Method for preparing high-strength and high-toughness 316L stainless steel through DS warm rolling

Abstract

The invention provides a method for preparing high-strength and high-toughness 316L stainless steel through DS warm rolling, which comprises the following steps: step a, carrying out hot forging on a 316L steel ingot to obtain a forged 316L steel plate; b, the 316L steel plate in the forging state is subjected to heating treatment; c, the heated 316L steel plate is subjected to DS rolling; step d, repeating the step b and the step c for ten to twenty-first times; and e, the 316L steel plate is subjected to leveling treatment, and the high-strength and high-toughness 316L austenitic stainless steel plate is obtained. The DS warm rolling process is adopted for rolling, and compared with a synchronous warm rolling process, the mechanical performance of the 316L austenitic stainless steel is obviously improved, the yield strength of the 316L austenitic stainless steel at the room temperature can reach 845 MPa, and the ductility of the 316L austenitic stainless steel at the room temperature can reach 22%; the tensile strength of the steel plate reaches 1130 MPa at the liquid nitrogen temperature of-196 DEG C, the maximum tensile strength reaches 1712 MPa, the ductility can reach 58% or above, the mechanical property of the steel plate is obviously improved, the technical difficulty is low, and the steel plate can be widely applied to the fields of manufacturing of low-temperature containers, ships, ocean chemical engineering and nuclear industry.

Description

Technical Field

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

[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 low-temperature steel is increasing. At the same time, higher requirements are placed on the mechanical properties of low-temperature steel at low temperatures. 316L austenitic stainless steel is widely used in industrial fields due to its excellent low-temperature performance, thermal insulation performance, low magnetism and corrosion resistance, such as cryogenic containers, building materials in cold areas, and low-temperature superconducting armor in controlled nuclear fusion. However, the annealed 316L austenitic stainless steel has coarse grains and a very low yield strength of only 200~400 MPa at room temperature, which limits its use in key load-bearing components.

[0003] According to the Hall-Petch relationship, grain refinement can significantly improve the strength of the material. Usually, a large amount of strain is introduced into the alloy through severe plastic deformation (SPD) processes, such as high-pressure torsion and multi-directional forging, to achieve grain refinement and obtain high-strength 316L austenitic stainless steel. However, while the SPD process strengthens 316L austenitic stainless steel, its plasticity begins to drop sharply. The SPD process also introduces a large number of stacking faults and dislocation accumulations into the material, promotes the formation of martensite, and causes part of the austenite to undergo martensitic phase transformation prematurely, thereby causing material embrittlement. The most important thing is that the SPD process is complex in actual production and the sample size is small, so it cannot be used for large-scale production.

[0004] Another way to refine grains is rolling. In the traditional synchronous rolling process, synchronous rolling is limited by its rolling force, and the shear force cannot penetrate into the core of the plate, so the refinement effect on the center of the plate is not obvious. Through asynchronous rolling, the upper and lower rollers have different speeds, so a pair of shear forces are introduced during the rolling process, so that the shear force penetrates into the core of the plate, which has a significant refinement effect on the central grains and makes the grain distribution of the plate more uniform. However, asynchronous rolling will cause the plate to bend toward the slow roller side, and rolling will be carried out after rotating 90° in the rolling direction. Due to the excessive bending of the plate, it cannot be smoothly bitten into the plate. Summary of the invention

[0005] Aiming at the technical problems of low strength, uneven grain distribution in the thickness direction, and excessive plate bending in the existing process for preparing 316L austenitic stainless steel, the present invention 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] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, comprising the following steps: Step a, hot forging the 316L steel ingot to obtain a forged 316L steel plate; Step b, heating the forged 316L steel plate, wherein the temperature of the steel plate after heating is 500-600° C.; Step c, performing DS rolling on the heated 316L steel plate; Step d, repeat steps b and c ten to twenty-one times; Step e: leveling the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate.

[0007] Furthermore, in step a, the initial forging temperature of hot forging is ≥1100°C, the final forging temperature is ≥850°C, and the holding time is 100-120 min.

[0008] Furthermore, when DS rolling is performed on 316L steel plates, the upper working roll for odd-numbered rolling passes is a small-diameter roll and the lower working roll is a large-diameter roll, and the upper working roll for even-numbered rolling passes is a large-diameter roll and the lower working roll is a small-diameter roll.

[0009] Furthermore, the diameter ratio of the large diameter roller to the small diameter roller is k, 1 <k≤1.2。

[0010] Furthermore, in all rolling passes, the 316L steel plate first contacts the large diameter roll.

[0011] Furthermore, during DS rolling, the small diameter roll and the large diameter working roll are provided with a horizontal offset d in the horizontal direction, and the range of d is 1.5~4 mm.

[0012] Furthermore, the horizontal misalignment d of each rolling pass has different values ​​and the ratio d / h of the horizontal misalignment d of each rolling pass to the plate thickness h is constant.

[0013] Furthermore, when DS rolling is performed on the 316L steel plate, after each rolling pass, the 316L steel plate is rotated 180° with the rolling direction as the axis before the next rolling pass.

[0014] Furthermore, the reduction in each rolling pass in step c is 3.7% to 7.5%, and the overall reduction after step d is completed is 56% to 95%.

[0015] The beneficial effects of the present invention are: 1. The present invention adopts a warm rolling preparation process, and the grains of the warm rolling process are elongated in the rolling direction, showing fibrous deformation. During the warm rolling process, dynamic recovery is significant, and some dislocations are eliminated by climbing and slipping, and the dislocation density is lower than that of cold rolling at room temperature; while during cold rolling at room temperature, dynamic recovery is suppressed, and a large number of dislocations accumulate in the grains, resulting in stress concentration. In addition, during the cold rolling process at room temperature, the larger stress and dislocation density will induce part of the austenite to transform into martensite, resulting in a martensitic phase transformation. The production of martensitic phase transformation will significantly increase the strength of 316L, but at the same time it will make the material brittle and cause brittle fracture during low-temperature deformation. Warm rolling 316L in its non-recrystallization zone can effectively avoid the reduction of strength caused by high-temperature recrystallization on the one hand, and on the other hand it can avoid the rolling pressure being too high during cold rolling, thereby affecting normal rolling. The present invention is rolled in the non-recrystallization zone, and no recrystallization occurs, which can effectively refine the grains, reduce the residual stress generated by rolling, and improve the comprehensive mechanical properties of the material.

[0016] 2. The present invention adopts the DS rolling process. Compared with synchronous rolling, the 316L austenitic stainless steel plate prepared by DS rolling can ensure a constant shear angle during the rolling process, so the shear force applied to the plate remains unchanged. By increasing the shear force during the rolling process, the effect of severe plastic deformation is achieved, and more refined and uniform grains are obtained, so that the plate has better mechanical properties. Since there is a certain amount of misalignment between the upper and lower working rolls of DS rolling, during the rolling process, the small-diameter working roll applies a reverse force to the 316L austenitic stainless steel plate, thereby reducing the degree of bending of the plate. Reverse DS rolling is performed in an even number of passes. Since the rolling force is constant, the plate can produce uniform reverse deformation and obtain a flatter plate shape.

[0017] 3. The present invention can produce large-size plates without complicated annealing process, replaces the process of manually rotating the plates along the rolling direction, is simple to operate, and can be used for large-scale industrial production.

[0018] The present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of 316L ingot forging; Figure 2 It is a schematic diagram of DS rolling; Figure 3 It is the engineering stress-strain curve of the steel plate after DS rolling and synchronous rolling at 600℃ at -196℃; Figure 4 It is a comparison chart of microhardness of DS rolling at 600℃ and synchronous rolling at -196℃; Figure 5It is a comparison diagram of IQ at the center layer during synchronous rolling and DS rolling at a temperature of 600°C; Figure 6 It is an equivalent strain diagram in the thickness direction of DS rolling, unidirectional rolling, rotary rolling, and synchronous rolling; Figure 7 It is a comparison diagram of the simulated plate shape of DS rolling, unidirectional rolling, rotary rolling, and synchronous rolling. Specific implementation manner

[0020] The present invention provides a method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, including the following steps.

[0021] 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.

[0022] 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.

[0023] Referring to the appendix Figure 2 , step b, heating the forged 316L steel plate, and the temperature of the steel plate after heating is 500 - 600°C.

[0024] Step c, performing DS rolling on the heated 316L steel plate.

[0025] 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.

[0026] 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.

[0027] During DS rolling, the small-diameter roll and the large-diameter work roll are provided with a horizontal misalignment d in the horizontal direction, and the range of d is 1.5~4 mm. The value of the horizontal misalignment d in each rolling pass is different, and the ratio d / h of the horizontal misalignment d in each rolling pass to the plate thickness h is constant. The specific value of the horizontal misalignment d is determined by h*tanθ. When k is constant, when the shear angle θ is in the range of 9~12°, the shear force is the largest and the strength is the highest during rolling.

[0028] The reduction in each rolling pass in step c is 3.7-7.5%, and the overall reduction after step d is 56-95%. Too much reduction in each pass will cause cracks in the plate and require a higher rolling force, while too little reduction will make it difficult for the rolled plate to be rolled through, and the rolling force will have difficulty penetrating into the core, resulting in a decrease in strength. Therefore, the reduction in each pass is selected to be 3.7-7.5%.

[0029] Step e: leveling the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate.

[0030] The present invention is described in detail below with reference to specific embodiments.

[0031] Embodiment 1: In this embodiment: three forged 316L austenitic stainless steel plates are placed in an electric furnace at temperatures of 500° C., 550° C., and 600° C., respectively, and heated to corresponding temperatures.

[0032] Three 316L austenitic stainless steel plates were rolled synchronously, with a reduction of 3.7-7.5% per pass, a total of 12 passes, and a final thickness of 12 mm after rolling, with a total reduction of 56%. After each pass of rolling, the three 316L austenitic stainless steel plates were placed in a furnace and heated to the last heating temperature, ensuring that the rolling temperatures of 316L were 500°C, 550°C, and 600°C, respectively. After synchronous warm rolling, the plates were leveled using a leveling device.

[0033] Table 1 Heating and rolling parameters of Example 1 .

[0034] Taking the 316L austenitic stainless steel plate heated at 600°C as an example, the engineering stress-strain curve, Vickers hardness distribution and center layer IQ diagram of the 316L austenitic stainless steel plate obtained by the above method in this example are as follows: Figure 3 , Figure 4 , Figure 5 (The left figure in the figure is the IQ diagram of the synchronous rolling center layer, and the right figure is the IQ diagram of the DS rolling center layer) As shown, the yield strength at -196°C is 937.88MPa, the tensile strength is 1564MPa, the elongation at break is 61.2%, and the hardness is 325HV.

[0035] Embodiment 2. In this embodiment, 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, and the rest is Fe and unavoidable impurities.

[0036] The 316L austenitic stainless steel ingot was forged. The initial forging temperature of the forging heat treatment was ≥1100℃, the final forging temperature was controlled to be ≥850℃, the holding time was 120 min, and the thickness after forging was 27 mm.

[0037] Three forged 316L austenitic stainless steel plates were placed in an electric furnace at 500 ℃, 550 ℃, and 600 ℃ and heated to the corresponding temperatures.

[0038] The diameter of the upper working roll in DS rolling is 180 mm, the diameter of the lower working roll is 216 mm, and the initial misalignment d0 of the upper and lower rolls is 4 mm. At this time, the shear force is the largest and the shear angle is 9°.

[0039] Three 316L austenitic stainless steel plates were subjected to DS rolling, with a reduction of 3.7-7.5% per pass, a total of 12 passes, and a final thickness of 12 mm.

[0040] After each rolling, the specific value of d is calculated according to d / h=tan9°, and the misalignment is adjusted. Three 316L austenitic stainless steel plates are placed in a furnace and heated to the temperature of the last heating, ensuring that the rolling temperatures of the 316L steel plates are 500°C, 550°C, and 600°C, respectively. After heating, the 316L austenitic stainless steel plates are rotated 180° around the rolling direction for the next rolling.

[0041] In this embodiment, the overall pressing amount is 56%, and finally leveling is performed by a leveling device.

[0042] Table 2 Heating and rolling parameters of Example 2 .

[0043] Taking the 316L austenitic stainless steel plate with a heating temperature of 600°C as an example, the engineering stress-strain curve, microhardness distribution and center layer IQ diagram of the 316L austenitic stainless steel plate obtained by the above method are shown in Figure 3 , Figure 4 , Figure 5As shown in the figure, the yield strength at -196°C is 1125.6 MPa, the tensile strength is 1710.8 MPa, the elongation at break is 58.8%, and the hardness is 332 HV. It can be seen from the engineering stress-strain curve that the strength and hardness of the steel plate rolled by DS are significantly improved compared with those rolled by synchronous rolling, and the elongation is only reduced by 3.9%.

[0044] Example 3: This embodiment is a re-DS rolling of the 316L austenitic stainless steel plate obtained in Example 2. Three 316L austenitic stainless steel plates with a thickness of 12 mm after DS rolling in Example 2 were placed in an electric furnace at temperatures of 500°C, 550°C, and 600°C, respectively, and heated to the corresponding temperatures (the heating temperatures of the three 316L austenitic stainless steel plates are consistent with the temperatures during rolling in Example 2, such as the heating temperature in Example 2 is 500°C, and it is still 500°C in this embodiment).

[0045] The diameter of the upper working roll in DS rolling is 180 mm, the diameter of the lower working roll is 216 mm, and the initial misalignment d0 of the upper and lower rolls is 1.7 mm. At this time, the shear force is the largest and the shear angle is 9°.

[0046] DS rolling was performed on the 316L stainless steel plate. The reduction of each DS rolling pass was 3.7-7.5%, and there were 5 rolling passes in total. The final thickness after rolling was 6 mm.

[0047] After each rolling, the specific value of d is calculated according to d / h=tan9°, and the misalignment is adjusted. Three 316L austenitic stainless steel plates are placed in a furnace and heated to the last heating temperature, ensuring that the rolling temperatures of 316L austenitic stainless steel are 500°C, 550°C, and 600°C. After heat preservation, the 316L steel plate is rotated 180° with the rolling direction as the axis for the next rolling.

[0048] The overall reduction is 78%, and finally it is leveled by a leveling device.

[0049] Table 3 Heating and rolling parameters of Example 3 .

[0050] Taking the 316L austenitic stainless steel plate with a heating temperature of 600°C as an example, the engineering stress-strain curve of the 316L austenitic stainless steel plate obtained after rolling again is as follows: Figure 3 As shown in the figure, the yield strength at -196 ℃ is 1210 MPa, the tensile strength is 1762 MPa, and the elongation at break is 51.3%. It can be seen from the engineering stress-strain curve that the DS rolled steel plate has a good strength-plasticity match at low temperature.

[0051] Example 4: This example is a re-DS rolling of the 316L austenitic stainless steel plate obtained in Example 3. The three 6 mm 316L austenitic stainless steel plates after DS rolling in Example 3 were placed in an electric furnace at temperatures of 500°C, 550°C, and 600°C, respectively, and heated to the corresponding temperatures (the heating temperatures of the three 316L austenitic stainless steel plates were consistent with the temperatures during rolling in Example 3, such as the heating temperature of 500°C in Example 2, and it was still 500°C in this example).

[0052] The diameter of the upper working roll in DS rolling is 180 mm, the diameter of the lower working roll is 216 mm, and the initial misalignment d0 of the upper and lower rolls is 1 mm. At this time, the shear force is maximum and the shear angle is 9°.

[0053] DS rolling was performed on the 316L austenitic stainless steel plate. The reduction of each DS rolling pass was 3.7-7.5%, and a total of 4 rolling passes were performed. The final thickness after rolling was 1.3 mm.

[0054] After each rolling, the specific value of d is calculated according to d / h=tan9°, and the misalignment is adjusted. Three 316L austenitic stainless steel plates are placed in a furnace and heated to the temperature of the last heating, ensuring that the rolling temperatures of 316L austenitic stainless steel are 500°, 550°, and 600°, respectively. After the insulation is completed, the 316L austenitic stainless steel plate is rotated 180° with the rolling direction as the axis for the next rolling. The overall reduction is 95%, and finally leveled by a leveling device.

[0055] Table 4 Heating and rolling parameters of Example 4 .

[0056] Taking the 316L austenitic stainless steel plate with a heating temperature of 600°C as an example, the engineering stress-strain curve of the 316L austenitic stainless steel plate obtained after rolling again is as follows: Figure 3 As shown in the figure, the yield strength at -196 ℃ is 1540 MPa, the tensile strength is 1891 MPa, and the elongation at break is 43%. It can be seen from the engineering stress-strain curve that the DS rolled steel plate has a good strength-plasticity match at low temperature.

[0057] Example 5. In this example, DEFORM-3D software was used to simulate DS unidirectional rolling, DS rotary rolling, and synchronous rolling for 10 passes with a total reduction of 56%.

[0058] The diameter of the upper working roll of DS unidirectional rolling is 180 mm, the diameter of the lower working roll is 216 mm, and the initial misalignment d0 of the upper and lower rolls is 1 mm. At this time, the shear force is the largest, 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 according to d / h=tan9°, and the misalignment is adjusted.

[0059] The diameter of the upper working roll of DS rotary rolling is 180 mm, the diameter of the lower working roll is 216 mm, and the initial misalignment d0 of the upper and lower rolls is 1 mm. At this time, the shear force is maximum, the shear angle is 9°, and the roll speed is 0.604 rad / s. After each rolling, the specific value of d is calculated according to d / h=tan9°, and the misalignment is adjusted. The 316L austenitic stainless steel plate is rotated 180° with the rolling direction as the axis for the next rolling.

[0060] Synchronous rolling, the diameter of the upper and lower working rolls is 180 mm, and the roll speed is 0.604 rad / s.

[0061] The equivalent strain diagram of the thickness direction of 316L austenitic stainless steel was obtained by the above method, as shown in the attached figure. Figure 6 As shown in the figure, the equivalent strain distribution of DS rolling and rotary rolling is more uniform, and the refinement effect on the central grain is more obvious. Figure 7 As shown, the plate shape of DS rolling and rotary rolling is good and closer to the plate shape of synchronous rolling.

[0062] The materials of Examples 1 and 2 were subjected to room temperature (RT) and liquid nitrogen temperature (LNT) tensile and impact tests. The test results are shown in Table 5 below: Table 5 Related properties of DS warm rolling and synchronous warm rolling .

[0063] According to actual measurements, at room temperature (RT), the yield strength of DS rolling increased by 5% to 834.2MPa, the tensile strength increased by 4% to 850.9MPa, and the elongation at break decreased by 10% compared with synchronous rolling.

[0064] At low temperature (LNT), DS rolling increased the yield strength by 20% compared with synchronous rolling, reaching 1125.6 MPa; the rolled tensile strength increased by 9% to 1710.8 MPa; and the elongation at break decreased by 3.9%.

[0065] The materials of the above-mentioned Examples 1 and 2 were subjected to tensile and impact tests at room temperature and -196°C. The test results were compared with the 316L processing data in the literature as shown in Table 6 below: Table 6 Comparison of relevant properties of DS warm rolling and 316L in the literature .

[0066] 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. [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.

[0067] The materials of the above-mentioned Examples 1 and 2 were subjected to tensile and impact tests at room temperature and -196°C. The test results were compared with the data of other steel materials in the literature as shown in Table 7 below: Table 7 Comparison of relevant properties of DS warm rolled and low temperature steel materials in the literature .

[0068] Note: [3] Wang YH, Zhang YB, Godfrey A, et al. Cryogenictoughness in low-cost austenitic steel. Communications Materials, 2021, 2(1): 44. [4] SOHN SS, HONG S, LEE J, et al. Effects of Mn and Al contentsoncryogenic-temperature tensile and Charpy impact properties in four austenitic high-Mn steels. ActaMaterialia, 2015, 100: 39-52. [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. [6] LEE Y K, CHOI C. Driving force for γ→εmartensitic transformationand stacking fault energy ofγ in Fe-Mn binary system. Metallurgical andMaterials Transactions A, 2000, 31 (2): 355-360. [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. [8] WANG X J, SUN X J, SONG C, et al. Enhancement of yield strengthbychromium / nitrogen alloying in high-manganese cryogenic steel. MaterialsScience and Engineering: A, 2017, 698: 110-116. [9] CHEN J, REN J, LIU Z. Deformation microstructures as wellasstrengthening and toughening mechanisms of low-density high Mn steels forcryogenic applications. Journal of Materials Research and Technology, 2021,13:947-961。

[0069] Tables 6 and 7 show the relationship between low temperature impact and room temperature yield strength of different materials and processing methods. It can be seen that the DS-rolled 316L austenitic stainless steel has a good balance between strength and plasticity, and has excellent mechanical properties. Therefore, the DS warm rolling process proposed in the present invention can prepare 316L austenitic stainless steel with high strength and toughness.

[0070] It can be seen that the invention adopts the DS warm rolling process for rolling, which significantly improves the mechanical properties of 316L austenitic stainless steel compared with the synchronous warm rolling process. Its yield strength at room temperature can reach 845 MPa and its elongation can reach 22%; its yield strength at liquid nitrogen temperature of -196°C 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 technical difficulty is low. It can be widely used in the manufacture of cryogenic containers, ships, marine chemical industry and nuclear industry.

[0071] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling, characterized in that: The following steps are involved: Step a, hot forging the 316L steel ingot to obtain a forged 316L steel plate; Step b, heating the forged 316L steel plate, wherein the temperature of the steel plate after heating is 500-600°C; Step c, performing DS rolling on the heated 316L steel plate; Step d, repeat steps b and c ten to twenty-one times; Step e: leveling the 316L steel plate to obtain a high-strength and high-toughness 316L austenitic stainless steel plate.

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°C, the final forging temperature is ≥850°C, 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: When DS rolling is performed on 316L steel plates, the upper working roll for odd-numbered rolling passes is a small-diameter roll and the lower working roll is a large-diameter roll, and the upper working roll for even-numbered rolling passes is a large-diameter roll and the lower working roll is a small-diameter roll.

4. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 3, characterized in that: The diameter ratio of the large diameter roller to the small diameter roller is k, 1 <k≤1.2。 5. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 3, characterized in that: During all rolling passes, the 316L steel plate first contacts the large diameter roll.

6. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 3, characterized in that: During DS rolling, the small-diameter roll and the large-diameter working roll are provided with a horizontal offset d in the horizontal direction, and the range of d is 1.5~4 mm.

7. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 6, characterized in that: The value of the horizontal misalignment d in each rolling pass is different, and the ratio d / h of the horizontal misalignment d in each rolling pass to the plate thickness h is constant.

8. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to claim 1, characterized in that: When DS rolling is performed on 316L steel plate, after each rolling pass, the 316L steel plate is rotated 180° with the rolling direction as the axis before the next rolling pass.

9. The method for preparing high-strength and high-toughness 316L stainless steel by DS warm rolling according to any one of claims 1 to 8, characterized in that: The reduction in each rolling pass in step c is 3.7% to 7.5%, and the overall reduction after step d is completed is 56% to 95%.

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