Corrosion-resistant cold-rolled steel sheet and method for manufacturing the same

Abstract

The present application relates to cold-rolled steel plate material technical field, disclose a kind of corrosion-resistant cold-rolled steel plate, by mass percent, its chemical composition includes: C:0.02~0.10%, Si:0.05~0.25%, Mn:0.10~1.0%, P≤0.020%, S≤0.020%, Als≥0.010%, Cu:0.10~0.50%, Sn:0.001~0.045%, Sb:0.001~0.045%, Cr:0.10~0.60%, Mo:0.03~0.20%, the balance is Fe and inevitable trace impurities.The present application further discloses a kind of preparation method of corrosion-resistant cold-rolled steel plate.The present application corrosion-resistant cold-rolled steel plate and preparation method thereof, by five-element composite corrosion-resistant system and six-stage gradient controllable annealing process synergy, build high stability composite protective layer, block the invasion of corrosive medium, synchronous grain refinement, release residual stress, realize the technical breakthrough of low cost, high salt fog resistance, high acid corrosion resistance, high forming precision and high mass production stability.

Description

Technical Field

[0001] This invention relates to the field of cold-rolled steel sheet material technology, specifically to a corrosion-resistant cold-rolled steel sheet and its preparation method. Background Technology

[0002] Currently, general-purpose cold-rolled steel sheets for structural applications are widely used in warehouse racking, equipment frames, outdoor light steel structures, and electromechanical cabinets. While stainless steel offers sufficient corrosion resistance, it is more expensive. Commercially available ordinary cold-rolled structural steel sheets are inexpensive, but they have poor matrix density, containing numerous inclusions and grain boundary corrosion sites. Under conditions of salt spray, humid atmospheres, diurnal temperature fluctuations, and slight dust and acid / alkali corrosion, they are highly susceptible to localized pitting corrosion, intergranular corrosion, and surface oxidation and peeling, leading to short service life of structural components and high maintenance and refurbishment costs.

[0003] Existing high corrosion-resistant structural steel plates often employ high-chromium, nickel, and molybdenum composite systems, resulting in high raw material costs, narrow smelting and rolling process windows, and low yields. This makes it difficult to meet the demands of large-volume, low-cost applications in civil structural components. Furthermore, traditional corrosion-resistant cold-rolled plates have the following shortcomings: 1) When only a single copper or copper-tin binary alloy system is used, the passivation film has poor stability, and chloride ions can easily penetrate the film layer and cause pitting corrosion. 2) The production process is crude, the residual stress of rolling is large, the springback deformation of the sheet metal after stamping and bending is obvious, and the assembly accuracy is insufficient. 3) The precipitation of alloying elements is difficult to control, and segregation and agglomeration are prone to occur, resulting in uneven corrosion resistance of the whole plate and poor batch stability.

[0004] Chinese patent (publication date: August 3, 2021, publication number: CN113201694A) discloses a method for producing high corrosion-resistant cold-rolled low-carbon steel, including controlling the composition of the cold-rolled low-carbon steel, the conductivity of the alkaline solution and electrolytic conductivity in the annealing furnace, and the temperature, belt speed, dew point, oxygen content, and hydrogen content of each section in the annealing furnace. The cold-rolled low-carbon steel produced by this process exhibits strong corrosion resistance and good corrosion resistance during subsequent use, such as being less prone to rust during body-in-white painting and achieving good painting results. However, this invention has the following drawbacks: 1) the produced cold-rolled steel sheet has insufficient salt spray resistance, making it difficult to resist long-term salt spray corrosion in storage and outdoor steel structures; 2) it does not employ a multi-element corrosion-resistant alloy synergistic system, resulting in limited resistance to chloride-containing environments.

[0005] Chinese Patent (Publication Date: April 16, 2019, Publication No.: CN109628840A) discloses a 550MPa grade cold-rolled corrosion-resistant duplex steel and its manufacturing method. The steel contains: C: 0.061%–0.083%, Si < 0.10%, Mn: 1.05%–1.39%, P ≤ 0.018%, S ≤ 0.006%, Als: 0.015%–0.045%, Cr: 0.45%–0.91%, Ni: 0.11%–0.19%, Cu: 0.27%–0.41%, Nb: 0.011%–0.029%, Ti: 0.015%–0.035%, Sb: 0.046%–0.099%. %, Sn: 0.034%~0.079%, Mo: 0.11%~0.19%, B: 0.0008%~0.0019%, Ca: 0.0008%~0.0030%, with the balance being iron and unavoidable impurities; 135~170mm billets are heated to 1228~1249℃, with a total furnace time not exceeding 110min, roughing temperature >1100℃, finishing rolling temperature 895~915℃, annealing at 790~820℃, and the steel plate has excellent corrosion resistance. However, the invention has the following drawbacks: 1) The alloy system contains a variety of precious metals and microalloying elements such as nickel, niobium, titanium, and boron, resulting in high raw material costs and making it difficult to meet the demand for low-cost mass production of civilian structural components; 2) The system is designed with dual-phase high strength as its main objective, but it is not suitable for hydrochloric acid corrosion and has poor adaptability to pickling environments; 3) The process window is narrow, and the hot rolling and annealing parameters are strictly required, which limits the yield.

[0006] Therefore, the industry urgently needs a cold-rolled steel sheet and its preparation method that, under the premise of controllable cost of ordinary cold-rolled structural steel, combines alloy system and refined preparation process to simultaneously possess salt spray resistance, acid corrosion resistance, intergranular corrosion resistance, and stable mechanical and forming properties. Summary of the Invention

[0007] To overcome the above-mentioned defects, this invention provides a corrosion-resistant cold-rolled steel sheet and its preparation method. By combining a Cu-Sn-Sb-Cr-Mo five-element composite corrosion-resistant system with a six-stage gradient controllable annealing process, a highly stable composite protective layer is constructed while controlling production costs. This layer blocks the intrusion of corrosive media, simultaneously refines grains, and releases residual stress, achieving a technological breakthrough in low cost, high salt spray resistance, high acid corrosion resistance, high forming precision, and high mass production stability.

[0008] To achieve the above objectives, the corrosion-resistant cold-rolled steel sheet designed in this invention has the following chemical composition by mass percentage: C: 0.02%~0.10%, Si: 0.05%~0.25%, Mn: 0.10%~1.0%, P≤0.020%, S≤0.020%, Als≥0.010%, Cu: 0.10%~0.50%, Sn: 0.001%~0.045%, Sb: 0.001%~0.045%, Cr: 0.10%~0.60%, Mo: 0.03%~0.20%, with the balance being Fe and unavoidable trace impurities.

[0009] The mechanisms of action of each alloying element in this invention are as follows: C element: Trace solid solution strengthens the ferrite matrix, improves the yield strength of the product, and avoids soft collapse and end face deformation of stamped parts; it is limited to the low carbon range to prevent the precipitation of cementite at grain boundaries, prevent the formation of galvanic corrosion between cementite and ferrite, and reduce the local corrosion rate; the carbon content is not higher than 0.10% to ensure that the plate does not crack when cold-bent at 180° and does not crack when matched with stamping.

[0010] Si element: assists in pre-deoxidation, reduces free oxygen in molten steel, and reduces internal pitting oxide inclusions (inclusions are the initial cause of salt spray pitting); slightly strengthens the matrix through solid solution without deteriorating plasticity; avoids the introduction of hard silicate inclusions into the plate surface due to high silicon content, and prevents the induction of early pitting corrosion.

[0011] Mn element: It fixes harmful sulfur elements, generates stable MnS spherical inclusions, replaces low melting point FeS. MnS has strong chemical inertness and does not participate in salt spray corrosion, avoiding FeS dissolution along grain boundaries and causing intergranular corrosion. At the same time, it refines hot-rolled grains, uniformizes matrix potential, and avoids galvanic corrosion caused by matrix potential difference. It also improves the cold stamping ductility of sheet metal.

[0012] Phosphorus (P) element: It tends to segregate at ferrite grain boundaries, reducing grain boundary bonding and increasing anodic dissolution rate. High-phosphorus plates will exhibit rapid edge corrosion and mottled corrosion on the surface under salt spray conditions. Therefore, its content must be strictly controlled to ensure uniform corrosion.

[0013] Sulfur (S) is the number one corrosive and harmful impurity in steel. Primary FeS has a low melting point and is distributed in a network along the grain boundaries during hot rolling. Chloride ions in salt spray preferentially corrode the network FeS, forming intergranular cracks and filamentous corrosion. Its content must be strictly controlled.

[0014] Als element: terminal deep deoxidation, eliminates free oxygen and micropore defects, and closes the micro-corrosion channels of the matrix; generates dispersed AlN precipitates, inhibits grain coarsening, and improves the uniformity of the structure; no excessive aluminum is added to avoid the hard inclusion of alumina from damaging the continuity of the passivation film.

[0015] Cu element: As a special anti-corrosion element for grain boundaries, when the steel substrate is anoly dissolved in a salt spray environment, copper ions are precipitated again at grain boundaries and plate defects, forming a rich layer of elemental copper. On the one hand, it reduces the corrosion current density of the substrate and slows down the overall corrosion rate; on the other hand, it seals grain boundary vacancies and blocks chloride ions from penetrating inward. Copper passivation film is loose when used alone, and must be used in combination with Cr and Mo.

[0016] Sn element: As an auxiliary element for copper film modification, trace amounts of tin are dissolved in the copper enrichment layer, which improves the adhesion and water resistance of the copper passivation film, solves the problem of peeling and detachment of pure copper film under alternating dry and wet salt spray, and eliminates localized delamination and pitting corrosion on the board surface; at the same time, it fills the microscopic scratches and defects of the substrate, improves the corrosion resistance consistency of the board surface, and does not affect bending and welding performance.

[0017] Sb element: A low-potential interface passivation auxiliary element, suitable for reinforcing Cu-Sn-Cr-Mo systems. Sb is enriched at the interface between the passivation film and the substrate on the steel surface, filling the microscopic gaps in Cr2O3 and molybdate passivation films, blocking the lateral penetration of chloride ions along the interface; it preferentially adsorbs on the surface of MnS and silicate inclusions, encapsulating corrosion-induced inclusions, preventing pitting corrosion at inclusion sites, inhibiting high-temperature thermal segregation of Cu, and avoiding local agglomeration of copper elements after annealing, which can cause color differences and uneven corrosion resistance on the plate surface; trace addition does not affect cold bending, spot welding, or coating adhesion, and will not cause cold brittleness of steel.

[0018] Cr element: The main anti-corrosion element in the surface layer. When steel comes into contact with air and salt spray, chromium preferentially oxidizes to form a nano-scale continuous Cr2O3 passivation film. The film is dense and has self-healing properties, which isolates oxygen, chloride ions and water vapor from contacting the iron substrate. It is the basis for the material's resistance to 420h neutral salt spray. In the low chromium range (<0.6%), it will not deteriorate the plasticity and cold bending performance of the steel.

[0019] Mo: A reinforcing element against chloride ion pitting corrosion. A single chromium passivation film has nanopores. Chloride ions will penetrate the film layer along the micropores, forming needle-like pitting corrosion. Molybdenum forms insoluble molybdate precipitates at the micropores, sealing the micropores of the passivation film and increasing the breakdown potential of the passivation film. It is specifically designed to deal with coastal and high-chlorine salt spray conditions and solve the problem of late-stage failure of chromium films.

[0020] The aforementioned Cu-Sn-Sb-Cr-Mo pentagonal composite corrosion-resistant system synergistically enhances corrosion resistance. Its functions are differentiated by protective layers: outer layer protection: Cr and Mo construct a dense, self-healing passivation film resistant to chlorine, resisting external salt spray corrosion and preventing pitting and breakdown; interface protection: Sb encapsulates internal inclusions and seals interfacial gaps, blocking lateral corrosion; inner layer protection: Cu and Sn seal grain boundary corrosion channels, preventing intergranular corrosion; matrix protection: Mn, Si, and Als purify the matrix and eliminate inclusion corrosion sources; impurity control: low P and low S eliminate low-melting-point harmful phases at grain boundaries. These five layers work synergistically at each level, with no overlapping elemental functions or performance conflicts. Sb specifically compensates for the shortcomings of the original system in interface corrosion.

[0021] Preferably, the sum of Sn and Sb content, Sn+Sb≥0.015%, ensures the minimum effective concentration of copper film modification elements and interface passivation auxiliary elements to work synergistically, and avoids uneven local corrosion resistance.

[0022] Preferably, P≤0.016% and S≤0.010%, further reducing the tendency of grain boundary segregation and intergranular corrosion, making the plate surface corrosion uniform, and preventing rapid edge corrosion and mottled corrosion under salt spray conditions.

[0023] Preferably, the yield strength is 270~370MPa, the tensile strength is 400~500MPa, and the A50 elongation is ≥30%. This range of mechanical properties takes into account the load-bearing requirements of warehouse racks and light steel structures as well as the forming requirements of stamping and bending, and matches the downstream assembly precision.

[0024] To achieve the above objectives, this invention also provides a method for preparing the aforementioned corrosion-resistant cold-rolled steel sheet. Addressing the problems of large performance fluctuations, uncontrollable Cu precipitation, and incomplete stress relief in existing technologies, the method employs strict parameter control within narrow ranges and differentiated process matching throughout the entire process. The complete process includes steelmaking and segmented refining, gradient temperature-controlled hot rolling, constant temperature controllable shallow pickling, multi-pass graded reduction and segmented tension cold rolling, six-segment gradient controllable annealing, and low-stress micro-leveling and refined graded finishing. Specifically, it includes the following steps: S1) Steelmaking and segmented refining processes (core impurity removal, elimination of corrosion defect sites): The process employs a converter top-bottom composite blowing method and low-superheat casting; pre-deoxidation of silicon-manganese alloy and precise oxygen determination with aluminum wire ensure that the total oxygen content of the molten steel is controlled to ≤25ppm; LF white slag refining for 25~35min controls P≤0.020% and S≤0.020%; after refining, a two-stage differentiated soft argon blowing method is adopted, with high flow rate argon blowing for 3~4min in the early stage to break large bubbles and polymer inclusions, and low flow rate stable pressure soft blowing for 5~8min in the later stage to remove fine inclusions and improve the purity of the matrix; S2) Gradient temperature controlled hot rolling process (pre-refining grains to prevent microstructure segregation): The slab is heated in a gradient manner, with a preheating rate of 8~10℃ / min and a soaking temperature of 1180~1220℃ for 30~45min to eliminate porosity and compositional segregation in the slab; the rough rolling temperature is 1050~1100℃ with a cumulative reduction of 65%~70%; the finish rolling temperature is 860~890℃ with a temperature fluctuation of ≤±5℃; after segmented laminar flow cooling, the coiling temperature is 600~640℃ with a coiling temperature fluctuation of ≤±8℃, resulting in a hot-rolled base material with a uniform microstructure. S3) Temperature-controlled shallow pickling process (non-destructive descaling, eliminating surface defects): Abandoning the traditional strong acid pickling and uncontrolled pickling mode, we adopt a unique process of constant temperature, timed, and gradient rinsing. The hydrochloric acid concentration is kept constant at 18%~22%, the pickling temperature is kept constant at 75~80℃, and the pickling time is 45~60 seconds. This process thoroughly removes the surface iron oxide scale without corroding the steel plate substrate. After pickling, we use three-level differentiated pressure high-pressure water rinsing to thoroughly remove residual acid and fine oxide residue from the plate surface, eliminating initial corrosion defects such as pitting and acid etching spots, and ensuring the integrity and corrosion resistance of the plate surface. S4) Multi-pass graded reduction and segmented tension cold rolling process (uniform stress, shape and property control): The process employs a five-pass progressively decreasing pressure reduction process, with a total reduction rate of 60%~75%. The single-pass reduction rates are 18%~26%, 22%~31%, 20%~28%, 15%~21%, and 8%~13% respectively, avoiding stress concentration and uneven microstructure caused by a single large reduction. The rolling speed is 8~12 m / s, and a three-stage adaptive tension control is adopted at the head, middle, and tail. Tension reduction at the head prevents cracking, constant tension in the middle stabilizes the plate shape, and tension increase at the tail prevents deviation. The tension deviation throughout the process is ≤±5%. This process can uniformly break up the hot-rolled microstructure, refine the grains, and disperse residual rolling stress, thus avoiding plate shape defects and stress concentration problems from the early stage. S5) Six-stage gradient controllable annealing process: A six-stage temperature control system is adopted, consisting of preheating, homogenization, slow cooling, rapid cooling, isothermal settling, and final cooling. The preheating stage has a heating rate of 12-15℃ / s to eliminate temperature differences on the plate surface and prevent warping. The homogenization stage reaches 760-790℃ and is held for 80-110 seconds to achieve complete recrystallization, promoting uniform solid solution of Cu, Sn, Cr, and Mo and avoiding elemental segregation. The slow cooling stage has a cooling rate of 4-6℃ / s to gradually release residual stress. The rapid cooling stage has a cooling rate of 18-22℃ / s. The process involves three steps: first, locking in fine-grained structures and inhibiting abnormal grain growth; second, maintaining a constant temperature of 380-420℃ for 20-30 seconds to allow quaternary corrosion-resistant elements to uniformly disperse and precipitate on the surface and at grain boundaries, forming a stable composite protective structure; and third, cooling in the furnace at an outlet temperature of 120-180℃. This process achieves a three-in-one control of grain refinement, stress release, and controllable precipitation of the composite corrosion-resistant phase, fundamentally solving the problems of unstable passivation films, easy pitting corrosion, and easy springback in traditional processes. S6) Low-stress micro-leveling and fine-grading finishing process: Adaptive low-pressure micro-leveling is adopted to eliminate yield plateau and correct micro-plate shape without generating new residual stress. Subsequent processes include multi-roller micro-straightening, precise edge cutting, surface defect grading and detection, and protective film packaging to completely eliminate secondary oxidation during storage and transportation, ensuring the consistency and stability of batch finished products.

[0025] Preferably, in step S1), after LF refining, a two-stage differentiated soft argon blowing is adopted. The argon blowing flow rate in the early stage is 300~500NL / min, and the argon blowing flow rate in the later stage is 100~200NL / min. The two-stage differentiated flow rates remove large-sized bubbles and micro-inclusions step by step, thereby further improving the purity of the matrix and eliminating the initial inducing factors of salt spray pitting corrosion from the source.

[0026] Preferably, in step S3), the pressure of the three-stage differential pressure high-pressure water rinsing after pickling is 3~5MPa, 2~3MPa, and 0.8~1.2MPa respectively. The three-stage gradient rinsing corresponds to coarse rinsing, fine rinsing, and final rinsing, which thoroughly removes residual acid and fine oxide residues from the board surface and eliminates initial corrosion defects such as pitting and acid etching spots on the board surface.

[0027] Preferably, in step S4), during the adaptive tension control of the head, middle, and tail sections, the tension at the head is reduced by 10% to 15% compared to the tension at the middle section, and the tension at the tail is increased by 5% to 10% compared to the tension at the middle section. The three sections of differentiated tension are matched with the process under five-pass decompression reduction, which can uniformly break up the hot-rolled structure, refine the grains, and disperse residual stress, thereby avoiding plate defects and stress concentration.

[0028] Preferably, in step S5), the outlet temperature of the slow cooling section in the six-stage gradient controllable annealing process is 660~700℃.

[0029] Preferably, in step S6), the micro-flattening elongation rate is 0.5%~1.2%, which can eliminate the yield plateau without adding residual stress, and the trimming amount is 3~5mm.

[0030] Compared with the prior art, the present invention has the following advantages: 1. Through the hierarchical synergistic protection of the Cu-Sn-Sb-Cr-Mo pentagonal composite corrosion-resistant system, a five-in-one protective structure is constructed, consisting of an outer layer of dense Cr2O3 self-healing passivation film, interface Sb blocking, inner layer Cu-Sn grain boundary blocking, matrix Mn-Si-Als purification, and strict control of impurities PS. Compared with traditional single Cu or Cu-Sn binary alloy systems, the corrosion rate in full immersion in 5% HCl solution is reduced to 5 g / m. 2 Below h, the corrosion rate drops to 3 g / m² in a 5% H₂SO₄ solution after full immersion. 2 ·h below, the neutral salt spray test duration is extended to more than 72h without obvious red rust, and the corrosion resistance of the whole plate is uniform; 2. A six-stage gradient controllable annealing process is adopted, with a temperature control system of six stages: preheating, homogenization, slow cooling, rapid cooling, constant temperature standing, and final cooling. This achieves a three-in-one synergistic effect of grain refinement, stress grade elimination, and controllable dispersion precipitation of corrosion-resistant phases. Compared with the traditional two-stage annealing, under the same alloy composition, the yield strength can be controlled in a stable range of 270~370MPa, the tensile strength is 400~500MPa, the A50 elongation is ≥30%, the sheet metal has small springback deformation during stamping and bending, and the assembly accuracy is high. 3. By using LF segmented refining and two-stage differentiated soft argon blowing, the total oxygen content of molten steel is controlled to be ≤25ppm, P≤0.020%, and S≤0.020%, eliminating inclusions and grain boundary corrosion sites in the steel from the source. The high purity of the matrix avoids early pitting corrosion and intergranular corrosion induced by inclusions, making the corrosion resistance of the plate stable in storage and long-term outdoor exposure environments. 4. Through a cold rolling process with five passes of progressively reduced pressure and adaptive tension control in the head, middle and tail sections, the hot-rolled structure is uniformly broken, the grains are refined and the residual rolling stress is dispersed. Combined with 0.5%~1.2% adaptive low pressure micro-leveling, the plate has a good shape, the yield plate is eliminated and the springback deformation is small. It can be directly used for stamping and bending forming of complex structural parts with a high processing qualification rate. 5. A shallow acid pickling process with constant temperature, timed, and gradient rinsing is adopted. The hydrochloric acid concentration is 18%~22%, the temperature is 75~80℃ and the time is 45~60s. This process removes only the surface iron oxide scale without corroding the steel plate substrate. Combined with three-level differentiated pressure high-pressure water rinsing, it eliminates initial corrosion defects such as pitting and acid spots on the plate surface, ensuring the integrity of the plate surface and the consistency of the corrosion resistance of the entire plate. 6. Without introducing high-priced and microalloying elements such as Ni, Nb, Ti, and B, this product achieves a corrosion resistance improvement of more than 5 times at the cost level of ordinary cold-rolled structural steel by using only five conventional elements (Cu, Sn, Sb, Cr, and Mo) in synergistic and refined process matching. The raw material cost is significantly reduced compared to stainless steel and high Cr-Ni-Mo corrosion-resistant steel. It has a wide process window and high yield, making it suitable for mass production at low cost of civilian structural components such as warehouse racks, outdoor light steel structures, and warehouse equipment cabinets. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In this invention, the chemical composition of the corrosion-resistant cold-rolled steel sheet, by mass percentage, includes: C: 0.02%~0.10%, Si: 0.05%~0.25%, Mn: 0.10%~1.0%, P≤0.020%, S≤0.020%, Als≥0.010%, Cu: 0.10%~0.50%, Sn: 0.001%~0.045%, Sb: 0.001%~0.045%, Cr: 0.10%~0.60%, Mo: 0.03%~0.20%, with the balance being Fe and unavoidable trace impurities.

[0033] The preparation method includes, in sequence, steelmaking and segmented refining processes, gradient temperature-controlled hot rolling processes, constant temperature controllable shallow pickling processes, multi-pass graded reduction and segmented tension cold rolling processes, six-segment gradient controllable annealing processes, and low-stress micro-leveling and refined graded finishing processes. The invention will be further described in detail below through specific embodiments. Example 1 The corrosion-resistant cold-rolled steel sheet of this embodiment has the following chemical composition by mass percentage: C: 0.06%, Si: 0.15%, Mn: 0.65%, P: 0.013%, S: 0.012%, Als: 0.022%, Cu: 0.25%, Sn: 0.020%, Sb: 0.018%, Cr: 0.40%, Mo: 0.12%, with the balance being Fe and unavoidable trace impurities.

[0034] The method for preparing corrosion-resistant cold-rolled steel sheet in this embodiment includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to 22ppm; LF white slag refining is carried out for 30 minutes; after refining, two-stage differentiated soft argon blowing is adopted, with a high flow rate of 400NL / min for 3.5 minutes in the early stage and a low flow rate of 150NL / min for 7 minutes of stable soft blowing in the later stage. S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a preheating rate of 9℃ / min, a soaking temperature of 1200℃ and a holding temperature of 38min; the roughing temperature is 1070℃ and the cumulative reduction rate is 68%; the finishing temperature is 870℃ with a temperature fluctuation of ±4℃; after segmented laminar flow cooling, the coiling temperature is 615℃ with a coiling temperature fluctuation of ≤±6℃. S3) Temperature-controlled shallow pickling process: hydrochloric acid concentration of 20%, pickling temperature of 78℃ is kept constant and controlled, pickling time is 52s; after pickling, three-level differentiated pressure high-pressure water rinsing is used, with pressures of 4MPa, 2.5MPa and 1MPa respectively. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced pressure reduction process is adopted, with a total reduction rate of 66%. The reduction rates of each single pass are 20%, 25%, 23%, 18%, and 10%, respectively. The rolling speed is 10 m / s, and an adaptive tension control is adopted for the head, middle, and tail sections. The tension at the head is reduced by 12% compared to the middle section, and the tension at the tail is increased by 8% compared to the middle section. The tension deviation throughout the process is ±4%. S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 13℃ / s; the homogenization stage has a temperature of 770℃ and a holding time of 95s; the slow cooling stage has a cooling rate of 5℃ / s and an outlet temperature of 680℃; the rapid cooling stage has a cooling rate of 20℃ / s; the constant temperature holding stage has a temperature of 400℃ and a duration of 24s; and the final cooling stage is cooled with the furnace and has an outlet temperature of 150℃. S6) Low-stress micro-leveling and fine grading finishing process: Adaptive low-pressure micro-leveling is adopted, with a micro-leveling elongation rate of 0.8%. Subsequently, it undergoes multi-roller micro-straightening, precise edge cutting, surface defect grading detection, and protective packaging with a cutting amount of 4mm to obtain the finished product.

[0035] The corrosion-resistant cold-rolled steel sheet obtained in this embodiment has the following properties: yield strength 287 MPa, tensile strength 440 MPa, elongation after fracture 35%; and a corrosion rate of ≤3.6 g / m² in a 5% HCl solution during full immersion. 2 • h (tested by full immersion in 10.5% hydrochloric acid at 60℃ for 6 hours), the corrosion rate during full immersion in 5% H2SO4 solution is ≤2.2 g / m 2 • h (tested by immersion in 20% sulfuric acid at 20℃ for 24 hours), no obvious red rust was observed after 80 hours of neutral salt spray test.

[0036] Example 2 The corrosion-resistant cold-rolled steel sheet of this embodiment has the following chemical composition by mass percentage: C: 0.04%, Si: 0.10%, Mn: 0.50%, P: 0.011%, S: 0.010%, Als: 0.025%, Cu: 0.18%, Sn: 0.015%, Sb: 0.012%, Cr: 0.32%, Mo: 0.10%, with the balance being Fe and unavoidable trace impurities.

[0037] The method for preparing corrosion-resistant cold-rolled steel sheet in this embodiment includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to 20ppm; LF white slag refining is carried out for 28 minutes; after refining, two-stage differentiated soft argon blowing is adopted, with a high flow rate of 300NL / min for 3 minutes in the early stage and a low flow rate of 100NL / min for 6 minutes in the later stage. S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a preheating rate of 8.5℃ / min, a soaking temperature of 1190℃ and a holding temperature of 32min; the roughing temperature is 1060℃, with a cumulative reduction rate of 66%; the finishing temperature is 865℃, with a temperature fluctuation of ±3℃; after segmented laminar flow cooling, the coiling temperature is 605℃, with a coiling temperature fluctuation of ≤±5℃. S3) Temperature-controlled shallow pickling process: The hydrochloric acid concentration is 29%, the pickling temperature is 76℃ and the pickling time is 48s; after pickling, a three-level differentiated pressure high-pressure water rinse is used, with pressures of 3.5MPa, 2.2MPa and 0.9MPa respectively. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced pressure reduction process is adopted, with a total reduction rate of 62%. The single-pass reduction rates are 19%, 23%, 21%, 16%, and 9% respectively. The rolling speed is 9 m / s, and an adaptive tension control is adopted for the head, middle, and tail sections. The tension at the head is reduced by 10% compared to the middle section, and the tension at the tail is increased by 6% compared to the middle section. The tension deviation throughout the process is ±3%. S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 12.5℃ / s; the homogenization stage has a temperature of 765℃ and a holding time of 85s; the slow cooling stage has a cooling rate of 4.5℃ / s and an outlet temperature of 660℃; the rapid cooling stage has a cooling rate of 19℃ / s; the constant temperature holding stage has a temperature of 420℃ and a duration of 22s; the final cooling stage is carried out with the furnace and has an outlet temperature of 180℃. S6) Low-stress micro-leveling and fine grading finishing process: Adaptive low-pressure micro-leveling is adopted, with a micro-leveling elongation rate of 1.7%. Subsequently, it undergoes multi-roller micro-straightening, precise edge cutting, surface defect grading detection, and protective packaging with a cutting amount of 3mm to obtain the finished product.

[0038] The corrosion-resistant cold-rolled steel sheet obtained in this embodiment has the following properties: yield strength 304 MPa, tensile strength 454 MPa, elongation after fracture 33.5%; and a corrosion rate of ≤3.2 g / m² in a 5% HCl solution during full immersion. 2 • h (tested by full immersion in 10.5% hydrochloric acid at 60℃ for 6 hours), the corrosion rate during full immersion in 5% H2SO4 solution is ≤2.9 g / m 2 • h (tested by immersion in 20% sulfuric acid at 20℃ for 24 hours), no obvious red rust was observed after 80 hours of neutral salt spray test.

[0039] Example 3 The corrosion-resistant cold-rolled steel sheet of this embodiment has the following chemical composition by mass percentage: C: 0.09%, Si: 0.22%, Mn: 0.90%, P: 0.017%, S: 0.015%, Als: 0.048%, Cu: 0.42%, Sn: 0.038%, Sb: 0.035%, Cr: 0.55%, Mo: 0.18%, with the balance being Fe and unavoidable trace impurities.

[0040] The method for preparing corrosion-resistant cold-rolled steel sheet in this embodiment includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to 24ppm; LF white slag refining is carried out for 33 minutes; after refining, two-stage differentiated soft argon blowing is adopted, with a large flow rate of 500NL / min for 4 minutes in the early stage and a small flow rate of 200NL / min for 8 minutes in the later stage. S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a heating rate of 10℃ / min in the preheating section, a temperature of 1210℃ in the soaking section and a holding temperature of 42min; the roughing temperature is 1090℃, with a cumulative reduction rate of 70%; the finishing temperature is 880℃, with a temperature fluctuation of ±5℃; after segmented laminar flow cooling, the coiling temperature is 630℃, with a coiling temperature fluctuation of ≤±7℃. S3) Temperature-controlled shallow pickling process: The hydrochloric acid concentration is 22%, the pickling temperature is 80℃ and the pickling time is 58s; after pickling, a three-level differentiated pressure high-pressure water rinse is used, with pressures of 5MPa, 3MPa and 1.2MPa respectively. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced pressure reduction process is adopted, with a total reduction rate of 69%. The reduction rates of each single pass are 22%, 27%, 25%, 19%, and 11%, respectively. The rolling speed is 11 m / s, and an adaptive tension control is adopted in three sections: head, middle, and tail. The tension at the head is reduced by 15% compared to the middle section, and the tension at the tail is increased by 10% compared to the middle section. The tension deviation throughout the process is ±5%. S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 15℃ / s; the homogenization stage has a temperature of 780℃ and a holding time of 105s; the slow cooling stage has a cooling rate of 5.5℃ / s and an outlet temperature of 700℃; the rapid cooling stage has a cooling rate of 21℃ / s; the constant temperature holding stage has a temperature of 380℃ and a duration of 28s; and the final cooling stage is carried out with the furnace and has an outlet temperature of 150℃. S6) Low-stress micro-leveling and fine grading finishing process: Adaptive low-pressure micro-leveling is adopted, with a micro-leveling elongation rate of 1.0%. Subsequently, it undergoes multi-roller micro-straightening, precise edge cutting, surface defect grading detection, and protective packaging with a cutting amount of 5mm to obtain the finished product.

[0041] The corrosion-resistant cold-rolled steel sheet obtained in this embodiment has the following properties: yield strength 334 MPa, tensile strength 486 MPa, elongation after fracture 32%; and a corrosion rate of ≤3.7 g / m² in a 5% HCl solution during full immersion. 2 • h (tested by full immersion in 10.5% hydrochloric acid at 60℃ for 6 hours), the corrosion rate during full immersion in 5% H2SO4 solution is ≤2.0 g / m 2 • h (tested by immersion in 20% sulfuric acid at 20℃ for 24 hours), no obvious red rust was observed after 80 hours of neutral salt spray test.

[0042] Example 4 The corrosion-resistant cold-rolled steel sheet of this embodiment has the following chemical composition by mass percentage: C: 0.06%, Si: 0.15%, Mn: 0.65%, P: 0.010%, S: 0.008%, Als: 0.022%, Cu: 0.25%, Sn: 0.020%, Sb: 0.018%, Cr: 0.40%, Mo: 0.12%, with the balance being Fe and unavoidable trace impurities.

[0043] The method for preparing corrosion-resistant cold-rolled steel sheet in this embodiment includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to 25ppm; LF white slag refining is carried out for 25min; after refining, two-stage differentiated soft argon blowing is adopted, with a high flow rate of 300NL / min for 4min in the early stage and a low flow rate of 100NL / min for 8min in the later stage. S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a heating rate of 10℃ / min in the preheating section, a temperature of 1180℃ in the soaking section and a holding temperature of 45min; the roughing temperature is 1050℃, with a cumulative reduction rate of 65%; the finishing temperature is 860℃, with a temperature fluctuation of ±5℃; after segmented laminar flow cooling, the coiling temperature is 600℃, with a coiling temperature fluctuation of ≤±8℃. S3) Temperature-controlled shallow pickling process: The hydrochloric acid concentration is 22%, the pickling temperature is 75℃ and the pickling time is 45s; after pickling, a three-level differentiated pressure high-pressure water rinse is used, with pressures of 5MPa, 3MPa and 1.2MPa respectively. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced pressure reduction process is adopted, with a total reduction rate of 60%. The reduction rates of each single pass are 18%, 22%, 20%, 15%, and 8% respectively. The rolling speed is 8 m / s, and an adaptive tension control is adopted in three sections: head, middle, and tail. The tension at the head is reduced by 15% compared to the middle section, and the tension at the tail is increased by 10% compared to the middle section. The tension deviation throughout the process is ±5%. S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 15℃ / s; the homogenization stage has a temperature of 790℃ and a holding time of 80s; the slow cooling stage has a cooling rate of 6℃ / s and an outlet temperature of 700℃; the rapid cooling stage has a cooling rate of 22℃ / s; the constant temperature holding stage has a temperature of 420℃ and a duration of 20s; and the final cooling stage is cooled with the furnace and has an outlet temperature of 180℃. S6) Low-stress micro-leveling and fine grading finishing process: Adaptive low-pressure micro-leveling is adopted, with a micro-leveling elongation rate of 1.2%. Subsequently, it undergoes multi-roller micro-straightening, precise edge cutting, surface defect grading and detection, and protective packaging with a cutting amount of 5mm to obtain the finished product.

[0044] The corrosion-resistant cold-rolled steel sheet obtained in this embodiment has the following properties: yield strength 295 MPa, tensile strength 448 MPa, elongation after fracture 34%; and a corrosion rate of ≤3.0 g / m² in a 5% HCl solution during full immersion. 2 • h (tested by full immersion in 10.5% hydrochloric acid at 60℃ for 6 hours), the corrosion rate during full immersion in 5% H2SO4 solution is ≤1.8 g / m 2 • h (tested by immersion in 20% sulfuric acid at 20℃ for 24 hours), no obvious red rust was observed after 80 hours of neutral salt spray test.

[0045] Example 5 The corrosion-resistant cold-rolled steel sheet of this embodiment has the following chemical composition by mass percentage: C: 0.06%, Si: 0.15%, Mn: 0.65%, P: 0.010%, S: 0.008%, Als: 0.022%, Cu: 0.25%, Sn: 0.020%, Sb: 0.018%, Cr: 0.40%, Mo: 0.12%, with the balance being Fe and unavoidable trace impurities.

[0046] The method for preparing corrosion-resistant cold-rolled steel sheet in this embodiment includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to 20ppm; LF white slag refining is carried out for 35 minutes; after refining, two-stage differentiated soft argon blowing is adopted, with a large flow rate of 500NL / min for 3 minutes in the early stage and a small flow rate of 200NL / min for 5 minutes of stable soft blowing in the later stage. S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a preheating rate of 8℃ / min, a soaking temperature of 1220℃ and a holding time of 30min; the roughing temperature is 1190℃ and the cumulative reduction rate is 70%; the finishing temperature is 890℃ with a temperature fluctuation of ±5℃; after segmented laminar flow cooling, the coiling temperature is 640℃ with a coiling temperature fluctuation of ≤±7℃. S3) Temperature-controlled shallow pickling process: The hydrochloric acid concentration is 18%, the pickling temperature is 80℃ and the pickling time is 60s; after pickling, a three-level differentiated pressure high-pressure water rinse is used, with pressures of 3MPa, 2MPa and 0.8MPa respectively. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced pressure reduction process is adopted, with a total reduction rate of 75%. The single-pass reduction rates are 26%, 31%, 28%, 21%, and 13% respectively. The rolling speed is 12m / s, and an adaptive tension control is adopted for the head, middle, and tail sections. The tension at the head is reduced by 10% compared to the middle section, and the tension at the tail is increased by 5% compared to the middle section. The tension deviation throughout the process is ±5%. S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 12℃ / s; the homogenization stage has a temperature of 760℃ and a holding time of 110s; the slow cooling stage has a cooling rate of 4℃ / s and an outlet temperature of 660℃; the rapid cooling stage has a cooling rate of 18℃ / s; the constant temperature holding stage has a temperature of 380℃ and a duration of 30s; and the final cooling stage is cooled with the furnace and has an outlet temperature of 120℃. S6) Low-stress micro-leveling and fine grading finishing process: Adaptive low-pressure micro-leveling is adopted, with a micro-leveling elongation rate of 0.5%. Subsequently, it undergoes multi-roller micro-straightening, precise edge cutting, surface defect grading and detection, and protective packaging with a cutting amount of 3mm to obtain the finished product.

[0047] The corrosion-resistant cold-rolled steel sheet obtained in this embodiment has the following properties: yield strength 312 MPa, tensile strength 462 MPa, elongation after fracture 34.5%; and a corrosion rate of ≤2.6 g / m² in a 5% HCl solution during full immersion. 2 • h (tested by full immersion in 10.5% hydrochloric acid at 60℃ for 6 hours), the corrosion rate during full immersion in 5% H2SO4 solution is ≤1.5 g / m 2 • h (tested by immersion in 20% sulfuric acid at 20℃ for 24 hours), no obvious red rust was observed after 80 hours of neutral salt spray test.

[0048] Comparative example: Comparative Example 1 (Ordinary SPCC cold-rolled steel sheet, existing conventional product) The chemical composition is that of conventional SPCC, C: 0.05%, Si: 0.02%, Mn: 0.33%, S: 0.025%, P: 0.028%, Als: 0.047%, without the addition of Cu, Sn, Sb, Cr, and Mo corrosion-resistant alloying elements.

[0049] It adopts traditional smelting and two-stage conventional annealing process.

[0050] Finished product properties: Yield strength 240 MPa, tensile strength 375 MPa, elongation after fracture 42%; corrosion rate in 5% HCl solution after full immersion is 102.5 g / m.2 The corrosion rate during full immersion in 5% H2SO4 solution is 45.1 g / m. 2 • h, obvious red rust appeared after 6 hours of neutral salt spray test.

[0051] Comparative Example 2: Compared with Example 1, the chemical composition is Sn+Sb=0.005% (not satisfying Sn+Sb≥0.015%), Sn: 0.002%, Sb: 0.003%, and the content of other elements is the same as in Example 1; The production process is the same as in Example 1.

[0052] Finished product properties: yield strength 291 MPa, tensile strength 444 MPa, elongation after fracture 35.5%; corrosion rate in 5% HCl solution after full immersion is 13.8 g / m. 2 The corrosion rate during full immersion in 5% H2SO4 solution is 9.3 g / m. 2 •h, no obvious red rust was observed after 68 hours of neutral salt spray testing.

[0053] The results showed that when the sum of Sn and Sb contents was below the preferred range, the synergistic effect of copper film modification and interface passivation decreased significantly.

[0054] Comparative Example 3: Compared with Example 1, the chemical composition is 0.005% Mo, and the remaining elements are the same as in Example 1.

[0055] Production process: Same as in Example 1.

[0056] Finished product properties: Yield strength 278 MPa, tensile strength 431 MPa, elongation after fracture 34%; corrosion rate in 5% HCl solution during full immersion ≤ 5.9 g / m 2 h, the corrosion rate during full immersion in 5% H2SO4 solution is ≤3.6 g / m 2 h, no obvious red rust was observed after 47 hours of neutral salt spray testing.

[0057] The results showed that Mo can effectively increase the breakdown potential of the passivation film, and the material’s resistance to chloride ion pitting corrosion is significantly reduced after its absence.

[0058] Comparative Example 4 Chemical composition: Compared with Example 1, Cr: 0.018%, and the remaining elements are the same as in Example 1.

[0059] Production process: completely consistent with Example 1.

[0060] Finished product properties: Yield strength 261 MPa, tensile strength 403 MPa, elongation after fracture 37%, corrosion rate ≤12.6 g / m² in 5% HCl solution. 2 h, the corrosion rate during full immersion in 5% H2SO4 solution is ≤9.2 g / m 2 h, no obvious red rust was observed after 32 hours of neutral salt spray testing.

[0061] The results show that Cr is the core basic element for constructing a continuous passivation film, providing a fundamental guarantee for the overall corrosion resistance performance.

[0062] Comparative Example 5 Chemical composition: Same as in Example 1.

[0063] Production Process: The production process adopts the traditional annealing process to replace the six-stage gradient controllable annealing process of this invention. Converter smelting, molten steel with 27ppm total oxygen; LF refining for 22min, argon blowing for 5min; slab held at 1200℃ without holding, rough rolling at 1070℃, finishing rolling at 855℃, coiling temperature at 700℃; hydrochloric acid constant temperature pickling for 42s; cold rolling total reduction rate of 80%, rolling speed of 10m / s; annealing: soaking at 730℃ for 45s, slow cooling at 8℃ / s, fast cooling at 20℃ / s, constant temperature holding at 400℃ for 15s; leveling elongation of 0.4%, followed by edge trimming, inspection, and packaging to obtain the finished product.

[0064] Finished product properties: Yield strength 368MPa, tensile strength 496MPa, elongation after fracture 26%, corrosion rate ≤5.1g / m² in 5% HCl solution. 2 h, the corrosion rate during full immersion in 5% H2SO4 solution is ≤2.9 g / m 2 h, no obvious red rust was observed after 72 hours of neutral salt spray testing.

[0065] As can be seen from the above embodiments and comparative examples, the Cu-Sn-Sb-Cr-Mo five-element system in the chemical composition of the corrosion-resistant cold-rolled steel sheet of the present invention performs its respective function and works synergistically for protection. The absence of core elements will cause a significant decrease in corrosion resistance. Using the exact same alloy composition, replacing it with the traditional annealing process also results in a significant deterioration in formability, highlighting the core value of refined processes such as six-stage gradient annealing and segmented tension cold rolling. Compared with ordinary SPCC sheets, the salt spray resistance of the material of the present invention is increased by more than 5 times, its mechanical and formability properties are stable, and it is suitable for complex service environments, demonstrating outstanding technical advantages.

[0066] It should be noted that the above description of the technical solutions is exemplary, and this specification may be embodied in different forms and should not be construed as limiting it to the technical solutions set forth herein. Rather, providing these descriptions will ensure that the disclosure of this invention is thorough and complete, and will fully convey the scope of this specification to those skilled in the art. Furthermore, the technical solutions of this invention are defined only by the scope of the claims. Features of various embodiments of this invention may be combined or spliced ​​together in part or in whole, and may be implemented in various different configurations as will be fully understood by those skilled in the art. Embodiments of this invention may be implemented independently of each other or may be implemented together in an interdependent relationship.

[0067] For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and the above structures should all be considered to fall within the protection scope of the present invention.

Claims

1. A corrosion-resistant cold-rolled steel sheet, characterized in that: Its chemical composition by mass percentage includes: C: 0.02%~0.10%, Si: 0.05%~0.25%, Mn: 0.10%~1.0%, P≤0.020%, S≤0.020%, Als≥0.010%, Cu: 0.10%~0.50%, Sn: 0.001%~0.045%, Sb: 0.001%~0.045%, Cr: 0.10%~0.60%, Mo: 0.03%~0.20%, with the balance being Fe and unavoidable trace impurities.

2. The corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: The sum of Sn and Sb content, Sn+Sb ≥ 0.015%.

3. The corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: P≤0.016%, S≤0.010%.

4. The corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: Yield strength is 270~370MPa, tensile strength is 400~500MPa, and A50 elongation is ≥30%.

5. A method for preparing the corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: Includes the following steps: S1) Steelmaking and segmented refining process: Converter top and bottom combined blowing is adopted, and low superheat casting is used; silicon-manganese alloy pre-deoxidation and aluminum wire precise oxygen determination are used to control the total oxygen content of molten steel to ≤25ppm; LF white slag refining is carried out for 25~35min, and P≤0.020% and S≤0.020% are controlled; after refining, two-stage differentiated soft argon blowing is adopted, with high flow rate argon blowing for 3~4min in the early stage and low flow rate stable pressure soft blowing for 5~8min in the later stage; S2) Gradient temperature controlled hot rolling process: The slab is heated in a gradient manner, with a preheating rate of 8~10℃ / min, a soaking temperature of 1180~1220℃ and a holding temperature of 30~45min; the roughing temperature is 1050~1100℃, with a cumulative reduction rate of 65%~70%; the finishing temperature is 860~890℃, with a temperature fluctuation of ≤±5℃; after segmented laminar flow cooling, the coiling temperature is 600~640℃, with a coiling temperature fluctuation of ≤±8℃. S3) Temperature-controlled shallow pickling process: hydrochloric acid concentration of 18%~22%, pickling temperature of 75~80℃ is kept constant, pickling time is 45~60s; after pickling, three-level differentiated pressure high-pressure water rinsing is used. S4) Multi-pass graded reduction and segmented tension cold rolling process: A 5-pass progressively reduced reduction process is adopted, with a total reduction rate of 60%~75%, and the single-pass reduction rates are 18%~26%, 22%~31%, 20%~28%, 15%~21%, and 8%~13% respectively; the rolling speed is 8~12m / s, and an adaptive tension control is adopted in the head, middle, and tail sections, with a tension deviation of ≤±5% throughout the process; S5) Six-stage gradient controllable annealing process: adopts a six-stage temperature control system of preheating, homogenization, slow cooling, rapid cooling, constant temperature holding, and final cooling. The preheating stage has a heating rate of 12~15℃ / s; the homogenization stage has a temperature of 760~790℃ and a holding time of 80~110s; the slow cooling stage has a cooling rate of 4~6℃ / s; the rapid cooling stage has a cooling rate of 18~22℃ / s; the constant temperature holding stage has a temperature of 380~420℃ and a duration of 20~30s; the final cooling stage is cooled with the furnace, and the outlet temperature is 120~180℃. S6) Low-stress micro-leveling and fine-grading finishing process: Adaptive low-pressure micro-leveling is adopted, followed by multi-roller micro-straightening, precise edge cutting, surface defect grading detection, and protective packaging.

6. The method for preparing corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: In step S1), after LF refining, a two-stage differentiated soft argon blowing process is adopted. The argon blowing flow rate in the early stage is 300~500NL / min, and the argon blowing flow rate in the later stage is 100~200NL / min.

7. The method for preparing corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: In step S3), the pressures of the three-stage differentiated high-pressure water rinsing after pickling are 3~5MPa, 2~3MPa, and 0.8~1.2MPa, respectively.

8. The method for preparing corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: In step S4), during the adaptive tension control of the head, middle, and tail segments, the tension in the head is reduced by 10% to 15% compared to the tension in the middle segment, and the tension in the tail is increased by 5% to 10% compared to the tension in the middle segment.

9. The method for preparing corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: In step S5), during the six-stage gradient controllable annealing process, the outlet temperature of the slow cooling section is 660~700℃.

10. The method for preparing corrosion-resistant cold-rolled steel sheet as described in claim 1, characterized in that: In step S6), the micro-flattening elongation rate is 0.5%~1.2%, and the trimming amount is 3~5mm.