Method for low temperature rollability treatment of thick gauge 430 ferritic stainless steel laser welds

Abstract

The application discloses a kind of thick gauge 430 ferritic stainless steel laser weld low-temperature rollability processing method, comprising: using-1~‑2mm negative defocusing+8~10kW low-power laser welding, the grain of heat-affected zone is refined;NiCr-3 welding wire is preheated to 300~400℃ and carried out hot wire laser welding, reduces cooling rate;Weld is implemented 700 DEG C / 10-12 seconds short time induction annealing, decomposes martensite and releases residual stress;Weld is inducted to ≥50 DEG C before rolling and restores plasticity;Optimize five rack continuous rolling parameter, and the reduction of first rack is reduced to 15%-20%.The application is by welding-heat treatment-rolling whole process synergic control, makes weld low-temperature cracking rate from 2.6 times / month reduce to 1 times below, and-10 DEG C impact toughness is promoted to 22J, cup convexity qualification rate reaches 95%, and annual economic benefit is greatly improved, applicable to the thickness 3.0~8.0mm 430 stainless steel cold rolling production, solves the technical problem that thick gauge 430 stainless steel weld is easy to crack under low-temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel rolling technology, and particularly relates to a method for low-temperature rollability treatment of laser weld seams in thick 430 ferritic stainless steel. Background Technology

[0002] 430 ferritic stainless steel is widely used in cold rolling production due to its excellent corrosion resistance and processing performance. However, in the low-temperature environment of northern winters (-5℃ to -10℃), 430 stainless steel strips with a thickness of ≥4.5mm, after traditional laser welding, frequently experience cracking and even strip breakage in the weld area during cold continuous rolling. Statistics show that the weld cracking rate under traditional processes is as high as 2.6 times per month, with each failure taking 3-6 hours to resolve, resulting in significant economic losses and safety hazards.

[0003] The existing technology has the following drawbacks: 1. Grain coarsening in the heat-affected zone: Traditional 12kW laser welding causes the peak temperature of the heat-affected zone (HAZ) to exceed 1100℃, the grain size to reach more than 200μm, the ductile-brittle transition temperature (DBTT) to drop below room temperature, and the impact toughness at -10℃ is only 5~10J, which is far lower than the 20~30J of the base material. 2. Martensitic phase transformation problem: Rapid cooling after welding leads to the formation of continuous martensitic structure near the fusion line, and the hardness increases sharply to 380~450HV, forming a significant hardness gradient with the base material of 190~220HV, which causes stress concentration. 3. Excessive residual stress: The welding cooling process generates residual stress with a peak value of 280MPa. At low temperatures, the material has poor plasticity (elongation of only 8%), making it impossible to effectively release the stress. 4. Low-temperature performance degradation: The pass rate of weld cup protrusion at room temperature is only 10%, which is far lower than the 90% pass rate at hot (60℃). Existing processes cannot solve the problem of rapid performance degradation at low temperatures. The bottlenecks of existing technologies are: single process adjustments (such as welding parameter optimization) cannot simultaneously achieve microstructure refinement and stress control; heat treatment processes are difficult to balance martensite decomposition and grain refinement in a short time; rolling parameter optimization lacks a synergistic mechanism with welding processes; and temperature compensation measures are insufficient in low-temperature environments. Therefore, there is an urgent need to develop a multi-dimensional collaborative control technology that forms a closed-loop control from welding process optimization, heat treatment strengthening, temperature compensation to rolling parameter collaborative adjustment, to break through the low-temperature rollability bottleneck of 430 stainless steel welds and ensure the continuity of cold rolling production and the stability of product quality. Summary of the Invention

[0004] To at least partially solve the technical problems existing in the prior art, the present invention provides a method for low-temperature rollability treatment of laser weld seams of 430mm thick ferritic stainless steel.

[0005] The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds of the present invention includes the following steps: Laser welding: A negative defocus + low laser power welding method is adopted, and the laser welding defocus is adjusted to a negative defocus of -1mm to -2mm, so that the spot energy density reaches 200W / mm². 2 ~300W / mm 2 Meanwhile, the laser power is reduced to 8kW~10kW, and the heat input is reduced by 30%~40% while maintaining the penetration depth, and the weld is laser welded. Hot wire laser welding: Apply an external power source to the front end of the welding wire to preheat the NiCr-3 welding material to 300℃~400℃, set the heating current to 28A~30A, and perform hot wire laser welding on the weld. Short-time induction annealing: A 200KW induction heating device is used to rapidly heat the weld to 700℃ and hold it for 10~12 seconds to decompose martensite and release residual stress. Pre-rolling induction heating: A medium-frequency induction coil with a frequency of 10kHz and a power density of 5~8kW / m is installed in front of the No. 3 tension roll of the cold continuous rolling mill. 2 When the strip passes through at a speed of 20m / min, the weld temperature rises from room temperature to no less than 50℃; Coordinated adjustment of rolling parameters: reduce the reduction rate of the first stand of the five-stand continuous rolling mill to 15%~20%, and appropriately increase the reduction rate of subsequent stands, while keeping the total reduction rate unchanged; at the same time, adjust the inlet tension, inter-stand tension and rolling speed.

[0006] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick-gauge 430 ferritic stainless steel, the thickness of the thick-gauge 430 ferritic stainless steel is ≥4.5mm.

[0007] Furthermore, in the above-mentioned method for treating the low-temperature rollability of laser welds on thick 430 ferritic stainless steel, in the laser welding step, the welding speed of the negative defocusing + low laser power welding is 2 m / min, and the welding cooling rate is 10 m / min. 3 The grain size of the heat-affected zone is refined to 50~80μm at ℃ / s, and the hardness of the fusion line is controlled at 280~320HV.

[0008] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick 430 ferritic stainless steel, in the hot-wire laser welding step, the wire feeding speed of the hot-wire laser welding is 7 m / min, the length of the heating zone is 0.1 m, and the effective time for the welding wire to pass through the heating zone is 0.857 seconds; the diameter of the NiCr-3 welding material is 0.9 mm, the resistance at room temperature is 1.04 μΩ·m, and the resistance rises to 2.07 μΩ·m at 300℃.

[0009] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser welds of thick 430 ferritic stainless steel, in the short-time induction annealing step, the 700℃ short-time induction annealing is controlled by a closed-loop infrared thermometer to ensure that the weld temperature deviation is ≤±5℃, so that the martensite decomposition rate reaches 85%, the residual stress is reduced by 40%~50%, and the grain size of the heat-affected zone is stabilized at 80~100μm.

[0010] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of 430 thick ferritic stainless steel, in the pre-rolling induction heating step, the pre-rolling induction heating device is a solid-state induction heating power supply circuit structure. The AC power frequency voltage is rectified into pulsating DC by a rectifier bridge, and then inverted into square wave voltage and sinusoidal current by an inverter after passing through an LC filter circuit and output to the resonant groove circuit, and finally applied to the induction coil to heat the strip steel.

[0011] Furthermore, in the above-mentioned method for treating the low-temperature rollability of laser weld seams in thick 430 ferritic stainless steel, the coordinated adjustment of rolling parameters in the rolling parameter adjustment step specifically includes: increasing the inlet tension of the first stand by 5% to 10%; reducing the rolling speed of the weld area by 20% to 50% when the workshop temperature is below 0℃; and simultaneously adjusting the bending roll force and the position of the shifting roll to compensate for the plate shape deviation caused by the change in reduction rate.

[0012] Furthermore, the above-mentioned method for treating the low-temperature rollability of laser welds in thick 430 ferritic stainless steel also includes an ambient temperature compensation step: when the workshop temperature is below -5℃, the pre-rolling heating temperature is increased to 65℃, and the rolling speed is further reduced by 15%.

[0013] Furthermore, the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick 430 ferritic stainless steel also includes a wire matching optimization step: dynamically adjusting the hot wire current ±2A when the C content of different batches of base material fluctuates within the range of 0.08%~0.12%.

[0014] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick 430 ferritic stainless steel, for thick 430 ferritic stainless steel strips with a thickness range of 3.0~8.0mm, the negative defocusing amount is dynamically adjusted according to the formula d=-0.3×t+0.2. Where t is the strip thickness, in mm; When the Cr content of the base material fluctuates by ±0.5%, the induction annealing temperature is corrected according to the formula T=700+10×(Cr%-17).

[0015] The low-temperature rollability treatment method for thick 430 ferritic stainless steel laser welds of the present invention has the following advantages and beneficial effects: This invention forms a systematic solution through a closed-loop synergy of welding energy control, heat treatment microstructure optimization, pre-rolling temperature compensation, and rolling parameter adjustment. This reduces the low-temperature cracking rate of welds from 2.6 times / month to below 1 time / month, improving overall performance by more than 40%; the weld cupping qualification rate increases from 10% to 95%; the -10℃ low-temperature impact toughness increases from 5~10J to 22J, approaching the level of the base material; the grain size of the heat-affected zone is refined from over 200μm to 50~80μm, the martensite content is significantly reduced, and the hardness gradient is smoother; effectively reducing downtime, reducing scrap coil losses, saving waste costs, and improving annual economic benefits. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only for further understanding of the embodiments of the present invention and constitute a part of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 The images show a comparison of the microstructure of the weld seam, where a is the weld seam structure of the traditional process (200μm coarse grains + continuous martensite), and b is the weld seam structure of the present invention (65μm fine grains + dispersed carbides). Figure 2 This is a hardness distribution diagram of the present invention, where a is a hardness gradient distribution curve of the weld and b is a hardness gradient distribution curve of the base material. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0018] The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds of the present invention includes the following steps: Laser welding: A negative defocus + low laser power welding method is adopted, and the laser welding defocus is adjusted to a negative defocus of -1mm to -2mm, so that the spot energy density reaches 200W / mm². 2 ~300W / mm 2Simultaneously, the laser power is reduced to 8kW~10kW, reducing heat input by 30%~40% while maintaining the penetration depth. The welding speed of the negative defocusing + low laser power welding is 2m / min, and the welding cooling rate is 10. 3 The temperature of the weld seam was increased by ℃ / s, which extended the transformation time window from austenite to ferrite, suppressed the formation of martensite, refined the grain size of the heat-affected zone to 50~80μm, controlled the hardness of the fusion line to 280~320HV, made the gradient distribution more gentle, reduced the local stress concentration factor, and laser welded the weld seam, which significantly improved the low-temperature crack resistance of the 430 stainless steel weld seam. Hot-wire laser welding: An external power source is applied to the front end of the welding wire to preheat the NiCr-3 welding material to 300℃~400℃, thereby supplementing heat to the molten pool, slowing down the weld cooling rate, inhibiting the formation of brittle phases such as martensite, promoting ferrite transformation, and improving weld toughness. The heating current is set to 28A~30A. The wire feeding speed of the hot-wire laser welding is 7m / min, the heating zone length is 0.1m, and the effective time for the welding wire to pass through the heating zone is 0.857 seconds. The diameter of the NiCr-3 welding material is 0.9mm, the resistance is 1.04μΩ·m at room temperature, and the resistance rises to 2.07μΩ·m at 300℃. Hot-wire laser welding is then performed on the weld. Short-time induction annealing: A 200KW induction heating device is used to rapidly heat the weld to 700℃ and hold it for 10-12 seconds. The 700℃ setting activates the decomposition of martensite into ferrite + carbides, reducing the hardness from 380~450HV to 280~320HV. After a short holding time, an incomplete annealed structure is formed, retaining some fine carbide phases to balance hardness and toughness. The 700℃ short-time induction annealing is controlled by a closed-loop infrared thermometer to ensure that the weld temperature deviation is ≤±5℃, achieving a martensite decomposition rate of 85% and reducing residual stress by 40%~50%, thereby reducing the stress concentration factor. The grain size in the heat-affected zone is stabilized at 80~100μm, promoting martensite decomposition and residual stress release, while inhibiting grain coarsening and improving the low-temperature toughness of the weld. Short-time induction annealing works in conjunction with laser welding and hot-wire laser welding. Through negative defocusing and low-power welding, low heat input reduces martensite formation. Annealing further eliminates residual hard phases. After preheating the welding wire with hot-wire laser welding to reduce the cooling rate, annealing supplements stress release, forming a two-stage regulation. Pre-rolling induction heating: A medium-frequency induction coil with a frequency of 10kHz and a power density of 5~8kW / m is installed in front of the No. 3 tension roll of the cold continuous rolling mill. 2 When the strip passes through at a speed of 20 m / min, the weld temperature rises from room temperature to no less than 50°C, which exceeds the ductile-brittle transition temperature (DBTT) of the material to restore its plastic deformation capacity, while reducing the temperature stress during the rolling process and avoiding cracking. Coordinated adjustment of rolling parameters: The reduction rate of the first stand of the five-stand continuous rolling mill is reduced to 15%~20%, and the reduction rate of subsequent stands is appropriately increased, while the total reduction rate remains unchanged; at the same time, the inlet tension, inter-stand tension and rolling speed are adjusted. Specifically, the coordinated adjustment of rolling parameters is as follows: the inlet tension of the first stand is increased by 5%~10%; when the workshop temperature is below 0℃, the rolling speed in the weld area is reduced by 20%~50%; at the same time, the bending roll force and the position of the shifting roll are adjusted to compensate for the shape deviation caused by the change in reduction rate.

[0019] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick-gauge 430 ferritic stainless steel, the thickness of the thick-gauge 430 ferritic stainless steel is ≥4.5mm.

[0020] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of 430 thick ferritic stainless steel, in the pre-rolling induction heating step, the pre-rolling induction heating device is a solid-state induction heating power supply circuit structure. The AC power frequency voltage is rectified into pulsating DC by a rectifier bridge, and then inverted into square wave voltage and sinusoidal current by an inverter after passing through an LC filter circuit and output to the resonant groove circuit, and finally applied to the induction coil to heat the strip steel.

[0021] Furthermore, the above-mentioned method for treating the low-temperature rollability of laser welds in thick 430 ferritic stainless steel also includes an ambient temperature compensation step: when the workshop temperature is below -5℃, the pre-rolling heating temperature is increased to 65℃, and the rolling speed is further reduced by 15%.

[0022] Furthermore, the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick 430 ferritic stainless steel also includes a wire matching optimization step: dynamically adjusting the hot wire current ±2A when the C content of different batches of base material fluctuates within the range of 0.08%~0.12%.

[0023] Furthermore, in the above-mentioned method for low-temperature rollability treatment of laser weld seams of thick 430 ferritic stainless steel, for thick 430 ferritic stainless steel strips with a thickness range of 3.0~8.0mm, the negative defocusing amount is dynamically adjusted according to the formula d=-0.3×t+0.2. Where t is the strip thickness, in mm; When the Cr content of the base material fluctuates by ±0.5%, the induction annealing temperature is corrected according to the formula T=700+10×(Cr%-17).

[0024] Example 1 The following welding and cold rolling process is performed on 14.5mm thick 430 stainless steel: Laser welding: A negative defocus + low laser power welding method was adopted, with the defocus amount set to -1.5mm, laser power 9kW, welding speed 2m / min, heat input reduced by 37.5%, and cooling rate reduced to 10. 3 ℃ / s, heat-affected zone width reduced by 40%, grain size refined to 65μm, fusion line hardness 300HV.

[0025] Hot wire laser welding: NiCr-3 welding material (diameter 0.9mm) is selected, wire feed speed is 7m / min, heating current is 29A, welding wire preheating temperature is 350℃, the fluidity of the molten pool is significantly improved, and the porosity of the weld is reduced to below 0.1%.

[0026] Short-time induction annealing: A 200KW induction heating device is used, the heating temperature is 700℃, the holding time is 11 seconds, the temperature deviation is controlled by an infrared thermometer within ±3℃, the martensite decomposition rate is 85%, and the residual stress is reduced by 45%.

[0027] Pre-rolling induction heating: Medium-frequency induction coil frequency 10kHz, power density 6kW / m 2 The strip speed is 20m / min, the weld temperature is raised to 60℃, and the elongation is increased to 16%.

[0028] Rolling parameter adjustments: The reduction rate of the first stand of the five-stand continuous rolling mill was adjusted to 18%, and the inlet tension was increased from 80kN to 88kN; when the workshop temperature was below 0℃, the rolling speed was reduced from 30m / min to 15m / min; in conjunction with the adjustment of the bending roll force, the plate shape deviation was controlled within ±5μm.

[0029] The specific rolling parameters at different workshop temperatures are shown in Tables 1 and 2, where Table 1 is for workshop temperatures above 0℃ and Table 2 is for workshop temperatures below 0℃. Table 1

[0030] Table 2

[0031] In summary, compared with existing technologies, the low-temperature rollability treatment method for thick 430 ferritic stainless steel laser welds of the present invention has the following advantages and beneficial effects: The present invention forms a systematic solution through closed-loop synergy of welding energy control → heat treatment microstructure optimization → pre-rolling temperature compensation → rolling parameter adjustment, reducing the low-temperature cracking rate of welds from 2.6 times / month to less than 1 time / month, and improving the overall performance by more than 40%; the weld cupping qualification rate increases from 10% to 95%, and the -10℃ low-temperature impact toughness increases from 5-10J to 22J, approaching the level of the base material; the grain size of the heat-affected zone is refined from more than 200μm to 50-80μm, the martensite content is significantly reduced, and the hardness gradient is more gradual; effectively reducing downtime, reducing scrap coil losses, saving waste costs, and improving annual economic benefits.

[0032] It should be noted that, unless otherwise expressly specified and limited, the term "connection" or its synonyms should be interpreted broadly in this document. For example, "connection" can be a fixed connection or a detachable connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Furthermore, expressions such as "first" and "second" are merely used to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Meanwhile, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. In addition, the terms "front," "rear," "left," "right," "upper," and "lower" in this document refer to the placement states shown in the accompanying drawings.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for low-temperature rollability treatment of laser weld seams in 430mm thick ferritic stainless steel, characterized in that, Includes the following steps: Laser welding: A negative defocus + low laser power welding method is adopted, and the laser welding defocus is adjusted to a negative defocus of -1mm to -2mm, so that the spot energy density reaches 200W / mm². 2 ~300W / mm 2 Meanwhile, the laser power is reduced to 8kW~10kW, and the heat input is reduced by 30%~40% while maintaining the penetration depth, and the weld is laser welded. Hot wire laser welding: Apply an external power source to the front end of the welding wire to preheat the NiCr-3 welding material to 300℃~400℃, set the heating current to 28A~30A, and perform hot wire laser welding on the weld. Short-time induction annealing: A 200KW induction heating device is used to rapidly heat the weld to 700℃ and hold it for 10~12 seconds to achieve martensite decomposition and residual stress release; Pre-rolling induction heating: A medium-frequency induction coil with a frequency of 10kHz and a power density of 5~8kW / m is installed in front of the No. 3 tension roll of the cold continuous rolling mill. 2 When the strip passes through at a speed of 20m / min, the weld temperature rises from room temperature to no less than 50℃; Coordinated adjustment of rolling parameters: reduce the reduction rate of the first stand of the five-stand continuous rolling mill to 15%~20%, and appropriately increase the reduction rate of subsequent stands, while keeping the total reduction rate unchanged; at the same time, adjust the inlet tension, inter-stand tension and rolling speed.

2. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds according to claim 1, characterized in that, The thickness of the 430 ferritic stainless steel is ≥4.5mm.

3. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds according to claim 1, characterized in that, In the laser welding step, the welding speed of the negative defocusing + low laser power welding is 2 m / min, and the welding cooling rate is 10. 3 The grain size of the heat-affected zone is refined to 50~80μm at ℃ / s, and the hardness of the fusion line is controlled at 280~320HV.

4. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser weld seams according to claim 1, characterized in that, In the hot-wire laser welding step, the wire feeding speed is 7 m / min, the heating zone length is 0.1 m, and the effective time for the welding wire to pass through the heating zone is 0.857 seconds; the NiCr-3 welding material has a diameter of 0.9 mm, a resistance of 1.04 μΩ·m at room temperature, and a resistance that rises to 2.07 μΩ·m at 300 °C.

5. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds according to claim 1, characterized in that, In the short-time induction annealing step, the 700℃ short-time induction annealing is controlled by a closed-loop infrared thermometer to ensure that the weld temperature deviation is ≤±5℃, so that the martensite decomposition rate reaches 85%, the residual stress is reduced by 40%~50%, and the grain size of the heat-affected zone is stabilized at 80~100μm.

6. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser welds according to claim 1, characterized in that, In the pre-rolling induction heating step, the pre-rolling induction heating device is a solid-state induction heating power supply circuit structure. The AC power frequency voltage is rectified into pulsating DC by the rectifier bridge, and then inverted into square wave voltage and sinusoidal current by the inverter after passing through the LC filter circuit. The output is then sent to the resonant groove circuit and finally applied to the induction coil to heat the strip.

7. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser weld seams according to claim 1, characterized in that, In the rolling parameter coordination adjustment step, the rolling parameter coordination adjustment specifically includes: increasing the inlet tension of the first stand by 5% to 10%; reducing the rolling speed of the weld area by 20% to 50% when the workshop temperature is below 0℃; and simultaneously adjusting the bending roll force and the position of the shifting roll to compensate for the plate shape deviation caused by the change in the reduction rate.

8. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser weld seams according to claim 1, characterized in that, It also includes an ambient temperature compensation step: when the workshop temperature is below -5℃, the pre-rolling heating temperature is increased to 65℃, and the rolling speed is further reduced by 15%.

9. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser weld seams according to claim 1, characterized in that, It also includes a wire matching optimization step: dynamically adjusting the hot wire current ±2A when the C content of the base material fluctuates within the range of 0.08%~0.12% in different batches.

10. The method for low-temperature rollability treatment of thick 430 ferritic stainless steel laser weld seams according to claim 1, characterized in that, For thick 430 ferritic stainless steel strips with a thickness range of 3.0~8.0mm, the negative decoking amount is dynamically adjusted according to the formula d=-0.3×t+0.2; Where t is the strip thickness, in mm; When the Cr content of the base material fluctuates by ±0.5%, the induction annealing temperature is corrected according to the formula T=700+10×(Cr%-17).

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