A copper-containing heterogeneous structure austenitic light-weight steel, and a preparation method and application thereof

Abstract

The application discloses a kind of copper-containing heterogeneous structure austenitic light steel and its preparation method and application, belong to metal material processing technical field.The application is designed by copper alloying component, in combination with homogenization treatment, large deformation cold rolling, using the precipitation strengthening, solid solution strengthening and recrystallization inhibition effect of copper element, match 730~750 ℃, 1~3 min accurate annealing process, build stable heterogeneous structure by recrystallization soft area and non-recrystallization hard area in steel material.The application effectively solves the defects that the plasticity of traditional Fe-Mn-Al-C light steel precipitates strengthening causes sudden drop, brittle, difficult to form ideal heterogeneous structure, realizes the synchronous promotion of steel yield strength, tensile strength and elongation, and the obtained light steel is low in density, and excellent in comprehensive mechanical property, can be widely applied in the field of lightweight structural parts such as automobile body, and the preparation process is simple and easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of metal materials and heat treatment technology, specifically relating to a copper-containing heterostructure austenitic lightweight steel, its preparation method, and its application. Background Technology

[0002] With the global energy shortage and air pollution problems becoming increasingly severe, the demand for lightweight structural materials in the automotive, aerospace, and other fields continues to rise. Lightweight materials can effectively reduce vehicle weight, improve fuel efficiency, and reduce carbon emissions, making it one of the core directions in the research and development of modern transportation equipment. Traditional structural steel has excellent strength and stiffness, but its high density results in poor lightweighting effects; therefore, new lightweight steels with low density, high strength, and high plasticity have become a research hotspot in the industry.

[0003] Fe-Mn-Al-C austenitic lightweight steel, with its low density, high specific strength, and excellent deformability, has become a preferred material for lightweight automotive bodies. This steel relies on high manganese and aluminum content to reduce its overall density, and its face-centered cubic austenitic crystal structure also endows the material with good plasticity and toughness. Currently, the industry mainly improves the yield strength of this type of steel through precipitation strengthening methods using B2 phase and κ carbides. While this can significantly increase strength, the coarse precipitates within the grains cause stress concentration, drastically reducing the steel's plasticity and leading to brittle fracture, severely limiting its use in high-load, impact-resistant structural components.

[0004] Meanwhile, Fe-Mn-Al-C lightweight steel has a low activation energy for hot deformation, making it prone to complete recrystallization during heat treatment, resulting in a homogeneous microstructure. Heterogeneous structures are an effective means of balancing material strength and plasticity, relying on the synergistic effect of hard and soft regions to improve overall performance. However, existing conventional heat treatment processes cannot construct stable recrystallized / non-recrystallized composite heterogeneous structures in this type of steel. Heterogeneous structure forming is difficult, and the performance improvement effect is limited. In summary, existing Fe-Mn-Al-C lightweight steel faces three major technical challenges: the inability to balance strength and plasticity, the tendency for precipitation strengthening to lead to brittleness, and the difficulty in constructing stable heterogeneous structures. There is an urgent need to develop new alloy systems and preparation processes to achieve a comprehensive upgrade of the overall performance of lightweight steel. Summary of the Invention

[0005] This invention addresses the technical shortcomings of existing Fe-Mn-Al-C austenitic lightweight steels, such as precipitation strengthening leading to decreased plasticity, prominent brittleness, and difficulty in forming stable heterogeneous structures. It provides a copper-containing heterogeneous austenitic lightweight steel and its preparation method. By introducing copper for alloying modification and combining it with a precisely controlled high-temperature short-time annealing process, the recrystallization behavior of the steel is suppressed, and the morphology and distribution of precipitated phases are regulated. This constructs a soft-hard composite heterogeneous microstructure, significantly improving the steel's strength while retaining or even enhancing its plasticity and toughness, thus completely solving the problem of the inversion of strength and plasticity in traditional lightweight steels.

[0006] The first aspect of the present invention provides a copper-containing heterostructure austenitic lightweight steel, the chemical composition of which, by weight percentage, is as follows: Mn: 26~30%, Al: 6~10%, C: 1~1.5%, Cu: 3~4%, The balance is Fe.

[0007] In the copper-containing heterostructure austenitic lightweight steel of this invention, manganese acts as an austenite stabilizing element, ensuring a single austenitic structure at room temperature and achieving solid solution strengthening. Aluminum reduces the overall density of the steel while promoting the precipitation of strengthening phases. Carbon, in conjunction with manganese and aluminum, stabilizes austenite and generates carbides. Copper possesses both precipitation strengthening and solid solution strengthening effects, increasing the austenite volume fraction, inhibiting grain recrystallization, preventing excessive coarsening of precipitated phases, and avoiding brittleness. This compositional system lays the foundation for heterostructure forming and simultaneous improvement of strength and plasticity from the raw material end.

[0008] The heterogeneous structure described in this invention is a composite microstructure in which unrecrystallized structures (hard zones) and recrystallized structures (soft zones) coexist in a Fe-Mn-Al-C austenitic steel matrix, formed after copper alloying and high-temperature short-time annealing processes. Wherein: The hard region (unrecrystallized austenite) retains a large number of dislocations and suffers from severe lattice distortion after cold rolling, resulting in elongated grains, high hardness and yield strength, but weak plastic deformation capacity. The soft region (recrystallized austenite) undergoes static recrystallization during annealing, resulting in fine grains, low internal dislocation density, excellent plasticity and toughness, but relatively lower strength. These two types of regions are randomly or interspersed within the steel, without obvious stratification, forming heterogeneous interfaces through austenite grain boundaries, thus constituting a complete heterogeneous structural system.

[0009] Traditional steel, after conventional heat treatment, mostly exhibits a single recrystallized structure (homogeneous structure). The heterogeneous structure of this invention simultaneously contains two grain states, resulting in a significantly non-uniform microstructure, which is its most obvious characteristic. Different regions within the same material show marked differences in mechanical properties: the non-recrystallized region has higher hardness and strength; the recrystallized region has better plasticity and ductility. These performance differences are determined by the grain state and dislocation density. Numerous heterogeneous interfaces exist between the hard and soft regions. When the material undergoes plastic deformation under external force, heterogeneous deformation-induced stress (HDI stress) is generated at the interfaces, inducing the enrichment of geometrically necessary dislocations, enhancing work hardening capacity, and preventing deformation concentration and early necking fracture. Furthermore, this heterogeneous structure is achieved through a combination of copper element-inhibited recrystallization and precise temperature and time control during high-temperature short-time annealing: the solid solution dragging effect of copper hinders complete grain recrystallization, and short-time annealing only allows partial recrystallization, ultimately forming a hard-soft coexisting structure. If the annealing time is too long or the temperature is too high, the structure will completely recrystallize, and the heterogeneous structure will disappear. The non-recrystallized hard zone bears the main load, ensuring the steel's high yield strength and tensile strength; the recrystallized soft zone coordinates overall plastic deformation, absorbs strain, and delays crack initiation, solving the defect of "increased strength but sharp drop in plasticity" in traditional precipitation-strengthened steel. During material deformation, the deformation rates of the soft and hard zones are inconsistent, generating a stress gradient and additional work hardening effect at the heterogeneous interface, significantly improving the steel's overall deformation capacity and impact resistance, making it suitable for dynamic load conditions such as automotive bodies. Compared to traditional homogeneous steels strengthened by B2 phase and κ carbides, this heterogeneous structure does not rely on coarse precipitates as the main strengthening phase, but instead uses nano-precipitation strengthening of copper, reducing stress concentration and improving the material's service reliability under high load and impact environments.

[0010] It should be noted that heterogeneous structures are not the same as dual-phase steel, which is a composite of two different crystalline phases (such as austenite and ferrite). The heterogeneous structure of this invention has an austenitic matrix, differing only in the recrystallization state of the grains, thus belonging to heterogeneous structures with different microstructures within the same phase. It should also be noted that heterogeneous structures are not the same as composite materials, which are combinations of two independent materials. This structure, however, has a single alloy steel matrix with differentiated internal microstructures, exhibiting a homogeneous overall chemical composition, but with a non-homogeneous microstructure.

[0011] According to some embodiments of the present invention, the chemical composition, by weight percentage, is as follows: Mn: 28~30%, Al: 8.0~9.0%, C: 1.1~1.3%, Cu: 3.0~3.5%, The balance is Fe.

[0012] According to some embodiments of the present invention, the chemical composition, by weight percentage, is as follows: Mn: 29.16%, Al: 8.81%, C: 1.23%, Cu: 3.24%, The balance is Fe.

[0013] As a stabilizing element for core austenite, manganese, when its content is controlled at 28%~30%, can stably obtain a single austenitic structure at room temperature, thereby enhancing the basic strength of the matrix through solid solution strengthening. Furthermore, the content range of this invention is reasonably set, avoiding both excessively low manganese content, which would prevent complete austenite stabilization and lead to harmful phase transformations, and excessively high manganese content, which would increase raw material costs and reduce the processing performance of steel.

[0014] Limiting the aluminum content to 8.0%~9.0% has two advantages: firstly, it significantly reduces the overall density of the steel, achieving the goal of lightweighting and meeting the weight reduction requirements of automobile bodies; secondly, this content range can moderately promote the precipitation of B2 phase and κ carbides, helping to improve the strength of the steel. Aluminum content below 8.0% results in insufficient weight reduction, while content above 9.0% easily leads to excessive precipitation of intermetallic compounds, exacerbating the brittleness of the steel. This range strikes a balance between lightweighting and material toughness.

[0015] A carbon content controlled between 1.1% and 1.3% can synergistically work with manganese and aluminum to further stabilize the austenite structure, while also reasonably inducing carbide formation. This content range ensures the strengthening effect of carbides while avoiding problems such as grain boundary embrittlement and decreased plasticity caused by excessive carbon content, or insufficient strengthening effect caused by insufficient carbon content.

[0016] Setting the copper content to 3.0%~3.5% is one of the core optimization designs of this invention. Within this range, copper can form a dispersed, nano-sized copper-rich precipitate phase, achieving precipitation strengthening and further enhancing the steel's strength. Simultaneously, copper can increase the austenite volume fraction and stacking fault energy, effectively suppressing grain recrystallization during heat treatment, providing a foundation for constructing a heterogeneous structure where soft and hard materials coexist. Furthermore, at this content, copper exists in a solid solution + nano-precipitate form, preventing the formation of coarse copper-rich phases, thus eliminating stress concentration and brittle fracture problems, fundamentally solving the pain point of traditional Fe-Mn-Al-C steel's difficulty in simultaneously achieving both strength and plasticity.

[0017] In summary, the components in the steel of this invention are all set with reasonable fluctuation ranges, which are in line with the component control errors of conventional smelting in the metallurgical industry. There is no need for extremely precise material control during industrial smelting, which reduces production difficulty and manufacturing costs. At the same time, within this component range, the preparation process of this invention can stably form the target heterogeneous structure, with small fluctuations in the mechanical properties of the steel and good product consistency.

[0018] A second aspect of the present invention provides a method for preparing a copper-containing heterostructure austenitic lightweight steel according to the first aspect of the present invention, comprising the following steps: (1) Homogenization treatment: After heating and holding the cast steel billet at a certain temperature, it is then quenched; (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 730℃~750℃ for 1~3min. After annealing, it is quenched to room temperature to obtain the copper-containing heterostructure austenitic light steel. The chemical composition of the cast steel billet meets the requirements of the copper-containing heterostructure austenitic lightweight steel of the first aspect of the present invention.

[0019] The present invention discloses a method for preparing copper-containing heterostructure austenitic lightweight steel, which includes three main processes: homogenization treatment, cold rolling deformation, and annealing and quenching. Among them, a high-temperature short-time annealing process at 730℃~750℃ for 1~3min is used to precisely control the recrystallization ratio, thereby forming a heterostructure consisting of a recrystallized soft region and an unrecrystallized hard region.

[0020] This method has a simple process route, low equipment requirements, and controllable process parameters. It does not require complex special equipment and can be completed on conventional steel processing production lines, making it highly adaptable to industrial applications.

[0021] According to some embodiments of the present invention, in step (1), the heating temperature is 1180℃~1220℃.

[0022] According to some embodiments of the present invention, in step (1), the heating temperature is any value among 1180℃, 1185℃, 1190℃, 1195℃, 1200℃, 1205℃, 1210℃, 1215℃, and 1220℃, such as 1200℃, or any range formed by both, such as 1190℃~1210℃.

[0023] According to some embodiments of the present invention, in step (1), the heating temperature is 1200℃~1220℃.

[0024] According to some embodiments of the present invention, in step (1), the heat preservation time is 1.8h to 2.2h.

[0025] According to some embodiments of the present invention, in step (1), the heat preservation time is any value among 1.8h, 1.9h, 2.0h, 2.1h, and 2.2h, such as 2.0h, or any range formed by both, such as 1.9h to 2.1h.

[0026] According to some embodiments of the present invention, in step (1), the heat preservation time is 2h to 2.2h.

[0027] The homogenization process using temperature and time can eliminate as-cast composition segregation and structural defects.

[0028] According to some embodiments of the present invention, in step (2), the total deformation of the cold rolling is 75% to 85%.

[0029] According to some embodiments of the present invention, in step (2), the total deformation of the cold rolling is any value among 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, and 85%, such as 80%, or any range of two, such as 78% to 82%.

[0030] Large deformation cold rolling of 75% to 85% can introduce a large number of dislocations and lattice distortions, thereby increasing the strain energy of the microstructure.

[0031] According to some embodiments of the present invention, in steps (1) and (3), the quenching method is water quenching.

[0032] The quenching process fixes the final microstructure and ensures stable performance.

[0033] A third aspect of the present invention provides a vehicle body structural component prepared from copper-containing heterostructure austenitic lightweight steel of the first aspect of the present invention.

[0034] The aforementioned copper-containing heterostructure austenitic lightweight steel is used in lightweight structural components for automobile bodies. This material exhibits low density, high strength, high toughness, and strong impact resistance, fully meeting the requirements for weight reduction, collision protection, and safe use in automobile bodies, and has broad application prospects. Attached Figure Description

[0035] Figure 1 This is a backscattered electron diffraction microstructure diagram of the lightweight steel in Comparative Example 1.

[0036] Figure 2 This is the room temperature tensile curve of the light steel in Comparative Example 1.

[0037] Figure 3 This is the room temperature tensile curve of the lightweight steel in Comparative Example 2.

[0038] Figure 4 This is the room temperature tensile curve of the light steel in Comparative Example 3.

[0039] Figure 5 This is a diagram of the heterogeneous microstructure of the lightweight steel in Example 1.

[0040] Figure 6 This is the room temperature tensile curve of the lightweight steel in Example 1.

[0041] Figure 7 This is the room temperature tensile curve of the lightweight steel in Example 2.

[0042] Figure 8 This is the room temperature tensile curve of the lightweight steel in Example 3.

[0043] Figure 9 This is a process flow diagram for the preparation of copper-containing heterostructure austenitic lightweight steel. Detailed Implementation

[0044] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0045] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0046] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0047] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0048] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0049] In the embodiment, the standard for testing the room temperature tensile properties of the steel plate is GB / T228.1-2021 "Metallic materials, tensile testing - Part 1: Room temperature test method".

[0050] Comparative Example 1 A lightweight steel plate was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C-3.24Cu.

[0051] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 700℃ for 1 hour. After annealing, it is water-quenched to room temperature to obtain a lightweight steel plate.

[0052] The lightweight steel plate prepared in this comparative example has the following microstructure: Figure 1 As shown, the steel has undergone complete recrystallization, resulting in a homogeneous austenitic structure with no obvious heterogeneous structure.

[0053] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 2 As shown. Yield strength 772 MPa, tensile strength 1061 MPa, elongation 23%.

[0054] Comparative Example 2 A lightweight steel plate was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C-3.24Cu.

[0055] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 730℃ for 5 minutes. After annealing, it is water-quenched to room temperature to obtain a lightweight steel plate.

[0056] Observations revealed that the lightweight steel sheet prepared in this comparative example had a higher recrystallization ratio and a further decrease in plasticity.

[0057] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 3 As shown. Yield strength 766 MPa, tensile strength 1014 MPa, elongation 19%.

[0058] Comparative Example 3 (Copper-free control group) A lightweight steel plate was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C (excluding Cu).

[0059] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 730℃ for 1 min. After annealing, it is water-quenched to room temperature to obtain a lightweight steel plate.

[0060] Observations revealed that the lightweight steel plate prepared in this comparative example has a traditional precipitation-strengthened structure, exhibiting high strength but extremely poor plasticity and significant brittleness.

[0061] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 4 As shown. Yield strength 1105 MPa, tensile strength 1210 MPa, elongation 6%.

[0062] Example 1 A copper-containing heterostructure austenitic lightweight steel was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C-3.24Cu.

[0063] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 730℃ for 1 min. After annealing, it is water-quenched to room temperature to obtain copper-containing heterostructure austenitic light steel.

[0064] The copper-containing heterostructure austenitic lightweight steel prepared in this embodiment has the following microstructure: Figure 5 As shown, the microstructure exhibits a stable heterogeneous structure, containing recrystallized soft regions and non-recrystallized hard regions, without coarse precipitates.

[0065] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 6 As shown, the yield strength is 1090 MPa, the tensile strength is 1258 MPa, and the elongation is 25%. While maintaining ultra-high strength, the plasticity is much higher than that of the copper-free control group, demonstrating excellent strength-plasticity balance.

[0066] Example 2 A copper-containing heterostructure austenitic lightweight steel was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C-3.24Cu.

[0067] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 740℃ for 1 min. After annealing, it is water-quenched to room temperature to obtain copper-containing heterostructure austenitic light steel.

[0068] Observations revealed that the copper-containing heterostructure austenitic lightweight steel prepared in this embodiment exhibits further improved plasticity, a slight decrease in strength, and balanced overall performance.

[0069] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 7 As shown. Yield strength 957 MPa, tensile strength 1165 MPa, elongation 34%.

[0070] Example 3 A copper-containing heterostructure austenitic lightweight steel was prepared with the following chemical composition: Fe-29.16Mn-8.81Al-1.23C-3.24Cu.

[0071] The preparation method is as follows: (1) Homogenization treatment: The cast steel billet that meets the chemical composition requirements is heated to 1200℃ and held for 2 hours, and then water-quenched. (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled with a cold rolling deformation of 80% to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 750℃ for 1 min. After annealing, it is water-quenched to room temperature to obtain copper-containing heterostructure austenitic light steel.

[0072] Observations revealed that the copper-containing heterostructure austenitic lightweight steel prepared in this embodiment exhibits optimal plasticity while maintaining high strength, making it suitable for structural components with high requirements for ductility.

[0073] The steel plate was subjected to room temperature tensile property testing, and the room temperature tensile curve is shown below. Figure 8 As shown. Yield strength 789 MPa, tensile strength 1081 MPa, elongation 44%.

[0074] Through the above embodiments, it can be understood that the present invention introduces copper element for alloying, which is different from the traditional single precipitation strengthening mode. The solid solution drag effect of copper can effectively inhibit the recrystallization of steel, and the dispersed distribution of nano-sized copper-rich precipitates improves the strength. At the same time, it avoids stress concentration caused by large-sized precipitates, thus solving the problem of steel brittleness from the root.

[0075] refer to Figure 9As shown, the preparation method of copper-containing heterostructure austenitic lightweight steel of the present invention includes three major processes: homogenization treatment, cold rolling deformation, and annealing and quenching. Specifically, a high-temperature short-time annealing process at 730℃~750℃ for 1~3min is used to precisely control the recrystallization ratio, forming a heterostructure consisting of a recrystallized soft region and an unrecrystallized hard region. A stable heterostructure is successfully constructed in Fe-Mn-Al-C lightweight steel. The heterostructure deformation process generates heterostructure deformation-induced stress, enhancing work hardening ability and achieving simultaneous improvement in strength and plasticity, breaking the bottleneck of traditional steel where "strength increases, plasticity decreases". The phase diagram corresponding to this composition can be calculated using Thermo-Calc software, with an optimal annealing temperature of 730°C. The optimal annealing time is 1min; a shorter annealing time limits the precipitation amount and volume fraction of the B2 phase, and prevents excessive growth of recrystallized grains due to a longer annealing time.

[0076] The present invention has a reasonable composition design, a simple preparation process, easy control of process parameters, and uses conventional metallurgical raw materials, resulting in low production costs. It can be directly adapted to existing steel rolling and heat treatment production lines, facilitating large-scale industrial production.

[0077] The lightweight steel obtained by this invention has low density and excellent comprehensive mechanical properties, making it suitable for lightweight structural components such as automobile bodies. It has significant advantages in weight reduction, fuel saving, and improved vehicle safety.

[0078] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A copper-containing heterostructure austenitic lightweight steel, characterized in that, The chemical composition, by weight percentage, is: Mn: 26~30%. Al：6~10%， C：1~1.5%， Cu: 3~4%, The balance is Fe.

2. The copper-containing heterostructure austenitic lightweight steel according to claim 1, characterized in that, The chemical composition, by weight percentage, is as follows: Mn: 28~30%, Al：8.0~9.0%， C：1.1~1.3%， Cu: 3.0~3.5%, The balance is Fe.

3. A method for preparing copper-containing heterostructure austenitic lightweight steel as described in claim 1 or 2, characterized in that, Includes the following steps: (1) Homogenization treatment: After heating and holding the cast steel billet at a certain temperature, it is then quenched; (2) Cold rolling deformation: The steel billet processed in step (1) is cold rolled to obtain a steel plate; (3) Annealing and quenching: The steel plate after cold rolling in step (2) is annealed at 730℃~750℃ for 1~3min. After annealing, it is quenched to room temperature to obtain the copper-containing heterostructure austenitic light steel. The chemical composition of the cast steel billet meets the requirements for copper-containing heterostructure austenitic lightweight steel as described in claim 1 or 2.

4. The method according to claim 3, characterized in that, In step (1), the heating temperature is 1180℃~1220℃.

5. The method according to claim 4, characterized in that, In step (1), the heating temperature is 1200℃~1220℃.

6. The method according to claim 3, characterized in that, In step (1), the heat preservation time is 1.8h to 2.2h.

7. The method according to claim 6, characterized in that, In step (1), the heat preservation time is 2h to 2.2h.

8. The method according to claim 3, characterized in that, In step (2), the total deformation of the cold rolling is 75% to 85%.

9. The method according to any one of claims 3 to 8, characterized in that, In steps (1) and (3), the quenching method is water quenching.

10. A vehicle body structural component, characterized in that, It is prepared from the copper-containing heterostructure austenitic lightweight steel as described in claim 1 or 2.

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