Stainless steel precision strip for automobile decoration strip and processing technology of stainless steel precision strip

Abstract

The invention discloses a stainless steel precision strip for an automobile trim strip and a processing technology of the stainless steel precision strip, and relates to the technical field of stainless steel precision strip production, the stainless steel precision strip comprises the following chemical components in percentage by weight: 0.01-0.03% of C, 0.25-0.45% of Si, 0.5-1% of Mn, 18-20% of Cr, 9-11% of Ni, 1.8-3.2% of Mo, 0.06-0.12% of V, 0.3-0.5% of Cu, 0.1-0.3% of Ti, 0.03-0.08% of Nb, 0.01-0.03% of Y, 0.05-0.12% of Ta, 0.04-0.1% of Hf, and the balance of iron and inevitable impurity elements. The stainless steel precision strip has high surface quality, high corrosion resistance and excellent toughness.

Description

Technical Field

[0001] This invention relates to the field of stainless steel precision strip manufacturing technology, and in particular to a stainless steel precision strip for automotive trim strips and its processing technology. Background Technology

[0002] As an important component of automotive exterior design, automotive trim strips not only serve a decorative purpose but also must withstand the corrosive effects of complex outdoor environments, requiring high dimensional accuracy and surface quality. Stainless steel strip, due to its excellent corrosion resistance, gloss, and mechanical strength, has become a core raw material for automotive trim strips. However, existing stainless steel strips used in automotive trim strips are gradually revealing insufficient corrosion resistance. In harsh environments such as high temperature and humidity, and coastal salt spray, traditional stainless steel strips are prone to pitting corrosion and rust spots, leading to cosmetic failure and shortened service life. Furthermore, the surface roughness of currently available stainless steel strips is typically greater than 0.3μm, resulting in insufficient surface gloss and failing to meet the quality requirements of high-end automotive exterior components.

[0003] To address the aforementioned issues, invention patent document CN114147064B discloses a stainless steel precision strip for automotive trim strips and its processing technology, including multiple raw material precision rolling, finished product solution annealing, and stretching straightening processes, yielding a steel strip with a finished thickness of 0.3–0.6 mm and a surface roughness Ra of 0.1–0.2 μm. The flatness, surface gloss, and surface hardness of the obtained steel strip all meet the requirements. However, it does not optimize the alloy system for extreme working conditions such as high-temperature salt spray and low-temperature environments, and the surface treatment still relies on traditional mechanical polishing, making it difficult to meet the upgraded requirements of high-end automotive trim strips for long service life, high toughness, and efficient production.

[0004] Therefore, developing a stainless steel precision strip for automotive trim strips with high surface quality, high corrosion resistance, and suitability for direct stamping, as well as its processing technology, is of great practical significance. Summary of the Invention

[0005] The main objective of this invention is to overcome the above-mentioned shortcomings and provide a stainless steel precision strip for automotive trim strips with high surface quality, high corrosion resistance, and excellent toughness, as well as its processing technology.

[0006] To achieve the above objectives, the present invention provides a stainless steel precision strip for automotive trim strips, the chemical composition of which, by weight percentage, is: C: 0.01-0.03%, Si: 0.25-0.45%, Mn: 0.5-1%, Cr: 18-20%, Ni: 9-11%, Mo: 1.8-3.2%, V: 0.06-0.12%, Cu: 0.3-0.5%, Ti: 0.1-0.3%, Nb: 0.03-0.08%, Y: 0.01-0.03%, Ta: 0.05-0.12%, Hf: 0.04-0.1%, with the remainder being iron and unavoidable impurity elements.

[0007] Another object of the present invention is to provide a processing technology for the stainless steel precision strip for automotive trim strips, comprising the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.1-0.2 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.7-1.0 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1180-1220℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 35-65m / min, and strip with a thickness of 0.5-1.2mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0008] Preferably, the initial smelting temperature in the electric arc furnace in step S1 is 1620-1660℃.

[0009] Preferably, in step S1, the vacuum degree is maintained at no more than 30 Pa during the VD vacuum degassing process, and the heat preservation time is 40-50 minutes; the RH vacuum cycle degassing time is no less than 20 minutes.

[0010] Preferably, the pulse voltage of the pulsed electric field in step S1 is 800-1200V, the frequency is 50-80Hz, it acts on the crystallizer region, and the duration is 10-15s / s / s of the billet section.

[0011] Preferably, the thickness of the billet in step S1 is 130-160 mm.

[0012] Preferably, in step S2, the initial rolling temperature is ≥1100℃, the final rolling temperature is 820-860℃, and the reduction rate is 75-80%.

[0013] Preferably, the magnetic field strength of the pulsed magnetic field in step S2 is 0.3-0.5T, the frequency is 30-50Hz, and it acts on the roll exit area.

[0014] Preferably, the annealing in step S2 is carried out in a hydrogen-protected annealing furnace, with an annealing temperature of 1080-1120℃, a holding time of 120-160 min, and then air cooling after furnace cooling to 650℃.

[0015] Preferably, the total cold rolling reduction rate in step S3 is 85-90%, and the reduction rates for each pass are 40-45%, 25-30%, 15-20%, 5-8%, and 2-3%, respectively.

[0016] Preferably, the strategy for dynamic oil temperature closed-loop control is: the oil temperature for the first pass is 40-45℃, and the oil temperature for the subsequent four passes is 50-55℃.

[0017] Preferably, the annealing treatment in step S4 specifically comprises: a first stage of heating from room temperature to 800°C at a heating rate of 4-6°C / min and holding for 40-60 minutes to eliminate stress generated during cold rolling; a second stage of heating from 800°C to 1080-1120°C at a heating rate of 2-3°C / min and holding for 120-160 minutes to promote the full and uniform diffusion of alloying elements; a third stage of cooling from 1080-1120°C to 650°C at a cooling rate of 3-5°C / min and holding for 50-70 minutes to achieve grain refinement; and a fourth stage of furnace cooling from 650°C to room temperature.

[0018] Preferably, the straightening speed in step S5 is 18-22 m / min, and the straightening roller pressure is 10-14 MPa; the tensioning and straightening process is implemented as an integrated operation of tensioning, bending and straightening, and the tension rate is controlled at 1.0-1.5%.

[0019] Preferably, the electrolyte for electropolishing in step S6 includes: 90-110 g / L phosphoric acid, 40-60 g / L sulfuric acid, and 15-25 g / L citric acid.

[0020] Preferably, the electropolishing temperature in step S6 is 55-65℃, the current density is 20-30 A / dm², and the time is maintained for 4-6 minutes.

[0021] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The stainless steel precision strip for automotive trim disclosed in this invention has the following chemical composition by weight percentage: C: 0.01-0.03%, Si: 0.25-0.45%, Mn: 0.5-1%, Cr: 18-20%, Ni: 9-11%, Mo: 1.8-3.2%, V: 0.06-0.12%, Cu: 0.3-0.5%, Ti: 0.1-0.3%, Nb: 0.03-0.08%, Y: 0.01-0.03%, Ta: 0.05-0.12%, Hf: 0.04-0.1%, with the remainder being iron and unavoidable impurity elements. Through the synergistic effect of the various components, the resulting stainless steel precision strip simultaneously possesses high surface quality, high corrosion resistance, and excellent toughness. Through an innovative alloy design of "Mo-Ta synergistic strengthening + Ti-Nb-Hf composite carbon fixation", Mo and Ta form a MoO3-Ta2O3 composite structure in the passivation film, which improves its resistance to high-temperature degradation; at the same time, Ti, Nb, Hf preferentially combine with C to form highly stable composite carbides, which completely inhibits Cr. 23 C6 precipitation at grain boundaries. Combined with continuous casting pulsed electric field to refine grains, this further reduces corrosion pathways.

[0022] (2) The stainless steel precision strip for automotive trim disclosed in this invention utilizes a synergistic scheme of "high Ni stable austenite + V-Ti-Y grain refinement + hot rolling pulse magnetic field assistance"; the Ni content of 9.0-11.0% effectively suppresses martensite transformation at low temperature, and V, Ti and Y together control grain size and reduce stress concentration; a 0.3-0.5T pulse magnetic field is applied during the hot rolling stage to reduce deformation stress through magnetoplastic effect and avoid microstructure inhomogeneity; for the first time, the synergistic unity of "high strength-high toughness" in low temperature environment is achieved, breaking through the performance bottleneck of traditional processes.

[0023] (3) The stainless steel precision strip for automotive trim disclosed in this invention utilizes an integrated "alloy purity control + electropolishing" scheme. The Y element and Ca-Si alloy work synergistically to reduce the content of inclusions and avoid surface protrusions caused by inclusions. Electropolishing employs a phosphoric acid-sulfuric acid-citric acid composite electrolyte (citric acid inhibits excessive corrosion) to achieve a mirror finish. At the same time, the integrated "hot rolling-annealing" reduces process transfer losses and improves overall processing efficiency. For the first time, it achieves compatibility between "mirror-level surface quality" and "high-efficiency large-scale production," resolving the long-standing contradiction between efficiency and quality that has plagued the industry.

[0024] (4) The stainless steel precision strip for automotive trim disclosed in this invention is precisely controlled by “five-stage gradient cold rolling + dynamic oil temperature closed-loop control + laser thickness measurement feedback straightening”. In the cold rolling stage, the gradient reduction rate is distributed as 40-45% → 25-30% → 15-20% → 5-8% → 2-3%, and the dynamic oil temperature control is “40-45℃ for the first pass (anti-sticking roller) and 50-55℃ for the next four passes (to improve precision)” to avoid thinning at the edges. In the finishing stage, a composite scheme of twenty-roll straightening (pressure 10-14MPa) + laser thickness measurement + 1.0-1.5% tension straightening rate is adopted. The combined effect effectively reduces the rework rate, improves the production qualification rate, and significantly improves the stability and economy of mass production. Detailed Implementation

[0025] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. Example 1

[0026] A stainless steel precision strip for automotive trim has the following chemical composition by weight percentage: C: 0.01%, Si: 0.25%, Mn: 0.5%, Cr: 18%, Ni: 9%, Mo: 1.8%, V: 0.06%, Cu: 0.3%, Ti: 0.1%, Nb: 0.03%, Y: 0.01%, Ta: 0.05%, Hf: 0.04%, with the remainder being iron and unavoidable impurity elements.

[0027] A processing method for the stainless steel precision strip used in automotive trim strips includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.1 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.7 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1180℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 35m / min, and a strip with a thickness of 0.5mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0028] The initial smelting temperature in the electric arc furnace in step S1 is 1620℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 40 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulsed electric field in step S1 is 800V, the frequency is 50Hz, it is applied to the crystallizer region, and the duration is 10s / s / slab section; the thickness of the slab in step S1 is 130mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 820℃, and the reduction rate is 75%.

[0029] The magnetic field strength of the pulsed magnetic field in step S2 is 0.3T, the frequency is 30Hz, and it acts on the roll exit area; the annealing in step S2 is carried out in a hydrogen-protected annealing furnace, the annealing temperature is 1080℃, the holding time is 120min, and it is cooled in the furnace to 650℃ and then air-cooled; the total cold rolling reduction rate in step S3 is 87%, and the reduction rates of each pass are 40%, 25%, 15%, 5%, and 2% respectively; the strategy of dynamic oil temperature closed-loop control is: the oil temperature of the first pass is 40℃, and the oil temperature of the next four passes is 50℃.

[0030] The annealing treatment in step S4 specifically comprises: The first stage involves heating from room temperature to 800℃ at a rate of 4℃ / min, holding for 40 minutes to eliminate stress generated during cold rolling; the second stage involves heating from 800℃ to 1080℃ at a rate of 2℃ / min, holding for 120 minutes to promote the full and uniform diffusion of alloying elements; the third stage involves cooling from 1080℃ to 650℃ at a rate of 3℃ / min, holding for 50 minutes to achieve grain refinement. The process involves four stages of furnace cooling from 650℃ to room temperature; the straightening speed in step S5 is 18 m / min, and the straightening roller pressure is 10 MPa; the tensioning and straightening process is an integrated operation of tensioning, bending, and straightening, with the tension rate controlled at 1.0%; the electrolyte for electropolishing in step S6 includes 90 g / L phosphoric acid, 40 g / L sulfuric acid, and 15 g / L citric acid; the electropolishing temperature in step S6 is 55℃, the current density is 20 A / dm², and the time is maintained for 4 minutes. Example 2

[0031] A stainless steel precision strip for automotive trim has the following chemical composition by weight percentage: C: 0.015%, Si: 0.3%, Mn: 0.6%, Cr: 18.5%, Ni: 9.5%, Mo: 2.2%, V: 0.07%, Cu: 0.35%, Ti: 0.15%, Nb: 0.05%, Y: 0.015%, Ta: 0.07%, Hf: 0.06%, with the remainder being iron and unavoidable impurity elements.

[0032] A processing method for the stainless steel precision strip used in automotive trim strips includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.13 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.8 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1190℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 45m / min, and a strip with a thickness of 0.7mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0033] The initial smelting temperature in the electric arc furnace in step S1 is 1630℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 43 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulsed electric field in step S1 is 900V, the frequency is 60Hz, it is applied to the crystallizer area, and the duration is 12s / s / slab section; the thickness of the slab in step S1 is 140mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 830℃, and the reduction rate is 76%.

[0034] The magnetic field strength of the pulsed magnetic field in step S2 is 0.35T, the frequency is 35Hz, and it acts on the roll exit area; the annealing in step S2 is carried out in a hydrogen-protected annealing furnace, the annealing temperature is 1090℃, the holding time is 130min, and it is cooled in the furnace to 650℃ and then air-cooled; the total cold rolling reduction rate in step S3 is 87%, and the reduction rates of each pass are 40%, 25%, 15%, 5%, and 2% respectively; the strategy of dynamic oil temperature closed-loop control is: the oil temperature of the first pass is 42℃, and the oil temperature of the next four passes is 52℃.

[0035] The annealing process described in step S4 is as follows: In the first stage, the temperature is raised from room temperature to 800℃ at a rate of 4.5℃ / min and held for 45 minutes to eliminate the stress generated during cold rolling; in the second stage, the temperature is raised from 800℃ to 1100℃ at a rate of 2.3℃ / min and held for 130 minutes to promote the full and uniform diffusion of alloying elements; in the third stage, the temperature is lowered from 1090℃ to 650℃ at a rate of 3.5℃ / min and held for 55 minutes to achieve grain refinement; and in the fourth stage, the temperature is cooled from 650℃ to room temperature in the furnace.

[0036] The straightening speed in step S5 is 19 m / min, and the straightening roller pressure is 12 MPa; the tensioning and straightening process is carried out in an integrated operation of tensioning, bending, and straightening, and the tension rate is controlled at 1.1%; the electrolyte for electropolishing in step S6 includes: 95 g / L phosphoric acid, 45 g / L sulfuric acid, and 17 g / L citric acid; the electropolishing temperature in step S6 is 57℃, the current density is 23 A / dm², and the time is maintained for 4.5 minutes. Example 3

[0037] A stainless steel precision strip for automotive trim has the following chemical composition by weight percentage: C: 0.02%, Si: 0.35%, Mn: 0.75%, Cr: 19%, Ni: 10%, Mo: 2.5%, V: 0.09%, Cu: 0.4%, Ti: 0.2%, Nb: 0.06%, Y: 0.023%, Ta: 0.09%, Hf: 0.07%, with the remainder being iron and unavoidable impurity elements.

[0038] A processing method for the stainless steel precision strip used in automotive trim strips includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.15 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.85 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1200℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 50m / min, and a strip with a thickness of 0.9mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0039] The initial refining temperature in the electric arc furnace in step S1 is 1640℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 45 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulse electric field in step S1 is 1000V, the frequency is 65Hz, it acts on the crystallizer area, and the duration is 13s / s / slab section; the thickness of the slab in step S1 is 145mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 840℃, and the reduction rate is 770%; the magnetic field strength of the pulse magnetic field in step S2 is 0.4T, the frequency is 40Hz, and it acts on the roll exit area.

[0040] The annealing in step S2 is carried out in a hydrogen-protected annealing furnace at a temperature of 1100℃ and a holding time of 140 min. After furnace cooling to 650℃, it is air-cooled. The total cold rolling reduction rate in step S3 is 87%, and the reduction rates of each pass are 40%, 25%, 15%, 5%, and 2%, respectively. The strategy for dynamic oil temperature closed-loop control is as follows: the oil temperature for the first pass is 43℃, and the oil temperature for the next four passes is 53℃.

[0041] The annealing treatment in step S4 specifically comprises: The first stage involves heating from room temperature to 800℃ at a rate of 5℃ / min, holding for 50 minutes to eliminate stress generated during cold rolling; the second stage involves heating from 800℃ to 1100℃ at a rate of 2.5℃ / min, holding for 140 minutes to promote the full and uniform diffusion of alloying elements; the third stage involves cooling from 1100℃ to 650℃ at a rate of 4℃ / min, holding for 60 minutes to achieve grain refinement. The process involves four stages of furnace cooling from 650℃ to room temperature; the straightening speed in step S5 is 20 m / min, and the straightening roller pressure is 12 MPa; the tensioning and straightening process is an integrated operation of tensioning, bending, and straightening, with the tension rate controlled at 1.3%; the electrolyte for electropolishing in step S6 includes: 100 g / L phosphoric acid, 50 g / L sulfuric acid, and 20 g / L citric acid; the electropolishing temperature in step S6 is 60℃, the current density is 25 A / dm², and the time is maintained for 5 minutes. Example 4

[0042] A stainless steel precision strip for automotive trim has the following chemical composition by weight percentage: C: 0.025%, Si: 0.4%, Mn: 0.9%, Cr: 19.5%, Ni: 10.5%, Mo: 3%, V: 0.1%, Cu: 0.45%, Ti: 0.25%, Nb: 0.07%, Y: 0.025%, Ta: 0.1%, Hf: 0.09%, with the remainder being iron and unavoidable impurity elements.

[0043] A processing method for the stainless steel precision strip used in automotive trim strips includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.18 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.9 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1210℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 60m / min, and a strip with a thickness of 1mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0044] The initial smelting temperature in the electric arc furnace in step S1 is 1650℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 48 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulsed electric field in step S1 is 1100V, the frequency is 75Hz, it is applied to the crystallizer region, and the duration is 14s / s of the billet section; the thickness of the billet in step S1 is 155mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 850℃, and the reduction... The rate is 79%; the magnetic field strength of the pulsed magnetic field in step S2 is 0.45T, the frequency is 45Hz, and it acts on the roll exit area; the annealing in step S2 is carried out in a hydrogen-protected annealing furnace, the annealing temperature is 1110℃, the holding time is 150min, and it is cooled in the furnace to 650℃ and then air-cooled; the total cold rolling reduction rate in step S3 is 87%, and the reduction rates of each pass are 40%, 25%, 15%, 5%, and 2% respectively; the strategy of dynamic oil temperature closed-loop control is: the oil temperature of the first pass is 44℃, and the oil temperature of the next four passes is 54℃.

[0045] The annealing treatment in step S4 specifically comprises: a first stage of heating from room temperature to 800℃ at a rate of 5.5℃ / min, holding for 55 minutes to eliminate stress generated during cold rolling; a second stage of heating from 800℃ to 1110℃ at a rate of 2.8℃ / min, holding for 150 minutes to promote the full and uniform diffusion of alloying elements; a third stage of cooling from 1110℃ to 650℃ at a rate of 4.5℃ / min, holding for 65 minutes to achieve grain refinement; and a fourth stage of furnace cooling from 650℃ to room temperature. The straightening speed in step S5 is 21 m / min, and the straightening roller pressure is 13 MPa. The tensioning process integrates stretching, bending, and straightening, with the stretching rate controlled at 1.4%. The electrolyte for electropolishing in step S6 includes 105 g / L phosphoric acid, 55 g / L sulfuric acid, and 23 g / L citric acid. The electropolishing temperature in step S6 is 63℃, and the current density is 28 kJ / L. A / dm², time maintained for 5.5 minutes. Example 5

[0046] A stainless steel precision strip for automotive trim has the following chemical composition by weight percentage: C: 0.03%, Si: 0.45%, Mn: 1%, Cr: 20%, Ni: 11%, Mo: 3.2%, V: 0.12%, Cu: 0.5%, Ti: 0.3%, Nb: 0.08%, Y: 0.03%, Ta: 0.12%, Hf: 0.1%, with the remainder being iron and unavoidable impurity elements.

[0047] A processing method for the stainless steel precision strip used in automotive trim strips includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.2 kg / ton of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 1.0 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1220℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 65m / min, and a strip with a thickness of 1.2mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

[0048] The initial smelting temperature in the electric arc furnace in step S1 is 1660℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 50 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulsed electric field in step S1 is 1200V, the frequency is 80Hz, it is applied to the crystallizer region, and the duration is 15s / s / slab section; the thickness of the slab in step S1 is 160mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 860℃, and the reduction... The rate is 80%; the magnetic field strength of the pulsed magnetic field in step S2 is 0.5T, the frequency is 50Hz, and it acts on the roll exit area; the annealing in step S2 is carried out in a hydrogen-protected annealing furnace, the annealing temperature is 1120℃, the holding time is 160min, and it is cooled in the furnace to 650℃ and then air-cooled; the total cold rolling reduction rate in step S3 is 87%, and the reduction rates of each pass are 40%, 25%, 15%, 5%, and 2% respectively; the strategy of dynamic oil temperature closed-loop control is: the oil temperature of the first pass is 45℃, and the oil temperature of the next four passes is 55℃.

[0049] The annealing treatment in step S4 specifically comprises: a first stage of heating from room temperature to 800℃ at a rate of 6℃ / min, holding for 60 minutes to eliminate stress generated during cold rolling; a second stage of heating from 800℃ to 1120℃ at a rate of 3℃ / min, holding for 160 minutes to promote the full and uniform diffusion of alloying elements; a third stage of cooling from 1120℃ to 650℃ at a rate of 5℃ / min, holding for 70 minutes to achieve grain refinement; and a fourth stage of furnace cooling from 650℃ to room temperature. The straightening speed in step S5 is 22 m / min, and the straightening roller pressure is 14 MPa. The tensioning process integrates stretching, bending, and straightening, with the stretching rate controlled at 1.5%. The electrolyte for electropolishing in step S6 includes 110 g / L phosphoric acid, 60 g / L sulfuric acid, and 25 g / L citric acid. The electropolishing temperature in step S6 is 65℃, and the current density is 30 kJ / L. A / dm², timed for 6 minutes.

[0050] Comparative Example 1 A precision stainless steel strip for automotive trim strips and its processing technology are basically the same as those in Example 1, except that the chemical composition of the precision stainless steel strip for automotive trim strips is the same as that of conventional 316L.

[0051] Comparative Example 2 A stainless steel precision strip for automotive trim and its processing technology are basically the same as those in Example 1, except that Nb, Y, Ta and Hf are not added.

[0052] Comparative Example 3 A precision stainless steel strip for automotive trim and its processing technology are basically the same as those in Example 1, except that no pulsed electric field is provided.

[0053] Comparative Example 4 A precision stainless steel strip for automotive trim and its processing technology are basically the same as those in Example 1, except that there is no electrolytic polishing process.

[0054] Comparative Example 5 A precision stainless steel strip for automotive trim and its processing technology are basically the same as those in Example 1, except that no pulsed magnetic field is provided.

[0055] To further illustrate the beneficial technical effects of the stainless steel precision strip for automotive trim strips involved in the various embodiments of the present invention, relevant performance tests were conducted on the stainless steel precision strip for automotive trim strips involved in Example 1 and Comparative Examples 1-5. The test results are shown in Table 1, and the test methods are as follows: (1) High temperature corrosion resistance: Refer to GB / T 10125-2021 to conduct a neutral salt spray test at 70℃ and record the time when pitting corrosion occurs. The larger the value, the better the high temperature corrosion resistance. (2) Low temperature toughness: Refer to GB / T 13239-2021 to conduct a bending test at -20℃ (R=1.0t) and observe whether cracking occurs.

[0056] (3) Mirror quality: Surface roughness is tested in accordance with GB / T 2523-2022.

[0057] As can be seen from Table 1, the stainless steel precision strip for automotive trim disclosed in the embodiments of the present invention has better corrosion resistance, low-temperature toughness and surface quality than the comparative product; the combined use of Nb, Y, Ta, Hf, pulsed electric field, electropolishing and pulsed magnetic field is beneficial to improving the above properties.

[0058] Table 1. Performance Test Results of Stainless Steel Precision Strip for Automotive Trim Strips project unit Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 corrosion resistance h 2170 1420 1830 1710 2150 1920 Low temperature toughness - No cracks cracking cracking cracking No cracks cracking roughness μm 0.02 0.08 0.05 0.04 0.18 0.04 The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. A stainless steel precision strip for automotive trim, characterized in that, Its chemical composition by weight percentage is as follows: C: 0.01-0.03%, Si: 0.25-0.45%, Mn: 0.5-1%, Cr: 18-20%, Ni: 9-11%, Mo: 1.8-3.2%, V: 0.06-0.12%, Cu: 0.3-0.5%, Ti: 0.1-0.3%, Nb: 0.03-0.08%, Y: 0.01-0.03%, Ta: 0.05-0.12%, Hf: 0.04-0.1%, with the remainder being iron and unavoidable impurity elements.

2. A processing method for stainless steel precision strip for automotive trim as described in claim 1, characterized in that, Includes the following steps: Step S1, Smelting and Casting: The smelting process adopts a five-step method: "electric arc furnace primary smelting + LF refining + VD vacuum degassing + RH vacuum degassing + continuous casting pulse electric field refinement". First, the primary smelting is carried out in an electric arc furnace. After entering the LF refining stage, 0.1-0.2 kg / ton of steel of Ca-Si alloy is added to remove inclusions. Then, VD vacuum degassing and RH vacuum circulation degassing are carried out in sequence. The continuous casting adopts "electromagnetic stirring + light reduction + pulse electric field" in combination, with a casting speed of 0.7-1.0 m / min to obtain the billet. Step S2, Hot Rolling-Annealing Integration: The billet is heated to 1180-1220℃ and held for 2 hours. The hot rolling-annealing integration process is carried out using the "single-segment hot rolling + pulse magnetic field assisted + online annealing" process. Step S3, Cold Rolling Shape Control: The cold rolling process of "five-segment gradient reduction + dynamic oil temperature closed-loop control" is used for cold rolling shape control. The rolling speed is 35-65m / min, and strip with a thickness of 0.5-1.2mm is produced. Step S4, Annealing: Annealing is carried out in four stages in a hydrogen-protected annealing furnace; Step S5, Precision Finishing: Precision finishing is carried out using a composite finishing method that combines 20-roll precision straightening, laser thickness measurement feedback, and precision tension straightening. Step S6, Mirror Finish: Mirror finish is achieved by electrolytic polishing.

3. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The initial refining temperature in the electric arc furnace in step S1 is 1620-1660℃; the vacuum degree is maintained at no more than 30Pa during the VD vacuum degassing process in step S1, and the holding time is 40-50 minutes; the RH vacuum circulation degassing time is no less than 20 minutes; the pulse voltage of the pulsed electric field in step S1 is 800-1200V, the frequency is 50-80Hz, it is applied to the crystallizer area, and the duration is 10-15s / s / s of the billet section.

4. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The thickness of the billet in step S1 is 130-160mm; the initial rolling temperature of the hot rolling in step S2 is ≥1100℃, the final rolling temperature is 820-860℃, and the reduction rate is 75-80%; the magnetic field strength of the pulsed magnetic field in step S2 is 0.3-0.5T, the frequency is 30-50Hz, and it acts on the roll exit area.

5. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The annealing described in step S2 is carried out in a hydrogen-protected annealing furnace at a temperature of 1080-1120℃ and a holding time of 120-160 min. After furnace cooling to 650℃, it is air-cooled.

6. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, In step S3, the total cold rolling reduction rate is 85-90%, and the reduction rates for each pass are 40-45%, 25-30%, 15-20%, 5-8%, and 2-3%, respectively. The strategy for dynamic oil temperature closed-loop control is: the oil temperature for the first pass is 40-45℃, and the oil temperature for the next four passes is 50-55℃.

7. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The annealing process described in step S4 is as follows: In the first stage, the temperature is raised from room temperature to 800℃ at a rate of 4-6℃ / min and held for 40-60 minutes to eliminate the stress generated during cold rolling; in the second stage, the temperature is raised from 800℃ to 1080-1120℃ at a rate of 2-3℃ / min and held for 120-160 minutes to promote the full and uniform diffusion of alloying elements; in the third stage, the temperature is lowered from 1080-1120℃ to 650℃ at a rate of 3-5℃ / min and held for 50-70 minutes to achieve grain refinement; and in the fourth stage, the temperature is cooled from 650℃ to room temperature in the furnace.

8. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The straightening speed in step S5 is 18-22 m / min, and the straightening roller pressure is 10-14 MPa; The tensioning and straightening process involves integrated stretching, bending, and straightening operations, with the stretching rate controlled at 1.0-1.5%.

9. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The electrolyte for electropolishing in step S6 includes: 90-110 g / L phosphoric acid, 40-60 g / L sulfuric acid, and 15-25 g / L citric acid.

10. The processing technology of stainless steel precision strip for automotive trim strips according to claim 2, characterized in that, The electropolishing process in step S6 is carried out at a temperature of 55-65℃, a current density of 20-30 A / dm², and a time of 4-6 minutes.