Low-carbon austenite-based high-toughness plastic lightweight steel and preparation method thereof

Abstract

The application discloses a kind of low-carbon austenite-based high-toughness plastic lightweight steel and its preparation method, belong to lightweight steel technical field, solve the problem of low temperature toughness of lightweight steel in prior art.The component of low-carbon austenite-based high-toughness plastic lightweight steel includes:C 0.03%~0.12%, Mn 24.0%~36.0%, Al 4.0%~7.0%, P<0.02%, S<0.01%, Nb 0.04%~1.0%, V 0.04%~1.0%, Mo 0.1%~1.5%, W 0.1%~1.5% by mass percentage;The balance is Fe and inevitable trace impurities.The low-carbon austenite-based high-toughness plastic lightweight steel of the application has good toughness and plasticity at low temperature.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light steel, and particularly relates to a low-carbon austenite-based high-toughness plastic light steel and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for equipment weight reduction, low-density materials have attracted increasing attention. Light steel has advantages such as low cost, high strength and toughness, and is widely concerned. High-carbon austenite Fe-Mn-Al-C light steel has good strength and plasticity, but has obvious brittle-ductile transition phenomenon, and the brittle-ductile transition mechanism is not clear. High-carbon austenite-based dual-phase light steel has similar performance to austenite light steel, and in addition, the deformation incompatibility between the two phases worsens the impact toughness and plasticity.

[0003] CN 114892084 A discloses a high-strength austenite light steel with high impact toughness and a manufacturing method thereof. The chemical composition is as follows in terms of percentage by weight: Mn: 23-26%, Al: 6.90-8.20%, C: 0.83-0.92%, Si: 0.15-0.35, Cr: 0.05-0.14%, Cu: 0.1-0.3%, Nb: 0.01-0.04, N≤0.10%, P<0.008, S<0.002, and the balance is iron and inevitable impurities. It is reported that the KV2 impact energy at -40℃ in the solid solution state is ≥161J, but there is no research on lower temperatures (such as -196℃). CN 115572885 A discloses a manufacturing method of high-strength high-toughness austenite type low-density steel. The chemical composition is as follows in terms of percentage by weight: Mn 23-26%, Al 6.90-8.20%, C 0.83-0.92%, Si 0.10-0.35%, Cr 0.05-0.14%, Cu 0.10-0.30%, Nb 0.01-0.04%, N≤0.10%, P≤0.008%, S≤0.002%, and the balance is iron and inevitable impurities. It is reported that the KV2 impact energy at -40℃ in the solid solution state is ≥177J, but there is no mention of lower temperature toughness. CN 116288021 A discloses a high-strength dual-phase low-density steel, a preparation method and application thereof. The chemical composition is as follows in terms of percentage by weight: C: 0.58-0.62%, Mn: 18-22%, Al: 8-10%, Nb: 0-0.02%, and the balance is Fe and other inevitable impurities. No related impact performance is reported. KR101816439B1 discloses a light high-strength low-carbon steel and a manufacturing method thereof, but there is no research on impact toughness. Therefore, how to improve the low-temperature toughness of light steel becomes a problem to be solved. SUMMARY

[0004] In view of the above, the present application aims to provide a low-carbon austenite-based high-toughness plastic lightweight steel and a preparation method thereof, to solve the problem of low low-temperature toughness of existing lightweight steel.

[0005] The object of the present application is mainly achieved by the following technical solutions:

[0006] In one aspect, the present application provides a low-carbon austenite-based high-toughness plastic lightweight steel, the components of the low-carbon austenite-based high-toughness plastic lightweight steel include, in mass percentage: C 0.03%~0.12%, Mn 24.0%~36.0%, Al 4.0%~7.0%, P<0.02%, S<0.01%, Nb 0.04%~1.0%, V 0.04%~1.0%, Mo 0.1%~1.5%, W 0.1%~1.5%; the balance is Fe and inevitable trace impurities.

[0007] Further, the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel includes an austenite matrix and a small amount of ferrite uniformly distributed on the austenite matrix, without κ-carbide precipitation.

[0008] Further, in the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel, the volume percentage of ferrite is 3%~10%.

[0009] Further, in the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel, the average grain size is 20~37μm.

[0010] Further, the-196℃ KV2 impact energy of the low-carbon austenite-based high-toughness plastic lightweight steel is 243J or more.

[0011] The present application also provides a preparation method of a low-carbon austenite-based high-toughness plastic lightweight steel, which includes: steelmaking, mold casting, heating, forging, cooling, solid solution, and cooling after solid solution.

[0012] Further, the heating process includes: holding the casting blank at 1100~1200℃ for 2~4 hours for homogenization treatment.

[0013] Further, the forging process includes: forging to form different specifications of rod materials at 840~1150℃.

[0014] Further, in the forging process, the open forging temperature is 1050~1150℃, and the finish forging temperature is 840~880℃.

[0015] Further, the solid solution process includes: high-temperature solid solution at 950~1150℃, and the solid solution time is 30min~240min.

[0016] Compared with the prior art, the present application has the following advantages:

[0017] a) The low-carbon austenite-based high-toughness plastic lightweight steel of the present application is designed in composition, adopts low C, high Mn and high Al contents to obtain low-temperature high-toughness austenite, and simultaneously adds Nb, V, Mo and W alloys which have strong combination with C to inhibit κ-carbide precipitation phase, through component control, to ensure that the obtained structure is a combination of low-carbon high-toughness austenite matrix and a small amount of ferrite phase, and to realize the inhibition of κ-carbide precipitation. The low-carbon austenite-based high-toughness plastic lightweight steel of the present application ensures low-temperature stability and strength and toughness.

[0018] b) The deformation structure (i.e. the structure after stretching or impact) of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application at low temperature (for example -196℃) is mainly nanotwin, therefore, the low-carbon austenite-based high-toughness plastic lightweight steel of the present application has good toughness at low temperature.

[0019] c) The low-carbon austenite-based high-toughness plastic lightweight steel of the present application is fully tough fracture at room temperature to -196℃ temperature range, without ductile-brittle transition, the room temperature KV2 impact energy is 290J or more (for example 290-340J), the -196℃ KV2 impact energy is 243J or more (for example 243-265J), the -120℃ KV2 impact energy is 260J or more (for example 261-280J), and can be widely used in low-temperature fields such as low-temperature pressure vessels.

[0020] d) The low-carbon austenite-based high-toughness plastic lightweight steel of the present application has low density (for example 7.08-7.47g / cm 3 , cold speed insensitivity (no κ-carbide precipitation), the room temperature performance of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application is as follows: R t0.5 is 245MPa or more (for example 249-269MPa), Rm is 575MPa or more (for example 579-600MPa), and A is 50% or more (for example 50.1%-53%); the -196℃ performance of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application is as follows: R t0.5 is 560MPa or more (for example 560-570MPa), Rm is 950MPa or more (for example 951-960MPa), and A is 55% or more (for example 55%-70%).

[0021] e) The low-carbon austenite-based high-toughness plastic lightweight steel of the present application has a stacking fault energy of about 23-67mJ / m 2 from -196℃ to room temperature (23℃). Among them, the stacking fault energy at -196℃ is about 2-53mJ / m 2 , which is roughly within the TWIP deformation mechanism, and significantly improves the low-temperature toughness.

[0022] Additional features and advantages of the present application will be set forth in the description that follows, and in part will be apparent from the description, or can be learned by practice of the application. The objectives and other advantages of the present application will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. BRIEF DESCRIPTION OF DRAWINGS

[0023] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0024] Figure 1 is a typical EBSD diffraction quality map of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1;

[0025] Figure 2 is a bright field morphology of undeformed austenite of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1;

[0026] Figure 3 is a deformed twin of austenite at uniformly deformed place of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 after impact at -196°C;

[0027] Figure 4 are macroscopic morphology photos of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 after impact at room temperature and low temperature;

[0028] Figure 5 are force displacement and work displacement curves of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 at room temperature;

[0029] Figure 6 are force displacement and work displacement curves of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 at -80°C;

[0030] Figure 7 are force displacement and work displacement curves of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 at -120°C;

[0031] Figure 8 are force displacement and work displacement curves of the low carbon austenite based high ductility plasticity lightweight steel obtained in Example 1 at -196°C. DETAILED DESCRIPTION

[0032] The preferred embodiments of the present application will be described herein below with reference to the accompanying drawings, in which:

[0033] The application provides a low-carbon austenite-based high-toughness plastic lightweight steel, and components of the low-carbon austenite-based high-toughness plastic lightweight steel include, in percentage by mass, C 0.03%-0.12%, Mn 24.0%-36.0%, Al 4.0%-7.0%, P <0.02%, S <0.01%, Nb 0.04%-1.0%, V 0.04%-1.0%, Mo 0.1%-1.5%, W 0.1%-1.5%, and the balance of Fe and inevitable trace impurities.

[0034] The following specifically describes the effects and dosage selection of the components contained in the application:

[0035] C: C elements can cause the ductile-brittle transition temperature to increase significantly, which is mainly due to the fact that C elements significantly increase the dislocation density and the formation of kelly gas clusters of the material. By means of low-carbon content design, the dislocation density and kelly gas clusters under low-temperature deformation conditions are reduced to some extent, which can effectively improve the deformation under low-temperature conditions and improve the low-temperature toughness. At the same time, the low-carbon design helps to control the austenite stacking fault energy in the range of nano-twin deformation, that is, the austenite stacking fault energy is designed to be 20-50 mJ / m 2 2. In addition, excessive C content can increase the precipitation of κ-carbides in austenite, especially large particles of κ-carbides after welding, which seriously deteriorates the welding performance. In order to avoid the combination of C with Fe, Mn and Al to form (FeMn)3AlC type carbide, the application requires low-carbon control. Therefore, the application limits the C content to 0.03%-0.12%.

[0036] Mn: Mn is an austenite forming and stabilizing element, which can expand the austenite phase region and obtain a certain amount of austenite. However, more than 36% of Mn content leads to the easy formation of β-Mn brittle phase in the lightweight steel, which greatly reduces the toughness of the material. However, in order to ensure that the matrix structure of the steel of the application is austenite structure, the Mn content needs to be not less than 24%. Therefore, the application limits the Mn content to 24%-36%.

[0037] Al: Al is an important element of low density in lightweight steel, which is a key element for determining density and austenite content and can significantly refine the austenite structure. However, Al is a ferrite forming element, and excessive Al addition can reduce the austenite content, and too low Al content has little contribution to density. Therefore, the application limits the Al content to 4%-7%.

[0038] Nb, V, Mo, W: The appropriate addition of Nb, V, Mo and W can greatly reduce the precipitation driving force of κ-carbides and inhibit the precipitation of κ-carbides.

[0039] Specifically, the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel includes an austenite matrix and a small amount of ferrite uniformly distributed on the austenite matrix, and no κ-carbides are precipitated.

[0040] Specifically, in order to guarantee the low-temperature stability and toughness of the base body, the volume percentage of ferrite in the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel is 3% to 10%, and the volume percentage of austenite is more than 89%.

[0041] Specifically, the average grain size of the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel is 20 to 37 μm, and the grain is fine.

[0042] The low-carbon austenite-based high-toughness plastic lightweight steel of the present application is designed in terms of composition, adopts low C, high Mn and high Al content, obtains low-temperature high-toughness austenite, and simultaneously adds Nb, V, Mo and W alloys which are strongly combined with C to inhibit the precipitation of κ-carbide phase. Through component control, it is guaranteed that the obtained structure is a combination of low-carbon high-toughness austenite base body and a small amount of ferrite, and the precipitation of κ-carbide is inhibited. The low-temperature stability and toughness of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application are guaranteed.

[0043] The low-carbon austenite-based high-toughness plastic lightweight steel of the present application is fully ductile fracture in the temperature range from room temperature to -196℃, and there is no ductile-brittle transition. The room temperature KV2 impact energy is more than 290 J (for example, 290 to 340 J); the -196℃ KV2 impact energy is more than 243 J (for example, 243 to 265 J), and the -120℃ KV2 impact energy is more than 260 J (for example, 261 to 280 J), and can be widely used in low-temperature fields such as low-temperature pressure vessels.

[0044] In addition, the low-carbon austenite-based high-toughness plastic lightweight steel of the present application has a low density (for example, 7.08 to 7.47 g / cm 3 ), and is not sensitive to cooling rate (without κ-carbide precipitation). The room temperature performance of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application is as follows: R t0.5 is more than 245 MPa (for example, 249 to 269 MPa), Rm is more than 575 MPa (for example, 579 to 600 MPa), and A is more than 50% (for example, 50.1% to 53%); the -196℃ performance of the low-carbon austenite-based high-toughness plastic lightweight steel of the present application is as follows: R t0.5 is more than 560 MPa (for example, 560 to 570 MPa), Rm is more than 950 MPa (for example, 951 to 960 MPa), and A is more than 55% (for example, 55% to 70%).

[0045] The low-carbon austenite-based high-toughness plastic lightweight steel of the present application has a stacking fault energy of about 23 to 67 mJ / m 2 from -196℃ to room temperature (23℃). The stacking fault energy at -196℃ is about 2 to 53 mJ / m 2 , which is approximately within the TWIP deformation mechanism, which significantly improves the low-temperature toughness.

[0046] As shown in the drawings, the low-carbon austenite-based high-toughness plastic lightweight steel of the present application is mainly composed of nano-twins in the deformed structure (i.e. the structure after stretching or impact) at low temperature (e.g. -196℃), and thus has good toughness at low temperature. Figure 3

[0047] The present application also provides a preparation method of the low-carbon austenite-based high-toughness plastic lightweight steel, which comprises the following steps: steelmaking, mold casting, heating, forging, cooling, solid solution and cooling after solid solution.

[0048] Specifically, the steelmaking and mold casting steps are performed by vacuum induction furnace melting and mold casting into a blank.

[0049] Specifically, the heating step comprises: keeping the blank at 1100-1200℃ for 2-4 hours for homogenization treatment.

[0050] Specifically, the forging step comprises: forging to form different specifications of rods at 840-1150℃.

[0051] Specifically, the cooling step after forging can be performed by conventional water cooling, oil cooling or air cooling.

[0052] Specifically, the solid solution step comprises: high-temperature solid solution at 950-1150℃ for 30-240 minutes to obtain quasi-polygonal ferrite and austenite structure.

[0053] Specifically, the cooling step after solid solution can be performed by water cooling, oil cooling or air cooling.

[0054] It should be noted that the selection of parameters in the preparation method is as follows:

[0055] The parameters of the heating step are selected as follows: the temperature is higher than 1200℃, the grains are abnormally long, and local melting may occur; the temperature is lower than 1100℃, and the elements in the blank cannot be effectively homogenized. Therefore, the heating temperature of the blank is set to 1100-1200℃. In order to ensure that the structure and elements in the blank can be effectively homogenized, the heating time is set to ≥2h, and in order to avoid ineffective long-time heating, the upper limit of the heating time is set to 4h. That is, the heating time is controlled to be 2-4h.

[0056] The forging temperature is selected as follows: if the forging temperature is too high or too low, the structure is unstable. Therefore, the forging temperature is set to 840-1150℃. Specifically, the open forging temperature is 1050-1150℃, and the finish forging temperature is 840-880℃.

[0057] ​Forging cooling process selection: The microstructure and performance of the present application design is not sensitive to the cooling rate, that is, no κ-carbide precipitation, so the cooling process can use conventional water cooling, oil cooling or air cooling.

[0058] Solution process: The solution temperature is lower than 950℃, which cannot effectively eliminate the deformation incompatibility between two phases, and is easy to precipitate large particle MC carbide, which seriously reduces the low temperature toughness of the material; the temperature is higher than 1150℃, which causes abnormal grain growth and significantly reduces the austenite content, which is not conducive to the strength and toughness matching of the material; therefore, high temperature solution is controlled at 950-1150℃. In order to ensure that the microstructure and elements in the steel after solution can be effectively homogenized, the solution time is set to ≥30min, considering that the long solution time has no significant effect on the microstructure and performance, in order to avoid long time solution, the upper limit of solution is set to 240min. That is, the solution time is set to 30-240min.

[0059] Solution cooling process: The austenitic-based lightweight steel designed in the present application has no κ-carbide precipitation, and is not sensitive to the cooling rate, so it can be cooled by conventional water cooling, oil cooling or air cooling.

[0060] Examples 1-5

[0061] The following specific examples and comparative examples are used to demonstrate the advantages of the composition and process parameter control of the steel of the present application.

[0062] Examples 1-5 of the present application provide a low-carbon austenitic-based high-toughness plastic lightweight steel and a preparation method thereof. The chemical composition of the steel of examples 1-5 is shown in table 1.

[0063] The preparation method of the steel of examples 1-5 includes: steelmaking, slab mold casting, heating, forging, cooling, solution and solution cooling treatment. Among them, the casting blank heating process: the casting blank is heated at 1100-1200℃ for 2-4h. The forging process is forged into a 16mm diameter rod at 840-1150℃; the cooling process after forging adopts air cooling; the solution process is carried out at 950-1150℃, and the solution time is 30-240min; the solution cooling process adopts oil cooling or air cooling.

[0064] The specific process parameters of examples 1-5 are shown in table 2; the main performance test results of the low-carbon austenitic-based high-toughness plastic lightweight steel produced are shown in table 3.

[0065] Table 1 Chemical composition, wt%

[0066] Example C Mn Al P S Nb V Mo W 1 0.09 36.0 6.0 0.010 0.005 0.80 0.14 0.40 0.60 2 0.03 35.0 5.5 0.015 0.006 0.04 0.04 1.5 1.4 3 0.11 35.0 7.0 0.014 0.004 0.05 0.05 1.0 1.1 4 0.12 30.4 6.5 0.012 0.008 0.10 0.08 0.1 1.5 5 0.08 24.0 4.0 0.017 0.012 0.15 0.60 0.8 0.1

[0067] Table 2 Production process parameters

[0068]

[0069]

[0070] Table 3 Partial performance test results

[0071]

[0072] Figure 1 A typical EBSD diffraction quality map of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1; it can be seen that the volume percentage of austenite therein is about 90%, and the volume percentage of ferrite is about 10%.

[0073] Figure 2 A non-deformed austenite bright field morphology of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1; it shows that there is no κ-carbide precipitated phase in the austenite matrix.

[0074] Figure 3 A deformed twin of austenite at a uniformly deformed place of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 after impact at -196 ℃; the formation of a large number of deformed twins significantly toughens the low-temperature toughness of the material.

[0075] Figure 4 A macroscopic morphology photograph of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 after impact at room temperature and low temperature; the sample after impact is not completely broken, indicating that the lightweight steel of the present application shows high toughness at room temperature and low temperature.

[0076] Figure 5 A force displacement and work displacement curve of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 at room temperature; Figure 6 A force displacement and work displacement curve of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 at -80 ℃; Figure 7 A force displacement and work displacement curve of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 at -120 ℃; Figure 8 A force displacement and work displacement curve of the low-carbon austenite-based high-toughness plastic lightweight steel obtained in Example 1 at -196 ℃. The curve shows that the steel of the present application has ultra-high toughness at low temperature and room temperature, and there is no ductile-brittle transition, and the entire fracture process is ductile fracture.

[0077] The microstructure of Examples 1-5 is shown in Table 4 below.

[0078] Table 4 Microstructure of steel

[0079] Numbering Microstructure Average grain size Example 1 Austenitic matrix + about 10% ferrite, no kappa-carbide precipitation About 21.1 um Example 2 Austenitic matrix + about 9% ferrite, no kappa-carbide precipitation About 21.8 um Example 3 Austenitic matrix + about 7% ferrite, no kappa-carbide precipitation About 21.0 um Example 4 Austenitic matrix + about 10% ferrite, no kappa-carbide precipitation About 20.7 um Example 5 Austenitic matrix + about 3% ferrite, no kappa-carbide precipitation About 36.8 um

[0080] The inventors carried out a large number of experimental researches during the research process, and some schemes with poor performance are taken as comparative examples.

[0081] Comparative Example 1

[0082] The comparative example provides a light steel, the component of which is shown in Table 5 below, and the preparation method is the same as that of Example 1, which is not repeated here.

[0083] Comparative Example 2

[0084] The comparative example provides a light steel, the component of which is shown in Table 5 below, and the preparation method is the same as that of Example 1, which is not repeated here.

[0085] Comparative Example 3

[0086] The comparative example provides a light steel, the component of which is the same as that of Example 1, and the solid solution temperature in the preparation method is 900°C, and the rest of the preparation method is the same as that of Example 1, which is not repeated here.

[0087] The main performance test results of the comparative example steel are shown in Table 7. The low temperature impact energy of the comparative example is low, the low temperature toughness is poor, and it is not suitable for low temperature fields such as low temperature pressure vessels.

[0088] Table 5 Chemical composition of comparative example, wt%

[0089] Comparative Example C Mn Al P S Nb V Mo W 1 1.00 30.0 8.0 0.011 0.008 0.10 0.10 0.10 0.10 2 0.09 36.0 2.0 0.015 0.006 0.10 0.18 0.10 0.10 3 0.09 36.0 6.0 0.010 0.005 0.80 0.14 0.40 0.60

[0090] Table 6 Production process parameters of comparative example

[0091]

[0092] Table 7 Partial performance test results of comparative example

[0093]

[0094] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A low-carbon, austenite-based, high-ductility, plastic, lightweight steel, characterized in that, The low-carbon austenite-based high-toughness plastic lightweight steel comprises the following components in percentage by mass: C 0.03%-0.12%, Mn 24.0%-36.0%, Al 4.0%-7.0%, P <0.02%, S <0.01%, Nb 0.04%-1.0%, V 0.04%-1.0%, Mo 0.1%-1.5%, W 0.1%-1.5%, and the balance of Fe and inevitable trace impurities. The preparation method of the low-carbon austenite-based high-toughness plastic lightweight steel comprises the following steps: steelmaking, mold casting, heating, forging, cooling, solid solution, and cooling after solid solution. The heating process comprises the following steps: the casting blank is kept at 1100-1200 ℃ for 2-4 hours for homogenization treatment. The forging process comprises the following steps: the forging is performed at 840-1150 ℃ to form rod materials of different specifications; the open forging temperature is 1050-1150 ℃, and the final forging temperature is 840-880 ℃. The solid solution process comprises the following steps: high-temperature solid solution is performed at 950-1150 ℃, and the solid solution time is 30-240 minutes. The microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel comprises an austenite matrix and a small amount of quasi-polygonal ferrite uniformly distributed on the austenite matrix, and no κ-carbide is precipitated. The volume percentage of the ferrite is 3%-10%. In the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel, the average grain size is 20-37 μm, and the deformation structure at low temperature is mainly nanotwin. The low-carbon austenite-based high-toughness plastic lightweight steel has a stacking fault energy of 23~67 mJ / m 2 ; The low-carbon austenite-based high-toughness plastic lightweight steel has a -196 ℃ KV2 impact energy of 243 J or more and an A of 55% or more.

2. The low carbon, austenite based, high ductility, plastic, lightweight steel of claim 1, wherein, In the microstructure of the low-carbon austenite-based high-toughness plastic lightweight steel, the average grain size is 20.7-37 μm.

3. Low carbon, austenite based, high ductility, plastic, lightweight steel according to claim 1 or 2, characterized in that, The low-carbon austenite-based high-toughness plastic lightweight steel has a -196 ℃ KV2 impact energy of 243-265 J.

4. A method of producing a low carbon, austenite based, high ductility, plastic, lightweight steel according to any one of claims 1 to 3, characterized in that, The preparation method of the low-carbon austenite-based high-toughness plastic lightweight steel comprises the following steps: steelmaking, mold casting, heating, forging, cooling, solid solution, and cooling after solid solution. The heating process comprises the following steps: the casting blank is kept at 1100-1200 ℃ for 2-4 hours for homogenization treatment. The forging process comprises the following steps: the forging is performed at 840-1150 ℃ to form rod materials of different specifications; the open forging temperature is 1050-1150 ℃, and the final forging temperature is 840-880 ℃. The solid solution process comprises the following steps: high-temperature solid solution is performed at 950-1150 ℃, and the solid solution time is 30-240 minutes. In the forging process, the open forging temperature is 1060-1150 ℃.

5. The preparation method according to claim 4, characterized in that, ​

Images