High-strength corrosion-resistant structural steel and method for producing the same

Abstract

This application provides a high-strength corrosion-resistant structural steel and its preparation method. The high-strength corrosion-resistant structural steel is composed of the following components by mass fraction: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder being Fe and impurity elements remaining from the smelting process. This application adjusts the elemental composition and content in high-strength corrosion-resistant structural steel. In addition to adding traditional corrosion-resistant elements such as chromium, nickel, molybdenum, and copper, trace amounts of antimony and titanium are added. This results in the precipitation of a large amount of dispersed TiC, generating a second-phase strengthening effect and increasing strength; simultaneously, it inhibits the formation of Fe3C, improving toughness; and suppresses Cr... 23 The precipitation of C6 improves the steel plate's resistance to intergranular corrosion, making it suitable for coal mine operations in environments containing sulfur, chlorine, and other acidic media, as well as high-salt and high-humidity environments.

Description

Technical Field

[0001] This application relates to the field of alloy structural steel manufacturing technology, and in particular to a high-strength corrosion-resistant structural steel and its preparation method. Background Technology

[0002] Low-alloy high-strength structural steel is an economical, resource-saving, green, and high-value-added steel product. High-strength steel, as a primary load-bearing structural component, has a wide range of applications. However, it faces complex and variable mechanical load conditions and operating media, leading to numerous problems under certain special conditions. Traditional low-alloy steel is widely used in engineering machinery, but its performance in coal mining areas is poor, with premature corrosion failure preventing the high-strength steel from fulfilling its intended function.

[0003] Therefore, it is of great significance to develop an economical high-strength corrosion-resistant steel with high strength, high toughness, easy welding, and suitable for complex loads and strong corrosion conditions in coal mine environments with high sulfur, high chlorine, and high humidity. Summary of the Invention

[0004] This application provides a high-strength corrosion-resistant structural steel and its preparation method, which has high strength, high toughness, and easy welding performance. It is also suitable for coal mine environments with high sulfur, high chlorine, and high humidity, and is suitable for complex loads and strong corrosion conditions.

[0005] In a first aspect, embodiments of this application provide a high-strength corrosion-resistant structural steel, comprising the following components by mass percentage: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder being Fe and impurity elements remaining from the smelting process.

[0006] According to an embodiment of the first aspect of this application, the yield strength of the high-strength corrosion-resistant structural steel is greater than 1000 MPa.

[0007] According to an embodiment of the first aspect of this application, the tensile strength of the high-strength corrosion-resistant structural steel is greater than 1100 MPa.

[0008] According to an embodiment of the first aspect of this application, the high-strength corrosion-resistant structural steel has an impact energy of >27J at -40℃.

[0009] According to an embodiment of the first aspect of this application, the metallographic structure of the high-strength corrosion-resistant structural steel is tempered martensite and austenite.

[0010] Secondly, embodiments of this application provide a method for preparing high-strength corrosion-resistant structural steel, used to produce the aforementioned high-strength corrosion-resistant structural steel, comprising the following steps:

[0011] Continuous casting is used to obtain a billet, which is composed of the following components by mass fraction: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-0.1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the balance being Fe and impurity elements remaining from the smelting process.

[0012] The cast billet is heated in a heating furnace and rolled under controlled conditions to obtain high-strength corrosion-resistant structural steel.

[0013] According to the embodiments of the second aspect of this application, the continuous casting process includes KR desulfurization: the sulfur content is reduced to below 0.010% before the molten iron can be fed into the furnace; converter smelting: after converter smelting, the ladle is blown with argon, and the final temperature of the argon station is controlled to be greater than 1540°C; LF refining: the inlet temperature is greater than 1525°C, the LF outlet temperature is 1585-1620°C, the refining time is 40-45 minutes, the ladle is refined and the composition is fine-tuned to the target composition, and the molten steel temperature is greater than 1540°C before being transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH circulation time is 22-30 minutes.

[0014] According to an embodiment of the second aspect of this application, the continuous casting speed is controlled at 1.4-1.6 m / min, and the billet is cast using a light reduction mode.

[0015] According to an embodiment of the second aspect of this application, the billet heating temperature is 1240-1280℃, the heating time is 150-250min, and the solution treatment time is 40min.

[0016] According to the embodiment of the second aspect of this application, the billet is cooled to room temperature, the slab is heated in the furnace, and then enters a single stand for 5 passes of rough rolling, followed by 7 passes of rough rolling mill, and finally enters a laminar flow cooling system for microstructure control.

[0017] According to an embodiment of the second aspect of this application, the billet is laminar cooled after rough rolling and final rolling, with a cooling rate of 20-30℃ / s, and finally cooled to 650-630℃ before being coiled.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] This application adjusts the elemental composition and content in high-strength corrosion-resistant structural steel. In addition to adding traditional corrosion-resistant elements such as chromium, nickel, molybdenum, and copper, trace amounts of antimony are added. Specifically, the addition of 0.12-0.15% Ti precipitates a large amount of dispersed TiC, generating a second-phase strengthening effect and increasing strength; it also inhibits the formation of Fe3C, improving toughness; and inhibits Cr... 23 The precipitation of C6 improves the steel plate's resistance to intergranular corrosion. By optimizing the proportions of each element and the design and composition, a high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance in coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur and chlorine, and high-salt, high-humidity and high-heat environments. Attached Figure Description

[0020] The features, advantages, and technical effects of exemplary embodiments of this application will now be described with reference to the accompanying drawings.

[0021] Figure 1 This is the tempered metallographic structure of 6mm 1000MPa grade high-strength corrosion-resistant steel according to an embodiment of this application;

[0022] Figure 2 This is the tempered metallographic structure of 12mm 1000MPa grade high-strength corrosion-resistant steel according to an embodiment of this application;

[0023] Figure 3 The metallographic structure of the 24mm 1000MPa grade high-strength corrosion-resistant steel in the tempered state is an embodiment of this application. Detailed Implementation

[0024] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0025] In the description of this application, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. "Vertical" does not require strict verticality, but may include permissible errors. "Parallel" does not require strict parallelism, but may include permissible errors.

[0026] Traditional low-alloy steels are widely used in the field of engineering machinery, but their performance in coal mining areas is poor. They fail prematurely due to corrosion, preventing high-strength steels from fulfilling their functions.

[0027] In view of this, the inventors of this application, through extensive experimental research, provide a high-strength corrosion-resistant structural steel with high strength, high toughness, and easy weldability. It is also suitable for use in coal mine environments with high sulfur, high chlorine, and high humidity, and is applicable to complex loads and highly corrosive conditions.

[0028] High-strength corrosion-resistant structural steel

[0029] In a first aspect, embodiments of this application provide a high-strength corrosion-resistant structural steel, composed of the following components by mass fraction: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-0.1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder being Fe and impurity elements remaining from the smelting process.

[0030] This application adjusts the elemental composition and content in high-strength corrosion-resistant structural steel. In addition to adding traditional corrosion-resistant elements such as chromium, nickel, molybdenum, and copper, trace amounts of antimony are added. Specifically, the addition of 0.12-0.15% Ti precipitates a large amount of dispersed TiC, generating a second-phase strengthening effect and increasing strength; it also inhibits the formation of Fe3C, improving toughness; and inhibits Cr... 23 The precipitation of C6 improves the steel plate's resistance to intergranular corrosion. By optimizing the proportions of each element and the design and composition, a high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance in coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur and chlorine, and high-salt, high-humidity and high-heat environments.

[0031] The following section provides a detailed explanation of the roles of each chemical component in high-strength corrosion-resistant structural steel:

[0032] Carbon: In this invention, the carbon content is selected to be between 0.12% and 0.15%. Carbon is an effective and economical element for improving the strength of steel. When the carbon content is higher than 0.12%, lath martensite will be formed, ensuring strength performance. However, excessively high carbon content will reduce low-temperature toughness and deteriorate weldability and corrosion resistance. The carbon content is controlled between 0.12% and 0.15%. For example, the carbon content is 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, 0.16 wt%, or any combination of two of the above values.

[0033] Silicon: Silicon can be deoxidized during smelting, but excessive silicon content will affect weldability and toughness. Its content is controlled between 0.3% and 0.50%. For example, the silicon content is 0.3wt%, 0.31wt%, 0.32wt%, 0.33wt%, 0.34wt%, 0.35wt%, 0.36wt%, 0.37wt%, 0.38wt%, 0.39wt%, 0.4wt%, 0.41wt%, 0.42wt%, 0.43wt%, 0.44wt%, 0.45wt%, 0.46wt%, 0.47wt%, 0.48wt%, 0.49wt%, 0.5wt%, or any combination of two of the above values.

[0034] Manganese: High manganese content is beneficial for refining martensitic laths, and can improve both strength and toughness. Its content is controlled at 1.8-2.0%. For example, the manganese content is 1.0wt%, 1.1wt%, 1.2wt%, 1.3wt%, 1.4wt%, 1.5wt%, 1.6wt%, 1.7wt%, 1.8wt%, 1.9wt%, 2.0wt%, or any combination of two of the above values.

[0035] Niobium: Niobium is a carbide-forming element that can increase the recrystallization temperature of austenite, allowing austenite to be rolled at higher rolling temperatures. Furthermore, Nb plays a role in precipitation strengthening during the controlled rolling cooling process. Strain-induced precipitation of Nb carbonitrides can pin austenite grains, refine them, and improve strength and low-temperature toughness. Excessive Nb content makes it difficult to control the yield strength ratio, while excessively low Nb has an insignificant grain-refining effect. Preferably, the niobium content is controlled at 0.05-0.06%. For example, the niobium content is 0.05wt%, 0.052wt%, 0.054wt%, 0.056wt%, 0.058wt%, 0.06wt%, or any combination of two of the above values.

[0036] Titanium: During continuous casting solidification, titanium combines with nitrogen to form TiN, reducing the influence of nitrogen on boron. The presence of TiN can suppress grain coarsening in the weld heat-affected zone. Ti is a strong carbon element in steel, and it combines with carbon to form a large number of TiC second-phase particles, which can produce second-phase strengthening. On the other hand, it can suppress the bonding of Fe and C, reducing the precipitation of the brittle Fe3C phase; and suppress the bonding of Cr and C, reducing Cr... 23 C6 precipitation retains more effective Cr dissolved in the matrix, inhibiting intergranular corrosion; Ti in steel can play a cathodic protection role, which is conducive to the growth and densification transformation of the rust layer. Preferably, considering all factors, the content is 0.12-0.15%. For example, the titanium content is 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, or any combination of two of the above values.

[0037] Aluminum: Aluminum, along with a small amount of boron, promotes the formation of acicular ferrite, but excessive aluminum can impair the toughness of steel. Its content is controlled at 0.015-0.035%. For example, the aluminum content is 0.015wt%, 0.016wt%, 0.017wt%, 0.018wt%, 0.019wt%, 0.020wt%, 0.021wt%, 0.022wt%, 0.023wt%, 0.024wt%, 0.025wt%, 0.026wt%, 0.027wt%, 0.028wt%, 0.029wt%, 0.030wt%, 0.031wt%, 0.032wt%, 0.033wt%, 0.034wt%, 0.035wt%, or any range of two of the above values.

[0038] Chromium: A chromium content greater than 0.2% can improve corrosion resistance, enhance the hardenability of steel, promote the formation of martensite in lath and slabs, and improve strength. However, excessively high chromium content can increase welding difficulty. Content less than 0.35% cannot effectively exert its effect. A chromium content controlled between 0.75% and 1.0% ensures a balance between corrosion resistance and toughness. For example, the chromium content can be 0.75 wt%, 0.80 wt%, 0.85 wt%, 0.90 wt%, 0.95 wt%, 1.0 wt%, or any combination of two of these values.

[0039] Copper: Adding an appropriate amount of Cu can increase the corrosion resistance of the steel matrix against sulfides and dilute acids in coal mining media, while improving the hardenability of the steel, significantly increasing the core strength and thickness-direction uniformity of the steel plate. The synergistic effect of Cu and Sb can enhance the resistance to dilute acid corrosion. The preferred amount of copper added is 0.25-0.50%. For example, the copper content is 0.25wt%, 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt%, or any combination of two of the above values.

[0040] Antimony: Antimony is the chemical element that most significantly improves the corrosion resistance of steel in sulfuric acid environments. Sb significantly enhances the corrosion resistance of steel. However, Sb is an element that negatively impacts the strength, toughness, plasticity, and weldability of steel. Adding Sb to the metal surface can form Sb₂O₅ in corrosive media, which has higher stability than the steel matrix, thus helping to prevent further corrosion of the metal matrix by the corrosive media. In this invention, the antimony content is controlled at 0.10-0.20%, and it interacts with Cu and Mo to provide good corrosion resistance without compromising strength and toughness. Exemplarily, the antimony content is 0.10wt%, 0.11wt%, 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt%, 0.17wt%, 0.18wt%, 0.19wt%, 0.20wt%, or any combination of two of the above values.

[0041] Nickel: 0.8-0.10% can enhance the hardenability of the steel matrix, reduce the network cracking caused by copper embrittlement in copper-containing steel, and significantly improve the low-temperature toughness of the weld heat-affected zone of the base metal. On the other hand, Ni can improve the corrosion resistance of the rust layer in steel. Ni is an austenite-forming element in steel, which can promote the reverse transformation of austenite during tempering, forming a small amount of thin-film austenite, ensuring the toughness and crack arrest properties of the steel. For example, the nickel content is 0.80wt%, 0.85wt%, 0.90wt%, 0.95wt%, 1.0wt%, or any combination of two of the above values.

[0042] Molybdenum: Molybdenum can improve the thermal stability of microalloyed carbonitrides, reduce thermal deformation of steel plates during flame cutting and welding, ensure component precision, and reduce inhomogeneity in microstructure during hot working and welding. Furthermore, the addition of Mo can synergistically increase resistance to chloride ion corrosion with Cr, Ni, and Cu. Considering all factors, the preferred Mo addition amount is controlled at 0.10-0.20%. For example, the molybdenum content is 0.10 wt%, 0.12 wt%, 0.14 wt%, 0.16 wt%, 0.18 wt%, 0.20 wt%, or any combination of two of the above values.

[0043] Sulfur: Sulfur readily forms MnS inclusions in steel. MnS inclusions are detrimental to impact toughness, corrosion resistance, and weldability; therefore, its content is limited to ≤0.015%. For example, the sulfur content can be 0.001 wt%, 0.002 wt%, 0.003 wt%, 0.004 wt%, 0.005 wt%, or any combination of two of these values.

[0044] Phosphorus: Excessive phosphorus can cause grain boundary segregation, increasing the brittleness of steel. A small amount of phosphorus can increase the weather resistance of steel. The phosphorus content should be controlled to be less than 0.018%. For example, the phosphorus content is 0.001wt%, 0.002wt%, 0.003wt%, 0.004wt%, 0.005wt%, 0.006wt%, 0.007wt%, 0.008wt%, or any combination of two of the above values.

[0045] Gaseous elements such as nitrogen, oxygen, and hydrogen are extremely detrimental to the toughness of steel and should be strictly controlled: nitrogen ≤ 0.00060%, oxygen ≤ 0.00015%, and hydrogen ≤ 0.0015%.

[0046] In summary, this application achieves high-strength corrosion-resistant structural steel by adjusting the elemental composition and content in the high-strength corrosion-resistant structural steel, with each chemical component working synergistically to produce a high-strength corrosion-resistant structural steel with excellent performance. The high-strength corrosion-resistant structural steel provided by this application can meet the environmental characteristics of coal mine working conditions, including acidic media containing sulfur and chlorine, as well as high-salt and high-humidity environments.

[0047] In some embodiments, the yield strength of the high-strength corrosion-resistant structural steel is greater than 1000 MPa.

[0048] In some embodiments, the tensile strength of the high-strength corrosion-resistant structural steel is greater than 1100 MPa.

[0049] In some embodiments, the impact energy of high-strength corrosion-resistant structural steel at -40℃ is >27J.

[0050] In some embodiments, the microstructure of the high-strength corrosion-resistant structural steel consists of tempered martensite and austenite. The basic microstructure comprises tempered martensite and a small amount of reverse-transformed thin-film austenite.

[0051] In some embodiments, the corrosion rate of high-strength corrosion-resistant structural steel in a coal mine environment is less than 0.10 mm / year.

[0052] In some embodiments, the thickness of the high-strength corrosion-resistant structural steel product is 4-30 mm.

[0053] The design basis for the 1000MPa grade high-strength corrosion-resistant steel of this invention under coal mine working conditions is:

[0054] Hot rolling is based on metal deformation and phase transformation processes. Under specified deformation and temperature conditions, it completes hardening measures such as solid solution strengthening, precipitation strengthening, dislocation strengthening, and grain refinement strengthening to obtain steel plates with excellent comprehensive properties. It reduces the use of precious alloys, lowers manufacturing costs, and makes full use of the rolling and heat treatment control capabilities of continuous rolling mills. It adopts controlled rolling and accelerated cooling methods to obtain appropriately sized grains through deformation recrystallization in the high-temperature austenite region, deformation in the low-temperature non-recrystallized austenite region, and accelerated cooling after rolling.

[0055] The heat treatment process for this steel grade employs a quenching and tempering process. Isothermal solution treatment at 950℃ for 30 minutes ensures austenitization and the re-dissolution of alloying elements. Water quenching is then used to obtain a fully martensitic microstructure. High-temperature tempering at 580℃ decomposes the quenched martensitic matrix into reverse-transformed austenitic microstructure. The volume fraction of the reverse-transformed austenitic microstructure is greater than 15-20%, dividing the grains into several small spaces to achieve matrix toughening. A large amount of NbC and TiC phases precipitate between the matrix, ensuring high strength properties.

[0056] The steel composition and supporting processes used in this application produce a 1000MPa grade high-strength corrosion-resistant steel suitable for coal mine environments: yield strength: 1000MPa, tensile strength greater than 1100MPa, elongation greater than 12%, and KV2 type impact energy greater than 27J at -40℃; the actual corrosion rate under coal mine working conditions is less than 0.1mm / year.

[0057] The high-strength corrosion-resistant structural steel in this application possesses high strength, high toughness, and ease of welding. It is also suitable for use in coal mine environments with high sulfur, high chlorine, and high humidity, and is applicable to complex loads and highly corrosive conditions. This economical high-strength corrosion-resistant steel is of great significance. The successful application of this high-strength corrosion-resistant steel, compared to traditional low-alloy steel, can save 30% of steel consumption and increase service life by 5 times, possessing considerable economic and social value.

[0058] Preparation method of high-strength corrosion-resistant structural steel

[0059] Secondly, embodiments of this application provide a method for preparing high-strength corrosion-resistant structural steel, used to produce the aforementioned high-strength corrosion-resistant structural steel, comprising the following steps:

[0060] Continuous casting yields a billet composed of the following components by mass fraction: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder being Fe and impurity elements remaining from the smelting process.

[0061] High-strength corrosion-resistant structural steel is obtained by heating the billet in a heating furnace and controlling the rolling process.

[0062] This application adjusts the elemental composition and content in high-strength corrosion-resistant structural steel. In addition to adding traditional corrosion-resistant elements such as chromium, nickel, molybdenum, and copper, trace amounts of antimony are added. Specifically, the addition of 0.12-0.15% Ti precipitates a large amount of dispersed TiC, generating a second-phase strengthening effect and increasing strength; it also inhibits the formation of Fe3C, improving toughness; and inhibits Cr... 23 The precipitation of C6 improves the steel plate's resistance to intergranular corrosion. By optimizing the proportions of each element and the design and composition, a high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance in coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur and chlorine, and high-salt, high-humidity and high-heat environments.

[0063] In some embodiments, the continuous casting process includes KR desulfurization: the sulfur content is reduced to below 0.010% before the molten iron can be fed into the furnace; converter smelting: after converter smelting, the ladle is blown with argon, and the final temperature of the argon station is controlled to be greater than 1540°C; LF refining: the inlet temperature is greater than 1525°C, the LF outlet temperature is 1585-1620°C, the refining time is 40-45 minutes, the ladle is refined and the composition is fine-tuned to the target composition, and the molten steel temperature is greater than 1540°C before being transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH circulation time is 22-30 minutes.

[0064] KR desulfurization: The sulfur content must be reduced to below 0.010% before molten iron can be fed into the furnace. The composition design system in this application contains 1.8-2.0% Mn. To avoid the precipitation of MnS inclusions, the S content must be controlled to be less than 0.001%, while also ensuring good impact performance.

[0065] Converter smelting: After converter smelting, the steel ladle is blown with argon, and the final temperature of the argon station is controlled to be greater than 1540℃.

[0066] LF refining: The inlet temperature is greater than 1525℃, the outlet temperature of LF is 1585-1620℃, the refining time is 40-45 minutes, LF ladle refining and composition fine-tuning are carried out to the target composition, and the molten steel temperature is greater than 1540℃ before being transferred to RH for vacuum treatment.

[0067] The LF furnace features sophisticated temperature control and argon blowing equipment, enabling precise control of the alloy composition range. In this embodiment, the inlet and outlet temperatures are determined to be within the aforementioned range based on the production rhythm of the preceding and following processes and the alloy system.

[0068] For example, the LF outlet temperature is 1585℃, 1590℃, 1595℃, 1600℃, 1605℃, 1610℃, 1615℃, 1620℃ or any two of the above values.

[0069] RH vacuum treatment: vacuum level requirement ≤67MPa, RH cycle time 22-30min.

[0070] In order to remove elements such as H, O, and N from steel, the vacuum degree must be less than 67 MPa. In the embodiments of this application, the vacuum degree requirement and cycle time are within the above range, which can effectively remove elements such as H, O, and N.

[0071] In some embodiments, the continuous casting speed is controlled at 1.4-1.6 m / min, and the billet is cast using a light reduction mode.

[0072] In order to match the production rhythm of the entire process, the slab specifications and the characteristics of the steel grade, the continuous casting speed is controlled at 1.4-1.6 m / min in the embodiments of this application, which can obtain steel with better performance.

[0073] For example, the pulling speed is controlled within a range of 1.4 m / min, 1.45 m / min, 1.5 m / min, 1.55 m / min, 1.6 m / min or any two of the above values.

[0074] The billet is cooled to room temperature, the slab is loaded into the furnace for heating, and then enters a single stand for 5 passes of rough rolling. After that, it is rolled by a 7-pass rough rolling mill and then enters a laminar flow cooling system for microstructure control.

[0075] The slab is heated to 1240-1280℃, with a heating time of 150-250 min and a solution treatment time of 40 min.

[0076] The thermomechanical controlled rolling and cooling process is as follows: roughing rolling start temperature is 1160-1200℃, roughing rolling finish temperature is 1100-1050℃, finishing rolling start temperature is 1060-1020℃, and finishing rolling finish temperature is 880-840℃.

[0077] In order to match the production rhythm of the entire process, the temperature settings of each node, the slab specifications, the steel grade characteristics and the thermodynamic requirements of the target microstructure, the rolling parameters in this application embodiment are determined to be within the above range, so that steel with better performance can be obtained.

[0078] After roughing and final rolling, laminar flow cooling is performed at a rate of 20-30℃ / s, and the final temperature is reduced to 650-630℃ before coiling.

[0079] The inventors of this application have verified through experiments that by controlling the cooling rate to 20-30℃ / s according to thermodynamic conditions and the winding temperature to 650-630℃, the final target structure can be obtained during winding.

[0080] Example

[0081] The following embodiments describe the disclosure of this application in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of the disclosure of this application. Unless otherwise stated, all components, percentages, and ratios reported in the following embodiments are based on weight, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0082] Examples 1-3:

[0083] Molten iron is desulfurized using KR and then smelted in a 210-ton converter. It then undergoes argon blowing in a ladle, refining in an LF furnace, RH vacuum treatment, and continuous casting to form 230mm slabs. The slabs are cooled to 500℃, rough rolled in 5 passes, and then subjected to thermomechanical controlled rolling and controlled cooling on a 7-stand 2250℃ continuous rolling mill. The hot-rolled coil thicknesses are 6mm, 12mm, and 24mm. The composition of the high-strength corrosion-resistant structural steel used in this application is shown in Table 1, the controlled rolling and controlled cooling process parameters are shown in Table 2, the mechanical properties are shown in Table 3, and the test results are shown in Table 4.

[0084] The chemical composition of the high-strength corrosion-resistant structural steel in the coal mine environment is shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] The specific heating process used in the example is 1220-1260℃, with a heating time of 180-240 min in the furnace. The first stage is the initial rolling, with an initial rolling temperature of 1100-100℃. The second stage is the finishing rolling, with an initial rolling temperature of 1080-1020℃. After rolling, the steel strip is cooled using ACC-controlled cooling, and the coiling temperature is 580±15℃.

[0089] The specific rolling process parameters for each embodiment and comparative example are shown in Table 2.

[0090] Table 2

[0091]

[0092] The specific mechanical properties of each embodiment and comparative example are shown in Table 3.

[0093] Table 3

[0094]

[0095] The results of soaking in an acidic environment of 0.01 mol / L NaHSO3 and pH 4-5 are as follows:

[0096] serial number Results of hanging film for 1 year, mm / year Results of 2-year hanging film, mm / year Example 1 0.0653 0.0742 Example 2 0.0643 0.0733 Example 3 0.0682 0.0728

[0097] Figure 1 This is the tempered metallographic structure of 6mm 1000MPa grade high-strength corrosion-resistant steel according to an embodiment of this application; Figure 2 This is the tempered metallographic structure of 12mm 1000MPa grade high-strength corrosion-resistant steel according to an embodiment of this application; Figure 3 This is the tempered metallographic structure of 24mm 1000MPa grade high-strength corrosion-resistant steel according to an embodiment of this application. As can be seen from the table and pictures above, this embodiment of the application, through optimizing the proportions of each element and the design and composition, manufactures a high-strength corrosion-resistant structural steel with excellent performance, suitable for coal mine working conditions, acidic media containing sulfur and chlorine, and high-salt, high-humidity and high-heat environments.

[0098] The above embodiments are merely illustrative of the ideas and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly, without limiting the scope of protection of the present invention. All equivalent changes or modifications made according to the technical elements of the present invention should be within the scope of protection of the present invention.

Claims

1. A high-strength corrosion-resistant structural steel, characterized in that, Composed of the following components in mass fraction composition: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder is Fe and impurity elements remaining from the smelting process; The high-strength corrosion-resistant structural steel has a yield strength greater than 1000 MPa; a tensile strength greater than 1100 MPa; an impact energy at -40℃ greater than 27 J; and a metallographic structure consisting of tempered martensite and austenite.

2. A method for preparing high-strength corrosion-resistant structural steel, characterized in that, Includes the following steps: Continuous casting to obtain a billet, the billet being composed of the following components in mass fraction: Composition: C: 0.12-0.15%; Si: 0.3-0.50%; Mn: 1.8-2.0%; Nb: 0.05-0.06%; Ti: 0.12-0.15%; Cr: 0.75-1.0%; Ni: 0.8-1.0%; Cu: 0.25-0.50%; Mo: 0.10-0.20%; Sb: 0.10-0.20%; Als: 0.015-0.035%; N≤0.00060%; O≤0.00015%; H≤0.0015%; S≤0.015%; P≤0.018%; the remainder is Fe and impurity elements remaining from the smelting process. The billet is heated in a heating furnace and rolled under controlled conditions to obtain high-strength corrosion-resistant structural steel. The high-strength corrosion-resistant structural steel has a yield strength greater than 1000 MPa, a tensile strength greater than 1100 MPa, an impact energy at -40℃ greater than 27 J, and a metallographic structure consisting of tempered martensite and austenite.

3. The preparation method according to claim 2, characterized in that, Before continuous casting, the process includes KR desulfurization: the sulfur content is reduced to below 0.010% before the molten iron can be fed into the furnace; converter smelting: after converter smelting, the ladle is argon-blown, and the final temperature of the argon station is controlled to be greater than 1540℃; LF refining: the inlet temperature is greater than 1525℃, the LF outlet temperature is 1585-1620℃, the refining time is 40-45 minutes, the ladle refining and composition fine-tuning are carried out to the target composition, and the molten steel temperature is greater than 1540℃ before being transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH circulation time is 22-30min.

4. The preparation method according to claim 2, characterized in that, The continuous casting speed is controlled at 1.4-1.6 m / min, and the billet is cast using a light reduction mode.

5. The preparation method according to claim 2, characterized in that, The billet is heated at a temperature of 1240-1280℃ for 150-250 minutes and the solution treatment time is 40 minutes.

6. The preparation method according to claim 2, characterized in that, The billet is cooled to room temperature, the slab is heated in the furnace, and then enters a single stand for 5 passes of rough rolling. After that, it is rolled by a 7-pass rough rolling mill and then enters a laminar flow cooling system for microstructure control.

7. The preparation method according to claim 2, characterized in that, The billet is cooled by laminar flow after rough rolling and final rolling at a cooling rate of 20-30℃ / s, and finally cooled to 650-630℃ before being coiled.

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