High-strength corrosion-resistant structural steel and preparation method thereof

Abstract

The invention provides high-strength corrosion-resistant structural steel and a preparation method thereof. The high-strength corrosion-resistant structural steel is composed of the following components in percentage by mass: 0.12-0.15% of C; 0.3 to 0.50 percent of Si; 1.8 to 2.0 percent of Mn; 0.05% to 0.06% of Nb; 0.12% to 0.15% of Ti; 0.75 to 1.0 percent of Cr; 0.8 to 1.0 percent of Ni; 0.25 to 0.50 percent of Cu; 0.10% to 0.20% of Mo; 0.10% to 0.20% of Sb; the content of Als is 0.015 to 0.035 percent; n < = 0.00060%; o < = 0.00015%; h < = 0.0015%; less than or equal to 0.015% of S; p is less than or equal to 0.018%; the balance is Fe and residual impurity elements in the smelting process. By adjusting the element components and the content of the element components in the high-strength corrosion-resistant structural steel, on the basis that traditional chromium, nickel, molybdenum and copper are added to improve corrosion-resistant elements, trace antimony elements and titanium elements are added, on one hand, a large amount of dispersed TiC is separated out to generate second-phase strengthening, and the strength is improved; on one hand, formation of Fe3C is inhibited, and toughness is improved; the corrosion-resistant steel plate is suitable for the working condition of a coal mine and the high-salt and high-humidity environment containing sulfur, chlorine and other acid media.

Description

Technical Field

[0001] The present application relates to the technical field of alloy structural steel manufacturing, and in particular to a high-strength corrosion-resistant structural steel and a preparation method thereof. Background Art

[0002] Low-alloy high-strength structural steel is an economical, resource-saving, green and high-value-added steel product. High-strength steel is the main load-bearing structural component with a wide range of applications. The mechanical load conditions and medium conditions faced are complex and changeable, and many problems also arise under some special conditions. Traditional low-alloy steel is widely used in the field of engineering machinery, but the effect of use in coal mining areas is not good. It fails prematurely due to corrosion, making the function of high-strength steel unable to be exerted.

[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 high sulfur, high chlorine, and high humidity in coal mine environments and suitable for complex loads and strong corrosion conditions. Summary of the invention

[0004] The embodiments of the present application provide a high-strength corrosion-resistant structural steel and a preparation method thereof, which has high strength, high toughness, and easy welding performance, and is suitable for high sulfur, high chlorine, and high humidity in coal mine environments, and is suitable for complex loads and strong corrosion conditions.

[0005] In a first aspect, an embodiment of the present application provides a high-strength corrosion-resistant structural steel, comprising the following components in percentage by mass: 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 rest are Fe and impurity elements remaining during the smelting process.

[0006] According to an embodiment of the first aspect of the present 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 the present 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 the present application, the -40°C impact energy of the high-strength corrosion-resistant structural steel is greater than 27J.

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

[0010] In a second aspect, an embodiment of the present application provides a method for preparing high-strength corrosion-resistant structural steel, which is used to produce the above-mentioned high-strength corrosion-resistant structural steel, comprising the following steps:

[0011] Continuously casting to obtain a casting billet, the casting billet consists 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 rest are Fe and impurity elements remaining in the smelting process;

[0012] The ingot is heated in a heating furnace and subjected to controlled rolling to obtain high-strength corrosion-resistant structural steel.

[0013] According to the embodiment of the second aspect of the present application, the continuous casting step includes KR desulfurization: the sulfur content is removed to below 0.010% before the molten iron can enter the furnace; converter smelting: after converter smelting, argon is blown through the ladle, and the terminal control temperature of the argon station is greater than 1540°C; LF refining: the station entry temperature is greater than 1525°C, the LF station exit temperature is 1585-1620°C, the refining time is 40-45 minutes, the furnace refining and composition fine-tuning to the target composition, the molten steel temperature is greater than 1540°C and transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH cycle time is 22-30min.

[0014] According to an embodiment of the second aspect of the present application, the continuous casting speed is controlled at 1.4-1.6 m / min, and the casting is carried out in a light reduction mode.

[0015] According to an embodiment of the second aspect of the present application, the heating temperature of the ingot is 1240-1280°C, the heating time is 150-250 minutes, and the solution time is 40 minutes.

[0016] According to the embodiment of the second aspect of the present application, the ingot is cooled to room temperature, the slab is loaded into the furnace for heating, and enters a single frame for 5 rough rolling passes, and then rolled by a rough rolling unit for 7 passes. After rolling, it enters a laminar cooling system for tissue control.

[0017] According to an embodiment of the second aspect of the present application, the ingot is laminar-cooled after rough rolling and final rolling, with a cooling rate of 20-30°C / s, and finally cooled to 650-630°C for coiling.

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

[0019] The present invention adjusts the element components and their contents in high-strength corrosion-resistant structural steel, and adds trace antimony elements on the basis of adding traditional chromium, nickel, molybdenum and copper to improve corrosion resistance; in particular, adding 0.12-0.15% Ti, on the one hand, precipitates a large amount of dispersed TiC to produce second phase strengthening and improve strength; on the other hand, inhibits Fe 3 The formation of C improves toughness and inhibits the formation of Cr 23 C 6 The precipitation of elements improves the intergranular corrosion resistance of the steel plate; by optimizing the ratio of each element, design and composition, high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance under coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur, chlorine, and high salt, high humidity and heat environments. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 1 This is the tempered metallographic structure of the 6mm 1000MPa grade high strength corrosion resistant steel in the embodiment of the present application;

[0022] Figure 2 This is the tempered metallographic structure of the 12mm 1000MPa grade high strength corrosion resistant steel in the embodiment of the present application;

[0023] Figure 3 This is the tempered metallographic structure of the 24mm 1000MPa grade high strength corrosion resistant steel in the embodiment of the present application. DETAILED DESCRIPTION

[0024] The following detailed description and drawings of the embodiments of the present application are used to illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0025] In the description of the present application, it should be noted that, unless otherwise specified, "multiple" means more than two; the terms "upper", "lower", "left", "right", "inside", "outside", etc., indicating the orientation or positional relationship are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" does not require verticality in the strict sense, but may include allowable errors. "Parallel" does not require parallelism in the strict sense, but may include allowable errors.

[0026] Traditional low-alloy steels are widely used in the field of engineering machinery, but they are not very effective in coal mining areas because they fail prematurely due to corrosion, making it impossible for high-strength steel to perform its functions.

[0027] In view of this, the inventor of this application has conducted a lot of experimental research and provided a high-strength corrosion-resistant structural steel with high strength, high toughness, and easy welding performance. It is also suitable for high sulfur, high chlorine, and high humidity in coal mine environments and is suitable for complex loads and strong corrosion conditions.

[0028] High strength corrosion resistant structural steel

[0029] In a first aspect, an embodiment of the present application provides a high-strength corrosion-resistant structural steel, composed of the following components in 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 rest are Fe and impurity elements remaining in the smelting process.

[0030] The present invention adjusts the element components and their contents in high-strength corrosion-resistant structural steel, and adds trace antimony elements on the basis of adding traditional chromium, nickel, molybdenum and copper to improve corrosion resistance; in particular, adding 0.12-0.15% Ti, on the one hand, precipitates a large amount of dispersed TiC to produce second phase strengthening and improve strength; on the other hand, inhibits Fe 3 The formation of C improves toughness and inhibits the formation of Cr 23 C 6The precipitation of elements improves the intergranular corrosion resistance of the steel plate; by optimizing the ratio of each element, design and composition, high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance under coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur, chlorine, and high salt, high humidity and heat environments.

[0031] Next, the role of each chemical component of high-strength corrosion-resistant structural steel is described in detail:

[0032] Carbon: In the present invention, the carbon content is selected to be 0.12-0.15%. Carbon is an effective economic element for improving the strength of steel. When the carbon content is higher than 0.12%, lath martensite will be formed to ensure strength performance. Too high carbon content will reduce low temperature toughness and deteriorate welding performance and corrosion resistance. The carbon content is controlled at 0.12-0.15%. Exemplarily, the carbon content is 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt%, 0.16wt% or a range consisting of any two of the above values.

[0033] Silicon: Silicon can be deoxidized during the smelting process, but too high a content thereof will affect weldability and toughness, and its content is controlled at 0.3-0.50%. 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 a range consisting of any two of the above values.

[0034] Manganese: High manganese is beneficial to the refinement of martensite 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 a range consisting of any two of the above values.

[0035] Niobium: Niobium is a carbide-forming element that can increase the recrystallization temperature of austenite, so that austenite can be rolled at a higher rolling temperature. In addition, Nb has a precipitation strengthening effect in the continuous cooling process of controlled rolling. The strain-induced precipitation of Nb carbonitrides can pin austenite grains, refine austenite grains, and improve strength and low-temperature toughness. Too high Nb makes it difficult to control the yield strength ratio, and too low Nb has an insignificant grain refinement effect. Preferably, the niobium content is controlled at 0.05-0.06%. Exemplarily, the niobium content is 0.05wt%, 0.052wt%, 0.054wt%, 0.056wt%, 0.058wt%, 0.06wt%, or a range consisting of any two of the above values.

[0036] Titanium: During the continuous casting solidification process, titanium combines with nitrogen to form TiN, reducing the effect of nitrogen on boron. The presence of TiN can inhibit the coarsening of grains in the heat affected zone of welding. Ti is a strong carbon element in steel. When combined with carbon in steel, it forms a large number of TiC second phase particles, which can produce second phase strengthening. On the other hand, it can inhibit the combination of Fe and C and reduce the brittle phase Fe 3 C precipitation; inhibit the combination of Cr and C, reduce Cr 23 C 6 Precipitation, retaining more effective Cr in the matrix, inhibiting the occurrence of intergranular corrosion; Ti can play a cathodic protection role in steel, which is beneficial to the growth and densification of the rust layer. Preferably, the comprehensive consideration is: 0.12-0.15%. For example, the titanium content is 0.12wt%, 0.13wt%, 0.14wt%, 0.15wt% or a range consisting of any two of the above values.

[0037] Aluminum: Aluminum and a small amount of boron are beneficial to the formation of acicular ferrite, but too much aluminum will damage the toughness of steel, and its content is controlled to be 0.015-0.035%. Exemplarily, 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 a range consisting of any two of the above values.

[0038] Chromium: Chromium content greater than 0.2% can improve corrosion resistance, while enhancing the hardenability of steel, promoting the formation of needle-plate martensite, and improving strength performance. Excessive Cr content can easily increase welding difficulty. Less than 0.35% cannot effectively play its role. The chromium content is controlled at 0.75-1.0% to ensure the combination of corrosion resistance and toughness. Exemplarily, the chromium content is 0.75wt%, 0.80wt%, 0.85wt%, 0.90wt%, 0.95wt%, 1.0wt% or a range consisting of any two of the above values.

[0039] Copper: Adding an appropriate amount of Cu can increase the corrosion resistance of the steel matrix to sulfides and dilute acid in coal mine media, improve the hardenability of steel, and significantly improve the core strength of the steel plate and the uniformity of the structure in the thickness direction. The synergistic effect of Cu and Sb can enhance the ability to resist dilute acid corrosion. The preferred copper addition amount is 0.25-0.50%. For example, the copper content is 0.25wt%, 0.30wt%, 0.35wt%, 0.40wt%, 0.45wt%, 0.50wt% or a range consisting of any two of the above values.

[0040] Antimony: Antimony is the most significant chemical element that improves the corrosion resistance of steel in a sulfuric acid environment. Sb significantly improves the corrosion resistance of steel. However, Sb is an element that has an adverse effect on the strength, toughness, plasticity and weldability of steel. Sb added to the metal surface can form Sb in the corrosive medium. 2 O 5 , the stability is higher than that of the steel matrix, which is beneficial to prevent the metal matrix from being further corroded by the corrosive medium. In the present invention, the antimony content is controlled at 0.10-0.20%, and it couples with Cu and Mo, has good corrosion resistance, and does not damage 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 a range consisting of any two of the above values.

[0041] Nickel: 0.8-0.10% can enhance the hardenability of the steel matrix, reduce the cracking caused by copper embrittlement of copper-containing steel, and significantly improve the low-temperature toughness of the welding heat-affected zone of the parent material; on the other hand, Ni can improve the corrosion resistance of the steel rust layer. Ni is an element that expands the austenite zone in steel, which can promote the reverse transformation of austenite during tempering, forming a small amount of film-like austenite, and ensuring the toughness and crack arrest of the steel. Exemplarily, the nickel content is 0.80wt%, 0.85wt%, 0.90wt%, 0.95wt%, 1.0wt% or a range consisting of any two of the above values.

[0042] Molybdenum: Molybdenum can improve the thermal stability of microalloy carbonitrides, reduce the thermal deformation of steel plates during flame cutting and welding, ensure the accuracy of components, and reduce the unevenness of the structure during hot working and welding. In addition, the addition of Mo can synergistically increase the chloride ion corrosion resistance with Cr, Ni, and Cu. Comprehensive consideration: The preferred Mo addition amount is controlled at 0.10-0.20%. Exemplarily, the molybdenum content is 0.10wt%, 0.12wt%, 0.14wt%, 0.16wt%, 0.18wt%, 0.20wt% or a range consisting of any two of the above values.

[0043] Sulfur: Sulfur easily forms MnS inclusions in steel, which are harmful to impact toughness, corrosion resistance and welding performance, so its content is within the range of ≤0.015%. For example, the sulfur content is 0.001wt%, 0.002wt%, 0.003wt%, 0.004wt%, 0.005wt% or a range consisting of any two of the above values.

[0044] Phosphorus: Too much phosphorus will cause grain boundary segregation and increase the brittleness of steel. A small amount of phosphorus can increase the weather resistance of steel. The phosphorus content is 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 a range consisting of any 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, the present application adjusts the elemental components and their contents in the high-strength corrosion-resistant structural steel, and the chemical components work together to produce high-strength corrosion-resistant structural steel with excellent performance. The high-strength corrosion-resistant structural steel provided by the present application can withstand the acidic media containing sulfur, chlorine, etc. and the high salt, high humidity and heat environment under coal mine working conditions.

[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 -40°C impact energy of the high strength corrosion resistant structural steel is greater than 27J.

[0050] In some embodiments, the metallographic structure of the high-strength corrosion-resistant structural steel is tempered martensite and austenite, wherein the basic structure is tempered martensite and a small amount of reversed film-like austenite.

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

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

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

[0054] Hot rolling is based on metal deformation, phase transformation and other processes. Under the specified deformation and temperature conditions, solid solution strengthening, precipitation strengthening, dislocation strengthening, fine grain strengthening and other hardening measures are completed to obtain steel plates with excellent comprehensive performance. Reduce the use of precious alloys, reduce manufacturing costs, make full use of the rolling and heat treatment control capabilities of the continuous rolling unit, adopt controlled rolling and accelerated cooling to produce, and obtain grains of appropriate size through deformation recrystallization in the high-temperature austenite zone, deformation in the low-temperature austenite non-recrystallization zone, and accelerated cooling after rolling.

[0055] The heat treatment process of this steel adopts the quenching and tempering process. Isothermal solution is carried out at 950℃ for 30 minutes to ensure the austenitization of the structure and the dissolution of the alloy elements. Water quenching is used for cooling, and the full martensite structure is obtained by water quenching. High-temperature tempering is carried out at 580℃, and the quenched martensite matrix is ​​decomposed into reverse austenite structure. The volume fraction of reverse austenite structure is greater than 15-20%, and the grains are divided into several small spaces to achieve the purpose of toughening the matrix. A large amount of NbC and TiC phases are precipitated between the matrix to ensure high strength performance.

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

[0057] The high-strength corrosion-resistant structural steel in the embodiment of the present application has high strength, high toughness, and is easy to weld. It is also suitable for high sulfur, high chlorine, and high humidity in coal mine environments. It is an economical high-strength corrosion-resistant steel suitable for complex loads and strong corrosion conditions. The successful application of this high-strength corrosion-resistant steel can save 30% of steel consumption and increase the service life by 5 times compared with traditional low-alloy steel, which has very considerable economic and social value.

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

[0059] In a second aspect, an embodiment of the present application provides a method for preparing high-strength corrosion-resistant structural steel, which is used to produce the above-mentioned high-strength corrosion-resistant structural steel, comprising the following steps:

[0060] Continuously casting to obtain a casting billet, the casting billet consists 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 rest are Fe and impurity elements remaining in the smelting process;

[0061] The ingot is heated in a heating furnace and subjected to controlled rolling to obtain high-strength corrosion-resistant structural steel.

[0062] The present invention adjusts the element components and their contents in high-strength corrosion-resistant structural steel, and adds trace antimony elements on the basis of adding traditional chromium, nickel, molybdenum and copper to improve corrosion resistance; in particular, adding 0.12-0.15% Ti, on the one hand, precipitates a large amount of dispersed TiC to produce second phase strengthening and improve strength; on the other hand, inhibits Fe 3 The formation of C improves toughness and inhibits the formation of Cr 23 C 6 The precipitation of elements improves the intergranular corrosion resistance of the steel plate; by optimizing the ratio of each element, design and composition, high-strength corrosion-resistant structural steel with excellent performance is manufactured. It has high strength and high corrosion resistance under coal mine conditions and is suitable for coal mine conditions, acidic media containing sulfur, chlorine, and high salt, high humidity and heat environments.

[0063] In some embodiments, the continuous casting step includes KR desulfurization: the sulfur content is removed to below 0.010% before the molten iron can enter the furnace; converter smelting: after converter smelting, argon is blown through the ladle, and the terminal control temperature of the argon station is greater than 1540°C; LF refining: the station entry temperature is greater than 1525°C, the LF station exit temperature is 1585-1620°C, the refining time is 40-45 minutes, the furnace refining and composition fine-tuning to the target composition, the molten steel temperature is greater than 1540°C and transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH cycle time is 22-30min.

[0064] KR desulfurization: The molten iron can enter the furnace only when the sulfur content is reduced to below 0.010%. The composition design system in this application contains 1.8-2.0% Mn. In order to avoid the precipitation of MnS inclusions, the S content should be controlled to be less than 0.001%, while also ensuring good impact properties.

[0065] Converter smelting: After converter smelting, argon is blown through the ladle, and the terminal 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, the LF refining and composition fine-tuning to the target composition, the molten steel temperature is greater than 1540℃ and transferred to RH for vacuum treatment.

[0067] The LF furnace has refined temperature control and argon blowing device, which can accurately control the range of alloy composition. In the embodiment of the present application, the inlet temperature and outlet temperature are determined to be within the above range according to the production rhythm of the previous and next processes and the alloy system.

[0068] Exemplarily, the LF outlet temperature is 1585° C., 1590° C., 1595° C., 1600° C., 1605° C., 1610° C., 1615° C., 1620° C. or an interval range consisting of any two of the above values.

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

[0070] In order to remove H, O, N and other elements from steel, the vacuum degree must be less than 67 MPa. The vacuum degree requirements and cycle time in the embodiment of the present application can effectively remove H, O, N and other elements within the above range.

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

[0072] In order to coordinate the production rhythm of the entire process, slab specifications and steel grade characteristics, the continuous casting speed is determined to be controlled at 1.4-1.6 m / min in the embodiment of the present application, so that steel with better performance can be obtained.

[0073] Exemplarily, 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 ingot is piled and cooled to room temperature, the slab is heated in the furnace, and enters the single stand for 5 passes of rough rolling, and then rolled by the 7-pass rough rolling unit. After rolling, it enters the laminar cooling system for tissue control.

[0075] The slab heating temperature is 1240-1280℃, the required heating time is 150-250min, and the solution time is 40min.

[0076] Thermomechanical controlled rolling and controlled cooling process is as follows: the starting temperature of rough rolling is 1160-1200℃, the final rolling temperature of rough rolling is 1100-1050℃, the starting temperature of finishing rolling is 1060-1020℃, and the final rolling temperature of finishing rolling is 880-840℃.

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

[0078] After rough rolling and final rolling, laminar cooling is performed at a cooling rate of 20-30°C / s, and final cooling is performed to 650-630°C for coiling.

[0079] The inventors of the present application have verified through experiments that the final target structure can be obtained when the cooling rate is controlled at 20-30°C / s according to thermodynamic conditions and the coiling temperature is 650-630°C.

[0080] Example

[0081] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present application will be apparent to those skilled in the art. Unless otherwise stated, all ingredients, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the instruments used in the examples are commercially available.

[0082] Embodiment 1~3:

[0083] The molten iron is desulfurized by KR and then smelted in a 210-ton converter, and then argon is blown into a ladle, refined in an LF furnace, vacuum treated in RH and continuously cast into a 230mm slab. The slab is pile-cooled to 500°C, rough-rolled for 5 times, and thermomechanically controlled rolled and controlled cooled by a 7-stand 2250 continuous rolling unit. The thickness specifications of the hot-rolled coils are 6mm, 12mm and 24mm. The composition of the high-strength corrosion-resistant structural steel of 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 embodiment of high strength corrosion resistant structural steel in 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℃, the heating time in the furnace is 180-240min, the first stage is initial rolling, and the starting rolling temperature is 1100-100℃; the second stage is finishing rolling, and the starting rolling temperature is 1080-1020℃. After rolling, the steel strip is cooled by ACC controlled cooling, and the coiling temperature is 580±15℃.

[0089] The specific rolling process parameters of 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 immersion in an acidic environment of 0.01mol / L NaHSO3, PH4-5 are as follows:

[0096] serial number 1-year hanging result, mm / year Results of hanging film in 2 years, 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 the 6mm 1000MPa grade high strength corrosion resistant steel in the embodiment of the present application; Figure 2 This is the tempered metallographic structure of the 12mm 1000MPa grade high strength corrosion resistant steel in the embodiment of the present application; Figure 3 This is the tempered metallographic structure of the 24mm 1000MPa grade high-strength corrosion-resistant steel in the embodiment of the present application. It can be seen from the above tables and pictures that the embodiment of the present application optimizes the ratio of each element and the design and composition to produce a high-strength corrosion-resistant structural steel with excellent performance, which is suitable for acidic media containing sulfur, chlorine, etc. and high-salt, high-humidity and high-heat environments under coal mine conditions.

[0098] The above embodiments are only used to illustrate the ideas and features of the present invention, and their purpose is to enable people who understand this technology to understand the content of the present invention and implement it accordingly, and are not limited to the protection scope of the present invention. Any equivalent changes or modifications made based on the technical elements of the present invention should be within the protection scope of the present invention.

Claims

1. A high-strength corrosion-resistant structural steel, characterized in that: The following components are calculated by 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 rest are Fe and residual impurity elements in the smelting process.

2. The high-strength corrosion-resistant structural steel according to claim 1, characterized in that: The high-strength corrosion-resistant structural steel meets at least one of the following conditions: (1) The yield strength of the high-strength corrosion-resistant structural steel is greater than 1000 MPa; (2) The tensile strength of the high-strength corrosion-resistant structural steel is greater than 1100 MPa; (3) The -40°C impact energy of the high-strength corrosion-resistant structural steel is greater than 27J.

3. The high-strength corrosion-resistant structural steel according to claim 1, characterized in that: The metallographic structure of the high-strength corrosion-resistant structural steel is tempered martensite and austenite.

4. A method for preparing high-strength corrosion-resistant structural steel, characterized in that: The steps include: Continuously casting to obtain a cast billet, the cast billet consists of the following components by 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 rest are Fe and residual impurity elements in the smelting process; The ingot is heated in a heating furnace and subjected to controlled rolling to obtain high-strength corrosion-resistant structural steel.

5. The preparation method according to claim 4, characterized in that: The continuous casting step includes KR desulfurization: the sulfur content is removed to below 0.010% before the molten iron can enter the furnace; converter smelting: after converter smelting, argon is blown through the ladle, and the terminal temperature of the argon station is controlled to be greater than 1540℃; LF refining: the station entry temperature is greater than 1525℃, the LF station exit temperature is 1585-1620℃, the refining time is 40-45 minutes, the furnace refining and composition fine-tuning to the target composition, the molten steel temperature is greater than 1540℃ and is transferred to RH for vacuum treatment; RH vacuum treatment: the vacuum degree requirement is ≤67MPa, and the RH cycle time is 22-30min.

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

7. The preparation method according to claim 4, characterized in that: The heating temperature of the casting is 1240-1280° C., the heating time is 150-250 min, and the solution time is 40 min.

8. The preparation method according to claim 4, characterized in that: The ingot is piled and cooled to room temperature, the slab is heated in a furnace, and enters a single stand for 5 passes of rough rolling, and then rolled by a rough rolling unit for 7 passes. After rolling, it enters a laminar cooling system for tissue control.

9. The preparation method according to claim 4, characterized in that: The ingot is subjected to laminar cooling after rough rolling and final rolling, with a cooling rate of 20-30° C. / s, and finally cooled to 650-630° C. for coiling.

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