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

Abstract

The invention discloses a high-strength 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, by means of the stabilizing effect of the elements on a ferrite phase, the influence of the elements on phase change and the behaviors of the elements in the heat treatment process, a compact oxide layer is formed between a surface layer and a matrix after ferrite with the chemical components is subjected to heat treatment, and due to the fact that the compact oxide layer is formed, the corrosion resistance of the ferrite is improved, and the service life of the ferrite is prolonged. The corrosion-resistant steel plate can protect a base body under the surface layer, the corrosion speed is greatly relieved, oxygen and water in the atmosphere can be prevented from permeating into steel, the corrosion capacity of a steel material is greatly improved, the obtained corrosion-resistant steel plate achieves balance of high strength, high plasticity and high toughness, meanwhile, the production technology is simple, large-scale production can be achieved, and the production cost is low. And the steel is more suitable for steel structures exposed in the atmosphere for a long time, such as railways, vehicles, bridges, towers, photovoltaics, high-abrasion and slow engineering and the like.

Description

Technical Field

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

[0002] Every year in the world, the metal equipment and materials scrapped due to corrosion are equivalent to 20 - 40% of the annual metal output. Moreover, the corrosion of steel reduces the service life of steel structures, causes casualties and economic losses, and the emissions cause environmental pollution. On the other hand, steel structures used in railways, vehicles, bridges, towers, photovoltaic, high-speed projects, etc., which are exposed to the atmosphere for a long time, are welded from plain carbon steel and need to be painted to ensure the corrosion resistance of the steel structure. This is labor-intensive and material-consuming 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 plates, also known as atmospheric corrosion-resistant steel, are a type of steel with excellent corrosion resistance. They belong to low-alloy high-strength structural steel plates and are divided into high-weathering structural steel and weathering steel for welded structures according to their main characteristics. Compared with ordinary carbon steel, weathering steel plates have better corrosion resistance in the atmosphere. Compared with ordinary stainless steel, by adding a small amount of alloying elements on the basis of ordinary carbon steel, a dense oxide film is formed on its surface, thus effectively resisting atmospheric corrosion. The alloying elements added, such as phosphorus, copper, nickel, vanadium, titanium, etc., the total amount of alloying elements is only a few percent of the total content, while the alloying elements of stainless steel can reach more than ten percent, so the price is cheaper than that of ordinary stainless steel.

[0004] Moreover, weathering steel plates can effectively resist corrosion factors such as moisture, oxygen, and salts in the atmosphere, thus 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, anti-corrosion measures such as frequent painting are not required, thus reducing maintenance costs and labor costs. Correspondingly, weathering steel plates reduce the use of anti-corrosion materials such as paint, meet environmental protection requirements, and are beneficial to reducing environmental pollution; weathering steel plates not only have corrosion resistance but also have good mechanical properties and can meet the requirements of various engineering structures. Moreover, 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] Generally speaking, for steel structures exposed to the atmosphere for a long time, using weathering steel plates is an economical, environmentally friendly, and durable choice.

[0006] As the invention patent ZL2020101169915 provides a high-strength weathering steel, the high-strength weathering steel contains the following chemical components by weight percentage: 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%, and the balance is Fe and inevitable impurities. The yield strength of the high-strength weathering steel is between 636 MPa and 710 MPa, the tensile strength is between 698 MPa and 775 MPa, the elongation is between 23% and 26%, and the -40°C V-notch impact energy is between 54 J and 77 J. Although this invention patent achieves the balance of high strength, high plasticity and high toughness, by obtaining a nearly fully ferritic matrix structure, significantly reducing the extra volume of grain boundaries, and significantly reducing the dislocation density to achieve weather resistance, it is theoretically feasible. However, due to various limitations such as cost, efficiency, quality, equipment, performance, market, environmental protection and technology, this method is not suitable for large-scale production.

[0007] Therefore, we propose a new high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface. Summary of the Invention

[0008] (I) Technical problems to be solved

[0009] Aiming at the deficiencies of the prior art, the present invention provides a high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface, and solves the problem that although the current method of producing weathering steel achieves the balance of high strength, high plasticity and high toughness, by obtaining a nearly fully ferritic matrix structure, significantly reducing the extra volume of grain boundaries, and significantly reducing the dislocation density to achieve weather resistance, it is theoretically feasible. However, due to various limitations such as cost, efficiency, quality, equipment, performance, market, environmental protection and technology, this method is not suitable for large-scale production.

[0010] (II) Technical solutions

[0011] The purpose of the present invention is to provide a high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface to solve the problems raised in the above background technology.

[0012] To achieve the above object, the present invention provides the following technical solutions: A high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface, comprising the following chemical components by 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 balance is iron and unavoidable impurities.

[0013] Through the above technical solutions, a new type of stable ferrite matrix structure is designed by using elements such as C, Mn, Cr, Ni, and Cu. Mainly, the stabilizing effect of these elements on the ferrite phase, the influence on phase transformation, and their behavior during the heat treatment process are utilized. After the ferrite heat treatment of the above chemical components, a dense oxide layer can be formed between the surface layer and the matrix.

[0014] Preferably, a method for manufacturing the high-strength corrosion-resistant steel plate with the above chemical components is provided, comprising the following specific steps:

[0015] Step 1: First, add the ingredients in an electric arc furnace in sequence, and obtain a preliminary finished steel plate after casting. The mass percentages of the detected components of the obtained preliminary finished steel plate are: 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 balance is iron and unavoidable impurities;

[0016] Step 2: Perform heat treatment on the above preliminary finished steel plate. The heat treatment process is to first heat it to 1020°C at a rate of 120°C / h and hold for 1 h; then cool it to 930 - 950°C at a rate of 65°C / h and hold for 0.5 h; then perform (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat it to 360 - 380°C at a rate of 90°C / h and hold for 4 - 5 h, and air-cool to obtain the final finished high-strength corrosion-resistant steel plate.

[0017] Through the above technical solutions, in practical applications, the technical solutions of the present application can solve the existing technical problems, and it is a more economical, efficient, and feasible production method, thereby promoting large-scale production by making the production technology simple.

[0018] Preferably, the properties of the obtained high-strength corrosion-resistant steel plate after heat treatment are: hardness greater than 280 HB, yield strength ≥ 750 MPa, tensile strength ≥ 870 MPa, elongation rate ≥ 18%, and V-notch impact energy at -40°C ≥ 63 J.

[0019] Preferably, a dense oxide layer is formed between the surface layer and the matrix of the high-strength corrosion-resistant steel plate.

[0020] Through the above technical solution, because of this dense oxide film, the matrix under the surface layer can be protected, and the corrosion rate is greatly alleviated. It can prevent oxygen and water in the atmosphere from penetrating into the steel, and greatly improve the corrosion resistance of the steel material.

[0021] Preferably, the weight loss rate of the high-strength corrosion-resistant steel plate after circumferential immersion accelerated corrosion for 150 cycles after heat treatment is 0.69 - 0.75 g / (m 2 ·h).

[0022] Preferably, the C content plays a decisive role in the microstructure and mechanical properties of the steel: when the C content is low, the toughness is good, but the strength and hardness are insufficient; when the C content is high, both the strength and hardness of the steel will increase, but the toughness will decrease, and a larger driving force is required to manufacture steel pipes and shaped steels used outdoors. Therefore, the carbon content is finally determined to be 0.18% - 0.22%.

[0023] Preferably, Mn can significantly reduce the martensite 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 and improve the structure of the steel. The final determined Mn content element is 1.8% - 2.0%.

[0024] Preferably, Si is a good deoxidizer and can exist in the form of solid solution in ferrite or austenite. It can narrow the austenite phase region, be beneficial to the formation of martensite, significantly improve the elastic limit, yield strength and yield ratio of the steel, and improve the fatigue strength. The Si element can also reduce the diffusion rate of carbon in ferrite and increase the structural stability of the steel; however, when the Si element content is too high, massive ferrite structure will appear in the steel, significantly reducing the plasticity, toughness and ductility of the steel. Considering comprehensively, the final Si content is controlled at 0.5% - 0.8%.

[0025] Preferably, Cr is a basic element of weathering steel and can be infinitely dissolved with iron element. When reasonably combined with Mn and Si elements, it can improve the solid solution strengthening effect. It has the effect of narrowing the austenite phase region and slowing down the austenite decomposition rate, and can significantly improve the hardenability of the steel. In addition, the Cr element has a certain effect on improving the corrosion resistance of the steel; however, when its content is too high, the ductile-brittle transition temperature of the steel is significantly increased, and it is finally controlled at 0.9% - 1.0.

[0026] Preferably, Ni can make the steel have high toughness under ultra-high strength, improve the heat resistance, corrosion resistance and acid resistance of the steel, and finally control Ni at 0.42% - 0.64%.

[0027] Preferably, the Cu can increase the corrosion resistance of the material. Too little Cu cannot play the role of corrosion resistance, while too much Cu will reduce the mechanical properties of the steel. Finally, it is controlled at 0.4 - 0.6%.

[0028] (III) Beneficial Effects

[0029] The present invention provides a high-strength corrosion-resistant steel plate with a dense oxide layer formed on its surface. Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] By designing a new type of stable ferrite matrix structure with elements C, Mn, Cr, Ni, and Cu, and utilizing the stabilizing effect of these elements on the ferrite phase, the influence on phase transformation, and their behaviors during the heat treatment process, a dense oxide layer is formed between the surface layer and the matrix of the ferrite with the above chemical composition after heat treatment. Because of this dense oxide film, it can protect the matrix under the surface layer, greatly alleviate the corrosion rate, prevent oxygen and water in the atmosphere from infiltrating into the steel, and greatly improve the corrosion resistance of the steel material;

[0031] Moreover, the properties of the high-strength corrosion-resistant steel plate obtained after heat treatment in this application are as follows: the hardness is greater than 280 HB, the yield strength ≥ 750 MPa, the tensile strength ≥ 870 MPa, the elongation rate ≥ 18%, the V-notch impact energy at -40 °C ≥ 63 J. At the same time, the weight loss rate of the high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion acceleration corrosion is 0.69 - 0.75 g / (m 2 ·h). The obtained corrosion-resistant steel plate achieves a balance of high strength, high plasticity, and high toughness, has high toughness and excellent welding performance. At the same time, the production technology is simple and can be mass-produced, and it is more suitable for use as steel for steel structures that are exposed to the atmosphere for a long time, such as railways, vehicles, bridges, towers, photovoltaics, and high-abrasion and high-speed projects. Description of the Drawings

[0032] Figure 1 It is a process flow chart of a high-strength corrosion-resistant steel plate with a dense oxide layer formed on its surface provided by an embodiment of the present invention. Detailed Embodiments

[0033] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to Figure 1, the present invention provides a high-strength corrosion-resistant steel plate with a dense oxide layer formed on its surface, comprising the following chemical components by 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 balance is iron and unavoidable impurities.

[0035] Specifically, among them, the C is the main alloying element in the steel, and its content plays a decisive role in the microstructure and mechanical properties of the steel. It can improve the strength and hardness of the steel, but will reduce the toughness and plasticity. In ferrite, the solubility of carbon is relatively 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 good, but the strength and hardness are insufficient; when the C content is high, both the strength and hardness of the steel will increase, but the toughness will decrease, and a larger driving force is required to manufacture steel pipes and shaped steels used outdoors. Therefore, the carbon content is finally determined to be 0.18% - 0.22%. During the heat treatment process, carbon can adjust the microstructure and properties of the 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;

[0036] At the same time, the Si is a good deoxidizer and can exist in ferrite or austenite in the form of a solid solution. It can narrow the austenite phase region, is conducive to the formation of martensite, significantly improve the elastic limit, yield strength and yield ratio of the steel, and improve the fatigue strength. The Si element can also reduce the diffusion rate of carbon in ferrite and increase the tissue stability of the steel; however, when the Si element content is too high, massive ferrite tissue will appear in the steel, significantly reducing the plasticity, toughness and ductility of the steel. Considering comprehensively, the final Si content is controlled at 0.5% - 0.8%;

[0037] At the same time, the Mn can significantly reduce the martensite 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 ferrite, improve the strength and hardness of the steel, while maintaining good toughness, improving the structure of the steel, and it can also reduce the critical cooling rate of the steel, which is conducive to quenching treatment. The final determined Mn content element is 1.8% - 2.0%. Manganese can promote the formation of austenite during heat treatment and improve the hardenability of the steel. During the tempering process, manganese helps to inhibit the precipitation of carbides and maintain the stability of ferrite;

[0038] Meanwhile, the Cr is a basic element of weathering steel and is a ferrite stabilizing element, which can significantly improve the corrosion resistance and oxidation resistance of the steel. Chromium can also increase the strength and hardness of the steel, can be infinitely solid-solved with iron element, and can improve the solid-solution strengthening effect when reasonably combined with Mn and Si elements. It has the effects of shrinking the austenite phase region and slowing down the decomposition rate of austenite, and can significantly improve the hardenability of the steel. In addition, the Cr element plays a certain role in improving the corrosion resistance of the steel; however, when its content is too high, the ductile-brittle transition temperature of the steel is significantly increased, and finally it is controlled at 0.9%-1.0%. During the tempering process of heat treatment, chromium helps to form stable chromium carbides and further stabilize the ferrite;

[0039] Meanwhile, the Ni is an austenite stabilizing element, but it can also increase the strength and toughness of the steel in ferrite. Nickel can also improve the low-temperature toughness of the steel, enabling the steel to have high toughness under ultra-high strength, and improving the heat resistance, corrosion resistance, and acid resistance of the steel. Finally, Ni is controlled at 0.42%-0.64%. During heat treatment, it can inhibit the transformation of ferrite to austenite, which is beneficial to maintaining the ferrite matrix. During the tempering process, nickel helps to maintain the toughness and plasticity of the steel;

[0040] Meanwhile, the Cu can increase the corrosion resistance of the material, especially in the atmospheric environment. Copper can also increase the strength of the steel, but has little impact on its toughness. Too little amount cannot play the role of corrosion resistance, and too much amount will reduce the mechanical properties of the steel. The addition of copper is usually used to improve the corrosion resistance of the steel, and finally it is controlled at 0.4-0.6%. The behavior of copper during heat treatment is similar to that of nickel, and it can inhibit the transformation of ferrite to austenite;

[0041] By designing a new type of stable ferrite matrix structure with 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 behaviors during the heat treatment process, a dense oxide layer is formed between the surface layer and the matrix of the ferrite after heat treatment of the above chemical composition. Because of this dense oxide film, it can protect the matrix under the surface layer, greatly relieve the corrosion rate, prevent oxygen and water in the atmosphere from infiltrating into the steel, and greatly improve the corrosion resistance of the steel material.

[0042] Based on the chemical composition of the above raw material weight percentages, the present application also provides a method for making the above chemical composition into a high-strength corrosion-resistant steel plate, including the following specific steps:

[0043] Step 1: First, add ingredients into the electric arc furnace in sequence. After casting, a preliminary finished steel plate is obtained. The mass percentages of the detected components of the obtained preliminary finished steel plate are 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 inevitable impurities;

[0044] Step 2: Perform heat treatment on the above-mentioned preliminary finished steel plate. The heat treatment process is as follows: first heat to 1020°C at a rate of 120°C / h and hold for 1 h; then cool to 930 - 950°C at a rate of 65°C / h and hold for 0.5 h; subsequently, perform (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat to 360 - 380°C at a rate of 90°C / h and hold for 4 - 5 h, and then air cool to obtain the final finished high-strength corrosion-resistant steel plate.

[0045] Example 1

[0046] Step 1: First, add ingredients into the electric arc furnace in sequence. After casting, a preliminary finished steel plate is obtained. The mass percentages of the detected components of the obtained preliminary finished steel plate are as follows: C: 0.182%; Si: 0.52%; Mn: 1.87%; Cr: 0.91%; Ni: 0.43%; Cu: 0.51%; P ≤ 0.02%; S ≤ 0.02%, and the rest is iron and inevitable impurities;

[0047] Step 2: Perform heat treatment on the above-mentioned preliminary finished steel plate. The heat treatment process is as follows: first heat to 1020°C at a rate of 120°C / h and hold for 1 h; then cool to 930°C at a rate of 65°C / h and hold for 0.5 h; perform (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat to 260°C at a rate of 90°C / h and hold for 4 - 5 h, and then air cool.

[0048] The properties of the heat-treated final finished high-strength corrosion-resistant steel plate obtained are as follows: hardness: 283 HB, yield strength: 752 MPa, tensile strength: 871 MPa, elongation: 18.5%, -40°C V-notch impact energy: 65 J;

[0049] And the weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion corrosion is 0.75 g / (m 2 ·h).

[0050] Example 2

[0051] Step 1. First, add ingredients into the electric arc furnace in sequence. After casting, a preliminary finished steel plate is obtained. The mass percentages of the detected components of the obtained preliminary finished steel plate are as follows: C: 0.191%; Si: 0.67%; Mn: 1.91%; Cr: 0.93%; Ni: 0.52%; Cu: 0.55%; P≤0.02%; S≤0.02%, and the rest is iron and inevitable impurities;

[0052] Step 2. Conduct heat treatment on the above-mentioned preliminary finished steel plate. The heat treatment process is to heat it to 1020°C at a rate of 120°C / h and hold for 1 h first; then cool it to 935°C at a rate of 65°C / h and hold for 0.5 h; conduct (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat it to 270°C at a rate of 90°C / h and hold for 4 - 5 h, and then air cool.

[0053] The properties of the finally obtained high-strength corrosion-resistant steel plate after heat treatment are as follows: hardness: 290 HB, yield strength: 760 MPa, tensile strength: 874 MPa, elongation: 19.0%, -40°C V-notch impact energy: 69 J;

[0054] And the weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion accelerated corrosion is 0.73 g / (m 2 ·h).

[0055] Example 3

[0056] Step 1. First, add ingredients into the electric arc furnace in sequence. After casting, a preliminary finished steel plate is obtained. The mass percentages of the detected components of the obtained preliminary finished steel plate are as follows: C: 0.202%; Si: 0.7%; Mn: 1.94%; Cr: 0.97%; Ni: 0.57%; Cu: 0.65%; P≤0.02%; S≤0.02%, and the rest is iron and inevitable impurities;

[0057] Step 2. Conduct heat treatment on the above-mentioned preliminary finished steel plate. The heat treatment process is to heat it to 1020°C at a rate of 120°C / h and hold for 1 h first; then cool it to 940°C at a rate of 65°C / h and hold for 0.5 h; conduct (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat it to 275°C at a rate of 90°C / h and hold for 4 - 5 h, and then air cool.

[0058] The properties of the finally obtained high-strength corrosion-resistant steel plate after heat treatment are as follows: hardness greater than 293 HB, yield strength 764 MPa, tensile strength 889 MPa, elongation 19.6%, -40°C V-notch impact energy 71 J;

[0059] And the weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion accelerated corrosion is 0.71 g / (m 2 ·h).

[0060] Example 4

[0061] Step 1: First, add ingredients into the electric arc furnace in sequence. After casting, a preliminary finished steel plate is obtained. The mass percentages of the detected components of the obtained preliminary finished steel plate are as follows: C: 0.21%; Si: 0.78%; Mn: 2.0%; Cr: 1.0%; Ni: 0.63%; Cu: 0.67%; P≤0.02%; S≤0.02%, and the rest is iron and inevitable impurities;

[0062] Step 2: Perform heat treatment on the above-mentioned preliminary finished steel plate. The heat treatment process is to heat it to 1020°C at a rate of 120°C / h and hold for 1 h; then cool it to 950°C at a rate of 65°C / h and hold for 0.5 h; perform (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat it to 280°C at a rate of 90°C / h and hold for 4 - 5 h, and then air-cool.

[0063] The properties of the obtained high-strength corrosion-resistant steel plate after heat treatment are as follows: hardness is greater than 298 HB, yield strength is 778 MPa, tensile strength is 892 MPa, elongation is 20.0%, and -40°C V-notch impact energy is 73 J;

[0064] And the weight loss rate of the heat-treated high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion corrosion is 0.69 g / (m 2 ·h).

[0065] Comparative Example

[0066] The technical solution proposed in the invention patent ZL2020101169915, which includes the following chemical components by weight percentage: 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%. By rapidly cooling to the ferrite phase transformation range, followed by coiling and slow cooling, an almost fully ferritic structure is obtained;

[0067] Among them, the rolling process specifically includes the following technological steps: heating the forged steel billet to 1200°C and holding 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 rapidly cooled to 560 - 656°C.

[0068] The properties of the obtained weathering steel product are as follows: the yield strength is between 636 MPa and 710 MPa, the tensile strength is between 698 MPa and 775 MPa, the elongation is between 23% and 26%, and the -40°C V-notch impact energy is between 54 J and 77 J;

[0069] And the weight loss rate of the obtained high-strength weathering steel product after 150 cycles of cyclic immersion accelerated corrosion is 1.0 - 1.28 g / (m 2 ·h).

[0070] Table 1 Chemical composition comparison of Examples 1 - 3 and Comparative Example 1 (by weight percentage)

[0071] Material C Si Mn Ni Cr Cu Nb P S Al Ti Sb N Example 1 0.182 0.52 1.87 0.43 0.91 0.51 - 0.02 0.02 - - - - Example 2 0.191 0.67 1.91 0.52 0.93 0.55 - 0.02 0.02 - - - - Example 3 0.202 0.70 1.94 0.57 0.97 0.61 - 0.02 0.02 - - - - Example 4 0.210 0.78 2.00 0.63 1.00 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

[0072] Table 2 Material property comparison of Examples 1 - 3 and Comparative Example 1

[0073]

[0074] Table 3 Metallographic structure of the corrosion-resistant steel plate with a dense oxide layer formed on the surface

[0075]

[0076] In summary, the properties of the high-strength corrosion-resistant steel plate of the final product obtained in this application after heat treatment are as follows: the hardness is greater than 280 HB, the yield strength ≥ 750 MPa, the tensile strength ≥ 870 MPa, the elongation ≥ 18%, the -40°C V-notch impact energy ≥ 63 J. At the same time, the weight loss rate of the high-strength corrosion-resistant steel plate after 150 cycles of cyclic immersion accelerated corrosion is 0.69 - 0.75 g / (m 2 ·h);

[0077] Among them, the yield strength: indicates the critical point at which a material transitions from elastic deformation to plastic deformation when subjected to stress. In other words, when the stress applied to the material reaches the yield strength, it will start to undergo permanent deformation.

[0078] The tensile strength: refers to the maximum stress value that a material can withstand during the tensile process and is usually an important indicator for measuring the maximum load-bearing capacity (maximum stress value) of a material when subjected to a tensile force.

[0079] The elongation: represents the maximum degree of plastic deformation that a material can reach before tensile fracture and is usually expressed as a percentage. The higher the elongation, the better the plasticity of the material, indicating that it can withstand greater deformation without cracking.

[0080] -40°C V-notch impact energy: This is an indicator to measure the impact resistance of materials in low-temperature environments. Specifically, it represents the energy absorbed by the material in the V-notch specimen impact test under the low-temperature condition of -40°C. The higher this value, the better the impact resistance of the material at low temperatures.

[0081] Weight loss rate after 150 cycles of cyclic immersion accelerated corrosion: This is an indicator to evaluate the corrosion resistance of materials. The specific method is to immerse and dry the material specimen periodically in a specific corrosion environment. After 150 cycles, the weight loss rate of the specimen is measured. The lower the weight loss rate, the better the corrosion resistance of the material.

[0082] These indicators together constitute a comprehensive evaluation of the performance of the steel plate, including its mechanical properties, plastic deformation ability, low-temperature impact resistance, and corrosion resistance, corresponding to the data listed in Table 1 and Table 2 above:

[0083] Compared with the comparative example, Examples 1-4 of the technical solution of this application have higher yield strength, tensile strength, and -40°C V-notch impact energy, and at the same time have a lower weight loss rate after 150 cycles of cyclic immersion accelerated corrosion, enabling the corrosion-resistant steel plate obtained by the technical solution of this application to achieve a balance of high strength, high plasticity, and high toughness. At the same time, the production technology is simple and can be mass-produced;

[0084] Specifically, the production method of the high-strength weathering steel as described above in the comparative example includes: steel smelting, casting, forging, and rolling processes to obtain a nearly fully ferritic matrix structure, significantly reducing the extra volume of grain boundaries and dislocation density to achieve weather resistance. The main reasons why it is not suitable for mass production include the following points:

[0085] 1. Long heat treatment cycle: To achieve an ideal microstructure, long heat treatment may be required, which reduces production efficiency;

[0086] 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.

[0087] 3. Quality control: Consistency is difficult to guarantee. In mass production, it is very difficult to ensure that each batch of products has the same microstructure and performance;

[0088] At the same time, the detection is difficult: Precise detection of the microstructure is required, which requires advanced detection equipment and professional personnel, increasing the cost and difficulty of quality control.

[0089] 4. Requirement for special equipment: Special smelting, casting, and heat treatment equipment are required, and the investment and maintenance costs of these equipment are relatively high.

[0090] 5. Material property limitations:

[0091] Mechanical property balance: Although a nearly fully ferritic matrix structure is beneficial for weather resistance, it may sacrifice other mechanical properties such as strength and hardness, which limits its application scope.

[0092] Weather resistance limitations: The improvement of weather resistance may be significant only in specific environments, while it may not be obvious in other environments.

[0093] 6. Market demand: Specific application limitations: This material may only be suitable for specific application scenarios, with limited market demand and not suitable for large-scale production.

[0094] 7. Technology maturity: Increased technical risks: The application of new technologies and new processes has certain risks and requires time and costs for technical verification and optimization.

[0095] In summary, although obtaining a nearly fully ferritic matrix structure to improve weather resistance is theoretically feasible, due to various limitations such as cost, efficiency, quality, equipment, performance, market, environmental protection, and technology, this method is not suitable for large-scale production. In practical applications, these factors need to be comprehensively considered to find a more economical, efficient, and feasible production method. The technical solution of this application can solve the above technical problems and achieve a simple production technology, thus promoting large-scale production.

[0096] Furthermore, the technical solution of this application designs a new type of stable ferritic matrix structure through elements C, Mn, Cr, Ni, and Cu. After heat treatment, a dense oxide layer is formed between the surface layer and the matrix. Because of this dense oxide film, it can protect the matrix under the surface layer, greatly alleviating the corrosion rate, preventing oxygen and water in the atmosphere from penetrating into the steel, and greatly improving the corrosion resistance of the steel material.

[0097] For the properties of the corrosion-resistant steel plate with a dense oxide layer formed on the surface provided by the present invention, the hardness ≥ 280 HB, the yield strength ≥ 750 MPa, the tensile strength ≥ 870 MPa, the elongation ≥ 18%, and the weather resistance can reach 3 - 4 times that of ordinary carbon steel. The corrosion-resistant steel plate of the present invention has high toughness and excellent welding performance and can be used for steel structures such as railways, vehicles, bridges, towers, photovoltaics, and high-speed projects that are exposed to the atmosphere for a long time.

[0098] It should be noted that in this text, the term "including" or any of its other variants is intended to cover non-exclusive inclusion, so that an article or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or elements inherent to such article or device. The above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the present invention.

[0099] It should be noted that the above-listed are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and there are many similar variations. All deformations directly derived or associated by those skilled in the art from the disclosed content of the present invention shall fall within the protection scope of the present invention.

[0100] The above is only a preferred embodiment of the present invention, and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A high-strength corrosion-resistant steel plate with a dense oxide layer formed on its surface, characterized in that, It includes chemical components with the following weight percentages: 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 inevitable impurities.

2. The high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface according to claim 1, characterized in that A method for making the above chemical components into a high-strength corrosion-resistant steel plate is provided, including the following specific steps: Step 1: First, add ingredients in an electric arc furnace in sequence, and obtain a preliminary finished steel plate after casting. The mass percentages of the detected components of the obtained preliminary finished steel plate are: 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 inevitable impurities; Step 2: Perform heat treatment on the above preliminary finished steel plate. The heat treatment process is to first heat it to 1020°C at a rate of 120°C / h and hold for 1 h; then cool it to 930 - 950°C at a rate of 65°C / h and hold for 0.5 h; then carry out (water) quenching treatment, and the water outlet temperature < 100°C; finally, heat it to 360 - 380°C at a rate of 90°C / h and hold for 4 - 5 h, and air-cool to obtain the final finished high-strength corrosion-resistant steel plate.

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

4. The high-strength corrosion-resistant steel plate with a dense oxide layer formed on the surface according to claim 2, wherein, A dense oxide layer is formed between the surface layer and the matrix 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 high-strength corrosion-resistant steel plate after heat treatment after 150 cycles of cyclic immersion accelerated corrosion is 0.69 - 0.75 g / (m 2 ·h).

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