Raw material composition for cold-rolled corrosion-resistant steel, cold-rolled corrosion-resistant steel, and method for producing the same

Abstract

The application belongs to the technical field of corrosion-resistant steel manufacturing, and particularly relates to raw material components of cold-rolled corrosion-resistant steel, the cold-rolled corrosion-resistant steel and a preparation method thereof. The raw material components of the cold-rolled corrosion-resistant steel include, with the total mass of the raw material components of the cold-rolled corrosion-resistant steel being 100%, 0.04-0.12% of carbon elements, 0.50-1.25% of silicon elements, 0.20-0.60% of manganese elements, 0.10-0.20% of phosphorus elements, less than 0.015% of sulfur elements, 0.20-0.60% of copper elements, 0.020-0.055% of acid-melted aluminum, 0.05-0.15% of antimony elements, 0.0010-0.0020% of boron elements, 0.01-0.02% of titanium elements, and the balance of iron elements and impurity elements. The cold-rolled corrosion-resistant steel prepared by using the raw material components of the cold-rolled corrosion-resistant steel has better performances of resisting hydrochloric acid and resisting sulfuric acid, and the cold-rolled corrosion-resistant steel has better toughness and is not easy to break.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant steel manufacturing technology, specifically relating to the raw material composition of cold-rolled corrosion-resistant steel, cold-rolled corrosion-resistant steel and its preparation method, and particularly to economical cold-rolled corrosion-resistant steel for consumables in corrosive environments of hydrochloric acid and sulfuric acid. Background Technology

[0002] With the development of various industries at home and abroad, the application scope of some special products has gradually increased, and the corrosion environment they face has become increasingly complex. Especially in some chemical and power industries, their flues also face complex environmental corrosion. This is mainly because the flue gas in the combustion process contains gases such as S, N, and Cl. If these gases encounter water vapor in the high-temperature zone, boiling corrosion will occur. As the gases are discharged, dew point corrosion will occur in some low-temperature zones, thus forming complex environments such as sulfuric acid and hydrochloric acid, which will cause serious corrosion to the pipe walls and heat exchangers.

[0003] Currently, cold-rolled corrosion-resistant steel is commonly used to manufacture heat exchanger corrugated sheets for heat conduction. These corrugated sheets typically operate within the temperature range of 80–200°C. However, at this temperature, SO2 and chlorine gases easily form small droplets on the steel plate surface and condense, leading to dew point corrosion. Therefore, these corrugated sheets face a complex corrosive environment, resulting in corrosion and requiring timely replacement. Consequently, the cold-rolled corrosion-resistant steel used in the manufacture of heat exchanger corrugated sheets must be inexpensive and economical to effectively reduce costs. Furthermore, since the corrosive droplets in dew point corrosion are primarily hydrochloric acid and sulfuric acid, the cold-rolled corrosion-resistant steel must also be able to withstand sulfuric acid and hydrochloric acid corrosion environments. Currently, most corrosion-resistant steels in the industry focus on weathering corrosion resistance, with limited reports on resistance to sulfuric acid and hydrochloric acid corrosion.

[0004] Chinese patent CN109487171A discloses a hydrochloric acid-resistant steel and its preparation method. The chemical composition of the hydrochloric acid-resistant steel is as follows: Cr: 12-15%, Mo: 2-4%, Sn: 0.25-0.65%, Cu: 0.3-0.5%, Sb: 0.1-0.4%, Nb: 0.15-0.25%, Ti: 0.05-0.15%, C≤0.15%, and Fe as the balance. This corrosion-resistant steel has a certain degree of resistance to hydrochloric acid. However, the patent does not specify whether it can also resist sulfuric acid. Furthermore, a large number of alloying elements are added to this corrosion-resistant steel, resulting in high cost. Summary of the Invention

[0005] The purpose of this invention is to address the lack of research on economical cold-rolled steels that are simultaneously resistant to hydrochloric acid and sulfuric acid in the existing technology, and to propose the raw material composition, cold-rolled corrosion-resistant steel and its preparation method. The raw material composition of the cold-rolled corrosion-resistant steel of the present invention contains a certain amount of elements such as Si, P, Cu, Sb and B. Among them, the Si element easily forms SiO2 particles on the surface of the steel plate. The SiO2 particles on the surface of the steel plate can effectively fill the pores of the oxide film formed on the surface of the steel plate. The P, Cu and Sb elements, under the interaction, easily form a dense protective layer covering the surface of the steel plate. At the same time, due to the presence of SiO2 particles, the protective layer on the surface of the steel plate has a certain strength. Under the synergistic effect of SiO2 particles and protective layer, it can effectively prevent SO2 gas and chlorine gas from forming corrosive droplets on the surface of the steel plate, thereby effectively improving the resistance of cold-rolled corrosion-resistant steel to hydrochloric acid and sulfuric acid. Since the Si, P, Cu and Sb elements in the raw material composition are prone to enrichment at the grain boundaries, this enrichment phenomenon may lead to adverse consequences such as grain boundary embrittlement and decreased corrosion resistance. The B element in the raw material composition can improve the consequences of grain boundary embrittlement and decreased corrosion resistance. The cold-rolled corrosion-resistant steel prepared using the raw material composition of the cold-rolled corrosion-resistant steel of this invention has superior resistance to hydrochloric acid and sulfuric acid. At the same time, the cold-rolled corrosion-resistant steel has good toughness and is not easy to break, thereby achieving the effect of effectively reducing costs.

[0006] The first aspect of this invention provides a raw material composition for cold-rolled corrosion-resistant steel, which, based on the total mass of the raw material composition of the cold-rolled corrosion-resistant steel as 100%, includes: 0.04-0.12% carbon, 0.50-1.25% silicon, 0.20-0.60% manganese, 0.10-0.20% phosphorus, less than 0.015% sulfur, 0.20-0.60% copper, 0.020-0.055% acid-fused aluminum, 0.05-0.15% antimony, 0.0010-0.0020% boron, 0.01-0.02% titanium, with the balance being iron and impurity elements.

[0007] Preferably, based on the total mass of the raw material components of the cold-rolled corrosion-resistant steel as 100%, it includes: 0.05-0.06% carbon, 0.65-1.25% silicon, 0.30-0.55% manganese, 0.10-0.18% phosphorus, 0.008-0.010% sulfur, 0.30-0.35% copper, 0.033-0.040% acid-fused aluminum, 0.05-0.10% antimony, 0.0010-0.0012% boron, 0.018-0.02% titanium, with the balance being iron and impurity elements.

[0008] More preferably, the relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula:

[0009] (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) /

[0010] (10.25*e+1.06*f)≥20;

[0011] Where a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, and f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel.

[0012] More preferably, the value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20 to 38.

[0013] A second aspect of this invention provides a method for preparing cold-rolled corrosion-resistant steel, the method comprising the following steps:

[0014] Step S1: Smelt the pretreated molten iron to obtain molten steel;

[0015] Step S2: The molten steel obtained in step S1 is tempered and refined to adjust the composition and content of the raw material components of the cold-rolled corrosion-resistant steel as described above.

[0016] Step S3: The molten steel obtained in step S2 is continuously cast to form a billet, and then the billet is successively subjected to hot rolling, cold rolling, continuous annealing and leveling.

[0017] Preferably, based on the total mass of the raw material components of the cold-rolled corrosion-resistant steel as 100%, it includes: 0.05-0.06% carbon, 0.65-1.25% silicon, 0.30-0.55% manganese, 0.10-0.18% phosphorus, 0.008-0.010% sulfur, 0.30-0.35% copper, 0.033-0.040% acid-fused aluminum, 0.05-0.10% antimony, 0.0010-0.0012% boron, 0.018-0.02% titanium, with the balance being iron and impurity elements.

[0018] More preferably, the relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula:

[0019] (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) /

[0020] (10.25*e+1.06*f)≥20;

[0021] Where a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, and f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel.

[0022] More preferably, the value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20 to 38.

[0023] Preferably, in step S1, the sulfur content of the pretreated molten iron is ≤0.005%; in step S3, the hot rolling conditions are: heating temperature of 1200-1240℃, heating time ≤150min, final rolling temperature of 850-900℃, and coiling temperature of 550-600℃; the cold rolling conditions are: total reduction rate of 55-75%; the continuous annealing conditions are: heating temperature of 790-810℃, soaking temperature of 770-800℃, and annealing speed of 80-200m / min; the leveling conditions are: leveling elongation of 0.8-1.4%.

[0024] A third aspect of the present invention provides a cold-rolled corrosion-resistant steel prepared according to the preparation method of cold-rolled corrosion-resistant steel described above.

[0025] The raw material composition, cold-rolled corrosion-resistant steel, and preparation method of the cold-rolled corrosion-resistant steel described in this invention have at least the following beneficial effects:

[0026] (1) In this invention, cold-rolled corrosion-resistant steel is prepared using raw material components composed of elements such as Si (silicon), P (phosphorus), Cu (copper), Sb (antimony), and B (boron). Since Si easily forms SiO2 particles on the surface of the steel plate, and P, Cu, and Sb elements easily form a dense protective layer covering the surface of the steel plate under their interaction, the presence of SiO2 particles further promotes the protective layer to have higher strength. Therefore, under the synergistic effect of SiO2 particles and protective layer, it can effectively prevent SO2 gas and chlorine gas from forming corrosive droplets on the surface of the steel plate, thereby effectively improving the hydrochloric acid resistance of cold-rolled corrosion-resistant steel. The cold-rolled corrosion-resistant steel exhibits excellent resistance to both hydrochloric acid and sulfuric acid. Furthermore, elements such as Si, P, Cu, and Sb in the raw materials tend to accumulate at grain boundaries, which can lead to grain boundary embrittlement and decreased corrosion resistance. However, element B in the raw materials can mitigate these effects, resulting in a cold-rolled corrosion-resistant steel with superior resistance to hydrochloric acid and sulfuric acid. This steel also possesses good toughness, making it less prone to fracture. The yield strength of the prepared cold-rolled corrosion-resistant steel is ≥245 MPa, the tensile strength is 360–510 MPa, and its sulfuric acid dew point corrosion rate is <3.0 mg / cm³. 2 *h, hydrochloric acid dew point corrosion rate <5.0mg / cm 2 *h, thereby effectively reducing costs;

[0027] (2) By precisely controlling the process parameters in each step of the preparation of cold-rolled corrosion-resistant steel, and combining the raw material composition of cold-rolled corrosion-resistant steel with specific components and contents, an economical cold-rolled steel plate resistant to sulfuric acid and hydrochloric acid corrosion is finally prepared. Its yield strength is ≥280MPa, tensile strength is 430~510MPa, and its sulfuric acid dew point corrosion rate is <2.08mg / cm². 2 *h, hydrochloric acid dew point corrosion rate <3.8mg / cm 2 *h can be used for structural stamping parts, heat exchange plates, etc. Attached Figure Description

[0028] Figure 1 This is a scanning electron microscope image of the cold-rolled corrosion-resistant steel prepared in Example 4 of this invention. Detailed Implementation

[0029] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0030] The first aspect of this invention discloses a raw material composition for cold-rolled corrosion-resistant steel. Based on 100% of the total mass of the raw material composition, the composition includes: 0.04–0.12% carbon, 0.50–1.25% silicon, 0.20–0.60% manganese, 0.10–0.20% phosphorus, less than 0.015% sulfur, 0.20–0.60% copper, 0.020–0.055% fused aluminum, 0.05–0.15% antimony, 0.0010–0.0020% boron, and 0.01–0.02% titanium, with the balance being iron and impurities. The cold-rolled corrosion-resistant steel prepared using this raw material composition has a yield strength ≥245 MPa, a tensile strength of 360–510 MPa, and a sulfuric acid dew point corrosion rate <3.0 mg / cm³. 2 *h, hydrochloric acid dew point corrosion rate <5.0mg / cm 2 *h.

[0031] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the carbon content can be 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.11%, or 0.12%. Carbon is the most economical strengthening element for steel, mainly improving the strength of steel through solid solution strengthening and precipitation strengthening. However, excessively high carbon content in alloy steel will deteriorate the weldability of the steel, and excessively high C content will reduce the plasticity and toughness of the material.

[0032] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the silicon content can be 0.50%, 0.55%, 0.60%, 0.62%, 0.65%, 0.86%, 0.92%, 1.02%, or 1.25%. Silicon can play a role in solid solution strengthening in steel. During the smelting process, it can be added to the steel as a reducing agent and deoxidizer. At the same time, silicon can improve the hardenability and tempering resistance of steel. The increase of Si will form SiO crystals on the surface during corrosion, which can effectively increase the wear resistance and strength of the steel plate surface. At the same time, Si combined with Cu and Sb in the steel can effectively improve the weather resistance and corrosion resistance of the steel. However, excessive Si content will reduce the toughness and weldability of the steel.

[0033] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the content of manganese can be 0.20%, 0.28%, 0.30%, 0.35%, 0.45%, 0.50%, 0.55%, or 0.60%. Manganese, as a commonly used desulfurization and deoxidation element, can prevent hot brittleness and welding hot cracks caused by FeS. At the same time, it can be infinitely dissolved in ferrite and austenite, improving the strength of the steel plate. It can also control the diffusion of C element together with hardenable elements to form local pearlite and bainite structures. However, excessive Mn will coarsen the grains, form banded structures in the steel plate, and easily cause C segregation in local locations, which will accelerate the corrosion of the steel plate in local locations. Therefore, the Mn content should not be too high.

[0034] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the content of phosphorus can be 0.10%, 0.12%, 0.13%, 0.16%, 0.18%, or 0.20%. Phosphorus can improve the corrosion resistance of steel plates. During corrosion, phosphorus accumulates inside the oxide layer, increasing the adhesion and corrosion resistance of the steel plate. However, phosphorus tends to segregate at grain boundaries in steel, thereby reducing the plasticity, low-temperature toughness, and weldability of the steel. Therefore, this patent adds a small amount of boron (B) to the steel. The increase of boron can effectively improve the problem of element segregation at grain boundaries.

[0035] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the sulfur content can be 0.012%, 0.010%, 0.008%, or 0.005%. A sulfur content higher than 0.015% will result in segregation in the steel and the formation of MnS particles with Mn in the steel. MnS particles have a negative impact on the corrosion performance of the substrate and are also detrimental to the enrichment of elements. MnS particles can also cause localized corrosion reactions in the original electrolytic cell to be aggravated, which is not conducive to improving the corrosion resistance of the substrate.

[0036] Specifically, in the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, the content of copper can be 0.20%, 0.30%, 0.35%, 0.40%, 0.44%, 0.50%, or 0.60%. Copper can form a barrier layer mainly composed of Cu and P between the matrix and the rust layer, which is firmly bonded to the matrix and provides good protection for the steel plate. In addition, Cu can also counteract the harmful effects of impurity element S in the steel plate and plays an important role in the weather resistance of the steel plate. However, excessive Cu addition will cause the problem of "Cu embrittlement". The Cu content is controlled at 0.20% to 0.60%.

[0037] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the content of acid-fused aluminum can be 0.020%, 0.030%, 0.033%, 0.035%, 0.040%, 0.050%, or 0.055%. If the content of acid-fused aluminum is less than 0.020%, it is not economical to remove oxygen from the molten steel. Oxygen content is retained in the steel, which easily leads to oxide inclusions such as voids during subsequent steel plate manufacturing, which is detrimental to the corrosion resistance of the substrate. If the content of acid-fused aluminum is higher than 0.055%, it is easy to form Al2O3 inclusion particles with the O element in the steel plate, which will also affect the strength, plasticity, and corrosion resistance of the material.

[0038] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the content of antimony can be 0.05%, 0.08%, 0.10%, 0.12%, or 0.15%. Antimony is a very effective alloying element for improving the corrosion resistance of sulfuric acid and hydrochloric acid. When combined with Cu to form Cu2Sb, it can significantly reduce the corrosion rate of hydrochloric acid and sulfuric acid. At the same time, in the mixture of sulfuric acid and hydrochloric acid, Sb and Cl act as a catalyst to promote the formation of composite compounds, thereby improving the corrosion resistance of the substrate.

[0039] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the boron content can be 0.0010%, 0.0012%, 0.0015%, 0.0018%, or 0.0020%. Boron preferentially accumulates at grain boundaries, filling "vacancies" and "defects," thus preventing the accumulation of elements such as P and Cu at these locations, which would lead to a decrease in the steel's plasticity, toughness, and corrosion resistance. Therefore, B can effectively improve the performance at grain boundaries.

[0040] In the raw material composition of the cold-rolled corrosion-resistant steel described in this invention, specifically, the content of titanium can be 0.010%, 0.012%, 0.015%, 0.016%, 0.018%, or 0.020%. Titanium has a strong affinity for C and N, and easily forms TiN and Ti(C, N) during the preparation process. This can effectively prevent austenite grain growth, pinning the grain boundaries and reducing the segregation of P and Cu at the grain boundaries, thus reducing the formation of brittle networks, which leads to a decrease in the plasticity and corrosion resistance of the material.

[0041] In a preferred embodiment of the raw material composition of the cold-rolled corrosion-resistant steel of the present invention, the raw material composition comprises, by weight (100%): 0.05–0.06% carbon, 0.65–1.25% silicon, 0.30–0.55% manganese, 0.10–0.18% phosphorus, 0.008–0.010% sulfur, 0.30–0.35% copper, 0.033–0.040% fused aluminum, 0.05–0.10% antimony, 0.0010–0.0012% boron, and 0.018–0.02% titanium, with the balance being iron and impurities. The cold-rolled corrosion-resistant steel prepared using this raw material composition exhibits a yield strength ≥280 MPa, a tensile strength of 430–510 MPa, and a sulfuric acid dew point corrosion rate <2.08 mg / cm³. 2 *h, hydrochloric acid dew point corrosion rate <3.8mg / cm 2 *h.

[0042] In a more preferred embodiment, the relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula:

[0043] (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) /

[0044] (10.25*e+1.06*f)≥20;

[0045] Where a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, and f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel.

[0046] In a further optimized scenario, the value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20 to 38.

[0047] A second aspect of this invention provides a method for preparing cold-rolled corrosion-resistant steel, the method comprising the following steps:

[0048] Step S1: Smelt the pretreated molten iron to obtain molten steel;

[0049] Step S2: The molten steel obtained in step S1 is tempered and refined to adjust the composition and content of the raw material components of the cold-rolled corrosion-resistant steel as described above.

[0050] Step S3: The molten steel obtained in step S2 is continuously cast to form a billet, and then the billet is successively subjected to hot rolling, cold rolling, continuous annealing and leveling.

[0051] In a preferred embodiment of the preparation method of the cold-rolled corrosion-resistant steel of the present invention, the raw material components of the cold-rolled corrosion-resistant steel, based on a total mass of 100%, include: 0.05-0.06% carbon, 0.65-1.25% silicon, 0.30-0.55% manganese, 0.10-0.18% phosphorus, 0.008-0.010% sulfur, 0.30-0.35% copper, 0.033-0.040% fused aluminum, 0.05-0.10% antimony, 0.0010-0.0012% boron, 0.018-0.02% titanium, with the balance being iron and impurity elements.

[0052] In a more preferred embodiment, the relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula:

[0053] (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) /

[0054] (10.25*e+1.06*f)≥20;

[0055] Where, a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel, and the value of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20.4, 24.2, 25.2, 37.2, 45.2, or 62.3.

[0056] In a further optimized scenario, the value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20 to 38.

[0057] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, the method further includes pretreatment of molten iron. During the pretreatment of molten iron, it is required to remove slag before and after the process to avoid the protective slag of molten steel being drawn into the molten steel during the casting process, which would reduce the purity of the molten steel, leave a large number of inclusions, and affect the performance of the product.

[0058] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S1, the sulfur content of the pretreated molten iron is ≤0.005%, which is beneficial to improving the corrosion resistance of the substrate.

[0059] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S1, the pretreated molten iron is transported to a converter for smelting to obtain molten steel. In the specific operation process, due to the high alloy content, the slag-blocking operation is strengthened.

[0060] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S2, the molten steel obtained in step S1 is transported to a ladle refining furnace (LF) for tempering and refining.

[0061] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S3, during the continuous casting process, the target temperature of the tundish is controlled at 10-35°C above the liquidus temperature, which improves the fluidity of the molten steel and facilitates its pouring; at the same time, the billet is cooled by stacking and slow cooling in the protective pit.

[0062] In a specific embodiment of the preparation method of cold-rolled corrosion-resistant steel according to the present invention, in step S3, the hot rolling conditions are as follows: the heating temperature is 1200-1240℃, and the heating time is ≤150min. This can avoid the enrichment of Cu elements at the grain boundaries during the heating process, thereby reducing the toughness and corrosion resistance of the cold-rolled corrosion-resistant steel; the final rolling temperature is 850-900℃. If the final rolling temperature is too high, Cu elements are prone to accumulate at the grain interface, resulting in lower plasticity of the material and poorer element uniformity in the steel, which will reduce corrosion resistance; if the final rolling temperature is too low, the production rate is slow, affecting the production rhythm. At the same time, if the temperature is too low, the cooling rate is fast, which will affect the strength of the material and increase the production risk; the coiling temperature is 550-600℃. If the coiling temperature is too high or too low, it will affect the surface oxygen pressure of the hot-rolled plate.

[0063] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S3, the cold rolling conditions are: a total reduction rate of 55-75%. Under the total reduction rate conditions described in the present invention, it is beneficial to have deformation energy storage in the steel, promote recrystallization during annealing, refine the grains, and improve the material's plasticity and toughness. In the specific operation process, the hot-rolled coil first enters the pickling tank to remove the surface iron oxide scale, and then is sent to a five-stand continuous rolling mill to be rolled to a target thickness of 0.5-2.5 mm.

[0064] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S3, the conditions for continuous annealing are: heating temperature of 790-810℃, soaking temperature of 770-800℃; annealing speed of 80-200m / min. If the annealing speed is too fast, the annealing time is short, the microstructure does not undergo sufficient recrystallization, the grain uniformity deteriorates, and the strength and plasticity of the material decrease. If the annealing speed is too slow, the steel strip stays in the furnace for a long time, the steel strip is prone to overheating, the grains grow, the surface quality of the steel plate decreases, the plasticity increases, and the strength decreases.

[0065] In a specific embodiment of the method for preparing cold-rolled corrosion-resistant steel according to the present invention, in step S3, the leveling conditions are: leveling elongation of 0.8 to 1.4%; preferably, the target value of leveling elongation is controlled at 1.2% to eliminate yield plateau.

[0066] Unless otherwise specified, the test methods or experimental methods described in the following examples are conventional methods; unless otherwise specified, the reagents and materials are obtained from conventional commercial sources or prepared by conventional methods.

[0067] (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f)=A;

[0068] The raw material composition of the cold-rolled corrosion-resistant steels of Examples 1-6 and Comparative Examples 1-5 is shown in Table 1, with the remainder being unavoidable iron and impurity elements.

[0069] Table 1. Raw material composition of cold-rolled corrosion-resistant steels in Examples 1-6 and Comparative Examples 1-5

[0070]

[0071]

[0072] The preparation methods of cold-rolled corrosion-resistant steels in Examples 1-6 and Comparative Examples 1-5 include the following steps:

[0073] Step S1: The pretreated molten iron with a sulfur content of 0.005% is transported to a converter for smelting to obtain molten steel;

[0074] Step S2: The molten steel obtained in step S1 is tempered and refined in a ladle refining furnace to adjust the composition and content of each component in the molten steel to the composition and content of the raw material components of the cold-rolled corrosion-resistant steels of Examples 1-6 and Comparative Examples 1-5.

[0075] Step S3: The molten steel obtained in step S2 is continuously cast to form a billet, and then the billet is successively hot rolled, cold rolled, continuously annealed and leveled. The main process parameters are shown in Table 2.

[0076] Table 2. Main process parameters for preparing cold-rolled corrosion-resistant steels in Examples 1-6 and Comparative Examples 1-5

[0077]

[0078]

[0079] Test case

[0080] The cold-rolled corrosion-resistant steel prepared in Example 4 was observed under a scanning electron microscope. It was found that the microstructure was mainly ferrite with a small amount of carbides. The microstructure was relatively simple. When corrosion occurred, it preferentially occurred at the carbide sites, which achieved uniform corrosion and avoided abnormal corrosion in localized areas, thus preventing the formation of an original electrolytic cell that would accelerate corrosion.

[0081] The cold-rolled corrosion-resistant steels prepared in Examples 1-6 and Comparative Examples 1-5 were tested for yield strength, tensile strength, elongation, sulfuric acid dew point corrosion rate, and hydrochloric acid dew point corrosion rate, respectively. The sulfuric acid dew point corrosion rate was tested according to GB / T28907-2012 "Steel Plates and Strips Resistant to Sulfuric Acid Dew Point Corrosion": 20℃, 20% sulfuric acid full immersion for 24h; the hydrochloric acid dew point corrosion rate was tested by 60℃, 10.5% hydrochloric acid full immersion for 6h. The results are shown in Table 3.

[0082] Table 3. Test results of cold-rolled corrosion-resistant steels in Examples 1-6 and Comparative Examples 1-5.

[0083]

[0084] As can be seen from the results of Examples 1-6 and Comparative Examples 1-5, the present invention utilizes raw material components of cold-rolled corrosion-resistant steel composed of elements such as Si (silicon), P (phosphorus), Cu (copper), Sb (antimony), and B (boron) to prepare cold-rolled corrosion-resistant steel. Since Si readily forms SiO2 particles on the steel plate surface, and P, Cu, and Sb elements readily form a dense protective layer covering the steel plate surface through interaction, the presence of SiO2 particles further enhances the strength of the protective layer. Therefore, the synergistic effect of SiO2 particles and the protective layer effectively prevents SO2 gas from entering the steel plate. The reaction of chlorine gas with sulfuric acid forms corrosive droplets on the steel plate surface, effectively improving the resistance of cold-rolled corrosion-resistant steel to hydrochloric acid and sulfuric acid. Simultaneously, elements such as Si, P, Cu, and Sb in the raw materials tend to accumulate at grain boundaries, which can lead to grain boundary embrittlement and decreased corrosion resistance. However, element B in the raw materials can mitigate these effects, resulting in a final cold-rolled corrosion-resistant steel with a yield strength ≥245 MPa, a tensile strength of 360–510 MPa, and a sulfuric acid dew point corrosion rate <3.0 mg / cm³. 2 *h, hydrochloric acid dew point corrosion rate <5.0mg / cm 2 *h.

[0085] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A raw material composition for a cold-rolled corrosion-resistant steel, characterized in that, The raw material composition of the cold-rolled corrosion-resistant steel, based on a total mass of 100%, includes: 0.04~0.12% carbon, 0.50~1.25% silicon, 0.20~0.60% manganese, 0.10~0.20% phosphorus, less than 0.015% sulfur, 0.20~0.60% copper, 0.020~0.055% acid-fused aluminum, 0.05~0.15% antimony, 0.0010~0.0020% boron, 0.01~0.02% titanium, with the balance being iron and impurity elements; The relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula: (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f)≥20; Where a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, and f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel.

2. The raw material composition of the cold-rolled corrosion-resistant steel according to claim 1, characterized in that, The raw material composition of the cold-rolled corrosion-resistant steel, based on a total mass of 100%, includes: 0.05-0.06% carbon, 0.65-1.25% silicon, 0.30-0.55% manganese, 0.10-0.18% phosphorus, 0.008-0.010% sulfur, 0.30-0.35% copper, 0.033-0.040% acid-fused aluminum, 0.05-0.10% antimony, 0.0010-0.0012% boron, 0.018-0.02% titanium, with the balance being iron and impurity elements.

3. The raw material composition of the cold-rolled corrosion-resistant steel according to claim 1, characterized in that, The value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20~38.

4. A method for preparing cold-rolled corrosion-resistant steel, characterized in that, The method includes the following steps: Step S1: Smelt the pretreated molten iron to obtain molten steel; Step S2: The molten steel obtained in step S1 is tempered and refined to adjust the composition and content of the raw material components of the cold-rolled corrosion-resistant steel as described in any one of claims 1 to 3. Step S3: The molten steel obtained in step S2 is continuously cast to form a billet, and then the billet is successively subjected to hot rolling, cold rolling, continuous annealing and leveling. The relationship between the elements in the raw material composition of the cold-rolled corrosion-resistant steel is shown in the following formula: (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f)≥20; Where a represents the mass percentage of silicon in the raw material composition of cold-rolled corrosion-resistant steel, b represents the mass percentage of copper in the raw material composition of cold-rolled corrosion-resistant steel, c represents the mass percentage of antimony in the raw material composition of cold-rolled corrosion-resistant steel, d represents the mass percentage of phosphorus in the raw material composition of cold-rolled corrosion-resistant steel, e represents the mass percentage of boron in the raw material composition of cold-rolled corrosion-resistant steel, and f represents the mass percentage of titanium in the raw material composition of cold-rolled corrosion-resistant steel.

5. The method for preparing cold-rolled corrosion-resistant steel according to claim 4, characterized in that, The raw material composition of the cold-rolled corrosion-resistant steel, based on a total mass of 100%, includes: 0.05-0.06% carbon, 0.65-1.25% silicon, 0.30-0.55% manganese, 0.10-0.18% phosphorus, 0.008-0.010% sulfur, 0.30-0.35% copper, 0.033-0.040% acid-fused aluminum, 0.05-0.10% antimony, 0.0010-0.0012% boron, 0.018-0.02% titanium, with the balance being iron and impurity elements.

6. The method for preparing cold-rolled corrosion-resistant steel according to claim 4, characterized in that, The value range of (48.5*a*b*c+56.8*d*b*c)*10+((1.26*a+3.62*d)*0.28) / (10.25*e+1.06*f) is 20~38.

7. The method for preparing cold-rolled corrosion-resistant steel according to claim 4, characterized in that, In step S1, the sulfur content of the pretreated molten iron is ≤0.005%; In step S3, the hot rolling conditions are: heating temperature of 1200~1240 ℃, heating time ≤150 min, final rolling temperature of 850~900 ℃, and coiling temperature of 550~600 ℃; The conditions for cold rolling are: a total reduction rate of 55-75%; The conditions for continuous annealing are: heating temperature of 790~810 ℃, soaking temperature of 770~800 ℃, and annealing rate of 80~200 m / min; The flattening condition is: the flattening elongation is 0.8~1.4%.

8. A cold-rolled corrosion-resistant steel prepared by the method of any one of claims 4 to 7.

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