JP3374672B2 - Process-induced transformation of austenitic stainless steel and method of producing magnetic member - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a process-induced transformation method for austenitic stainless steel, and a method for manufacturing a magnetic member and a composite magnetic member.

[0002]

2. Description of the Related Art At present, austenitic stainless steel is
It is used in various fields from railway cars to household kitchen appliances, and its mechanical properties are very important. For this austenitic stainless steel, Ms
From the austenite phase, which is the parent phase, by performing cold working in the temperature range above the point (upper limit temperature where martensite is generated by constant temperature transformation) and below Md point (upper limit temperature where martensite is generated by work-induced transformation) It is known that a martensite phase is generated to cause work-induced martensite transformation. The austenite phase is the fcc phase (face-centered cubic phase), while the work-induced martensite phase is mostly composed of the bcc phase (body-centered cubic phase) α'martensite phase, and only slightly hc.
A p-phase (dense hexagonal phase) ε ′ martensite phase is included. Hereinafter, unless otherwise limited, the work-induced martensite phase refers to the above α ′ martensite phase.

[0003]

[Problems to be Solved] When this work-induced martensite transformation occurs, the hardness and brittleness may increase and the mechanical properties may change due to the increase in the amount of work-induced martensite formation. However, the crystal structure of the austenite phase and the work-induced martensite phase are different as described above. Therefore, the austenite phase and the processing-induced martensite phase have large differences in their magnetic properties, such as the former being a non-magnetic material and the latter being a ferromagnetic material.

Therefore, when austenitic stainless steel is used as a magnetic member or a composite magnetic member as described later, it is extremely effective to increase the ratio of ferromagnetic work-induced martensite phase. On the other hand, for example, JP-A-7-11397 and JP-A-8-
In the conventional manufacturing method disclosed in Japanese Patent No. 3643, etc., the magnetic flux density B ₄₀₀₀ (strength of 4000 A
The magnetic flux density when a magnetic field of / m was applied) could not be set to a ferromagnetic level of 0.8 T (tesla) or higher.

This means that the strain amount that can be applied to the magnetic member or the composite magnetic member is limited by the breaking limit of the material and the member shape, but even if the maximum strain amount is given by the conventional cold working method, the work-induced martensite is applied. This is probably because the site generation rate is still low. Therefore, a method for positively producing the above-mentioned process-induced martensite in a large amount, that is,
It has been required to develop a method for increasing the amount of work-induced martensite formation with respect to the amount of strain applied.

[0006] Further, as a basic research on the work-induced transformation method, for example, the 1995 plastic working spring lecture (199
Various studies have been conducted, such as "Work-induced transformation of SUS304 in various stress states" reported in 5.5.18 to 20). However, even in these studies, it has not been clarified how to generate the work-induced martensite at a high ratio.

The present invention has been made in view of the above-mentioned conventional requirements, and in the austenitic stainless steel,
An object of the present invention is to provide a process-induced transformation method capable of generating a process-induced martensite at a high ratio, and a method for producing a magnetic member or a composite magnetic member having excellent ferromagnetic properties.

[0008]

According to the invention of claim 1, a material of austenitic stainless steel has a Ms point or more and M or more.
A method for performing a work-induced transformation of an austenite phase into a work-induced martensite phase by performing cold working in a temperature range of point d or lower, wherein the cold working is biaxial tensile working. It is a method of work-induced transformation of austenitic stainless steel.

What is most noticeable in the present invention is to perform biaxial tensile working as the cold working. This biaxial tension processing is, for example, bulge processing, in which tensile stress in different biaxial directions is applied to extend the material in these tensile stress directions and to make 90 ° in both tensile directions. The process of shrinking the material in the intersecting direction.

As the above-mentioned biaxial tension processing, in addition to the above bulge processing (including various methods using a die, hydraulic pressure, rubber die, roller, etc.), expand molding, electromagnetic molding (explosion molding), incremental molding There is forming etc. Further, the number of biaxial tension processes may be once or plural times depending on the purpose. Further, different processing methods may be combined and performed a plurality of times.

Further, the above-mentioned biaxial tensile working is carried out within a temperature range from the Ms point to the Md point of the material. When the temperature is lower than the Ms point, martensite occurs due to the isothermal transformation that occurs simply by lowering the temperature without adding processing, and there is a problem that the processing-induced martensite cannot be generated at a high ratio. On the other hand, when the temperature exceeds the Md point, there is a problem that the processing-induced martensite does not occur only by adding strain to the austenite phase.

Next, the operation of the present invention will be described. In the work-induced transformation method for austenitic stainless steel of the present invention, biaxial tensile working is performed as the cold working.
Therefore, the work-induced martensite generation rate can be significantly increased as compared with, for example, uniaxial or biaxial compression processing or uniaxial tensile processing (see Embodiment 1).

The reason for this is considered as follows. That is, the work-induced martensite phase is bcc as described above.
Since it contains a phase, it has a larger volume per unit weight than the austenite phase of the fcc phase. Therefore, the work-induced martensitic transformation is a transformation accompanied by an increase in volume. On the other hand, there are various forms of cold working that cause work-induced transformation, and the above-mentioned biaxial tensile working can be said to be a working method in which stress is applied in the direction of increasing the volume of the material most.

Therefore, in the present invention, the role of the biaxial tensile working not only as a cold working for merely causing the work-induced transformation but also for promoting the volume increase accompanying the transformation from the austenite phase to the work-induced martensite phase. Fulfill. Therefore, it is considered that the present invention can significantly increase the work-induced martensite generation rate as compared with the case of other cold working such as compression working.

Therefore, according to the present invention, it is possible to provide a work-induced transformation method capable of producing a high ratio of work-induced martensite in austenitic stainless steel.

Next, there is the following invention as a method for producing a magnetic member having excellent ferromagnetic properties by using the above-described work-induced transformation method of austenitic stainless steel. That is, as in the invention of claim 2, a material made of austenitic stainless steel is used, and the material has a Ms point or more and M or more.
A method for producing a magnetic member by subjecting a non-magnetic austenite phase to a work-induced martensite phase that is ferromagnetic by cold-working in a temperature range of point d or lower, wherein the cold working is , There is a method of manufacturing a magnetic member, which is characterized by biaxial tension processing.

The present invention is intended to manufacture a magnetic member having excellent ferromagnetic properties by utilizing the physical property that the processing-induced martensite phase is a ferromagnetic material. That is, transforming the austenite phase into the work-induced martensite phase and transforming the non-magnetic material into the ferromagnetic material are
Physically it is synonymous. Therefore, the present invention and the invention of claim 1 above are substantially the same.

Therefore, according to the present invention, by performing the biaxial tensile working as the cold working, the work-induced martensite is produced at a high ratio by the same effect as in the case of the invention of claim 1. You can Therefore, a magnetic member having excellent ferromagnetic properties can be easily obtained. Therefore, if the composition of the above material and the amount of strain due to biaxial tension processing are properly selected, for example, the magnetic flux density B
It is possible to obtain a magnetic member having extremely excellent ferromagnetic properties such that ₄₀₀₀ reaches 0.8 T or more (see Embodiment 3).

Next, utilizing the above-mentioned invention of claim 2,
There is the following invention as a method of manufacturing a composite magnetic member. That is,
As in the invention of claim 3, by using a material made of austenitic stainless steel and subjecting the material to cold working in a temperature range of the Ms point or more and the Md point or less, the non-magnetic austenite phase is strengthened. A ferromagnetic part is formed by processing-induced transformation into a magnetic processing-induced martensite phase,
Then, a method for producing a composite magnetic member having the ferromagnetic portion and the non-magnetic portion continuously by forming a non-magnetic portion of an austenite phase by heating a part of the ferromagnetic portion into a solution. There is a method of manufacturing a composite magnetic member, wherein the cold working is biaxial tensile working.

What is most noticeable in the present invention is that the above-mentioned biaxial tensile working is performed to generate a processing-induced martensite to form a ferromagnetic part, and then a part of the ferromagnetic part is heated to a solution. Forming a non-magnetic portion.

The above-mentioned heat solution treatment is a treatment in which only a portion where the nonmagnetic portion is to be formed is heated above the austenite transformation temperature. Means for heat solution treatment include, for example, induction annealing and laser processing. In addition, the solution heating is 10
It is preferable to carry out in a short time within seconds. As a result, the austenitized crystal grain size can be reduced to 30 μm or less, and the relative permeability can be sufficiently reduced. On the other hand, when the solution heating is performed for more than 10 seconds, there is a problem that the austenitized structure is coarsened.

Here, the composite magnetic member refers to a member having a ferromagnetic portion and a non-magnetic portion continuously in one member as described above. Since this composite magnetic member does not require a joining portion between the ferromagnetic portion and the non-magnetic portion, it can be used as a magnetic circuit member that is very excellent in terms of durability and manufacturing cost. Therefore, as shown in the above-mentioned prior art, various manufacturing methods of composite magnetic members have been disclosed so far. The present invention is intended to provide a method for manufacturing a composite magnetic member having a ferromagnetic portion, which is more excellent in ferromagnetic properties than the conventional method.

Next, the operation of the present invention will be described. In the method for manufacturing the composite magnetic member of the present invention, biaxial tension processing is used as the means for forming the ferromagnetic portion. for that reason,
As described above, the processing-induced martensite generation rate is significantly higher than that of other processing methods. Therefore, it is possible to obtain a ferromagnetic part having excellent ferromagnetic properties.

That is, as in the case of the second aspect of the invention, the ferromagnetic portion can be made to have, for example, a magnetic flux density B by appropriately selecting the composition of the material and the strain amount due to the biaxial tensile working.
It is possible to obtain extremely excellent ferromagnetic properties such that ₄₀₀₀ reaches 0.8 T or more (see Embodiment 3).

Further, in the present invention, a part of the ferromagnetic portion which has been made ferromagnetic as described above is heated into a solution. As a result, a part of it easily returns to the austenite phase and becomes a nonmagnetic part. Therefore, according to the present invention, it is possible to easily manufacture a composite magnetic member in which a ferromagnetic portion having extremely excellent ferromagnetic properties and a non-magnetic portion are continuously formed in one member.

Next, as in the invention of claim 4, as the cold working, it is preferable to further perform uniaxial or biaxial compression working after the biaxial tensile working. In this case,
It is possible to increase the total amount of strain that can be applied to the above material, and to obtain a ferromagnetic part having excellent ferromagnetic properties. That is, the amount of work-induced martensite generally increases as the total amount of cold working strain increases. Therefore, it is very effective to add a compression process that can take a relatively large amount of strain after a biaxial tensile process that can take only a relatively small amount of strain.

Examples of the uniaxial or biaxial compression processing include spinning, swaging, drawing with a die, rolling, cold forging, ironing with a die, drawing, extrusion and die. There are bending methods using molds and other processing methods. The number of uniaxial or biaxial compression processes may be once or plural times depending on the purpose. Further, different processing methods may be combined and performed a plurality of times.

Further, as in the fifth aspect of the present invention, it is preferable that the cold working is divided into multiple stages and performed plural times .
As a result, the temperature rise of the material due to cold working can be suppressed, and cold working in the temperature range of the Ms point or more and the Md point or less can be easily realized.

Further, as in the sixth aspect of the invention, the cold working can be performed while forcibly cooling the material.
Also in this case, cold working can be realized in the temperature range from the Ms point to the Md point.

According to the invention of claim 7, in the above material, C is 0.6% or less and Cr is 12 to 1 by weight.
9%, Ni 6-12%, Mn 2% or less, Mo 2%
Below, Nb is 1% or less, and the balance is composed of Fe and unavoidable impurities, and the Hirayama equivalent Heq = [Ni%]
+1.05 [Mn%] +0.65 [Cr%] +0.35
[Si%] + 12.6 [C%] is 20 to 23%,
And nickel equivalent Nieq = [Ni%] + 30 [C
%] + 0.5 [Mn%] is 9 to 12%, and chromium equivalent Creq = [Cr%] + [Mo%] + 1.5
[Si%] + 0.5 [Nb%] is preferably made of an austenitic stainless steel having a composition of 16 to 19%.

The reason why C is set to 0.6% or less in the composition of the above-mentioned material is that if it exceeds 0.6%, the amount of carbide increases and the workability decreases. Also, the amount of Cr is 12 to
The content of Ni is set to 19% and the amount of Ni is set to 6 to 12% because the relative magnetic permeability is μ = 1.
This is because the magnetic flux density B ₄₀₀₀ does not show 0.3 T or more when the upper limit value is exceeded. Further, when Mn exceeds 2%, there is a problem that molding performance is deteriorated.

Further, Mo and Nb are not necessarily added, but Mo has an effect of lowering the Ms point, and Nb has an effect of increasing the material strength. Therefore, Mo or Nb may be added alone or in combination depending on the purpose. You can Where Mo is 2%
%, And if Nb exceeds 1%, the workability decreases, so the upper limits of the amounts of Mo and Nb added are preferably 2% and 1%, respectively.

As described above, not only the composition range of each element is limited, but also the combination within these composition ranges can surely obtain excellent magnetic characteristics. That is, when the equivalent Heq of Hirayama is less than 20%, there is a problem that the relative permeability μ = 1.2 is exceeded and sufficient non-magnetic characteristics cannot be obtained. On the other hand, when it exceeds 23%, there is a problem. There is a problem that it is difficult for the magnetic flux density B ₄₀₀₀ to exceed 0.3T.

For the same reason as the case of the Hirayama equivalent, the ranges of the nickel equivalent Nieq and the chromium equivalent Creq are 9 to 12% and 16 to 1, respectively.
The range was 9%. Here, the material usually contains 2% or less of Si and 0.5% or less of Al as deoxidizing elements, and other impurity elements, but these do not impair the characteristics of the composite magnetic member. .

[0035]

DETAILED DESCRIPTION OF THE INVENTION

First Exemplary Embodiment A method for processing-induced transformation of austenitic stainless steel according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 to 3. The work-induced transformation method of the austenitic stainless steel of this example is such that a material made of austenitic stainless steel is cold-worked in a temperature range from the Ms point to the Md point to transform the austenite phase into a martensite phase. This is a method of causing work-induced transformation. The cold working in this example is biaxial tensile working.

In the present example, in order to confirm the effect of the present invention, two kinds of materials are prepared, and various cold workings are added to the raw materials to measure the amount of work-induced martensite formation. I investigated the effect of. As the cold working method,
As in the model shown in FIG. 3, four types of methods, biaxial tension (A), uniaxial tension (B), uniaxial compression (C), and biaxial compression (D) were performed. The prepared material is SUS30.
There are two types, 1 and SUS304. Table 1 shows each chemical component.

SUS301 was made of a plate material having a thickness of 1 mm, and SUS304 was made of an ingot. In addition, in SUS301, the plate materials were overlapped, the plate materials were joined by a thermal diffusion method, processed into a block material, and then subjected to finish heat treatment to fabricate test pieces for uniaxial compression and biaxial compression.

Each of the test pieces processed into the required shape had a vacuum degree of 10 ⁻³ Pa and a temperature of 1373 K for a time of 7.2.
A solution heat treatment was performed by holding for ks. However,
The uniaxially compressed piece and the biaxially compressed piece of SUS301 were subjected to solution heat treatment by holding for a total time of 5.8 ks for convenience of joining and finishing. As a result, the same crystal grain size No. 6 was obtained for all the test pieces, and it was possible to manufacture the test pieces that did not need to consider the particle size dependence due to the difference in the particle size between the test pieces.

[0039]

[Table 1]

Next, a test method for performing each cold working will be described. In the uniaxial tensile test, the width W as a tensile test piece
= 10 mm, gauge length L = 40 mm, parallel part length P =
60 mm, shoulder radius R = 10 mm, and thickness T = 1 m
A JIS Z2201 No. 13B test piece reduced to m was used. And, with INSTRON universal testing machine, the maximum strain of SUS301 is equivalent strain ε = 0.445, SUS
304 gave strain up to equivalent strain ε = 0.281.

In the uniaxial compression test, a cubic test piece having a side length of 15 mm was used as the compression test piece. And
With a hydraulic compression tester, the maximum equivalent strain for SUS301 is ε = 1.000, and the equivalent strain for SUS304 is ε =
Strain was applied to 0.910 with repeated lubrication.

In the biaxial tensile test, a disc-shaped test piece having a diameter of 90 mm and a plate thickness of 1 mm was used as an overhanging test piece for the biaxial tensile test. Then, a bulging test is performed using a deep drawing tester, and the maximum equivalent strain SUS301 is ε = 0.20.
4, SUS304 was strained to an equivalent strain ε = 0.163, and an equibiaxial tensile test was conducted.

In the biaxial compression test, a cubic test piece having the same side length of 15 mm as the test piece used in the uniaxial compression test was used. Then, using a biaxial compression tester that is a combination of a hydraulic compression tester and a device that applies a horizontal load using a stepping motor, a maximum of SUS301
Is equivalent strain ε = 0.157, and SUS304 is equivalent strain ε = 0.176, and equibiaxial compression test was performed. All the above tests were carried out at an ambient temperature of 300 K and at a strain rate of 10 ⁻³ / s so as not to cause a temperature rise due to deformation heat. As a result, the temperature of the test piece is kept within the temperature range above the Ms point and below the Md point during the test.

The martensite phase is quantified by Fish
er Ferritescope. In addition, polycrystalline X-ray diffraction was performed in order to check the validity of the quantitative values of the crystal structure of austenite and martensite and the martensite phase. At this time, as the X-ray source, Co-
Ka radiation was used.

Next, the results of the above tests are shown in FIGS. 1 and 2, the horizontal axis represents the equivalent strain and the vertical axis represents the amount of work-induced martensite formation (%). And biaxial tension is E11, E12, uniaxial tension is C12, C
22, uniaxial compression is C13, C23, biaxial compression is C14,
Shown by C24. FIG. 1 relates to SUS301, and FIG. 2 relates to SUS304.

As is known from FIGS. 1 and 2, it is understood that, in any of the components, the work-induced martensite was produced at a higher ratio in the case of the biaxial tensile working than in the case of the other working methods. That is, in this example, it is found that the work-induced martensite is easily generated in the order of biaxial tension, uniaxial tension, uniaxial compression, and biaxial compression. This indicates that the production rate of work-induced martensite increases as the amount of strain increases in any of the processing methods, but it increases even further in the processing method in which the material is strongly stressed in the volume increasing direction. ing.

In this example, _{SUS301 was} evaluated based on Ni equivalent of Hirayama et al. And M _d30 (K) of Nohara et al. Although the work-induced transformation was easier than that of SUS304, SUS304 resulted in a larger amount of work-induced martensite formation. This is due to the difference in the carbon (C) content in SUS301 and SUS304 of this example (see Table 1), and S with a large carbon content
It is considered that US301 requires more transformation driving force.

Embodiment 2 In this embodiment, in order to further support the evaluation result of Embodiment 1, the effect of hydrostatic stress on the formation of work-induced martensite was examined. That is, the single axis in the first embodiment,
The relationship between the hydrostatic stress at the equivalent strain of about 0.1 and the work-induced martensite formation rate in the above-mentioned four types of biaxial tension and compression tests was determined. Figure 4 shows SUS301
FIG. 5 is for SUS304.

The data shown in FIGS. 4 and 5 are arranged in the order of biaxial tension, uniaxial tension, uniaxial compression, and biaxial compression from the side having the higher hydrostatic stress. Therefore, in FIG.
As is clear from Fig. 5, the production rate of work-induced martensite increases in the order of biaxial tension, uniaxial tension, uniaxial compression, and biaxial compression.

Therefore, according to this example, the greater the hydrostatic stress, the more easily the work-induced martensitic transformation occurs,
It can be seen that the biaxial tensile working is very advantageous for the work-induced transformation.

Embodiment 3 Next, a method of manufacturing a composite magnetic member according to an embodiment of the present invention will be described with reference to FIGS. The composite magnetic member 1 manufactured in this example has the following structure as shown in FIG.
A cylindrical composite magnetic member having a non-magnetic portion 3 in the upper half portion and a ferromagnetic portion 2 in the lower half portion. In manufacturing the same, as shown in FIG. 6, a disc-shaped material 10 made of austenitic stainless steel is used.

Then, as shown in FIGS. 7 to 9, the material 1
By performing cold working in the temperature range from the Ms point to the Md point to 0, the nonmagnetic austenite phase is transformed into the ferromagnetic martensite phase by the work-induced transformation to form the ferromagnetic portion 2. Next, as shown in FIG. 10, a part of the ferromagnetic portion 2 is heated to a solution to form a non-magnetic portion 3 of austenite phase.

Thus, as shown in FIG. 11, the composite magnetic member 1 having the ferromagnetic portion 2 and the non-magnetic portion 3 continuously is manufactured. Further, as the cold working in this example,
After biaxial tension processing, uniaxial or biaxial compression processing is further performed.

This will be described in detail below. First, the material 10 to be prepared is a disk-shaped blank material as shown in FIG. 6, and is austenitic stainless steel having the chemical components shown in Table 2. Further, the material 10 is composed of a nonmagnetic austenite phase as a whole.

[0055]

[Table 2]

Next, as shown in FIGS. 7 to 9, the non-magnetic material 10 is subjected to cold working for causing work-induced transformation. This cold working is as shown in FIG.
This is a combination of bulge processing as biaxial tension processing and spinning processing as uniaxial compression processing as shown in FIGS. 8 and 9.

Specifically, first, as shown in FIG. 7, a bulge processing apparatus 50 including a punch 51 having a ball head 52 with a radius of 25 mm and a clamp portion 53 for restraining the material 10 is used to remove the material 10. Bulge processing is performed until the intermediate material 11 is overhanged by 16 mm. The equivalent strain at this time is 0.25.

Then, in order to increase the amount of equivalent strain by further performing cold working, as shown in FIGS. 8 and 9, uniaxial compression spinning which allows a high working ratio is used as the intermediate material 11.
Apply to. The intermediate member 11 has the outer peripheral portion, which is constrained by the clamp portion 53 during the bulging process, cut in advance.

Then, as shown in FIGS. 8 and 9, the spinning process is performed by using a spinning device 60 including a forming die 61 and a moving roller 62 which rotate together with the set intermediate material 11. Then, the tip portion 111 of the intermediate member 11
Then, the intermediate roller 11 is subjected to spinning by gradually moving the moving roller 62. The equivalent strain at this time is 0.5, including the above bulge processing.

By performing the bulging process as the biaxial tensile process and the spinning process as the uniaxial compression process in this way, the material 10 has the second ferromagnetic part 3 in which the process-induced martensite is generated. It becomes the intermediate material 12.

Then, as shown in FIG. 10, the tip 121 of the second intermediate member 12 is cut and the high-frequency coil 7 is cut.
The upper half is heated and solution-treated by induction heating within about 10 seconds. As a result, as shown in FIG. 11, the composite magnetic member 1 having the non-magnetic portion 3 in the upper half portion and the ferromagnetic portion 2 in the lower half portion is obtained.

Next, in this example, in order to evaluate the magnetic characteristics of the obtained composite magnetic member 1, the processing-induced martensite generation amount of the ferromagnetic portion 2 and the magnetic flux density B ₄₀₀₀ were measured, and the non-magnetic portion was measured. The relative magnetic permeability of 3 was measured. The method for measuring the amount of processing-induced martensite formation was the same as in Embodiment 1.

The measurement results will be described. First, the amount of processing-induced martensite produced in the ferromagnetic part 2 is 90
% Has been reached. And the magnetic flux density B ₄₀₀₀ reached 1.3T. For comparison, a comparative product was produced in which the equivalent strain of 0.5 was applied by the spinning process of the uniaxial compression process without performing the biaxial tension process. The parts other than cold working were the same as in the method for manufacturing the composite magnetic member of this example. Then, in the ferromagnetic part of the obtained comparative product, the same measurement as above was carried out. As a result, the work-induced martensite production rate was about 65%, and the magnetic flux density B ₄₀₀₀ was 0.6T.

FIG. 12 shows the above relationship. In FIG. 12, the horizontal axis shows the amount of production of martensite induced by machining (%), and the vertical axis shows the ferromagnetic level (magnetic flux density B ₄₀₀₀ ). The ferromagnetic level of the ferromagnetic portion in this example is shown as E3, and the ferromagnetic level of the comparative product is shown as C3. From the figure, even when cold working giving the same equivalent strain of 0.5 is applied, the uniaxial compression processing alone has a low work-induced martensite generation rate and a low ferromagnetism level, but is biaxially tensile worked. It can be clearly seen that, in the case of all the cases where

From these facts, it is understood that the method of this example is extremely effective in improving the magnetic characteristics of the ferromagnetic portion. Further, the relative magnetic permeability in the non-magnetic portion 3 is μ = 1.00 to
It was 1.05, which was a very excellent characteristic.

As described above, in this example, the composite magnetic member 1 having the ferromagnetic portion 2 and the non-magnetic non-magnetic portion 3 which are extremely excellent in the ferromagnetic property in a continuous manner can be easily manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between an equivalent strain and a processing-induced martensite generation amount for each of various processing methods of SUS301 in the first embodiment.

FIG. 2 is an explanatory diagram showing a relationship between an equivalent strain and a processing-induced martensite generation amount for each of various processing methods of SUS304 in the first embodiment.

FIG. 3 (A) Biaxial tension in Embodiment 1;
Explanatory drawing which shows the model of (B) uniaxial tension, (C) uniaxial compression, and (D) biaxial compression.

FIG. 4 is an explanatory diagram showing the relationship between hydrostatic pressure stress of SUS301 and the amount of work-induced martensite formation in the second embodiment.

FIG. 5 is an explanatory diagram showing a relationship between hydrostatic pressure stress of SUS304 and processing-induced martensite generation amount in the second embodiment.

FIG. 6 is a perspective view of a material according to the third embodiment.

FIG. 7 is an explanatory diagram showing bulge processing in the third embodiment.

FIG. 8 is an explanatory diagram showing an initial state of spinning processing according to the third embodiment.

FIG. 9 is an explanatory diagram showing a final state of spinning processing in the third embodiment.

FIG. 10 is an explanatory diagram showing heating solution treatment in the third embodiment.

FIG. 11 is an explanatory diagram showing a composite magnetic member according to the third embodiment.

FIG. 12 is an explanatory view showing the relationship between the amount of processing-induced martensite formation and the ferromagnetism level in the third embodiment.

[Explanation of symbols]

1. ． ． Composite magnetic material, 10. ． ． Material, 11. ． ． Intermediate material, 12. ． ． Second intermediate material, 2. ． ． Ferromagnetic part, 3. ． ． Non-magnetic part,

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keizo Takeuchi 1-1, Showa-cho, Kariya city, Aichi Prefecture, Nippon Denso Co., Ltd. (72) Inventor, Masaki Shimizu 1-1-chome, Showa town, Kariya city, Aichi Nippon Denso Co., Ltd. (72) Inventor Koji Ishikawa 79-1 Inaba, Higashiootomo-cho, Okazaki-shi, Aichi (58) Fields investigated (Int.Cl. ⁷ , DB name) C21D 8/00-8/10 C22C 38/00-38/60

Claims (7)

(57) [Claims] 1. A method of performing work-induced transformation of an austenite phase into a work-induced martensite phase by subjecting a material made of austenitic stainless steel to cold working in a temperature range from the Ms point to the Md point. The cold-working is a biaxial tensile work, which is a process-induced transformation method for austenitic stainless steel. 2. A non-magnetic austenite phase is induced by ferromagnetic processing by using a material made of austenitic stainless steel and subjecting the material to cold working in a temperature range from the Ms point to the Md point. A method for manufacturing a magnetic member by subjecting a martensitic phase to a work-induced transformation, wherein the cold working is a biaxial tensile working. 3. A non-magnetic austenite phase is induced by ferromagnetic processing by using a material made of austenitic stainless steel and subjecting the material to cold working in a temperature range from the Ms point to the Md point. The ferromagnetic part is formed by subjecting the ferromagnetic part to the martensite phase by work-induced transformation, and then a part of the ferromagnetic part is heated to a solution to form the nonmagnetic part of the austenite phase. A method for producing a composite magnetic member, wherein the cold working is biaxial tensile working, the method comprising: 4. The method of manufacturing a composite magnetic member according to claim 3, wherein, as the cold working, uniaxial or biaxial compression working is further performed after the biaxial tensile working. 5. The method for manufacturing a composite magnetic member according to claim 3 or 4, wherein the cold working is divided into multiple stages and performed a plurality of times . 6. The method according to any one of claims 3 to 5,
The method for producing a composite magnetic member, wherein the cold working is performed while forcibly cooling the material. 7. The method according to any one of claims 3 to 6,
In the above materials, the weight ratio of C is 0.6% or less, Cr is 12 to 19%, Ni is 6 to 12%, Mn is 2% or less, and M is
O is 2% or less, Nb is 1% or less, and the balance is composed of Fe and unavoidable impurities, and Hirayama equivalent Heq = [Ni%] + 1.05 [Mn%] +
0.65 [Cr%] + 0.35 [Si%] + 12.6
[C%] is 20 to 23%, and nickel equivalent Nieq = [Ni%] + 30 [C%] +
0.5 [Mn%] is 9 to 12%, and chromium equivalent Creq = [Cr%] + [Mo%] + 1.5
A method for producing a composite magnetic member, which comprises an austenitic stainless steel having a composition of [Si%] + 0.5 [Nb%] of 16 to 19%.