A method for improving precipitates of s32050 super austenitic stainless steel

Abstract

The application discloses a method for improving precipitated phase of S32050 super austenitic stainless steel, and steps are as follows: S1, slab heating: the slab is loaded into a heating furnace and heated through a heat exchange section, a preheating section, a heating section and a soaking section; S2, hot rolling: after the slab is rolled by a rough rolling mill, the slab is sent to a finishing rolling mill for continuous rolling, the slab is heated by a coiling furnace, and rolling is completed above a sensitive temperature of the precipitated phase; S3, coiling and cooling: the slab is rapidly cooled by using laminar flow water and a water cooling pool; and S4, annealing and pickling: the precipitated phase is solid-solved by controlling annealing temperature and steel strip speed. The application has the advantages that: 1. the temperature of the heating furnace is increased to promote solid-solution and diffusion of the precipitated phase in the slab; 2. the coiling furnace is used to reduce the generation of the precipitated phase in the rolling process; 3. rapid cooling is used to reduce the generation of the precipitated phase; and 4. high-temperature slow solid-solution is used to make the precipitated phase in the steel strip fully solid-solved and diffused; and finally, the precipitated phase in the steel strip is completely eliminated, and the corrosion resistance and elongation are improved.

Description

Technical Field

[0001] This invention relates to the field of stainless steel processing technology, and in particular to a method for improving the precipitates in S32050 super austenitic stainless steel. Background Technology

[0002] S32050 super austenitic stainless steel is an austenitic stainless steel containing high levels of chromium, nickel, molybdenum, and nitrogen, and is widely used in industries such as nuclear power and petrochemicals.

[0003] Because S32050 super austenitic stainless steel has a high chromium and molybdenum content, it is prone to producing chromium-molybdenum precipitates during production. The main reasons for the formation of these precipitates are: First, the chromium and molybdenum content in S32050 super austenitic stainless steel is significantly increased compared to ordinary austenitic stainless steel, which increases the potential energy generated by the precipitated phases during the slab casting and hot rolling stages.

[0004] Second, the product passes through a precipitation-sensitive temperature range during the hot rolling process.

[0005] Third, the annealing process cannot fully dissolve and diffuse the precipitated phase in the material.

[0006] This chromium-molybdenum precipitate reduces the corrosion resistance and elongation of S32050 super austenitic stainless steel, making it highly susceptible to bending cracks, corrosion perforation, and other accidents during subsequent processing and use, severely restricting the application of this material. Summary of the Invention

[0007] The purpose of this invention is to provide a method for improving the precipitate content in S32050 super austenitic stainless steel. This method can effectively improve the precipitate content in S32050 super austenitic stainless steel and enhance its corrosion resistance and elongation.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: a method for improving the precipitates in S32050 super austenitic stainless steel, wherein the steps of the method are as follows: S1. Slab heating: The S32050 super austenitic stainless steel slab is heated in a heating furnace. The temperatures of the preheating zone, heating zone and soaking zone in the heating furnace are as follows: preheating zone 1020℃~1100℃, heating zone 1285℃~1305℃, soaking zone 1290℃~1310℃, and the slab is in the furnace for 250~280 minutes. S2, Hot Rolling: (a) Rough rolling: The rough rolling mill performs rough rolling on the heated slab, and the rough rolling temperature is controlled at 1070℃~1120℃ to obtain semi-finished strip steel; (b) Finish rolling: The furnace coil finishing mill continues to roll the semi-finished strip steel. The temperature of the furnace coil mill at the entrance and exit of the furnace coil mill is controlled at 1065℃~1085℃, and the final rolling temperature of the strip steel is controlled at 920℃~970℃. S3, Cooling and winding: (a) Laminar flow cooling: The strip steel that has been hot rolled is rapidly cooled by spraying water, and the temperature of the strip steel is rapidly reduced to below 660°C within 12 to 15 seconds; (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler, and then the coil is quickly immersed in a water tank for water cooling until the temperature of the coil is below 60°C. S4. Annealing and pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1140-1160℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 7.5-8.5 meters / minute. After annealing, pickling is performed to obtain S32050 super austenitic stainless steel finished products.

[0009] Furthermore, in the aforementioned method for improving the precipitates of S32050 super austenitic stainless steel, in step S2, both rough rolling and fine rolling are performed using 7 passes.

[0010] Furthermore, in the aforementioned method for improving the precipitates of S32050 super austenitic stainless steel, in step (b) of step S3, the cooling time of the steel coil in the water tank is controlled to be 8 to 10 hours.

[0011] Furthermore, in the aforementioned method for improving the precipitates of S32050 super austenitic stainless steel, in step (b) of step S3, the winding speed of the coiler is controlled at 180-250 m / min.

[0012] Furthermore, in the aforementioned method for improving the precipitates of S32050 super austenitic stainless steel, in step S4, the annealed steel strip is pickled with a pickling solution composed of nitric acid and hydrofluoric acid to remove the oxide scale on the surface of the steel strip.

[0013] Through the implementation of the above technical solution, the beneficial effects of this invention are as follows: In the slab heating stage before rolling, by controlling the temperature of each zone of the heating furnace and the time spent in the furnace, the precipitates generated in the casting stage of the slab are dissolved in advance to reduce the amount of precipitation in the slab; in the hot rolling stage, temperature-controlled rolling is performed, completing the entire roughing and finishing rolling process above the temperature range most sensitive to precipitates, effectively reducing the precipitation of precipitates during the rolling process; after rolling, a two-stage rapid cooling method of laminar flow cooling plus water tank cooling is adopted, allowing the strip steel to quickly pass through the precipitation temperature range of the precipitates. Significantly shortening the residence time of the strip in the precipitation temperature range not only further reduces the precipitation of precipitates but also greatly shortens the cooling cycle and improves production efficiency. Furthermore, by controlling the annealing temperature and speed during the annealing stage, the residual precipitates in the strip can be fully dissolved and eliminated, ultimately completely removing the precipitates inside the strip and achieving complete elimination of precipitates. This effectively improves the precipitate content in S32050 super austenitic stainless steel, thereby significantly improving the corrosion resistance and elongation of S32050 super austenitic stainless steel. Attached Figure Description

[0014] Figure 1 This is an internal micrograph of the S32050 super austenitic stainless steel product obtained by the method for improving the precipitates of S32050 super austenitic stainless steel according to Embodiment 1 of the present invention.

[0015] Figure 2 This is an internal micrograph of the S32050 super austenitic stainless steel product obtained by the method for improving the precipitates of S32050 super austenitic stainless steel according to Embodiment 2 of the present invention.

[0016] Figure 3 This is an internal micrograph of the S32050 super austenitic stainless steel product obtained by the method for improving the precipitates of S32050 super austenitic stainless steel according to Embodiment 3 of the present invention.

[0017] Figure 4 This is an internal micrograph of the S32050 super austenitic stainless steel product obtained by the method for improving the precipitates of S32050 super austenitic stainless steel described in Comparative Example 1 of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments.

[0019] A method for improving the precipitates in S32050 super austenitic stainless steel, comprising the following steps: S1. Slab heating: S32050 super austenitic stainless steel slabs are heated in a heating furnace. The temperatures of the preheating zone, heating zone, and soaking zone in the heating furnace are as follows: preheating zone 1020℃~1100℃, heating zone 1285℃~1305℃, soaking zone 1290℃~1310℃. The slab is in the furnace for 250~280 minutes and is then removed from the furnace after heating. The purpose of setting the above furnace temperatures is to dissolve the precipitates generated during the casting stage of the slab as early as possible, thereby initially reducing the precipitates in the slab. S2, Hot Rolling: (a) Rough rolling: The heated slab is rough rolled using a rough rolling mill. The rough rolling temperature is controlled between 1070℃ and 1120℃ to obtain semi-finished strip steel. In actual production, the number of rolling passes for rough rolling can be flexibly increased, decreased, and adjusted according to the slab specifications, production rhythm, and product performance requirements. It is preferred to use 7 rolling passes to complete the rough rolling. The purpose of controlling the rough rolling temperature at 1070℃ to 1120℃ during the rough rolling stage is twofold: firstly, to ensure that the strip avoids the 700℃ to 900℃ temperature range, which is the most sensitive temperature range for precipitates, during the entire rough rolling process, thereby suppressing the generation of precipitates in the strip during rough rolling; secondly, to utilize the high temperature to partially dissolve the chromium-molybdenum precipitates already present in the strip, thereby reducing the amount of precipitates in subsequent processes.

[0020] (b) Finish rolling: The semi-finished strip steel is rolled in a hot-rolled mill. During the rolling process, the strip steel is heated by the inlet and outlet hot-rolled mills. The temperatures of the inlet and outlet hot-rolled mills are controlled at 1065℃~1085℃, and the final rolling temperature of the strip steel is controlled at 920℃~970℃. In actual production, the number of rolling passes for finish rolling can be flexibly increased, decreased, and adjusted according to the slab specifications, production rhythm, and product performance requirements. It is preferred to use 7 rolling passes to complete finish rolling. During the finishing rolling stage, the finishing rolling temperature is controlled between 920℃ and 970℃. Combined with the heat preservation effect of the inlet and outlet coil furnaces, this ensures that the strip steel is always in a suitable rolling temperature range during the finishing rolling process. At the same time, this temperature is above the temperature range most sensitive to precipitates, and rolling is completed above the temperature most sensitive to precipitates. Under the condition of ensuring the smooth progress of the rolling process, the amount of precipitates generated in the strip steel during the finishing rolling stage is effectively reduced. Meanwhile, setting the final rolling temperature of the strip steel to no higher than 970℃ can prevent the formation of excessive secondary oxide scale on the surface of the strip steel, thus taking into account both the internal structure quality and the surface quality control.

[0021] S3, Cooling and winding: (a) Laminar flow cooling: The strip steel that has been hot rolled is rapidly cooled by spraying water, and the temperature of the strip steel is rapidly reduced to below 660°C within 12 to 15 seconds; The purpose of laminar flow cooling is to rapidly pass the strip temperature from around 970℃ through the 700℃~900℃ temperature range, which is the most sensitive temperature range for precipitates, thereby reducing the residence time of the strip in this range and thus inhibiting the formation of precipitates.

[0022] (b) Water tank cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler. The coiling speed of the coiler is controlled at 180-250 m / min. The purpose of controlling the coiling speed at 180-250 m / min is as follows: if the coiling speed is too fast, the strip steel is prone to scratches and poor coil shape during the coiling process, and the tension fluctuation is large at high speed, which affects the edge quality of the steel coil; if the speed is too slow, it will affect the production efficiency, and the long coiling time will increase the risk of precipitation of precipitates in the strip steel. Controlling the coiling speed at 180-250 m / min can not only ensure that the strip steel can quickly enter the subsequent water tank cooling process after laminar flow cooling, reducing the amount of strip steel precipitation, but also take into account the coiling stability and production rhythm, and ensure the quality of the steel coil.

[0023] After the steel coil is coiled, it is quickly immersed in a water tank for water cooling until the temperature of the steel coil is below 60°C. In practical applications, the cooling time of the steel coil in the water tank is controlled at 8 to 10 hours, which can make the temperature of the steel coil below 60°C. The purpose of the water tank cooling is to rapidly pass the steel strip temperature through the 500℃~700℃ range, which is the temperature range for the slow precipitation of precipitated phases. This reduces the residence time of the steel strip in this range, further suppressing the formation of precipitated phases. This not only significantly shortens the cooling cycle and improves production efficiency, but also rapidly reduces the steel strip temperature to below 60℃, preventing water spot defects from forming on the steel strip surface due to high temperatures. Thus, it improves both the internal and surface quality of the steel strip.

[0024] S4. Annealing and Pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1140-1160℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 7.5-8.5 meters / minute. After annealing, pickling is performed. During pickling, a pickling solution composed of nitric acid and hydrofluoric acid is used to pickle the annealed steel strip to remove the oxide scale on the surface of the steel strip and obtain the finished S32050 super austenitic stainless steel.

[0025] In the aforementioned annealing process, the annealing temperature is controlled at 1140–1160℃, and the running speed of the steel strip in the furnace is controlled at 7.5–8.5 m / min. The purpose is to: provide sufficient energy for the diffusion of chromium and molybdenum atoms by raising the annealing temperature to above 1140℃, so that the chromium-molybdenum precipitates generated during hot rolling and cooling can be fully dissolved and diffused, thereby eliminating the harmful effects of the precipitates on the material's corrosion resistance and plasticity; at the same time, controlling the annealing temperature below 1160℃ avoids excessively high temperatures that could lead to grain coarsening and damage to the material's mechanical properties; and at a suitable annealing temperature, controlling the steel strip running speed at 7.5–8.5 m / min ensures that the steel strip has sufficient holding time in the high-temperature zone to ensure that the precipitates can be fully dissolved, while also taking into account production efficiency and avoiding excessively slow speeds that could affect output. Example 1

[0026] A method for improving the precipitates in S32050 super austenitic stainless steel, comprising the following steps: S1. Slab heating: The S32050 super austenitic stainless steel slab is heated in a heating furnace. The temperatures of the preheating zone, heating zone and soaking zone in the heating furnace are 1100℃, 1305℃, and 1310℃, respectively. The slab is in the furnace for 280 minutes and is then removed from the heating furnace after heating is completed. S2, Hot Rolling: (a) Rough rolling: The heated slab is rough rolled by a rough rolling mill. The rough rolling is carried out in 7 passes and the rough rolling temperature is controlled at 1120℃ to obtain semi-finished strip steel. (b) Finish rolling: The semi-finished strip steel is rolled in 7 passes in a hot-rolled mill. During the rolling process, the strip steel is heated by the inlet and outlet hot-rolled mills. The temperature of the inlet hot-rolled mill is controlled at 1085°C, the temperature of the outlet hot-rolled mill is controlled at 1085°C, and the final rolling temperature of the strip steel is controlled at 970°C. S3, Cooling and winding: (a) Laminar flow cooling: The hot-rolled strip steel is rapidly cooled for 12 seconds by spraying water to quickly reduce the strip steel temperature to 656°C. (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler. The coiling speed of the coiler is controlled at 250 m / min. Then the coil is quickly immersed in a water tank for water cooling. The cooling time of the coil in the water tank is controlled at 10 hours. The final temperature of the coil after cooling is 41°C. S4. Annealing and Pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1160℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 8.5 meters / minute. After annealing, pickling is performed. During pickling, a pickling solution composed of nitric acid and hydrofluoric acid is used to pickle the annealed steel strip to remove the oxide scale on the surface of the steel strip and obtain the finished S32050 super austenitic stainless steel.

[0027] The internal microscopic photograph of the S32050 super austenitic stainless steel product obtained in Example 1 is shown below. Figure 1 ,Depend on Figure 1 It can be seen that no precipitated phases were detected inside the S32050 super austenitic stainless steel product obtained in Example 1. Example 2

[0028] A method for improving the precipitates in S32050 super austenitic stainless steel, comprising the following steps: S1. Slab heating: S32050 super austenitic stainless steel slabs were heated in a heating furnace. The temperatures of the preheating zone, heating zone, and soaking zone in the heating furnace were 1057°C, 1295°C, and 1300°C, respectively. The slabs were in the furnace for 276 minutes and were then removed from the heating furnace after heating was completed. S2, Hot Rolling: (a) Rough rolling: The heated slab is rough rolled using a rough rolling mill. The rough rolling process consists of 7 passes, and the rough rolling temperature is controlled at 1100℃ to obtain semi-finished strip steel. (b) Finish rolling: The semi-finished strip steel is rolled in 7 passes in a hot-rolled mill. During the rolling process, the strip steel is heated by the inlet and outlet hot-rolled mills. The temperature of the inlet hot-rolled mill is controlled at 1076°C and the temperature of the outlet hot-rolled mill is controlled at 1076°C. The final rolling temperature of the strip steel is controlled at 950°C. S3, Cooling and winding: (a) Laminar flow cooling: The hot-rolled strip steel is rapidly cooled for 13 seconds by spraying water to quickly reduce the strip steel temperature to 628°C. (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler. The coiling speed of the coiler is controlled at 220 m / min. Then the coil is quickly immersed in a water tank for water cooling. The cooling time of the coil in the water tank is controlled at 9 hours. The final temperature of the coil after cooling is 46°C. S4. Annealing and Pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1152℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 8 meters / minute. After annealing, pickling is performed. During pickling, a pickling solution composed of nitric acid and hydrofluoric acid is used to pickle the annealed steel strip to remove the oxide scale on the surface of the steel strip and obtain the finished S32050 super austenitic stainless steel.

[0029] The internal microscopic photograph of the S32050 super austenitic stainless steel product obtained in Example 2 is shown below. Figure 2 ,Depend on Figure 2 It is evident that no precipitated phases were detected inside the S32050 super austenitic stainless steel product obtained in Example 2. Example 3

[0030] A method for improving the precipitates in S32050 super austenitic stainless steel, comprising the following steps: S1. Slab heating: The S32050 super austenitic stainless steel slab is heated in a heating furnace. The temperatures of the preheating zone, heating zone and soaking zone in the heating furnace are 1020℃, 1285℃, and 1290℃, respectively. The slab is in the furnace for 250 minutes and is then removed from the heating furnace after heating is completed. S2, Hot Rolling: (a) Rough rolling: The heated slab is rough rolled using a rough rolling mill. The rough rolling process consists of 7 passes, and the rough rolling temperature is controlled at 1070℃ to obtain semi-finished strip steel. (b) Finish rolling: The semi-finished strip steel is rolled in 7 passes in a hot-rolled mill. During the rolling process, the strip steel is kept warm by the inlet and outlet hot-rolled mills. The temperature of the inlet hot-rolled mill is controlled at 1065°C, the temperature of the outlet hot-rolled mill is controlled at 1065°C, and the final rolling temperature of the strip steel is controlled at 920°C. S3, Cooling and winding: (a) Laminar flow cooling: The hot-rolled strip steel is rapidly cooled for 15 seconds by spraying water to quickly reduce the strip steel temperature to 615°C. (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler. The coiling speed of the coiler is controlled at 180 meters / minute. Then the coil is quickly immersed in a water tank for water cooling. The cooling time of the coil in the water tank is controlled at 8 hours. The final temperature of the coil after cooling is 52°C. S4. Annealing and Pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1140℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 7.5 meters / minute. After annealing, pickling is performed. During pickling, a pickling solution composed of nitric acid and hydrofluoric acid is used to pickle the annealed steel strip to remove the oxide scale on the surface of the steel strip and obtain the finished S32050 super austenitic stainless steel.

[0031] The internal microscopic photograph of the S32050 super austenitic stainless steel product obtained in Example 3 is shown below. Figure 3 ,Depend on Figure 3 It is evident that no precipitated phases were detected inside the S32050 super austenitic stainless steel product obtained in Example 3.

[0032] Comparative Example 1 A method for improving the precipitates in S32050 super austenitic stainless steel, comprising the following steps: S1. Slab heating: S32050 super austenitic stainless steel slabs are heated in a heating furnace. The temperatures of the preheating zone, heating zone, and soaking zone in the heating furnace are 1000℃ for the preheating zone, 1272℃ for the heating zone, and 1287℃ for the soaking zone, respectively. The slabs are in the furnace for 240 minutes and are then removed from the heating furnace after heating is completed. S2, Hot Rolling: (a) Rough rolling: The heated slab is rough rolled using a rough rolling mill. The rough rolling process consists of 7 passes, and the rough rolling temperature is controlled at 1060℃ to obtain semi-finished strip steel. (b) Finish rolling: The semi-finished strip steel is rolled in 7 passes in a hot-rolled mill. During the rolling process, the strip steel is kept warm by the inlet and outlet hot-rolled mills. The temperature of the inlet hot-rolled mill is controlled at 1056°C, the temperature of the outlet hot-rolled mill is controlled at 1059°C, and the final rolling temperature of the strip steel is controlled at 915°C. S3, Cooling and winding: (a) Laminar flow cooling: The hot-rolled strip steel is rapidly cooled for 10 seconds by spraying water to quickly reduce the temperature of the strip steel to 676°C. (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler. The coiling speed of the coiler is controlled at 280 m / min. Then the coil is quickly immersed in a water tank for water cooling. The cooling time of the coil in the water tank is controlled at 9 hours. The final temperature of the coil after cooling is 47°C. S4. Annealing and Pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1136℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 9 meters / minute. After annealing, pickling is performed. During pickling, a pickling solution composed of nitric acid and hydrofluoric acid is used to pickle the annealed steel strip to remove the oxide scale on the surface of the steel strip and obtain the finished S32050 super austenitic stainless steel.

[0033] The internal microscopic photograph of the S32050 super austenitic stainless steel product prepared in Comparative Example 1 is shown below. Figure 4 ,Depend on Figure 4 It is evident that the S32050 super austenitic stainless steel product prepared in Comparative Example 1 contains a large number of precipitated phases.

[0034] The specific process parameters for each step of heating, rolling, cooling and annealing in Examples 1, 2, 3 and Comparative Example 1 are detailed in Tables 1 to 4. The precipitates and performance test results of the products obtained under each process condition are shown in Table 5.

[0035]

[0036]

[0037] The product was sent to the laboratory for precipitate analysis, and the results are shown in Table 5.

[0038] From Table 5 and Figure 1 , Figure 2 , Figure 3 It can be seen that no precipitated phases were detected in the S32050 super austenitic stainless steel products manufactured in Examples 1-3 of this invention, and the corrosion test results all showed no corrosion, with an elongation of over 50%; while from Table 5 and Figure 4 It can be seen that the S32050 super austenitic stainless steel product manufactured in Comparative Example 1 has more precipitates, and corrosion tests show corrosion with an elongation of only 42%. This indicates that the method of the present invention can effectively improve the precipitate content in S32050 super austenitic stainless steel and significantly improve the corrosion resistance and elongation of S32050 super austenitic stainless steel.

[0039] The advantages of this invention are: In the slab heating stage before rolling, by controlling the temperature of each zone of the heating furnace and the time spent in the furnace, the precipitates generated during the casting stage are dissolved in advance, thereby reducing the amount of precipitation in the slab; in the hot rolling stage, temperature-controlled rolling is performed, completing the entire roughing and finishing rolling process above the temperature range most sensitive to precipitates, effectively reducing the precipitation of precipitates during the rolling process; after rolling, a two-stage rapid cooling method of laminar flow cooling plus water tank cooling is adopted, allowing the strip steel to quickly pass through the precipitation temperature range of the precipitates, significantly shortening the time required for the strip steel to pass through the precipitation temperature range. The residence time within the precipitation temperature range not only effectively reduces the precipitation of precipitates but also significantly shortens the cooling cycle and improves production efficiency. Furthermore, by controlling the annealing temperature and speed during the annealing stage, the residual precipitates in the strip can be fully dissolved and eliminated, ultimately completely removing the precipitates inside the strip and achieving complete elimination of precipitates. This effectively improves the precipitate content in S32050 super austenitic stainless steel, thereby significantly improving the corrosion resistance and elongation of S32050 super austenitic stainless steel.

[0040] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A method for improving the precipitates in S32050 super austenitic stainless steel, characterized in that: The steps of the method are as follows: S1. Slab heating: The S32050 super austenitic stainless steel slab is heated in a heating furnace. The temperatures of the preheating zone, heating zone and soaking zone in the heating furnace are as follows: preheating zone 1020℃~1100℃, heating zone 1285℃~1305℃, soaking zone 1290℃~1310℃, and the slab is in the furnace for 250~280 minutes. S2, Hot Rolling: (a) Rough rolling: The rough rolling mill performs rough rolling on the heated slab, and the rough rolling temperature is controlled at 1070℃~1120℃ to obtain semi-finished strip steel; (b) Finish rolling: The furnace coil finishing mill continues to roll the semi-finished strip steel. The temperature of the furnace coil mill at the entrance and exit of the furnace coil mill is controlled at 1065℃~1085℃, and the final rolling temperature of the strip steel is controlled at 920℃~970℃. S3, Cooling and winding: (a) Laminar flow cooling: The strip steel that has been hot rolled is rapidly cooled by spraying water, and the temperature of the strip steel is rapidly reduced to below 660°C within 12 to 15 seconds; (b) Water cooling: The strip steel after laminar flow cooling is coiled into a coil using a coiler, and then the coil is quickly immersed in a water tank for water cooling until the temperature of the coil is below 60°C. S4. Annealing and pickling: After the steel coils have been cooled in the water tank, they are uncoiled and sent to a continuous annealing furnace for annealing. The annealing temperature is controlled at 1140-1160℃, and the running speed of the steel strip in the continuous annealing furnace is controlled at 7.5-8.5 meters / minute. After annealing, pickling is performed to obtain S32050 super austenitic stainless steel finished products.

2. The method for improving the precipitates in S32050 super austenitic stainless steel according to claim 1, characterized in that: In step S2, both rough rolling and fine rolling are performed using 7 passes.

3. The method for improving the precipitates in S32050 super austenitic stainless steel according to claim 1, characterized in that: In step (b) of step S3, the cooling time of the steel coil in the water tank is controlled to be 8 to 10 hours.

4. The method for improving the precipitates in S32050 super austenitic stainless steel according to claim 1, characterized in that: In step (b) of step S3, the winding speed of the winding machine is controlled at 180 to 250 meters per minute.

5. The method for improving the precipitates in S32050 super austenitic stainless steel according to claim 1, characterized in that: In step S4, the annealed steel strip is pickled using a pickling solution composed of nitric acid and hydrofluoric acid to remove the oxide scale on the surface of the steel strip.

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