Process for manufacturing a ferritic stainless steel and use thereof

Abstract

The application belongs to the technical field of heat treatment, and particularly relates to a manufacturing process of ferritic stainless steel and application thereof. The manufacturing process of ferritic stainless steel comprises the following steps: S1, steelmaking: smelting steelmaking raw materials to obtain molten steel; the steelmaking raw materials comprise molten iron raw materials and chromium molten iron raw materials; the weight percentage of P element in the molten iron raw materials is less than or equal to 0.025%, and the weight percentage of S element is less than or equal to 0.025%; the feeding temperature of the molten iron raw materials is 1300-1500 DEG C; the content of Cr in the chromium molten iron raw materials is 40-60% of the total mass of the chromium molten iron raw materials; the feeding temperature of the chromium molten iron raw materials is 1450-1650 DEG C; S2, continuous casting; S3, hot rolling; and S4, warehousing. The manufacturing process of ferritic stainless steel can significantly reduce power consumption, fuel consumption and carbon emission while keeping the uniformity of the obtained product, mechanical properties and corrosion resistance stable.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology, specifically relating to a manufacturing process for ferritic stainless steel and its application. Background Technology

[0002] As a key functional component of kitchen appliances, gas stove panels are widely used in household and commercial cooktops, integrated cooktops, and countertop stoves. They require materials with high resistance to high temperatures, oxidation, corrosion, and processing. Traditional gas stove panels are mostly made of tempered glass or glass-ceramic materials. While these materials are aesthetically pleasing and have excellent heat resistance, they suffer from high costs, poor impact resistance, and complex processing, hindering the mass production and promotion of cost-effective products.

[0003] As the kitchen appliance industry moves towards high cost-effectiveness, long lifespan, and green manufacturing, metal gas stove panels are gradually becoming a new application trend. Among them, 430 ferritic stainless steel stands out in gas stove materials due to its excellent corrosion resistance, oxidation resistance, thermal conductivity, and significant cost advantages. Compared with carbon steel, its surface is more stable in high-temperature oil fume and humid steam environments, and it is less prone to rusting; compared with austenitic stainless steel, it has lower cost, better forming rigidity, and dimensional stability, making it suitable for economical and high-volume gas stove products, achieving a good balance between performance and economy. Driven by the "dual-carbon" strategy and green manufacturing goals, the kitchen appliance and stainless steel industries have placed higher demands on energy conservation, carbon reduction, and efficient manufacturing. The current 430 stainless steel production process usually relies on a high proportion of cold materials and multi-stage heat treatment, resulting in high energy consumption, limited thermal energy utilization efficiency, and insufficient temperature connection between processes, causing serious waste of heat energy between smelting and hot rolling.

[0004] Therefore, there is an urgent need to develop a ferritic stainless steel manufacturing process that can effectively reduce production energy consumption. Summary of the Invention

[0005] This invention aims to provide a manufacturing process for ferritic stainless steel and its applications. The manufacturing process for ferritic stainless steel of this invention achieves integrated utilization of thermal energy and unified microstructure control throughout the entire process of smelting, continuous casting, and hot rolling. While maintaining the uniformity of microstructure, stable mechanical properties, and corrosion resistance of the produced product, it significantly reduces power consumption, fuel consumption, and carbon emissions, and has good prospects for widespread application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a manufacturing process for ferritic stainless steel, comprising the following steps: S1. Steelmaking: Smelting raw materials for steelmaking to produce molten steel; The steelmaking raw materials include molten iron and molten chromium iron. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1300~1500℃. The Cr content in the molten chromium raw material is 40-60% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1450-1650℃; S2, continuous casting; S3, hot-rolled; S4. Inventory entry.

[0007] The ferritic stainless steel described in this invention is 430 ferritic stainless steel.

[0008] As one embodiment of the present invention, the steelmaking process in step S1 includes the following steps: adding steelmaking raw materials into an AOD furnace for decarburization and desulfurization, and then refining and fine-tuning them to the required composition in an LF furnace to obtain molten steel.

[0009] In one embodiment of the present invention, the amount of molten chromium raw material fed is 40±5% of the total mass of the furnace charge.

[0010] In one embodiment of the present invention, the steelmaking raw materials also include scrap steel, and the proportion of scrap steel added is 15% to 45% of the total mass of the furnace charge.

[0011] In this invention, the addition of scrap steel can effectively regulate the temperature during the steelmaking process and dilute the composition of the raw materials.

[0012] In one embodiment of the present invention, the continuous casting in step S2 is as follows: the molten steel obtained in step S1 is produced using a slab continuous casting machine; the casting speed during the continuous casting process is controlled at 0.8 to 1.0 m / min, the water content in the secondary cooling zone is 1.0 to 1.2 L / kg, and the slab thickness is 220 to 250 mm.

[0013] In this invention, the thickness of the slab is controlled to be 220~250 mm, which has higher heat capacity and heat preservation performance compared with conventional thin slabs. It can effectively maintain the offline temperature and provide a good temperature reserve and structural stability basis for subsequent hot rolling and through-type thermal control processes.

[0014] As one embodiment of the present invention, the PA value of the molten steel is detected during the continuous casting process to keep the PA value within the range of 43 to 52. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements.

[0015] The PA value mentioned in this invention refers to the austenite forming ability parameter, which is a comprehensive index measuring the influence of alloying elements on the proportion of high-temperature austenite in steel, and is used to characterize the comprehensive influence of alloying elements on the stability of high-temperature austenite. The PA value is calculated by comprehensively considering the contents of stabilizing ferrite elements such as Cr, Si, and Mo, and stabilizing austenite elements such as C, N, and Ni. Its value range directly affects the austenite volume fraction and phase transformation behavior during hot working. Controlling the PA value between 43 and 52 can keep the high-temperature austenite volume fraction within a suitable range, avoiding excessive austenitization and cooling during hot rolling to form martensite, which ultimately affects the quality of the steel coil.

[0016] In one embodiment of the present invention, the temperature of the billet in the continuous casting process is 400-900°C.

[0017] In one embodiment of the present invention, immediately after the billet comes off the production line, a hot billet surrounding process is employed, in which the billet is surrounded by a hot billet at a temperature not lower than 400°C, with the overall cooling rate controlled at 20–30°C / h. By employing this hot billet surrounding process immediately after the billet comes off the production line, the present invention effectively maintains a balanced temperature field and promotes grain homogenization, thereby significantly improving the quality of the resulting steel coil.

[0018] As one embodiment of the present invention, the hot rolling includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling and coiling; The roughing speed is 0.8~1.2m / s and the rolling time is 65-75s; the finishing speed is 8~12m / s and the rolling time is 65-75s.

[0019] The termination temperature of the laminar flow cooling is 880±20℃.

[0020] In one embodiment of the present invention, the billet is heated at a temperature of 1250±30℃.

[0021] In one embodiment of the present invention, the descaling conditions are: a furnace back pressure of 20-25 MPa and a speed of 0.7-1.0 m / s.

[0022] In one embodiment of the present invention, the post-furnace pressure of the rough rolling mill is 20~25MPa, and it undergoes 1~3 descaling passes.

[0023] In one embodiment of the present invention, the coil is immediately subjected to heat preservation treatment after winding, so that the wound steel coil is in a heat preservation environment of 600-700°C for 48-72 hours until the core temperature of the steel coil naturally cools down to below 200-400°C, and then it is taken out.

[0024] In one embodiment of the present invention, the heat preservation treatment involves suspending the steel coil into a through-type thermal stacking system for heat preservation. The through-type thermal stacking system of the present invention refers to forming a closed thermal field around the steel coil by arranging hot coils at ≥600℃, thereby achieving the heat preservation effect.

[0025] This invention optimizes the laminar cooling and coiling stages in the manufacturing process, controlling the roughing and finishing rolling times to 65-75 seconds and the laminar cooling termination temperature to 880±20℃. It implements a combination of high-temperature coiling and through-type thermal control processes to ensure stable grain transformation, prevent coarsening and embrittlement of the microstructure caused by excessively rapid cooling, and provide a suitable initial microstructure for warehousing.

[0026] The billet heating, descaling, rough rolling, finish rolling, laminar flow cooling, and coiling (the coiling process should ensure that the coiling machine does not leak water) described in this invention are all well-known operating methods in the art.

[0027] This invention, through the synergistic interaction between various steps in the continuous casting and hot rolling processes, effectively suppresses martensite formation in 430 ferritic stainless steel during cooling, significantly reducing the risk of microstructure embrittlement, resulting in more uniform grain distribution and simultaneous performance improvement. Stable microstructure and excellent mechanical-corrosion resistance matching can be obtained without the need for bag-type annealing (BAF), achieving the effect of annealing substitution.

[0028] As one embodiment of the present invention, the criterion for warehousing is as follows: Warehousing and entry into the cold rolling process are permitted only when the following three conditions are simultaneously met: ① PA value is in the range of 43 to 52; ② Hot rolling process parameters meet the standards (laminar cooling termination temperature controlled at 880±20℃); ③ The through-type thermal control process is completed, that is, after hot rolling is put into storage, it is kept at the temperature in the through-type hot stacking area for ≥48~72 hours, and the core temperature is ≤400℃ when it is taken out; If any of the above conditions are not met, it is necessary to switch to the traditional bell-type annealing (BAF) mode for supplementary treatment to ensure that the mechanical properties, corrosion resistance and other properties of the final product meet the corresponding requirements.

[0029] The present invention also claims protection for the application of a manufacturing process for the ferritic stainless steel in the preparation of ferritic stainless steel products; the ferritic stainless steel products include gas stove panels and other products that are sensitive to thermal stability and cost.

[0030] Compared with the prior art, the present invention has the following beneficial effects: In the steelmaking stage, the manufacturing process of this invention utilizes steelmaking raw materials at higher temperatures for smelting. It leverages the residual heat of liquid metal to reduce the addition of solidified cold materials and the energy consumption for melting, while simultaneously reducing the load on dephosphorization, desulfurization, and deep refining, thus decreasing electricity consumption and carbon emissions. Furthermore, in the continuous casting and hot rolling stages, a continuous thermal process replaces the traditional bell-type annealing process, effectively saving annealing energy consumption and gas costs per ton of steel. In summary, this invention's manufacturing process, while maintaining the uniformity of the microstructure, mechanical properties, and corrosion resistance of 430 stainless steel, can achieve a total cost reduction of approximately USD 50.3 per ton of steel, significantly enhancing its competitiveness in the steelmaking market. It also effectively improves thermal efficiency, reduces energy consumption and carbon emissions, achieving a synergistic optimization of energy conservation and carbon reduction.

[0031] The manufacturing process of this invention enables the product to have both performance stability and economic competitiveness in the fields of gas stoves and low-to-mid-range kitchen appliance materials, and has good prospects for promotion and application. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the hot blank surrounding coverage process described in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram of the through-type thermal stacking system described in an embodiment of the present invention.

[0034] Figure 3 This is a schematic diagram of the salt spray resistance test results of an embodiment of the present invention. Detailed Implementation

[0035] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0036] Unless otherwise specified, the experimental methods used in the examples and comparative examples are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0037] Example 1 A manufacturing process for ferritic stainless steel includes the following steps: S1. Steelmaking: Steelmaking raw materials are added to an AOD furnace for decarburization and desulfurization, followed by refining and fine-tuning to the required composition in an LF furnace to obtain molten steel; specifically including the following operations: (1) Steelmaking raw materials are simultaneously injected into the AOD furnace, with a furnace temperature ≥1400℃, and the furnace temperature is maintained at 1550~1650℃. The low oxygen top blowing intensity is 700~1000Nm³ / h, and the time is 15~30min to achieve rapid decarburization. (2) Desulfurization period: CaO-SiO2 slag system is used to control the alkalinity at 2.0~4.0 to ensure that the sulfur removal rate is ≥85% and reduce the subsequent refining load; (3) Refining and composition fine-tuning (LF furnace): Control the temperature at 1500-1580℃, add lime for desulfurization again, and adjust the composition to C≤0.050%, N≤0.050%, O≤0.004% to obtain molten steel; The steelmaking raw materials include molten iron, molten chromium iron, and scrap steel. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1400℃. The Cr content in the molten chromium raw material is 50% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1550℃; The feed amount of the molten chromium raw material is 40% of the total mass of the furnace charge; the proportion of scrap steel added is 30% of the total mass of the furnace charge.

[0038] S2. Continuous casting: The molten steel obtained in step S1 is produced using a slab continuous casting machine. The casting speed of the slab continuous casting machine is controlled at 0.9 m / min, the water content in the secondary cooling zone is 1.0 L / kg, and the slab thickness is 220 mm. PA value is tested on the molten steel during continuous casting, and the PA value is set to 50. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements. The continuous casting process uses a billet that is 700°C at the bottom of the casting line. See Figure 1 After the billet comes off the production line, a hot billet surrounding process is immediately adopted, in which the billet is surrounded by a hot billet at a temperature of not less than 400°C, and the overall cooling rate is controlled at 25°C / h.

[0039] S3. Hot rolling: includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling and coiling; The billet is heated to 1250℃; The descaling conditions are a furnace back pressure of 25 MPa and a speed of 0.8 m / s; The roughing mill has a furnace pressure of 25 MPa and undergoes two descaling passes. The roughing mill has a rolling speed of 1.0 m / s and a rolling time of 70 s; the finishing mill has a rolling speed of 10 m / s and a rolling time of 70 s. The termination temperature of the laminar flow cooling is 880°C; See Figure 2 Immediately after winding, the steel coil is hoisted into a through-type hot stacking system for heat preservation. By arranging hot coils at ≥600℃ around the steel coil, a closed hot field is formed, so that the wound steel coil is in a heat preservation environment of 640℃ for 48 hours until the core temperature of the steel coil naturally cools down to below 200-400℃, and then it is taken out.

[0040] S4. Inventory entry.

[0041] Example 2 A manufacturing process for ferritic stainless steel includes the following steps: S1. Steelmaking: Steelmaking raw materials are added to an AOD furnace for decarburization and desulfurization, followed by refining and fine-tuning to the required composition in an LF furnace to obtain molten steel; specifically including the following operations: (1) Steelmaking raw materials are simultaneously injected into the AOD furnace, with a furnace temperature ≥1400℃, and the furnace temperature is maintained at 1550~1650℃. The low oxygen top blowing intensity is 700~1000Nm³ / h, and the time is 15~30min to achieve rapid decarburization. (2) Desulfurization period: CaO-SiO2 slag system is used to control the alkalinity at 2.0~4.0 to ensure that the sulfur removal rate is ≥85% and reduce the subsequent refining load; (3) Refining and composition fine-tuning (LF furnace): Control the temperature at 1500-1580℃, add lime for desulfurization again, and adjust the composition to C≤0.050%, N≤0.050%, O≤0.004% to obtain molten steel; The steelmaking raw materials include molten iron, molten chromium iron, and scrap steel. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1400℃. The Cr content in the molten chromium raw material is 40% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1450℃. The feed amount of the molten chromium raw material is 45% of the total mass of the furnace charge; the proportion of scrap steel added is 15% of the total mass of the furnace charge.

[0042] S2. Continuous casting: The molten steel obtained in step S1 is produced using a slab continuous casting machine. The casting speed of the slab continuous casting machine is controlled at 0.8 m / min, the water content in the secondary cooling zone is 1.0 L / kg, and the slab thickness is 220 mm. PA value is tested on the molten steel during continuous casting, and the PA value is set to 45. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements. The continuous casting process uses a billet with a final run-off temperature of 400°C. Immediately after the billet comes off the production line, a hot billet surrounding process is adopted, in which the billet is surrounded by a hot billet at a temperature of not less than 400°C, and the overall cooling rate is controlled at 20°C / h.

[0043] S3. Hot rolling: includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling and coiling; The billet is heated to 1280℃; The descaling conditions are a furnace back pressure of 25 MPa and a speed of 1.0 m / s; The roughing mill has a furnace pressure of 25 MPa and undergoes three descaling passes. The roughing mill has a rolling speed of 0.8 m / s and a rolling time of 65 s; the finishing mill has a rolling speed of 8 m / s and a rolling time of 65 s. The termination temperature of the laminar flow cooling is 890°C; Immediately after winding, the steel coil is hoisted into a through-type thermal stacking system for heat preservation. By arranging hot coils at ≥600℃ around the steel coil, a closed thermal field is formed, so that the wound steel coil is in a heat preservation environment of 600℃ for 64 hours until the core temperature of the steel coil naturally cools down to below 200-400℃, and then it is taken out.

[0044] S4. Inventory entry.

[0045] Example 3 A manufacturing process for ferritic stainless steel includes the following steps: S1. Steelmaking: Steelmaking raw materials are added to an AOD furnace for decarburization and desulfurization, and then refined and finely adjusted to the required composition in an LF furnace to obtain molten steel. This process includes the following steps: (1) Steelmaking raw materials are simultaneously injected into the AOD furnace, with a furnace temperature ≥1400℃, and the furnace temperature is maintained at 1550~1650℃. The low oxygen top blowing intensity is 700~1000Nm³ / h, and the time is 15~30min to achieve rapid decarburization. (2) Desulfurization period: CaO-SiO2 slag system is used to control the alkalinity at 2.0~4.0 to ensure that the sulfur removal rate is ≥85% and reduce the subsequent refining load; (3) Refining and composition fine-tuning (LF furnace): Control the temperature at 1500-1580℃, add lime for desulfurization again, and adjust the composition to C≤0.050%, N≤0.050%, O≤0.004% to obtain molten steel; The steelmaking raw materials include molten iron, molten chromium iron, and scrap steel. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1500℃. The Cr content in the molten chromium raw material is 60% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1650℃; The feed amount of the molten chromium raw material is 35% of the total mass of the furnace charge; the proportion of scrap steel added is 45% of the total mass of the furnace charge.

[0046] S2. Continuous casting: The molten steel obtained in step S1 is produced using a slab continuous casting machine. The casting speed of the slab continuous casting machine is controlled at 1.0 m / min, the water content in the secondary cooling zone is 1.2 L / kg, and the slab thickness is 220 mm. PA value was tested on the molten steel during continuous casting, and the PA value was set to 52. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements. The minimum casting temperature of the billet in the continuous casting process is 900℃; Immediately after the billet comes off the production line, a hot billet surrounding process is adopted, in which the billet is surrounded by a hot billet at a temperature of not less than 400°C, and the overall cooling rate is controlled at 30°C / h.

[0047] S3. Hot rolling: includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling and coiling; The billet is heated to 1220℃; The descaling conditions are a furnace back pressure of 20 MPa and a speed of 0.7 m / s; The roughing mill has a furnace pressure of 20 MPa and undergoes one descaling pass. The roughing mill has a rolling speed of 1.2 m / s and a rolling time of 75 s; the finishing mill has a rolling speed of 12 m / s and a rolling time of 75 s. The termination temperature of the laminar flow cooling is 860°C; Immediately after winding, the steel coil is hoisted into a through-type thermal stacking system for heat preservation. By arranging hot coils at ≥600℃ around the steel coil, a closed thermal field is formed, so that the wound steel coil is in a heat preservation environment of 700℃ for 72 hours until the core temperature of the steel coil naturally cools down to below 200-400℃, and then it is taken out.

[0048] S4. Inventory entry.

[0049] Example 4 A manufacturing process for ferritic stainless steel includes the following steps: S1. Steelmaking: Steelmaking raw materials are added to an AOD furnace for decarburization and desulfurization, and then refined and finely adjusted to the required composition in an LF furnace to obtain molten steel. This process includes the following steps: (1) Steelmaking raw materials are simultaneously injected into the AOD furnace, with a furnace temperature ≥1400℃, and the furnace temperature is maintained at 1550~1650℃. The low oxygen top blowing intensity is 700~1000Nm³ / h, and the time is 15~30min to achieve rapid decarburization. (2) Desulfurization period: CaO-SiO2 slag system is used to control the alkalinity at 2.0~4.0 to ensure that the sulfur removal rate is ≥85% and reduce the subsequent refining load; (3) Refining and composition fine-tuning (LF furnace): Control the temperature at 1500-1580℃, add lime for desulfurization again, and adjust the composition to C≤0.050%, N≤0.050%, O≤0.004%; The steelmaking raw materials include molten iron, molten chromium iron, and scrap steel. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1400℃. The Cr content in the molten chromium raw material is 50% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1550℃; The feed amount of the molten chromium raw material is 40% of the total mass of the furnace charge; the proportion of scrap steel added is 30% of the total mass of the furnace charge.

[0050] S2. Continuous casting: The molten steel obtained in step S1 is produced using a slab continuous casting machine. The casting speed of the slab continuous casting machine is controlled at 0.9 m / min, the water content in the secondary cooling zone is 1.0 L / kg, and the slab thickness is 220 mm. PA value is tested on the molten steel during continuous casting, and the PA value is set to 50. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements. The continuous casting process uses a billet that is 700°C at the bottom of the casting line. Immediately after the billet comes off the production line, a hot billet surrounding process is adopted, in which the billet is surrounded by a hot billet at a temperature of not less than 400°C, and the overall cooling rate is controlled at 50°C / h.

[0051] S3. Hot rolling: includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling and coiling; The billet is heated to 1250℃; The descaling conditions are a furnace back pressure of 25 MPa and a speed of 0.8 m / s; The roughing mill has a furnace pressure of 25 MPa and undergoes two descaling passes. The roughing mill has a rolling speed of 1.0 m / s and a rolling time of 70 s; the finishing mill has a rolling speed of 10 m / s and a rolling time of 70 s. The termination temperature of the laminar flow cooling is 880°C; Immediately after winding, the steel coil is hoisted into a through-type thermal stacking system for heat preservation. By arranging hot coils at ≥600℃ around the steel coil, a closed thermal field is formed, so that the wound steel coil is in a heat preservation environment of 640℃ for 48 hours until the core temperature of the steel coil naturally cools down to below 200-400℃, and then it is taken out.

[0052] S4. Inventory entry.

[0053] The only difference between this embodiment and Embodiment 1 is that the hot billet is immediately covered around the billet after it comes off the production line, and the overall cooling rate is controlled at 50℃ / h.

[0054] Comparative Example 1 The only difference between this comparative example and Example 1 is that the PA value of the molten steel was tested during the continuous casting process, and the PA value was 55.

[0055] Other manufacturing processes are the same as in Example 1.

[0056] Comparative Example 2

[0057] The only difference between this comparative example and Example 1 is that the heat preservation time of the steel coil after winding is 20 hours.

[0058] Other manufacturing processes are the same as in Example 1.

[0059] Comparative Example 3 The only difference between this comparative example and Example 1 is that the laminar flow cooling termination temperature is 720°C.

[0060] Other manufacturing processes are the same as in Example 1.

[0061] Comparative Example 4 The only difference between this comparative example and Example 1 is that no heat preservation treatment is performed after winding.

[0062] Other manufacturing processes are the same as in Example 1.

[0063] Comparative Example 5 The difference between this comparative example and Example 1 is that the feeding temperature of the molten iron raw material in the steelmaking process in step S1 is 1000℃; the feeding temperature of the ferrochrome raw material is room temperature.

[0064] Other manufacturing processes are the same as in Example 1.

[0065] Experimental Example 1: Comparison of Inclusions The inclusions in the steel coils produced by the manufacturing process according to the embodiment were compared and analyzed with those produced by the conventional bell-type annealing process.

[0066] Comparative analysis revealed that the 430 ferritic stainless steel hot-rolled coils prepared using the manufacturing process of this invention have the same inclusion characteristics as conventional uncoiling coils. The types, size distributions, and contents of inclusions are not significantly different, and no large particles or concentrated inclusions were detected. This indicates that the low-carbon through-flow hot process will not introduce additional inclusions or affect the cleanliness of the material.

[0067] Experiment Example 2: Performance Testing (1) Mechanical property testing Test method: Yield strength, tensile strength and elongation: tested according to the mechanical properties of metallic materials "Tension testing - Part 1: Test method at room temperature" in GB / T 228.1—2021 standard.

[0068] Rockwell hardness: Tested in accordance with GB / T 230.1—2018 "Metallic materials Rockwell hardness test - Part 1: Test method".

[0069] Test samples: steel coils prepared according to the manufacturing methods of Examples 1-4 and Comparative Examples 1-5, and steel coils prepared by conventional bell-type annealing process.

[0070] The test results are shown in Table 1.

[0071] Table 1 Test results for each group

[0072] As can be seen from the experimental results in Table 1, in the manufacturing process of this embodiment of the invention, when the PA value is in the range of 43 to 52, the termination temperature of laminar cooling (i.e., the winding temperature) is 880±20℃ and the holding time is ≥48h, the yield strength of the material is about 270~295MPa, the tensile strength is about 470~490MPa, the Rockwell hardness HRB is about 76~82, the elongation is maintained at 25%~32%, the overall performance is stable and the cold rolling and calendering properties are good.

[0073] Compared to Example 1, Comparative Example 1 had an unsuitable PA value in its manufacturing process, resulting in poor yield strength and tensile strength of the produced steel coil. Furthermore, its adaptability to cold rolling was poor, and the cold-rolled product failed to meet standard requirements. In Comparative Example 2, the holding time of the coil after coiling was 20 hours, which was too short, significantly deteriorating the yield strength and elongation of the produced steel coil, and resulting in excessively high strength, making the cold-rolled product unable to meet standard requirements. In Comparative Example 3, the laminar flow cooling termination temperature (i.e., coiling temperature) was 720°C, resulting in steel coils with improved yield strength and tensile strength. The strength and other properties deteriorated, and the adaptability of cold rolling was poor, with the mill load exceeding the design value by 15%. In Comparative Example 4, no heat preservation treatment was used after the coiling operation, resulting in a significant deterioration in yield strength and elongation. Furthermore, the adaptability of cold rolling was poor, and problems such as "high hardness at the head and tail and difficulty in rolling" occurred during the cold rolling process. In Comparative Example 5, the feeding temperature of the molten iron and ferrochrome raw materials was unsuitable, or room temperature feeding was used (most major steel mills in China use high-carbon ferrochrome cold materials, which are melted in an induction furnace during production). Although the performance of the steel coils produced met the corresponding requirements, the final production cost increased significantly.

[0074] Compared with conventional bell-type annealing, the products manufactured by the process of this invention are basically equivalent to those of traditional bell-type annealed products in terms of mechanical properties. The Rockwell hardness (HRB) of both is at a similar level, the strength distribution is relatively uniform, and no obvious difference in hardness is observed; the elongation also remains within the same range, and the plasticity and toughness of the materials are stable.

[0075] (2) Salt spray resistance The test method is in accordance with GB / T 10125-1997 Artificial Atmosphere Corrosion Test - Salt Spray Test, and the results are evaluated in accordance with GB / T 6461-2002 Rating of Specimens and Test Pieces of Metals and Other Inorganic Coatings on Metal Substrates after Corrosion Test.

[0076] The test items, test standard requirements, and experimental values ​​are shown in Table 2: Table 2 Test Items, Test Standards, and Experimental Values

[0077] Test samples: steel coils manufactured by the process of Example 1 of this invention and steel coils manufactured by conventional bell annealing.

[0078] Test results are as follows Figure 3 As shown.

[0079] from Figure 3 The experimental results show that the steel coils produced by the manufacturing process of the present invention have excellent corrosion resistance stability in a neutral salt spray environment. After 96 hours of neutral salt spray testing, no corrosion, rust spots or peeling were observed on the sample surface.

[0080] This demonstrates that the ferritic stainless steel manufacturing process of the present invention can significantly reduce energy consumption and carbon emissions while maintaining corrosion resistance comparable to that of the traditional bell-type annealing process, fully meeting the requirements for materials used in gas stove panels.

[0081] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A manufacturing process for ferritic stainless steel, characterized in that, Includes the following steps: S1. Steelmaking: Smelting raw materials for steelmaking to produce molten steel; The steelmaking raw materials include molten iron and molten chromium iron. The weight percentage of phosphorus (P) and sulfur (S) in the molten iron raw material is ≤0.025% and ≤0.025% respectively; the feeding temperature of the molten iron raw material is 1300~1500℃. The Cr content in the molten chromium raw material is 40-60% of the total mass of the molten chromium raw material; the feeding temperature of the molten chromium raw material is 1450-1650℃; S2, continuous casting; S3, hot-rolled; S4. Inventory entry.

2. The manufacturing process of ferritic stainless steel as described in claim 1, characterized in that, The steelmaking process described in step S1 includes the following steps: adding steelmaking raw materials into an AOD furnace for decarburization and desulfurization, followed by refining and fine-tuning in an LF furnace to achieve the desired composition, thereby obtaining molten steel.

3. The manufacturing process of ferritic stainless steel as described in claim 1, characterized in that, The feed amount of the molten chromium raw material is 40±5% of the total mass of the furnace charge; the steelmaking raw materials also include scrap steel, and the proportion of scrap steel added is 15% to 45% of the total mass of the furnace charge.

4. The manufacturing process of ferritic stainless steel as described in claim 2, characterized in that, The continuous casting in step S2 is as follows: the molten steel obtained in step S1 is produced using a slab continuous casting machine; the casting speed during the continuous casting process is controlled at 0.8 to 1.0 m / min, the water content in the secondary cooling zone is 1.0 to 1.2 L / kg, and the slab thickness is 220 to 250 mm.

5. The manufacturing process of ferritic stainless steel as described in claim 4, characterized in that, PA value is tested during continuous casting to keep the PA value within the range of 43 to 52. The formula for calculating the PA value is as follows: PA = 189 + 470 * N + 420 * C + 23 * Ni + 9 * Cu + 7 * Mn - 11.5 * Cr - 11.5 * Si - 12 * Mo - 23 * V - 47 * Nb - 49 * Ti - 52 * Al, where N, C, Ni, Cu, Mn, Cr, Si, Mo, V, Nb, Ti, and Al refer to the weight percentage values ​​of the corresponding metallic elements.

6. The manufacturing process of ferritic stainless steel as described in claim 4, characterized in that, The continuous casting process involves casting billets at a temperature of 400–900°C. Immediately after the billet comes off the production line, a hot billet surrounding process is adopted, in which the billet is surrounded by a hot billet at a temperature of not less than 400°C, and the overall cooling rate is controlled at 20-30°C / h.

7. The manufacturing process of ferritic stainless steel as described in claim 1, characterized in that, The hot rolling process includes the following steps: billet heating, descaling, rough rolling, finish rolling, laminar flow cooling, and coiling; The roughing speed is 0.8~1.2m / s and the rolling time is 65-75s; the finishing speed is 8~12m / s and the rolling time is 65-75s. The termination temperature of the laminar flow cooling is 880±20℃.

8. The manufacturing process of ferritic stainless steel as described in claim 7, characterized in that, Immediately after winding, the coil is kept in a heat-preserving environment of 600-700°C for 48-72 hours until the core temperature of the coil naturally cools down to below 200-400°C.

9. The manufacturing process of ferritic stainless steel as described in claim 8, characterized in that, The insulation process involves suspending the steel coil into a continuous thermal stacking system for insulation.

10. The application of a manufacturing process for ferritic stainless steel as described in any one of claims 1 to 9 in the preparation of ferritic stainless steel products, characterized in that, The ferritic stainless steel products include gas stove panels.

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