Low-strength high-formability austenitic stainless steel and manufacturing method thereof

Abstract

According to the low-strength high-formability austenitic stainless steel and the manufacturing method thereof, C + N is controlled to be smaller than or equal to 0.035%, the manganese content is controlled to be within 1.5%, the tin content is limited to be 0.01%-0.30%, the copper content is limited to be 2.4%-4.5%, and the tin-copper ratio is that (Sn / Cu) * 1000 is larger than or equal to 5 and smaller than or equal to 50, so that it is guaranteed that tin exerts the beneficial effects such as the corrosion resistance is improved, and the harm of tin segregation can be controlled to be at the low level; according to the finally obtained austenitic stainless steel, the yield strength is smaller than or equal to 160 Mpa, the tensile strength is smaller than or equal to 500 Mpa, the ductility is larger than or equal to 55%, the grain size grade is 6-8, edge cracks cannot occur during hot rolling, the martensite content of a cup drawing deformation part is 0.05% or below during large deformation machining, in other words, the austenite phase is still stable under the complex deformation condition, deformation cracks are avoided, and the service life of the austenitic stainless steel is prolonged. The comprehensive effects of high corrosion resistance, low strength and high forming machinability of the material are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of stainless steel, and in particular relates to an economical low-strength, high-formability austenitic stainless steel and a manufacturing method thereof. Background Art

[0002] Copper has a wide range of applications. For example, air conditioners and refrigerators account for 75% of my country's total copper demand. Furthermore, with the development of the automotive industry, particularly the popularity of new energy vehicles, the amount of copper used per vehicle has increased from 23 kg in gasoline-powered vehicles to 83 kg. This has led to a continuous rise in copper prices, increasing production costs for air conditioners, refrigerators, and other refrigeration industries, weakening their international competitiveness. Furthermore, copper pipes are prone to corrosion, which can lead to problems such as leaks.

[0003] Conventional austenitic stainless steels (such as SUS304 stainless steel) offer excellent corrosion resistance and are relatively inexpensive. If they could replace copper in the refrigerant piping of heat exchangers, they could significantly reduce production costs in the refrigeration industry. However, conventional austenitic stainless steels are difficult to machine and deform due to their high hardness, limiting their application in this area. Conventional SUS305 stainless steel also offers excellent corrosion resistance, while its strength and hardness are significantly lower than SUS304. However, its alloy's higher nickel content results in higher costs.

[0004] For softer stainless steels, while their room-temperature strength and hardness are lower than those of conventional SUS304, the impact of phase transformation strengthening (such as the formation of martensite) resulting from subsequent component processing must also be considered. Some soft stainless steels, such as SUS304ES developed in Japan, reduce nickel content and exhibit typical low strength and hardness characteristics. However, after repeated forming processes, the austenite-to-martensite transformation still occurs, resulting in martensitic transformation strengthening under large deformation conditions, exhibiting the characteristics of metastable austenitic stainless steel. Especially in processing scenarios involving materials that are difficult to deform, such as punching and flanging, the material's stress state becomes more complex, with stress concentration and multi-directional stresses, increasing the driving force for phase transformation. Furthermore, the deformation is large and uneven, with large local deformation and a high degree of work hardening, providing more nucleation points for phase transformation. Furthermore, the material's austenite stability and composition sensitivity are more easily disrupted under complex deformation conditions, promoting phase transformation and, in turn, leading to cracks (for example, cracks due to severe deformation at the edges). This means that existing soft stainless steel materials cannot meet the requirements of complex forming designs. Furthermore, the pitting corrosion resistance of existing soft stainless steels is also unsatisfactory, with a maximum pitting potential of only 160 mV. Therefore, there is still room for improvement in both the performance of existing ultra-soft austenitic stainless steels in difficult-to-deform processes such as punching and flanging, as well as their pitting corrosion resistance. Summary of the Invention

[0005] An object of the present invention is to provide a low-strength, high-formability austenitic stainless steel having the characteristics of low strength, no phase change during deformation and high corrosion resistance.

[0006] A low-strength, high-formability austenitic stainless steel having the following chemical composition by mass percentage: C: 0.001-0.02%, Si: 0.01-0.5%, Mn: 0.01-1.5%, P<0.04%, S<0.01%, Cr: 17.0-20.0%, Ni: 9.0-14.0%, Cu: 2.4-4.5%, N≤0.025%, C+N≤0.035%, Mo: 0.01-0.3%, Al: 0.005-0.05%, Sn: 0.01-0.30%, and the balance being Fe and unavoidable impurities; and the contents of the above components must also meet the following requirement: 5≤(Sn / Cu)*1000≤50.

[0007] The functions of the various components of the present invention are as follows: Carbon (C) solid solution in stainless steel can improve the steel's strength, but excessive carbon content can reduce the steel's plasticity, improve strength and hardness, and form martensitic transformation during large deformation, affecting forming properties such as deep drawing and flanging, while also reducing corrosion resistance. Carbon is also an austenitizing element, promoting the formation of a single austenitic structure, preventing the formation of high-temperature ferrite, and improving processability. The present invention controls the carbon content to 0.001-0.02%.

[0008] N: Nitrogen can improve the corrosion resistance and increase the strength of austenitic stainless steel, but it is not conducive to the formability of the steel. Therefore, the nitrogen content is controlled below 0.025%.

[0009] Nitrogen and carbon exist as interstitial atoms. When interstitial atoms enter the metal lattice, they occupy interstitial positions, causing lattice distortion. Lattice distortion makes the material more susceptible to cracking and fracture during processing, reducing the material's formability. To minimize the total amount of interstitial atoms and their impact on steel formability, this application specifically proposes a target of C+N ≤ 0.035%.

[0010] Si: Silicon can play a deoxidizing role in the smelting of austenitic stainless steel. The silicon in the stainless steel matrix increases the strength of the steel to a certain extent and reduces the processability of the material. In the present invention, the silicon content is controlled at 0.01-0.5%.

[0011] Mn: A certain manganese content is beneficial to the pickling of the coils and is also beneficial to the stability of austenite. Excessive manganese content will produce manganese sulfide inclusions that reduce corrosion resistance, especially pitting corrosion resistance. On the other hand, excessive manganese will affect the function of other beneficial elements in stainless steel. Changes in manganese content will also significantly affect the passivation film performance of austenitic stainless steel. High manganese content weakens the quality and stability of the passivation film, reduces the protective ability of the passivation film, and increases the risk of corrosion. This makes it more prone to corrosion in acidic, alkaline, and chloride-containing corrosive environments, and the probability of corrosion problems such as pitting corrosion and crevice corrosion will increase. In order to ensure good corrosion resistance, the present invention specifically limits the manganese content to 0.01~1.5%.

[0012] P, S: Phosphorus and sulfur are considered harmful elements in stainless steel and should be controlled as low as possible.

[0013] Cr: Chromium is the most important alloying element in stainless steel. It easily forms a dense passivation film of Cr2O3 in contact with oxygen, thereby improving the corrosion resistance of steel. Too low a Cr content affects the corrosion resistance, while too high a Cr content causes the precipitation of a ferrite phase, thereby increasing the strength and hardness. In the present invention, the chromium content is between 17.0% and 20.0%.

[0014] Ni: In low-strength, non-magnetic austenitic stainless steel, the alloying element nickel (Ni) plays a vital role: first, it stabilizes the austenite structure. Nickel is a strong austenite-forming element that can significantly expand the austenite phase region, allowing stainless steel to maintain a stable austenite structure at room temperature and over a wide temperature range. This is one of the keys to achieving non-phase transformation strengthening properties during stainless steel processing deformation. At the same time, the austenite structure itself is non-magnetic, so nickel ensures that stainless steel will not undergo phase transformation and produce magnetic interference during use, meeting the needs of application scenarios such as electronic equipment and medical equipment that have high non-magnetic properties. Secondly, it regulates mechanical properties. Similar to the role of copper, it helps to reduce the strength of stainless steel to meet the low-strength characteristic requirements, while improving the toughness and ductility of the material. This makes stainless steel easier to deform during processing operations such as stamping, bending, and stretching, reducing the probability of defects such as cracks during processing and improving the material's forming properties. Secondly, it improves corrosion resistance. Nickel can enhance stainless steel's resistance to a variety of corrosive media, especially in complex media where oxidizing and reducing environments are intertwined. Nickel can work synergistically with other alloying elements such as chromium to improve the stability of the passivation film on the surface of stainless steel, making it denser and stronger, thereby effectively blocking the erosion of corrosive media and extending the service life of stainless steel products. However, nickel is a relatively expensive alloying element, and its large-scale use will increase material costs. Reasonable control of its addition amount is necessary to balance multiple factors such as performance and cost. The nickel content of this patent is Ni: 9.0~14.0%.

[0015] Cu: In austenitic stainless steel, copper (Cu) has many functions such as improving corrosion resistance, adjusting mechanical properties, and improving processing performance. However, this application mainly considers its mechanical adjustment performance, and by adding a high content of Cu, the material exhibits low-strength characteristics. At the same time, a high content of Cu can also produce the following auxiliary effects: copper also has a certain effect of stabilizing austenite, and the effect is only 1 / 4 of nickel. Under the premise of ensuring the nickel content, a high content of copper is added, and copper can be dissolved into the matrix, and together with nickel, it plays a role in strengthening and stabilizing the austenite structure. Since excessive addition of copper will bring some negative effects, such as causing poor hot working performance, etc., the appropriate copper content needs to be comprehensively determined according to specific use requirements and production processes. Therefore, the present invention selects 2.4~4.5%.

[0016] Sn: Tin (Sn) has multiple benefits, including improving corrosion resistance, enhancing austenite stability, and improving processability. However, this application primarily considers its improved corrosion resistance. The addition of tin forms a protective film containing SnO2 on the stainless steel surface. SnO2 reduces defects in the passive film, improving its integrity and density. Furthermore, Sn oxides and hydroxides readily deposit within pitting pits, enhancing the self-healing properties of the passive film and thereby inhibiting the development of steady-state pitting corrosion. Low tin content has little effect on inhibiting pitting corrosion. However, high tin content, due to its low solid solubility in austenite, can lead to segregation toward grain boundaries. Tin at grain boundaries may affect carbide precipitation and the distribution of elements like chromium, increasing susceptibility to intergranular corrosion. Furthermore, excessively high tin content increases the risk of defects such as cracking during hot working. Taking all these factors into consideration, this application specifically limits the Sn content to 0.01% to 0.30%. The addition of tin also produces the following auxiliary effects: (1) An appropriate amount of tin can refine the grains. Grain refinement can increase the grain boundary area. The grain boundary serves as the nucleation site of austenite, which helps to form more austenite grains, thereby increasing the nucleation rate of austenite. At the same time, fine grains can hinder dislocation movement, reduce the possibility of austenite transforming to other phases due to dislocation movement, and improve the structural stability of austenite; (2) Tin can also reduce the hot working temperature of the material, improve the hot working performance, and thus reduce the formation of hot cracks; Tin improves the forming performance by improving the efficiency of cold working.

[0017] Sn / Cu: While both copper and tin can improve the corrosion resistance of stainless steel, copper's melting point is much higher than tin, so excessive amounts of copper can have greater negative effects (such as reduced hot workability). Therefore, tin is added to copper-containing austenitic stainless steel to further enhance corrosion resistance. The inventors unexpectedly discovered that combining the tin-copper content with a tin-copper ratio (5 ≤ (Sn / Cu) * 1000 ≤ 50) ensures that tin can exert its beneficial effects, such as improving the material's corrosion resistance, while minimizing the risk of tin segregation. The inventors speculate that an appropriate amount of copper may interact with tin or alter the alloy's microstructure, resulting in a more uniform distribution of tin in the steel and thus reducing the occurrence of tin segregation.

[0018] This patent combines the processing performance requirements of the material trial scenario and takes into account the comprehensive characteristics of stainless steel, such as low strength (low strength determines its better processability), high corrosion resistance, and deformation without phase change. Compared with the existing technology, the advantages of this invention are: (1) By achieving ultra-low carbon and nitrogen in austenitic stainless steel and reducing the solid solution strengthening effect of interstitial elements, the formability can be effectively improved. As a design requirement for high formability, especially for deep drawing and flanging, the interstitial elements C and N must be strictly controlled, and C+N must be controlled to ≤0.035%; (2) Under certain nickel content conditions, by adding a high content of copper element 2.4~4.5%, the strength of stainless steel is reduced, making it exhibit low strength characteristics, while more copper can be dissolved into the austenite phase, playing a role in better stabilizing the austenite structure. In addition, copper can also reduce the cold hardening tendency of austenitic stainless steel, improve the cold working formability, and enable the material to obtain a larger deformation under a smaller forming force. Therefore, adding a higher copper content and nickel content at the same time can better balance mechanical properties such as strength and cold working adaptability; (3) Since manganese increases pitting corrosion sensitivity, for high corrosion resistance requirements, the manganese content needs to be strictly controlled within 1.5%; (4) By combining the tin-copper content with the control of the tin-copper ratio, it is possible to ensure that tin plays its beneficial role to a certain extent, such as improving corrosion resistance, while also controlling the harm of tin segregation at a low level; in addition, it can also take into account other properties, such as thermoplasticity and strength, so that copper-containing austenitic stainless steel has good comprehensive properties; (5) The austenitic stainless steel finally obtained in the present application has a yield strength of ≤160Mpa, a tensile strength of ≤500Mpa, an elongation of ≥55%, a grain size of 6-8, and no edge cracking during hot rolling. Moreover, during large deformation processing, such as cupping, the martensite content is less than 0.05%. That is, under complex deformation conditions, the austenite phase is stable and rarely transforms into martensite, thus avoiding deformation cracks. Ultimately, the material achieves the comprehensive effect of high corrosion resistance, low strength, and high formability, and stainless steel can replace copper (plates or tubes) in heat exchange systems and various control systems such as air conditioners and automobiles. At the same time, compared with metallic copper, the stainless steel of the present invention can save expensive material costs.

[0019] To ensure non-magnetic properties under high forming conditions, the chemical composition of the present invention meets the following requirements for non-magnetic properties in applications such as electronic equipment and medical devices. The chemical composition of the present invention must also meet the following requirements: NM = 551-462 (C+N) - 9.2Si - 8.1Mn - 29 (Ni+Cu+Sn) - 13.7Cr ≤ -50. The NM value is a key indicator of the non-magnetic properties of stainless steel. A lower NM value indicates non-magnetic stability and a lower resistance to phase transformation during deformation, which in turn reduces the likelihood of hardening during deformation, thus improving formability.

[0020] A second object of the present invention is to provide a method for manufacturing low-strength, high-formability austenitic stainless steel according to the first object, comprising the following steps: (1) Melting and forging: The ingredients are prepared and melted according to the formula system designed for the chemical composition of the low-strength, high-formability austenitic stainless steel described in the first object of the present invention, and the ingot is cast in a mold, and then cooled at a cooling rate of ≥50°C / s. After the ingot is cooled, it is heated in a furnace at a heating temperature of 1100~1250°C and a holding time of 50~150min. After heating, it is forged out of the furnace, with the initial forging temperature not lower than 1150°C and the final forging temperature greater than 900°C. After forging, it is air-cooled; (2) Hot rolling: The forged steel billet is milled to remove the surface oxide scale, and then hot rolled. It is heated at 1080~1250℃ and kept warm for 60~100min before rolling begins. The starting rolling temperature is greater than 1100℃, and the final rolling temperature is controlled at above 850℃. It is water-cooled after rolling. (3) Homogenization annealing: annealing the hot-rolled steel plate at a temperature of 1000-1100°C for 2-10 minutes; (4) Cold rolling: The hot-rolled steel plate after annealing is pickled and surface polished before cold rolling. The total reduction rate of cold rolling is not less than 70%. After cold rolling, bright annealing is performed. The bright annealing temperature is 1000~1100℃, the bright annealing time is 1~10min, and the bright annealing speed is controlled at 5~50m / min. The grain size of the stainless steel plate is controlled to 5~10 levels, and the surface roughness is guaranteed to be Ra0.003~0.08mm, so as to obtain a stainless steel product with a bright surface.

[0021] Furthermore, the bright annealing in step (4) may also adopt a conventional annealing process, and pickling is performed after conventional annealing to obtain the stainless steel product with a bright surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the metallographic structure diagram of the stainless steel material of Example 1 of the present invention; Figure 2 A photograph of the magnetic permeability of the cupping portion before cracking, showing the cupping process using the stainless steel material of Example 3 of the present invention; Figure 3 A photograph of the magnetic permeability of the cupping portion when the cupping limit is exceeded and cracking occurs is shown for cupping processing using the stainless steel material of Example 3 of the present invention; Figure 4 This is the hot rolling edge cracking situation of comparative example 3; Figure 5 This is a rendering of the flanging process using the low-strength, high-formability austenitic stainless steel of the present application; Figure 6 This is the effect diagram of flanging processing of SUS304L stainless steel in comparative example 5. DETAILED DESCRIPTION

[0023] The following is a detailed description of the specific embodiments of the low-strength, high-formability austenitic stainless steel and its manufacturing method of the present invention: Example 1

[0024] A low-strength, high-formability austenitic stainless steel having the following chemical composition in percentage by weight: C: 0.012%, Si: 0.42%, Mn: 0.85%, P: 0.012%, S: 0.002%, Cr: 17.0%, Ni: 10.3%, Cu: 2.5%, N: 0.013%, C+N≤0.035%, Mo: 0.01-0.3%, Al: 0.005-0.05%, Sn: 0.06%, the balance being Fe and unavoidable impurities; and the contents of the above components must also meet the following requirement: 5≤(Sn / Cu)*1000≤50.

[0025] The method for manufacturing the low-strength, high-formability austenitic stainless steel comprises the following steps: (1) Melting and Forging: The ingredients are prepared and melted according to the formula system designed for the chemical composition of the above-mentioned low-strength, high-formability austenitic stainless steel. The cylindrical ingot is cast in a mold and cooled at a cooling rate of 56°C / s. After cooling, the ingot is heated in a furnace at a heating temperature of 1205°C and a holding time of 50-150 minutes. The billet is then forged into a 50*30*300mm square billet. The initial forging temperature is 1170°C, the final forging temperature is 1010°C, and water cooling is performed after forging. (2) Hot rolling: After forging, the steel billet is milled to remove the surface oxide scale, and then hot rolled. It is heated at 1120℃ and kept warm for 60~100min before rolling begins. The starting rolling temperature is 1185℃, and the thickness is rolled to 2~5mm. The final rolling temperature is 910℃, and the steel billet is water-cooled after rolling. (3) Homogenization annealing: anneal the hot-rolled steel plate at a temperature of 1080°C for 2-10 minutes. (4) Cold rolling: The hot-rolled steel plate after annealing is pickled and surface polished before cold rolling. The total reduction rate of cold rolling is not less than 70%. After the cold rolling, bright annealing is set. The bright annealing temperature is 1060℃, the bright annealing time is 1-10min, the annealing speed is controlled at 5-50m / min, and the grain size of the stainless steel plate is controlled at level 5-10 (specifically: level 7), and a stainless steel product with a surface roughness Ra of 0.03~0.50μm is obtained.

[0026] Examples 2-5 and Comparative Examples 1-4 follow the same process as Example 1, differing in the mass percentages of the primary chemical components and key technical parameters of the manufacturing process. The weight percentages of the primary chemical components of Examples 1-5 and Comparative Examples 1-4 are shown in Table 1, where NM = 551-462 (C+N) - 9.2 Si - 8.1 Mn - 29 (Ni+Cu+Sn) - 13.7 Cr ≤ -50. Key technical parameters of the manufacturing process are shown in Table 2. The present invention also provides the standard composition of conventional austenitic stainless steel SUS304L as Comparative Example 5. The performance parameters of the stainless steel products of each Example and Comparative Example are shown in Table 3.

[0027] Table 1 Main chemical components of Examples and Comparative Examples by weight (wt%)

[0028] Table 2 Key technical parameters of the examples and comparative examples

[0029] Table 3 Performance parameters of the examples and comparative examples

[0030] Since the austenite phase is usually non-magnetic, while the martensite phase formed by its phase transformation is magnetic, the present invention characterizes the deformation martensite content of the material by the value of magnetic permeability.

[0031] As shown in Tables 1-3, the chemical composition mass percentages and key manufacturing process parameters of Examples 1-5 meet the requirements of the present invention. The stainless steel products meet the following performance and microstructure requirements: yield strength ≤ 160 MPa; tensile strength ≤ 500 MPa; elongation ≥ 55%; pitting potential ≥ 280 mV; and grain size grade 5-10. Compared to existing SUS304L stainless steel (Comparative Example 5), the yield strength and tensile strength are significantly reduced, while the elongation is higher, making it easier to process. More importantly, the austenite phase is more stable, and the martensite phase variation caused by hot rolling and cupping is extremely low. This reduces the impact of phase transformation strengthening caused by complex processes such as cupping on the material's strength and avoids the occurrence of processing deformation cracks. A comparison of Comparative Examples 1 and 3 with Examples 1-5 shows that controlling the interstitial C and N atoms to achieve C+N ≤ 0.035% can minimize strength indicators and improve processability. From the comparison between comparative examples 2-4 and examples 1-5, it can be seen that when the Sn content is higher than the design requirement, the grain boundaries will be softened or even melted due to the segregation of the low melting point Sn grain boundaries, resulting in weakened grain boundary strength and cracking (such as Figure 4 As shown in the figure, an appropriate amount of Sn can improve the corrosion resistance of stainless steel. At the same time, it works together with Cu in an appropriate proportion to improve its corrosion resistance and help maintain the stability of the austenite structure, so that the stainless steel can maintain a good organizational structure and performance under difficult and complex processing operations (such as cupping processing, etc.), and the formability and processability are improved at the same time, which is conducive to reducing the incidence of processing cracks.

[0032] The metallographic structure of Example 1 is as follows: Figure 1 As shown, the structure is single austenite, and the twin structure characteristics can be seen.

[0033] The present application also provides a photo of the magnetic permeability test of the cupping test on the stainless steel material (1.0 mm thickness) of Example 3. When the cupping part is not cracked, the magnetic permeability cannot be detected (e.g. Figure 2 As shown). At this time, the relative permeability is 1.000. The material with a relative permeability of 1 is called a non-magnetic material, and its magnetic permeability is the same as that in a vacuum. Under the cupping limit condition (cracking), its magnetic permeability value is 1.005~1.007 (as shown). Figure 3 As shown in the figure, the magnetic permeability of the non-magnetic steel is much lower than the standard value of 1.02 (ISO15692-2017 or ASTMA996 / A996M) of non-magnetic steel, that is, it still has a good non-magnetic effect under large deformation, indicating that the austenite of the composition-designed material of the present invention has good stability and better formability.

[0034] When the steel thickness is equal, the flange height can reach 8mm when the low-strength high-formability austenitic stainless steel of the present application is used for flange processing (e.g. Figure 5 As shown), while the flange height of SUS304L stainless steel in comparative example 5 is only 2 mm (as shown Figure 6 The above description is only an embodiment of the present invention and does not limit the scope of the present invention. Any equivalent process transformation made by using the contents of the present invention specification, or directly or indirectly applied to other related technical fields, is also included in the scope of patent protection of the present invention.

Claims

1. A low-strength, high-formability austenitic stainless steel, characterized in that: The mass percentage of its chemical composition is: C: 0.001~0.02%, Si: 0.01~0.5%, Mn: 0.01~1.5%, P<0.04%, S<0.01%, Cr: 17.0~20.0%, Ni: 9.0~14.0%, Cu: 2.4~4.5%, N≤0.025%, C+N≤0.035%, Mo: 0.01~0.3%, Al: 0.005~0.05%, Sn: 0.01~0.30%, and the balance is Fe and unavoidable impurities; at the same time, the content of the above components must also meet the following requirements: 5≤(Sn / Cu)*1000≤50.

2. The low-strength, high-formability austenitic stainless steel according to claim 1, characterized in that: The chemical composition content also meets the following requirements: NM=551-462 (C+N)-9.2Si-8.1Mn-29 (Ni+Cu+Sn)-13.7Cr≤-50.

3. A method for manufacturing low-strength and high-formability austenitic stainless steel, characterized in that: The following steps are involved: (1) Melting and forging: The ingredients are prepared and melted according to the formula system designed for the chemical composition of the low-strength, high-formability austenitic stainless steel according to claim 1 or 2, and the ingot is cast in a mold and cooled at a cooling rate of ≥50°C / s. After the ingot is cooled, it is heated in a furnace at a heating temperature of 1100~1250°C and a holding time of 50~150min. After heating, it is forged out of the furnace, with the initial forging temperature not lower than 1150°C and the final forging temperature greater than 900°C. After forging, it is air-cooled; (2) Hot rolling: The forged steel billet is milled to remove the surface oxide scale, and then hot rolled. It is heated at 1080~1250℃ and kept warm for 60~100min before rolling begins. The starting rolling temperature is greater than 1100℃, and the final rolling temperature is controlled at above 850℃. It is water-cooled after rolling. (3) Homogenization annealing: annealing the hot-rolled steel plate at a temperature of 1000-1100°C for 2-10 minutes; (4) Cold rolling: The hot-rolled steel plate after annealing is pickled and surface polished before cold rolling. The total reduction rate of cold rolling is not less than 70%. After cold rolling, bright annealing is performed. The bright annealing temperature is 1000~1100℃, the bright annealing time is 1~10min, the bright annealing speed is controlled at 5~50m / min, and the grain size of the stainless steel plate is controlled at 5~10 levels to obtain a stainless steel product with a bright surface.

4. The method for producing low-strength, high-formability austenitic stainless steel according to claim 3, wherein: The bright annealing in step (4) adopts the existing conventional annealing process, and pickling is performed after conventional annealing to obtain the stainless steel product with a bright surface.

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