High-strength and corrosion-resistant steel plate with compact oxide layer formed on surface

Abstract

The invention discloses a high-strength and corrosion-resistant steel plate with a compact oxide layer formed on the surface, and relates to the technical field of weather-resistant steel plates and production processes thereof. A novel and stable ferrite matrix structure is designed through the elements C, Mn, Cr, Ni and Cu, a compact oxide layer is formed between a surface layer and a matrix after heat treatment by utilizing the stabilizing effect of the elements on a ferrite phase and the influence on a phase change structure, and the compact oxide film can protect the matrix below the surface layer to greatly relieve the corrosion speed, so that the corrosion resistance of the matrix is improved, and the service life of the matrix is prolonged. Oxygen and water in the atmosphere are effectively prevented from permeating into steel, and the corrosion resistance of a steel material is greatly improved. The obtained corrosion-resistant steel plate achieves balance of high strength and high toughness, meanwhile, the production technology is simple, large-scale production can be achieved, and the corrosion-resistant steel plate is more suitable for steel for steel structures exposed in the atmosphere for a long time for railways, vehicles, bridges, towers, photovoltaics, expressways and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of weathering steel plates and production processes thereof, in particular to a high-strength, corrosion-resistant steel plate with a dense oxide layer formed on the surface. Background Art

[0002] Every year, the amount of metal equipment and materials scrapped due to corrosion in the world is equivalent to 20% to 40% of the annual metal production. On the other hand, steel structures used in railways, vehicles, bridges, towers, photovoltaics, highways, etc. that are exposed to the atmosphere for a long time are welded from plain carbon steel and need to be sprayed with paint to ensure the corrosion resistance of the steel structure. This is labor-intensive and material-intensive and does not meet environmental protection requirements, making weathering steel plates more suitable for the above-mentioned steel structures exposed to the atmosphere for a long time.

[0003] Weathering steel plate, also known as atmospheric corrosion-resistant steel, is a type of steel with excellent corrosion resistance. It is a low-alloy, high-strength structural steel plate and is divided into high-weathering structural steel and weathering steel for welded structures based on its main characteristics. Compared with ordinary carbon steel, weathering steel plate has better corrosion resistance in the atmosphere. Compared with ordinary stainless steel, it adds a small amount of alloying elements to ordinary carbon steel to form a dense oxide film on its surface, thereby effectively resisting atmospheric corrosion. The total amount of alloying elements added, such as phosphorus, copper, nickel, vanadium, and titanium, is only 4.3-5.3% of the total content, while the alloying elements of stainless steel can reach 16%, so the price is cheaper than ordinary stainless steel.

[0004] Weathering steel plates can effectively resist corrosion factors such as moisture, oxygen, and salt in the atmosphere, thereby extending the service life of steel structures and having excellent corrosion resistance. At the same time, due to the good corrosion resistance of weathering steel plates, there is no need for frequent anti-corrosion measures such as spraying paint, thereby reducing maintenance costs and labor costs. Accordingly, weathering steel plates reduce the use of anti-corrosion materials such as paint, meet environmental protection requirements, and help reduce pollution to the environment; weathering steel plates are not only corrosion-resistant, but also have good mechanical properties, which can meet the needs of various engineering structures, and weathering steel plates will gradually form a stable rust layer in the natural environment. This rust layer not only has a protective effect, but also can present a unique aesthetic effect.

[0005] For steel structures exposed to the atmosphere for long periods of time, the use of weathering steel plates is an economical, environmentally friendly, and durable option. For example, invention patent ZL2020101169915 provides a high-strength weathering steel having the following chemical composition by weight: C 0.06-0.07%, Si 0.23-0.26%, Mn 1.40-1.50%, P ≤ 0.009%, S ≤ 0.007%, Al ≤ 0.015%, Ni 0.0-0.19%, Cr 0.0-0.51%, Cu 0.31-0.33%, Ti 0.11-0.12%, Nb 0.030-0.036%, Sb 0.0-0.09%, N ≤ 0.055%, with the remainder being Fe and unavoidable impurities. The yield strength of high-strength weathering steel is between 636MPa and 710MPa, the tensile strength is between 698MPa and 775MPa, the elongation is between 23% and 26%, and the -40℃ V-notch impact energy is between 54 and 77J. Although this invention patent achieves a balance between high strength, high plasticity and high toughness, it relies on obtaining a nearly all-ferrite matrix structure and significantly reducing the dislocation density to achieve weather resistance. This is theoretically feasible, but due to limitations in cost, efficiency, quality, equipment, performance, market, environmental protection and technology, this method is not suitable for large-scale production.

[0006] To this end, the present invention proposes a new high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface, which has higher performance than existing weathering steel. Summary of the Invention

[0007] (1) Technical problems solved In response to the shortcomings of the existing technology, the present invention provides a high-strength, corrosion-resistant steel plate with a dense oxide layer formed on the surface, which solves the problem that the current method of producing weathering steel achieves a balance of high strength, high plasticity and high toughness, but relies on obtaining a nearly fully ferrite matrix structure, greatly reducing the additional volume of grain boundaries, and greatly reducing the dislocation density to achieve weather resistance. Although it is theoretically feasible, due to limitations in cost, efficiency, quality, equipment, performance, market, environmental protection and technology, this method is not suitable for large-scale production.

[0008] (2) Technical solution The object of the present invention is to provide a high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface, so as to solve the problems raised in the above-mentioned background technology.

[0009] To achieve the above-mentioned object, the present invention provides the following technical solution: a high-strength, corrosion-resistant steel plate with a dense oxide layer formed on the surface, comprising the following chemical components in weight percentage: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest being iron and unavoidable impurities.

[0010] Through the above technical solution, a new stable ferrite matrix structure is designed using C, Mn, Cr, Ni, and Cu elements, mainly utilizing the stabilizing effect of these elements on the ferrite phase, the influence on phase transformation, and their behavior during heat treatment. After heat treatment, the ferrite with the above chemical composition can form a dense oxide layer between the surface and the matrix.

[0011] Preferably, a method for producing a high-strength corrosion-resistant steel plate from the above chemical composition is provided, comprising the following specific steps: Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heating to 1020°C at 120°C / h and keeping warm for 1 hour; then cooling to 930-950°C at 65°C / h and keeping warm for 0.5 hour; then water quenching heat treatment is performed, and the water outlet temperature is less than 100°C; finally, heating to 360-380°C at 90°C / h, keeping warm for 4-5 hours, and air cooling to obtain the final finished high-strength corrosion-resistant steel plate.

[0012] Through the above technical solution, in practical applications, the technical solution of the present application can solve existing technical problems and is a more economical, efficient and feasible production method, thereby promoting large-scale production by simplifying the production technology.

[0013] Preferably, the high-strength corrosion-resistant steel plate obtained as the final product after heat treatment has the following properties: hardness ≥ 280HB, yield strength ≥ 750MPa, tensile strength ≥ 870MPa, elongation ≥ 18%, and V-notch impact energy ≥ 63J at -40°C.

[0014] Preferably, a dense oxide layer is formed between the surface layer and the substrate of the high-strength corrosion-resistant steel plate.

[0015] Through the above technical solution, because this dense oxide film can protect the substrate under the surface, the corrosion rate is greatly reduced, and it can prevent oxygen and water in the atmosphere from penetrating into the steel, greatly improving the corrosion resistance of the steel material.

[0016] Preferably, the weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.69 to 0.75 g / (m 2 ·h).

[0017] The carbon content plays a crucial role in determining the microstructure and mechanical properties of steel. Lower carbon content improves toughness but reduces strength and hardness. Higher carbon content improves strength and hardness, but reduces toughness. Manufacturing steel pipes and formed steel for outdoor use requires greater power. Therefore, the carbon content was ultimately determined to be between 0.18% and 0.22%.

[0018] Preferably, the manganese (Mn) can significantly reduce the martensitic transformation temperature and phase transformation rate of the steel, thereby improving the hardenability of the steel. Mn can dissolve in the iron matrix to achieve solid solution strengthening, improving the steel's microstructure. The final Mn content was determined to be 1.8%-2.0%.

[0019] Preferably, Si is a good deoxidizer, existing as a solid solution in ferrite or austenite. This reduces the austenite phase, favoring the formation of martensite, significantly improving the steel's elastic limit, yield strength, and yield strength ratio, and enhancing fatigue strength. Si also reduces the diffusion rate of carbon in ferrite, increasing the steel's structural stability. However, excessive Si content can cause massive ferrite to form in the steel, significantly reducing the steel's plasticity, toughness, and ductility. Taking all factors into consideration, the final Si content is controlled within a range of 0.5% to 0.8%.

[0020] Cr is an essential element in weathering steel. It forms an infinite solid solution with iron and, when properly combined with Mn and Si, enhances solid solution strengthening. It reduces the austenite phase and slows austenite decomposition, significantly improving the hardenability of the steel. Cr also contributes to the corrosion resistance of steel. However, excessive Cr content significantly increases the ductile-brittle transition temperature, so it is best controlled within a range of 0.9% to 1.0%.

[0021] Preferably, the Ni can make the steel have higher toughness under ultra-high strength, improve the heat resistance, corrosion resistance and acid resistance of the steel, and ultimately the Ni content is controlled at 0.42%-0.64%.

[0022] Preferably, the Cu can increase the corrosion resistance of the material. Too little Cu will not have any corrosion resistance effect, and too much Cu will reduce the mechanical properties of the steel. The content is ultimately controlled at 0.4-0.6%.

[0023] (3) Beneficial effects The present invention provides a high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface. Compared with the prior art, the present invention has the following beneficial effects: A new stable ferrite matrix structure is designed by using C, Mn, Cr, Ni, and Cu elements. By utilizing the stabilizing effect of these elements on the ferrite phase, their influence on phase transformation, and their behavior during heat treatment, the ferrite with the above chemical composition forms a dense oxide layer between the surface and the matrix after heat treatment. Because this dense oxide film can protect the matrix below the surface, the corrosion rate is greatly reduced, and it can prevent oxygen and water in the atmosphere from penetrating into the steel, greatly improving the corrosion resistance of the steel material. In addition, the performance of the high-strength corrosion-resistant steel plate obtained after heat treatment in the present application is as follows: hardness ≥ 280HB, yield strength ≥ 750MPa, tensile strength ≥ 870MPa, elongation ≥ 18%, V-notch impact energy ≥ 63J at -40°C, and the weight loss rate of the high-strength corrosion-resistant steel plate after heat treatment after 150 cycles of circumferential immersion accelerated corrosion is 0.69-0.75g / (m 2 h), the resulting corrosion-resistant steel plate achieves a balance of high strength, high ductility and high toughness, has high toughness and excellent welding performance, and is simple to produce on a large scale, making it more suitable for use in steel structures exposed to the atmosphere for long periods of time, such as railways, vehicles, bridges, towers, photovoltaics, and highways. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A process flow chart of forming a dense oxide layer on the surface of a high-strength corrosion-resistant steel plate provided by an embodiment of the present invention; Figure 2 Schematic diagram of the metallographic structure of the corrosion-resistant steel plate with a dense oxide layer formed on the surface in Table 3 provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See also Figure 1-Figure 2The present invention provides a high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface, comprising the following chemical components in weight percentage: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest being iron and unavoidable impurities.

[0027] Among them, specifically, the C is the main alloying element in steel, and its content plays a decisive role in the microstructure and mechanical properties of steel. It can increase the strength and hardness of steel, but reduce toughness and plasticity. In ferrite, the solubility of carbon is low, and too high a carbon content will lead to the formation of pearlite or martensite. When the C content is low, the toughness is better, but the strength and hardness are insufficient; when the C content is high, the strength and hardness of the steel will be improved, but the toughness will decrease, and the manufacture of steel pipes and formed steel for outdoor use requires a larger power drive. Therefore, the carbon content was finally determined to be 0.18%-0.22%. During the heat treatment process, carbon can be used to adjust the microstructure and properties of steel through quenching and tempering. Quenching can increase the supersaturation of carbon in ferrite, while tempering helps the precipitation of carbon and the stabilization of ferrite; At the same time, Si is a good deoxidizer and can exist in ferrite or austenite in the form of solid solution. It can reduce the austenite phase area, which is conducive to the formation of martensite, significantly improving the elastic limit, yield strength and yield strength ratio of steel, and improving fatigue strength. Si element can also reduce the diffusion rate of carbon in ferrite and increase the structural stability of steel; however, when the Si element content is too high, blocky ferrite structure will appear in the steel, significantly reducing the plasticity, toughness and ductility of the steel. Taking all factors into consideration, the final Si content is controlled at 0.5%-0.8%; At the same time, the Mn can significantly reduce the martensitic transformation temperature and phase transformation rate of the steel, thereby improving the hardenability of the steel. Mn can be dissolved in the iron matrix to play a role in solid solution strengthening, stabilize the ferrite, improve the strength and hardness of the steel, while maintaining good toughness, and improve the structure of the steel. It can also reduce the critical cooling rate of the steel, which is beneficial to the quenching process. The element with the final Mn content is determined to be 1.8%-2.0%. Manganese can promote the formation of austenite during heat treatment and improve the hardenability of steel. During the tempering process, manganese helps to inhibit the precipitation of carbides and maintain the stability of ferrite; At the same time, Cr is an essential element of weathering steel and a ferrite-stabilizing element, significantly improving the corrosion and oxidation resistance of steel. Chromium also increases the strength and hardness of steel, and can form an infinite solid solution with iron. When properly combined with Mn and Si, it enhances the solid solution strengthening effect, shrinking the austenite phase and slowing the decomposition rate of austenite, significantly improving the hardenability of steel. Furthermore, Cr has a certain effect on improving the corrosion resistance of steel; however, excessive Cr content significantly increases the ductile-brittle transition temperature of steel, and is ultimately controlled within a range of 0.9%-1.0%. During the tempering process of heat treatment, chromium helps form stable chromium carbides, further stabilizing ferrite. At the same time, Ni is an austenite stabilizing element, but it can also improve the strength and toughness of steel in ferrite. Nickel can also improve the low-temperature toughness of steel, making the steel have higher toughness at ultra-high strength, and improve the heat resistance, corrosion resistance, and acid resistance of steel. Ultimately, controlling Ni within 0.42%-0.64% can inhibit the transformation of ferrite to austenite during heat treatment, which is beneficial to maintaining the ferrite matrix. During the tempering process, nickel helps maintain the toughness and plasticity of the steel. At the same time, the Cu can increase the corrosion resistance of the material, especially in atmospheric environments. Copper can also improve the strength of steel, but has little effect on its toughness. Too little will not have any anti-corrosion effect, and too much will reduce the mechanical properties of the steel. The addition of copper is usually used to improve the corrosion resistance of steel, and is ultimately controlled at 0.4-0.6%. The behavior of copper in heat treatment is similar to that of nickel, and it can inhibit the transformation of ferrite to austenite. The design of a new stable ferrite matrix structure through the elements of C, Mn, Cr, Ni and Cu is mainly based on the stabilizing effect of these elements on the ferrite phase, the influence on phase transformation and their behavior during heat treatment. After heat treatment, the ferrite with the above chemical composition forms a dense oxide layer between the surface and the matrix. Because this dense oxide film can protect the matrix under the surface, the corrosion rate is greatly reduced, and it can prevent oxygen and water in the atmosphere from penetrating into steel, greatly improving the corrosion resistance of steel materials.

[0028] Based on the chemical composition of the above raw materials in weight percentage, the present application also provides a method for producing a high-strength corrosion-resistant steel plate from the above chemical composition, comprising the following specific steps: Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heating to 1020°C at 120°C / h and keeping warm for 1 hour; then cooling to 930-950°C at 65°C / h and keeping warm for 0.5 hour; then water quenching heat treatment is performed, and the water outlet temperature is less than 100°C; finally, heating to 360-380°C at 90°C / h, keeping warm for 4-5 hours, and air cooling to obtain the final finished high-strength corrosion-resistant steel plate. Example

[0029] Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.182%; Si: 0.52%; Mn: 1.87%; Cr: 1.0%; Ni: 0.63%; Cu: 0.51%; P≤0.02%; S≤0.02%, and the remainder is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heat to 1020°C at 120°C / h and keep warm for 1 hour; then cool to 930°C at 65°C / h and keep warm for 0.5 hour; perform (water) quenching treatment, with the water outlet temperature less than 100°C; finally, heat to 260°C at 90°C / h, keep warm for 4-5 hours, and air cool.

[0030] The properties of the high-strength corrosion-resistant steel plate obtained after heat treatment are as follows: hardness: 283HB, yield strength: 752MPa, tensile strength: 871MPa, elongation: 20.0%, -40°C V-notch impact energy: 65J; The weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.75g / (m 2 ·h). Example

[0031] Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.191%; Si: 0.67%; Mn: 1.91%; Cr: 0.97%; Ni: 0.57%; Cu: 0.55%; P≤0.02%; S≤0.02%, and the remainder is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heat to 1020℃ at 120℃ / h and keep warm for 1h; then cool to 935℃ at 65℃ / h and keep warm for 0.5h; perform water quenching heat treatment, with the water outlet temperature less than 100℃; finally, heat to 270℃ at 90℃ / h, keep warm for 4-5h, and air cool.

[0032] The high-strength corrosion-resistant steel plate obtained after heat treatment has the following properties: hardness: 290 HB, yield strength: 760 MPa, tensile strength: 874 MPa, elongation: 19.6%, -40°C V-notch impact energy: 69 J; The weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.73g / (m 2 ·h). Example

[0033] Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.202%; Si: 0.7%; Mn: 1.94%; Cr: 0.93%; Ni: 0.52%; Cu: 0.65%; P≤0.02%; S≤0.02%, and the remainder is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heat to 1020℃ at 120℃ / h and keep warm for 1h; then cool to 940℃ at 65℃ / h and keep warm for 0.5h; perform water quenching heat treatment, with the water outlet temperature less than 100℃; finally, heat to 275℃ at 90℃ / h, keep warm for 4-5h, and air cool.

[0034] The high-strength corrosion-resistant steel plate obtained after heat treatment has the following properties: hardness greater than 293HB, yield strength 764MPa, tensile strength 889MPa, elongation 19.0%, and -40°C V-notch impact energy 71J; The weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.71g / (m 2 ·h).

[0035] Example 4 Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.21%; Si: 0.78%; Mn: 2.0%; Cr: 0.91%; Ni: 0.43%; Cu: 0.67%; P≤0.02%; S≤0.02%, and the remainder is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heat to 1020℃ at 120℃ / h and keep warm for 1h; then cool to 950℃ at 65℃ / h and keep warm for 0.5h; perform water quenching heat treatment, with the water outlet temperature less than 100℃; finally, heat to 280℃ at 90℃ / h, keep warm for 4-5h, and air cool.

[0036] The high-strength corrosion-resistant steel plate obtained after heat treatment has the following properties: hardness greater than 298 HB, yield strength 778 MPa, tensile strength 892 MPa, elongation 18.5%, and -40°C V-notch impact energy 73 J; The weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.69g / (m 2 ·h).

[0037] Comparative Example The technical solution proposed in invention patent ZL2020101169915 includes the following chemical compositions by weight: C: 0.06-0.07%, Si 0.23-0.26%, Mn 1.40-1.50%, P ≤ 0.009%, S ≤ 0.007%, Al ≤ 0.015%, Ni 0.0-0.19%, Cr 0.0-0.51%, Cu 0.31-0.33%, Ti 0.110-0.12%, Nb 0.030-0.036%, Sb 0.0-0.09%, N ≤ 0.055%. An almost fully ferrite structure is obtained by rapid cooling to the ferrite phase transformation range, followed by coiling and slow cooling. Among them, the rolling process specifically includes the following process steps: heating the forged steel billet to 1200℃ and keeping it warm for a period of time, then performing the first stage rolling and temperature control and the second stage rolling and temperature control. After the second stage rolling and temperature control are completed, the steel is quickly cooled to 560-656℃.

[0038] The finished weathering steel has the following properties: yield strength between 636MPa and 710MPa, tensile strength between 698MPa and 775MPa, elongation between 23% and 26%, and -40℃ V-notch impact energy between 54 and 77J. The weight loss rate of the obtained finished high-strength weathering steel after 150 cycles of immersion accelerated corrosion is 1.0-1.28 g / (m 2 ·h).

[0039] Table 1 Comparison of chemical compositions of Examples 1-3 and Comparative Example 1 (by weight percentage) Material C Si Mn Ni Cr Cu Nb P S Al Ti Sb N Example 1 0.182 0.52 1.87 0.63 1.00 0.51 - 0.02 0.02 - - - - Example 2 0.191 0.67 1.91 0.57 0.97 0.55 - 0.02 0.02 - - - - Example 3 0.202 0.70 1.94 0.52 0.93 0.61 - 0.02 0.02 - - - - Example 4 0.210 0.78 2.00 0.43 0.91 0.67 - 0.02 0.02 - - - - Comparative Example 1 0.065 0.25 1.45 0.15 0.31 0.32 0.03 0.009 0.007 0.015 0.11 0.03 0.05 Table 2 Comparison of material properties of Examples 1-3 and Comparative Example 1 Example Yield strength / MPa Tensile strength / MPa Elongation / % Impact energy-40℃ / J Brinell hardness / HB <![CDATA[150 cycle weightlessness rate g / m 2 ·h]]> Example 1 752 871 20.0 65 283 0.75 Example 2 760 874 19.6 69 290 0.73 Example 3 764 889 19.0 71 293 0.71 Example 4 778 892 18.5 73 298 0.69 Comparative Example 1 636-710 698-775 23-26 54-77 1.0-1.28 Table 3 Metallographic structure of corrosion-resistant steel plate with dense oxide layer formed on the surface surface layer Figure a Ferrite + Pearlite dense oxide layer Figure b <![CDATA[Mixture of SiO2, TiO2, CuO, and MnO2]]> matrix Figure c Ferrite structure In summary, the performance of the high-strength corrosion-resistant steel plate obtained by the present application after heat treatment is as follows: hardness ≥ 280HB, yield strength ≥ 750MPa, tensile strength ≥ 870MPa, elongation ≥ 18%, V-notch impact energy ≥ 63J at -40°C, and the weight loss rate of the high-strength corrosion-resistant steel plate after heat treatment after 150 cycles of circumferential immersion accelerated corrosion is 0.69-0.75g / (m 2 h); Yield strength refers to the critical point at which a material transitions from elastic deformation to plastic deformation when subjected to stress. In other words, when the stress on a material reaches its yield strength, it will begin to permanently deform.

[0040] Tensile strength: refers to the maximum stress value that a material can withstand during the stretching process. It is usually an important indicator used to measure the maximum bearing capacity (maximum stress value) of a material when subjected to tensile force.

[0041] Elongation: This indicates the maximum degree of plastic deformation a material can achieve before breaking under tension, usually expressed as a percentage. The higher the elongation, the better the material's plasticity, and its ability to withstand greater deformation without breaking.

[0042] -40°C V-notch impact energy: This is a measure of a material's impact resistance at low temperatures. Specifically, it indicates the energy absorbed by the material during a V-notch impact test at -40°C. A higher value indicates better low-temperature impact resistance.

[0043] Weight loss after 150 cycles of cyclic immersion accelerated corrosion: This is an indicator for evaluating a material's corrosion resistance. The method involves periodically immersing and drying a material sample in a specific corrosive environment. After 150 cycles, the weight loss of the sample is measured. The lower the weight loss, the better the material's corrosion resistance.

[0044] These indicators together constitute a comprehensive evaluation of the performance of the steel plate, including its mechanical properties, plastic deformation capacity, low-temperature impact resistance and corrosion resistance, corresponding to the data listed in Tables 1 and 2 above: Compared with the comparative example, Examples 1-4 of the technical solution of the present application have higher yield strength, tensile strength and -40°C V-notch impact energy, and at the same time have lower weight loss rate after 150 cycles of cyclic immersion accelerated corrosion. This enables the corrosion-resistant steel plate obtained by the technical solution of the present application to achieve a balance of high strength, high plasticity and high toughness, while the production technology is simple and can be mass-produced. Specifically, the production method of the high-strength weathering steel described above in the comparative example includes the following steps: smelting, casting, forging, and rolling of the steel material to obtain a nearly fully ferrite matrix structure, significantly reducing the excess volume of grain boundaries and dislocation density to achieve weather resistance. However, the reasons why it is not suitable for large-scale production are mainly the following: 1. Long heat treatment cycle: In order to achieve the ideal microstructure, long heat treatment may be required, which will reduce production efficiency; 2. Complex process: Precise control of grain boundary volume and dislocation density requires complex process parameter control, which increases the complexity and difficulty of production operations.

[0045] 3. Quality control: consistency is difficult to ensure. In large-scale production, it is very difficult to maintain the same microstructure and performance in each batch of products. At the same time, detection is difficult: precise detection of the microstructure is required, which requires advanced testing equipment and professional personnel, increasing the cost and difficulty of quality control.

[0046] 4. Special equipment requirements: Special smelting, casting and heat treatment equipment are required, which have high investment and maintenance costs.

[0047] 5. Material performance limitations: Balance of mechanical properties: Although the nearly all-ferrite matrix structure is beneficial to weather resistance, it may sacrifice other mechanical properties such as strength and hardness, which limits its application range.

[0048] Weathering resistance limitations: Improved weathering resistance may only be significant in certain environments, while the effect may not be obvious in other environments.

[0049] 6. Market demand: Specific application limitations: This material may only be suitable for specific application scenarios, has limited market demand, and is not suitable for large-scale production.

[0050] 7. Technology maturity: Increased technological risks: The application of new technologies and new processes involves certain risks, and requires time and cost for technical verification and optimization.

[0051] In summary, although it is theoretically feasible to obtain a nearly fully ferrite matrix structure to improve weather resistance, this method is not suitable for large-scale production due to limitations in cost, efficiency, quality, equipment, performance, market, environmental protection, and technology. In practical applications, it is necessary to comprehensively consider these factors and find a more economical, efficient, and feasible production method. The technical solution of the present application can solve the above technical problems, simplify the production technology, and thus promote large-scale production.

[0052] Furthermore, the technical solution of the present application designs a new stable ferrite matrix structure through C, Mn, Cr, Ni, and Cu elements, and forms a dense oxide layer between the surface and the matrix after heat treatment. Because this dense oxide film can protect the matrix under the surface, the corrosion rate is greatly reduced, and it can prevent oxygen and water in the atmosphere from penetrating into the steel, greatly improving the corrosion resistance of the steel material.

[0053] The corrosion-resistant steel plate provided by the present invention, which forms a dense oxide layer on its surface, exhibits a hardness of 280 HB or higher, a yield strength of 750 MPa or higher, a tensile strength of 870 MPa or higher, and an elongation of 18% or higher. Its weathering resistance is 3-4 times that of ordinary carbon steel. The corrosion-resistant steel plate exhibits high toughness and excellent welding properties, making it suitable for use in steel structures exposed to the atmosphere for long periods of time, such as railways, vehicles, bridges, towers, photovoltaic systems, and high-speed projects.

[0054] It should be noted that, in this article, the term "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such article or device. The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the present invention.

[0055] It should be noted that the above examples are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above examples, and many similar variations are possible. All variations directly derived from or associating with the present invention by those skilled in the art are intended to fall within the scope of protection of the present invention.

[0056] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-strength, corrosion-resistant steel plate having a dense oxide layer formed on its surface, characterized in that: The invention comprises the following chemical components in weight percentage: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest is iron and unavoidable impurities.

2. The high-strength, corrosion-resistant steel plate having a dense oxide layer formed on the surface according to claim 1, characterized in that: A method for producing a high-strength, corrosion-resistant steel plate from the above chemical composition is provided, comprising the following specific steps: Step 1: First, ingredients are added sequentially into an electric arc furnace, and a preliminary finished steel plate is obtained after continuous casting and rolling. The mass percentage of the components of the obtained preliminary finished steel plate is as follows: C: 0.18%-0.22%; Si: 0.5%-0.8%; Mn: 1.8%-2.0%; Cr: 0.9%-1.0%; Ni: 0.42%-0.64%; Cu: 0.5%-0.7%; P≤0.02%; S≤0.02%, and the rest is iron and unavoidable impurities; Step 2: The above-mentioned preliminary finished steel plate is heat treated. The heat treatment process is as follows: first, heating to 1020°C at 120°C / h and keeping warm for 1 hour; then cooling to 930-950°C at 65°C / h and keeping warm for 0.5 hour; then water quenching heat treatment is performed, and the water outlet temperature is ≤100°C; finally, heating to 360-380°C at 90°C / h, keeping warm for 4-5 hours, and air cooling to obtain a high-strength, corrosion-resistant steel plate.

3. The high-strength, corrosion-resistant steel plate having a dense oxide layer formed on the surface according to claim 2, characterized in that: The obtained high-strength, corrosion-resistant steel plate has the following properties: hardness ≥ 280HB, yield strength ≥ 750MPa, tensile strength ≥ 870MPa, elongation ≥ 18%, and V-notch impact energy ≥ 63J at -40°C.

4. The high-strength, corrosion-resistant steel plate having a dense oxide layer formed on the surface according to claim 2, characterized in that: A dense oxide layer is formed between the surface layer and the substrate of the high-strength corrosion-resistant steel plate.

5. The high-strength, corrosion-resistant steel plate with a dense oxide layer formed on the surface according to claim 2, characterized in that: The weight loss rate of the heat-treated high-strength, corrosion-resistant steel plate after 150 cycles of immersion accelerated corrosion is 0.69-0.75 g / (m 2 ·h).

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