A short-process high-strength high-manganese high-aluminum austenitic lightweight steel and a preparation method thereof

Abstract

The application discloses a short-process high-strength high-manganese high-aluminum austenitic lightweight steel and a preparation method thereof, and belongs to the technical field of ultrahigh-strength steel.The specific proportion of alloy is cast into an ingot by adopting a vacuum melting technology, and then the high-strength high-manganese high-aluminum austenitic lightweight steel with a tensile strength of 1600MPa-1800MPa, a yield strength of 1430MPa-1800MPa and an elongation of 8%-15% is prepared through heating, forging, hot rolling, room-temperature cold rolling and low-temperature short-time aging.The method provided by the application only adopts a cold rolling and one-time low-temperature aging treatment process, thereby avoiding the problems of multiple long-time high-temperature heat treatments before and after cold rolling, greatly shortening a production cycle, shortening a production process, reducing production cost and energy consumption.Meanwhile, the lightweight steel prepared by adopting the method of the application is composed of austenitic structures and kappa carbides, and the volume fraction of recrystallized grains after aging treatment is low, so that the comprehensive mechanical properties of the material are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high strength steel technology, specifically relating to a short-process high-strength, high-manganese, high-alumina austenitic lightweight steel and its preparation method. Background Technology

[0002] In recent years, as energy conservation and emission reduction have become a global consensus, lightweight materials are imperative in order to achieve my country's carbon neutrality goals. Steel is widely used in various industries and plays a role that other lightweight materials cannot replace. Therefore, in order to achieve the established plans while ensuring safety, the development of a new type of high-strength lightweight material has become increasingly urgent.

[0003] High-manganese, high-alumina lightweight steel, as a newly emerging type of lightweight steel in recent years, has attracted increasing attention due to its significant weight reduction potential. Currently, high-strength high-manganese, high-alumina lightweight steel is mainly prepared through long-term annealing and aging treatment. This process is complex, cumbersome, and costly, greatly limiting the application of this series of lightweight steels. Therefore, there is a need to develop a short-process, high-strength, high-manganese, high-alumina austenitic lightweight steel and its preparation method. Summary of the Invention

[0004] To address the shortcomings of current technologies, this invention provides a short-process, high-strength, high-manganese, high-alumina austenitic lightweight steel and its preparation method. Through process design, the long-duration, multiple-annealing process required in the preparation process is avoided, while achieving ultra-high strength.

[0005] The first aspect of this invention provides a method for preparing high-strength, high-manganese, high-alumina austenitic lightweight steel using a short-process method, the method comprising the following steps:

[0006] (1) According to the composition of short-process high-strength high-manganese high-alumina austenitic light steel, vacuum melting technology is used to cast it into ingots;

[0007] (2) Heat the billet to 1170℃~1230℃, hold it for 1h~3h, and then forge it into a slab and air cool it to room temperature;

[0008] (3) Heat the air-cooled slab to 1100℃~1250℃, hold for 2h~4h, and then air-cool to room temperature after rolling;

[0009] (4) The hot-rolled plate from step (3) is cold-rolled at room temperature;

[0010] (5) Heat the cold-rolled plate in step (4) to the aging temperature range, that is, control the temperature at 400℃~650℃, hold for 15min~6h, and quench in water to room temperature to obtain high-strength single-aging lightweight steel.

[0011] In further step (3), the total hot rolling reduction is 80%~95%, and the hot-rolled plate is rolled into a thickness of 4.0mm~5.0mm.

[0012] In further step (4), the total cold rolling reduction is 75%~85%, and the material is cold rolled into a sheet with a thickness of 0.8mm~1.2mm.

[0013] In further step (5), after the high-strength austenitic lightweight steel is aged, the recrystallized grain size of the microstructure is less than 2 μm and the recrystallization ratio is less than 15%.

[0014] The second aspect of this invention provides a high-strength, high-manganese, high-aluminum austenitic lightweight steel, prepared by the above method. The chemical composition of the lightweight steel, by chemical mass ratio, is: C: 0.6%-1.2%, Mn: 18%-24%, Al: 5.1%-8.1%, with the balance being Fe and its unavoidable impurities.

[0015] The lightweight steel has a tensile strength of 1600MPa~1800MPa, a yield strength of 1430MPa~1800MPa, and an elongation of 8%~15%.

[0016] The lightweight steel is composed of austenitic structure and κ carbides.

[0017] The principle of this invention is:

[0018] The high-manganese, high-alumina lightweight steel of this invention, with appropriate addition of Al, significantly reduces the steel's density. This invention employs a short process, achieving age strengthening through κ carbide precipitation after a lower temperature heat treatment, while simultaneously introducing a small amount of recrystallized structure within the material. The intragranular κ carbides after aging treatment alter the mechanical properties between the recrystallized and non-recrystallized structures, reducing incompatibility between different structures during deformation, preventing premature stress concentration that could lead to premature material failure, and thus improving the overall mechanical properties of the material.

[0019] Compared with the prior art, the advantages of this invention are:

[0020] 1. This invention provides high-strength, high-manganese, high-alumina austenitic lightweight steel alloy plates with a tensile strength of 1600MPa~1800MPa, a yield strength of 1430MPa~1800MPa, and an elongation of 8%~15%. The preparation process is simple, the process is short, and the application range is wide, which can meet the requirements of multiple industries. The production process only adopts cold rolling and one low-temperature aging treatment (400℃~650℃), avoiding the problem of multiple long-term high-temperature heat treatments (>700℃) before and after cold rolling, which greatly shortens the production cycle, shortens the production process, and reduces production costs and energy consumption.

[0021] 2. After aging treatment according to this invention, the recrystallized grain volume fraction is low (<15%), and a large amount of unrecrystallized structure is still retained. Typically, the significant difference in mechanical properties between partially recrystallized and unrecrystallized structures leads to premature failure, with elongation usually not exceeding 5%. In the aging process of this invention, intragranular κ carbides improve the overall mechanical properties by reducing the difference in mechanical properties between the crystalline and unrecrystallized regions. This reduces the incompatibility between different structures during deformation, greatly enhancing the overall mechanical properties of the material. Attached Figure Description

[0022] Figure 1 This is a SEM image of the annealed sample in Example 1 of the present invention;

[0023] Figure 2 This is a TEM image of the annealed sample in Example 1 of the present invention;

[0024] Figure 3 This is the XRD pattern of the annealed sample in Example 1 of the present invention;

[0025] Figure 4 This is the stress-strain curve of the annealed sample in Example 1 of the present invention. Detailed Implementation

[0026] This invention provides a short-process method for preparing high-strength, high-manganese, high-alumina austenitic lightweight steel, which includes the following steps:

[0027] (1) Light steel with the following composition by chemical mass ratio: C: 0.6%-1.2%, Mn: 18%-24%, Al: 5.1%-8.1%, balance Fe and its unavoidable impurities, is cast into ingots using vacuum melting technology;

[0028] (2) Heat the billet to 1170℃~1230℃, hold for 1h~3h, forge into a slab and air cool to room temperature;

[0029] (3) After air cooling, the slab is heated to 1100℃~1250℃ and held for 2h~4h. Then, it is rolled into a hot-rolled plate with a thickness of 4.0mm-5.0mm with a total reduction of 80%~95%, and then air-cooled to room temperature.

[0030] (4) After air cooling, the hot-rolled plate is cold-rolled at room temperature, with a total cold rolling reduction of 75%~85%, and the plate is cold-rolled to a thickness of 0.8mm~1.2mm;

[0031] (5) The cold-rolled sheet is heated to 400℃~650℃ and held for 15min~6h, then water-quenched to room temperature to obtain high-strength single-aging lightweight steel. The obtained steel is composed of austenitic structure and κ carbides, with a microstructure recrystallized grain size of less than 2μm and a recrystallization ratio of less than 15%.

[0032] The lightweight steel produced by this invention has a tensile strength of 1600MPa~1800MPa, a yield strength of 1430MPa~1800MPa, and an elongation of 8%~15%.

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0034] Example 1:

[0035] A short-process, high-strength, high-manganese, high-aluminum austenitic lightweight steel, wherein the chemical composition of the lightweight steel, by chemical mass ratio, is: C: 0.8%, Mn: 22%, Al: 6%, with the balance being Fe and its unavoidable impurities.

[0036] (1) According to the chemical composition of a short-process high-strength high-manganese high-alumina austenitic lightweight steel by mass percentage, the steel is cast into ingots using vacuum melting technology.

[0037] (2) Heat the billet to 1200℃, hold it for 3 hours, and then forge it into a slab and air cool it to room temperature;

[0038] (3) Heat the air-cooled slab to 1200℃, hold for 3 hours, with a total reduction of 92%, and hot roll it into a 5mm thick plate. After rolling, air cool to room temperature.

[0039] (4) The hot-rolled plate in step (3) is cold-rolled at room temperature with a total reduction of 80% to form a 1mm thick plate.

[0040] (5) Heat the cold-rolled sheet from step (4) to the aging temperature range, i.e., control the temperature at 550℃, hold for 30 minutes, and water quench to room temperature to obtain high-strength, high-manganese, high-aluminum austenitic lightweight steel, the microstructure of which is as follows: Figure 1 As shown in the figure. The recrystallized structure has a volume fraction of approximately 9%, and the recrystallized grain size is less than 1.5 μm. Its microstructure is as follows. Figure 2 As shown; XRD test results are as follows Figure 3 As shown, the lightweight steel produced is composed of austenite and κ carbides.

[0041] It can be seen that intracrystalline κ carbides are formed in the crystal after heat treatment. As mentioned earlier, the recrystallized fine grains have a high elongation while the crystalline structure has extremely high strength. The huge mechanical energy difference between the two can lead to premature fracture. However, by adjusting the intracrystalline κ carbides, the mechanical incompatibility between the two structures is reduced, thereby achieving good comprehensive mechanical properties.

[0042] The short-process, high-strength, high-manganese, high-alumina austenitic lightweight steel prepared by this invention exhibits a yield strength of 1738 MPa, a tensile strength of 1740 MPa, and an elongation of 9.5% after uniaxial tensile testing. Its stress-strain curve is shown below. Figure 4 As shown.

[0043] Example 2:

[0044] A short-process, high-strength, high-manganese, high-aluminum austenitic lightweight steel, wherein the chemical composition of the lightweight steel, by chemical mass ratio, is: C: 0.8%, Mn: 22%, Al: 6%, with the balance being Fe and its unavoidable impurities.

[0045] (1) According to the chemical composition of a short-process high-strength high-manganese high-alumina austenitic lightweight steel by mass percentage, the steel is cast into ingots using vacuum melting technology.

[0046] (2) Heat the billet to 1200℃, hold it for 3 hours, and then forge it into a slab and air cool it to room temperature;

[0047] (3) Heat the air-cooled slab to 1200℃, hold for 3 hours, with a total reduction of 92%, and hot roll it into a 5mm thick plate. After rolling, air cool to room temperature.

[0048] (4) The hot-rolled plate in step (3) is cold-rolled at room temperature with a total reduction of 80% to form a 1mm thick plate.

[0049] (5) The cold-rolled sheet from step (4) is heated to the aging temperature range, i.e., the temperature is controlled at 575℃, held for 30 minutes, and then quenched in water to room temperature to obtain high-strength, high-manganese, and high-alumina austenitic lightweight steel. The recrystallized structure has a volume fraction of about 11%, and the recrystallized grain size is less than 1μm; the lightweight steel is composed of austenite and κ carbides.

[0050] The short-process high-strength high-manganese high-alumina austenitic lightweight steel prepared by this invention has a yield strength of 1619 MPa, a tensile strength of 1658 MPa, and an elongation of 10.3% after uniaxial stretching.

[0051] Example 3:

[0052] A short-process, high-strength, high-manganese, high-aluminum austenitic lightweight steel, wherein the chemical composition of the lightweight steel, by chemical mass ratio, is: C: 1%, Mn: 22%, Al: 8%, with the balance being Fe and its unavoidable impurities.

[0053] (1) According to the chemical composition of a short-process high-strength high-manganese high-alumina austenitic lightweight steel by mass percentage, the steel is cast into ingots using vacuum melting technology.

[0054] (2) Heat the billet to 1200℃, hold it for 3 hours, and then forge it into a slab and air cool it to room temperature;

[0055] (3) Heat the air-cooled slab to 1200℃, hold for 3 hours, with a total reduction of 87%, and hot roll it into a 5mm thick plate. After rolling, air cool to room temperature.

[0056] (4) The hot-rolled plate in step (3) is cold-rolled at room temperature with a total reduction of 80% to form a 1mm thick plate.

[0057] (5) The cold-rolled sheet from step (4) is heated to the aging temperature range, i.e., the temperature is controlled at 550℃, held for 30 minutes, and then quenched in water to room temperature to obtain high-strength, high-manganese, and high-alumina austenitic lightweight steel. The recrystallized structure has a volume fraction of about 7%, and the recrystallized grain size is less than 1μm; the lightweight steel is composed of austenite and κ carbides.

[0058] The short-process high-strength high-manganese high-alumina austenitic lightweight steel prepared by this invention has a yield strength of 1500 MPa, a tensile strength of 1688 MPa, and an elongation of 12.8% after uniaxial stretching.

[0059] Example 4:

[0060] A short-process, high-strength, high-manganese, high-aluminum austenitic lightweight steel, wherein the chemical composition of the lightweight steel, by chemical mass ratio, is: C: 1%, Mn: 22%, Al: 8%, with the balance being Fe and its unavoidable impurities.

[0061] (1) According to the chemical composition of a short-process high-strength high-manganese high-alumina austenitic lightweight steel by mass percentage, the steel is cast into ingots using vacuum melting technology.

[0062] (2) Heat the billet to 1200℃, hold it for 3 hours, and then forge it into a slab and air cool it to room temperature;

[0063] (3) Heat the air-cooled slab to 1200℃, hold for 3 hours, with a total reduction of 80%, and hot roll it into a 5mm thick plate. After rolling, air cool to room temperature.

[0064] (4) The hot-rolled plate in step (3) is cold-rolled at room temperature with a total reduction of 80% to form a 1mm thick plate.

[0065] (5) The cold-rolled sheet from step (4) is heated to the aging temperature range, i.e., the temperature is controlled at 550℃, held for 3 hours, and then quenched in water to room temperature to obtain high-strength, high-manganese, and high-alumina austenitic lightweight steel. The recrystallized structure has a volume fraction of about 13%, and the recrystallized grain size is less than 1μm; the lightweight steel is composed of austenite and κ carbides.

[0066] The short-process high-strength high-manganese high-alumina austenitic lightweight steel prepared by this invention has a yield strength of 1522 MPa, a tensile strength of 1645 MPa, and an elongation of 9.7% after uniaxial tensile testing.

Claims

1. A method for producing a short-cycle high-strength high-manganese high-aluminum austenitic light steel, characterized by, The method comprises the following steps: S1. According to the composition of the short-process high-strength high-manganese high-aluminum austenitic lightweight steel, a vacuum melting technology is used to cast an ingot; S2. The cast blank is heated to 1170-1230 DEG C, and after being kept for 1-3 hours, the blank is forged into a slab and air-cooled to room temperature; S3. The air-cooled slab is heated to 1200-1250 DEG C, and after being kept for 2-4 hours, the slab is hot-rolled and air-cooled to room temperature to obtain a hot-rolled plate; S4. The hot-rolled plate is cold-rolled at room temperature to obtain a cold-rolled plate; S5. The cold-rolled plate is heated to 400-650 DEG C, kept for 15-30 minutes, and then aged, and then water-quenched to room temperature to obtain the short-process high-strength high-manganese high-aluminum austenitic lightweight steel; The chemical composition of the lightweight steel comprises, by mass percent, C 0.6-1.2%, Mn 18-24%, Al 5.1-8.1%, and the balance of Fe and inevitable impurities; The high-strength austenitic lightweight steel prepared has a recrystallized grain size less than 2 μm and a recrystallization ratio less than 15% after aging.

2. A method of producing a short process high strength high manganese high aluminum austenitic light weight steel according to claim 1, characterized in that, In S3, the total reduction in the hot-rolling process is 80-95%, and the thickness of the hot-rolled plate is 4.0-5.0 mm.

3. The method according to claim 1, wherein the short process high-strength high-manganese high-aluminum austenitic light steel is characterized by, In S4, the total reduction in the cold-rolling process is 75-85%, and the thickness of the cold-rolled plate is 0.8-1.2 mm.

4. A short process high strength high manganese high aluminum austenitic light weight steel produced by the method of claim 1 or 2, characterized by, The lightweight steel has a tensile strength of 1600-1800 MPa, a yield strength of 1430-1800 MPa, and an elongation of 8-15%. The lightweight steel is composed of austenitic structure and κ carbide.

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