Method for preparing high-strength and high-toughness 316l stainless steel by ds warm rolling

Abstract

The application provides a method for preparing high-strength and high-toughness 316L stainless steel through DS warm rolling, and comprises the following steps: step a, hot forging is performed on a 316L steel ingot to obtain a forged 316L steel plate; step b, heating treatment is performed on the forged 316L steel plate; step c, DS rolling is performed on the heated 316L steel plate; step d, steps b and c are repeated for ten to twenty times; and step e, flattening treatment is performed on the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate. The application adopts the DS warm rolling process for rolling, compared with the synchronous warm rolling process, the mechanical properties of the 316L austenitic stainless steel are obviously improved, the yield strength of the 316L austenitic stainless steel at room temperature can reach 845 MPa, and the elongation can reach 22%; the yield strength at the liquid nitrogen temperature of -196 DEG C can reach 1130 MPa, the maximum tensile strength can reach 1712 MPa, and the elongation can reach more than 58%, the mechanical properties are obviously improved, the technical difficulty is low, and the method can be widely used in the fields of low-temperature containers, ships, ocean chemical industry and nuclear industry.

Description

Technical Field

[0001] This invention belongs to the field of 316L austenitic stainless steel preparation technology, specifically relating to a method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling. Background Technology

[0002] With the application and development of clean energy (such as liquefied natural gas and hydrogen energy) and the rapid development of controlled nuclear fusion technology, the demand for cryogenic steel is increasing. At the same time, higher requirements are being placed on the mechanical properties of cryogenic steel at low temperatures. 316L austenitic stainless steel is widely used in industrial fields due to its excellent low-temperature performance, thermal insulation properties, low magnetism, and corrosion resistance, such as cryogenic containers, building materials in extremely cold regions, and cryogenic superconducting armor in controlled nuclear fusion. However, annealed 316L austenitic stainless steel has coarse grains and a very low yield strength, only 200~400 MPa at room temperature, which limits its use in critical load-bearing components.

[0003] According to the Hall-Petch relationship, grain refinement can significantly improve the strength of a material. Typically, high-strength 316L austenitic stainless steel is obtained by introducing significant strain into the alloy through severe plastic deformation (SPD) processes, such as high-pressure torsion and multi-directional forging, thereby refining the grains. However, while SPD strengthens 316L austenitic stainless steel, its plasticity begins to decrease sharply. SPD also introduces a large number of stacking faults and dislocations into the material, promoting martensite formation and causing some austenite to undergo premature martensitic transformation, leading to material embrittlement. Most importantly, in actual production, the SPD process is complex and requires small sample sizes, making it unsuitable for large-scale production.

[0004] Another way to refine grains is through rolling. In traditional synchronous rolling, the shearing force is limited by the rolling force, preventing it from penetrating deep into the core of the sheet, resulting in minimal grain refinement at the center. Asynchronous rolling, by using different speeds for the upper and lower rolls, introduces a pair of shearing forces during the rolling process. These shearing forces penetrate deep into the core of the sheet, significantly refining the central grains and resulting in a more uniform grain distribution. However, asynchronous rolling causes the sheet to bend towards the slower roll, rotating 90° along the rolling direction before rolling. Due to the excessive bending, the sheet cannot be properly gripped. Summary of the Invention

[0005] This invention addresses the technical problems of low strength, uneven grain distribution in the thickness direction, and excessive plate bending in existing processes for preparing 316L austenitic stainless steel. It provides a method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, which can produce larger-sized 316L austenitic stainless steel plates with high efficiency and is suitable for large-scale production.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing high-strength and high-toughness 316 L stainless steel by DS warm rolling, comprising the following steps:

[0007] Step a: Hot forging of 316L steel ingot to obtain forged 316L steel plate;

[0008] Step b: Heat the forged 316L steel plate to a temperature of 500~600℃.

[0009] Step c: Perform DS rolling on the heated 316L steel plate;

[0010] Step d, repeat steps b and c ten to twenty-one times;

[0011] Step e: Level the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate.

[0012] Furthermore, in step a, the initial forging temperature of hot forging is ≥1100 ℃, the final forging temperature is ≥850 ℃, and the holding time is 100~120 min.

[0013] Furthermore, when DS rolling 316L steel plates, the upper work rolls for odd-numbered passes are small-diameter rolls and the lower work rolls are large-diameter rolls, while the upper work rolls for even-numbered passes are large-diameter rolls and the lower work rolls are small-diameter rolls.

[0014] Furthermore, the diameter ratio of the large-diameter roller to the small-diameter roller is k, 1 <k≤1.2。

[0015] Furthermore, in all rolling passes, the 316L steel sheet first comes into contact with the large-diameter rolls.

[0016] Furthermore, the small-diameter rolls and large-diameter work rolls during DS rolling are provided with a horizontal misalignment d in the horizontal direction, with d ranging from 1.5 to 4 mm.

[0017] Furthermore, the horizontal misalignment d is different for each rolling pass, and the ratio d / h of the horizontal misalignment d to the plate thickness h remains constant for each rolling pass.

[0018] Furthermore, during DS rolling of 316L steel plates, after each rolling pass is completed, the 316L steel plate is rotated 180° around the rolling direction before the next rolling pass is performed.

[0019] Furthermore, the reduction in each rolling pass in step c is 3.7% to 7.5%, and the overall reduction after step d is 56% to 95%.

[0020] The beneficial effects of this invention are:

[0021] 1. This invention employs a warm rolling process, in which the grains elongate in the rolling direction, exhibiting fibrous deformation. During warm rolling, dynamic recovery is significant, with some dislocations eliminated through climb and slip, resulting in a lower dislocation density compared to room temperature cold rolling. In contrast, during room temperature cold rolling, dynamic recovery is suppressed, leading to a large accumulation of dislocations in the grains and stress concentration. Furthermore, during room temperature cold rolling, the higher stress and dislocation density induce a partial transformation of austenite to martensite, resulting in a martensitic phase transformation. While this martensitic transformation significantly improves the strength of 316L, it also makes the material brittle, leading to brittle fracture during low-temperature deformation. Warm rolling 316L in its non-recrystallization region effectively avoids strength reduction due to high-temperature recrystallization and prevents excessively high rolling pressure during cold rolling, which could affect normal rolling. This invention, rolling in the non-recrystallization region, prevents recrystallization, effectively refines the grains, reduces residual stress generated during rolling, and improves the overall mechanical properties of the material.

[0022] 2. This invention employs the DS rolling process. Compared to synchronous rolling, the 316L austenitic stainless steel sheet prepared by DS rolling maintains a constant shear angle during the rolling process, thus ensuring a constant shear force applied to the sheet. By increasing the shear force during rolling, a severe plastic deformation effect is achieved, resulting in finer and more uniform grains and better mechanical properties. Due to a certain misalignment between the upper and lower work rolls in DS rolling, the smaller diameter work roll applies a reverse force to the 316L austenitic stainless steel sheet during rolling, thereby reducing the degree of bending. Reverse DS rolling in even-numbered passes, with a constant rolling force, allows for uniform reverse deformation of the sheet, resulting in a straighter sheet shape.

[0023] 3. This invention can produce large-size plates without a complicated annealing process, replacing the manual process of rotating the plate along the rolling direction. It is simple to operate and can be used for large-scale industrial production.

[0024] The present invention will now be described in detail with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of 316L ingot forging;

[0026] Figure 2 This is a schematic diagram of DS rolling;

[0027] Figure 3 This is the stress-strain curve of a steel plate rolled by DS and synchronous rolling at 600℃ at -196℃.

[0028] Figure 4 This is a comparison of the microhardness of DS rolling at 600℃ and synchronous rolling at -196℃;

[0029] Figure 5 It is a comparison diagram of IQ at the center layer of synchronous rolling and DS rolling at a temperature of 600 °C;

[0030] Figure 6 It is an equivalent strain diagram in the thickness direction of DS rolling, unidirectional rolling, rotary rolling, and synchronous rolling;

[0031] Figure 7 It is a comparison diagram of the simulated plate shape of DS rolling, unidirectional rolling, rotary rolling, and synchronous rolling. Specific implementation mode

[0032] The present invention provides a method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, including the following steps.

[0033] Step a, referring to the appendix Figure 1 , hot forging the 316L steel ingot to obtain a forged 316L steel plate. The starting forging temperature of the hot forging is ≥1100 °C, the final forging temperature is ≥850 °C, and the holding time is 100 - 120 min.

[0034] The chemical composition of the 316L austenitic stainless steel used in the present invention includes, by mass percentage: C ≤ 0.03, Si ≤ 1.0, Mn ≤ 2.0, S ≤ 0.03, P ≤ 0.045, Ni ≤ 10.0 - 14.0, Cr ≤ 16.0 - 18.0, Mo ≤ 2.0 - 3.0, and the rest is Fe and inevitable impurities.

[0035] Referring to the appendix Figure 2 , step b, heat-treating the forged 316L steel plate, and the temperature of the steel plate after heating is 500 - 600 °C.

[0036] Step c, performing DS rolling on the heated 316L steel plate.

[0037] Step d, repeating steps b and c ten to twenty-one times. The specific number of repetitions in this step can be determined according to the final plate thickness and the reduction per pass.

[0038] When performing multiple DS rollings on the 316L steel plate, the upper working roll for odd-numbered passes is a small-diameter roll, and the lower working roll is a large-diameter roll; the upper working roll for even-numbered passes is a large-diameter roll, and the lower working roll is a small-diameter roll. The diameter ratio of the large-diameter roll to the small-diameter roll is k, 1 < k ≤ 1.2, so that when the shear angle θ is constant within the range of 1 < k ≤ 1.2, the shear force during the rolling process is the largest. During the rolling process of all passes, the 316L steel plate first contacts the large-diameter roll. After each pass of rolling, the 316L steel plate is rotated 180° around the rolling direction and then the next pass of rolling is performed.

[0039] In DS rolling, the small-diameter rolls and large-diameter work rolls have a horizontal misalignment d, ranging from 1.5 to 4 mm. The value of the horizontal misalignment d is different for each rolling pass, and the ratio d / h of the horizontal misalignment d to the plate thickness h remains constant across all passes. The specific value of the horizontal misalignment d is determined by h*tanθ. When k is constant, the shear force is maximum and the strength is highest during rolling when the shear angle θ is in the range of 9~12°.

[0040] In step c, the reduction per pass is 3.7% to 7.5%, and after step d, the overall reduction is 56% to 95%. Too much reduction per pass can cause cracks in the sheet and requires higher mill reduction force, while too little reduction makes it difficult to roll through the sheet, and the rolling force cannot penetrate to the core, resulting in a decrease in strength. Therefore, a reduction of 3.7% to 7.5% per pass is chosen.

[0041] Step e: Level the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate.

[0042] The present invention will be described in detail below with reference to specific embodiments.

[0043] Example 1: In this example, three forged 316L austenitic stainless steel plates were placed in electric furnaces at temperatures of 500℃, 550℃, and 600℃ respectively and heated to the corresponding temperatures.

[0044] Three 316L austenitic stainless steel plates were simultaneously rolled, with a reduction of 3.7% to 7.5% per pass, for a total of 12 passes. The final rolled thickness was 12 mm for each plate, with a total reduction of 56%. After each pass, the three 316L austenitic stainless steel plates were heated in a furnace to the previous heating temperature, ensuring that the rolling temperatures for 316L were 500℃, 550℃, and 600℃ respectively. After simultaneous warm rolling, the plates were leveled using a leveling device.

[0045] Table 1 Heating and rolling parameters for Example 1

[0046] .

[0047] Taking a 316L austenitic stainless steel plate heated to 600℃ as an example, the engineering stress-strain curve, Vickers hardness distribution, and central layer IQ diagram of the 316L austenitic stainless steel plate obtained by the above method in this example are shown below. Figure 3 , Figure 4 , Figure 5(The left side of the figure shows the IQ diagram of the synchronously rolled center layer, and the right side shows the IQ diagram of the DS rolled center layer.) As shown, the yield strength at -196℃ is 937.88MPa, the tensile strength is 1564MPa, the elongation at break is 61.2%, and the hardness is 325HV.

[0048] Example 2: In this example, the chemical composition percentage of 316L austenitic stainless steel includes: C≤0.03, Si≤1.0, Mn≤2.0, S≤0.03, P≤0.045, Ni≤10.0~14.0, Cr≤16.0~18.0, Mo≤2.0~3.0, with the remainder being Fe and unavoidable impurities.

[0049] The 316L austenitic stainless steel ingot is forged. The initial forging temperature is ≥1100℃, the final forging temperature is controlled at ≥850℃, the holding time is 120 min, and the thickness after forging is 27 mm.

[0050] Three forged 316L austenitic stainless steel plates were placed in electric furnaces at temperatures of 500 ℃, 550 ℃, and 600 ℃ respectively and heated to the corresponding temperatures.

[0051] The DS rolling mill has an upper work roll diameter of 180 mm and a lower work roll diameter of 216 mm. The initial dislocation d0 of the upper and lower rolls is 4 mm, at which point the shear force is at its maximum and the shear angle is 9°.

[0052] Three 316L austenitic stainless steel plates were subjected to DS rolling. The reduction per pass in DS rolling was 3.7~7.5%, and a total of 12 passes were rolled, resulting in a final thickness of 12 mm.

[0053] After each rolling pass, the specific value of d is calculated based on d / h=tan9°, and the misalignment is adjusted accordingly. Three 316L austenitic stainless steel plates are placed in the furnace and heated to the temperature of the previous heating, ensuring that the rolling temperatures of the 316L steel plates are 500℃, 550℃, and 600℃ respectively. After heating, the 316L austenitic stainless steel plates are rotated 180° around the rolling direction as the axis for the next rolling pass.

[0054] In this embodiment, the overall reduction is 56%, and the final leveling is performed using a leveling device.

[0055] Table 2 Heating and rolling parameters for Example 2

[0056] .

[0057] Taking 316L austenitic stainless steel plates heated to 600℃ as an example, the engineering stress-strain curves, microhardness distribution, and central layer IQ diagrams of the 316L austenitic stainless steel plates obtained by the above method are shown below. Figure 3 , Figure 4 , Figure 5 As shown, the yield strength at -196℃ is 1125.6 MPa, the tensile strength is 1710.8 MPa, the elongation at break is 58.8%, and the hardness is 332 HV. The engineering stress-strain curves show that the steel plate rolled by DS exhibits significantly improved strength and hardness compared to synchronously rolled steel, while the elongation decreases by only 3.9%.

[0058] Example 3: This example involves a second DS rolling of the 316L austenitic stainless steel sheet obtained in Example 2. Three 316L austenitic stainless steel sheets with a thickness of 12 mm after DS rolling in Example 2 were placed in electric furnaces at temperatures of 500 ℃, 550 ℃, and 600 ℃ respectively and heated to the corresponding temperatures (the heating temperature of the three 316L austenitic stainless steel sheets is consistent with the rolling temperature in Example 2; for example, if the heating temperature in Example 2 was 500 ℃, it remains 500 ℃ in this example).

[0059] The DS rolling mill has an upper work roll diameter of 180 mm and a lower work roll diameter of 216 mm. The initial dislocation d0 of the upper and lower rolls is 1.7 mm, at which point the shear force is at its maximum and the shear angle is 9°.

[0060] 316L stainless steel sheet was subjected to DS rolling. The reduction per pass of DS rolling was 3.7~7.5%, and a total of 5 passes were rolled to achieve a final thickness of 6 mm.

[0061] After each rolling pass, the specific value of d is calculated based on d / h=tan9°, and the misalignment is adjusted accordingly. Three 316L austenitic stainless steel plates are placed in the furnace and heated to the previous heating temperature, ensuring the rolling temperatures of the 316L austenitic stainless steel are 500℃, 550℃, and 600℃, respectively. After holding at these temperatures, the 316L steel plates are rotated 180° around the rolling direction for the next rolling pass.

[0062] The overall reduction was 78%, and finally leveling was performed using a leveling device.

[0063] Table 3 Heating and rolling parameters for Example 3

[0064] .

[0065] Taking 316L austenitic stainless steel plates heated to 600℃ as an example, the engineering stress-strain curve of the 316L austenitic stainless steel plates obtained after re-rolling is as follows: Figure 3As shown, the yield strength at -196 ℃ is 1210 MPa, the tensile strength is 1762 MPa, and the elongation at break is 51.3%. The engineering stress-strain curves demonstrate that DS-rolled steel plates exhibit good strength-plasticity matching at low temperatures.

[0066] Example 4: This example describes a second DS rolling of the 316L austenitic stainless steel sheet obtained in Example 3. Three 6 mm thick 316L austenitic stainless steel sheets from Example 3 were placed in electric furnaces at temperatures of 500 °C, 550 °C, and 600 °C, respectively, and heated to the corresponding temperatures (the heating temperature of the three 316L austenitic stainless steel sheets is consistent with the rolling temperature in Example 3; for example, if the heating temperature in Example 2 was 500 °C, it remains 500 °C in this example).

[0067] The DS rolling mill has an upper work roll diameter of 180 mm and a lower work roll diameter of 216 mm. The initial dislocation d0 of the upper and lower rolls is 1 mm, at which point the shear force is at its maximum and the shear angle is 9°.

[0068] 316L austenitic stainless steel plates were subjected to DS rolling. The reduction per pass in DS rolling was 3.7~7.5%, and a total of 4 passes were rolled, resulting in a final thickness of 1.3 mm.

[0069] After each rolling pass, the specific value of d is calculated based on d / h=tan9°, and the misalignment is adjusted accordingly. Three 316L austenitic stainless steel plates are placed in the furnace and heated to the temperature of the previous heating, ensuring that the rolling temperatures of the 316L austenitic stainless steel are 500 ℃, 550 ℃, and 600 ℃ respectively. After holding at these temperatures, the 316L austenitic stainless steel plates are rotated 180° around the rolling direction for the next rolling pass. The overall reduction is 95%, and finally, the plates are leveled using a leveling device.

[0070] Table 4 Heating and rolling parameters for Example 4

[0071] .

[0072] Taking 316L austenitic stainless steel plates heated to 600℃ as an example, the engineering stress-strain curve of the 316L austenitic stainless steel plates obtained after re-rolling is as follows: Figure 3 As shown, the yield strength at -196 ℃ is 1540 MPa, the tensile strength is 1891 MPa, and the elongation at break is 43%. The engineering stress-strain curves demonstrate that DS-rolled steel plates exhibit good strength-plasticity matching at low temperatures.

[0073] Example 5: In this example, DEFORM-3D software was used to simulate 10 passes of DS unidirectional rolling, DS rotary rolling, and synchronous rolling, with a total reduction of 56%.

[0074] In the DS unidirectional rolling mill, the upper work roll diameter is 180 mm and the lower work roll diameter is 216 mm. The initial dislocation d0 of the upper and lower rolls is 1 mm, at which point the shear force is at its maximum, the shear angle is 9°, and the roll speed is 0.604 rad / s. After each rolling pass, the specific value of d is calculated based on d / h=tan9°, and the dislocation is adjusted accordingly.

[0075] In the DS rotary rolling mill, the upper work roll diameter is 180 mm, and the lower work roll diameter is 216 mm. The initial dislocation d0 of the upper and lower rolls is 1 mm, at which point the shear force is at its maximum, the shear angle is 9°, and the roll speed is 0.604 rad / s. After each rolling pass, the specific value of d is calculated based on d / h = tan9°, and the dislocation is adjusted accordingly. The 316L austenitic stainless steel sheet is rotated 180° around the rolling direction as the axis for the next rolling pass.

[0076] Synchronous rolling is used, with the upper and lower work rolls having a diameter of 180 mm and a roll rotation speed of 0.604 rad / s.

[0077] The equivalent strain diagram in the thickness direction of 316L austenitic stainless steel was obtained using the above method, as shown in the attached figure. Figure 6 As shown, the equivalent strain distribution of DS rolling is more uniform, and its grain refinement effect on the central grains is more significant. (See attached image.) Figure 7 As shown, the DS rolling rotary rolling produces a good plate shape, which is closer to that of synchronous rolling.

[0078] The materials from Examples 1 and 2 above were subjected to room temperature (RT) and liquid nitrogen temperature (LNT) tensile and impact tests, and the test results are shown in Table 5 below:

[0079] Table 5 Relevant Properties of DS-Warm Rolling and Synchronous Warm Rolling

[0080] .

[0081] Actual measurements showed that at room temperature (RT), DS rolling increased the yield strength by 5% compared to synchronous rolling, reaching 834.2 MPa; the tensile strength increased by 4%, reaching 850.9 MPa; and the elongation at break decreased by 10%.

[0082] At low temperature (LNT), DS rolling increased the yield strength by 20% compared to synchronous rolling, reaching 1125.6 MPa; the rolling tensile strength increased by 9%, reaching 1710.8 MPa; and the elongation at break decreased by 3.9%.

[0083] The materials from Examples 1 and 2 were subjected to tensile and impact tests at room temperature and -196 °C. The test results are compared with the processing data of 316L in the literature, as shown in Table 6 below:

[0084] Table 6 Comparison of relevant properties of DS warm-rolled steel and 316L (reference 316L)

[0085] .

[0086] Note: [1] Nam, Y.-H., Park, J.-S., Baek, U.-B., Suh, J.-Y., etal. Low-temperature tensile and impact properties of hydrogen-charged high-manganesesteel. Int. J. Hydrogen Energy, 2019, 44(13): 7000-7013.

[0087] [2] Wang XL, Sanchez-Mata O, Atabay SE, et al. Crystallographic orientation dependence of Charpy impact behaviors instainless steel 316L fabricated by laser powder bed fusion. Additivemanufacturing, 2021,46: 102104.

[0088] The materials from Examples 1 and 2 above were subjected to tensile and impact tests at room temperature and -196 °C. The test results are compared with data from other steel materials in the literature, as shown in Table 7 below:

[0089] Table 7 Comparison of relevant properties of DS-rolled and literature-based low-temperature steel materials

[0090] .

[0091] Note: [3] Wang YH, Zhang YB, Godfrey A, et al. Cryogenictoughness in low-cost austenitic steel.

[0092] Communications Materials, 2021, 2(1): 44.

[0093] [4] SOHN S S, HONG S, LEE J, et al. Effects of Mn and Al contentsoncryogenic-temperature tensile

[0094] and Charpy impact properties in four austenitic high-Mn steels. ActaMaterialia, 2015, 100: 39-52.

[0095] [5] OTTO F, DLOUHÝ A, SOMSEN C, et al. The influences of temperatureandmicrostructure on the tensile properties of a CoCrFeMnNi high-entropyalloy. Acta Materialia, 2013, 61 (15): 5743-5755.

[0096] [6] LEE Y K, CHOI C. Driving force for γ→εmartensitictransformation and stacking fault energy ofγ in Fe-Mn binary system.Metallurgical and Materials Transactions A, 2000, 31 (2): 355-360.

[0097] [7] CHEN S, RANA R, HALDAR A, et al. Current state of Fe-Mn-Al-Clowdensity steels. Progress in Materials Science, 2017, 89: 345-391.

[0098] [8] WANG XJ, SUN XJ, SONG C, et al. Enhancement of yield strength by chromium / nitrogen alloying in high-manganese cryogenic steel. MaterialsScience and Engineering: A, 2017, 698: 110-116.

[0099] [9] CHEN J, REN J, LIU Z. Deformation microstructures as wellasstrengthening and toughening mechanisms of low-density high Mn steels for cryogenic applications. Journal of Materials Research and Technology, 2021,13:947-961.

[0100] Tables 6 and 7 show the relationship between low-temperature impact and room-temperature yield strength for different materials and processing methods. It can be seen that the DS-rolled 316L austenitic stainless steel achieves a good balance between strength and plasticity, exhibiting excellent mechanical properties. Therefore, the DS warm rolling process proposed in this invention can prepare 316L austenitic stainless steel with high strength and high toughness.

[0101] As can be seen, the invention uses the DS warm rolling process, which significantly improves the mechanical properties of 316L austenitic stainless steel compared to the synchronous warm rolling process. Its yield strength at room temperature can reach 845 MPa, and its elongation can reach 22%. At liquid nitrogen temperature of -196℃, the yield strength reaches 1130 MPa, the maximum tensile strength reaches 1712 MPa, and the elongation can reach more than 58%. Its mechanical properties are significantly improved, and the technology is less difficult to master. It can be widely used in the manufacture of cryogenic containers, ships, marine chemical industry and nuclear industry.

[0102] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.

Claims

1. A method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, characterized in that, Includes the following steps: Step a: Hot forging of 316L steel ingot to obtain forged 316L steel plate; Step b: Heat the forged 316L steel plate to a temperature of 500~600 ℃. Step c: Perform DS rolling on the heated 316L steel plate; Step d, repeat steps b and c ten to twenty-one times; Step e: Level the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate. When DS rolling 316L steel plate, the upper work roll is a small diameter roll and the lower work roll is a large diameter roll in odd-numbered rolling passes, and the upper work roll is a large diameter roll and the lower work roll is a small diameter roll in even-numbered rolling passes. In all rolling passes, the 316L steel sheet first comes into contact with the large-diameter rolls.

2. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 1, characterized in that, In step a, the initial forging temperature of hot forging is ≥1100 ℃, the final forging temperature is ≥850 ℃, and the holding time is 100~120 min.

3. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 1, characterized in that, The diameter ratio of the large-diameter roller to the small-diameter roller is k, 1 <k≤1.2。 4. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 1, characterized in that, In DS rolling, the small-diameter rolls and large-diameter work rolls are provided with a horizontal misalignment d in the horizontal direction, and the range of d is 1.5~4 mm.

5. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 4, characterized in that, The horizontal misalignment d is different for each rolling pass, and the ratio d / h of the horizontal misalignment d to the plate thickness h remains constant for each rolling pass.

6. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 1, characterized in that, When performing DS rolling on 316L steel plates, after each rolling pass is completed, the 316L steel plate is rotated 180° around the rolling direction before proceeding to the next rolling pass.

7. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to any one of claims 1-6, characterized in that, In step c, the reduction in each rolling pass is 3.7% to 7.5%, and after step d, the overall reduction is 56% to 95%.

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