Fe-mn-al-c-si austenitic twip high-strength steel and preparation method thereof

Abstract

The application provides a Fe-Mn-Al-C-Si austenitic TWIP high-strength steel and a preparation method thereof, and belongs to the technical field of alloy materials.The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by the application contains, by mass percentage, Si 0.6-0.9%, C 0.9-1.0%, Al 2.5-3%, Mn 20-24% and the balance of Fe.The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by the application has a density of 7.05-7.10 g / cm 3 , a yield strength of 493.09-1289.20 MPa, a tensile strength of 998.10-1442.29 MPa and an elongation of 30.78-79.00%, and has high yield strength, high tensile strength, high elongation and low density.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, and in particular to a Fe-Mn-Al-C-Si austenitic TWIP high-strength steel and its preparation method. Background Technology

[0002] Steel, as the most widely used alloy material, occupies an important position in various industries, and TWIP steel represents another major breakthrough in the comprehensive performance of steel in terms of strength and elongation.

[0003] In recent years, many researchers have conducted in-depth studies on TWIP steel and successfully applied it in a range of industries, such as automotive, marine, and metallurgy, with its performance in the automotive industry being particularly outstanding. For TWIP steel to be used in the automotive field, it needs to possess good comprehensive mechanical properties and a low density (<7.2 g / cm³). 3 To meet the requirements of lightweighting. However, the strength of TWIP steel obtained by traditional alloy composition and preparation methods in the existing technology is mostly concentrated at around 400MPa. Although the yield strength of TWIP steel can be improved by controlling the preparation method, the plasticity of the material is often sacrificed, resulting in a low elongation.

[0004] Therefore, providing a TWIP high-strength steel with high yield strength, high tensile strength, high elongation and low density has become an urgent technical problem to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a Fe-Mn-Al-C-Si austenitic TWIP high-strength steel. The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention possesses high yield strength, high tensile strength, high elongation, and low density.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides an austenitic TWIP high-strength steel based on the Fe-Mn-Al-C-Si system, comprising, by mass percentage: Si 0.6-0.9%, C 0.9-1.0%, Al 2.5-3%, Mn 20-24%, and the balance Fe.

[0008] Preferably, the microstructure of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel comprises: recrystallized austenitic grains and / or non-recrystallized austenitic grains;

[0009] The grain size of the recrystallized austenite is 5–9 μm;

[0010] The grain size of the non-recrystallized austenite is 40–50 μm.

[0011] This invention provides a method for preparing Fe-Mn-Al-C-Si austenitic TWIP high-strength steel as described above, comprising the following steps:

[0012] (a) The alloy raw materials are melted and then cast to obtain an ingot;

[0013] (b) The ingot obtained in step (a) is homogenized to obtain a homogenized alloy steel ingot;

[0014] (c) The homogenized alloy steel ingot obtained in step (b) is subjected to hot rolling and cold rolling in sequence to obtain rolled alloy steel plate;

[0015] (d) The rolled alloy steel sheet obtained in step (c) is annealed to obtain Fe-Mn-Al-C-Si austenitic TWIP high-strength steel.

[0016] Preferably, the homogenization temperature in step (b) is 1100–1200°C, and the homogenization time is 60–120 min.

[0017] Preferably, the temperature of the hot rolling treatment in step (c) is 900–1000°C.

[0018] Preferably, the hot rolling process is a multi-pass hot rolling deformation; the reduction amount in each pass of the multi-pass hot rolling deformation is ≤20%.

[0019] Preferably, the total deformation of the hot rolling process is 80-88%.

[0020] Preferably, the cold rolling process in step (c) is a multi-pass rolling deformation; the reduction in each pass of the multi-pass rolling deformation is ≤3%.

[0021] Preferably, the total deformation of the cold rolling process is 35-45%.

[0022] Preferably, the annealing temperature in step (d) is 550–850°C, and the holding time for annealing is 15–25 min.

[0023] This invention provides an austenitic TWIP high-strength steel based on the Fe-Mn-Al-C-Si system, comprising, by mass percentage: Si 0.6-0.9%, C 0.9-1.0%, Al 2.5-3%, Mn 20-24%, and the balance Fe. The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention, by adding Mn, can expand the austenite phase region, increase the stability of austenite, and ensure its stable existence at room temperature. Mn also has a solid solution strengthening effect. The addition of Al can significantly reduce the density of the steel. Furthermore, Al causes outward expansion of the crystal lattice, increasing the volume of the lightweight steel and further reducing the density. Al can also control stacking fault energy and ensure the excitation of dislocation slip and twinning at low stacking fault energies. Si can dissolve in austenite, playing a solid solution strengthening role, improving the strength and hardness of the steel, while reducing the stacking fault energy. The addition of C can improve the stability of austenite in the steel and the recovery kinetics of austenite, expand the austenite phase region, and has an interstitial solid solution strengthening effect, improving strength and toughness. Additionally, C can also reduce the density of the high-strength steel. The results of the examples show that the density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention is 7.05–7.10 g / cm³. 3 It has a yield strength of 493.09–1289.20 MPa, a tensile strength of 998.10–1442.29 MPa, and an elongation of 30.78–79.00%, exhibiting high yield strength, high tensile strength, high elongation, and low density. Attached Figure Description

[0024] Figure 1 This is the electron backscattering diffraction pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 1 of the present invention;

[0025] Figure 2 This is the electron backscattering diffraction pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 2 of the present invention;

[0026] Figure 3 This is the electron backscattering diffraction pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 3 of the present invention;

[0027] Figure 4 The images show TEM images of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 3 of this invention; where (a) shows dense dislocation tangles; and (b) shows stacking faults and twins.

[0028] Figure 5 This is a schematic diagram of the dimensions of the tensile specimen in the test example of the present invention; the unit of dimension is mm. Detailed Implementation

[0029] This invention provides an austenitic TWIP high-strength steel based on the Fe-Mn-Al-C-Si system, comprising, by mass percentage: Si 0.6-0.9%, C 0.9-1.0%, Al 2.5-3%, Mn 20-24%, and the balance Fe.

[0030] The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention, by mass percentage, comprises 0.6-0.9% Si, preferably 0.7-0.8%, and more preferably 0.75%. In this invention, Si can be dissolved in austenite in the TWIP steel, playing a role in solid solution strengthening and reducing stacking fault energy. Limiting the Si content to the above-mentioned range in this invention can improve the strength of the steel.

[0031] The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention, by mass percentage, comprises 0.9-1.0% C, preferably 0.95-1.0%, and more preferably 0.95%. In this invention, C can improve the stability and recovery kinetics of austenite in the steel, expand the austenite phase region, and has interstitial solid solution strengthening effect, improving strength and toughness, while also reducing density. Limiting the C content to the above-mentioned range in this invention reduces the density of the steel while maintaining its strength and plasticity.

[0032] The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention, by mass percentage, comprises 2.5-3% Al, preferably 2.6-2.8%, and more preferably 2.7%. In this invention, the addition of Al significantly reduces the density of the steel. The addition of Al causes outward expansion of the crystal lattice, increasing the volume of the steel and further reducing its density. By limiting the Al content to the above-mentioned range, this invention can control the stacking fault energy and ensure the activation of dislocation slip and twinning at low stacking fault energies, thereby improving the strength and toughness of the steel and reducing its density.

[0033] The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention, by mass percentage, comprises 20-24% Mn, preferably 21-23%, and more preferably 22%. In this invention, Mn can expand the austenite phase region, thereby increasing the stability of austenite and ensuring its stable existence at room temperature. Furthermore, Mn also possesses solid solution strengthening properties. Limiting the Mn content to the above-mentioned range in this invention can improve the strength of the steel.

[0034] In this invention, the microstructure of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel preferably includes recrystallized austenite grains and / or non-recrystallized austenite grains, more preferably recrystallized austenite grains and non-recrystallized austenite grains.

[0035] In this invention, the grain size of the recrystallized austenite is preferably 5–9 μm. Limiting the grain size of the recrystallized austenite to this range ensures the strength and toughness of the steel.

[0036] In this invention, the grain size of the non-recrystallized austenite is 40–50 μm. Limiting the grain size of the non-recrystallized austenite to this range further improves the strength of the steel without significantly sacrificing toughness.

[0037] This invention expands the austenite phase region by adding Mn, increasing the stability of austenite and ensuring its stable existence at room temperature. Mn also provides solid solution strengthening. Adding Al significantly reduces the density of the steel. Furthermore, Al causes outward expansion of the crystal lattice, increasing the volume of the lightweight steel and further reducing density. Al also controls stacking fault energy and ensures the excitation of dislocation slip and twinning at low stacking fault energies. Si dissolves in austenite, providing solid solution strengthening, increasing the strength and hardness of the steel, while reducing stacking fault energy. Adding C improves the stability of austenite and its recovery kinetics, expands the austenite phase region, provides interstitial solid solution strengthening, and enhances strength and toughness. Additionally, C can reduce the density of high-strength steel.

[0038] This invention also provides a method for preparing the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel described in the above technical solution, comprising the following steps:

[0039] (a) The alloy raw materials are melted and then cast to obtain an ingot;

[0040] (b) The ingot obtained in step (a) is homogenized to obtain a homogenized alloy steel ingot;

[0041] (c) The homogenized alloy steel ingot obtained in step (b) is subjected to hot rolling and cold rolling in sequence to obtain rolled alloy steel plate;

[0042] (d) Anneal the rolled alloy steel sheet obtained in step (c) to obtain Fe-Mn-Al-C-Si austenitic TWIP high-strength steel.

[0043] This invention involves melting alloy raw materials and then casting them to obtain ingots.

[0044] In this invention, the alloy raw materials preferably include high-purity iron rods (Fe 99.99%), electrolytic manganese sheets (Mn 99.99%), high-purity aluminum rods (Al 99.99%), high-purity silicon (Si 99.99%), and high-purity carbon (C 99.99%). Limiting the alloy raw materials to the above-mentioned types and purities avoids introducing excessive impurities into the alloy.

[0045] In this invention, the alloy raw materials are preferably pretreated before smelting.

[0046] In this invention, the pretreatment preferably includes washing and drying.

[0047] In this invention, the cleaning is preferably ultrasonic cleaning; the cleaning time is preferably 25-35 minutes, more preferably 30 minutes; the solvent used for cleaning is preferably anhydrous ethanol. This invention does not have a specific limitation on the ultrasonic frequency for ultrasonic cleaning; parameters commonly used by those skilled in the art can be employed to clean the alloy raw materials effectively.

[0048] In this invention, the drying process is preferably air drying.

[0049] In this invention, the melting is preferably carried out in a vacuum induction furnace. This invention does not impose any special limitations on the vacuum control in the vacuum induction furnace; appropriate selection can be made using conventional methods employed by those skilled in the art.

[0050] In this invention, the preferred order of adding alloy raw materials during the smelting process is as follows: first, high-purity iron rods and electrolytic manganese sheets are added to the crucible and melted, followed by the addition of high-purity silicon, high-purity carbon, and high-purity aluminum rods for further melting. By limiting the smelting of alloy raw materials to the above-mentioned order, this invention avoids the loss of silicon, carbon, and aluminum during the smelting process and precisely controls the alloy composition content.

[0051] The present invention does not impose any special limitations on the casting operation; any casting method known to those skilled in the art can be used.

[0052] After obtaining the ingot, the present invention performs homogenization treatment on the ingot to obtain homogenized alloy steel ingot.

[0053] In this invention, the homogenization treatment temperature is preferably 1100–1200°C, more preferably 1150°C; the homogenization treatment time is preferably 60–120 min, more preferably 80–120 min, and even more preferably 100–120 min. Limiting the homogenization treatment time and temperature to the above ranges ensures the uniformity of the alloy composition.

[0054] In this invention, the heating rate to the homogenization treatment temperature is preferably 5–20 °C / min, more preferably 10 °C / min. In this invention, variations in the heating rate affect grain size and phase structure; a slow heating rate increases grain growth time, resulting in larger grain sizes. By limiting the heating rate to the homogenization treatment temperature within the aforementioned range, this invention achieves grains of suitable size.

[0055] In this invention, the cooling method for the homogenization process is preferably air cooling.

[0056] After obtaining the homogenized alloy steel ingot, the present invention performs hot rolling and cold rolling treatments on the homogenized alloy steel ingot in sequence to obtain rolled alloy steel plate.

[0057] In this invention, the temperature of the hot rolling treatment is preferably 900–1000°C, more preferably 900–950°C. Limiting the hot rolling temperature to this range allows for better hot rolling of the alloy.

[0058] In this invention, the heating rate to the hot rolling temperature is preferably 8–12 °C / min, more preferably 10 °C / min. In this invention, an excessively fast or slow heating rate can lead to deviations in grain size. Limiting the heating rate to the hot rolling temperature within the above-mentioned range ensures uniform grain size.

[0059] In this invention, the hot rolling process is preferably a multi-pass hot rolling deformation; the amount of pressure applied in each pass of the multi-pass hot rolling deformation is preferably ≤20%, more preferably ≤15%. By limiting the amount of pressure applied in each pass to the above range, this invention can prevent the workpiece from cracking due to excessive pressure during the deformation process.

[0060] In the hot rolling process, the present invention preferably ensures that the rolling temperature is the same for each pass of the hot rolling process.

[0061] In this invention, the total deformation of the hot rolling process is preferably 80-88%, more preferably 80-85%. Limiting the total deformation of the hot rolling process to the above range can better improve the mechanical properties of the alloy.

[0062] After hot rolling, the hot-rolled alloy steel plate is preferably water-quenched to room temperature.

[0063] In this invention, the cold rolling process is preferably carried out in a twin-roll mill; the temperature of the cold rolling process is preferably room temperature; the cold rolling process is preferably a multi-pass rolling deformation; the reduction per pass in the multi-pass rolling deformation is preferably ≤3%, more preferably ≤2%. By limiting the reduction per pass to the above range, this invention can prevent the workpiece from cracking due to excessive reduction during deformation.

[0064] In this invention, the total deformation of the cold rolling process is preferably 35-45%, more preferably 40%. Limiting the total deformation of the cold rolling process to the above range can prevent cracking during the rolling process and give the alloy good mechanical properties.

[0065] After obtaining the rolled alloy steel sheet, the present invention performs annealing treatment on the rolled alloy steel sheet to obtain Fe-Mn-Al-C-Si system austenitic TWIP high-strength steel.

[0066] In this invention, the annealing temperature is preferably 550–850°C, more preferably 550–750°C, and even more preferably 550–650°C; the holding time for the annealing is preferably 15–25 min, more preferably 20 min. Limiting the annealing temperature and time to the above ranges ensures that the alloy possesses good strength and toughness.

[0067] This invention enables the alloy to have a smaller grain size by homogenizing, hot rolling, and cold rolling, and eliminates substructures and defects through annealing, thereby giving the alloy high strength while maintaining good elongation.

[0068] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0069] Example 1

[0070] A Fe-Mn-Al-C-Si austenitic TWIP high-strength steel, by mass percentage, has the following composition: Si 0.75%, C 0.95%, Al 2.7%, Mn 22%, and the balance Fe;

[0071] The preparation method of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel consists of the following steps:

[0072] (a) The alloy raw materials were ultrasonically cleaned in wastewater ethanol for 30 minutes. High-purity iron rods (Fe 99.99%) and electrolytic manganese sheets (Mn 99.99%) were first placed in a magnesia crucible in a vacuum induction furnace. Then, high-purity silicon (Si 99.99%), high-purity carbon (C 99.99%), and high-purity aluminum rods (Al) were added. 99.99% of the high-purity iron rod and electrolytic manganese sheet were placed in the secondary feeding hopper of the vacuum induction furnace. The vacuum induction furnace was evacuated to a vacuum degree of 0.02 MPa, and then high-purity argon gas was introduced into the vacuum induction furnace to a vacuum degree of 0.03 MPa. First, the power of the vacuum induction furnace was set to 5 kW and the heating time was 6 min. Then, the power of the vacuum induction furnace was set to 10 kW and the heating time was 6 min. Then, the power of the vacuum induction furnace was set to 20 kW and the heating time was 12 min. After the high-purity iron rod and electrolytic manganese sheet were melted, the alloy raw material in the secondary feeding hopper was poured into the magnesia crucible. The power of the vacuum induction furnace was set to 40 kW and the heating time was 30 min to obtain molten steel. Then, the molten steel was poured into the mold and allowed to cool naturally to room temperature to obtain the ingot.

[0073] (b) The ingot obtained in step (a) is placed in a muffle furnace and heated to 1150°C at a heating rate of 10°C / min. After holding at that temperature for 120 min, the furnace is cooled to room temperature by air cooling to obtain a homogenized alloy steel ingot.

[0074] (c) Cut the homogenized alloy steel ingot obtained in step (b) into steel blocks of 40mm×25mm×25mm. Then, put the steel blocks into a muffle furnace and heat them to 900℃ at a heating rate of 10℃ / min. After holding at this temperature for 60min, quickly remove the steel blocks for the first hot rolling. After the first hot rolling, put the steel blocks into the muffle furnace and reheat them to 900℃ and hold them for 3min for the second hot rolling. The number of hot rolling cycles is 8, and the reduction amount per pass is 10% (2.5mm). A hot-rolled steel plate with a thickness of 5mm is obtained. The total deformation amount of the hot rolling treatment is 80%. After the hot rolling is completed, the steel plate is water quenched and taken out after cooling to room temperature to obtain a hot-rolled alloy steel plate. At room temperature, the hot-rolled alloy steel plate is cold-rolled in a twin-roll mill with a reduction amount of 2% (0.1mm) per pass and a reduction number of passes of 20 to obtain a cold-rolled alloy steel plate with a thickness of 3mm. The total deformation amount of the cold rolling treatment is 40%. A rolled alloy steel plate is obtained.

[0075] (d) The rolled alloy steel plate obtained in step (c) is placed in a muffle furnace and held at 850°C for 20 min to obtain Fe-Mn-Al-C-Si austenitic TWIP high-strength steel.

[0076] The electron backscattering pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel prepared in Example 1 is shown below. Figure 1 As shown, by Figure 1It can be seen that the obtained Fe-Mn-Al-C-Si austenitic TWIP high-strength steel is composed of fully recrystallized austenitic grains.

[0077] The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 1 was tested using the Archimedes' displacement method and a digital density meter (XF-120SD). The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel was 7.07 g / cm³. 3 .

[0078] Example 2

[0079] The only difference between Example 2 and Example 1 is that the annealing temperature in step (d) is 650°C, and the rest is the same as in Example 1.

[0080] The electron backscattering pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel prepared in Example 2 is shown below. Figure 2 As shown, by Figure 2 It can be seen that the obtained Fe-Mn-Al-C-Si system TWIP high-strength steel is composed of recrystallized austenite grains and unrecrystallized austenite grains.

[0081] The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 2 was tested using the Archimedes' displacement method and a digital density meter (XF-120SD). The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel was 7.05 g / cm³. 3 .

[0082] Example 3

[0083] The only difference between Example 3 and Example 1 is that the annealing temperature in step (d) is 550°C, and the rest is the same as in Example 1.

[0084] The electron backscattering pattern of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel prepared in Example 3 is shown in Figure 3. Figure 3 As shown, by Figure 3 It can be seen that the obtained Fe-Mn-Al-C-Si system TWIP high-strength steel is composed of unrecrystallized austenite grains.

[0085] TEM image of the austenite in the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel prepared in Example 3 is shown below. Figure 4 As shown, by Figure 4 It can be seen that (a) represents dense dislocation entanglement, and (b) represents stacking faults and twins.

[0086] The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 3 was tested using the Archimedes' displacement method and a digital density meter (XF-120SD). The density of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel was 7.07 g / cm³. 3 .

[0087] Test case

[0088] Tensile specimens were prepared from the Fe-Mn-Al-C-Si austenitic TWIP high-strength steels in Examples 1-3 using wire electrical discharge machining. The tensile specimens are shown in the figure below. Figure 5 As shown, the sample was polished on #150 to #400 gauze paper to remove the oxide layer on the surface, and a uniaxial tensile test was performed on an Instron 5982 universal testing machine. The mechanical properties obtained are shown in Table 1.

[0089] Table 1 Mechanical properties of Fe-Mn-Al-C-Si austenitic TWIP high-strength steels in Examples 1-3

[0090]

[0091]

[0092] This invention employs an annealing process to control the microstructure of the alloy, resulting in different morphological structures at different annealing temperatures. The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 2 exhibits a dual-state structure (i.e., recrystallized austenite grains and non-recrystallized austenite grains), such as... Figure 2 As shown in the electron backscattering diagram (EBSD), the dual-state microstructure allows the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel to possess both high strength and good elongation. The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel in Example 3 exhibits non-recrystallized austenitic grains, such as... Figure 3 As shown, it contains a high density of dislocations. The high density of dislocations provides extremely high dislocation strengthening in the alloy, giving TWIP high-strength steel extremely high strength.

[0093] As shown in Table 1, the test results and density test results indicate that the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel provided by this invention has a yield strength of 493.09–1289.20 MPa, a tensile strength of 998.10–1442.29 MPa, an elongation of 30.78–79.00%, and a density of 7.05–7.10 g / cm³. 3 It has high yield strength, high tensile strength, high elongation and low density.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A Fe-Mn-Al-C-Si austenitic TWIP high-strength steel, comprising, by mass percentage: Si 0.75%, C 0.95%, Al 2.7%, Mn 22% and the balance Fe; The preparation method of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel consists of the following steps: (a) The alloy raw materials were ultrasonically cleaned in anhydrous ethanol for 30 min. High-purity iron rods (Fe 99.99%) and electrolytic manganese sheets (Mn 99.99%) were first placed in a magnesia crucible in a vacuum induction furnace. Then, high-purity silicon (Si 99.99%), high-purity carbon (C 99.99%), and high-purity Al... 99.99% high-purity aluminum rods are placed in the secondary feeding hopper of a vacuum induction furnace. The vacuum induction furnace is evacuated to a vacuum level of 0.02 MPa, and then high-purity argon gas is introduced into the vacuum induction furnace to a vacuum level of 0.03 MPa. First, the power of the vacuum induction furnace is set to 5 kW and the heating time is 6 min. Then, the power of the vacuum induction furnace is set to 10 kW and the heating time is 6 min. Then, the power of the vacuum induction furnace is set to 20 kW and the heating time is 12 min. After the high-purity iron rods and electrolytic manganese sheets are melted, the alloy raw materials in the secondary feeding hopper are poured into a magnesia crucible. The power of the vacuum induction furnace is set to 40 kW and the heating time is 30 min to obtain molten steel. Then, the molten steel is poured into a mold and allowed to cool naturally to room temperature to obtain an ingot. (b) The ingot obtained in step (a) is placed in a muffle furnace and heated to 1150°C at a heating rate of 10°C / min. After holding at that temperature for 120 min, the furnace is cooled to room temperature by air cooling to obtain a homogenized alloy steel ingot. (c) Cut the homogenized alloy steel ingot obtained in step (b) into steel blocks of 40mm×25mm×25mm. Then, put the steel blocks into a muffle furnace and heat them to 900℃ at a heating rate of 10℃ / min. After holding at that temperature for 60min, quickly remove the steel blocks for the first hot rolling. After the first hot rolling is completed, put the steel blocks into the muffle furnace and reheat them to 900℃ and hold them for 3min for the second hot rolling. The number of hot rolling cycles is 8, and the reduction amount per pass is 2.5mm, to obtain a hot-rolled steel plate with a thickness of 5mm. The total deformation amount of the hot rolling process is 80%. After the hot rolling is completed, the steel plate is water quenched and taken out after cooling to room temperature to obtain a hot-rolled alloy steel plate. At room temperature, the hot-rolled alloy steel plate is cold-rolled in a twin-roll mill with a reduction amount of 0.1mm per pass and a reduction number of 20 times to obtain a cold-rolled alloy steel plate with a thickness of 3mm. The total deformation amount of the cold rolling process is 40%, to obtain a rolled alloy steel plate. (d) The rolled alloy steel plate obtained in step (c) is placed in a muffle furnace and held at 550°C for 20 min to obtain Fe-Mn-Al-C-Si austenitic TWIP high-strength steel; The microstructure of the Fe-Mn-Al-C-Si austenitic TWIP high-strength steel consists of unrecrystallized austenitic grains.

2. The Fe-Mn-Al-C-Si austenitic TWIP high-strength steel according to claim 1, characterized in that, The grain size of the non-recrystallized austenite is 40~50μm.

3. The method for preparing Fe-Mn-Al-C-Si austenitic TWIP high-strength steel according to claim 1 or 2 comprises the following steps: (a) The alloy raw materials were ultrasonically cleaned in anhydrous ethanol for 30 min. High-purity iron rods (Fe 99.99%) and electrolytic manganese sheets (Mn 99.99%) were first placed in a magnesia crucible in a vacuum induction furnace. Then, high-purity silicon (Si 99.99%), high-purity carbon (C 99.99%), and high-purity Al... 99.99% high-purity aluminum rods are placed in the secondary feeding hopper of a vacuum induction furnace. The vacuum induction furnace is evacuated to a vacuum level of 0.02 MPa, and then high-purity argon gas is introduced into the vacuum induction furnace to a vacuum level of 0.03 MPa. First, the power of the vacuum induction furnace is set to 5 kW and the heating time is 6 min. Then, the power of the vacuum induction furnace is set to 10 kW and the heating time is 6 min. Then, the power of the vacuum induction furnace is set to 20 kW and the heating time is 12 min. After the high-purity iron rods and electrolytic manganese sheets are melted, the alloy raw materials in the secondary feeding hopper are poured into a magnesia crucible. The power of the vacuum induction furnace is set to 40 kW and the heating time is 30 min to obtain molten steel. Then, the molten steel is poured into a mold and allowed to cool naturally to room temperature to obtain an ingot. (b) The ingot obtained in step (a) is placed in a muffle furnace and heated to 1150°C at a heating rate of 10°C / min. After holding at that temperature for 120 min, the furnace is cooled to room temperature by air cooling to obtain a homogenized alloy steel ingot. (c) Cut the homogenized alloy steel ingot obtained in step (b) into steel blocks of 40mm×25mm×25mm. Then, put the steel blocks into a muffle furnace and heat them to 900℃ at a heating rate of 10℃ / min. After holding at that temperature for 60min, quickly remove the steel blocks for the first hot rolling. After the first hot rolling is completed, put the steel blocks into the muffle furnace and reheat them to 900℃ and hold them for 3min for the second hot rolling. The number of hot rolling cycles is 8, and the reduction amount per pass is 2.5mm, to obtain a hot-rolled steel plate with a thickness of 5mm. The total deformation amount of the hot rolling process is 80%. After the hot rolling is completed, the steel plate is water quenched and taken out after cooling to room temperature to obtain a hot-rolled alloy steel plate. At room temperature, the hot-rolled alloy steel plate is cold-rolled in a twin-roll mill with a reduction amount of 0.1mm per pass and a reduction number of 20 times to obtain a cold-rolled alloy steel plate with a thickness of 3mm. The total deformation amount of the cold rolling process is 40%, to obtain a rolled alloy steel plate. (d) The rolled alloy steel plate obtained in step (c) is placed in a muffle furnace and held at 550°C for 20 min to obtain Fe-Mn-Al-C-Si austenitic TWIP high-strength steel.

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