Lightweight, low-alloy cost austenitic stainless steel, its preparation methods and applications

Abstract

This invention discloses a lightweight, low-alloy-cost austenitic stainless steel, its preparation method, and its applications. The preparation method of the lightweight, low-alloy-cost austenitic stainless steel includes the following steps: weighing each component raw material according to mass percentage and smelting it; casting the smelted material into a steel ingot; cooling the steel ingot to room temperature for later use; homogenizing the cooled steel ingot; after homogenization, cooling the sample to 1000-1130℃ and then performing multi-pass hot forging, controlling the final forging temperature at 800-960℃, followed by cooling to room temperature; and solution treating the final forged sample, followed by cooling to room temperature, thus obtaining the lightweight, low-alloy-cost austenitic stainless steel. This invention eliminates carbides in the microstructure after solution treatment, resulting in a material exhibiting excellent comprehensive mechanical properties (high strength, high elongation), achieving a good combination of strength and plasticity.

Description

Technical Field

[0001] This invention belongs to the field of steel materials technology, and particularly relates to a lightweight, low-alloy cost austenitic stainless steel, its preparation method, and its application. Background Technology

[0002] Energy conservation and emission reduction are pressing issues for the metal materials industry, and lightweight and low-cost design of metal materials is a crucial measure to address this problem. Stainless steel, due to its high corrosion resistance, is widely used across various industries; for example, TWIP and TRIP stainless steels are used to replace traditional steels. Austenitic stainless steel, in particular, has received widespread attention and is used in structural components for automobiles, ships, and aerospace.

[0003] A promising design approach involves modifying the composition of austenitic stainless steel by adding aluminum (Al), a lightweight element, to achieve a material with low density and high performance. However, the addition of Al tends to promote excessive ferrite formation, necessitating an increase in carbon (C) content for balance. Yet, high carbon content can lead to excessive carbide precipitation, requiring precise control to ensure material performance. Currently, there is a lack of established guidelines for optimizing the amount of alloying elements added; furthermore, there are few reports on how to effectively eliminate such carbides while maintaining the high specific strength of stainless steel. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the primary objective of this invention is to provide a lightweight, low-alloy-cost austenitic stainless steel, its preparation method, and its application.

[0005] The objective of this invention is achieved through the following technical solution: A lightweight, low-alloy cost austenitic stainless steel comprises, by mass percentage, the following chemical composition: Al 2.0~8.0%, Cr 8.0~13.0%, C 0.3~0.5%, Mn 4.0~12.0%, Ni 3.0~6.0%, with the balance being Fe and unavoidable impurities.

[0006] Preferably, the lightweight, low-alloy-cost austenitic stainless steel comprises, by mass percentage, the following chemical composition: Al 2.12~4.24%, Cr 8.19~12.10%, C 0.32~0.35%, Mn 5.80~10.07%, Ni 4.82~5.01%, with the balance being Fe and unavoidable impurities.

[0007] Preferably, the lightweight, low-alloy cost austenitic stainless steel has a density of 7.04~7.38 g / cm³. 3 .

[0008] Preferably, the lightweight, low-alloy-cost austenitic stainless steel has a single-phase austenitic microstructure or a dual-phase microstructure consisting of austenite and ferrite.

[0009] The preparation method of the above-mentioned lightweight, low-alloy cost austenitic stainless steel includes the following steps: S1. Weigh each component raw material according to the mass percentage and smelt it. After smelting, cast it to obtain a steel ingot. Cool the steel ingot to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is subjected to homogenization treatment. After homogenization treatment, the sample is cooled to 1000~1130℃ and then subjected to multiple hot forgings. The final forging temperature is controlled at 800~960℃, and then cooled to room temperature. S3. The sample that has been forged and cooled to room temperature in step S2 is subjected to solution treatment, and then cooled to room temperature to obtain the lightweight, low-alloy-cost austenitic stainless steel.

[0010] Preferably, the purity of each component raw material in step S1 is ≥99.9%.

[0011] Preferably, the smelting temperature in step S1 is 1480~1650℃, and the steel ingot is obtained by casting after holding at that temperature for 0.5~2 hours.

[0012] Preferably, the cooling to room temperature mentioned in step S1 refers to natural cooling to room temperature in the air.

[0013] Preferably, the homogenization process in step S2 is as follows: heating the sample to 1200~1280℃ and holding it at that temperature for 0.5~3h.

[0014] Preferably, the cooling to room temperature mentioned in step S2 refers to cooling to room temperature along with the furnace.

[0015] Preferably, the solution treatment in step S3 is performed by heating the sample to 850~1180℃ and holding it at that temperature for 15~120 minutes.

[0016] Preferably, the cooling to room temperature mentioned in step S3 refers to water quenching to room temperature.

[0017] The aforementioned lightweight, low-alloy cost austenitic stainless steel is used in the manufacture of structural components for automobiles, ships, and aerospace.

[0018] Compared with the prior art, the beneficial effects of the present invention include: (1) The present invention eliminates carbides in the structure after solution treatment, and the material exhibits excellent comprehensive mechanical properties (high strength and high elongation), and can achieve a good combination of strength and plasticity.

[0019] (2) Compared with traditional TWIP steel and TRIP steel, the present invention re-proportioned the alloy composition and added the lightweight element Al, which reduced the weight without compromising the good performance of the material.

[0020] (3) No precious metals need to be added in this invention, and sufficient Mn and C replace part of the Ni element. The added Al element can also replace part of the Cr element to play a role in corrosion resistance, thus reducing the cost of the alloy. Attached Figure Description

[0021] Figure 1 Metallographic image of the forged steel prepared in Example 1.

[0022] Figure 2 Metallographic image of the solid solution steel prepared in Example 1.

[0023] Figure 3 Metallographic image of the forged steel prepared in Example 2.

[0024] Figure 4 Metallographic image of the solid solution steel prepared in Example 2.

[0025] Figure 5 Metallographic image of the forged steel prepared in Example 3.

[0026] Figure 6 Metallographic image of the solid solution steel prepared in Example 3. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Energy conservation and cost reduction are pressing issues for the metal materials industry, and lightweight and low-cost design of metal materials are crucial measures to address this problem. Against the backdrop of global efforts to actively address climate change and promote green and low-carbon development, the industrial sector is placing higher demands on energy efficiency and carbon emission control. Key industries such as transportation, energy equipment, and aerospace, as major sources of energy consumption and emissions, are accelerating their structural lightweighting upgrades. Replacing traditional steel with lighter materials can significantly reduce equipment weight, effectively improve energy efficiency, and reduce fuel consumption and greenhouse gas emissions during operation, thus achieving a win-win situation for both economic and environmental benefits.

[0029] Stainless steel is widely used in various industries due to its high corrosion resistance. For example, TWIP and TRIP stainless steels have been used to replace traditional steels. Its excellent corrosion resistance allows it to remain stable in harsh environments such as humidity, high salt, and high temperature, significantly extending equipment lifespan and reducing maintenance and replacement costs. This characteristic makes it irreplaceable in marine engineering, chemical equipment, building structures, and household appliances. Among them, austenitic stainless steel has received even more attention due to its excellent comprehensive performance and has been used in structural components in the automotive, shipbuilding, and aerospace industries. A promising design approach is to design the composition of austenitic stainless steel by adding the lightweight element aluminum (Al) to obtain low-density, high-performance materials. However, the addition of aluminum can easily lead to excessive ferrite formation, thus requiring an increase in carbon (C) content for balance. But high carbon content can trigger excessive carbide precipitation, necessitating precise control of carbon content or carbide precipitation behavior to ensure material performance. Currently, there is a lack of reference data for optimizing the amount of alloying elements added; furthermore, there are few reports on how to effectively eliminate such carbides while maintaining the high specific strength of stainless steel.

[0030] To address the aforementioned shortcomings and drawbacks, the present invention aims to provide a lightweight, low-alloy-cost austenitic stainless steel, its preparation method, and its applications. The present invention adds a certain amount of Al to austenitic stainless steel and increases the ratio of Mn and C. By controlling the alloy composition and forming process, a lightweight, low-cost, and high-performance austenitic stainless steel material is obtained, thereby reducing the material's cost and weight without sacrificing performance.

[0031] A lightweight, low-alloy cost austenitic stainless steel comprises, by mass percentage, the following chemical composition: Al 2.0~8.0%, Cr 10.5~13.0%, C 0.3~0.5%, Mn 4.0~12.0%, Ni 3.0~6.0%, with the balance being Fe and unavoidable impurities.

[0032] Preferably, the lightweight, low-alloy-cost austenitic stainless steel comprises, by mass percentage, the following chemical composition: Al 2.12~4.24%, Cr 11.19~12.10%, C 0.32~0.35%, Mn 5.80~10.07%, Ni 4.82~5.01%, with the balance being Fe and unavoidable impurities.

[0033] In some embodiments of the present invention, the C content is 0.32~0.35%, for example, it can be 0.32%, 0.34%, and 0.35%, or any value between any two of the above. The Cr content is 11.19~12.10%, for example, it can be 11.19%, 11.72%, and 12.10%, or any value between any two of the above. C can dissolve in the austenite lattice, playing a role in solid solution strengthening, and at the same time, it can also hinder the movement of dislocations, thereby improving the strength of the material. Increasing the C content can expand the austenite phase region, but if the content is too high, it will form chromium carbide with Cr during welding, resulting in a decrease in Cr content near the austenite grain boundaries, forming a chromium-depleted region, which leads to a decrease in corrosion resistance. Cr is the most important corrosion-resistant element in austenitic stainless steel. Its oxides still have a certain degree of stability at high temperatures.

[0034] In some embodiments of the present invention, the Al content is 2.12% to 4.24%, for example, it can be 2.12%, 3.70%, and 4.24%, or any value between the above two. Al, as an important lightweight element, can significantly reduce the density of materials. However, increasing the Al content leads to the formation of ferrite in the material, reducing the proportion of austenite. Al can refine grains; during hot working or heat treatment, Al acts as a nucleating agent, promoting austenite grain refinement, improving the strength and toughness of the material, and also improving the corrosion resistance of the material.

[0035] In some embodiments of the present invention, the Mn content is 5.80~10.07%, for example, it can be 5.80%, 6.17%, and 10.07%, or any value between the above two. As an austenite stabilizing element, Mn can expand the austenite phase region and reduce the proportion of ferrite formed by the increase of Al. Mn can also dissolve in the austenite lattice, playing a role in solid solution strengthening and improving the overall mechanical properties of the material.

[0036] In some embodiments of the present invention, the Ni content is 4.82-5.01%, for example, it can be 4.82%, 4.89%, and 5.01%, or any value between these two. Ni is an austenite stabilizing element, which can very strongly expand the austenite phase region and increase austenite stability, while also making the oxide film denser and more stable, thus improving corrosion resistance. However, due to its high cost, the present invention increases the content of Mn and C to replace a portion of the Ni, thereby reducing the alloy cost.

[0037] Preferably, the lightweight, low-alloy cost austenitic stainless steel has a density of 7.04~7.38 g / cm³. 3 .

[0038] Preferably, the lightweight, low-alloy-cost austenitic stainless steel has a single-phase austenitic microstructure or a dual-phase microstructure consisting of austenite and ferrite.

[0039] In some embodiments of the present invention, when the amount of ferrite stabilizing element Al added is small, the metallographic structure of stainless steel is single-phase austenite; when the amount of ferrite stabilizing element Al added increases while the amount of austenite stabilizing element is small, a two-phase structure of austenite and a small amount of ferrite will appear.

[0040] The lightweight, low-alloy-cost austenitic stainless steel prepared by this invention has a single-phase austenitic structure or a dual-phase austenitic + ferrite structure, and has high strength, good toughness, and high work hardening rate. It is a high-strength and tough material, and its lightweight and low-alloy-cost properties have good development prospects compared with traditional materials.

[0041] The preparation method of the above-mentioned lightweight, low-alloy cost austenitic stainless steel includes the following steps: S1. Weigh each component raw material according to the mass percentage and smelt it. After smelting, cast it to obtain a steel ingot. Cool the steel ingot to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is subjected to homogenization treatment. After homogenization treatment, the sample is cooled to 1000~1130℃ and then subjected to multiple hot forgings. The final forging temperature is controlled at 800~960℃, and then cooled to room temperature. S3. The sample that has been forged and cooled to room temperature in step S2 is subjected to solution treatment, and then cooled to room temperature to obtain the lightweight, low-alloy-cost austenitic stainless steel.

[0042] In this invention, homogenization treatment is used to eliminate segregation in stainless steel and make the alloying elements evenly distributed; solution treatment is used to eliminate carbides while maintaining the high specific strength of stainless steel.

[0043] Preferably, the purity of each component raw material in step S1 is ≥99.9%.

[0044] Preferably, the smelting temperature in step S1 is 1480~1650℃, and the steel ingot is obtained by casting after holding at that temperature for 0.5~2 hours.

[0045] In some embodiments of the present invention, the smelting temperature in step S1 is 1480~1650℃, and the steel ingot is cast after holding at this temperature for 0.5~2 hours. For example, the smelting temperature can be 1480℃, 1490℃, 1500℃, 1510℃, 1520℃, 1530℃, 1540℃, 1550℃, 1560℃, 1570℃, 1580℃, 1590℃, 1600℃, 1610℃, 1620℃, 1630℃, 1640℃, and 1650℃, or any value between any two of the above. The holding time can be 0.5h, 1h, 1.5h, and 2h, or any value between any two of the above. Excessively high smelting temperatures and excessively long holding times can easily lead to the volatilization of some elements, aggravate furnace lining erosion, and increase inclusions, which not only increases costs but also negatively impacts material performance. Too low a smelting temperature and too short a holding time will prevent the raw materials from melting completely, which is not conducive to their uniform mixing and will affect the performance of the materials.

[0046] Preferably, the cooling to room temperature mentioned in step S1 refers to natural cooling to room temperature in the air.

[0047] Preferably, the homogenization process in step S2 is as follows: heating the sample to 1200~1280℃ and holding it at that temperature for 0.5~3h.

[0048] In some embodiments of the present invention, the specific operation of the homogenization treatment in step S2 is as follows: heating the sample to 1200~1280℃ and holding it at that temperature for 0.5~3h; for example, the heating temperature can be 1200℃, 1210℃, 1220℃, 1230℃, 1240℃, 1250℃, 1260℃, 1270℃, and 1280℃, or any two of the above values. The holding time can be 0.5h, 1h, 1.5h, 2h, 2.5h, and 3h, or any two of the above values. Excessively high homogenization temperatures and excessively long holding times can easily cause surface element volatilization, excessively coarse grains, severe oxidation, and grain boundary embrittlement, leading not only to increased costs but also to detrimental material performance. Excessively low homogenization temperatures and excessively short holding times can result in insufficient dissolution of harmful phases and the inability to eliminate local segregation of alloying elements, thereby significantly reducing material performance.

[0049] Preferably, the cooling to room temperature mentioned in step S2 refers to cooling to room temperature along with the furnace.

[0050] Preferably, the solution treatment in step S3 is performed by heating the sample to 850~1180℃ and holding it at that temperature for 15~120 minutes.

[0051] In some embodiments of the present invention, the specific operation of the solution treatment in step S3 is as follows: heating the sample to 850~1180℃ and holding it at that temperature for 15~120 min; for example, the heating temperature can be 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃, 960℃, 970℃, 980℃, 990℃, 1000℃, 1010℃, 1020℃, 1030℃, 1040℃, 1050℃, 1060℃, 1070℃, 1080℃, 1090℃, 1100℃, 1110℃, 1120℃, 1130℃, 1140℃, 1150℃, 1160℃, 1170℃, and 1180℃, as well as any two of the above values. The holding time can be 15 min, 30 min, 45 min, 60 min, 75 min, 90 min, 105 min, and 120 min, or any value between these two. Excessively high solution treatment temperatures and excessively long holding times can easily cause surface element volatilization and excessively coarse grains, leading not only to increased costs but also negatively impacting material performance. Conversely, excessively low solution treatment temperatures and excessively short holding times can result in incomplete dissolution of carbides, thus affecting material performance.

[0052] Preferably, the cooling to room temperature mentioned in step S3 refers to water quenching to room temperature.

[0053] The aforementioned lightweight, low-alloy cost austenitic stainless steel is used in the manufacture of structural components for automobiles, ships, and aerospace.

[0054] Example 1 A lightweight, low-alloy cost austenitic stainless steel is prepared by the following chemical composition by mass percentage: Al 2.12%, Cr 11.19%, C 0.34%, Mn 6.17%, Ni 4.82%, with the balance being Fe and unavoidable impurities.

[0055] The specific steps for preparing the aforementioned lightweight, low-alloy cost austenitic stainless steel are as follows: S1. Weigh each component raw material (purity ≥99.9%) according to mass percentage and smelt it at 1500℃. After holding at the temperature for 1 hour, cast it to obtain a steel ingot. Let the steel ingot cool naturally in the air to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is heated to 1250°C and held for 2 hours for homogenization treatment. After homogenization treatment, the sample is cooled to 1100°C and then subjected to multiple hot forging passes. The final forging temperature is controlled at 950°C. The sample is then cooled to room temperature in the furnace. The steel at this time is called forged steel. S3. The sample that has been finally forged and cooled to room temperature in step S2 is heated to 1180°C and held for 30 minutes for solution treatment. Then it is water quenched and cooled to room temperature to obtain the lightweight, low-alloy cost austenitic stainless steel. The steel at this time is called solution-treated steel.

[0056] The forged and solution-treated steels prepared in Example 1 were subjected to grinding, polishing, and etching, and their metallographic structure was observed using an optical microscope. The specific procedure was as follows: mechanical grinding was performed sequentially using 400, 600, 800, 1000, 1200, 1500, and 3000 grit sandpaper, followed by polishing with 2.5 μm diamond polishing paste. Etching was performed using Beraha II etching solution (composition: 100 mL water, 50 mL concentrated hydrochloric acid, 6 g ammonium bifluoride, and 1 g potassium metabisulfite) at a temperature of 25 °C for 20 s.

[0057] Figure 1 Metallographic image of the forged steel prepared in Example 1, from Figure 1 It can be seen that the matrix is ​​austenite, with continuous distribution of carbides within the grains, and carbides can also be observed at the grain boundaries.

[0058] Figure 2 Metallographic image of the solid solution steel prepared in Example 1, from Figure 2 It can be seen that the matrix is ​​austenite, and the carbides have completely disappeared.

[0059] Example 2 A lightweight, low-alloy-cost austenitic stainless steel is prepared by the following chemical composition by mass percentage: Al 3.70%, Cr 12.10%, C 0.32%, Mn 5.80%, Ni 5.01%, with the balance being Fe and unavoidable impurities.

[0060] The specific steps for preparing the aforementioned lightweight, low-alloy cost austenitic stainless steel are as follows: S1. Weigh each component raw material (purity ≥99.9%) according to mass percentage and smelt it at 1500℃. After holding at the temperature for 1 hour, cast it to obtain a steel ingot. Let the steel ingot cool naturally in the air to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is heated to 1250°C and held at that temperature for 2 hours for homogenization treatment. After homogenization treatment, the sample is cooled to 1100°C and then subjected to multiple hot forging passes. The final forging temperature is controlled at 950°C. The sample is then cooled to room temperature in the furnace. The steel at this point is called forged steel. S3. The sample that has been finally forged and cooled to room temperature in step S2 is heated to 1180°C and held for 30 minutes for solution treatment. Then it is water quenched and cooled to room temperature to obtain the lightweight, low-alloy cost austenitic stainless steel. The steel at this time is called solution-treated steel.

[0061] Figure 3 Metallographic image of the forged steel prepared in Example 2, from Figure 3 It can be seen that the matrix is ​​austenite + ferrite, with continuous distribution of carbides within the austenite grains, and carbides can also be observed at the grain boundaries.

[0062] Figure 4 Metallographic image of the solid solution steel prepared in Example 2, from Figure 4 It can be seen that the matrix is ​​austenite with a small amount of ferrite, and the carbides have completely disappeared.

[0063] Example 3 A lightweight, low-alloy cost austenitic stainless steel is prepared by the following chemical composition by mass percentage: Al 4.24%, Cr 11.72%, C 0.35%, Mn 10.07%, Ni 4.89%, with the balance being Fe and unavoidable impurities.

[0064] The specific steps for preparing the aforementioned lightweight, low-alloy cost austenitic stainless steel are as follows: S1. Weigh each component raw material (purity ≥99.9%) according to mass percentage and smelt it at 1500℃. After holding at the temperature for 1 hour, cast it to obtain a steel ingot. Let the steel ingot cool naturally in the air to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is heated to 1250°C and held at that temperature for 2 hours for homogenization treatment. After homogenization treatment, the sample is cooled to 1100°C and then subjected to multiple hot forging passes. The final forging temperature is controlled at 950°C. The sample is then cooled to room temperature in the furnace. The steel at this point is called forged steel. S3. The sample that has been finally forged and cooled to room temperature in step S2 is heated to 1180°C and held for 30 minutes for solution treatment. Then it is water quenched and cooled to room temperature to obtain the lightweight, low-alloy cost austenitic stainless steel. The steel at this time is called solution-treated steel.

[0065] Figure 5 Metallographic image of the forged steel prepared in Example 3, from Figure 5 It can be seen that the matrix is ​​austenite + ferrite, with continuous distribution of carbides within the austenite grains, and carbides can also be observed at the grain boundaries.

[0066] Figure 6 Metallographic image of the solid solution steel prepared in Example 3, from Figure 6 It can be seen that the matrix is ​​austenite with a small amount of ferrite, and the carbides have completely disappeared.

[0067] The raw material composition ratio of the austenitic stainless steel described in Examples 1-3 is shown in Table 1.

[0068] Table 1 Raw material group distribution ratio

[0069] The steel prepared in step S2 in Examples 1-3 is defined as forged steel, and the steel after step S3 (solution treatment) is defined as solution-treated steel. The mechanical properties of the steel in these two states were tested, and the results are shown in Tables 2 and 3, respectively.

[0070] Table 2 Mechanical properties of forged steel

[0071] Table 3 Mechanical properties of solution-treated steel

[0072] Referring to the statistical data in Tables 2 and 3, we can see that the solution-treated state has a better strength-ductility product than the forged state, but it loses some tensile strength. After solution treatment, the resistance to dislocation movement in the matrix decreases due to the disappearance of carbides. During material deformation, dislocations can move more freely. Dislocation movement is the main mechanism of plastic deformation in materials; reduced resistance to dislocation movement enhances the material's plastic deformation capacity, thus increasing elongation. However, the disappearance of the strengthening effect of the second-phase carbides leads to a decrease in the yield strength of the material. Simultaneously, solution treatment causes grain growth; according to the Hall-Petch equation, increased grain size leads to decreased material strength.

[0073] The deformation mechanism of austenitic stainless steel during deformation is influenced by stacking fault energy. Mn and Al, both elements in the composition of this invention, increase stacking fault energy. With increasing stacking fault energy, the deformation mechanism of all experimental steels in this invention is deformation twinning, resulting in similar work hardening rates. This invention compares different combinations of strength and plasticity, finding that the maximum strength-ductility product (the product of tensile strength and elongation after fracture) reaches 50 GPa·%, far exceeding that of third-generation automotive steel (strength-ductility product 30 GPa·%).

[0074] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A lightweight, low-alloy cost austenitic stainless steel, characterized in that, By mass percentage, it comprises the following chemical components: Al 2.0~8.0%, Cr 8.0~13.0%, C 0.3~0.5%, Mn 4.0~12.0%, Ni 3.0~6.0%, with the balance being Fe and unavoidable impurities.

2. The lightweight, low-alloy cost austenitic stainless steel according to claim 1, characterized in that, By mass percentage, it comprises the following chemical components: Al 2.12~4.24%, Cr 8.19~12.10%, C 0.32~0.35%, Mn 5.80~10.07%, Ni 4.82~5.01%, with the balance being Fe and unavoidable impurities.

3. The lightweight, low-alloy cost austenitic stainless steel according to claim 1 or 2, characterized in that, The lightweight, low-alloy cost austenitic stainless steel has a single-phase austenitic microstructure, or a dual-phase microstructure consisting of austenite and ferrite; and / or The lightweight, low-alloy cost austenitic stainless steel has a density of 7.04~7.38 g / cm³. 3 .

4. The method for preparing the lightweight, low-alloy cost austenitic stainless steel according to any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Weigh each component raw material according to the mass percentage and smelt it. After smelting, cast it to obtain a steel ingot. Cool the steel ingot to room temperature for later use. S2. The steel ingot cooled to room temperature in step S1 is subjected to homogenization treatment. After homogenization treatment, the sample is cooled to 1000~1130℃ and then subjected to multiple hot forgings. The final forging temperature is controlled at 800~960℃, and then cooled to room temperature. S3. The sample that has been forged and cooled to room temperature in step S2 is subjected to solution treatment, and then cooled to room temperature to obtain the lightweight, low-alloy-cost austenitic stainless steel.

5. The method for preparing lightweight, low-alloy cost austenitic stainless steel according to claim 4, characterized in that, The smelting temperature in step S1 is 1480~1650℃, and the steel ingot is obtained by casting after holding at that temperature for 0.5~2 hours.

6. The method for preparing lightweight, low-alloy cost austenitic stainless steel according to claim 4, characterized in that, Step S1, cooling to room temperature, refers to natural cooling to room temperature in air; and / or Step S2, cooling to room temperature, refers to cooling the furnace to room temperature.

7. The method for preparing lightweight, low-alloy cost austenitic stainless steel according to claim 4, characterized in that, The specific operation of the homogenization treatment in step S2 is as follows: heat the sample to 1200~1280℃ and keep it at that temperature for 0.5~3h.

8. The method for preparing lightweight, low-alloy cost austenitic stainless steel according to claim 4, characterized in that, The specific operation of the solution treatment in step S3 is as follows: heat the sample to 850~1180℃ and keep it at that temperature for 15~120min.

9. The method for preparing lightweight, low-alloy cost austenitic stainless steel according to claim 4, characterized in that, Step S3, cooling to room temperature, refers to water quenching to room temperature.

10. The use of the lightweight, low-alloy cost austenitic stainless steel according to any one of claims 1 to 3 in the manufacture of structural components for automobiles, ships and aerospace.

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