Online solution annealing process for austenitic stainless steel

Abstract

The invention discloses an online solution annealing process for austenitic stainless steel. The online solution annealing process comprises the following steps that S1, smelted molten steel is subjected to continuous casting to form a plate blank; s2, a heating furnace is adopted for heating the casting blank, the temperature of a preheating zone is controlled to be 990-1130 DEG C, the temperature of a heating zone is controlled to be 1175-1280 DEG C, and the temperature of a soaking zone is controlled to be 1280-1285 DEG C; s3, seven passes of rough rolling and calendering are carried out; s4, 5-7 passes of finish rolling and calendering are carried out, wherein the finish rolling temperature of a finish rolling machine of the steckel mill is controlled to be 980-1000 DEG C; the rolling speed of final pass finish rolling is 210-320 mpm, and the recrystallization time of the casting blank is controlled to be 7-10 S; s5, the casting blank is rapidly and evenly cooled to 500 DEG C at the speed of 23-25 DEG C / S in a laminar water cooling mode and then coiled; and S6, pickling to obtain the austenitic stainless steel coiled material. The method has the advantage that online solution annealing of the austenitic stainless steel can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of steel rolling, and in particular to an online solid solution annealing process for austenitic stainless steel. Background Art

[0002] The steel industry is an important pillar industry of my country's national economy and also one of the main battlefields for CO2 emission reduction. Austenitic stainless steel needs to be solution treated after hot rolling. Conventional annealing and pickling processes mainly use offline solution treatment: the hot-rolled austenitic stainless steel sheet must be cooled to room temperature first, and then reheated to the solution temperature for solution treatment. This not only consumes a lot of energy, but also has a longer production cycle. Generally, hot-rolled coils consume about 35Nm3 / ton of natural gas, and the unit price of natural gas is 4.0~6.0 yuan / Nm3, the heating cost is about 140~210 yuan / ton, and CO2 emissions are 68.74kg / ton. At the same time, online heat treatment technology has also shown unique advantages in the development of micro-alloyed high-strength steel. It organically combines controlled rolling and controlled cooling. Compared with the offline solution treatment method, it can obtain better comprehensive mechanical properties. However, applying it to austenitic stainless steel presents certain challenges: 1) The online heat treatment process must simultaneously meet the multiple requirements of product mechanical properties, corrosion resistance and surface quality; 2) Austenitic stainless steel has a low thermal conductivity, and it is difficult to control the plate shape after cooling under high cooling intensity after rolling, resulting in the inability to guarantee the productivity of the subsequent engineering. Therefore, it is urgent to break through the relevant technical bottlenecks, make full use of the residual heat from rolling to develop an online solution annealing process for austenitic stainless steel, and promote the transformation and development of my country's stainless steel industry towards a green and low-carbon direction. Summary of the invention

[0003] The purpose of the present invention is to provide an austenitic stainless steel online solid solution annealing process capable of realizing the austenitic stainless steel online solid solution annealing.

[0004] To achieve the above object, the present invention adopts the following technical scheme: an online solution annealing process for austenitic stainless steel, comprising the following steps: S1: continuously casting the smelted molten steel into slabs; S2: The ingot is heated in a heating furnace. The temperature of the preheating zone of the heating furnace is controlled at 990-1130°C, the temperature of the heating zone of the heating furnace is controlled at 1175-1280°C, the temperature of the soaking zone of the heating furnace is controlled at 1280-1285°C, and the conditions for the ingot to be taken out of the heating furnace must meet the following conditions: the time in the furnace is ≥200min and the pure time in the furnace is ≥100min, where: The furnace time is the sum of the time the billet spends in the preheating zone, heating zone and soaking zone. Pure furnace time is the sum of the furnace time of the billet in the heating zone and the soaking zone; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The cast billet after rough rolling is subjected to 5 to 7 passes of finishing rolling by using a Steckel mill, wherein: The finishing temperature of the Steckel mill is controlled at 980-1000℃; The rolling speed of the last pass of the finishing mill is controlled at 210-320 mpm, and the billet is cooled after sufficient recrystallization time is given. The recrystallization time of the billet is controlled at 7-10 seconds. S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 23-25°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil.

[0005] Further, the aforementioned online solution annealing process for austenitic stainless steel, wherein: in S2, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the preheating zone is controlled at 990°C, and the temperature of the second temperature zone of the preheating zone is controlled at 1130°C; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the heating zone is controlled at 1175°C, the temperature of the second temperature zone of the heating zone is controlled at 1245°C, the temperature of the third temperature zone of the heating zone is controlled at 1270°C, and the temperature of the fourth temperature zone of the heating zone is controlled at 1280°C.

[0006] Furthermore, in the aforementioned online solution annealing process for austenitic stainless steel, in which: in S4, the temperature in the inlet coil furnace and the outlet coil furnace of the Steckel mill are both controlled at 1060°C.

[0007] Furthermore, in the aforementioned online solution annealing process for austenitic stainless steel, in which: in S4, the rolling speed of the last finishing pass of the finishing mill of the Steckel mill is controlled at 320 mpm, and the recrystallization time of the ingot is controlled at 8 s.

[0008] Through the implementation of the above technical scheme, the beneficial effects of the present invention are as follows: (1) The process of the present invention can realize online solution annealing of austenitic stainless steel. Compared with the traditional offline solution annealing process, the process of the present invention omits one annealing process. The present invention first formulates a reasonable heating furnace heating process to ensure that the final rolling temperature during hot rolling is controlled at 980-1000°C. Then, by formulating a reasonable rolling schedule and formulating a precise speed matching mode, the rolling speed of the last pass of finishing rolling is reduced and controlled to give the ingot sufficient recrystallization time, thereby utilizing the rolling waste heat to fully online solution the austenitic stainless steel to achieve the effect of offline solution. , and then by formulating a reasonable rapid and uniform cooling mode, the ingot is quickly and uniformly cooled to 500℃ for coiling, so that the carbides in the austenitic stainless steel are dissolved, the scale structure is improved, and the d-ferrite is decomposed, effectively reducing the degree of defective plate shape; the austenitic stainless steel produced by the process of the present invention ensures excellent mechanical properties, corrosion resistance and other properties while ensuring the plate shape; (2) The online solution annealing process of the present invention can solve the problem of long existing production cycle, reduce production and processing costs, and reduce carbon emissions, greatly improving the overall profitability, and making positive contributions to the country's carbon peak and carbon neutrality, meeting the requirements of green and low-carbon strategic transformation and development. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Schematic diagram of the structural principle of the Steckel mill.

[0010] Figure 2 Schematic diagram of the structural principle of the Steckel mill and the subsequent layer cooling.

[0011] Figure 3 It is a schematic diagram comparing the grain size changes of the online solution annealing process of austenitic stainless steel described in the present invention and the conventional annealing and pickling process.

[0012] Figure 4 It is a schematic diagram comparing the cooling modes of the online solution annealing process for austenitic stainless steel of the present invention and the conventional annealing and pickling process.

[0013] Figure 5 It is a schematic diagram comparing the morphology of the oxide layer of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel in Example 1 of the present invention and the oxide layer of austenitic stainless steel obtained by the conventional annealing and pickling process.

[0014] Figure 6 Schematic diagram showing the yield strength comparison between the austenitic stainless steel produced by the online solution annealing process for austenitic stainless steel in Example 1 of the present invention and the austenitic stainless steel produced by the conventional annealing and pickling process after the subsequent cold rolling process.

[0015] Figure 7Schematic diagram showing the comparison of the tensile strength of austenitic stainless steel produced by online solution annealing process of austenitic stainless steel in Example 1 of the present invention and austenitic stainless steel produced by conventional annealing and pickling process after subsequent cold rolling process.

[0016] Figure 8 It is a schematic diagram comparing the elongation of austenitic stainless steel produced by online solution annealing process of austenitic stainless steel in Example 1 of the present invention and austenitic stainless steel produced by conventional annealing and pickling process after subsequent cold rolling and calendering process.

[0017] Fig. 9 Schematic diagram showing the comparison of the corrosion areas of austenitic stainless steel produced by online solution annealing process of austenitic stainless steel in Example 1 of the present invention and austenitic stainless steel produced by conventional annealing and pickling process. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0019] An online solution annealing process for austenitic stainless steel comprises the following steps: S1: continuously casting the smelted molten steel into slabs; S2: The ingot is heated in a heating furnace. The temperature of the preheating zone of the heating furnace is controlled at 990-1130°C, the temperature of the heating zone of the heating furnace is controlled at 1175-1280°C, the temperature of the soaking zone of the heating furnace is controlled at 1280-1285°C, and the conditions for the ingot to be taken out of the heating furnace must meet the following conditions: the time in the furnace is ≥200min and the pure time in the furnace is ≥100min, where: The furnace time is the sum of the time the billet spends in the preheating zone, heating zone and soaking zone. Pure furnace time is the sum of the furnace time of the billet in the heating zone and the soaking zone; By formulating a reasonable heating furnace heating process, the final rolling temperature during hot rolling and finishing rolling is controlled at 980-1000℃; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The cast billet after rough rolling is subjected to 5 to 7 passes of finishing rolling by using a Steckel mill, wherein: The finishing temperature of the Steckel mill is controlled at 980-1000℃; The rolling speed of the last pass of the finishing mill is controlled at 210-320 mpm, and the billet is cooled after sufficient recrystallization time is given. The recrystallization time of the billet is controlled at 7-10 seconds. Steckel mill is a commonly used equipment, its structure is as follows Figure 1As shown, it includes a finishing mill 1, an inlet coil furnace 2 arranged at the inlet side of the finishing mill 1, and an outlet coil furnace 3 arranged at the outlet side of the finishing mill 1, and a drum is installed in the middle of each coil furnace to realize the reciprocating rolling of the strip steel; in this embodiment, the temperature in the inlet coil furnace 2 and the outlet coil furnace 3 of the Steckel mill is controlled at 1060°C, which can further ensure that the finishing mill final rolling temperature of the Steckel mill is controlled at 980-1000°C; The recrystallization time is the time from the last pass of the finishing mill to the laminar water cooling of the next pass. Figure 2 As shown in the figure, the distance between the outlet of the finishing mill and the subsequent laminar water cooling is m, and the time it takes for the billet to pass m after being output from the finishing mill is the recrystallization time of the billet; S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 23-25°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil. Example 1

[0020] An online solution annealing process for austenitic stainless steel comprises the following steps: S1: Continuously casting the smelted molten steel to form a slab; the size of the slab is 200mm*1280mm*12.5m; S2: The ingot is heated by a heating furnace, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the preheating zone is controlled at 990°C, the temperature of the second temperature zone of the preheating zone is controlled at 1130°C, and the preheating zone is in the furnace for 100 minutes; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the heating zone is controlled at 1175°C, the temperature of the second temperature zone of the heating zone is controlled at 1245°C, the temperature of the third temperature zone of the heating zone is controlled at 1270°C, the temperature of the fourth temperature zone of the heating zone is controlled at 1280°C, and the heating zone is in the furnace for 60 minutes; the temperature of the soaking zone is controlled at 1280°C, and the soaking zone is in the furnace for 40 minutes; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The rough-rolled ingot is subjected to 7 passes of finishing rolling by a Steckel mill, and the target thickness of the finishing rolling is 3.5 mm, wherein: The finishing temperature of the Steckel mill is controlled at 980°C; The rolling speed of the last pass of the finishing mill is controlled at 320mpm, and the billet is cooled after sufficient recrystallization time is given. The recrystallization time of the billet is controlled at 8S. The temperature in the inlet coil furnace 2 and the outlet coil furnace 3 of the Steckel mill is controlled at 1060°C; S5: The finished rolled ingot is quickly and uniformly cooled to 500°C at a rate of 23°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil. Example 2

[0021] An online solution annealing process for austenitic stainless steel comprises the following steps: S1: Continuously casting the smelted molten steel to form a slab; the size of the slab is 200mm*1280mm*12.5m; S2: The ingot is heated by a heating furnace, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the preheating zone is controlled at 990°C, the temperature of the second temperature zone of the preheating zone is controlled at 1100°C, and the preheating zone is in the furnace for 120 minutes; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the heating zone is controlled at 1175°C, the temperature of the second temperature zone of the heating zone is controlled at 1225°C, the temperature of the third temperature zone of the heating zone is controlled at 1260°C, the temperature of the fourth temperature zone of the heating zone is controlled at 1280°C, and the heating zone is in the furnace for 70 minutes; the temperature of the soaking zone is controlled at 1285°C, and the soaking zone is in the furnace for 50 minutes; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The rough-rolled ingot is subjected to five passes of finishing rolling by a Steckel mill, with a target thickness of 4.8 mm, including: The finishing temperature of the Steckel mill is controlled at 990°C; The rolling speed of the last pass of the finishing mill was controlled at 256 mpm, and the ingot was cooled after being given sufficient recrystallization time. The recrystallization time of the ingot was controlled at 10 seconds. The temperature in the inlet coil furnace 2 and the outlet coil furnace 3 of the Steckel mill is controlled at 1060°C; S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 25°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil. Example 3

[0022] An online solution annealing process for austenitic stainless steel comprises the following steps: S1: Continuously casting the smelted molten steel to form a slab; the size of the slab is 200mm*1280mm*12.5m; S2: The ingot is heated by a heating furnace, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the preheating zone is controlled at 1000°C, the temperature of the second temperature zone of the preheating zone is controlled at 1130°C, and the preheating zone is in the furnace for 110 minutes; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the heating zone is controlled at 1175°C, the temperature of the second temperature zone of the heating zone is controlled at 1200°C, the temperature of the third temperature zone of the heating zone is controlled at 1270°C, the temperature of the fourth temperature zone of the heating zone is controlled at 1280°C, and the heating zone is in the furnace for 60 minutes; the temperature of the soaking zone is controlled at 1283°C, and the soaking zone is in the furnace for 50 minutes; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The rough-rolled ingot is subjected to 7 passes of finishing rolling by a Steckel mill, and the target thickness of the finishing rolling is 3.8 mm, wherein: The finishing temperature of the Steckel mill is controlled at 1000°C; The rolling speed of the last pass of the finishing mill was controlled at 284 mpm, and the ingot was cooled after being given sufficient recrystallization time. The recrystallization time of the ingot was controlled at 9 seconds. The temperature in the inlet coil furnace 2 and the outlet coil furnace 3 of the Steckel mill is controlled at 1060°C; S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 24°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil. Example 4

[0023] An online solution annealing process for austenitic stainless steel comprises the following steps: S1: Continuously casting the smelted molten steel to form a slab; the size of the slab is 200mm*1280mm*12.5m; S2: The ingot is heated by a heating furnace, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the preheating zone is controlled at 990°C, the temperature of the second temperature zone of the preheating zone is controlled at 1120°C, and the preheating zone is in the furnace for 130 minutes; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone of the heating zone is controlled at 1175°C, the temperature of the second temperature zone of the heating zone is controlled at 1190°C, the temperature of the third temperature zone of the heating zone is controlled at 1260°C, the temperature of the fourth temperature zone of the heating zone is controlled at 1280°C, and the heating zone is in the furnace for 70 minutes; the temperature of the soaking zone is controlled at 1285°C, and the soaking zone is in the furnace for 60 minutes; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The rough-rolled ingot is subjected to 7 passes of finishing rolling by a Steckel mill, and the target thickness of the finishing rolling is 3.2 mm, wherein: The finishing temperature of the Steckel mill is controlled at 1000°C; The rolling speed of the last pass of the finishing mill was controlled at 366 mpm, and the ingot was cooled after being given sufficient recrystallization time. The recrystallization time of the ingot was controlled at 7 seconds. The temperature in the inlet coil furnace 2 and the outlet coil furnace 3 of the Steckel mill is controlled at 1060°C; S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 25°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil.

[0024] In the present invention, Figure 3 Schematic diagram showing the comparison of the grain size changes between the online solution annealing process for austenitic stainless steel of the present invention and the conventional annealing and pickling process; Figure 3 The ultra-fast cooling + pickling process represents the online solution annealing process of austenitic stainless steel according to the present invention. Figure 3 It can be seen that the grain size of the austenitic stainless steel structure after annealing by the online solution annealing process of the present invention is smaller than the grain size of the austenitic stainless steel structure after normal annealing by the conventional annealing and pickling process, indicating that the austenitic stainless steel after annealing by this process has better performance; In the present invention, Figure 4 FIG. 1 is a schematic diagram comparing the cooling modes of the online solution annealing process for austenitic stainless steel of the present invention and the conventional annealing and pickling process. Figure 4 It can be known that the online solution annealing process of austenitic stainless steel of the present invention adopts a rapid cooling mode. The process of the present invention is on the left side of the dynamic precipitation start line and the static precipitation start line, and does not pass through the dynamic precipitation start line and the static precipitation start line, which reduces the precipitation of carbides and improves the corrosion resistance of the surface of austenitic stainless steel; while the conventional annealing and pickling process adopts a normal cooling method, and the conventional annealing and pickling process passes through the dynamic precipitation start line, so that a certain amount of carbides will precipitate, resulting in reduced corrosion resistance; In the present invention, Figure 5 Schematic diagram showing the morphology comparison between the oxide layer of austenitic stainless steel obtained by the online solid solution annealing and pickling process of austenitic stainless steel in Example 1 of the present invention and the oxide layer of austenitic stainless steel obtained by the conventional annealing and pickling process; Figure 5It can be seen that the oxide layer of the austenitic stainless steel obtained by the online solution annealing process of the present invention is uniform and continuously distributed, which can greatly improve the pickling property of the surface, while the oxide layer of the austenitic stainless steel obtained by the conventional annealing and pickling process is uneven and discontinuously distributed, and is partially embedded in the matrix, resulting in poor pickling property of the surface; In the present invention, Figure 6 Schematic diagram showing the yield strength comparison between the austenitic stainless steel obtained by the online solution annealing process of austenitic stainless steel in Example 1 of the present invention and the austenitic stainless steel obtained by the conventional annealing and pickling process after the subsequent cold rolling process; Figure 6 In the figure, YS represents yield strength, normal annealing represents austenitic stainless steel coils obtained by conventional annealing and pickling process, and annealing-free represents austenitic stainless steel coils obtained by online solution annealing process of austenitic stainless steel of the present invention; Figure 6 It can be seen that the yield strength of austenitic stainless steel produced by online solution annealing process of austenitic stainless steel is not significantly different from that of austenitic stainless steel produced by conventional annealing and pickling process, and both meet the national standard. In the present invention, Figure 7 Schematic diagram showing the comparison of the tensile strength of the austenitic stainless steel obtained by the online solution annealing process of austenitic stainless steel in Example 1 of the present invention and the austenitic stainless steel obtained by the conventional annealing and pickling process after the subsequent cold rolling process; Figure 7 In the figure, TS represents tensile strength, normal annealing represents austenitic stainless steel coils obtained by conventional annealing and pickling process, and annealing-free represents austenitic stainless steel coils obtained by the online solution annealing process of austenitic stainless steel of the present invention; Figure 7 It can be seen that there is no significant difference in the tensile strength of austenitic stainless steel produced by the online solution annealing process of austenitic stainless steel and the tensile strength of austenitic stainless steel produced by the conventional annealing and pickling process, both of which meet the national standard. In the present invention, Figure 8 Schematic diagram showing the comparison of the elongation of the austenitic stainless steel obtained by the online solution annealing process of austenitic stainless steel in Example 1 of the present invention and the austenitic stainless steel obtained by the conventional annealing and pickling process after the subsequent cold rolling process; Figure 8 In the figure, EL represents elongation, normal annealing represents an austenitic stainless steel coil obtained by a conventional annealing and pickling process, and annealing-free represents an austenitic stainless steel coil obtained by an online solution annealing process of austenitic stainless steel of the present invention; Figure 8 It can be seen that there is no significant difference between the elongation of austenitic stainless steel produced by the online solution annealing process and the elongation of austenitic stainless steel produced by the conventional annealing and pickling process, both of which meet the national standard. In the present invention, Fig. 9Schematic diagram showing the comparison of the corrosion area of ​​the austenitic stainless steel obtained by the online solution annealing process of austenitic stainless steel in Example 1 of the present invention and the austenitic stainless steel obtained by the conventional annealing and pickling process; Fig. 9 In the figure, the general material represents the austenitic stainless steel coil obtained by the conventional annealing and pickling process, and the annealing-free material represents the austenitic stainless steel coil obtained by the austenitic stainless steel online solid solution annealing process of the present invention; Fig. 9 It can be known that the corrosion area ratio of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel is lower than the corrosion area ratio of austenitic stainless steel obtained by the conventional annealing and pickling process; the corrosion resistance of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel of the present invention is better; and, as for the plate shape defect retention rate, the plate shape defect retention rate of austenitic stainless steel obtained by the conventional annealing and pickling process is as high as 5.2%, while the plate shape defect retention rate of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel of the present invention is 2.5%, and the plate shape defect retention rate of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel of the present invention is lower than the plate shape defect retention rate of austenitic stainless steel obtained by the conventional annealing and pickling process, which can be explained that the plate shape of austenitic stainless steel obtained by the online solid solution annealing process of austenitic stainless steel of the present invention is better; The advantages of the present invention are: (1) The process of the present invention can realize online solution annealing of austenitic stainless steel. Compared with the traditional offline solution annealing process, the process of the present invention omits one annealing process. The present invention first formulates a reasonable heating furnace heating process to ensure that the final rolling temperature during hot rolling is controlled at 980-1000°C. Then, by formulating a reasonable rolling schedule and formulating a precise speed matching mode, by reducing and controlling the rolling speed of the last pass of finishing rolling, sufficient recrystallization time is given to the ingot, thereby utilizing the residual heat of rolling to fully carry out online solution of austenitic stainless steel to achieve the effect of offline solution. Then, by formulating A reasonable rapid and uniform cooling mode can quickly and uniformly cool the ingot to 500°C for coiling, so that the carbides in the austenitic stainless steel can be dissolved, the scale structure can be improved, and the d-ferrite can be decomposed, effectively reducing the degree of defective plate shape. The austenitic stainless steel produced by the process of the present invention can ensure excellent mechanical properties, corrosion resistance and other properties while ensuring the plate shape. (2) The online solution annealing process of the present invention can solve the problem of long existing production cycle, reduce production and processing costs, and reduce carbon emissions, greatly improving the overall profitability, making positive contributions to the country's carbon peak and carbon neutrality, and meeting the requirements of green and low-carbon strategic transformation and development.

[0025] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. An online solution annealing process for austenitic stainless steel, characterized by: The following steps are involved: S1: continuously casting the smelted molten steel into slabs; S2: The ingot is heated in a heating furnace. The temperature of the preheating zone of the heating furnace is controlled at 990-1130°C, the temperature of the heating zone of the heating furnace is controlled at 1175-1280°C, the temperature of the soaking zone of the heating furnace is controlled at 1280-1285°C, and the conditions for the ingot to be taken out of the heating furnace must meet the following conditions: the time in the furnace is ≥200min and the pure time in the furnace is ≥100min, where: The time in the furnace is the sum of the time the billet spends in the preheating zone, heating zone and soaking zone. Pure furnace time is the sum of the furnace time of the billet in the heating zone and the soaking zone; S3: rough rolling the ingot for 7 passes using a rough rolling mill; S4: The cast billet after rough rolling is subjected to 5 to 7 passes of finishing rolling by using a Steckel mill, wherein: The finishing temperature of the Steckel mill is controlled at 980-1000℃; The rolling speed of the last pass of the finishing mill is controlled at 210-320 mpm, and the billet is cooled after sufficient recrystallization time is given. The recrystallization time of the billet is controlled at 7-10 seconds. S5: The finished rolled ingot is quickly and evenly cooled to 500°C at a rate of 23-25°C / S by laminar water cooling and then coiled; S6: pickling the austenitic stainless steel to obtain an austenitic stainless steel coil.

2. The process for in-line solution annealing of austenitic stainless steel according to claim 1, characterized in that: In S2, the preheating zone of the heating furnace includes two temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone in the preheating zone is controlled at 990°C, and the temperature of the second temperature zone in the preheating zone is controlled at 1130°C; the heating zone of the heating furnace includes four temperature zones arranged in sequence along the conveying direction of the ingot, the temperature of the first temperature zone in the heating zone is controlled at 1175°C, the temperature of the second temperature zone in the heating zone is controlled at 1245°C, the temperature of the third temperature zone in the heating zone is controlled at 1270°C, and the temperature of the fourth temperature zone in the heating zone is controlled at 1280°C.

3. The process for in-line solution annealing of austenitic stainless steel according to claim 1, characterized in that: In S4, the temperatures in the inlet coil furnace and the outlet coil furnace of the Steckel mill are both controlled at 1060°C.

4. The process for in-line solution annealing of austenitic stainless steel according to claim 1, characterized in that: In S4, the rolling speed of the last finishing pass of the finishing mill of the Steckel mill is controlled at 320 mpm, and the recrystallization time of the ingot is controlled at 8 s.

Images