JP7053343B2 - Method for manufacturing Fe-Mn alloy and Fe-Mn alloy - Google Patents

Description

The present invention relates to a method for producing a Fe—Mn alloy and a Fe—Mn alloy.

Patent Document 1 describes a low-density ferroalloy. This low specific gravity iron alloy has Mn: 15.0 to 45.0% by mass, Al: 8.0 to 20.0% by mass, C: 0.01 to 2.5% by mass, Si: 0.01 to 5 by mass. It consists of 0.0% by mass, Cr: 0.01 to 10.0% by mass, B: 0.001 to 1.5% by mass, N: 0.01 to 1.5% by mass, the balance Fe and unavoidable impurities. Further, the low specific density iron alloy is made of an iron alloy having two phases of γ + α having an α phase fraction of 10 to 95%. Further, Non-Patent Document 1 describes a FeMnAl alloy. This FeMnAl alloy has a composition of Fe-29.5Mn-9.2Al-0.94C. When the ^FeMnAl alloy is aged at 550 ° C. for 104 minutes or longer, β-Mn is precipitated.

Japanese Unexamined Patent Publication No. 2005-325387

Ryan A. Howel, "Microstructural influence on dynamic techniques of age hardenable FemnAl Allorys", Doctoral Dissertations, Missouri University of Science, Missouri University of Science. 27-28

However, the low density iron alloy of Patent Document 1 and the FeMnAl alloy of Non-Patent Document 1 have low hardness.

Therefore, an object of the present invention is to provide a Fe—Mn alloy having a high hardness.

The Fe—Mn alloy according to the present invention has a composition of 20.0 to 30.0% by mass of Mn, 5.0 to 10.0% by mass of Al, and 0.5 to 1.5% by mass of C. And 5.0 to 10.0% by mass of Cr, the balance is Fe and unavoidable impurities, and the metal structure contains β-Mn phase and α phase.

The Fe—Mn alloy according to the present invention has a high hardness.

FIG. 1 is a diagram showing a change in Vickers hardness with respect to a processing rate for a Fe—Mn alloy sample. FIG. 2 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. FIG. 3 is a diagram showing the change in Vickers hardness with respect to the processing rate for the Fe—Mn alloy sample. FIG. 4 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. FIG. 5 is a diagram showing the change in Vickers hardness with respect to the processing rate for the Fe—Mn alloy sample. FIG. 6 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. FIG. 7 is a diagram showing an SEM image of the Fe—Mn alloy sample. FIG. 8 is a diagram showing an SEM image of the Fe—Mn alloy sample. FIG. 9 is a diagram showing an SEM image of the Fe—Mn alloy sample. FIG. 10 is a diagram showing an X-ray diffraction pattern of a Fe—Mn alloy sample. FIG. 11A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 11B is an enlarged view of a part of the HAADF-STEM image of FIG. 11A. FIG. 12A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 12B is an enlarged view of a part of the mapping of FIG. 12A. FIG. 13A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 13B is an enlarged view of a part of the HAADF-STEM image of FIG. 13A. FIG. 14A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 14B is an enlarged view of a part of the mapping of FIG. 14A. FIG. 15A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 15B is an enlarged view of a part of the HAADF-STEM image of FIG. 15A. FIG. 16A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 16B is an enlarged view of a part of the mapping of FIG. 16A. FIG. 17A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 17B is a diagram showing an electron diffraction pattern of the Fe—Mn alloy sample. FIG. 17C is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 18 is a diagram showing an electron diffraction pattern of a Fe—Mn alloy sample.

An embodiment (embodiment) for carrying out the present invention will be described in detail. The present invention is not limited to the contents described in the following embodiments. In addition, the components described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Further, various omissions, substitutions or changes of the configuration can be made without departing from the gist of the present invention.

<Fe-Mn alloy>
The Fe (iron) -Mn (manganese) alloy according to the embodiment has Mn of 20.0% by mass or more and 30.0% by mass or less and Al of 5.0% by mass or more and 10.0% by mass or less as a component composition. Aluminum), 0.5% by mass or more and 1.5% by mass or less of C (carbon), and 5.0% by mass or more and 10.0% by mass or less of Cr (chromium), and the balance is Fe and unavoidable impurities. be. Further, the Fe—Mn alloy according to the embodiment contains a β—Mn phase and an α phase (ferrite phase, bcc structure) as a metal structure. The β-Mn phase is a cubic system, a = b = c = 6.34 Å, and the number of atoms in a unit cell is 20.

As described above, the Fe—Mn alloy according to the embodiment has a specific component composition and has a β—Mn phase as a metal structure. Therefore, the Fe—Mn alloy according to the embodiment has high hardness and is excellent in scratch resistance and dent resistance. Further, since the Fe—Mn alloy according to the embodiment also contains an α phase, it is excellent in processability.

On the other hand, the low-density ferroalloy described in Patent Document 1 includes a γ phase (austenite phase, fcc structure) and an α phase. Therefore, it is considered that the hardness is low. Further, the FeMnAl alloy described in Non-Patent Document 1 has a component composition different from that of the Fe—Mn alloy. Further, in Non-Patent Document 1, the FeMnAl alloy is aged at 550 ° C. Here, β ^- Mn is precipitated by the aging treatment for 104 minutes or more. However, since β-Mn only appears as a precipitate, it is considered that the FeMnAl alloy has a low hardness.

Hereinafter, the Fe—Mn alloy according to the embodiment will be described in more detail. The Fe—Mn alloy according to the embodiment contains Mn of 20.0% by mass or more and 30.0% by mass or less. Since Mn is contained in the above amount, a β-Mn phase can be obtained as a metal structure. Therefore, the hardness of the Fe—Mn alloy can be increased.

The Fe—Mn alloy contains Al of 5.0% by mass or more and 10.0% by mass or less. Since Al is contained in the above amount, an α phase is obtained together with the β—Mn phase as a metal structure. In addition, the workability of the Fe—Mn alloy can be improved.

The Fe—Mn alloy contains C of 0.5% by mass or more and 1.5% by mass or less. Since C is contained in the above amount, an α phase is obtained together with the β—Mn phase as a metal structure. In addition, the workability of the Fe—Mn alloy can be improved. If C is more than 1.5% by mass, it may precipitate as carbides such as M ₃ C (M is Fe or Mn).

The Fe—Mn alloy contains Cr of 5.0% by mass or more and 10.0% by mass or less. Since Cr is contained in the above amount, a β-Mn phase can be obtained as a metal structure. Further, Cr mainly exists as a carbide at the boundary between the β—Mn phase and the α phase, and can contribute to the improvement of the hardness of the Fe—Mn alloy.

In the Fe—Mn alloy, the balance is Fe and unavoidable impurities. Inevitable impurities are inevitably mixed from raw materials. Examples of unavoidable impurities include Si (silicon), P (phosphorus), and S (sulfur). Usually, each is contained in an amount of less than 0.01% by mass. It is considered that this amount does not interfere with the effect of the embodiment.

The Fe—Mn alloy according to the embodiment preferably further contains 2.5% by mass or more and 10.0% by mass or less of Ni as a component composition. That is, the Fe-Mn alloy according to the embodiment has a component composition of Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, 0.5% by mass. It contains C of% or more and 1.5% by mass or less, Cr of 5.0% by mass or more and 10.0% by mass or less, and Ni of 2.5% by mass or more and 10.0% by mass or less, and the balance is Fe and unavoidable. It may be an impurity. When Ni is contained in the above amount, the α phase is more preferably obtained as a metal structure, and the hot and / or cold forging workability is improved. In addition, the workability of the Fe—Mn alloy can be improved. Therefore, the balance between the hardness and the strength of the Fe—Mn alloy can be improved.

Further, the Fe—Mn alloy according to the embodiment contains a β—Mn phase and an α phase as a metal structure. The β-Mn phase has a high hardness. Therefore, the Fe—Mn alloy containing such a β—Mn phase has a high hardness. Further, since the Fe—Mn alloy also contains an α phase, the Fe—Mn alloy is excellent in processability. Specifically, at least a part of the β-Mn phase contained in the Fe—Mn alloy is observed as a continuous phase having an area of 1 μm ² or more in the SEM image. In other words, at least a part of the β-Mn phase contained in the Fe—Mn alloy exists not as a fine precipitate but as a continuous phase as described above.

Further, in the Fe—Mn alloy according to the embodiment, the area fraction of the β—Mn phase is 60% or more and 90% or less when the total area fraction of the β—Mn phase and the α phase is 100%. , The area fraction of the α phase is preferably 10% or more and 40% or less. Further, it is more preferable that the surface integral of the β—Mn phase is 70% or more and 90% or less, and the surface integral of the α phase is 10% or more and 30% or less. When the surface integral is within the above range, the balance between hardness and workability can be improved. The area fraction is obtained from the measured values obtained by measuring the areas of the β-Mn phase and the α phase in a region of a specific size (for example, a region of 100 μm × 100 μm) in SEM image observation.

Further, in the above-mentioned region of a specific size, the area fraction of the region other than the β-Mn phase and the α phase (carbide other than the β-Mn phase and the α phase (for example, Cr carbide), the total area of the residual γ phase, etc.). The fraction) is usually 5% or less. If the surface integral of the region other than the β-Mn phase and the α phase is within the above range, it is considered that the effect of the embodiment is not hindered.

For the Fe—Mn alloy according to the embodiment, the crystal grain size is usually 10 μm or less. From the viewpoint of hardness, it is preferable that the crystal grains are in the above range.

For the Fe—Mn alloy according to the embodiment, the Vickers hardness (HV) is usually 400 or more, preferably 500 or more. When the Vickers hardness is within the above range, it is suitably used for applications where scratch resistance and dent resistance are required.

<Manufacturing method of Fe-Mn alloy>
The method for producing an Fe—Mn alloy according to an embodiment includes a hot working step, a cold forging step, and a curing heat treatment step. In the method for producing a Fe—Mn alloy, a hot work piece is manufactured in the hot work process. In the cold forging step, the hot work piece is cold forged to produce a cold forged product having metal crystals into which dislocations have been introduced. This cold forged product contains a γ phase and an α phase as a metallographic structure. In the curing heat treatment step, the cold forged product is subjected to curing heat treatment to produce an Fe—Mn alloy. This Fe—Mn alloy contains a β—Mn phase and an α phase as a metal structure. It is considered that the γ phase is transformed into the β-Mn phase during the curing heat treatment. That is, if dislocations are introduced into the metal crystal by cold forging, it is considered that the transformation from the γ phase to the β-Mn phase occurs in the subsequent curing heat treatment. When the hot work piece is cured and heat-treated as it is, the transformation from the γ phase to the β-Mn phase does not occur.

The hot working step is a step of hot working the ingot to obtain a hot work piece.

The component composition of the ingot is Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, and 0.5% by mass or more and 1.5% by mass or less. It contains C and Cr of 5.0% by mass or more and 10.0% by mass or less, and the balance is Fe and unavoidable impurities. When the ingot has the above component composition, an Fe—Mn alloy having a β—Mn phase can be produced. That is, a Fe—Mn alloy having high hardness can be produced. The ingot may further contain 2.5% by mass or more and 10.0% by mass or less of Ni as a component composition. When the ingot contains Ni in the above amount, the processability of the produced Fe—Mn alloy can be improved.

Further, the ingot contains a γ phase and an α phase as a metal structure. In the ingot, when the total area fraction of the γ phase and the α phase is 100%, the area fraction of the γ phase is 60% or more and 90% or less, and the area fraction of the α phase is 10% or more and 40%. The following is preferable. Further, it is more preferable that the surface integral of the γ phase is 70% or more and 90% or less, and the surface integral of the α phase is 10% or more and 30% or less. When the surface integral is in the above range, transformation to the β-Mn phase in the curing heat treatment is likely to occur.

The ingot is manufactured, for example, by weighing the raw materials so as to have the composition of the above components, dissolving them, and then injecting them into a mold.

Specific examples of the hot working include forging and groove roll rolling, whereby a bar is obtained as a hot working product. Hot working is usually performed at 1100 ° C. or higher and 1250 ° C. or lower. After hot working, it is usually water-cooled.

The processing rate by hot working is preferably 45% or more and 80% or less. In the present specification, the processing rate means the reduction rate of the cross-sectional area. Specifically, it refers to the rate of decrease in the cross-sectional area of the obtained bar with respect to the cross-sectional area of the ingot.

In the hot work piece, the composition and the type and ratio of the metallographic structure are the same as those in the case of the ingot, including the preferable range and the reason. Further, for the hot work piece, the size of crystal grains is usually 10 μm or less. From the viewpoint of the hardness of the finally produced Fe—Mn alloy, it is preferable that the crystal grains are in the above range.

The cold forging step is a step of cold forging the hot work piece obtained in the hot work step to obtain a cold forged product. Cold forging introduces dislocations into the metal crystals of the cold forged product.

Specific examples of the cold forging include swaging, whereby a bar having a narrower outer diameter can be obtained as a cold forging.

The processing rate by cold forging is preferably 20% or more and 80% or less, and more preferably 40% or more and 80% or less. When the processing rate is within the above range, dislocations can be introduced in an amount suitable for the metal crystal. Therefore, the curing heat treatment causes transformation to the β-Mn phase, and the hardness of the finally produced Fe—Mn alloy can be increased.

In the cold forged product, the composition and the type and ratio of the metallographic structure are the same as those of the ingot and the hot work product, including the preferable range and the reason. Further, for the cold forged product, the crystal grain size is usually 10 μm or less. From the viewpoint of the hardness of the finally produced Fe—Mn alloy, it is preferable that the crystal grains are in the above range.

The curing heat treatment step is a step of curing and heat-treating the cold forged product obtained in the cold forging step to obtain an Fe—Mn alloy. The curing heat treatment causes a transformation from the γ phase to the β-Mn phase. As a result, specifically, a rod material of Fe—Mn alloy can be obtained.

The curing heat treatment is preferably performed at 550 ° C. or higher and 800 ° C. or lower, and more preferably 600 ° C. or higher and 700 ° C. or lower. When the temperature of the curing heat treatment is in the above range, the hardness of the finally produced Fe—Mn alloy can be increased. If the temperature of the curing heat treatment is too high, the hardness of the finally produced Fe—Mn alloy may be low. In addition, it can be costly. The curing heat treatment is preferably performed for 10 minutes or more and 12 hours or less. When the curing heat treatment time is within the above range, the hardness of the finally produced Fe—Mn alloy can be increased. If the curing heat treatment time is too long, the strength of the finally produced Fe—Mn alloy may decrease. In addition, it can be costly. After the curing heat treatment, it is usually air-cooled.

The obtained Fe-Mn alloy has a composition of 20.0% by mass or more and 30.0% by mass or less of Mn, 5.0% by mass or more and 10.0% by mass or less of Al, and 0.5% by mass or more and 1 It contains C of 5.5% by mass or less and Cr of 5.0% by mass or more and 10.0% by mass or less, and the balance is Fe and unavoidable impurities. The Fe—Mn alloy may further contain 2.5% by mass or more and 10.0% by mass or less of Ni as a component composition. In the Fe—Mn alloy, the component composition of the ingot is usually maintained. Further, the Fe—Mn alloy contains a β—Mn phase and an α phase as a metal structure. The Fe—Mn alloy thus produced has a specific component composition and has a β—Mn phase as a metal structure. Therefore, the Fe—Mn alloy has high hardness and is excellent in scratch resistance and dent resistance. Further, since the Fe—Mn alloy also contains an α phase, it is excellent in processability.

Further, in the Fe—Mn alloy, the area fraction of the β—Mn phase is 60% or more and 90% or less when the total area fraction of the β—Mn phase and the α phase is 100%, and the α phase. It is preferable that the area fraction of the above is 10% or more and 40% or less. Further, it is more preferable that the surface integral of the β—Mn phase is 70% or more and 90% or less, and the surface integral of the α phase is 10% or more and 30% or less. When the surface integral is within the above range, the balance between hardness and workability can be improved.

Further, for the Fe—Mn alloy, the crystal grain size is usually 10 μm or less. From the viewpoint of the hardness of the Fe—Mn alloy, it is preferable that the crystal grains are in the above range.

In the above method for producing a Fe—Mn alloy, hot working may be performed by hot rolling as long as a desired shape can be obtained. Further, cold rolling may be performed instead of cold forging. Any cold working can be used as long as dislocations can be introduced into the metal crystal.

In the above method for producing a Fe—Mn alloy, a homogenization heat treatment step of homogenizing the ingot may be performed before the hot working. The homogenization heat treatment is performed, for example, at 1000 ° C. or higher and 1200 ° C. or lower for 0.5 hours or longer and 3 hours or shorter. As a result, the structure of the ingot can be made uniform. In this case, in the hot working step, the homogenized heat-treated ingot is hot-worked to obtain a hot-worked product.

In the method for producing a Fe—Mn alloy, after hot working, an annealing step of annealing the hot work product obtained in the hot working step may be performed. Annealing is carried out, for example, at 1000 ° C. or higher and 1200 ° C. or lower for 0.5 hours or longer and 3 hours or shorter. As a result, the structure of the hot work piece can be made uniform. In this case, in the cold forging step, the annealed hot work piece is cold forged to obtain a cold forged product.

In the above method for producing a Fe—Mn alloy, the case of obtaining a bar of the Fe—Mn alloy has been described, but the present invention is not limited to this. A wire rod or plate material of Fe—Mn alloy may be manufactured. In this case, for example, in hot working and cold forging, processing is performed so that wire rods and plate materials can be obtained.

The Fe—Mn alloy having the above-mentioned specific composition and metal structure may be produced by a production method other than the above-mentioned production method of the Fe—Mn alloy. That is, the production method is not limited as long as the Fe—Mn alloy having the above-mentioned specific composition and metal structure can be obtained.

<Use of Fe-Mn alloy>
The Fe—Mn alloy is suitably used for watch members (for example, exterior). Further, the Fe-Mn alloy is also suitably used for transport aircraft such as automobiles, ships and aircraft, machinery, electrical products, buildings, structures, optical instruments, equipment, and members (for example, exteriors) of fittings. Taking advantage of the high hardness of the Fe—Mn alloy, it is suitably used for applications that require sliding resistance, scratch resistance, and dent resistance.

Based on the above, the present invention relates to the following.

[1] As a component composition, Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, 0.5% by mass or more and 1.5% by mass or less. Fe-Mn alloy containing C and 5.0% by mass or more and 10.0% by mass or less of Cr, the balance being Fe and unavoidable impurities, and containing β-Mn phase and α phase as a metal structure.
The Fe—Mn alloy has a high hardness.
[2] When the total area fraction of the β-Mn phase and the α phase is 100%, the area fraction of the β-Mn phase is 60% or more and 90% or less, and the area fraction of the α phase is 10. % Or more and 40% or less, the Fe—Mn alloy according to the above [1].
When the surface integral is in the above range, the Fe—Mn alloy can improve the balance between hardness and workability.
[3] The Fe—Mn alloy according to the above [1] or [2], further containing 2.5% by mass or more and 10.0% by mass or less of Ni as the component composition.
When Ni is contained in the above amount, the balance between the hardness and the strength of the Fe—Mn alloy can be improved.
[4] A hot working step of hot-working an ingot to obtain a hot-worked product, and a cold forging of the hot-worked product obtained in the hot-working step to obtain a cold forged product. The ingot includes a forging step and a hardening heat treatment step of hardening and heat-treating the cold forging obtained in the cold forging step to obtain an Fe—Mn alloy, and the ingot has a component composition of 20.0% by mass or more. Mn of 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, C of 0.5% by mass or more and 1.5% by mass or less, and 5.0% by mass or more and 10.0% by mass. % Or less Cr, the balance is Fe and unavoidable impurities, and the metal structure contains γ phase and α phase. The Fe—Mn alloy has a component composition of 20.0% by mass or more and 30.0% by mass. % Mn, 5.0% by mass or more and 10.0% by mass or less of Al, 0.5% by mass or more and 1.5% by mass or less of C, and 5.0% by mass or more and 10.0% by mass or less of Cr. A method for producing a Fe—Mn alloy, which comprises, with Fe and unavoidable impurities in the balance, and β—Mn phase and α phase as a metal structure.
According to the above method for producing a Fe—Mn alloy, an Fe—Mn alloy having a high hardness can be produced.
[5] In the hot work piece, when the total area fraction of the γ phase and the α phase is 100%, the area fraction of the γ phase is 60% or more and 90% or less, and the area fraction of the α phase. The ratio is 10% or more and 40% or less, and the Fe—Mn alloy has an area fraction of β—Mn phase of 60% when the total area fraction of β—Mn phase and α phase is 100%. The method for producing an Fe—Mn alloy according to the above [4], wherein the content is 90% or more and the area fraction of the α phase is 10% or more and 40% or less.
When the surface integral is in the above range, the balance between hardness and processability can be improved in the obtained Fe—Mn alloy.
[6] The method for producing an Fe—Mn alloy according to the above [4] or [5], wherein the cold forging step is a cold forging of the hot work piece at a processing rate of 20% or more and 80% or less.
When the processing rate is within the above range, the hardness of the finally produced Fe—Mn alloy can be increased.
[7] The method for producing a Fe—Mn alloy according to any one of [4] to [6], wherein the curing heat treatment step is a curing heat treatment of the cold forged product at 550 ° C. or higher and 800 ° C. or lower.
When the temperature of the curing heat treatment is in the above range, the hardness of the finally produced Fe—Mn alloy can be increased.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to these Examples.

[Example]
[Experimental Example 1-1]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 5% Ni in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 80% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 80% was subjected to a curing heat treatment at 600 ° C. for 12 hours in an air furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Examples 1-2 to 1-5]
A bar was obtained in the same manner as in Experimental Example 1-1 except that cold forging of Experimental Example 1-1 was not performed (Experiment Example 1-2). That is, in Experimental Example 1-2, a bar was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 1-1 was carried out except that the processing rates in cold forging of Experimental Example 1-1 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 1-3 to 1). -5).

[Experimental Examples 1-6 to 1-10]
A bar material was obtained in the same manner as in Experimental Example 1-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 1-1 was changed to 6 hours (Experimental Example 1-6).
A bar was obtained in the same manner as in Experimental Example 1-6 except that cold forging of Experimental Example 1-6 was not performed (Experimental Example 1-7). That is, in Experimental Example 1-7, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 1-6 was carried out except that the processing rates in cold forging of Experimental Example 1-6 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 1-8 to 1). -10).

[Experimental Examples 1-11 to 1-15]
A bar material was obtained in the same manner as in Experimental Example 1-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 1-1 was changed to 1 hour (Experiment Example 1-11).
A bar was obtained in the same manner as in Experimental Example 1-11, except that cold forging of Experimental Example 1-11 was not performed (Experimental Example 1-12). That is, in Experimental Example 1-12, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 1-11 was carried out except that the processing rates in cold forging of Experimental Example 1-11 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 1-13 to 1). -15).

[Experimental Examples 1-16 to 1-20]
A bar material was obtained in the same manner as in Experimental Example 1-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 1-1 was changed to 30 minutes (Experiment Example 1-16).
A bar was obtained in the same manner as in Experimental Example 1-16 except that cold forging of Experimental Example 1-16 was not performed (Experimental Example 1-17). That is, in Experimental Example 1-17, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 1-16 was carried out except that the processing rates in cold forging of Experimental Example 1-16 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 1-18 to 1). -20).

[Experimental Examples 1-21 to 1-25]
A bar was obtained in the same manner as in Experimental Example 1-1 except that the curing heat treatment of Experimental Example 1-1 was not performed (Experimental Example 1-21). That is, in Experimental Example 1-21, a bar was obtained by hot working and cold forging.
A bar was obtained in the same manner as in Experimental Example 1-21, except that cold forging of Experimental Example 1-21 was not performed (Experiment Example 1-22). That is, in Experimental Example 1-22, hot working was performed to obtain a bar. The same procedure as in Experimental Example 1-21 was carried out except that the processing rates in cold forging of Experimental Example 1-21 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 1-23 to 1). -25).

[Experimental Examples 2-1 to 2-3]
The same procedure as in Experimental Example 1-11 was carried out except that the curing heat treatment temperatures in the curing heat treatment of Experimental Example 1-11 were changed to 550 ° C, 700 ° C and 800 ° C to obtain rods (Experiment Examples 2-1 to 2). -3).
In Experimental Example 1-11, the processing rate in cold forging is 80%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 2-4 to 2-6]
A bar material was obtained in the same manner as in Experimental Example 1-12 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 1-12 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 2-4 to 2). -6).
In Experimental Example 1-12, cold forging was not performed, the curing heat treatment temperature in the curing heat treatment was 600 ° C., and the curing heat treatment time was 1 hour.

[Experimental Examples 2-7 to 2-9]
A bar material was obtained in the same manner as in Experimental Example 1-13 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 1-13 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 2-7 to 2). -9).
In Experimental Example 1-13, the processing rate in cold forging is 20%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 2-10 to 2-12]
A bar material was obtained in the same manner as in Experimental Example 1-14 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 1-14 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 2-10 to 2). -12).
In Experimental Example 1-14, the processing rate in cold forging is 40%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 2-13 to 2-15]
A bar material was obtained in the same manner as in Experimental Example 1-15 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 1-15 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 2-13 to 2). -15).
In Experimental Example 1-15, the processing rate in cold forging is 60%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Example 3-1]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 10% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 80% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 80% was subjected to a curing heat treatment at 600 ° C. for 12 hours in an air furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Examples 3-2 to 3-5]
A bar was obtained in the same manner as in Experimental Example 3-1 except that cold forging of Experimental Example 3-1 was not performed (Experimental Example 3-2). That is, in Experimental Example 3-2, a bar material was obtained by performing a curing heat treatment following hot working. A bar material was obtained in the same manner as in Experimental Example 3-1 except that the processing rates in cold forging of Experimental Example 3-1 were changed to 20%, 40% and 60% (Experimental Examples 3-3-3). -5).

[Experimental Examples 3-6 to 3-10]
A bar material was obtained in the same manner as in Experimental Example 3-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 3-1 was changed to 6 hours (Experimental Example 3-6).
A bar was obtained in the same manner as in Experimental Example 3-6 except that cold forging of Experimental Example 3-6 was not performed (Experimental Example 3-7). That is, in Experimental Example 3-7, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 3-6 was carried out except that the processing rates in cold forging of Experimental Example 3-6 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 3-8 to 3). -10).

[Experimental Examples 3-11 to 3-15]
A bar material was obtained in the same manner as in Experimental Example 3-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 3-1 was changed to 1 hour (Experimental Example 3-11).
A bar was obtained in the same manner as in Experimental Example 3-11, except that cold forging of Experimental Example 3-11 was not performed (Experimental Example 3-12). That is, in Experimental Example 3-12, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 3-11 was carried out except that the processing rates in cold forging of Experimental Example 3-11 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 3-13 to 1). -15).

[Experimental Examples 3-16 to 3-20]
A bar material was obtained in the same manner as in Experimental Example 3-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 3-1 was changed to 30 minutes (Experimental Example 3-16).
A bar was obtained in the same manner as in Experimental Example 3-16, except that cold forging of Experimental Example 3-16 was not performed (Experimental Example 3-17). That is, in Experimental Example 3-17, a bar was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 3-16 was carried out except that the processing rates in cold forging of Experimental Example 3-16 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 3-18 to 3). -20).

[Experimental Examples 3-21 to 3-25]
A bar was obtained in the same manner as in Experimental Example 3-1 except that the curing heat treatment of Experimental Example 3-1 was not performed (Experimental Example 3-21). That is, in Experimental Example 3-21, a bar was obtained by hot working and cold forging.
A bar was obtained in the same manner as in Experimental Example 3-21, except that cold forging of Experimental Example 3-21 was not performed (Experimental Example 3-22). That is, in Experimental Example 3-22, hot working was performed to obtain a bar. The same procedure as in Experimental Example 3-21 was carried out except that the processing rates in cold forging of Experimental Example 3-21 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 3-23 to 3). -25).

[Experimental Examples 4-1 to 4-3]
The same procedure as in Experimental Example 3-11 was carried out except that the curing heat treatment temperatures in the curing heat treatment of Experimental Example 3-11 were changed to 550 ° C, 700 ° C and 800 ° C to obtain rods (Experiment Examples 4-1 to 4). -3).
In Experimental Example 3-11, the processing rate in cold forging is 80%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 4-4 to 4-6]
The same procedure as in Experimental Example 3-12 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 3-12 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 4-4 to 4). -6).
In Experimental Example 3-12, cold forging was not performed, the curing heat treatment temperature in the curing heat treatment was 600 ° C., and the curing heat treatment time was 1 hour.

[Experimental Examples 4-7-4-9]
The same procedure as in Experimental Example 3-13 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 3-13 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 4-7 to 4). -9).
In Experimental Example 3-13, the processing rate in cold forging is 20%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 4-10-4-12]
A bar material was obtained in the same manner as in Experimental Example 3-14 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 3-14 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 4-10 to 4). -12).
In Experimental Example 3-14, the processing rate in cold forging is 40%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 4-13 to 4-15]
A bar material was obtained in the same manner as in Experimental Example 3-15 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 3-15 was changed to 550 ° C, 700 ° C and 800 ° C (Experiment Examples 4-13 to 4). -15).
In Experimental Example 3-15, the processing rate in cold forging is 60%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Example 5-1]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 0.5% C, 10% Cr in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 80% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 80% was subjected to a curing heat treatment at 600 ° C. for 12 hours in an air furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Examples 5-2-5-5]
A bar was obtained in the same manner as in Experimental Example 5-1 except that cold forging of Experimental Example 5-1 was not performed (Experimental Example 5-2). That is, in Experimental Example 5-2, a bar material was obtained by performing a curing heat treatment following hot working. A bar material was obtained in the same manner as in Experimental Example 5-1 except that the processing rates in cold forging of Experimental Example 5-1 were changed to 20%, 40% and 60% (Experimental Examples 5-3 to 5). -5).

[Experimental Examples 5-6 to 5-10]
A bar material was obtained in the same manner as in Experimental Example 5-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 5-1 was changed to 6 hours (Experimental Example 5-6).
A bar was obtained in the same manner as in Experimental Example 5-6 except that cold forging of Experimental Example 5-6 was not performed (Experimental Example 5-7). That is, in Experimental Example 5-7, a bar was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 5-6 was carried out except that the processing rates in cold forging of Experimental Example 5-6 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 5-8 to 5). -10).

[Experimental Examples 5-11 to 5-15]
A bar material was obtained in the same manner as in Experimental Example 5-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 5-1 was changed to 1 hour (Experimental Example 5-11).
A bar was obtained in the same manner as in Experimental Example 5-11, except that cold forging of Experimental Example 5-11 was not performed (Experimental Example 5-12). That is, in Experimental Example 5-12, a bar material was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 5-11 was carried out except that the processing rates in cold forging of Experimental Example 5-11 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 5-13 to 1). -15).

[Experimental Examples 5-16 to 5-20]
A bar material was obtained in the same manner as in Experimental Example 5-1 except that the curing heat treatment time in the curing heat treatment of Experimental Example 5-1 was changed to 30 minutes (Experimental Example 5-16).
A bar was obtained in the same manner as in Experimental Example 5-16, except that cold forging of Experimental Example 5-16 was not performed (Experimental Example 5-17). That is, in Experimental Example 5-17, a bar was obtained by performing a curing heat treatment following hot working. The same procedure as in Experimental Example 5-16 was carried out except that the processing rates in cold forging of Experimental Example 5-16 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 5-18 to 5). -20).

[Experimental Examples 5-21 to 5-25]
A bar was obtained in the same manner as in Experimental Example 5-1 except that the curing heat treatment of Experimental Example 5-1 was not performed (Experimental Example 5-21). That is, in Experimental Example 5-21, a bar was obtained by hot working and cold forging.
A bar was obtained in the same manner as in Experimental Example 5-21, except that cold forging of Experimental Example 5-21 was not performed (Experimental Example 5-22). That is, in Experimental Example 5-22, hot working was performed to obtain a bar. The same procedure as in Experimental Example 5-21 was carried out except that the processing rates in cold forging of Experimental Example 5-21 were changed to 20%, 40% and 60% to obtain rods (Experimental Examples 5-23 to 5). -25).

[Experimental Examples 6-1 to 6-3]
The same procedure as in Experimental Example 5-11 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 5-11 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 6-1 to 6). -3).
In Experimental Example 5-11, the processing rate in cold forging is 80%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 6-4 to 6-6]
The same procedure as in Experimental Example 5-12 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 5-12 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 6-4 to 6). -6).
In Experimental Example 5-12, cold forging was not performed, the curing heat treatment temperature in the curing heat treatment was 600 ° C., and the curing heat treatment time was 1 hour.

[Experimental Examples 6-7 to 6-9]
The same procedure as in Experimental Example 5-13 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 5-13 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 6-7 to 6). -9).
In Experimental Example 5-13, the processing rate in cold forging is 20%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 6-10 to 6-12]
The same procedure as in Experimental Example 5-14 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 5-14 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experimental Examples 6-10 to 6). -12).
In Experimental Example 5-14, the processing rate in cold forging is 40%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

[Experimental Examples 6-13 to 6-15]
The same procedure as in Experimental Example 5-15 was carried out except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 5-15 was changed to 550 ° C, 700 ° C and 800 ° C to obtain a bar (Experiment 6-13 to 6). -15).
In Experimental Example 5-15, the processing rate in cold forging is 60%, the curing heat treatment temperature in the curing heat treatment is 600 ° C., and the curing heat treatment time is 1 hour.

The experimental examples corresponding to the examples are Experimental Examples 1-1, 1-3 to 1-5, 1-6, 1-8 to 1-10, 1-11, 1-13 to 1-15, 1 -16, 1-18 to 1-20, Experimental Examples 2-1 to 2-3, 2-7 to 2-15, Experimental Examples 3-1, 3-3 to 3-5, 3-6, 3-8 ~ 3-10, 3-11, 3-13 ~ 3-15, 3-16, 3-18 ~ 3-20, Experimental Examples 4-1 ~ 4-3, 4-7 ~ 4-15, Experimental Example 5 -1, 5-3 to 5-5, 5-6, 5-8 to 5-10, 5-11, 5-13 to 5-15, 5-16, 5-18 to 5-20, Experimental Example 6 -1 to 6-3, 6-7 to 6-15.

[Experimental Example 7-1]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 70% was subjected to a curing heat treatment at 600 ° C. for 1 hour in an atmospheric furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Examples 7-2, 7-3]
A bar material was obtained in the same manner as in Experimental Example 7-1 except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 7-1 was changed to 500 ° C. and 800 ° C. (Experimental Examples 7-2 and 7-3). ..

[Experimental Examples 8-1, 8-2]
A Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 2-2, except that cold forging and curing heat treatment of Experimental Example 2-2 were not performed. That is, an annealing heat treatment of Experimental Example 2-2 and water cooling were performed to obtain a bar (Experimental Example 8-1).
Further, a rod material of Fe—Mn alloy was obtained in the same manner as in Experimental Example 2-2 except that the curing heat treatment of Experimental Example 2-2 was not performed. That is, a bar was obtained by performing cold forging of Experimental Example 2-2 (Experimental Example 8-2).
In Experimental Example 2-2, the processing rate in cold forging is 80%, the curing heat treatment temperature in the curing heat treatment is 700 ° C., and the curing heat treatment time is 1 hour.

[evaluation]
<Vickers hardness>
The bar finally obtained in Experimental Example 1-1 was cut to obtain a test piece having a thickness of 2 mm, and the Vickers hardness was measured with a Vickers hardness tester. Specifically, the average value of 6 measurement points was obtained. The bar material of Experimental Example 1-1 showed HV958.
Experimental Examples 1-2 to 1-25, Experimental Examples 2-1 to 2-15, Experimental Examples 3-1 to 3-25, Experimental Examples 4-1 to 4-15, Experimental Examples 5-1 to 5-25, The rods finally obtained in Experimental Examples 6-1 to 6-15 were also measured in the same manner.

1 to 6 show the measurement results of Vickers hardness.
Specifically, FIG. 1 is a diagram showing a change in Vickers hardness with respect to a processing rate for an Fe—Mn alloy sample. Experimental Examples 1-1 to 1-25 are shown in graphs by curing heat treatment time. FIG. 2 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. Experimental Examples 1-11 to 1-15 and Experimental Examples 2-1 to 2-15 are shown in graphs by processing rate.
FIG. 3 is a diagram showing the change in Vickers hardness with respect to the processing rate for the Fe—Mn alloy sample. Experimental Examples 3-1 to 3-25 are shown in graphs by curing heat treatment time. FIG. 4 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. Experimental Examples 3-11 to 3-15 and Experimental Examples 4-1 to 4-15 are shown in graphs by processing rate.
FIG. 5 is a diagram showing the change in Vickers hardness with respect to the processing rate for the Fe—Mn alloy sample. Experimental Examples 5-1 to 5-25 are shown in graphs by curing heat treatment time. FIG. 6 is a diagram showing changes in Vickers hardness with respect to the curing heat treatment temperature for the Fe—Mn alloy sample. Experimental Examples 5-11 to 5-15 and Experimental Examples 6-1 to 6-15 are shown in graphs by processing rate. The machining rates in FIGS. 1 to 6 are the machining rates in cold forging.

<SEM image observation>
The rod material finally obtained in Experimental Example 7-1 was observed using a reflecting electron microscope (SEM).
The rods finally obtained in Experimental Examples 7-2 and 7-3 were also observed in the same manner.

7, 8 and 9 are views showing SEM images of Fe—Mn alloy samples. That is, they are SEM images of the rods of Experimental Examples 7-1 to 7-3, respectively. The gray part is the β-Mn phase, and the black part is the α phase. The identification of these two phases was performed from the results of electron diffraction graphic analysis described later. That is, the pattern of the electron diffraction pattern in the gray color portion coincided with Mn _0.375 Fe _0.375 Al _0.25 , which is a β-Mn structure. Further, the pattern of the electron diffraction pattern in the black portion coincided with the pattern of α-Fe, which is an α phase structure.

The area fraction was evaluated based on the SEM image and / or the EBSD image taken by the EBSD (electron backscatter diffraction method) attached to the SEM. In the SEM image, the area fraction of each is obtained from the contrast difference between the β-Mn phase and the α phase, and in the EBSD image, the β-Mn phase and the α phase are color-coded as a color map, and the respective areas are obtained. I asked for a fraction.
When the total area fraction of the β-Mn phase and the α phase is 100%, in Experimental Example 7-1, the area fraction of the β-Mn phase is 85% and the area fraction of the α phase is 15%. there were. In Experimental Example 7-2, the surface integral of the β-Mn phase was 60%, and the surface integral of the α phase was 40%. In Experimental Example 7-3, the surface integral of the β-Mn phase was 75%, and the surface integral of the α phase was 25%.
In addition, in other experimental examples corresponding to the examples, it is considered that the finally obtained bar contains β-Mn phase and α phase as the metal structure. Further, when the total area fraction of the β-Mn phase and the α phase is 100%, the area fraction of the β-Mn phase is 60% or more and 90% or less, and the area fraction of the α phase is 10%. It is considered to be 40% or less.
Further, in Experimental Example 7-1, in the Fe—Mn alloy sample after hot working, the area fraction of the γ phase was 80% and the area fraction of the α phase was 20%.

<X-ray diffraction measurement>
The bar material finally obtained in Experimental Example 1-1 was subjected to X-ray diffraction measurement.

FIG. 10 is a diagram showing an X-ray diffraction pattern of a Fe—Mn alloy sample. That is, it is an X-ray diffraction pattern for the bar material of Experimental Example 1-1. Diffraction peaks of α-Fe phase and β-Mn phase and diffraction peaks of Cr carbide were observed.

<observation of TEM image>
The rod material finally obtained in Experimental Example 2-2 was observed using a transmission electron microscope (TEM). Here, an HAADF image (HAADF-STEM image), which is a kind of STEM image, was obtained. The HAADF (High Angle Anal Dark-Field) image is obtained by detecting high-angle scattered transmission electrons in a STEM (Scanning Transmission Electron Microscopic) image with an annular detector.
The rods finally obtained in Experimental Examples 8-1 and 8-2 were also observed in the same manner.

The results of TEM image observation are shown in FIGS. 11A to 16B.
Specifically, FIG. 11A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 11B is an enlarged view of a part of the HAADF-STEM image of FIG. 11A. FIG. 12A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 12B is an enlarged view of a part of the mapping of FIG. 12A. It should be noted that FIGS. 11B and 12B are enlarged views of the inside of the quadrangular frame of FIGS. 11A and 12A, respectively. These are the results for the bar material finally obtained in Experimental Example 2-2.
FIG. 13A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 13B is an enlarged view of a part of the HAADF-STEM image of FIG. 13A. FIG. 14A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 14B is an enlarged view of a part of the mapping of FIG. 14A. It should be noted that FIGS. 13B and 14B are enlarged views of the inside of the quadrangular frame of FIGS. 13A and 14A, respectively. These are the results for the bar material finally obtained in Experimental Example 8-1.
FIG. 15A is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. FIG. 15B is an enlarged view of a part of the HAADF-STEM image of FIG. 15A. FIG. 16A is a diagram showing the results of mapping by STEM-EDS for the Fe—Mn alloy sample. FIG. 16B is an enlarged view of a part of the mapping of FIG. 16A. It should be noted that FIGS. 15B and 16B are enlarged views of the inside of the quadrangular frame of FIGS. 15A and 15A, respectively. These are the results for the bar material finally obtained in Experimental Example 8-2.

From FIGS. 11A to 16B, the Fe—Mn alloy of Experimental Example 2-2 obtained through cold forging and curing heat treatment has a β—Mn phase and an α phase. The hot work piece of Experimental Example 8-1 obtained by performing hot work has a γ phase and an α phase. No dislocations are observed in the γ-phase and α-phase metal crystals. The cold forged product of Experimental Example 8-2 obtained by performing cold forging has a γ phase and an α phase. White streak-like dislocations are observed in the γ-phase and α-phase metal crystals. From these results, it is considered that when dislocations are introduced into the metal crystal by cold forging, the transformation from the γ phase to the β-Mn phase occurs during the curing heat treatment.

Further, FIG. 17A is a diagram showing a HAADF-STEM image of the Fe—Mn alloy sample. FIG. 17B is a diagram showing an electron diffraction pattern of the Fe—Mn alloy sample. FIG. 17C is a diagram showing a HAADF-STEM image of a Fe—Mn alloy sample. 17B and 17C are HAADF-STEM images, which are electron diffraction figures of the portion surrounded by the dotted line in FIG. 17A, respectively. These are the results for the bar material finally obtained in Experimental Example 2-2.

From FIGS. 17A to 17C, the portion surrounded by the dotted line in FIG. 17A can be identified as the β-Mn phase. The other γ phase and α phase can also be identified from the electron diffraction pattern.

Further, FIG. 18 is a diagram showing an electron diffraction pattern of the Fe—Mn alloy sample. This is the result of the bar material finally obtained in Experimental Example 7-1. Specifically, it is an electron diffraction figure of the gray color portion of FIG. 7. As a result of the phase analysis by the electron diffraction pattern, as shown in FIG. 18 (electron diffraction pattern Mn _0.375 Fe _0.375 Al _0.25 [011] plane), the Fe—Mn alloy may contain the β—Mn phase after the curing heat treatment at 600 ° C. confirmed.

[Experimental Example 9-1]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 0.5% C, 10% Cr in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 80% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 80% was subjected to a curing heat treatment at 550 ° C. for 12 hours in an air furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Example 9-2]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-1 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 5% Ni in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-3]
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 2.5% Ni in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.
This ingot was subjected to a homogenization heat treatment at 1150 ° C. for 3 hours, followed by hot hammer forging and then hot groove roll rolling. By this hot working, a bar having a machining rate (decrease in cross-sectional area) of 70% with respect to the original ingot was obtained. Next, the bar was annealed at 1150 ° C. for 30 minutes and cooled with water.
Cold aging forging was performed on the bar after water cooling. By this cold forging, a bar having a machining rate (decrease in cross-sectional area) of 80% with respect to the bar before machining was obtained.
Subsequently, a bar having a processing rate of 80% was subjected to a curing heat treatment at 600 ° C. for 12 hours in an air furnace and air-cooled. By this curing heat treatment, a bar of Fe—Mn alloy was obtained.

[Experimental Example 9-4]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 7.5% Ni in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-5]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 25% Mn, 8% Al, 1% C, 10% Cr in mass% and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-6]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 20% Mn, 8% Al, 1% C, 10% Cr, 5% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-7]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1.5% C, 10% Cr, 5% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-8]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 8% Al, 1.5% C, 5% Cr, 5% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-9]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 10% Al, 1% C, 10% Cr, 5% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[Experimental Example 9-10]
A rod of Fe—Mn alloy was obtained in the same manner as in Experimental Example 9-3 except that the cast ingot obtained as described below was used.
The material was weighed in a composition ratio of 30% Mn, 5% Al, 1% C, 10% Cr, 5% Ni in mass%, and Fe in the balance. Next, these materials were melted in a crucible using a high-frequency vacuum melting device, and then poured into a copper mold to obtain a cast ingot having a diameter of 28 mm and a length of 110 mm.

[evaluation]
<Vickers hardness>
Using the bar finally obtained in Experimental Example 9-1, the Vickers hardness was measured by the above-mentioned method. The rods finally obtained in Experimental Examples 9-2 to 9-10 and Experimental Example 7-1 were also measured in the same manner.

Table 1 shows the measurement results of Vickers hardness for Experimental Examples 9-1 to 9-10. Table 1 also shows the component composition and production conditions of the finally obtained bar. The measurement results of Vickers hardness of Experimental Example 3-1 and Experimental Example 7-1 are also shown.

<Surface integral>
The surface integral of the bar finally obtained in Experimental Example 9-2 was determined by the above method. In Experimental Example 9-2, the surface integral of the β-Mn phase was 85%, and the surface integral of the α phase was 15%.

Claims (4)

As the component composition, Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, C of 0.5% by mass or more and 1.5% by mass or less, and It contains Cr of 5.0% by mass or more and 10.0% by mass or less, and the balance consists of Fe and unavoidable impurities , or
As the component composition, Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, C and 5 of 0.5% by mass or more and 1.5% by mass or less. It contains Cr of 0.0% by mass or more and 10.0% by mass or less, and Ni of 2.5% by mass or more and 10.0% by mass or less, and the balance consists of Fe and unavoidable impurities.
The metallographic structure includes β-Mn phase and α phase.
When the total area fraction of the β-Mn phase and the α phase is 100%, the area fraction of the β-Mn phase is 60% or more and 90% or less, and the area fraction of the α phase is 10% or more and 40. % Or less, Fe—Mn alloy. The hot working process to obtain a hot work by hot working the ingot,
A cold forging step of cold forging the hot work piece obtained in the hot work step to obtain a cold forged product, and a cold forging step.
Including a curing heat treatment step of curing and heat-treating the cold forged product obtained in the cold forging step to obtain a Fe—Mn alloy.
The ingot has 20.0% by mass or more and 30.0% by mass or less of Mn, 5.0% by mass or more and 10.0% by mass or less of Al, and 0.5% by mass or more and 1.5% by mass or less as a component composition. C and Cr of 5.0% by mass or more and 10.0% by mass or less, and the balance consists of Fe and unavoidable impurities , or 20.0% by mass or more and 30.0% by mass or less as a component composition. Mn, Al of 5.0% by mass or more and 10.0% by mass or less, C of 0.5% by mass or more and 1.5% by mass or less, Cr of 5.0% by mass or more and 10.0% by mass or less, and 2 .Contains 5% by mass or more and 10.0% by mass or less of Ni, the balance consists of Fe and unavoidable impurities, and contains γ phase and α phase as a metal structure.
The Fe-Mn alloy has a component composition of Mn of 20.0% by mass or more and 30.0% by mass or less, Al of 5.0% by mass or more and 10.0% by mass or less, and 0.5% by mass or more and 1.5. It contains C of mass% or less and Cr of 5.0 mass% or more and 10.0 mass% or less, and the balance consists of Fe and unavoidable impurities , or 20.0 mass% or more and 30.0 as a component composition. Mn of mass% or less, Al of 5.0% by mass or more and 10.0% by mass or less, C of 0.5% by mass or more and 1.5% by mass or less, Cr of 5.0% by mass or more and 10.0% by mass or less , And 2.5% by mass or more and 10.0% by mass or less of Ni, the balance is composed of Fe and unavoidable impurities, and the metal structure contains β-Mn phase and α phase.
In the hot work piece, when the total area fraction of the γ phase and the α phase is 100%, the area fraction of the γ phase is 60% or more and 90% or less, and the area fraction of the α phase is 10. % Or more and 40% or less,
The Fe—Mn alloy has an area fraction of β—Mn phase of 60% or more and 90% when the total area fraction of β—Mn phase and α phase is 100%, and the area fraction of α phase. A method for producing a Fe—Mn alloy, wherein the ratio is 10% or more and 40% or less . The method for producing an Fe—Mn alloy according to claim 2 , wherein the cold forging step is for cold forging the hot work piece at a processing rate of 20% or more and 80% or less. The method for producing a Fe—Mn alloy according to claim 2 or 3 , wherein the curing heat treatment step is a curing heat treatment of the cold forged product at 550 ° C. or higher and 800 ° C. or lower.

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