measures for preventing melt loss of
refractories, increase of surface defects, and other remarkable
deterioration of the manufacturability are not touched upon
either.
[0008] Further, Japanese Patent Publication (A) No. 2001-329335, to
improve the hot ductility, discloses the art of suppressing grain
boundary embrittlement due to precipitation of BN at the grain
boundaries and furthermore limiting the amount of N added for
making use of the action of solid-solute B in preventing grain
boundary embrittlement. However, this only reduces the amount of N.
Control of the amount of solid-solute N in the BT heating to work
temperature range is not sufficiently considered. The amount of
solid-solute N is not sufficiently reduced as required for
preventing defects. Further, the amount of N is limited to one
lower than the stoichiometric composition, so the amount of BN is
insufficient for improving the finished surface roughness. Using
other art for making up for this is not considered at all as well,
so it is not possible to obtain a good finished surface
roughness.
[0009] Further, Japanese Patent Publication (A) No. 2004-27297
proposes the art of reducing the surface defects by limiting the
amount of oxygen in the steel. However, the method of control of
the amount of oxygen in the steel is not alluded to at all. In
unkilled low carbon machining steel, without special control, it is
impossible to limit the amount of oxygen in the steel and prevent
occurrence of defects.
[0010] There have been examples of adding Ca for improving the
machinability in low carbon machining steel up to now as well. For
example, in Japanese Patent Publication (A) No. 2000-160284, the
specific effect of improving the machinability is not described.
Further, the range of the amount of addition of Ca is broad. The
amount of addition effective for improving the machinability is
also not described.
[0011] Further, when producing low carbon machining steel with the
addition of B by continuous casting, there is the problem of easy
melt loss of the plate refractories of the sliding nozzles. No
prior art document solving this problem can be found.
DISCLOSURE OF THE INVENTION
[0012] The present invention provides low carbon machining steel
used for automobiles, general machinery, etc. particularly
machining steel superior in tool life at the time of machining,
finished surface roughness, chip evacuation, and other
machinability, accompanied with little melt loss of plate
refractories of the continuous casting sliding nozzles, and
superior in ductility in hot rolling, and able to prevent
deterioration of the surface properties due to hot rolling.
[0013] Machining is a phenomenon of removal of chips. Promoting
this is one of the key points. However, as already explained, there
are limits with just increasing the S. Further, to achieve both
machinability and manufacturability, it is also necessary to
consider the amounts of the machinability improving elements.
[0014] Therefore, the inventors discovered that by controlling the
amount of solid-solute N in the rolling temperature range and
controlling the ratio of the amounts of B and N required for
obtaining the BN required for machinability at room temperature
where machining is performed, it is possible to achieve both hot
ductility and machinability. Here, the "solid-solute N" is the
total amount of N minus the amount of compound N. The "amount of
compound N" substantially shows the amount of N forming BN. This
solid-solute N is produced in large amounts since the BN becomes
solid solute by heating in the rolling temperature range of 800 to
1100.degree. C. For good rolling with little occurrence of surface
defects, it is necessary to reduce the amount of solid-solute N in
this temperature range.
[0015] Further, the inventors discovered that to improve the yield
of Mn, which is easily consumed as an oxide in the molten steel, as
MnS and the yield of B as BN so as to improve the machinability and
hot ductility and to improve the machinability and suppress the
melt loss of plate refractories of the continuous casting sliding
nozzles, it is necessary to reduce the amount of production of MnO
in the steel.
[0016] The present invention was made based on the above discovery
and has as its gist the following:
[0017] (1) Machining steel superior in manufacturability
containing, by mass %, [0018] C: 0.005 to 0.2% [0019] Si: 0.001 to
0.5% [0020] Mn: 0.3 to 3.0% [0021] P: 0.001 to 0.2% [0022] S: 0.30
to 0.60% [0023] B: 0.0003 to 0.015% [0024] O: 0.005 to 0.012%
[0025] Ca: 0.0001 to 0.0010%, and [0026] Al.ltoreq.0.01%, [0027]
having an N content satisfying [0028] N.gtoreq.0.0020% and
1.3.times.B-0.0100.ltoreq.N.ltoreq.1.3.times.B+0.0034, and [0029]
having a balance of Fe and unavoidable impurities, wherein [0030]
further, regarding the MnO in the steel, in a cross-section of the
steel material perpendicular to the rolling direction, the area of
MnO of a circle equivalent diameter of 0.5 .mu.m or more being 15%
or less of the area of the total Mn-based inclusions.
[0031] (2) Machining steel superior in manufacturability as set
forth in (1), wherein, regarding the sulfides mainly comprised of
MnS, in a cross-section of the steel material perpendicular to the
rolling direction, a density of sulfides of a circle equivalent
diameter of 0.1 to 0.5 .mu.m is 10000/mm.sup.2 or more.
[0032] (3) Machining steel superior in manufacturability as set
forth in any one of (1) to (5), further containing, by mass %, one
or more of [0033] V: 0.05 to 1.0% [0034] Nb: 0.005 to 0.2% [0035]
Cr: 0.01 to 2.0% [0036] Mo: 0.05 to 1.0% [0037] W: 0.05 to 1.0%
[0038] Ni: 0.05 to 2.0% [0039] Cu: 0.01 to 2.0% [0040] Sn: 0.005 to
2.0% [0041] Zn: 0.0005 to 0.5% [0042] Ti: 0.0005 to 0.1% [0043] Zr:
0.0005 to 0.1% [0044] Mg: 0.0003 to 0.005% [0045] Te: 0.0003 to
0.2% [0046] Bi: 0.005 to 0.5% [0047] Pb: 0.005 to 0.5%.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] FIG. 1 gives conceptual views showing a plunge cutting test
method, in which (a) is a bird's eye view and (b) is a plan
view.
[0049] FIG. 2 gives conceptual views showing a longitudinal turning
test method and the quality of the finished surface roughness, in
which (a) is a plan view and (b) is an enlarged view of a finished
surface (feed marks).
[0050] FIG. 3 is an optical micrograph showing an example of
measurement of MnO by EPMA.
[0051] FIG. 4 gives an (a) TEM replica photograph and (b) optical
micrograph of sulfides mainly comprised of MnS of an example of the
present invention.
[0052] FIG. 5 gives an (a) TEM replica photograph and (b) optical
micrograph of sulfides mainly comprised of MnS of a comparative
example of the present invention.
[0053] FIG. 6 is a view showing changes in machinability due to MnO
by the finished surface roughness by longitudinal turning after
machining 800 pieces.
[0054] FIG. 7 is a view showing a balance of finished surface
roughness by longitudinal turning and hot ductility in invention
examples and comparative examples.
[0055] FIG. 8 is an explanatory view of a depth position of 1/4 of
a cast slab thickness.
BEST MODE FOR CARRYING OUT THE INVENTION
[0056] The present invention provides low carbon machining steel in
which machinability is required more than strength characteristics,
which improves the machinability, without adding Pb, by adding B
and making it precipitate as BN, wherein, regarding the composition
of ingredients of the steel, in particular B and N are added so as
to satisfy a suitable relationship to thereby improve the
machinability and the ductility at the time of hot rolling and
wherein MnO in the steel is reduced so as to improve the
machinability and the lifetime of the refractories for control of
the amount of injection in continuous casting, whereby the
invention is completed. Furthermore, the present invention finely
disperses MnS-based inclusions in the steel to improve the
machinability. Below, the composition of ingredients prescribed in
the present invention and the reasons for limitation will be
explained.
[0057] [C] 0.005 to 0.2%
[0058] C is related to the basic strength of the steel material and
the amount of oxygen in the steel, so has a large effect on the
machinability. If adding a large amount of C to improve the
strength, the machinability is reduced, so the upper limit was made
0.2%. On the other hand, if simply using blow refining and overly
reducing the amount of C, not only will the costs swell, but also
the oxygen will no longer be removed by the C, so a large amount of
oxygen will remain in the steel and will cause pinholes and other
problems. Therefore, an amount of C of 0.005% able to easily
prevent pinholes and other problems was made the lower limit.
[0059] [Si] 0.001 to 0.5%
[0060] Excessive addition of Si forms hard oxides which lower the
machinability, but suitable addition softens the oxides and does
not cause a drop in the machinability. The upper limit is 0.5%.
Above that, hard oxides form. If less than 0.001%, softening of the
oxides becomes difficult and the cost swells industrially.
[0061] [Mn] 0.3 to 3.0%
[0062] Mn is required for fixing and dispersing the sulfur in the
steel as MnS. Further, it is necessary for softening the oxides in
the steel and rendering the oxides harmless. The effect depends on
the amount of S added, but if less than 0.3%, the added S is
sufficiently fixed as MnS leading to surface defects and S becomes
FeS leading to embrittlement. If the amount of Mn becomes large,
the hardness of the material also becomes greater and the
machinability and cold workability fall, so 3.0% was made the upper
limit.
[0063] [P] 0.001 to 0.2%
[0064] P causes a greater hardness of the material in the steel.
Not only the cold workability, but also the hot workability and
casting properties fall, so the upper limit has to be made 0.2%. On
the other hand, this is an element effective for improvement of the
machinability, so the lower limit was made 0.001%.
[0065] [S] 0.30 to 0.60%
[0066] S bonds with Mn and is present as sulfides mainly comprised
of MnS. Sulfides mainly comprised of MnS improve the machinability,
while sulfides mainly comprised of flattened MnS constitute one
cause of anisotropy at the time of forging. Large sulfides mainly
comprised of MnS should be avoided, but from the viewpoint of the
improvement of the machinability, addition of a large amount is
preferable. Therefore, causing sulfides mainly comprised of MnS to
finely disperse is preferable. For improvement of the machinability
when not adding Pb, addition of 0.30% or more is necessary. On the
other hand, if the amount of addition of S is too great, not only
is formation of coarse sulfides mainly comprised of MnS
unavoidable, but also cracks occur during the manufacture due to
the casting property due to FeS etc., the deterioration of the
deformation characteristics, etc. For this reason, the upper limit
was made 0.60%.
[0067] [B] 0.0003 to 0.015%
[0068] If B precipitates as BN, there is an effect of improvement
of the machinability. In particular, by coprecipitating with
sulfides mainly comprised of MnS and finely dispersing in the
matrix, the effect becomes more remarkable. These effects are not
remarkable if less than 0.0003%, while if added over 0.015%, the
reaction with the refractories in the molten steel becomes severer
and the melt loss of the refractories at the time of casting
becomes greater and the manufacturability is remarkably impaired.
Therefore, the range was made 0.0003% to 0.015%.
[0069] B easily forms oxides, so if the dissolved O in the molten
steel is high, it ends up being consumed as oxides and the amount
of BN effective for improvement of the machinability is sometimes
reduced. Adding Ca to lower the dissolved oxygen (free oxygen) to a
certain extent, then adding B to improve the yield of the amount of
B substantially becoming BN is effective for improving the
machinability.
[0070] [O] 0.005 to 0.012%
[0071] When O does not form oxides, but remains alone, it forms
bubbles at the time of cooling and causes pinholes. Sometimes it
forms hard oxides causing deterioration of the machinability or
defects, so control is necessary. Furthermore, it ends up consuming
the Mn and B added for improving the machinability as oxides in the
molten steel and thereby reduces the Mn becoming MnS and B becoming
BN to have an effect on the machinability. If less than 0.005%,
sulfides mainly comprised of MnS of a form called Type II of Sims
are formed and thereby the machinability is degraded. Furthermore,
a desulfurization reaction easily occurs in the molten steel and
stable addition of S no longer becomes possible. Therefore, 0.005%
was made the lower limit. If the amount of O exceeds 0.012%, oxides
of Mn and B easily form in the molten steel and the Mn becoming MnS
and B becoming BN are de facto reduced whereby the machinability is
degraded. Furthermore, a large amount of hard oxides are formed and
the amount of damage is increased. Furthermore, the melt loss of
the refractories also becomes greater. Therefore, 0.012% was made
the upper limit. For the control of O, addition of Ca is
essential.
[0072] [Ca] 0.0001 to 0.0010%
[0073] Ca is a deoxidizing element. It can control the amount of
dissolved oxygen (free oxygen) in the steel material, stabilizes
the yields of the easily oxide forming Mn and B, and furthermore
can suppress the formation of hard oxides. Further, if slight in
amount, it forms soft oxides and acts to improve the machinability.
If less than 0.0001%, this effect is nonexistent, while if over
0.0010%, a large amount of soft oxides are formed and deposit on
the tool cutting edges as relief shapes, so the finished surface
roughness becomes extremely bad. Not only this, but also a large
amount of hard oxides are produced. Furthermore, the machinability
and the hot ductility are lowered. Therefore, the range of the
ingredient was defined as 0.0001 to 0.0010%.
[0074] [Al] Al.ltoreq.0.01%
[0075] Al is a deoxidizing element and forms Al.sub.2O.sub.3 or AIN
in the steel. However, Al.sub.2O.sub.3 is hard, so becomes a cause
of tool damage and promotes wear at the time of machining. Further,
by forming AIN, the amount of N for forming BN ends up being
reduced and the machinability falls. Therefore, the amount was made
0.01% or less where Al.sub.2O.sub.3 and AIN are not produced in
large amounts.
[0076] [N Contained Satisfying N.gtoreq.0.0020% and
1.3.times.B-0.0100.ltoreq.N.ltoreq.1.3.times.B+0.0034]
[0077] N bonds with B to form BN which improves the machinability.
BN forms inclusions improving the machinability. By finely
dispersing them in a high density, the machinability is remarkably
improved. B and N bond exactly by a stoichiometric ratio, by mass
ratio, of B:N=10.8:14 (=1:1.3) whereby BN is formed. BN has
solubility with respect to steel. Along with a rise in the steel
temperature, its solubility becomes greater and the amount of
solid-solute N increases. If the amount of N becoming solid solute
in the rolling temperature range (800 to 1100.degree. C.) is great,
this will become a cause of rolling defects, so it is necessary to
limit the amount of solid-solute N to a certain amount or less. It
is necessary to control the amount of N added to the steel material
in accordance with the amount of addition of B. Therefore, if
exceeding the amount of N bonding exactly with B (1.3.times.B) by
+0.0034%, the occurrence of rolling defects becomes remarkable, so
the upper limit of the amount of N was made 1.3.times.B+0.0034. On
the other hand, if the amount of N added becomes too small, the
amount of formation of BN is reduced. If less than the amount of N
bonding exactly with B (1.3.times.B) by -0.0100%, the amount of BN
necessary for improvement of the machinability cannot be obtained,
so the lower limit of the amount of N with respect to the amount of
B was made 1.3.times.B-0.0100 or more. Further, if the amount of N
is less than 0.0020%, the absolute amount of N becomes insufficient
and the distance of dispersion to places where B is present in the
steel becomes greater, so even with an amount of addition of N of
the stoichiometric ratio, sufficient BN cannot be produced. For
this reason, it is necessary to secure 0.0020% or more. Due to the
above, to achieve both manufacturability and machinability, it is
necessary that the N content satisfy N.gtoreq.0.0020% and
1.3.times.B-0.0100.ltoreq.N.ltoreq.1.3.times.B+0.0034.
[0078] [MnO] Area of MnO of Circle Equivalent Diameter of 0.5 .mu.m
or More Not More Than 15% of Area of Total Mn-Based Inclusions
[0079] Mn is an element strong in affinity with oxygen. Formation
of MnO becomes unavoidable in the presence of a certain amount of
dissolved oxygen (free oxygen) in the molten steel. MnO is an
inclusion with relatively low melting point and softness. It itself
does not cause remarkable deterioration of the tool life and other
aspects of machinability like a hard inclusion such as
Al.sub.2O.sub.3. However, if the MnO increases, the amount of Mn
forming MnS is reduced and the fine dispersion of the MnS is
obstructed, so the machinability deteriorates. Furthermore, in an
environment where a large amount of MnO is produced, the dissolved
oxygen (free oxygen) in the molten steel becomes a high
concentration. Therefore, the amount of formation of B oxides also
increases, the amount of B forming BN is reduced, and the
machinability is further degraded. Further, if the Mn forming MnS
is reduced, it is no longer possible to fix the S at a high
temperature, so a large number of FeS particles are formed and
therefore the hot ductility is degraded.
[0080] Furthermore, due to the MnO in the molten steel, the melt
loss of the plate refractories of the continuous casting sliding
nozzles becomes severer and the manufacturability is remarkably
degraded. If the area of the MnO in the steel having a circle
equivalent diameter of 0.5 .mu.m or more in the cross-section of
the steel material perpendicular to the rolling direction is over
15% of the area of the total Mn-based inclusions, the deterioration
of the machinability and manufacturability becomes remarkable, so
to obtain good machinability and manufacturability, it is necessary
that the MnO in the steel be not more than 15% of the total
Mn-based inclusions.
[0081] If MnO is, by circle equivalent diameter, 0.5 .mu.m or less,
its area rate is extremely small, therefore the amount of Mn
consumed by the MnO is also slight, so the amount of production of
MnS is not greatly affected. For this reason, it is defined as
having a circle equivalent diameter of 0.5 .mu.m or more.
[0082] Here, the identification of the MnO referred to in the
present invention and the method of measurement of the area will be
explained.
[0083] MnO is usually present as MnO alone and is also sometimes
present bonded with other oxides, but in the present invention,
what is measured by the following method is identified as the "MnO"
and its area is found.
[0084] An example of measurement of the MnO by EPMA is shown in
FIG. 3. A test piece cut out from a position of the steel material
at a depth of 1/4 of the diameter of the cross-section
perpendicular to the rolling direction, buried in resin, and
polished was measured by an electron probe microanalyzer (EPMA) for
at least 20 fields, each field being 200 .mu.m.times.200 .mu.m. The
MnO's 13 in the steel of the steel material are present in a state
contained in sulfides mainly comprised of MnS 14, so in elemental
area analysis by EPMA, the parts where Mn and O overlap are deemed
MnO and that area is found.
[0085] The "total Mn-based inclusions" is the general term for all
of the inclusions combined with Mn in the steel. This covers the
later explained sulfides mainly comprised of MnS, oxides of MnO
alone, and oxides of MnO bonded with other oxides. The total
Mn-based inclusions can also be identified by elemental area
analysis by EPMA and their area measured, so the ratio of the area
of the MnO measured with respect to the area of the total Mn-based
inclusions measured is found.
[0086] To reduce the amount of formation of MnO, it is possible to
reduce the concentration of dissolved oxygen (free oxygen) in the
molten steel before LF. It is preferable to make the dissolved
oxygen (free oxygen) concentration 200 ppm or less. However, if
overly reducing it, a desulfurization reaction proceeds between the
metal/slag and securing the S in the steel for maintaining the
machinability becomes difficult, so sufficient care is required.
Making this 150 ppm or more is preferable. As the method for
control of the dissolved oxygen (free oxygen), advance
desulfurization before LF treatment is effective. For control of
the free oxygen, addition of Ca is essential, but in addition
adding Si, Al, Ti, Zr, Mg, etc. alone or in combination is also
effective.
[0087] [Dispersion of Sulfides Mainly Comprised of MnS]
[0088] Density of sulfides of circle equivalent diameter of 0.1 to
0.5 .mu.m of 10000/mm.sup.2 or more
[0089] Sulfides mainly comprised of MnS are inclusions for
improving the machinability. By finely dispersing them at a high
density, the machinability is remarkably improved. In particular,
in the case of a machining method like longitudinal turning which
proceeds while forming peaks called "feed marks" at the finished
surface, the presence of surface relief has a great effect on the
height of the peaks, that is, the finished surface roughness, but
sulfides mainly comprised of MnS dispersed finely at a high density
make the steel material uniform and thereby can improve the
breaking characteristics of the steel material, reduce the surface
relief, and improve the finished surface roughness. This is more
effective for improvement of the finished surface roughness of
parts such as shafts of office automation equipment machined by
longitudinal turning. To obtain this effect, a density of
10000/mm.sup.2 or more is necessary. The dimensions have to be a
circle equivalent diameter of 0.1 to 0.5 .mu.m. Usually, the
distribution of sulfides mainly comprised of MnS is observed under
an optical microscope to measure the dimensions and density.
Sulfides mainly comprised of MnS of these dimensions cannot be
confirmed by observation by an optical microscope and can only
first be observed by a transmission electron microscope (TEM).
Sulfides mainly comprised of MnS are of dimensions where even if
there is no difference in dimensions and density in observation
under an optical microscope, clear differences are observed by
observation under a TEM. In the present invention, this is
controlled and the state of presence is converted into a numerical
value so as to differentiate the invention from the prior art. To
ensure the presence of sulfides mainly comprised of MnS over these
dimensions by a density of 10000/mm.sup.2 or more, addition of a
large amount of S over the claims is considered necessary, but if
adding this in a large amount, the probability rises of coarse
sulfides mainly comprised of MnS also ending up present in large
numbers and defects occurring more at the time of hot rolling. With
the amount of addition of S of the claims, if sulfides mainly
comprised of MnS exceed these dimensions, the amount of sulfides
mainly comprised of MnS will become insufficient and the density
required for improving the finished surface roughness will no
longer be able to be maintained. Further, sulfides of less than the
minimum diameter of 0.1 .mu.m do not substantially affect the
machinability. Therefore, the density of sulfides mainly comprised
of MnS having a circle equivalent diameter of 0.1 to 0.5 .mu.m was
made 10000/mm.sup.2. The sulfides mainly comprised of MnS form
nuclei for precipitation of the Bn which is hard to make uniformly
finely disperse in the matrix, whereby the BN can be made to
uniformly finely disperse and the effect of improvement of the
machinability, in particular the finished surface roughness, by BN
can be made more remarkable.
[0090] Note that the "sulfides mainly comprised of MnS" include not
only pure MnS, but also include inclusions of sulfides of Fe, Ca,
Ti, Zr, Mg, REM, etc. solid solute with MnS or bonded together for
copresence, inclusions such as MnTe where elements other than S
form compounds with Mn to become solid solute or bond with MnS for
copresence, the above inclusions precipitated with oxides as their
nuclei, that is, inclusions able to be expressed by the chemical
formula (Mn,X)(S,Y) (where X: sulfide forming elements other than
Mn and Y: elements bonding with Mn other than S). This is the
general term for Mn sulfide-based inclusions.
[0091] To obtain dimensions and a density of sulfides mainly
comprised of MnS, it is more effective if the ratio Mn/S of the Mn
and S contained is made 1.2 to 2.8.
[0092] Furthermore, to effectively produce fine sulfides mainly
comprised of MnS, it is sufficient to control the range of the
solidification and cooling rate. If the cooling rate is less than
10.degree. C./min, the solidification becomes too slow and the
precipitated sulfides mainly comprised of MnS end up becoming
coarser and fine dispersion becomes difficult, while if the cooling
rate is more than 100.degree. C./min, the density of the produced
fine sulfides mainly comprised of MnS becomes saturated, the
hardness of the steel slab rises, and the danger of cracking
increases. Therefore, the cooling rate at the time of casting
should be 10 to 100.degree. C./min. This cooling rate can be easily
obtained by controlling the size of the casting mold cross-section,
the casting speed, etc. to suitable values. This can be applied to
both continuous casting and ingot making.
[0093] The "solidification and cooling rate" referred to here, as
shown in FIG. 8, means the speed at the time of cooling from the
liquidus temperature to the solidus temperature at the depth
position 18 (see FIG. 8(b)) of 1/4 the thickness (L) of the cast
slab in the horizontal cross-section 17 of the cast slab 16
produced by the casting direction 15 shown by the arrow. The
cooling rate is found from the distance between the secondary
dendrite arms of the solidified structure in the thickness
direction of the cast slab after solidification by calculation by
the following formula:
Rc = ( .lamda.2 770 ) - 1 0.41 ##EQU00001##
[0094] where, Rc: cooling rate (.degree. C./min), .lamda.2:
distance between secondary dendrite arms 2 (.mu.m)
[0095] That is, the distance between secondary dendrite arms
changes according to the cooling conditions, so this was measured
to confirm the controlled cooling rate.
[0096] Next, the reasons for defining the freely added optional
elements will be explained.
[0097] [Steel Strengthening Elements]
[0098] [V] 0.05 to 1.0%
[0099] V forms carbonitrides which can strengthen the steel by
secondary precipitation hardening. If less than 0.05%, there is no
effect on strengthening, while if added over 1.0%, a large amount
of carbonitrides precipitate and conversely the mechanical
properties are impaired, so this was made the upper limit.
[0100] [Nb] 0.005 to 0.2%
[0101] Nb also forms carbonitrides which can strengthen the steel
by secondary precipitation hardening. If less than 0.005%, there is
no effect on strengthening, while if added over 0.2%, a large
amount of carbonitrides precipitate and conversely the mechanical
properties are impaired, so this was made the upper limit.
[0102] [Cr] 0.01 to 2.0%
[0103] Cr is an element improving the hardenability and imparting
resistance to tempering softening. Therefore, it is added to steel
requiring higher strength. In that case, addition of 0.01% or more
is required. However, if adding a large amount, Cr carbides form
and cause embrittlement, so 2.0% was made the upper limit.
[0104] [Mo] 0.05 to 1.0%
[0105] Mo is an element imparting resistance to tempering softening
and improving the hardenability. If less than 0.05%, the effect is
not recognized, while even if added over 1.0%, the effect becomes
saturated, so 0.05% to 1.0% was made the range of addition.
[0106] [W] 0.05 to 1.0%
[0107] W forms carbonitrides which can strengthen the steel by
secondary precipitation hardening. If less than 0.05%, there is no
effect on strengthening, while if added over 1.0%, a large amount
of carbonitrides precipitate and conversely the mechanical
properties are impaired, so this was made the upper limit.
[0108] [Ni] 0.05 to 2.0%
[0109] Ni strengthens the ferrite, improves the ductility, and is
also effective for improving the hardenability and improving the
corrosion resistance. If less than 0.05%, that effect is not
recognized, while even if added over 2.0%, the effect becomes
saturated in terms of the mechanical properties, so this was made
the upper limit.
[0110] [Cu] 0.01 to 2.0%
[0111] Cu strengthens the ferrite and is effective for improving
the hardenability and improving the corrosion resistance. If less
than 0.01%, the effect is not recognized, while even if added over
2.0%, the effect becomes saturated in respect to the mechanical
properties, so this was made the upper limit. In particular, the
hot ductility is reduced. This easily becomes a cause of defects at
the time of rolling. Therefore, addition simultaneously with Ni is
preferable.
[0112] [Machinability Improving Elements Using Embrittlement]
[0113] [Sn] 0.005 to 2.0%
[0114] Sn makes the ferrite brittle, extends tool life, and
improves the surface roughness as an effect. If less than 0.005%,
this effect is not recognized, while even if added over 2.0%, the
effect becomes saturated, so this was made the upper limit.
[0115] [Zn] 0.0005 to 0.5%
[0116] Zn makes the ferrite brittle, extends tool life, and
improves the surface roughness as an effect. If less than 0.0005%,
this effect is not recognized, while even if added over 0.5%, the
effect becomes saturated, so this was made the upper limit.
[0117] [Machinability Improving Elements Using Adjustment of
Deoxidation]
[0118] [Ti] 0.0005 to 0.1%
[0119] Ti is a deoxidizing element which can control the amount of
oxygen in the steel and can stabilize the yields of the easily
oxide forming Mn and B. Further, if slight in amount, it forms soft
oxides and acts to improve the machinability. If less than 0.0005%,
this effect is nonexistent, while if over 0.1%, a large amount of
hard oxides are formed and the Ti becoming solid solute without
forming oxides bonds with N to form hard TiN which lowers the
machinability. Therefore, the range of the ingredient was made
0.0005 to 0.1%. Ti forms TiN and thereby consumes the N required
for forming BN. Therefore, the amount of addition of Ti is
preferably 0.01% or less.
[0120] [Zr] 0.0005 to 0.1%
[0121] Zr is a deoxidizing element which can control the amount of
oxygen in the steel and can stabilize the yields of the easily
oxide forming Mn and B. Further, if slight in amount, it forms soft
oxides and acts to improve the machinability. If less than 0.0005%,
this effect is nonexistent, while if over 0.1%, a large amount of
soft oxides are formed and deposit on the tool cutting edges as
relief shapes, so the finished surface roughness becomes extremely
bad. Not only this, but also a large amount of hard oxides are
produced. Furthermore, the machinability is lowered. Therefore, the
range of the ingredient was defined as 0.0005 to 0.1%.
[0122] [Mg] 0.0003 to 0.005%
[0123] Mg is a deoxidizing element which can control the amount of
oxygen in the steel. It can stabilize the yields of easily oxide
forming Mn and B. Further, if slight in amount, it forms soft
oxides and acts to improve the machinability. If less than 0.0003%,
this effect is nonexistent, while if over 0.005%, a large amount of
soft oxides are formed and deposit on the tool cutting edges as
relief shapes, so the finished surface roughness becomes extremely
bad. Not only this, but also a large amount of hard oxides are
produced. Furthermore, the machinability is lowered. Therefore, the
range of the ingredient was defined as 0.0003 to 0.005%.
[0124] [Machinability Improving Elements Using Control of Sulfide
Form and Lubrication Between Tool and Steel Material]
[0125] [Te] Te: 0.0003 to 0.2%
[0126] Te is a machinability improving element. Further, it forms
MnTe and, by copresence with MnS, lowers the deformability of MnS
to control the flattening of the MnS shapes. Therefore, this
element is effective for reducing anisotropy. This effect is not
recognized if less than 0.0003%, while even if added over 0.2%, not
only does the effect become saturated, but also the hot ductility
falls and defects are easily caused.
[0127] [Bi] 0.005 to 0.5%
[0128] Bi is a machinability improving element. Its effect is not
recognized if less than 0.005%, while even if added over 0.5%, not
only does the effect of improvement of the machinability become
saturated, but also the hot ductility falls and defects are easily
caused.
[0129] [Pb] 0.005 to 0.5%
[0130] Pb is a machinability improving element. Its effect is not
recognized if less than 0.005%, while even if added over 0.5%, not
only does the effect of improvement of the machinability become
saturated, but also the hot ductility falls and defects are easily
caused.
EXAMPLES
[0131] The effects of the present invention will be explained next
using examples. Steels of the invention examples of Examples 1 to
72 shown in Tables 1 to 4 were produced in a 270 t converter, then
cast by a solidification and cooling rate of 4 to 18.degree.
C./min. The casting was classified so that, among these, the
solidification and cooling rates of the steel types of claim 1 of
Examples 1 to 8 and the steel types of claim 6 of Examples 62 to 72
were 1 to 7.degree. C./min, while the solidification and cooling
rates of the steel types of claims 2 to 6 of Examples 9 to 61 were
12 to 85.degree. C./min. The steels of the comparative examples of
Examples 73 to 102 shown in Tables 5 to 6 were produced in a 270 t
converter, then cast by a solidification and cooling rate of 4 to
7.degree. C./min. In both the invention examples and the
comparative examples, the 270 t converter material was bloomed to a
billet, then rolled to .phi.9.5. This .phi.9.5 mm rolled material
was drawn to .phi.8 mm and used as the test material. For
evaluation of the hot ductility, before the rolling, test pieces
were taken from the billet and a 180 mm square cast material.
Further, the solidification and cooling rate were adjusted by
control of the size of the casting mold cross-section and casting
speed.
[0132] The machinability of the material was evaluated by three
typical types of machining methods of a drilling test showing the
conditions in Table 7, a plunge cutting test showing the conditions
in Table 8, and a longitudinal turning test showing the conditions
in Table 9. The drilling test is the method of evaluating the
machinability by the highest cutting speed enabling machining up to
a cumulative hole depth of 1000 mm, (so-called VL1000, unit:
m/min). The plunge cutting test is the method of evaluating the
finished surface roughness by transferring the tool shape by a
piercing tool of high speed steel (builtup cutting edge shape). A
summary of this test method is shown in FIG. 1. In the test, the
finished surface roughness when cutting 200 grooves was measured by
a contact type roughness meter. This was used as an indicator
showing the finished surface roughness of the 10 point surface
roughness Rz (unit: .mu.m). The longitudinal turning test is a
machining method cutting into the outer circumference of the steel
material of the test piece 2 in the machining direction 3 while
feeding the carbide tool 1 in the longitudinal direction. In the
same way as plunge cutting, this method repeatedly measures and
evaluates the finished surface roughness of the measurement surface
4 of surface roughness in transfer of the tool shape. A summary of
this test method is shown in FIG. 2. This method performs the test
while rotating the test piece 2, feeding the carbide tool 1 along
the test piece 2 (0.05 mm/rev), and machining by a predetermined
depth of cut 6 (1 mm). It is advanced while forming peaks called
"feed marks 5" on the finished surface 7 to form a surface
roughness measurement plane 8. The presence of any deterioration 9
of the relief shapes forms peak heights which becomes the roughness
of the surface relief surface (theoretical roughness+surface
relief) 10. That is, this becomes the finished surface roughness
and has a great effect on the good surface roughness (theoretical
roughness) 11 (see FIG. 2(b)). If there is no surface relief, the
value becomes close to the theoretical roughness, but if surface
relief occurs, the roughness is degraded by that amount. Sulfides
mainly comprised of MnS finely dispersed at a high density make the
steel material uniform and thereby reduce the surface relief and
enable a good finished surface roughness, so it is possible to
express the effect of the sulfides mainly comprised of MnS
dispersed at a high density remarkably well. Further, this method
can express the quality of the finished surface roughness resulting
from the transfer of tool surface relief due to tool wear after a
large amount of machining remarkably well, so in this test, the
evaluation was performed using the finished surface roughness after
machining 800 pieces--which enables evaluation of the difference of
machinability in the state where tool wear has progressed. The
finished surface roughness was measured by a contact type roughness
meter. The 10-point surface roughness Rz (unit: .mu.m) was used as
an indicator showing the finished surface roughness. For chip
evacuation, examples where the radius at the time of chip curling
is small or examples where the chips break off are preferable and
were evaluated as "G (good)". Examples where the number of curls is
large and the radius of curvature is small or examples where the
chip lengths do not reach 100 mm are good and were evaluated as
"G". Chips with a radius of curvature of over 20 mm, curling
continuously by three curls or more, and extending long are poor
and were evaluated as "P".
[0133] For the MnO in the steel material, the area rate of MnO of a
circle equivalent diameter of 0.5 .mu.m or more in the
cross-section perpendicular to the rolling direction of the steel
material was measured by an electron probe microanalyzer (EPMA)
using a test piece cut out from a depth position of 1/4 of the
diameter of the cross-section perpendicular to the rolling and
drawing direction after .phi.8 mm drawing, buried in resin, and
polished. The measurement was performed for 20 fields or more each
of 200 .mu.m.times.200 .mu.m. The area rate was found using the
area of MnO in the inclusions measured by the elemental area
analysis as a ratio with respect to the area of the total Mn-based
inclusions. The MnO in the steel material is present in a state
contained in MnS, so in analysis by EPMA, the area where Mn and O
overlap is deemed the area of MnO as differentiated from MnS. The
Mn and O were overlaid by image processing. An example of
measurement by EPMA is shown in FIG. 3.
[0134] The density of sulfides mainly comprised of MnS of
dimensions of a circle equivalent diameter of a maximum diameter of
0.5 .mu.m and a minimum diameter of 0.1 .mu.m was measured by a
transmission electron microscope using a test piece obtained by the
extract replica method from a position of a depth of 1/4 the
diameter of the cross-section perpendicular to the rolling and
drawing direction after .phi.8 mm drawing. The measurement was
performed at 10000 power for 40 fields or more, each field of 80
.mu.m.sup.2. The result was converted to the number of sulfides
mainly comprised of MnS per mm.sup.2.
[0135] The hot ductility was evaluated by the value of the
reduction rate in a high temperature tensile test at 1000.degree.
C. If the reduction rate is 50% or more, good rolling is possible,
but if less than 80%, numerous surface defects are formed, the area
for removal of defects and touchup after rolling becomes greater,
and use is not possible for high grade products with severe demands
on surface properties. If a value of the reduction rate of 80% or
more can be obtained, the formation of surface defects is
remarkably reduced, use even without touchup becomes possible, and
use for high grade products becomes possible. Furthermore, the
touchup costs can also be slashed. Therefore, a reduction rate of
80% or more was evaluated as a "G (good)" hot ductility, while one
of less than 80% was evaluated as "P (poor)".
[0136] The state of melt loss of the plate refractories of
continuous casting sliding nozzles was evaluated using MgO--C
(MgO=87%, Al.sub.2O.sub.3=10%, C=3%) as the material of the sliding
nozzle plates. The melt loss rate is a value indexing the melt loss
rates to the melt loss rate of refractories when the area of MnO of
0.5 .mu.m or more size constitutes 15% of the total area of
Mn-based inclusions as "1". If the melt loss rate exceeds 1, the
melt loss of the refractories becomes worse, so a melt loss rate of
1 or less was evaluated as "G (good)" and one over 1 was evaluated
as "P (poor)". The invention examples of Examples 1 to 72 were all
better than the comparative examples of Examples 73 to 102 in drill
tool life and finished surface roughness in plunge cutting and
longitudinal turning, had a hot ductility of a value of 80% or
more, and enabled good manufacturability with a low melt loss rate.
For example, it was possible to control the amount of N by balanced
amounts of addition of B and N like in the invention examples of
Examples 1 to 8 and possible to obtain a high value of hot
ductility and a low melt loss rate without deterioration of the
machinability when the MnO area rate is low by control of the
amount of O by addition of Ca. Further, it was possible to obtain
an extremely good machinability by balanced amounts of addition of
B and N and a low MnO area rate. When the density of fine sulfides
mainly comprised of MnS satisfies claim 2 like in Examples 9 to 18
and 56 to 59, the value of the finished surface roughness, in
particular the value at the time of longitudinal turning, becomes
even better. Even in the examples of addition of the freely added
optional elements of claims 3 to 6 of Examples 19 to 55 and 60 to
72, it is learned that a good finished surface roughness and
manufacturability are obtained. Among these, in Examples 47, 52,
60, and 62 to 67 to which a slight amount of Pb, known as a free
cutting element, is added, in Examples 45, 48, 50, 53, 61, 68, and
69 to which a slight amount of Te, also known as a free cutting
element, is added, and furthermore in Examples 55 and 70 to 72 to
which both Pb and Te are added, it is learned that good hot
ductility and machinability are obtained.
[0137] As opposed to this, the comparative examples were all cast
by a slow solidification cooling rate, so the density of fine
sulfides mainly comprised of MnS becomes smaller and, overall, poor
values of machinability, in particular the finished surface
roughness by longitudinal turning, are shown. Compared with the
invention examples of claim 1 of Examples 1 to 8 produced by the
same level of small solidification and cooling rate, poor values
are exhibited since the chemical ingredients are outside the ranges
of the present invention. For example, when the area rate of MnO is
high like in the comparative example of Example 76, the reduction
in the amount of MnS and the amount of BN results in a poor value
of finished surface roughness. The melt loss rate becomes a large
value. In the comparative example of Example 80, the MnO area rate
of 15% or less is satisfied, but the amounts of S and Ca are
outside the invention ranges, so the hot ductility becomes a poor
value. When Ca is not added like in the comparative example of
Example 81, the O cannot be control and the large numbers of MnO
and hard oxides formed result in poor manufacturability of a hot
ductility of less than 80% and a large value of melt loss rate.
Furthermore, Examples 90 and 91 are comparative examples with
amounts of N below the lower limit. The increase of solid-solute B
invites an increase in hardness and a low value of hot ductility is
exhibited. Further, Example 93 is a comparative example with
amounts of S and N above the upper limits. Due to the increase in
solid-solute N, a poor value of hot ductility is exhibited. Example
102 is a comparative example with a high MnO. Poor values of both
the finished surface roughness and melt loss index are
exhibited.
[0138] FIG. 4 gives an (a) TEM replica photograph and (b) optical
micrograph of sulfides mainly comprised of MnS of an example of the
present invention. FIG. 5 gives an (a) TEM replica photograph and
(b) optical micrograph of sulfides mainly comprised of MnS of a
comparative example of the present invention. In this way, in the
invention examples and the comparative examples, with (b)
observation by an optical microscope, there is no large difference
in the dimensions and density of the sulfides mainly comprised of
MnS, but with (a) observation by a TEM replica, clear differences
are seen in both the dimensions and density.
[0139] FIG. 6 shows changes in machinability due to the MnO area
rate using as an example the finished surface roughness by
longitudinal turning after machining 800 pieces. Tool wear
remarkably progresses at the time of a large amount of machining
when the MnO area rate is greater than 15%, so the difference in
finished surface roughness, which is governed by the transfer of
surface relief due to tool wear, appears remarkably at this as the
borderline.
[0140] FIG. 7 is a view showing a balance of finished surface
roughness by longitudinal turning and hot ductility in invention
examples and comparative examples. The invention examples are good
in finished surface roughness and have a hot ductility of a good
region of 80% or more. In the comparative examples, the finished
surface roughness and the hot ductility are both in the poor range
or even if the hot ductility is good, the finished surface
roughness is poor.
[0141] Due to this, it is learned that the invention examples,
which are balanced in amount of B and amount of N and where the
amount of MnO can be controlled, the manufacturability and
machinability are both good.
TABLE-US-00001 TABLE 1 Chemical ingredients (mass %) Ex. Class C Si
Mn P S B O Ca Al V Nb 1 Inv. ex. 0.059 0.002 1.38 0.035 0.58 0.0075
0.0088 0.0006 0.002 2 Inv. ex. 0.071 0.008 1.52 0.093 0.45 0.0101
0.0091 0.0003 0.002 3 Inv. ex. 0.050 0.009 1.32 0.070 0.41 0.0085
0.0119 0.0005 0.001 4 Inv. ex. 0.125 0.003 1.46 0.045 0.41 0.0110
0.0088 0.0006 0.003 5 Inv. ex. 0.082 0.005 1.36 0.057 0.41 0.0148
0.0106 0.0004 0.003 6 Inv. ex. 0.060 0.004 1.54 0.124 0.42 0.0129
0.0094 0.0005 0.001 7 Inv. ex. 0.090 0.003 1.59 0.099 0.30 0.0003
0.0084 0.0004 0.001 8 Inv. ex. 0.062 0.002 1.48 0.106 0.41 0.0067
0.0091 0.0003 0.001 9 Inv. ex. 0.073 0.006 0.94 0.030 0.42 0.0128
0.0105 0.0006 0.003 10 Inv. ex. 0.092 0.004 1.25 0.057 0.50 0.0142
0.0109 0.0007 0.002 11 Inv. ex. 0.065 0.006 1.00 0.064 0.42 0.0111
0.0110 0.0008 0.001 12 Inv. ex. 0.124 0.003 1.23 0.061 0.57 0.0097
0.0108 0.0009 0.003 13 Inv. ex. 0.085 0.008 0.98 0.084 0.47 0.0089
0.0081 0.0004 0.002 14 Inv. ex. 0.074 0.008 1.10 0.099 0.49 0.0108
0.0087 0.0005 0.002 15 Inv. ex. 0.066 0.002 0.87 0.071 0.43 0.0090
0.0084 0.0002 0.001 16 Inv. ex. 0.075 0.005 1.10 0.084 0.48 0.0074
0.0095 0.0008 0.002 17 Inv. ex. 0.061 0.003 1.19 0.075 0.36 0.0004
0.0084 0.0004 0.002 18 Inv. ex. 0.081 0.002 1.00 0.088 0.42 0.0112
0.0091 0.0002 0.001 19 Inv. ex. 0.051 0.008 1.10 0.065 0.45 0.0140
0.0086 0.0005 0.002 0.13 20 Inv. ex. 0.061 0.002 1.42 0.039 0.58
0.0079 0.0088 0.0005 0.002 0.09 0.01 21 Inv. ex. 0.042 0.005 1.00
0.064 0.45 0.0142 0.0110 0.0004 0.001 0.10 22 Inv. ex. 0.137 0.006
1.21 0.051 0.52 0.0112 0.0087 0.0008 0.001 0.024 23 Inv. ex. 0.069
0.006 1.01 0.094 0.49 0.0104 0.0094 0.0004 0.001 0.013 24 Inv. ex.
0.068 0.005 0.73 0.081 0.42 0.0101 0.0088 0.0002 0.002 25 Inv. ex.
0.039 0.005 0.97 0.061 0.47 0.0091 0.0089 0.0003 0.001 26 Inv. ex.
0.074 0.009 0.87 0.044 0.45 0.0072 0.0114 0.0009 0.001 27 Inv. ex.
0.101 0.005 0.89 0.060 0.46 0.0080 0.0086 0.0003 0.001 28 Inv. ex.
0.054 0.005 0.55 0.070 0.47 0.0110 0.0092 0.0007 0.002 29 Inv. ex.
0.061 0.007 1.10 0.063 0.51 0.0080 0.0088 0.0005 0.001 30 Inv. ex.
0.077 0.004 1.00 0.069 0.49 0.0122 0.0085 0.0006 0.002 31 Inv. ex.
0.068 0.006 0.97 0.112 0.45 0.0088 0.0077 0.0007 0.001 32 Inv. ex.
0.056 0.006 1.16 0.087 0.43 0.0118 0.0096 0.0005 0.001 33 Inv. ex.
0.082 0.007 1.21 0.059 0.52 0.0083 0.0088 0.0004 0.001 0.04 34 Inv.
ex. 0.082 0.005 1.02 0.057 0.45 0.0138 0.0110 0.0004 0.001 35 Inv.
ex. 0.096 0.002 1.01 0.099 0.42 0.0110 0.0076 0.0004 0.002 36 Inv.
ex. 0.070 0.006 1.52 0.093 0.44 0.0101 0.0090 0.0003 0.001 37 Inv.
ex. 0.051 0.001 1.01 0.084 0.52 0.0101 0.0074 0.0003 0.001 0.12 38
Inv. ex. 0.066 0.003 1.31 0.084 0.53 0.0098 0.0089 0.0003 0.001
0.01 39 Inv. ex. 0.051 0.002 0.84 0.064 0.45 0.0098 0.0081 0.0003
0.001 40 Inv. ex. 0.082 0.003 1.12 0.087 0.43 0.0105 0.0103 0.0006
0.004 41 Inv. ex. 0.066 0.006 0.67 0.099 0.44 0.0125 0.0109 0.0006
0.003 42 Inv. ex. 0.055 0.009 1.39 0.075 0.41 0.0086 0.0106 0.0005
0.001 43 Inv. ex. 0.029 0.002 0.94 0.066 0.46 0.0092 0.0082 0.0005
0.001 0.08 44 Inv. ex. 0.092 0.005 0.89 0.060 0.45 0.0080 0.0097
0.0003 0.001 0.21 45 Inv. ex. 0.094 0.003 1.26 0.100 0.47 0.0062
0.0112 0.0004 0.002 46 Inv. ex. 0.084 0.005 1.12 0.054 0.44 0.0100
0.0112 0.0003 0.001 47 Inv. ex. 0.102 0.002 1.24 0.079 0.48 0.0092
0.0102 0.0003 0.002 Chemical ingredients (mass %) Ex. Cr Mo W Ni Cu
Sn Zn Ti Zr Mg Te 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
20 21 0.19 0.10 22 23 0.23 24 0.78 25 0.34 0.11 0.10 26 0.12 27
0.21 0.09 28 0.16 29 0.27 0.21 0.18 30 0.36 31 0.31 0.16 32 0.26 33
0.11 0.12 34 0.15 35 0.004 36 0.25 0.18 0.08 37 0.18 0.010 38 0.11
0.07 0.06 39 0.007 40 0.0012 41 0.0008 42 0.12 0.10 0.004 43 0.008
0.002 44 0.19 0.09 0.11 0.005 45 0.01 46 47
TABLE-US-00002 TABLE 2 Chemical ingredients Evaluation (mass %)
Calculated result TEM replica MnS MnO area rate Drill life Ex.
Class Bi Pb N N allowable range density (%) VL1000 1 Inv. ex.
0.0091 0.0020 to 0.0132 4235 11.3 129 2 Inv. ex. 0.0133 0.0031 to
0.0165 1572 9.3 121 3 Inv. ex. 0.0075 0.0020 to 0.0145 633 12.0 130
4 Inv. ex. 0.0120 0.0043 to 0.0177 1001 8.6 131 5 Inv. ex. 0.0182
0.0092 to 0.0226 7006 10.9 125 6 Inv. ex. 0.0156 0.0068 to 0.0202
1421 6.2 131 7 Inv. ex. 0.0030 0.0020 to 0.0038 7950 10.8 128 8
Inv. ex. 0.0042 0.0020 to 0.0121 8014 12.0 126 9 Inv. ex. 0.0158
0.0066 to 0.0200 36190 5.9 135 10 Inv. ex. 0.0170 0.0085 to 0.0219
27954 7.2 126 11 Inv. ex. 0.0166 0.0044 to 0.0178 31904 8.0 132 12
Inv. ex. 0.0138 0.0026 to 0.0160 38596 7.8 131 13 Inv. ex. 0.0139
0.0020 to 0.0150 40780 5.3 146 14 Inv. ex. 0.0167 0.0040 to 0.0174
35986 5.7 127 15 Inv. ex. 0.0109 0.0020 to 0.0151 42635 6.4 138 16
Inv. ex. 0.0101 0.0020 to 0.0130 34583 6.2 131 17 Inv. ex. 0.0029
0.0020 to 0.0039 28951 10.5 130 18 Inv. ex. 0.0047 0.0046 to 0.0180
31904 11.5 131 19 Inv. ex. 0.0168 0.0082 to 0.0216 30002 6.7 154 20
Inv. ex. 0.0091 0.0020 to 0.0137 4006 11.4 128 21 Inv. ex. 0.0167
0.0085 to 0.0219 36666 11.2 143 22 Inv. ex. 0.0139 0.0046 to 0.0180
33525 7.9 139 23 Inv. ex. 0.0113 0.0035 to 0.0169 41496 8.0 132 24
Inv. ex. 0.0146 0.0031 to 0.0165 51190 9.2 136 25 Inv. ex. 0.0121
0.0020 to 0.0152 41418 9.1 141 26 Inv. ex. 0.0107 0.0020 to 0.0128
45333 10.5 140 27 Inv. ex. 0.0099 0.0020 to 0.0138 45290 7.6 129 28
Inv. ex. 0.0151 0.0043 to 0.0177 68227 9.1 144 29 Inv. ex. 0.0087
0.0020 to 0.0138 38627 9.0 144 30 Inv. ex. 0.0179 0.0059 to 0.0193
42109 7.7 138 31 Inv. ex. 0.0129 0.0020 to 0.0148 38203 7.8 136 32
Inv. ex. 0.0160 0.0053 to 0.0187 22403 8.4 142 33 Inv. ex. 0.0102
0.0020 to 0.0142 33525 9.1 138 34 Inv. ex. 0.0167 0.0079 to 0.0213
35333 11.4 144 35 Inv. ex. 0.0152 0.0043 to 0.0177 31190 6.8 133 36
Inv. ex. 0.0133 0.0031 to 0.0165 1741 9.3 122 37 Inv. ex. 0.0152
0.0031 to 0.0165 45064 6.7 132 38 Inv. ex. 0.0110 0.0027 to 0.0161
29182 8.6 137 39 Inv. ex. 0.0141 0.0027 to 0.0161 47333 8.4 137 40
Inv. ex. 0.0148 0.0037 to 0.0171 25193 10.6 145 41 Inv. ex. 0.0170
0.0063 to 0.0197 57651 10.1 142 42 Inv. ex. 0.0075 0.0020 to 0.0146
741 10.7 132 43 Inv. ex. 0.0141 0.0020 to 0.0154 42029 8.5 137 44
Inv. ex. 0.0094 0.0020 to 0.0138 44000 9.9 143 45 Inv. ex. 0.0102
0.0020 to 0.0115 22907 13.4 140 46 Inv. ex. 0.07 0.0137 0.0030 to
0.0164 26969 9.7 139 47 Inv. ex. 0.15 0.0128 0.0020 to 0.0154 25833
9.9 139 Evaluation Manufacturability Finished Hot surface rough.
ductility Plunge Long Chip (drawing Melt loss Ex. cutting turning
evac. %) rate Result Remarks 1 10.1 8.6 G 89.1 G 0.45 G G Claim 1
inv. ex. 2 8.0 6.8 G 93.0 G 0.47 G G Claim 1 inv. ex. 3 7.9 6.7 G
91.0 G 0.59 G G Claim 1 inv. ex. 4 7.7 6.5 G 89.0 G 0.45 G G Claim
1 inv. ex. 5 8.1 6.9 G 94.6 G 0.57 G G Claim 1 inv. ex. 6 5.2 4.4 G
95.0 G 0.30 G G Claim 1 inv. ex. 7 10.1 8.6 G 96.4 G 0.51 G G Claim
1 inv. ex. 8 10.3 8.8 G 94.6 G 0.53 G G Claim 1 inv. ex. 9 4.4 3.7
G 86.9 G 0.27 G G Claim 2 inv. ex. 10 5.2 4.4 G 91.6 G 0.22 G G
Claim 2 inv. ex. 11 5.7 4.8 G 90.0 G 0.39 G G Claim 2 inv. ex. 12
5.7 4.8 G 82.9 G 0.24 G G Claim 2 inv. ex. 13 5.1 4.3 G 93.8 G 0.23
G G Claim 2 inv. ex. 14 5.1 4.3 G 89.0 G 0.32 G G Claim 2 inv. ex.
15 6.0 5.1 G 90.6 G 0.35 G G Claim 2 inv. ex. 16 5.1 4.3 G 93.1 G
0.31 G G Claim 2 inv. ex. 17 9.8 8.3 G 94.3 G 0.33 G G Claim 2 inv.
ex. 18 9.9 8.4 G 91.5 G 0.61 G G Claim 2 inv. ex. 19 6.1 5.2 G 90.8
G 0.35 G G Claim 3 inv. ex., V added 20 10.2 8.7 G 82.6 G 0.43 G G
Claim 3 inv. ex., V.cndot.Nb added 21 8.0 6.8 G 83.7 G 0.87 G G
Claim 3 inv. ex., V.cndot.Cr.cndot.Ni added 22 7.1 6.0 G 86.7 G
0.31 G G Claim 3 inv. ex., Nb added 23 6.7 5.7 G 82.6 G 0.63 G G
Claim 3 inv. ex., Nb.cndot.W added 24 8.2 7.0 G 92.0 G 0.32 G G
Claim 3 inv. ex., Cr added 25 8.0 6.8 G 81.5 G 0.61 G G Claim 3
inv. ex., Cr.cndot.Mo.cndot.Ni added 26 7.2 6.1 G 90.8 G 0.56 G G
Claim 3 inv. ex., Mo added 27 6.9 5.9 G 83.0 G 0.50 G G Claim 3
inv. ex., Mo.cndot.Cu added 28 7.8 6.6 G 93.0 G 0.31 G G Claim 3
inv. ex., W added 29 8.0 6.8 G 81.7 G 0.65 G G Claim 3 inv. ex.,
Cr.cndot.W.cndot.Ni added 30 7.1 6.0 G 89.9 G 0.33 G G Claim 3 inv.
ex., Ni added 31 7.9 6.7 G 87.1 G 0.48 G G Claim 3 inv. ex., Niand
Cu added 32 6.9 5.9 G 93.1 G 0.41 G G Claim 3 inv. ex., Cu added 33
8.1 6.9 G 82.6 G 0.61 G G Claim 3 inv. ex., Nb.cndot.Mo.cndot.Cu
added 34 8.1 6.9 G 93.9 G 0.37 G G Claim 4 inv. ex., Sn added 35
7.0 6.0 G 94.0 G 0.36 G G Claim 4 inv. ex., Zn added 36 8.1 6.9 G
90.2 G 0.46 G G Claim 4 inv. ex., Cr.cndot.Ni.cndot.Sn added 37 7.1
6.0 G 90.1 G 0.49 G G Claim 4 inv. ex., V.cndot.Sn.cndot.Zn added
38 7.6 6.5 G 83.3 G 0.62 G G Claim 4 inv. ex.,
Nb.cndot.W.cndot.Ni.cndot.Sn added 39 8.1 6.9 G 94.4 G 0.42 G G
Claim 5 inv. ex., Ti added 40 8.1 6.9 G 90.3 G 0.67 G G Claim 5
inv. ex., Zr added 41 7.3 6.2 G 92.4 G 0.50 G G Claim 5 inv. ex.,
Mg added 42 7.9 6.7 G 84.1 G 0.61 G G Claim 5 inv. ex.,
Mo.cndot.W.cndot.Zr added 43 8.1 6.9 G 84.2 G 0.56 G G Claim 5 inv.
ex., Nb.cndot.Zn.cndot.Ti added 44 8.0 6.8 G 81.3 G 0.64 G G Claim
5 inv. ex., V.cndot.Cr.cndot.Ni.cndot.Sn.cndot.Zr added 45 9.4 8.0
G 87.9 G 0.64 G G Claim 6 inv. ex., Te added 46 6.8 5.8 G 85.1 G
0.50 G G Claim 6 inv. ex., Bi added 47 7.6 6.5 G 85.9 G 0.36 G G
Claim 6 inv. ex., Pb added
TABLE-US-00003 TABLE 3 Chemical ingredients (mass %) Ex. Class C Si
Mn P S B O Ca Al V Nb 48 Inv. ex. 0.113 0.007 1.51 0.045 0.41
0.0102 0.0089 0.0004 0.002 0.10 49 Inv. ex. 0.080 0.005 1.35 0.067
0.42 0.0132 0.0106 0.0004 0.003 0.05 50 Inv. ex. 0.067 0.004 1.31
0.097 0.44 0.0101 0.0099 0.0005 0.002 51 Inv. ex. 0.062 0.006 1.21
0.058 0.47 0.0114 0.0092 0.0006 0.003 52 Inv. ex. 0.091 0.006 0.99
0.101 0.42 0.0064 0.0102 0.0004 0.001 0.09 53 Inv. ex. 0.102 0.005
1.13 0.046 0.45 0.0092 0.0103 0.0006 0.002 54 Inv. ex. 0.039 0.007
1.27 0.074 0.51 0.0087 0.0110 0.0003 0.002 55 Inv. ex. 0.049 0.005
1.32 0.065 0.46 0.0068 0.0061 0.0002 0.001 0.11 0.02 56 Inv. ex.
0.060 0.004 0.93 0.072 0.37 0.0105 0.0086 0.0004 0.001 57 Inv. ex.
0.070 0.003 1.10 0.082 0.43 0.0109 0.0087 0.0005 0.001 58 Inv. ex.
0.060 0.003 1.13 0.084 0.46 0.0098 0.0087 0.0005 0.001 59 Inv. ex.
0.065 0.004 1.12 0.081 0.45 0.0090 0.0090 0.0005 0.001 60 Inv. ex.
0.069 0.003 0.97 0.061 0.37 0.0061 0.0084 0.0005 0.001 61 Inv. ex.
0.067 0.005 0.99 0.061 0.38 0.0099 0.0067 0.0006 0.001 62 Inv. ex.
0.071 0.005 0.92 0.045 0.35 0.0101 0.0098 0.0003 0.001 63 Inv. ex.
0.080 0.004 0.95 0.061 0.32 0.0087 0.0099 0.0004 0.001 64 Inv. ex.
0.059 0.006 0.90 0.058 0.34 0.089 0.0094 0.0006 0.003 65 Inv. ex.
0.090 0.006 1.00 0.106 0.41 0.0097 0.0096 0.0005 0.001 0.12 66 Inv.
ex. 0.080 0.003 0.94 0.060 0.40 0.0099 0.0092 0.0004 0.001 67 Inv.
ex. 0.090 0.005 1.01 0.061 0.41 0.0092 0.0093 0.0003 0.001 68 Inv.
ex. 0.059 0.004 1.21 0.074 0.49 0.0085 0.0105 0.0003 0.002 0.11 69
Inv. ex. 0.067 0.005 0.94 0.041 0.35 0.0087 0.0096 0.0002 0.001 70
Inv. ex. 0.090 0.004 1.06 0.045 0.39 0.0101 0.0093 0.0004 0.002 71
Inv. ex. 0.091 0.003 1.01 0.062 0.36 0.0087 0.0090 0.0004 0.001 72
Inv. ex. 0.081 0.004 0.94 0.051 0.35 0.0086 0.0088 0.0005 0.001
Chemical ingredients (mass %) Ex. Cr Mo W Ni Cu Sn Zn Ti Zr Mg Te
48 0.13 0.005 0.001 0.03 49 0.11 0.06 0.003 50 0.11 0.2 0.10 0.002
0.001 51 0.11 0.001 0.0007 52 53 0.15 0.09 0.003 0.01 54 0.09 0.12
0.002 0.0006 55 0.18 0.10 0.13 0.10 0.14 0.21 0.003 0.001 0.002
0.0004 0.001 56 57 58 59 60 61 0.0013 62 0.69 0.11 0.12 63 0.12
0.16 64 0.10 65 0.09 0.11 66 0.11 67 0.001 68 0.09 0.10 0.0009 69
0.11 0.12 0.0008 70 0.49 0.12 0.11 0.0006 71 0.0005 72 0.09 0.10
0.0006
TABLE-US-00004 TABLE 4 Evaluation Calculated Finished surface
Chemical results MnO Drill roughness ingredients (mass %) N
allowable TEM replica area rate life Plunge Long Ex. Class Bi Pb N
range MnS density (%) VL1000 drilling turning 48 Inv. ex. 0.0120
0.0033 to 0.0167 1025 7.8 130 6.9 5.9 49 Inv. ex. 0.11 0.0182
0.0072 to 0.0206 6941 10.8 126 8.0 6.8 50 Inv. ex. 0.0148 0.0031 to
0.0165 14015 11.0 146 8.7 7.4 51 Inv. ex. 0.05 0.0170 0.0048 to
0.0182 26099 8.6 142 7.3 6.2 52 Inv. ex. 0.10 0.0102 0.0020 to
0.0117 32619 11.8 139 9.1 7.7 53 Inv. ex. 0.0137 0.0020 to 0.0154
28000 8.7 137 6.6 5.6 54 Inv. ex. 0.06 0.0128 0.0020 to 0.0147
28627 9.8 141 7.0 6.0 55 Inv. ex. 0.04 0.09 0.0091 0.0020 to 0.0122
17246 4.7 149 6.0 5.1 56 Inv. ex. 0.0039 0.0037 to 0.0171 19864 9.3
138 7.0 7.2 57 Inv. ex. 0.0045 0.0042 to 0.0176 26425 9.7 140 7.5
7.4 58 Inv. ex. 0.0030 0.0027 to 0.0161 30012 9.7 140 7.5 7.4 59
Inv. ex. 0.0021 0.0020 to 0.0151 41012 6.2 140 6.0 5.8 60 Inv. ex.
0.07 0.0041 0.0020 to 0.0113 39569 8.1 128 7.1 6.4 61 Inv. ex.
0.0074 0.0029 to 0.0163 47551 5.1 129 6.0 5.1 62 Inv. ex. 0.06
0.0080 0.0031 to 0.0165 6764 9.4 135 8.6 6.4 63 Inv. ex. 0.07
0.0070 0.0020 to 0.0147 4166 10.8 130 8.8 7.3 64 Inv. ex. 0.10
0.0080 0.0020 to 0.0150 6702 8.7 132 7.3 6.2 65 Inv. ex. 0.11
0.0067 0.0026 to 0.0160 3001 10.9 139 9.0 7.6 66 Inv. ex. 0.06
0.0071 0.0029 to 0.0163 1575 8.8 133 7.1 6.4 67 Inv. ex. 0.09
0.0066 0.0020 to 0.0154 5745 11.3 129 7.3 8.1 68 Inv. ex. 0.0069
0.0020 to 0.0145 2925 9.6 131 6.8 6.1 69 Inv. ex. 0.0070 0.0020 to
0.0147 2762 10.2 129 7.8 7.1 70 Inv. ex. 0.12 0.0069 0.0031 to
0.0165 9125 10.3 141 8.7 7.4 71 Inv. ex. 0.06 0.0060 0.0020 to
0.0147 6196 10.1 138 7.7 7.5 72 Inv. ex. 0.07 0.0064 0.0020 to
0.0146 2762 9.8 135 7.8 7.4 Evaluation Manufacturability Hot
ductility Chip (drawing Melt loss Ex. disposal %) rate Result
Remarks 48 G 83.1 G 0.42 G G Claim 6 inv. ex.,
V.cndot.Cr.cndot.Zn.cndot.Ti.cndot.Te added 49 G 81.3 G 0.55 G G
Claim 6 inv. ex., Nb.cndot.W.cndot.Sn.cndot.Zr.cndot.Bi added 50 G
82.1 G 0.71 G G Claim 6 inv. ex.,
Mo.cndot.W.cndot.Sn.cndot.Zr.cndot.Te added 51 G 91.0 G 0.58 G G
Claim 6 inv. ex., Cu.cndot.Zn.cndot.Mg.cndot.Bi added 52 G 83.1 G
0.88 G G Claim 6 inv. ex., V.cndot.Pb added 53 G 84.1 G 0.58 G G
Claim 6 inv. ex., Cr.cndot.Sn.cndot.Zr.cndot.Te added 54 G 81.1 G
0.79 G G Claim 6 inv. ex., Ni.cndot.Cu.cndot.Zn.cndot.Mg.cndot.Bi
added 55 G 80.3 G 0.34 G G Claim 6 inv. ex., all elements added 56
G 81.2 G 0.72 G G Claim 2 inv. ex. 57 G 81.0 G 0.71 G G Claim 2
inv. ex. 58 G 81.0 G 0.71 G G Claim 2 inv. ex. 59 G 83.0 G 0.76 G G
Claim 2 inv. ex. 60 G 82.3 G 0.59 G G Claim 6 inv. ex., Pb added 61
G 80.3 G 0.34 G G Claim 6 inv. ex., Te added 62 G 82.1 G 0.77 G G
Claim 6 inv. ex., Pb.cndot.Ni.cndot.Cu.cndot.Cr added 63 G 81.1 G
0.73 G G Claim 6 inv. ex., Pb.cndot.Ni.cndot.Cu added 64 G 81.0 G
0.65 G G Claim 6 inv. ex., Pb.cndot.Mo added 65 G 80.3 G 0.72 G G
Claim 6 inv. ex., Pb.cndot.V.cndot.Ni.cndot.Cu added 66 G 80.9 G
0.75 G G Claim 6 inv. ex., Pb.cndot.W added 67 G 81.0 G 0.88 G G
Claim 6 inv. ex., Pb.cndot.Ti added 68 G 81.1 G 0.76 G G Claim 6
inv. ex., Te.cndot.V.cndot.Ni.cndot.Cu added 69 G 80.3 G 0.86 G G
Claim 6 inv. ex., Te.cndot.Ni.cndot.Cu added 70 G 80.9 G 0.86 G G
Claim 6 inv. ex., Pb.cndot.Te.cndot.Cr.cndot.Ni.cndot.Cu added 71 G
80.9 G 0.69 G G Claim 6 inv. ex., Pb.cndot.Te added 72 G 80.2 G
0.72 G G Claim 6 inv. ex., Pb.cndot.Te.cndot.Ni.cndot.Cu added
TABLE-US-00005 TABLE 5 Chemical ingredients (mass %) Ex. Class C Si
Mn P S B O Ca Al V Nb Cr Mo W Ni Cu Sn Zn Ti Zr Mg Te 73 Co. ex
0.082 0.008 1.35 0.090 0.65 0.0056 0.0073 0.0004 0.004 74 Co. ex
0.062 0.007 0.82 0.071 0.40 0.0182 0.0095 0.0005 0.003 75 Co. ex
0.075 0.008 1.15 0.050 0.42 0.0075 0.0041 0.0051 0.002 76 Co. ex
0.021 0.014 0.74 0.077 0.48 0.0091 0.0206 0.004 77 Co. ex 0.038
0.014 2.71 0.104 0.62 0.0051 0.0176 0.003 78 Co. ex 0.061 0.013
1.58 0.073 0.61 0.0112 0.0216 0.002 79 Co. ex 0.023 0.010 1.94
0.092 0.62 0.0084 0.0019 0.002 80 Co. ex 0.040 0.008 1.88 0.070
0.63 0.0061 0.0046 0.0035 0.003 81 Co. ex 0.016 0.003 1.43 0.072
0.42 0.0091 0.0199 0.004 82 Co. ex 0.062 0.013 0.99 0.088 0.49
0.0027 0.0196 0.002 83 Co. ex 0.061 0.007 1.47 0.091 0.15 0.0100
0.0106 0.0005 0.002 84 Co. ex 0.060 0.007 0.84 0.066 0.46 0.0171
0.004 85 Co. ex 0.041 0.011 0.50 0.080 0.29 0.0205 0.003 86 Co. ex
0.060 0.010 1.09 0.064 0.22 0.0103 0.0169 0.002 87 Co. ex 0.092
0.008 1.39 0.066 0.61 0.0158 0.0045 0.0016 0.004 88 Co. ex 0.065
0.007 1.78 0.091 0.28 0.0090 0.0006 0.003 89 Co. ex 0.021 0.012
0.71 0.069 0.42 0.0082 0.0005 0.004 90 Co. ex 0.042 0.012 2.76
0.083 0.43 0.0082 0.0081 0.0004 0.001 91 Co. ex 0.063 0.013 1.39
0.062 0.45 0.0064 0.0044 0.0023 0.002 92 Co. ex 0.038 0.011 2.87
0.091 0.42 0.0071 0.0065 0.0006 0.002 93 Co. ex 0.054 0.014 1.11
0.068 0.63 0.0068 0.0068 0.0005 0.003 94 Co. ex 0.087 0.015 1.39
0.080 0.10 0.0011 0.0040 0.0039 0.003 95 Co. ex 0.131 0.022 1.63
0.050 0.05 0.0112 0.0002 0.002 96 Co. ex 0.046 0.005 2.15 0.081
0.41 0.0050 0.0082 0.0004 0.001 97 Co. ex 0.067 0.007 1.41 0.062
0.44 0.0131 0.0045 0.0021 0.002 98 Co. ex 0.112 0.006 1.52 0.071
0.41 0.0134 0.0101 0.0004 0.003 99 Co. ex 0.034 0.013 2.74 0.091
0.42 0.0101 0.0068 0.0005 0.002 100 Co. ex 0.055 0.009 1.13 0.071
0.64 0.0141 0.0069 0.0004 0.003 101 Co. ex 0.011 0.012 1.32 0.080
0.39 0.0017 0.0105 0.0003 0.003 102 Co. ex 0.017 0.017 1.59 0.051
0.41 0.0059 0.0110 0.0002 0.002
TABLE-US-00006 TABLE 6 Evaluation Finished surface Chemical ing.
Calculated MnO Drill roughness (mass %) results TEM replica area
rate life Plunage Long Ex. Class Bi Pb N N allowable range MnS
density (%) VL1000 drilling turning 73 Co. ex 0.0077 0.0020 to
0.0107 4098 11.1 119 9.9 10.1 74 Co. ex 0.0200 0.0137 to 0.0271
3521 14.1 124 9.1 9.9 75 Co. ex 0.0087 0.0020 to 0.0132 1102 6.4
107 11.2 10.4 76 Co. ex 0.0118 0.0020 to 0.0152 3265 23.7 121 8.6
13.1 77 Co. ex 0.0091 0.0020 to 0.0100 45 29.6 119 8.9 13.3 78 Co.
ex 0.0207 0.0046 to 0.0180 501 24.6 118 9.1 13.9 79 Co. ex 0.0158
0.0020 to 0.0034 206 16.4 106 9.7 12.9 80 Co. ex 0.0018 0.0020 to
0.0113 1998 6.8 107 12.5 9.9 81 Co. ex 0.0019 0.0020 to 0.0152 682
25.1 98 12.3 13.1 82 Co. ex 0.0169 0.0020 to 0.0069 3699 25.1 121
9.8 13.8 83 Co. ex 0.0119 0.0030 to 0.0164 5 20.0 81 14.5 18.9 84
Co. ex 0.0122 0.0020 to 0.0034 556 30.6 110 11.9 17.9 85 Co. ex
0.0079 0.0020 to 0.0034 1309 33.8 99 12.0 18.7 86 Co. ex 0.0081
0.0034 to 0.0168 7 29.3 98 14.2 18.9 87 Co. ex 0.0251 0.0105 to
0.0239 46 16.4 99 12.3 17.9 88 Co. ex 0.0018 0.0020 to 0.0034 31
24.3 111 12.4 18.0 89 Co. ex 0.0074 0.0020 to 0.0034 2009 21.8 95
12.1 17.7 90 Co. ex 0.0016 0.0020 to 0.0141 26 15.8 104 12.0 13.0
91 Co. ex 0.0019 0.0020 to 0.0117 3102 7.1 100 11.8 9.8 92 Co. ex
0.0140 0.0020 to 0.0126 11 9.1 122 12.0 9.3 93 Co. ex 0.0291 0.0020
to 0.0122 1006 9.3 118 10.3 9.1 94 Co. ex 0.0045 0.0020 to 0.0048 6
16.9 54 15.0 23.1 95 Co. ex 0.0019 0.0020 to 0.0034 2 25.3 63 16.7
22.6 96 Co. ex 0.0123 0.0020 to 0.0099 34 16.2 105 12.1 13.2 97 Co.
ex 0.0254 0.0070 to 0.0204 2974 7.8 111 10.8 9.7 98 Co. ex 0.0051
0.0074 to 0.0208 1971 9.8 113 10.2 9.2 99 Co. ex 0.0018 0.0031 to
0.0165 19 9.3 121 11.8 9.1 100 Co. ex 0.0012 0.0083 to 0.0217 1210
9.7 108 10.6 9.4 101 Co. ex 0.0045 0.0020 to 0.0056 7 17.6 112 11.6
19.2 102 Co. ex 0.0039 0.0020 to 0.0111 9 16.7 109 12.0 18.2
Evaluation Manufacturability Hot Chip ductility Melt loss Ex. evac.
(drawing %) rate Result Remarks 73 G 50.3 P 0.61 G P S upper limit
exceeded 74 G 57.3 P 0.65 G P B upper limit exceeded 75 G 61.0 P
0.28 G P Ca upper limit exceeded, C lower limit exceeded 76 G 59.5
P 1.79 P P No Ca, O upper limit exceeded, MnO exceeded 77 G 66.8 P
2.35 P P No Ca, S.cndot.O upper limits exceeded, MnO exceeded 78 G
50.1 P 1.78 P P No Ca, S.cndot.O.cndot.N upper limits exceeded, MnO
exceeded 79 G 54.1 P 1.29 P P No B, S.cndot.O.cndot.N upper limit
exceeded, MnO exceeded 80 G 60.1 P 0.44 G P S.cndot.Ca upper
limits, N.cndot.O lower limits exceeded 81 G 72.3 P 1.70 P P No Ca,
O.cndot.N upper limits exceeded, MnO exceeded 82 G 51.2 P 2.00 P P
No Ca, N upper limit exceeded, MnO exceeded 83 P 74.6 P 1.85 P P S
lower limit exceeded, MnO exceeded 84 G 52.3 P 2.03 P P B.cndot.No
Ca, O upper limit exceeded, MnO exceeded 85 G 65.9 P 2.73 P P
B.cndot.No Ca, S lower limit, O upper limit, MnO exceeded 86 P 70.1
P 1.99 P P No Ca, S lower limit, O upper limit, MnO exceeded 87 G
52.0 P 1.23 P P S.cndot.B.cndot.Ca, N upper limits, O lower limit,
MnO exceeded 88 G 59.3 P 1.44 P P No B, S.cndot.N lower limits
exceeded, MnO exceeded 89 G 69.0 P 1.58 P P No B, MnO exceeded 90 G
61.3 P 1.25 P P N lower limit exceeded, MnO exceeded 91 G 63.6 P
0.29 G P Ca upper limit exceeded, O.cndot.N lower limit exceeded 92
G 60.9 P 0.50 G P N upper limit exceeded 93 G 51.9 P 0.40 G P
S.cndot.N upper limit exceeded 94 P 82.0 G 1.48 P P S.cndot.O lower
limits, Ca upper limit, MnO exceeded 95 P 82.3 G 1.99 P P No B,
S.cndot.N lower limit exceeded, MnO exceeded 96 G 62.3 P 1.33 P P N
upper limit exceeded, MnO exceeded 97 G 52.1 P 0.48 G P N.cndot.Ca
upper limit exceeded, O lower limit exceeded 98 G 61.2 P 0.52 G P N
lower limit exceeded 99 G 59.6 P 0.34 G P N lower limit exceeded
100 G 53.2 P 0.35 G P N lower limit exceeded, S upper limit
exceeded 101 P 70.9 P 1.35 P P MnO exceeded 102 P 65.6 P 1.28 P P
MnO exceeded
TABLE-US-00007 TABLE 7 Cutting conditions Drill Others Cutting
speed: 10 to 200 m/min .phi.3 mm Hole depth: 9 mm Feed: 0.25 mm/rev
NACHI general Tool life: until Non-water soluble drill breakage
cutting fluid
TABLE-US-00008 TABLE 8 Cutting conditions Tool Others Cutting
speed: 80 m/min Corresponding Evaluation Feed: 0.05 mm/rev to SKH51
timing: 200th Lubrication: Non-water Rake angle 15.degree. groove
soluble cutting fluid Relief angle 6.degree.
TABLE-US-00009 TABLE 9 Cutting conditions Tool Others Cutting
speed: 80 m/min Corresponding Evaluation Feed: 0.05 mm/rev to
carbide tool timing: 800th Depth of cut: 1 mm type P10 piece
Lubrication: Water- rake angle 10.degree. soluble cutting fluid
relief angle 7.degree.
INDUSTRIAL APPLICABILITY
[0142] According to the present invention, it is possible to
provide machining steel superior in tool life at the time of
machining, finished surface roughness, chip evacuation, and other
machinability, accompanied with little melt loss of plate
refractories of the continuous casting sliding nozzles, and
superior in manufacturability with good ductility in hot
rolling.
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