U.S. patent application number 13/580722 was filed with the patent office on 2012-12-13 for metallic material as a solid solution having a body-centered cubic (bcc) structure, an orientation of crystal axis <001> of which is controlled, and method of manufacturing the same.
This patent application is currently assigned to NATIONAL UNIVERSITY CORPORATION, YOKOHAMA NATIONAL UNIVERSITY. Invention is credited to Hiroshi Fukutomi, Kazuto Okayasu, Yusuke Onuki.
Application Number | 20120312432 13/580722 |
Document ID | / |
Family ID | 44507002 |
Filed Date | 2012-12-13 |
United States Patent
Application |
20120312432 |
Kind Code |
A1 |
Fukutomi; Hiroshi ; et
al. |
December 13, 2012 |
METALLIC MATERIAL AS A SOLID SOLUTION HAVING A BODY-CENTERED CUBIC
(BCC) STRUCTURE, AN ORIENTATION OF CRYSTAL AXIS <001> OF
WHICH IS CONTROLLED, AND METHOD OF MANUFACTURING THE SAME
Abstract
An orientation of crystal axis <001> of the metallic
material as a solid solution having a structure of body-centered
cubic (BCC) is arranged along a work surface of the metallic
material by hot rolling process in a temperature range of
structuring the metallic material to be BCC single phase solid
solution. For example, Fe-Si alloy as the metallic material is
heated in the temperature range for BCC single phase solid
solution, and processed so as to arrange the orientation of crystal
axis <001> along the work surface by pressing the BCC single
phase solid solution in a strain rate to maintain work condition
for controlling motion of dislocation by atmosphere of solute atom
generated in BCC single solid solution and migrating grain boundary
by strain energy stored in a crystal grain as driving force.
Inventors: |
Fukutomi; Hiroshi;
(Yokohama-shi, JP) ; Okayasu; Kazuto;
(Yokohama-shi, JP) ; Onuki; Yusuke; (Yokohama-shi,
JP) |
Assignee: |
NATIONAL UNIVERSITY CORPORATION,
YOKOHAMA NATIONAL UNIVERSITY
YOKOHAMA-SHI
JP
|
Family ID: |
44507002 |
Appl. No.: |
13/580722 |
Filed: |
February 28, 2011 |
PCT Filed: |
February 28, 2011 |
PCT NO: |
PCT/JP2011/054548 |
371 Date: |
August 23, 2012 |
Current U.S.
Class: |
148/559 ;
148/400 |
Current CPC
Class: |
B21B 3/02 20130101; C22C
38/02 20130101; C22C 38/004 20130101; C21D 7/13 20130101; C22C
38/06 20130101; C21D 8/1222 20130101; C21D 8/12 20130101; C21D
8/1205 20130101; C21D 2201/05 20130101 |
Class at
Publication: |
148/559 ;
148/400 |
International
Class: |
C21D 8/00 20060101
C21D008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 26, 2010 |
JP |
2010-042132 |
Claims
1. A method of manufacturing a metallic material as a solid
solution having body-centered cubic (BCC) structure, comprising
steps of: heating the metallic material in a temperature range to
be single phase solid solution; and distributing crystal axes
<001> of the metallic material along a work surface of the
metallic material by hot compression process in the temperature
range.
2. A method of manufacturing Fe-Si alloy as a metallic material,
comprising steps of: heating the Fe-Si alloy in a temperature range
to be single phase solid solution having body-centered cubic (BCC)
structure; and applying compression process on the solid solution
having body-centered cubic (BCC) structure with a strain rate able
to maintain process condition in which solute atmosphere generated
in the single phase solid solution having body-centered cubic (BCC)
structure can control motion of dislocation and grain boundary can
move by strain energy stored in a crystal grain as driving force so
as to distribute crystal plane {100} in parallel to a work surface
of manufacturing process.
3. The method of manufacturing a metallic material according to
claim 1, wherein Fe-Si alloy is used as the solid solution having
the body-centered cubic (BCC) structure; and compression process
with strain rate from 1.times.10.sup.-5/s to 1.times.10.sup.-1/s is
applied to the Fe-Si alloy heated in the temperature range to
become single phase solid solution.
4. The method of manufacturing a metallic material according to
claim 3, wherein the temperature range is between 800-1300.degree.
C.
5. The method of manufacturing a metallic material according to
claim 4, wherein a total amount of strain of at least -0.5 is
generated at the single phase solid solution having the
body-centered cubic (BCC) structure by the compression process.
6. A metallic material as a solid solution having the body-centered
cubic (BCC) structure, wherein crystal axes <001> are
distributed along a work surface of manufacturing process by hot
compression process.
7. The metallic material according to claim 6, wherein the solid
solution having the body-centered cubic (BCC) structure has 14
times or more orientation density on a line of .PHI.=0.degree. at
.phi..sub.2=0.degree. section of crystal Orientation Distribution
Function (ODF) indicating a distribution of the crystal axes
<001> along the work surface of manufacturing process against
an average value 1 of the orientation density.
8. The metallic material according to claim 6, wherein Fe-Si alloy
is used as the solid solution having the body-centered cubic (BCC)
structure.
9. The method of manufacturing a metallic material according to
claim 2, wherein Fe-Si alloy is used as the solid solution having
the body-centered cubic (BCC) structure; and compression process
with strain rate from 1.times.10.sup.-5/s to 1.times.10.sup.-1/s is
applied to the Fe-Si alloy heated in the temperature range to
become single phase solid solution.
10. The method of manufacturing a metallic material according to
claim 9, wherein the temperature range is between 800-1300.degree.
C.
11. The method of manufacturing a metallic material according to
claim 10, wherein a total amount of strain of at least -0.5 is
generated at the single phase solid solution having the
body-centered cubic (BCC) structure by the compression process.
12. The metallic material according to claim 7, wherein Fe-Si alloy
is used as the solid solution having the body-centered cubic (BCC)
structure.
Description
[0001] Metallic Material as A Solid Solution having a body-centered
cubic (BCC) structure, an orientation of crystal axis <001>
of which is controlled, and Method of Manufacturing the Same.
TECHNICAL FIELD
[0002] This invention relates to a metallic material as a solid
solution having a body-centered cubic (BCC) structure, an
orientation of crystal axis <001> of which is controlled in a
plane, and a method of manufacturing the material, for example an
electromagnetic material used for an iron core of an electric
device, and the method of manufacturing the material.
BACKGROUND ART
[0003] An electrical steel sheet used widely in electric devices is
an example of a material which can perform large effect of
technical features by aligning crystal axis of a metal. For
example, when a direction of magnetic field as a transformer shown
in FIG. 3 is fixed, a grain-oriented electrical steel sheet, in
which crystal axis is controlled, is used. Preferably, magnetic
lines of force shown with dot lines 33 in FIG. 3 are provided in a
plane of core sheets 31, which are stacked to be aligned in a
direction of easy magnetization
[0004] For application of a rotor or a stator of a motor, a known
non-oriented electrical steel sheet is used to reduce core loss. A
single phase SRM (Switched reluctance motor) shown in FIG. 4
includes a stator 10, which a coil connected with an outer electric
power is wound, and a rotor 20 provided rotatably in the stator 10
and rotated by electromagnetic forces acting between the stator 10
and the rotor 20 when outer electric power is supplied to the
stator 10.
[0005] The stator 10 includes a yoke 12 having a ring shape, a
plurality of poles 16 projecting along a radial direction from the
yoke 12 toward the rotor 20 at an interval to each other through a
predetermined slot 14 along a circumference of the yoke 12, and a
coil 18 wound around the pole 16 and connected with the outer
electric power.
[0006] The stator 10 of the motor is manufactured by steps of
punching a stator sheet having a plane shape with the yoke 12 and
the pole 16 from a thin electrical steel sheet, stacking the stator
sheets to be an iron core having a predetermined height, and
winding a coil 18 around the magnetic core.
[0007] In such motor, a direction of magnetic field is changed
around a rotation axis of the rotor as the center according to
rotation of the rotor. Therefore, non-oriented electrical steel
sheet is applied for rotors and stators (for example, see Patent
Document 1).
[0008] Magnetization of steel has anisotropic property according to
a crystal axis. Magnetization along the axis <001> is acted
most easily with small hysteresis loss. Magnetization along the
axis <011> is acted next most easily with small hysteresis
loss. Magnetization along the axis <111> is acted in most
difficulty with large hysteresis loss. Therefore, for a rotor and a
stator of a motor, the orientation of the axis <001> is
mainly aligned preferably along a radial direction of the motor so
as to magnetize it easily and reduce core loss by hysteresis. Thus,
core material, which orientation of the axis <001> is aligned
rotational-symmetrically about an axis of a motor, is expected.
[0009] Unfortunately, no technology for controlling and aligning
crystal axis <001> of steel sheet sufficiently exists. As
next best way, for avoiding that orientation of crystal axis
<111> is aligned along the radial direction, and orientation
of crystal axis <001> is aligned eccentrically in a certain
direction, non-oriented electrical steel sheet made of silicon
steel and having isotropic property in 3-dimensions as shown in
FIG. 5 is developed and delivered by Nippon Steel Corporation, and
JFE Steel. Electrical steel sheet named by Hi-light core (trade
name) and Home core (trade name) is supplied.
[0010] According to the non-oriented electrical steel sheet having
non-directional property in 3-dimensions as shown in FIG. 5, a
direction of easy magnetization is eccentrically arranged not in a
certain direction in the steel sheet, but many crystal axes
<001> as an axis of easy magnetization are not arranged along
a surface of steel sheet. Thereby, magnetic flux density along the
surface of the steel sheet can not be increased, and improving
efficiency of motor is limited.
[0011] Therefore, in a viewpoint of saving energy of a motor, it is
expected to develop non-oriented electrical steel sheet which
magnetic flux density along a surface of the electrical steel sheet
is increased by aligning crystal plane {100} in parallel to the
surface of steel sheet so as to arrange crystal axis <001> as
axis of easy magnetization uniformly in all directions in the
surface of the steel sheet as shown in FIG. 6 (see Unpatent
Document 1).
[0012] Furthermore, for improving efficiency of a transformer, it
is expected to develop oriented electrical steel sheet, which
crystal axis <001> is arranged along magnetic flux path.
[0013] Thus, for improving energy efficiency of an electromagnetic
apparatus such a motor and a transformer, it is expected to control
an orientation of crystal axis <001> of an electromagnetic
material.
CITATION LIST
Patent Document
[0014] Patent Document 1: Japan Patent Application Published No.
2006-87289
Unpatent Document
[0015] Unpatent Document 1: NIPPON STEEL MONTHLY Apr. 2005, P.
11-14
SUMMARY OF INVENTION
Objects to be Solved
[0016] According to a metal having a face-centered cubic (FCC)
structure, such as aluminum, it is known as development of a fiber
texture {011} (compression plane) that uniaxial compression process
is effective for arranging crystal orientation having rotational
symmetry around a compression axis. According to a metal having a
body-centered cubic (BCC) structure, such as Fe, it is known that
by uniaxial compression process in room temperature (cold
compression), double fiber texture with {111}+{100}, in which the
orientation distribution with rotational symmetry in which crystal
planes {111} and {100} are parallel to the compression plane, is
formed to have stable orientation for deformation.
[0017] The usual uniaxial compression process has a problem that
not only crystal plane {100} arranging crystal axis <001>
having excellent magnetic property in parallel to the surface of
the steel sheet, but also crystal plane {111} unable to arrange
crystal axis <001> in the surface of the steel sheet exist
together. The usual uniaxial compression process develops crystal
plane {111} in the surface more than crystal plane {100}, so that
the uniaxial compression process is not applied as a method for
manufacturing electrical steel sheet so as to arrange crystal axis
<001> along a surface of the sheet.
[0018] Usually, it is difficult to control orientation of axis of
easy magnetization <001> by not only the uniaxial compression
process but also other method of manufacturing. Thus, there was no
method for manufacturing non-oriented electrical steel sheet which
has excellent magnetic property with large magnetic flux density
and small core loss by controlling the axis of easy magnetization
<001> in parallel to the surface of steel sheet. In short,
there was not non-oriented electrical steel sheet which the axis of
easy magnetization <001> was arranged in the surface of steel
sheet.
[0019] According to the above problems, an object of the present
invention is to control crystal axis of metal. For example, the
object is to control axis of easy magnetization <001> of an
iron based material along a work surface of manufacturing process.
The object is to provide a metallic material having excellent
magnetic property of easy magnetization along a surface of a sheet
and large magnetic flux density and small core loss by controlling
the axis of easy magnetization <001> along the work surface
of manufacturing process, and a method of manufacturing the
metallic material.
How to Attain the Object of the Present Invention
[0020] Usually, it is known that crystallographic texture including
crystal plane {110} (compression plane) is formed by uniaxial
compression deformation of Al-Mg solid solution alloy having FCC
structure in high temperature. In result of proceeding study for
crystal plane {100}, present inventors found that with increasing
amount of deformation, the crystal plane {100} develops, and after
that, the crystallographic texture becomes to be formed by only
crystal plane {100}.
[0021] After proceeding the study of its mechanism, it is found
experimentally that when amount of dislocation is increased by
deformation, a crystal grain having orientation of {100} consumes
other crystal grains having orientation of {110} and others by
grain boundary migration and grows preferentially.
[0022] Attention was paid that {100} was the orientation with low
Taylor factor, which corresponded to the total amount of shear
strain and thus the amount of dislocation was considered to be
small. Furthermore, it was noticed that {100} is stable orientation
for deformation.
[0023] This change from the crystal plane {110} to the crystal
plane {100} is not found in pure aluminum (Al) . Therefore, it is
considered that deformation of Al-Mg alloy by compression occurs
when the solute magnesium (Mg) atmosphere dragging of dislocations
dominates the deformation. Thereby, a hypothesis that uniform
distribution of dislocation enhances the preferential migration of
crystal grain with {100} orientation is proposed.
[0024] According to the hypothesis, the present inventor had a
thought that in a solid solution having body-centered cubic (BCC)
structure, different crystallographic texture from that of pure
metal would be generated. The present inventor focused that
different from that of FCC metal, {100} and {111} coexists at room
temperature due to difference in slip systems, and Taylor factor of
crystal plane {100} is lower than Taylor factor of crystal plane
{111}.
[0025] Therefore, the present inventor reached to have an idea that
when process condition, in which solute atmosphere dragging of
dislocation becomes dominant deformation mechanism and grain
boundary migration become possible, could be found, technology of
manufacturing process for material, by which {111} would be
disappeared and oppositely {100} is frequently arranged along the
surface of the sheet material, would be developed.
[0026] This idea could be applied generally for a metallic material
having body-centered cubic (BCC) structure. Therefore, after
studying iron-silicon alloy having body-centered cubic (BCC)
structure, that is silicon steel, which the idea could be applied,
it was found that increase of grain diameter and arrangement of
<001> along the plane surface for increasing magnetic flux
density could be controlled by manufacturing process condition.
[0027] A usual method of manufacturing non-oriented electrical
steel sheet is formed by combining two processes of cold working
and heat treatment, or hot working and heat treatment, and in
contrast, based on the above found phenomena, it was appeared that
electrical steel sheet, which can be controlled so as to align axes
of easy magnetization <001> along a work surface of
manufacturing process, by only one process of hot uniaxial
compression process or hot plane strain compression process, can be
manufactured. Thus, the present invention is accomplished.
[0028] The present invention is a method for manufacturing metallic
material as a solid solution having a body-centered cubic (BCC)
structure, in which the metallic material is formed by hot
compression process in a temperature range, in which the metallic
material becomes BCC single phase solid solution, so as to arrange
crystal axis <001> along a work surface of manufacturing
process of the metallic material.
[0029] According to the present invention, crystal axis <001>
of the metal can be distributed along the work surface of
manufacturing process without heat treatment after the
manufacturing process, so that principle of the present invention
can be applied for a metallic material as a solid solution having
body-centered cubic (BCC) structure, and it has varied
applications.
[0030] The present invention is a method for manufacturing metallic
material, for example electrical steel sheet, having steps of:
heating Fe-Si alloy as the metallic material in a temperature range
to be BCC single phase solid solution, and applying compression
process on the BCC solid solution with a strain rate able to
maintain process condition in which solute atmosphere generated in
the BCC single phase solid solution dominates dislocation motion
and grain boundary can migrate by strain energy stored in a crystal
grain as driving force so as to distribute {100} in parallel to a
work surface of manufacturing process.
[0031] When the BCC single phase solid solution is processed by
compression with the strain rate able to maintain process condition
in which solute atmosphere generated in the BCC single phase solid
solution can control motion of dislocation and grain boundary can
migrate by strain energy stored in a crystal grain as driving
force, the crystal plane {100} can be arranged in parallel to a
work surface of manufacturing process. Thus, crystal axis
<001> is distributed along the work surface of manufacturing
process.
[0032] The present invention is a method for manufacturing a
metallic material in which Fe-Si alloy is used as the solid
solution having the body-centered cubic (BCC) structure; and the
Fe-Si alloy is heated in temperature range to become BCC single
phase solid solution and compression process with strain rate from
1.times.10.sup.-5/s to 1.times.10.sup.-1/s is applied to the Fe-Si
alloy.
[0033] When the solid solution is Fe-Si alloy, the strain rate able
to maintain process condition in which solute atmosphere generated
in the BCC single phase solid solution can control motion of
dislocations and grain boundary can migrate by strain energy stored
in a crystal grain as driving force is in range from
1.times.10.sup.-5/s to 1.times.10.sup.-1/s. By applying compression
process in the condition, the crystal plane {100} can be
distributed in parallel to the work surface of manufacturing
process. For example, when applying uniaxial compression process
with the strain rate from 1.times.10.sup.-5/s to
1.times.10.sup.-1/s to Fe-Si alloy, an electrical steel sheet of
Fe-Si alloy having good properties is manufactured. The Fe-Si alloy
includes preferably Si of 1-7 weight %, and Fe remaining and
unavoidable impurities.
[0034] The present invention is further characterized in that the
temperature range is between 800-1300.degree. C.
[0035] By determining temperature range, electrical steel sheet
having good properties can be manufactured with
reproducibility.
[0036] The present invention is further characterized in that total
amount of strain of at least -0.5 is given at the single phase
solid solution having the body-centered cubic (BCC) structure by
the compression process.
[0037] By giving total amount of strain of at least -0.5 by
uniaxial compression process, a high-quality electrical steel
sheet, in which crystal axis <001> is securely controlled
along a surface of the sheet, can be provided. The {100}
(compression plane) is a crystal orientation with low strain energy
under uniaxial compression deformation, and the crystal arranged in
the orientation is stable against deformation, so that migration of
grain boundary is acted during deformation so as to increase grain
size of the crystal. Therefore, when the amount of strain is
increased, {100} fiber texture develops. Larger strain provides
better results. By making the total amount of strain larger, {100}
parallel to the work surface of manufacturing process grows
remarkably.
[0038] The present invention is also related to a metallic material
as a solid solution having the body-centered cubic (BCC) structure,
in which crystal axes <001> are distributed along a work
surface of manufacturing process by hot compression process.
Especially, the metallic material as a solid solution having
body-centered cubic (BCC) structure has 14 times or more
orientation density on a line of .PHI.=0.degree. at
.phi..sub.2=0.degree. section of crystal Orientation Distribution
Function (ODF), which indicates a distribution of the crystal axis
<001> along the work surface of manufacturing process against
an average value 1 of the orientation density.
[0039] According to the present invention, highly concentrated
orientation distribution along a specific direction, which could
not be provided usually, is realized.
[0040] When the metallic material as the solid solution having
body-centered cubic (BCC) structure is deformed by hot uniaxial
compression process in a condition in which solute atmosphere
dragging of dislocation is main deformation mechanism, the
dislocation in the solid solution is distributed uniformly, so that
grain boundary migration is acted according to distribution of
strain energy corresponding to the dislocation. Thereby, a
situation, in which crystal grains with {100} having small strain
energy grows in parallel to the surface of the steel sheet, can be
generated. Furthermore, when the metallic material is processed by
hot rolling or hot plane strain compression, the crystal axis
<001> is aligned along a direction of extending the material.
In short, in the all above cases, the crystal axis <001> is
controlled along the work surface of manufacturing process.
[0041] In case which Fe-Si alloy as the solid solution having the
body-centered cubic (BCC) structure, physically an electrical steel
sheet, is formed by hot uniaxial compression process, the
electrical steel sheet having 14 times or more orientation density
on the line of .PHI.=0.degree. at .phi..sub.2=0.degree. section of
crystal Orientation Distribution Function (ODF) for checking
distribution of the crystal axis <001> against the average
value 1 thereof can be easily realized.
[0042] Usual metal sheet has two or less orientation density on the
line of .PHI.=0.degree. at .phi..sub.2=0.degree. section of crystal
Orientation Distribution Function (ODF) against the average value 1
thereof.
[0043] The electrical steel sheet by Fe-Si alloy, in which the
distribution of the crystal axis {001} is controlled so as to be in
parallel to the work surface of manufacturing process, has better
properties comparing usual non-oriented electrical steel sheet.
Effects of the Invention
[0044] According to the metallic material and the method for
manufacturing the same by the above-mentioned present invention,
the metallic material in which the crystal axis is controlled,
especially, the electrical steel sheet, in which axis of easy
magnetization <001> is controlled to be aligned along the
work surface of manufacturing process, is provided, so that the
electrical steel sheet having excellent magnetic properties with
large magnetic flux and small core loss is supplied.
BRIEF DESCRIPTION OF DRAWINGS
[0045] FIG. 1 is a view at .phi..sub.2=0.degree. section of crystal
orientation distribution function (ODF) of non-oriented electrical
steel sheet formed by a method for manufacturing using hot uniaxial
compression process according to the present invention;
[0046] FIG. 2 is a view at .phi..sub.2=0.degree. section of crystal
orientation distribution function (ODF) of usual non-oriented
electrical steel sheet by prior art;
[0047] FIG. 3 is an illustration for explaining flow of lines of
magnetic force in an electrical steel sheet of a transformer;
[0048] FIG. 4 is an illustration for explaining a structure of a
motor using the electrical steel sheet;
[0049] FIG. 5 is an illustration showing a crystal distribution of
usual known non-oriented electrical steel sheet;
[0050] FIG. 6 is an illustration showing a crystal distribution of
non-oriented electrical steel sheet formed by a method for
manufacturing according to present invention;
[0051] FIG. 7A is an illustration for explaining a condition before
compression of uniaxial compression process;
[0052] FIG. 7B is an illustration for explaining a condition after
compression of uniaxial compression process;
[0053] FIG. 8A is an illustration for explaining a forming jig for
plane strain compression process;
[0054] FIG. 8B is an illustration for explaining another forming
jig for plane strain compression process;
[0055] FIG. 8C is an illustration of a work sample before forming
by plane strain compression process;
[0056] FIG. 8D is an illustration of a work sample after forming by
plane strain compression process;
[0057] FIG. 9 is an illustration for explaining a rolling
process;
[0058] FIG. 10 is an illustration for explaining a multi-direction
rolling process;
[0059] FIG. 11 is an illustration for explaining a drawing
process;
[0060] FIG. 12 is an illustration of a body-centered cubic (BCC)
structure;
[0061] FIG. 13A is an illustration showing orientations of axes of
easy magnetization <001> of usual non-oriented electrical
steel sheet used in a stator of a motor;
[0062] FIG. 13B is an illustration showing orientations of axes of
easy magnetization <001> of ideal non-oriented electrical
steel sheet used in a stator of a motor;
[0063] FIG. 14A is an illustration showing a pole figure of {100}
of usual non-oriented electrical steel sheet used in a stator of a
motor;
[0064] FIG. 14B is an illustration showing a pole figure of {100}
of the non-oriented electrical steel sheet by the present invention
used in a stator of a motor; and
[0065] FIG. 15 is a chart showing magnetic properties of usual
non-oriented electrical steel sheet (by dot line) and the
electrical steel sheet according to the present invention (solid
line).
DESCRIPTION OF EMBODIMENTS
[0066] Embodiments of an electrical steel sheet and a method for
manufacturing the steel sheet according to the present invention
will be described as following.
[0067] When a metallic material is deformed in high temperatures,
various mechanisms contribute to its deformation. In a metallic
material, usually, deformation by movement of dislocation is a
basic mechanism.
[0068] One of phenomena affecting mainly the movement of
dislocation is a dragging of a solute atmosphere generated in a
solid solution alloy under combination of a certain temperature
range and a strain rate. The phenomenon is that the dislocation
surrounded by the solute atoms moves together with the solute
atoms. For example, in Fe-Si alloy, Si as the solute atom forms the
solute atom atmosphere existing at higher density than an average
density in overall crystal around the dislocation. In a certain
range of deforming condition, the dislocation can not break away
from the solute atom atmosphere and move with dragging the
dislocation. Thereby, velocity of the dislocation is slowed by
dragging the solute atom atmosphere. In result, differently from
deformation under room temperature, the dislocation is distributed
uniformly in the crystal. In short, the dislocation dragging the
solute atmosphere is easily distributed uniformly in the
crystal.
[0069] Herein, the dislocation is a lattice defect and has strain
energy. Depending on an orientation of crystal, an amount of
dislocations contributing to its deformation is varied. Thereby,
when applying same amount of deformation, the amount of dislocation
is different from each crystal, and in result, amount of energy
stored in each crystal is varied. In usual manufacturing condition,
dislocations are distributed so as to cancel strain energy of each
crystal to each other. Difference of dislocation densities about
each crystal grain is not directly reflected to difference of the
strain energy stored in each crystal grain.
[0070] In contrast, by compression process in high temperature,
which generates movement of dislocation dragging solute atom
atmosphere, as a condition of deformation according to the present
invention, dislocations are distributed uniformly and effect of
canceling strain by dislocation is small. Therefore, difference of
the amount of dislocation reflects directly to difference of stored
strain energy.
[0071] Under the condition that the solute atom atmosphere controls
movement of dislocation, amount of strain energy in each crystal
grain depends strongly on the orientation of crystal. Thereby, the
crystal grain having small strain energy tends to grow up, so that
the grain boundary of the crystal having low strain energy is moved
preferentially.
[0072] The orientation of crystal having low strain energy under
uniaxial compression deformation of a solid solution having the
body-centered cubic (BCC) structure is {100} (surface of sheet) .
The orientation of crystal under plane strain compression
deformation such as rolling is <001> (extending direction) in
{100} (surface of plane) . Therefore, the crystal grains in the
orientation of crystal consume other crystal grains in other
orientations, and grow.
[0073] The crystal in the orientation of crystal plane {100} is
stable against compression deformation, so that during deformation,
the grain boundary migrates so as to grow the crystal grain.
Therefore, when increasing the strain, fiber texture {100} is
growing at uniaxial compression deformation, and {100}<001>
texture is growing at plane strain compression deformation.
[0074] Herein, {100} shows a work surface of manufacturing process,
and <001> shows an extending direction by rolling.
[0075] The present invention is accomplished based on the
above-mentioned knowledge. According to the present invention,
{100} is arranged in parallel to a sheet surface under both of
uniaxial compression deformation and plane strain compression
deformation. At compression deformation, the crystal plane {100} is
arranged in parallel to the surface of plate. Especially, at
uniaxial compression deformation, <001> is distributed
uniformly in high density in a direction vertical to a direction of
compression in the surface of the plane around the crystal axis
<100> as a normal of the crystal plane {100} as a rotation
axis. At plane strain deformation such as rolling, when a thickness
of the sheet is reduced by compression process, the sheet extends
in one direction. In this case, crystal axis <001> is
distributed in high density along extending direction.
[0076] For manufacturing an electrical steel sheet in which axes of
easy magnetization <001> are distributed in parallel in a
surface of the sheet, an Fe-Si alloy, which includes at least Si
and Fe remaining and unavoidable impurities, is heated in a
temperature range in which the alloy becomes solid solution having
body-centered cubic (BCC) structure. In this condition, the solid
solution having the body-centered cubic (BCC) structure is
processed by the uniaxial compression process or the plane strain
compression process with a strain rate which can maintain a process
condition which the movement of dislocation dragging the solute
atmosphere generated in the BCC solid solution becomes main
deformation mechanism, and the grain boundary of the crystal can
migrate by the strain energy stored in the crystal grain as a
driving force. Thereby, the crystal plane {100} is distributed in
high density in parallel to the work surface.
[0077] For the process condition, the temperature range is between
800-1300.degree. C., and the strain rate is between
1.times.10.sup.-5-1.times.10.sup.-1/s.
[0078] The total amount of strain applied on the solid solution
having body-centered cubic (BCC) structure by compression process
is more than -0.5 as a true strain. The purposed condition is
simply widened according to increasing amount of strain, but is not
enough when the amount of strain is small. Larger amount of strain
generates better condition, so that amount of strain is not
upper-limited, and also, the strain can be applied
divisionally.
[0079] Regarding components of the alloy, Si in the solid solution
having body-centered cubic (BCC) structure is added to increase
specific resistance of the steel sheet and decreases eddy current,
and improve core loss by the eddy current. The solid solution
having body-centered cubic (BCC) structure can be BCC single phase
solid solution which is formed by not only binary alloy, but also
ternary or more alloy including a component other than Si. In case
that the solid solution having body-centered cubic (BCC) structure
is Fe-Si alloy, content of Si is in range between 1-7 weight %.
When the content of Si is not larger than 1 weight %, the alloy
cannot have enough specific resistance for low core loss. When the
content of Si is more than 7 weight %, crack is increased in
compression process, so that compression process becomes
troublesome. Content of Si is preferably between 1 weight % at the
lowest and 7 weight % at the highest.
[0080] As unavoidable impurities in the Fe-Si alloy, C, Mn, P, S,
Al and N are listed. Especially, Mn reacts with S to each other so
as to extract fine sulfide MnS and deteriorates extremely magnetic
properties. And P inhibits manufacturability. Thereby, Mn and P
should be controlled less than 0.01 weight %. S, which inhibits
growing crystal grain, should be controlled less than 0.0001 weight
%.
[0081] Fe-Si alloy, which is used as the solid solution having the
body-centered cubic (BCC) structure, is heated in temperature range
between 800-1300.degree. C. to become BCC single phase. Fe-Si alloy
having Si content of 2-5 weight % has BCC structure always in
temperature range from a low temperature to melting point. Fe-Si
alloy having Si content less than 2 weight % changes once to FCC
structure in high temperature according to the content of Si, so
that growing of fiber texture {100} may be inhibited. For solving,
Fe-Si alloy having Si content less than 2 weight % is heated in
lower temperature area in the temperature range between
800-1300.degree. C. to become BCC single phase.
[0082] The strain rate in compression process for BCC single phase
solid solution shows amount of strain per unit time, that is
process speed. The process speed, which is low or high, changes
main mechanism controlling movement of dislocation affecting the
deformation. Therefore, the process speed is limited so as to
maintain the process condition, in which solute atmosphere
generated in the BCC solid solution controls the motion of
dislocation in temperature range of heating solid solution having
the body-centered cubic (BCC) structure so as to be BCC single
phase. The strain rate of Fe-Si alloy as the solid solution having
body-centered cubic (BCC) structure is determined between
1.times.10.sup.-5-1.times.10.sup.-1/s in the temperature range
between 800-1300.degree. C.
[0083] The texture of Fe-Si alloy having Si content of 3 weight %
was evaluated in strain rate range between
1.times.10.sup.-5-1.times.10.sup.-2/s in the temperature
900.degree. C., and in strain rate range between
1.times.10.sup.-4-1.times.10.sup.-2/s in the temperature
1250.degree. C. It is assumed that when the strain rate is the
same, the temperature in process condition, which the same crystal
structure is generated, is changed to lower according to increasing
Si content; and when the temperature is the same, the strain rate
in process condition, which the same crystal structure is
generated, is changed to higher according to increasing Si content.
The above strain rate of Fe-Si alloy is determined about uniaxial
compression process in the above range of Si content and the
temperature range based on the above assumption.
[0084] <Embodiment>
[0085] The solid solution having body-centered cubic (BCC)
structure as a material is formed by steps of hot rolling (heating
temperature 1100.degree. C.times.60 minutes and finish temperature
higher than 850.degree. C.) a 40 Kg ingot made by vacuum melting
into 40 mm thick, cutting that into 320 mm length, hot rolling that
(heating temperature 1100.degree. C.times.60 minutes and finish
temperature higher than 850.degree. C.) into 20 mm thick, cutting
into a plate of 20 mm thick, 140 mm wide, 290 mm length, and
forming that into a cylindrical steel piece with round
cross-section of 12 mm diameter and 18 mm height by
electro-discharge machining.
[0086] The ingots A, B, C and D are formed to have Si of 1.5, 3, 4,
and 5 weight %; Mn and P less than 0.01 weight %, and S less than
0.01 weight % as unavoidable impurities. The four materials A, B, C
and D include C, Al and N of weight % shown in Table 1 as
unavoidable impurities other than Mn, P and S by knowing a content
by composition analysis after process shown in Table 1.
TABLE-US-00001 TABLE 1 C Si Mn P S Al N A 0.0012 1.56 <0.01
<0.01 <0.0001 0.037 0.0009 B 0.0014 3.00 <0.01 <0.01
<0.0001 0.036 0.001 C 0.0013 3.95 <0.01 <0.01 <0.0001
0.037 0.0009 D 0.0018 4.86 <0.01 <0.01 <0.0001 0.036
0.0009
[0087] Each of the above content steel pieces heated at 900.degree.
C. or 1250.degree. C. in a heat furnace is formed into a steel
piece with 20 mm diameter and 6.6 mm height at strain rate range
between 1.times.10.sup.-5-5.times.10.sup.-2/s to have true strain
of -1.0% by uniaxial compression process, and the steel piece is
cooled gradually in room temperature air.
[0088] Cross-head speed constant function of a tension tester
having load capacity of 2 ton shown in FIG. 7 (Shimazu Autograpgh
as trademark) is used for uniaxial compression process. For
compression process by the tension tester, a cylindrical
compression jig is arranged upside and downside the tester, and the
steel piece is provided between the compression jigs, and load is
applied from upside and downside. For maintaining constant
temperature during compression process, the upper and lower jigs
and the steel piece are arranged in the heat furnace. In FIG. 7,
the heater is illustrated as a heater.
[0089] An electrical steel sheet manufactured from the above
material B selected from the above steel pieces, which includes Si
content 3 weight % and is processed by strain rate
5.0.times.10.sup.-5/s in the temperature 900.degree. C., is divided
into a disk-shape measurement sample having 20 mm diameter and 3.3
mm height as a half height. A divided surface is polished and
measured about distribution of orientation of crystal by Schulz
Reflection Method as X-ray diffraction analysis, and thereby,
crystal Orientation Distribution Function (ODF) is given.
Physically, {100} pole figure, {110} pole figure and {211} pole
figure are drawn by data measured respectively by Schulz Reflection
Method, and then, the crystal Orientation Distribution Function
(ODF) showing three dimensional crystal orientation distribution is
calculated by a computer.
[0090] FIG. 1 is a .phi..sub.2=0.degree. section view of ODF given
by computer calculation for describing three pole figures with no
discrepancies. In FIG. 1, .PHI., .phi..sub.1, .phi..sub.2 are Euler
angles. Contour lines along an upper side and a lower side of a
quadrangle show a distribution of the crystal orientation density
in the surface of steel sheet. A value of the contour line shows
orientation density indicated by a multiple about an average value
as 1. In FIG. 1, the contour lines of value 18, 16, 14, 12, 10, 8,
6, 4 are drawn in order between the contour line of value 20 and
the contour line of value 1. At a line of .PHI.=0.degree. as a top
area in FIG. 1, concentration over value 14 is found even at a
lowest area. High density {100} fiber texture is formed therein.
The value is an excellent value much more than a value of usual
non-oriented electrical steel sheet shown in FIG. 2.
[0091] FIG. 2 is a view of .phi.2=0.degree. section of popular one
of usual non-oriented electrical steel sheet made by prior art. In
FIG. 2, orientation density along an upper side is between 0.5-2.0,
so that it can be found that there is almost no texture.
[0092] In the embodiment, crystal orientation distribution of the
material before processing is not described. By increasing amount
of strain for any material in any condition before processing, the
{100} fiber texture, in which {100} is arranged in parallel to the
work surface, is formed by hot compression process. Any steel
material having the same crystal orientation distribution as the
usual non-oriented electrical steel sheet can be applied. The
material in the above embodiment is formed into a round
cross-section, but, the material can be a plate or cylinder having
a rectangular or polygonal cross-section other than round shape.
The surface processed by uniaxial compression process can have any
shape other than a flat surface by the same reason.
[0093] The structure of the direction of easy magnetization in a
motor which is main application of the electrical steel sheet will
be physically described. A disk-shaped stator material is punched
to cut off a central area and slits. Therefore, properties of poles
16 in FIG. 4 are important for a stator material.
[0094] FIG. 12 shows a model of BCC structure. The BCC structure
has symmetry about Up-down and right-left. Axes [100], [010] and
[001] shown in FIG. 12 are equivalent, and general term for the
three axes is shown by <001>. All surfaces of a cubic are
equivalent and surfaces {001}, {100} and {010} are the same.
[0095] The directions of easy magnetization of the usual
non-oriented electrical steel sheet for a stator of a motor are
shown in FIG. 13A. In the usual electrical steel sheet, directions
of easy magnetization direct at any angle three-dimensionally. In
FIG. 13B, directions of easy magnetization in an almost ideal
electrical steel sheet are shown.
[0096] Distribution of directions of easy magnetization <001>
by {100} pole figure is shown in FIGS. 14A and 14B. FIG. 14A shows
distribution of <001> of the usual non-oriented electrical
steel sheet. FIG. 14B shows distribution of <001> of the
electrical steel sheet according to the present invention. Values
in the figures show concentration ratio of orientation density
<001> about average value 1.
[0097] In the usual non-oriented electrical steel sheet, the
smallest value at an outer area much affecting the properties is
not larger than 0.8 times of an average value. In contrast, in the
pole figure of the electrical steel sheet shown in FIG. 14B
according to the present invention, the smallest value at the outer
area is not less than 1.6 multiple of the average value, and the
value at central area is more than 19 multiple of the average
value. Thus, <001> density at the outer area becomes larger
than that of usual material by prior art.
[0098] FIG. 15 shows a magnetic property of the electrical steel
sheet according to the present invention. A magnetic property of
usual non-oriented electrical steel sheet is shown with a dot line
in FIG. 15, and a magnetic property of the electrical steel sheet
according to the present invention is shown with a solid line in
FIG. 15. Undoubtedly, according to the present invention, larger
magnetic flux density about added magnetic field is generated, so
that it is expected that properties of an electromagnetic device
such as a motor can be improved.
[0099] In the embodiment, example of processing single material by
uniaxial compression process is shown. For mass production, sheets
by overlapping various materials can be simultaneously processed by
compression process by a compression machine having larger load
capacity. Also, sizes of material can be increased.
[0100] When the above process condition is fulfilled, distribution
of {100} in parallel to the steel sheet can be resulted also by the
plane strain compression process shown in FIGS. 8A-8D as a method
of compression process.
[0101] For mass production, the rolling process shown in FIG. 9 can
be applied. According to one-direction rolling shown in FIG. 9,
crystal plane {100} grows in parallel to roll surface, so that the
sheet, in which many crystal axes <001> are distributed along
rolling direction, can be given. According to multi-directions
rolling shown in FIG. 10, many crystal axes <001> are
distributed in many directions in the surface of sheet. Thus, the
same effects of uniaxial compression process can be give.
[0102] A wire-shaped metal material can be formed by passing a row
material through a die as shown in FIG. 11 under heat condition.
<001> of the material are aligned along a drawing direction,
so that when magnetic flux flows along the drawing direction, good
magnetic property can be given.
[0103] By increasing amount of strain, a thinner electrical steel
sheet can be formed. Magnetic properties of the electrical steel
sheet formed as mentioned above become further better. The process
is operated in high temperature, so that the amount of lattice
defect remained after process is small, and non-oriented electrical
steel sheet, in which amount of lattice defect is more reduced, can
be given by adding short time anneal after the process.
[0104] In the embodiment, Fe-Si alloy as electromagnetic material
is exampled. The present invention can applied to all metallic
material which can be processed in condition of body-centered.
cubic (BCC) structure by hot compression process. According to the
present invention, a metallic material, in which {100} grows in
parallel to a work surface by hot compression process, can be
formed.
Industrial Applicability
[0105] According to the present invention, a method of
manufacturing process for a metallic material such as an
electromagnetic material, in which orientation of crystal axis is
controlled, is determinated, so that an electromagnetic material
having good properties is provided, and energy loss of
electromagnetic act is increased, and cost down can be performed
and support environmental problems.
Remarks
[0106] 10 Stator of a motor
[0107] 12 Yoke
[0108] 14 Slot
[0109] 16 Pole
[0110] 18 Coil
[0111] 20 Rotor of a motor
[0112] 31 Core
[0113] 32 Coil
[0114] 33 Magnetic lines of force
* * * * *