JP2019178352A - Fe-Mn ALLOY AND MANUFACTURING METHOD OF Fe-Mn ALLOY - Google Patents

Abstract

An object is to provide an Fe—Mn alloy having high hardness. The Fe-Mn alloy has a composition of Mn of 20.0% by mass to 30.0% by mass, Al of 5.0% by mass to 10.0% by mass, and 0.5% by mass or more. It contains 1.5 mass% or less of C and 5.0 mass% or more and 10.0 mass% or less of Cr, and the balance is Fe and inevitable impurities, and includes a β-Mn phase and an α phase as a metal structure. . 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. % Is preferable. [Selection diagram] None

Description

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

Patent Document 1 describes a low specific gravity iron alloy. This low specific gravity iron alloy has Mn: 15.0 to 45.0 mass%, Al: 8.0 to 20.0 mass%, C: 0.01 to 2.5 mass%, Si: 0.01 to 5 0.0 mass%, Cr: 0.01-10.0 mass%, B: 0.001-1.5 mass%, N: 0.01-1.5 mass%, the balance Fe and unavoidable impurities. Moreover, the said low specific gravity iron alloy consists of an iron alloy provided with two phases of (gamma) + (alpha) whose alpha phase fraction is 10-95%. Non-Patent Document 1 describes an FeMnAl alloy. This FeMnAl alloy has a composition of Fe-29.5Mn-9.2Al-0.94C. When the FeMnAl alloy is subjected to an aging treatment at 550 ° C. for 10 ⁴ minutes or longer, β-Mn precipitates.

JP 2005-325387 A

Ryan A. Howel, "Microstructural influence on dynamic properties of age hardenable FeMnAl Alliances, Documentary Society, Missouri University Sciences. 27-28

  However, the low specific gravity 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 an Fe—Mn alloy having high hardness.

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

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

FIG. 1 is a diagram showing a change in Vickers hardness with respect to a processing rate for an Fe—Mn alloy sample. FIG. 2 is a diagram showing the change in Vickers hardness with respect to the heat treatment temperature for the Fe—Mn alloy sample. FIG. 3 is a diagram showing a change in Vickers hardness with respect to the processing rate for an Fe—Mn alloy sample. FIG. 4 is a diagram showing the change in Vickers hardness with respect to the 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 an Fe—Mn alloy sample. FIG. 6 is a diagram showing the change in Vickers hardness with respect to the heat treatment temperature for the Fe—Mn alloy sample. FIG. 7 is a view showing an SEM image of the Fe—Mn alloy sample. FIG. 8 is a view showing an SEM image of the Fe—Mn alloy sample. FIG. 9 is a view showing an SEM image of the Fe—Mn alloy sample. FIG. 10 is a diagram showing an X-ray diffraction pattern of an Fe—Mn alloy sample. FIG. 11A is a diagram showing a HAADF-STEM image of an 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 result of mapping by STEM-EDS for an 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 an 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 a result of mapping by STEM-EDS for an 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 an 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 a result of mapping by STEM-EDS for an 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 an 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 an Fe—Mn alloy sample. FIG. 18 is a diagram showing an electron diffraction pattern of an Fe—Mn alloy sample.

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

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

  Thus, 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 excellent scratch resistance and dent resistance. Moreover, since the Fe-Mn alloy which concerns on embodiment contains the alpha phase, it is excellent also in workability.

On the other hand, the low specific gravity iron alloy described in Patent Document 1 includes a γ phase (austenite phase, fcc structure) and an α phase. For this reason, it is thought that hardness is low. Moreover, 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, an aging treatment at 550 ° C. is performed on this FeMnAl alloy. Here, β-Mn is precipitated by aging treatment for 10 ⁴ minutes or more. However, since β-Mn only appears as precipitates, the FeMnAl alloy is considered to have low hardness.

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

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

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

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

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

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

Moreover, the Fe—Mn alloy according to the embodiment includes 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 high hardness. Moreover, since the α phase is included, the Fe—Mn alloy is excellent in workability. 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 as a continuous phase as described above, not as a fine precipitate.

  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. Moreover, it is more preferable that the area fraction of the β-Mn phase is 70% or more and 90% or less, and the area fraction of the α phase is 10% or more and 30% or less. When the area fraction is in the above range, the balance between hardness and workability can be improved. The area fraction is determined from the measured values obtained by measuring the areas of the β-Mn phase and the α phase in a region having a specific size (for example, a region of 100 μm × 100 μm) in SEM image observation.

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

  In the Fe—Mn alloy according to the embodiment, the size of crystal grains is usually 10 μm or less. From the viewpoint of hardness, the crystal grains are preferably in the above range.

  About the Fe-Mn alloy which concerns on embodiment, Vickers hardness (HV) is 400 or more normally, Preferably it is 500 or more. When the Vickers hardness is in the above range, it is suitably used for applications requiring scratch resistance and dent resistance.

<Method for producing Fe-Mn alloy>
The manufacturing method of the Fe—Mn alloy according to the embodiment includes a hot working process, a cold forging process, and a hardening heat treatment process. In the method for producing the Fe—Mn alloy, in the hot working step, a hot work product is produced. In the cold forging process, a hot forged product is cold forged to produce a cold forged product having a metal crystal into which dislocations are introduced. This cold forging includes a γ phase and an α phase as a metal structure. In the hardening heat treatment step, the cold forging is subjected to hardening heat treatment to produce an Fe—Mn alloy. This Fe—Mn alloy includes a β-Mn phase and an α phase as a metal structure. It is considered that the γ phase transforms into a 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. In addition, when the hot-worked product is subjected to curing heat treatment as it is, transformation from the γ phase to the β-Mn phase does not occur.

  The hot working process is a process of obtaining a hot work product by hot working an ingot.

  The ingot has a component composition of 20.0 mass% to 30.0 mass% Mn, 5.0 mass% to 10.0 mass% Al, 0.5 mass% to 1.5 mass%. C and 5.0 mass% or more and 10.0 mass% or less of Cr are contained, and the balance is Fe and inevitable impurities. When the ingot has the above component composition, an Fe—Mn alloy having a β-Mn phase can be produced. That is, an Fe—Mn alloy having a 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 workability of the manufactured Fe—Mn alloy can be improved.

  The ingot includes a γ phase and an α phase as a metal structure. The ingot has an area fraction of the γ phase of 60% or more and 90% or less and an area fraction of the α phase of 10% or more and 40% when the total of the area fraction of the γ phase and the α phase is 100%. The following is preferable. More preferably, the area fraction of the γ phase is 70% or more and 90% or less, and the area fraction of the α phase is 10% or more and 30% or less. When the area fraction is in the above range, transformation to β-Mn phase is likely to occur during the curing heat treatment.

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

  Specific examples of hot working include forging and grooved roll rolling, whereby a bar is obtained as a hot work. Hot working is usually performed at 1100 ° C. or higher and 1250 ° C. or lower. In addition, it is usually water-cooled after hot working.

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

  In the hot-worked product, the component composition and the type and ratio of the metal structure are the same as in the ingot including the preferred range and the reason. Moreover, about the said hot-worked material, the magnitude | size of a crystal grain is 10 micrometers or less normally. From the viewpoint of the hardness of the finally produced Fe—Mn alloy, the crystal grains are preferably in the above range.

  The cold forging step is a step of cold forging the hot workpiece obtained in the hot working step to obtain a cold forged product. By cold forging, dislocations are introduced into the metal crystals of the cold forging.

  Specific examples of the cold forging include swaging, and as a result, a bar with a reduced outer diameter can be obtained as a cold forged product.

  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 in the above range, dislocations can be introduced in a suitable amount for the metal crystal. Therefore, the transformation to β-Mn phase occurs by the curing heat treatment, and the hardness of the finally produced Fe-Mn alloy can be increased.

  In the cold forged product, the component composition and the type and ratio of the metal structure are the same as those of the ingot and the hot-worked product, including the preferred range and the reason. Moreover, about the said cold forging, the magnitude | size of a crystal grain is 10 micrometers or less normally. From the viewpoint of the hardness of the finally produced Fe—Mn alloy, the crystal grains are preferably in the above range.

  A hardening heat treatment process is a process of obtaining the Fe-Mn alloy by carrying out hardening heat treatment of the said cold forging obtained in the said cold forging process. The transformation from the γ phase to the β-Mn phase occurs by the curing heat treatment. Thereby, specifically, a bar of Fe—Mn alloy is obtained.

  The curing heat treatment is preferably performed at 550 ° C. or higher and 800 ° C. or lower, 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 lowered. Furthermore, it may be costly. The curing heat treatment is preferably performed for 10 minutes to 12 hours. When the time for the curing heat treatment is in the above range, the hardness of the finally produced Fe—Mn alloy can be increased. If the time for the curing heat treatment is too long, the strength of the finally produced Fe—Mn alloy may be reduced. Furthermore, it may be costly. In addition, after the curing heat treatment, it is usually air-cooled.

  The obtained Fe-Mn alloy has a component composition of 20.0 mass% to 30.0 mass% Mn, 5.0 mass% to 10.0 mass% Al, 0.5 mass% to 1 0.5% by mass or less of C and 5.0% by mass or more and 10.0% by mass or less of Cr, with the balance being Fe and inevitable impurities. The Fe—Mn alloy may further contain 2.5 mass% or more and 10.0 mass% or less of Ni as a component composition. In addition, in the Fe-Mn alloy, the component composition of the ingot is generally kept substantially. The Fe—Mn alloy includes a β-Mn phase and an α phase as a metal structure. Thus, the produced Fe—Mn alloy has a specific component composition and has a β-Mn phase as a metal structure. Therefore, the Fe—Mn alloy has high hardness and excellent scratch resistance and dent resistance. In addition, the Fe—Mn alloy includes an α phase, and thus has excellent workability.

  The Fe—Mn alloy has an area fraction of β-Mn phase of 60% to 90% when the total area fraction of β-Mn phase and α phase is 100%. The area fraction is preferably 10% or more and 40% or less. Moreover, it is more preferable that the area fraction of the β-Mn phase is 70% or more and 90% or less, and the area fraction of the α phase is 10% or more and 30% or less. When the area fraction is in the above range, the balance between hardness and workability can be improved.

  Moreover, about the said Fe-Mn alloy, the magnitude | size of a crystal grain is 10 micrometers or less normally. From the viewpoint of the hardness of the Fe—Mn alloy, the crystal grains are preferably in the above range.

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

  In the method for producing the Fe—Mn alloy, a homogenization heat treatment step of homogenizing heat treatment of the ingot may be performed before hot working. The homogenization heat treatment is performed, for example, at 1000 ° C. or more and 1200 ° C. or less for 0.5 hours or more and 3 hours or less. Thereby, the structure of the ingot can be made uniform. In this case, in the hot working step, the ingot subjected to the homogenization heat treatment is hot worked to obtain a hot work product.

  In the manufacturing method of the said Fe-Mn alloy, you may perform the annealing process which anneals the said hot workpiece obtained at the said hot working process after hot working. For example, annealing is performed at 1000 ° C. or more and 1200 ° C. or less for 0.5 hours or more and 3 hours or less. Thereby, the structure | tissue of a hot workpiece can be made uniform. In this case, in the cold forging step, the annealed hot-worked product is cold forged to obtain a cold forged product.

  In the manufacturing method of the Fe—Mn alloy, the case of obtaining the rod of the Fe—Mn alloy has been described, but the present invention is not limited thereto. You may manufacture the wire and board | plate material of a Fe-Mn alloy. In this case, for example, processing is performed to obtain a wire or plate in hot processing and cold forging.

  In addition, you may manufacture the Fe-Mn alloy which has the specific component composition mentioned above and metal structure with manufacturing methods other than the manufacturing method of the Fe-Mn alloy mentioned above. That is, the production method is not limited as long as the Fe—Mn alloy having the above-described specific component composition and metal structure is obtained.

<Use of Fe-Mn alloy>
The Fe—Mn alloy is suitably used for a watch member (for example, an exterior). Furthermore, the Fe—Mn alloy is also suitably used for transportation equipment such as automobiles, ships, and airplanes, machines, electrical products, architecture, structures, optical instruments, instruments, and accessories (for example, exteriors). Utilizing the high hardness of the Fe—Mn alloy, it is suitably used for applications that require sliding resistance, scratch resistance, and dent resistance.

  As described above, the present invention relates to the following.

[1] As a component composition, Mn of 20.0 mass% or more and 30.0 mass% or less, Al of 5.0 mass% or more and 10.0 mass% or less, 0.5 mass% or more and 1.5 mass% or less of An 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 including a β-Mn phase and an α phase as a metal structure.
The Fe—Mn alloy has a high hardness.
[2] When the total area fraction of β-Mn phase and α phase is 100%, the area fraction of β-Mn phase is 60% or more and 90% or less, and the area fraction of α phase is 10%. The Fe—Mn alloy according to [1], which is not less than 40% and not more than 40%.
When the area fraction is in the above range, the Fe—Mn alloy can improve the balance between hardness and workability.
[3] The Fe—Mn alloy according to [1] or [2], further including 2.5% by mass to 10.0% by mass of Ni as the component composition.
When Ni is contained in the above amount, the balance between the hardness and strength of the Fe—Mn alloy can be improved.
[4] A hot working process in which an ingot is hot worked to obtain a hot work, and a cold forging is obtained by cold forging the hot work obtained in the hot working process. Including a forging step and a hardening heat treatment step for obtaining a Fe—Mn alloy by hardening and heat-treating the cold forging obtained in the cold forging step, wherein the ingot has a component composition of 20.0% by mass or more. 30.0 mass% or less Mn, 5.0 mass% or more and 10.0 mass% or less Al, 0.5 mass% or more and 1.5 mass% or less C, and 5.0 mass% or more and 10.0 mass% or less. % Of Cr, the balance being Fe and inevitable impurities, including a γ phase and an α phase as a metal structure, and the Fe—Mn alloy having a component composition of 20.0 mass% or more and 30.0 mass% % Mn, 5.0% to 10.0% Al, 0.5% Containing not less than 1.5% by mass and not more than 1.5% by mass of C, and not less than 5.0% by mass and not more than 10.0% by mass of Cr, with the balance being Fe and unavoidable impurities. The manufacturing method of the Fe-Mn alloy containing a phase.
According to the method for producing an Fe—Mn alloy, an Fe—Mn alloy having high hardness can be produced.
[5] The hot-worked product has an area fraction of the γ phase of 60% or more and 90% or less when the total of the area fraction of the γ phase and the α phase is 100%. The Fe—Mn alloy has an area fraction of β-Mn phase of 60% when the total of the area fractions of β-Mn phase and α phase is 100%. The method for producing an Fe—Mn alloy according to the above [4], which is 90% or more and the α phase area fraction is 10% or more and 40% or less.
When the area fraction is in the above range, the balance between hardness and workability can be improved in the obtained Fe—Mn alloy.
[6] The method for producing an Fe—Mn alloy according to [4] or [5], wherein the cold forging step cold forges the hot-worked product at a processing rate of 20% to 80%.
When the processing rate is in the above range, the hardness of the finally produced Fe—Mn alloy can be increased.
[7] The method for producing an Fe—Mn alloy according to any one of [4] to [6], wherein the hardening heat treatment step includes hardening and heat-treating the cold forged product at 550 ° C. or more and 800 ° C. or less.
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.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

[Example]
[Experimental Example 1-1]
The materials were weighed at a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar having a processing rate (reduction rate of cross-sectional area) of 80% with respect to the bar before processing was obtained.
Subsequently, the bar with a processing rate of 80% was subjected to curing heat treatment at 600 ° C. for 12 hours in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod of Fe—Mn alloy was obtained.

[Experimental Examples 1-2 to 1-5]
Except not having performed the cold forging of Experimental Example 1-1, a bar was obtained in the same manner as Experimental Example 1-1 (Experimental Example 1-2). That is, in Experimental Example 1-2, a bar was obtained by performing a heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 1-1 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 1-1, and obtained the bar (Experimental 1-3-1 -5).

[Experimental Examples 1-6 to 1-10]
Except having changed the hardening heat processing time in the hardening heat processing of Experimental Example 1-1 into 6 hours, it carried out similarly to Experimental Example 1-1 and obtained the rod (Experimental Example 1-6).
A bar was obtained in the same manner as in Experimental Example 1-6 except that the cold forging in 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 heat treatment after the hot working. Except having changed the processing rate in the cold forging of Experimental Example 1-6 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 1-6, and obtained the bar material (Experimental Examples 1-8 to 1). -10).

[Experimental Examples 1-11 to 1-15]
Except having changed into 1 hour the hardening heat processing time in the hardening heat processing of Experimental example 1-1, it carried out similarly to Experimental example 1-1 and obtained the rod (Experimental example 1-11).
A bar was obtained in the same manner as in Experimental Example 1-11 except that the cold forging in Experimental Example 1-11 was not performed (Experimental Example 1-12). That is, in Experimental Example 1-12, a bar was obtained by performing a heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 1-11 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 1-11, and obtained the bar (Experimental Examples 1-3-1 -15).

[Experimental Examples 1-16 to 1-20]
Except having changed the hardening heat processing time in the hardening heat processing of Experimental Example 1-1 into 30 minutes, it carried out similarly to Experimental Example 1-1 and obtained the rod (Experimental Example 1-16).
A bar was obtained in the same manner as in Experimental Example 1-16 except that the cold forging in Experimental Example 1-16 was not performed (Experimental Example 1-17). That is, in Experimental Example 1-17, the hot-working was followed by a curing heat treatment to obtain a bar. Except having changed the processing rate in the cold forging of Experimental Example 1-16 into 20%, 40%, and 60%, it carried out similarly to Experimental Example 1-16, and obtained the bar (Experimental Examples 1-18-1) -20).

[Experimental Examples 1-21 to 1-25]
Except not having performed the hardening heat treatment of Experimental Example 1-1, a bar was obtained in the same manner as Experimental Example 1-1 (Experimental 1-21). That is, in Experimental Example 1-21, hot working and cold forging were performed to obtain a bar.
A bar was obtained in the same manner as in Experimental Example 1-21 except that the cold forging in Experimental Example 1-21 was not performed (Experimental 1-22). That is, in Experimental Example 1-22, hot working was performed to obtain a bar. Except having changed the processing rate in the cold forging of Experimental Example 1-21 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 1-21, and obtained the bar (Experimental 1-23-1) -25).

[Experimental Examples 2-1 to 2-3]
Except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 1-11 was changed to 550 ° C., 700 ° C., and 800 ° C., the same procedure as in Experimental Example 1-11 was performed to obtain rods (Experimental 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]
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., the same procedure as in Experimental Example 1-12 was performed to obtain a bar (Experimental 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]
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., the same procedure as in Experimental Example 1-13 was performed to obtain rods (Experimental 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]
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., the same procedure as in Experimental Example 1-14 was performed to obtain rods (Experimental 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]
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., the same procedure as in Experimental Example 1-15 was performed to obtain rods (Experimental 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 materials were weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 10% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar having a processing rate (reduction rate of cross-sectional area) of 80% with respect to the bar before processing was obtained.
Subsequently, the bar with a processing rate of 80% was subjected to curing heat treatment at 600 ° C. for 12 hours in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod 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 the cold forging in 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 heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 3-1 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 3-1, and obtained the bar (Experimental Example 3-3-3) -5).

[Experimental Examples 3-6 to 3-10]
Except having changed the hardening heat processing time in the hardening heat processing of Experimental Example 3-1 to 6 hours, it carried out similarly to Experimental Example 3-1, and obtained the bar (Experimental Example 3-6).
A bar was obtained in the same manner as in Experimental Example 3-6 except that Cold Forging in 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 heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 3-6 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 3-6, and obtained the bar (Experimental Examples 3-8-3) -10).

[Experimental Examples 3-11 to 3-15]
Except having changed into 1 hour the hardening heat processing time in the hardening heat processing of Experimental example 3-1, it carried out similarly to Experimental example 3-1, and obtained the rod (Experimental example 3-11).
A bar was obtained in the same manner as in Experimental Example 3-11 except that the cold forging in Experimental Example 3-11 was not performed (Experimental Example 3-12). That is, in Experimental Example 3-12, a bar was obtained by performing a heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 3-11 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 3-11, and obtained the bar (Experimental Examples 3-13 to 1) -15).

[Experimental Examples 3-16 to 3-20]
Except that the curing heat treatment time in the curing heat treatment of Experimental Example 3-1 was changed to 30 minutes, the same procedure as in Experimental Example 3-1 was performed to obtain a bar (Experimental Example 3-16).
A bar was obtained in the same manner as in Experimental Example 3-16 except that the cold forging in 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 heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 3-16 into 20%, 40%, and 60%, it carried out similarly to Experimental Example 3-16, and obtained the bar (Experimental Examples 3-18-3) -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 in Experimental Example 3-1 was not performed (Experimental Example 3-21). That is, in Experimental Example 3-21, hot working and cold forging were performed to obtain a bar.
Except not having performed the cold forging of Experimental Example 3-21, a bar was obtained in the same manner as Experimental Example 3-21 (Experimental Example 3-22). That is, in Experimental Example 3-22, hot working was performed to obtain a bar. Except having changed the processing rate in cold forging of Experimental Example 3-21 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 3-21, and obtained the bar (Experimental Examples 3-23 to 3) -25).

[Experimental examples 4-1 to 4-3]
Except that the curing heat treatment temperature in the curing heat treatment of Experimental Example 3-11 was changed to 550 ° C., 700 ° C., and 800 ° C., the same procedure as in Experimental Example 3-11 was performed to obtain rods (Experimental Examples 4-1 to 4-4). -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]
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., the same procedure as in Experimental Example 3-12 was performed to obtain rods (Experimental Examples 4-4 to 4-4) -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 to 4-9]
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., the same procedure as in Experimental Example 3-13 was performed to obtain rods (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 to 4-12]
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., the same procedure as in Experimental Example 3-14 was performed to obtain rods (Experimental Examples 4-10 to 4-4) -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]
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., the same procedure as in Experimental Example 3-15 was performed to obtain rods (Experimental 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 materials were weighed in a composition ratio of 30% Mn, 8% Al, 0.5% C, 10% Cr, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar having a processing rate (reduction rate of cross-sectional area) of 80% with respect to the bar before processing was obtained.
Subsequently, the bar with a processing rate of 80% was subjected to curing heat treatment at 600 ° C. for 12 hours in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod of Fe—Mn alloy was obtained.

[Experimental Examples 5-2 to 5-5]
A bar was obtained in the same manner as in Experimental Example 5-1, except that the cold forging in 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 heat treatment after the hot working. Except having changed the processing rate in the cold forging of Experimental Example 5-1 into 20%, 40%, and 60%, it carried out similarly to Experimental Example 5-1, and obtained the bar (Experimental Examples 5-3-5) -5).

[Experimental Examples 5-6 to 5-10]
Except having changed the hardening heat processing time in the hardening heat processing of Experimental Example 5-1 to 6 hours, it carried out similarly to Experimental Example 5-1, and obtained the rod (Experimental Example 5-6).
A bar was obtained in the same manner as in Experimental Example 5-6 except that the cold forging in Experimental Example 5-6 was not performed (Experimental Example 5-7). That is, in Experimental Example 5-7, a bar material was obtained by performing a heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 5-6 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 5-6, and obtained the bar (Experimental Examples 5-8-5) -10).

[Experimental Examples 5-11 to 5-15]
A bar 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 the cold forging in 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 heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 5-11 to 20%, 40%, and 60%, it carried out similarly to Experimental Example 5-11, and obtained the bar (Experimental Examples 5-13 to 1). -15).

[Experimental Examples 5-16 to 5-20]
A bar 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 the cold forging in Experimental Example 5-16 was not performed (Experimental Example 5-17). That is, in Experimental Example 5-17, a bar material was obtained by performing a heat treatment for curing subsequent to hot working. Except having changed the processing rate in the cold forging of Experimental Example 5-16 into 20%, 40%, and 60%, it carried out similarly to Experimental Example 5-16, and obtained the bar (Experimental Examples 5-18-5) -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 in Experimental Example 5-1 was not performed (Experimental Example 5-21). That is, in Experimental Example 5-21, hot working and cold forging were performed to obtain a bar.
A bar was obtained in the same manner as in Experimental Example 5-21 except that Cold Forging in 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. Except having changed the processing rate in the cold forging of Experimental Example 5-21 into 20%, 40%, and 60%, it carried out similarly to Experimental Example 5-21, and obtained the bar (Experimental Examples 5-23-5) -25).

[Experimental Examples 6-1 to 6-3]
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., the same procedure as in Experimental Example 5-11 was performed to obtain rods (Experimental Examples 6-1 to 6-6) -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]
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., it was performed in the same manner as Experimental Example 5-12 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]
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., the same procedure as in Experimental Example 5-13 was performed to obtain rods (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]
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., the same procedure as in Experimental Example 5-14 was performed to obtain rods (Experimental Examples 6-10 to 6-6) -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]
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., the same procedure as in Experimental Example 5-15 was performed to obtain rods (Experimental Examples 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 to 3-20, Experimental Examples 4-1 to 4-3, 4-7 to 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 -1-6-3, 6-7-6-15.

[Experimental Example 7-1]
The materials were weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, and then hot hammer forging, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar material having a processing rate (reduction rate of cross-sectional area) of 70% with respect to the bar material before processing was obtained.
Subsequently, the bar having a processing rate of 70% was subjected to curing heat treatment at 600 ° C. for 1 hour in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod of Fe—Mn alloy was obtained.

[Experimental Examples 7-2 and 7-3]
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., the same procedure as in Experimental Example 7-1 was performed to obtain a bar (Experimental Examples 7-2 and 7-3). .

[Experimental examples 8-1 and 8-2]
A bar of Fe—Mn alloy was obtained in the same manner as in Experimental Example 2-2, except that the cold forging and hardening heat treatment in Experimental Example 2-2 were not performed. That is, the heat treatment and the water cooling of Experimental Example 2-2 were performed to obtain a bar (Experimental Example 8-1).
Moreover, the bar material of the Fe-Mn alloy was obtained like Example 2-2 except not having performed the hardening heat treatment of Example 2-2. That is, it went even to the cold forging of Experimental example 2-2, and obtained the bar (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 material 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 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 bar materials 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 the change in Vickers hardness with respect to the processing rate for an Fe—Mn alloy sample. About Experimental example 1-1 to 1-25, it has shown with the graph according to hardening heat processing time. FIG. 2 is a diagram showing the change in Vickers hardness with respect to the heat treatment temperature for the Fe—Mn alloy sample. About Experimental Examples 1-11 to 1-15 and Experimental Examples 2-1 to 2-15, it shows with a graph according to a processing rate.
FIG. 3 is a diagram showing a change in Vickers hardness with respect to the processing rate for an Fe—Mn alloy sample. About Experimental example 3-1 to 3-25, it has shown with the graph according to hardening heat processing time. FIG. 4 is a diagram showing the change in Vickers hardness with respect to the heat treatment temperature for the Fe—Mn alloy sample. About Experimental example 3-11 to 3-15 and Experimental example 4-1 to 4-15, it has shown with the graph according to a processing rate.
FIG. 5 is a diagram showing the change in Vickers hardness with respect to the processing rate for an Fe—Mn alloy sample. About Experimental example 5-1 to 5-25, it has shown with the graph according to hardening heat processing time. FIG. 6 is a diagram showing the change in Vickers hardness with respect to the heat treatment temperature for the Fe—Mn alloy sample. About Experimental example 5-11 to 5-15 and Experimental example 6-1 to 6-15, it has shown with the graph according to processing rate. In addition, the processing rate of FIGS. 1-6 is a processing rate in cold forging.

<SEM image observation>
The bar material finally obtained in Experimental Example 7-1 was observed using a reflection 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 diagrams showing SEM images of Fe—Mn alloy samples. That is, it is a SEM image about the bar material of Experimental Examples 7-1 to 7-3, respectively. The gray portion is the β-Mn phase and the black portion is the α phase. The two phases were identified from the result of electron diffraction pattern analysis described later. That is, the pattern of the electron diffraction pattern in the gray color portion was consistent with Mn _0.375 Fe _0.375 Al _0.25 having a β-Mn structure. Further, the pattern of the electron diffraction pattern in the black portion coincided with the pattern of α-Fe having an α phase structure.

The area fraction was evaluated based on an SEM image and / or an EBSD image taken by an EBSD (Electron Back Scattering Diffraction Method) attached to the SEM. In the SEM image, the respective area fractions are 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 color maps. The fraction was determined.
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 area fraction of the β-Mn phase was 60%, and the area fraction of the α phase was 40%. In Experimental Example 7-3, the area fraction of the β-Mn phase was 75%, and the area fraction of the α phase was 25%.
In other experimental examples corresponding to the examples, it is considered that the finally obtained bar includes a β-Mn phase and an α phase as a 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 thought that it is 40% or less.
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 an Fe—Mn alloy sample. That is, it is an X-ray diffraction pattern of the bar material of Experimental Example 1-1. The diffraction peaks of the α-Fe phase and the β-Mn phase, and the diffraction peak of Cr carbide were observed.

<TEM image observation>
The rod finally obtained in Experimental Example 2-2 was observed using a transmission electron microscope (TEM). Here, a HAADF image (HAADF-STEM image), which is a kind of STEM image, was obtained. A HAADF (High Angle Annular Dark-Field) image is obtained by detecting an STEM (Scanning Transmission Electron Microscopy) image scattered at a high angle among transmitted electrons with a ring 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 an 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 result of mapping by STEM-EDS for an Fe—Mn alloy sample. FIG. 12B is an enlarged view of a part of the mapping of FIG. 12A. FIGS. 11B and 12B are enlarged views of the rectangular frames in FIGS. 11A and 12A, respectively. These are the results for the bar finally obtained in Experimental Example 2-2.
FIG. 13A is a diagram showing a HAADF-STEM image of an 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 a result of mapping by STEM-EDS for an Fe—Mn alloy sample. FIG. 14B is an enlarged view of a part of the mapping of FIG. 14A. FIGS. 13B and 14B are enlarged views of the rectangular frames in 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 an 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 a result of mapping by STEM-EDS for an Fe—Mn alloy sample. FIG. 16B is an enlarged view of a part of the mapping of FIG. 16A. FIGS. 15B and 16B are enlarged views of the rectangular frames in FIGS. 15A and 15A, respectively. These are the results for the bar material finally obtained in Experimental Example 8-2.

  11A to 16B, the Fe—Mn alloy of Experimental Example 2-2 obtained through cold forging and hardening heat treatment has a β-Mn phase and an α phase. The hot-worked product of Experimental Example 8-1 obtained up to the hot working has a γ phase and an α phase. No dislocation is observed in the γ-phase and α-phase metal crystals. The cold forged product of Experimental Example 8-2 obtained by performing the 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 dislocation is introduced into the metal crystal by cold forging, transformation from γ phase to β-Mn phase occurs during the curing heat treatment.

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

  From FIG. 17A to FIG. 17C, the part surrounded by the dotted line in FIG. 17A can be identified as the β-Mn phase. 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 for the bar finally obtained in Experimental Example 7-1. Specifically, it is an electron diffraction pattern of a gray portion in FIG. Results of a phase analysis by electron diffraction pattern, as shown in FIG. _{18 (0.375 Fe 0.375 Al 0.25 [} 011] plane electron diffraction pattern Mn), Fe-Mn alloy to contain beta-Mn phase after hardening heat treatment of 600 ° C. confirmed.

[Experimental example 9-1]
The materials were weighed in a composition ratio of 30% Mn, 8% Al, 0.5% C, 10% Cr, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar having a processing rate (reduction rate of cross-sectional area) of 80% with respect to the bar before processing was obtained.
Subsequently, the bar with a processing rate of 80% was subjected to a curing heat treatment at 550 ° C. for 12 hours in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod of Fe—Mn alloy was obtained.

[Experimental Example 9-2]
An Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-1 except that the cast ingot obtained as described below was used.
The materials were weighed at a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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 materials were weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 2.5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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, followed by hot groove roll rolling. By this hot working, a bar having a working rate (reduction rate of 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 swaging forging was performed on the rod after water cooling. By this cold forging, a bar having a processing rate (reduction rate of cross-sectional area) of 80% with respect to the bar before processing was obtained.
Subsequently, the bar with a processing rate of 80% was subjected to curing heat treatment at 600 ° C. for 12 hours in an atmospheric furnace, and air-cooled. By this hardening heat treatment, a rod of Fe—Mn alloy was obtained.

[Experimental Example 9-4]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The materials were weighed in a composition ratio of 30% Mn, 8% Al, 1% C, 10% Cr, 7.5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The materials were weighed in a composition ratio of 25% Mn, 8% Al, 1% C, 10% Cr and the balance Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The material was weighed in a composition ratio of 20% Mn, 20% Mn, 8% Al, 1% C, 10% Cr, 5% Ni and the balance Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The materials were weighed in a composition ratio of 30% Mn, 8% Al, 1.5% C, 10% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The materials were weighed at a composition ratio of 30% Mn, 8% Al, 1.5% C, 5% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The material was weighed in a composition ratio of 30% Mn, 10% Al, 1% C, 10% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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]
Except for using the cast ingot obtained as described below, an Fe—Mn alloy bar was obtained in the same manner as in Experimental Example 9-3.
The materials were weighed in a composition ratio of 30% Mn, 5% Al, 1% C, 10% Cr, 5% Ni, and the balance being Fe. Next, these materials were melted in a crucible using a high-frequency vacuum melting apparatus 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>
Vickers hardness was measured by the above-described method using the bar material finally obtained in Experimental Example 9-1. The bar materials 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. In addition, it shows collectively about the measurement result etc. of the Vickers hardness of Experimental example 3-1 and Experimental example 7-1.

<Area fraction>
About the bar material finally obtained in Experimental Example 9-2, the area fraction was determined by the method described above. In Experimental Example 9-2, the area fraction of the β-Mn phase was 85%, and the area fraction of the α phase was 15%.

Claims (7)

As component composition, 20.0 mass% or more and 30.0 mass% or less Mn, 5.0 mass% or more and 10.0 mass% or less Al, 0.5 mass% or more and 1.5 mass% or less C, and Containing 5.0 mass% or more and 10.0 mass% or less of Cr, the balance being Fe and inevitable impurities,
An Fe—Mn alloy containing a β-Mn phase and an α phase as a metal structure.   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%. The Fe-Mn alloy according to claim 1, wherein the Fe-Mn alloy is 1% or less.   The Fe-Mn alloy according to claim 1 or 2, further comprising 2.5 mass% or more and 10.0 mass% or less of Ni as the component composition. A hot working process for hot working an ingot to obtain a hot work product;
A cold forging step of cold forging the hot workpiece obtained in the hot working step to obtain a cold forging; and
A hardening heat treatment step of hardening and heat-treating the cold forging obtained in the cold forging step to obtain a Fe-Mn alloy,
The ingot has a component composition of 20.0 mass% to 30.0 mass% Mn, 5.0 mass% to 10.0 mass% Al, 0.5 mass% to 1.5 mass%. C and 5.0 mass% or more and 10.0 mass% or less of Cr, the balance being Fe and unavoidable impurities, including a γ phase and an α phase as a metal structure,
The Fe—Mn alloy has a component composition of 20.0% by mass to 30.0% by mass Mn, 5.0% by mass to 10.0% by mass Al, 0.5% by mass to 1.5% by mass. Fe- containing not more than C% by mass, and not less than 5.0% by mass and not more than 10.0% by mass of Cr, the balance being Fe and inevitable impurities, and including a β-Mn phase and an α-phase as a metal structure A method for producing a Mn alloy. The hot-worked product has an area fraction of the γ phase of 60% or more and 90% or less when the sum of the area fraction of the γ phase and the α phase is 100%, and the area fraction of the α phase is 10%. % To 40%,
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%. The manufacturing method of the Fe-Mn alloy of Claim 4 whose rate is 10% or more and 40% or less.   The said cold forging process is a manufacturing method of the Fe-Mn alloy of Claim 4 or 5 which cold-forges the said hot work product with a process rate of 20% or more and 80% or less.   The said hardening heat treatment process is a manufacturing method of the Fe-Mn alloy of any one of Claims 4-6 which heat-treats the said cold forging at 550 degreeC or more and 800 degrees C or less.