Hot-rolled medium manganese steel with excellent high-temperature mechanical property and preparation method thereof

Abstract

The invention belongs to the technical field of metal material heat treatment, and relates to hot-rolled medium manganese steel with excellent high-temperature mechanical property and a preparation method thereof, the hot-rolled medium manganese steel with excellent high-temperature mechanical property is prepared by adopting homogenizing annealing, rough hot rolling, fine hot rolling and ferrite phase change coupling processes, the yield strength at 500 DEG C is 430-670MPa, the tensile strength is 590-750MPa, and the tensile strength is 590-750MPa. The elongation after fracture is 25-28%, the problem of insufficient high-temperature strength of the medium manganese steel is solved, good matching of the strength and plasticity of the medium manganese steel used in the high-temperature environment is achieved, and the application field of the medium manganese steel is widened.

Description

Technical Field

[0001] The invention relates to the technical field of heat treatment of metal materials, in particular to a hot-rolled medium manganese steel with excellent high-temperature mechanical properties and a preparation method thereof. Background Art

[0002] Medium manganese steel has the advantages of low price and excellent mechanical properties at room temperature, so it is highly expected by aviation, navigation, energy, transportation and other fields. However, the poor high-temperature mechanical properties of medium manganese steel make it difficult to meet the needs of some components for high-temperature environments. Microstructure control is an important scientific basis for determining the development of advanced metal materials. To this end, grain boundary engineering, gradient organization, dislocation engineering, composite phase transformation, heterogeneous structure, multiphase organization, precipitation phase control and other means are widely used in the microstructure control of medium manganese steel. However, high temperature environment will cause grain growth, coarsening of precipitation particles and reduced stability of austenite, thereby deteriorating its high-temperature mechanical properties. The above factors lead to the use of multi-stage step-by-step control strategies in the preparation of high-strength medium manganese steel, such as hot / cold / warm rolling process combined with quenching-partitioning, quenching-partitioning-tempering, quenching-partitioning-annealing-tempering and other processes. Complex and long-cycle thermal-mechanical coupling processing technology is difficult to significantly improve the strength and is not conducive to industrial production. It can be seen that it is urgent to optimize the existing medium manganese steel hot processing process to solve the above-mentioned organizational control problems. Summary of the invention

[0003] In order to solve the problems existing in the prior art, the main purpose of the present invention is to provide a hot-rolled medium manganese steel with excellent high-temperature mechanical properties and a preparation method thereof.

[0004] To solve the above technical problems, according to one aspect of the present invention, the present invention provides the following technical solutions: A method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises the following steps: S1. Homogenization annealing: the medium manganese steel ingot is subjected to homogenization annealing to obtain an annealed ingot; S2, rough hot rolling: annealing the ingot and performing rough hot rolling, and then water cooling to room temperature to obtain a rough hot rolled plate; S3, finishing hot rolling: the rough hot rolled plate is put into the furnace to be kept warm, and then finished hot rolled and air cooled to room temperature to obtain the finished hot rolled plate; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at the required temperature, and then the ferrite phase transformation process is carried out and the plate is air-cooled to room temperature to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0005] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, the hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises, by mass percentage, C: 0.35-0.50%, Mn: 9.5-11.0%, Al: 2.0-3.0%, V: 0.5-0.7%, and the remainder is Fe and unavoidable impurities.

[0006] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, the method further comprises, before step S1, S0, smelting the medium manganese steel ingot: preparing ingredients according to the composition of the medium manganese steel, and adding the ingredients to the furnace cavity of a vacuum induction melting furnace in the order of the melting points of the elements from low to high, the smelting temperature being 1400-1500°C, and casting the ingot into a mold after the smelting is completed, and air cooling to room temperature.

[0007] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, wherein: in the step S1, the homogenization annealing temperature is 1100-1150°C, the annealing time is 2-4h, and the cooling method is air cooling.

[0008] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, wherein: in the step S2, the rough hot rolling is divided into 3 to 4 passes, the total deformation of the rough hot rolling is 65 to 75%, the initial rolling temperature is 1000 to 1050°C, and the final rolling temperature is 950 to 1000°C.

[0009] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, wherein: in the step S3, the holding temperature is 640-660°C, and the holding time is 10-60 min; the finishing hot rolling is divided into 1-3 passes, and the total deformation of the finishing hot rolling is 40-50%; the final rolling temperature is 580-600°C.

[0010] As a preferred embodiment of the method for preparing a hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, wherein: in the step S4, the holding temperature is 490-510°C, and the holding time is 10-30 minutes.

[0011] To solve the above technical problem, according to another aspect of the present invention, the present invention provides the following technical solution: A hot-rolled medium manganese steel with excellent high-temperature mechanical properties is prepared by adopting the preparation method of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0012] As a preferred embodiment of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, the yield strength of the hot-rolled medium manganese steel under high-temperature deformation conditions of 500°C is 430~670MPa, the tensile strength is 590~750MPa, and the elongation after fracture is 25~28%.

[0013] As a preferred embodiment of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties described in the present invention, the matrix structure of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties includes 45~56vol% austenite and 44~55vol% ferrite / martensite, and the precipitated phase includes nano-cementite and vanadium carbide particles.

[0014] The beneficial effects of the present invention are as follows: The present invention proposes a hot-rolled medium manganese steel with excellent high-temperature mechanical properties and a preparation method thereof. The hot-rolled medium manganese steel with excellent high-temperature mechanical properties is prepared by adopting homogenization annealing, rough hot rolling, fine hot rolling and ferrite phase transformation coupling processes. The yield strength of the prepared hot-rolled medium manganese steel at 500°C is 430-670MPa, the tensile strength is 590-750MPa, and the elongation after fracture is 25-28%. The problem of "insufficient high-temperature strength" of the medium manganese steel is solved, a good match between the strength and plasticity of the medium manganese steel for high-temperature environments is achieved, and its application field is broadened. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0016] Figure 1 These are the SEM and TEM images of the hot-rolled medium manganese steel of Example 1 of the present invention.

[0017] Figure 2 These are the SEM and TEM images of the hot-rolled medium manganese steel according to Example 2 of the present invention.

[0018] Figure 3 These are the SEM and TEM images of the hot-rolled medium manganese steel of Example 3 of the present invention.

[0019] Figure 4 This is the SEM image of the hot-rolled medium manganese steel of Comparative Example 1 of the present invention.

[0020] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0021] The following will be described clearly and completely in conjunction with the technical solutions in the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] In view of the complex multiphase structure characteristics of medium manganese steel, the present invention adopts dual-phase rolling deformation to replace the traditional rolling + dual-phase annealing process, refines the structure and prepares austenite with a sufficient volume fraction; then, the ferrite phase transformation process is used to replace the traditional tempering process, and the decomposition of unstable austenite is accelerated to form fine-grained ferrite and nano-cementite particles. At the same time, the lower ferrite phase temperature can promote the precipitation of nano-vanadium carbide and retain a higher density of dislocations, and obtain stable austenite, fine-grained ferrite, and high-density nano double precipitation (cementite and vanadium carbide) particles. The multiphase structure prepared by this simplified processing technology can reasonably regulate the problems of grain growth, coarsening of precipitation particles and reduced austenite stability, and is expected to break through the bottleneck of "insufficient high temperature strength" of medium manganese steel, which is of great significance to the future development of medium manganese steel.

[0023] According to one aspect of the present invention, the present invention provides the following technical solution: A method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises the following steps: S1. Homogenization annealing: the medium manganese steel ingot is subjected to homogenization annealing to obtain an annealed ingot; S2, rough hot rolling: annealing the ingot and performing rough hot rolling, and then water cooling to room temperature to obtain a rough hot rolled plate; S3, finishing hot rolling: the rough hot rolled plate is put into the furnace to be kept warm, and then finished hot rolled and air cooled to room temperature to obtain the finished hot rolled plate; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at the required temperature, and then the ferrite phase transformation process is carried out and the plate is air-cooled to room temperature to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0024] Preferably, the hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises, by mass percentage, C: 0.35-0.50%, Mn: 9.5-11.0%, Al: 2.0-3.0%, V: 0.5-0.7%, and the remainder is Fe and unavoidable impurities.

[0025] Preferably, before step S1, the step further includes: S0, smelting medium manganese steel ingot: preparing ingredients according to the composition of medium manganese steel, adding them to the furnace chamber of a vacuum induction melting furnace in order of the melting points of the elements from low to high, with a smelting temperature of 1400-1500°C, casting them into ingots in a mold after smelting, and air cooling them to room temperature. Specifically, the smelting temperature can be, for example, any one of 1400°C, 1420°C, 1440°C, 1460°C, 1480°C, 1500°C, or a range between any two of them.

[0026] Preferably, in step S1, the homogenization annealing temperature is 1100-1150°C, the annealing time is 2-4h, and the cooling method is air cooling. Specifically, the homogenization annealing temperature can be, for example, any one of 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, or a range between any two thereof; the annealing time can be, for example, any one of 2h, 3h, 4h, or a range between any two thereof.

[0027] Preferably, in step S2, the rough hot rolling is divided into 3 to 4 passes, the total deformation of the rough hot rolling is 65 to 75%; the starting rolling temperature is 1000 to 1050°C, and the final rolling temperature is 950 to 1000°C. Specifically, the total deformation of the hot rolling can be, for example, any one of 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, or any range between two of them; the starting rolling temperature can be, for example, any one of 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, or any range between two of them; the final rolling temperature can be, for example, any one of 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, or any range between two of them.

[0028] Preferably, in step S3, the holding temperature is 640-660°C, the holding time is 10-60min; the finishing hot rolling is divided into 1-3 passes, the total deformation of the finishing hot rolling is 40-50%; the final rolling temperature is 580-600°C. Specifically, the finishing hot rolling holding temperature can be, for example, any one of 640°C, 645°C, 650°C, 655°C, 660°C or any range between two; the finishing hot rolling holding time can be, for example, any one of 10min, 20min, 30min, 40min, 50min, 60min or any range between two; the total deformation of the finishing hot rolling can be, for example, any one of 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50% or any range between two; the final rolling temperature can be, for example, any one of 580°C, 585°C, 590°C, 595°C, 600°C or any range between two.

[0029] Preferably, in step S4, the insulation temperature is 490-510°C, and the insulation time is 10-30 min. Specifically, the insulation temperature can be, for example, any one of 490°C, 495°C, 500°C, 505°C, 510°C, or any range between two thereof; the insulation time can be, for example, any one of 10 min, 15 min, 20 min, 25 min, 30 min, or any range between two thereof.

[0030] According to another aspect of the present invention, the present invention provides the following technical solution: A hot-rolled medium manganese steel with excellent high-temperature mechanical properties is prepared by the above-mentioned preparation method of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties. The hot-rolled medium manganese steel with excellent high-temperature mechanical properties has a yield strength of 430-670 MPa under 500°C high-temperature deformation conditions, a tensile strength of 590-750 MPa, and an elongation after fracture of 25-28%.

[0031] Preferably, the matrix structure of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties includes 45-56 vol% austenite and 44-55 vol% ferrite / martensite, and the precipitated phase includes nano-cementite and vanadium carbide particles.

[0032] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0033] The medium manganese steel used in the comparative examples of each embodiment is prepared by the following method: prepare the ingredients according to the composition of the medium manganese steel, add them into the furnace cavity of a vacuum induction melting furnace in the order of the melting points of the elements from low to high, and the melting temperature is 1400~1500℃. After the melting is completed, cast into an ingot in a mold and air-cooled to room temperature.

[0034] The chemical composition of medium manganese steel ingot is shown in Table 1.

[0035] Table 1 Chemical composition (mass percentage) of medium manganese steel ingots of various embodiments High-temperature tensile test conditions for the medium manganese steel prepared in each embodiment and comparative example: the hot-rolled medium manganese steel is rapidly heated to the deformation temperature in an electronic universal tensile testing machine equipped with a heating device, and then subjected to high-temperature tensile deformation: the deformation temperature is 500°C, the holding time is 10min, the heating rate is 20°C / s, and the deformation rate is 0.5mm / min.

[0036] Example 1 A method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises the following steps: S1. Homogenization annealing: the medium manganese steel ingot is homogenized to obtain an annealed ingot; the homogenization annealing temperature is 1130°C, the annealing time is 3h, and the cooling method is air cooling; S2. Rough hot rolling: The annealed ingot is subjected to rough hot rolling, and the rough hot rolled plate is obtained after water cooling to room temperature; the initial rolling temperature is 1020°C, and the final rolling temperature is 980°C; the rough hot rolling is divided into 4 passes, and the total deformation of the rough hot rolling is 70%; S3, finishing hot rolling: the rough hot rolled plate is kept warm by entering the furnace at the temperature, and then the finishing hot rolled plate is air-cooled to room temperature after finishing hot rolling; the holding temperature is 650℃, and the holding time is 60min; the finishing hot rolling is divided into 2 passes, and the total deformation of the finishing hot rolling is 50%; the final rolling temperature is 590℃; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at a temperature of 500°C for 30 minutes. The plate is then air-cooled to room temperature after a ferrite phase transformation process to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0037] The microstructure of the hot-rolled medium manganese steel prepared in this embodiment is as follows: Figure 1 As shown ( Figure 1 The middle left picture is a SEM picture. Figure 1 The middle right figure is a TEM image), its matrix structure includes 56 vol% austenite and 44 vol% ferrite / martensite as well as high-density nano-cementite and vanadium carbide particles. The hot-rolled medium manganese steel prepared in this embodiment has a yield strength of 670 MPa, a tensile strength of 736 MPa, and an elongation after fracture of 27% under high-temperature deformation conditions of 500°C.

[0038] Example 2 A method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises the following steps: S1. Homogenization annealing: the medium manganese steel ingot is homogenized to obtain an annealed ingot; the homogenization annealing temperature is 1130°C, the annealing time is 3h, and the cooling method is air cooling; S2. Rough hot rolling: The annealed ingot is subjected to rough hot rolling, and the rough hot rolled plate is obtained after water cooling to room temperature; the initial rolling temperature is 1020°C, and the final rolling temperature is 980°C; the rough hot rolling is divided into 4 passes, and the total deformation of the rough hot rolling is 70%; S3, finishing hot rolling: the rough hot rolled plate is kept warm by entering the furnace at the temperature, and then the finishing hot rolled plate is air-cooled to room temperature after finishing hot rolling; the holding temperature is 650℃, and the holding time is 30min; the finishing hot rolling is divided into 2 passes, and the total deformation of the finishing hot rolling is 50%; the final rolling temperature is 590℃; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at a temperature of 500°C for 30 minutes. The plate is then air-cooled to room temperature after a ferrite phase transformation process to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0039] The microstructure of the hot-rolled medium manganese steel prepared in this embodiment is as follows: Figure 2 As shown ( Figure 2 The middle left picture is a SEM picture. Figure 2 The middle right figure is a TEM image), its matrix structure includes 52 vol% austenite and 48 vol% ferrite / martensite as well as relatively high density nano cementite and vanadium carbide particles. The hot-rolled medium manganese steel prepared in this embodiment has a yield strength of 569 MPa, a tensile strength of 710 MPa, and an elongation after fracture of 25% under high temperature deformation conditions of 500°C.

[0040] Example 3 A method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises the following steps: S1. Homogenization annealing: the medium manganese steel ingot is homogenized to obtain an annealed ingot; the homogenization annealing temperature is 1130°C, the annealing time is 3h, and the cooling method is air cooling; S2. Rough hot rolling: The annealed ingot is subjected to rough hot rolling, and the rough hot rolled plate is obtained after water cooling to room temperature; the initial rolling temperature is 1020°C, and the final rolling temperature is 980°C; the rough hot rolling is divided into 4 passes, and the total deformation of the rough hot rolling is 70%; S3, finishing hot rolling: the rough hot rolled plate is kept warm by entering the furnace at the temperature, and then the finishing hot rolled plate is air-cooled to room temperature after finishing hot rolling; the holding temperature is 650℃, and the holding time is 10min; the finishing hot rolling is divided into 2 passes, and the total deformation of the finishing hot rolling is 50%; the final rolling temperature is 590℃; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at a temperature of 500°C for 30 minutes. The plate is then air-cooled to room temperature after a ferrite phase transformation process to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

[0041] The microstructure of the hot-rolled medium manganese steel prepared in this embodiment is as follows: Figure 3 As shown ( Figure 3 The middle left picture is a SEM picture. Figure 3 The middle right figure is a TEM image), its matrix structure includes 45vol% austenite and 55vol% ferrite / martensite as well as relatively high-density nano-cementite and vanadium carbide particles. The hot-rolled medium manganese steel prepared in this embodiment has a yield strength of 430MPa, a tensile strength of 591MPa, and an elongation after fracture of 28% under high-temperature deformation conditions of 500°C.

[0042] Comparative Example 1 The difference from Embodiment 1 is that step S4 is not performed.

[0043] The SEM image of the medium manganese steel prepared in this comparative example is as follows Figure 4 As shown, its matrix structure is 69 vol% austenite and 31 vol% ferrite / martensite, and the precipitated phases include low-density nano-cementite and vanadium carbide particles; the yield strength under high temperature deformation conditions of 500°C is 452 MPa, the tensile strength is 536 MPa, and the elongation after fracture is 30%.

[0044] Comparative Example 2 The difference from Example 1 is that the holding temperature in step S4 is 450°C.

[0045] The medium manganese steel matrix structure prepared in this comparative example includes 43 vol% austenite and 57 vol% ferrite / martensite, and the precipitated phase includes low-density nano-cementite and vanadium carbide particles. The yield strength under high-temperature deformation conditions of 500°C is 580 MPa, the tensile strength is 635 MPa, and the elongation after fracture is 19.5%.

[0046] It can be seen from the embodiments and comparative examples of the present invention that the hot-rolled medium manganese steel with excellent high-temperature mechanical properties prepared by the present invention through homogenization annealing, rough hot rolling, fine hot rolling and ferrite phase transformation coupling process has a yield strength of 430-670 MPa at 500°C, a tensile strength of 590-750 MPa, and an elongation after fracture of 25-28%, which breaks through the problem of "insufficient high-temperature strength" of medium manganese steel, achieves a good match between strength and plasticity of medium manganese steel for high-temperature environments, and broadens its application field.

[0047] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties, characterized in that: The steps include: S1. Homogenization annealing: the medium manganese steel ingot is subjected to homogenization annealing to obtain an annealed ingot; S2, rough hot rolling: annealing the ingot and performing rough hot rolling, and then cooling the ingot to room temperature to obtain a rough hot rolled plate; S3, finishing hot rolling: the rough hot rolled plate is put into the furnace to be kept warm, and then finished hot rolled and air cooled to room temperature to obtain the finished hot rolled plate; S4. Ferrite phase transformation process: The hot-rolled plate is kept warm by being put into the furnace at the required temperature, and then the ferrite phase transformation process is carried out and the plate is air-cooled to room temperature to obtain a hot-rolled medium manganese steel with excellent high-temperature mechanical properties.

2. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: The hot-rolled medium manganese steel with excellent high-temperature mechanical properties comprises, by mass percentage, 0.35-0.50% C, 9.5-11.0% Mn, 2.0-3.0% Al, 0.5-0.7% V, and the remainder being Fe and unavoidable impurities.

3. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: Before step S1, the method further includes: S0, smelting medium manganese steel ingot: preparing ingredients according to the composition of medium manganese steel, adding the ingredients into the vacuum induction melting furnace in the order of the melting points of the elements from low to high, the smelting temperature is 1400-1500° C., and after the smelting is completed, casting the ingot into an ingot in a mold and air cooling it to room temperature.

4. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: In the step S1, the homogenization annealing temperature is 1100-1150° C., the annealing time is 2-4 hours, and the cooling method is air cooling.

5. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: In step S2, the initial rolling temperature is 1000-1050°C, and the final rolling temperature is 950-1000°C; the rough hot rolling is divided into 3-4 passes, and the total deformation of the rough hot rolling is 65-75%.

6. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: In step S3, the holding temperature is 640-660°C, and the holding time is 10-60 minutes; the finishing hot rolling is divided into 1-3 passes, and the total deformation of the finishing hot rolling is 40-50%; the final rolling temperature is 580-600°C.

7. The method for preparing hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 1, characterized in that: In step S4, the insulation temperature is 490-510° C., and the insulation time is 10-30 min.

8. A hot-rolled medium manganese steel with excellent high temperature mechanical properties, characterized in that: The steel is prepared by the method for preparing hot-rolled medium manganese steel with excellent high-temperature mechanical properties as described in any one of claims 1 to 7.

9. The hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 8, characterized in that: The yield strength of hot-rolled medium manganese steel under high temperature deformation conditions of 500℃ is 430~670MPa, the tensile strength is 590~750MPa, and the elongation after fracture is 25~28%.

10. The hot-rolled medium manganese steel with excellent high temperature mechanical properties according to claim 8, characterized in that: The matrix structure of the hot-rolled medium manganese steel with excellent high-temperature mechanical properties includes 45-56 vol% of austenite and 44-55 vol% of ferrite / martensite, and the precipitated phase includes nano-cementite and vanadium carbide particles.

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