Thick-specification high-strength high-toughness hot-rolled weather-resistant steel plate and preparation method thereof

Abstract

The invention discloses a thick-specification high-strength high-toughness hot-rolled weather-resistant steel plate and a preparation method thereof, and belongs to the technical field of hot continuous rolling plate strip production. The steel plate comprises the following chemical components: 0.05 to 0.07 percent of C, 0.20 to 0.30 percent of Si, 1.85 to 1.95 percent of Mn, less than or equal to 0.020 percent of P, less than or equal to 0.007 percent of S, 0.40 to 0.50 percent of Cr, 0.20 to 0.25 percent of Ni, 0.20 to 0.30 percent of Cu, 0.050 to 0.060 percent of Nb, 0.04 to 0.06 percent of V, 0.075 to 0.095 percent of Ti, 0.25 to 0.30 percent of Mo, 0.010 to 0.045 percent of Als, less than or equal to 0.0050 percent of N and the balance of Fe and impurities. According to the method disclosed by the invention, the industrial production of the hot-rolled weather-resistant steel plate with thick specification, high strength and high toughness can be realized through alloy component design and matched key production process design.

Description

Technical Field

[0001] The invention belongs to the technical field of hot continuous rolling plate and strip production, and specifically relates to a thick specification high-strength and high-toughness hot-rolled weathering steel plate and a preparation method thereof. Background Art

[0002] The damage of steel corrosion to various fields of national economy and national defense construction is a common and serious problem. According to statistics, in some industrially developed countries, the economic losses caused by corrosion account for 2% to 4% of the gross national economic output value, among which atmospheric corrosion is the main form of corrosion of steel structures, accounting for about half of all corrosion losses. Therefore, the research and development of weathering steel is of great significance. Weathering steel is a kind of low-alloy steel with good corrosion resistance in the atmosphere. Through a lot of research at home and abroad, it is generally believed that after long-term exposure to the atmosphere, a layer of dense and well-adhesive oxidation products will be generated on the surface of weathering steel to isolate the steel matrix from external corrosive substances, thereby significantly improving the corrosion resistance of weathering steel. With the development of the national economy, the performance requirements of weathering steel in industries such as railway vehicles, bridges, and building structures are constantly upgrading. Not only are the materials required to have high strength to improve bearing capacity, but they are also required to have good low-temperature impact toughness to ensure structural safety. As the thickness of the steel plate increases, the rolling compression ratio during hot rolling decreases, and problems such as uneven heating of the slab and uneven cooling rate in the thickness direction are prone to occur, resulting in coarsening of the product's organization and second-phase particles, and increased organizational inhomogeneity, making it difficult to ensure the high strength and toughness of the material.

[0003] CN113265596A discloses a 700MPa grade high-strength weathering steel plate resistant to atmospheric corrosion and a production method thereof, CN113278879A discloses a 800MPa thin-gauge high-strength weathering steel plate resistant to atmospheric corrosion and a production method thereof, and CN114350911A discloses a method for preparing a hot-rolled 700MPa grade complex phase high-strength weathering steel, but the product thickness is ≤6.0mm, which is not suitable for the production of thick-gauge high-strength and high-toughness weathering steel.

[0004] CN112593158A discloses a 690MPa low-temperature resistant ultra-high strength weathering steel plate and a preparation method, which is composed of the following components in weight percentage: C: 0.12-0.14%, Si: 0.20-0.30%, Mn: 1.05-1.25%, P: ≤0.018%, S: ≤0.015%, Cu: 0.20-0.35%, Cr: 0.40-0.50%, Ni: 0.20-0.40%, Nb: 0.020-0.035%, Ti: 0.015-0.025%, Mo: 0.20-0.25%, Sb: 0.03-0.05%, Als: 0.015-0.035%, N: ≤0.00060%, O: ≤0.00015%, H: ≤0.0015%, and the rest are Fe and unavoidable impurities. The preparation method comprises the following steps: heating the slab and then sequentially performing rough rolling, finish rolling, laminar cooling, coiling, quenching and tempering. This invention requires obtaining tempered martensite and austenite structures through a heat treatment process of quenching and tempering after coiling to ensure performance. The preparation method is complex and the production is difficult. The maximum thickness of the product is only 12 mm and the tensile strength is low. Summary of the invention

[0005] The technical problem to be solved by the present invention is that the existing high-strength weathering steel plates are not suitable for the production of thick-gauge high-strength and high-toughness weathering steels, and the steel plate materials that meet the thick gauges are difficult to ensure high strength and high toughness properties.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] In a first aspect, the present invention provides a thick specification high-strength and high-toughness hot-rolled weathering steel plate, which includes the following components by weight percentage: C 0.05-0.07%, Si 0.20-0.30%, Mn 1.85-1.95%, P≤0.020%, S≤0.007%, Cr 0.40-0.50%, Ni 0.20-0.25%, Cu 0.20-0.30%, Nb 0.050-0.060%, V0.04-0.06%, Ti 0.075-0.095%, Mo0.25-0.30%, Als 0.010-0.045%, N≤0.0050%, and the balance is Fe and unavoidable impurities.

[0008] Furthermore, the above-mentioned thick-gauge high-strength and high-toughness hot-rolled weathering steel plate includes the following components by weight percentage: C0.06%, Si 0.26-0.29%, Mn 1.90-1.92%, P≤0.016%, S≤0.004%, Cr 0.45-0.46%, Ni 0.21-0.23%, Cu 0.22-0.23%, Nb 0.057-0.058%, V 0.05%, Ti 0.079-0.089%, Mo 0.27%, Als 0.021-0.028%, N≤0.0045%, and the balance is Fe and unavoidable impurities.

[0009] The yield strength of the above-mentioned thick specification high-strength and high-toughness hot-rolled weathering steel plate is ≥690MPa, the tensile strength is ≥800MPa, the elongation after fracture is ≥14%, and the 180° bending test D=2a.

[0010] The full-size -40℃ impact value KV2≥31J of the above-mentioned thick-specification high-strength and high-toughness hot-rolled weathering steel plate.

[0011] The corrosion rate of the above-mentioned thick-gauge high-strength and high-toughness hot-rolled weathering steel plate relative to Q355B is ≤55%.

[0012] The thickness of the above-mentioned thick specification high-strength and high-toughness hot-rolled weathering steel plate is 10.0 to 16.0 mm.

[0013] In the second aspect, the present invention provides a method for preparing the above-mentioned thick-gauge high-strength and high-toughness hot-rolled weathering steel plate: the components of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate are smelted into slabs, and then the slabs are heated, rough rolled, finish rolled, laminar cooled and coiled in sequence to obtain thick-gauge high-strength and high-toughness hot-rolled weathering steel plates.

[0014] In the heating step of the above preparation method, the ingot is heated by hot delivery and hot loading, the heating temperature is 1240-1260°C, and the heating time is 150-250min.

[0015] In the rough rolling step of the above preparation method, after 5 rough rolling passes, the deformation amount of each pass is ≥18%, and the thickness of the intermediate billet is 51-53 mm; after the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used.

[0016] In the finishing rolling step of the above preparation method, 7 finishing rolling passes are performed, the starting rolling temperature of the finishing rolling is ≤960°C, and the final rolling temperature is 840-880°C; the cooling water between the racks is fully turned on, and the F3 rack is polished.

[0017] In the laminar cooling step of the above preparation method, the front section cooling mode is adopted, and the upper header of the laminar cooling section is "2 open and 2 closed" and the lower header is fully open.

[0018] In the coiling step of the above preparation method, the coiling temperature is 550-590°C.

[0019] The beneficial effects of the present invention are as follows: the present invention makes up for the strength and toughness loss caused by thick specifications and solves the contradiction between high strength and high toughness through reasonable alloy composition design and supporting key process design of heating, rough rolling, finishing rolling, laminar cooling and coiling for the whole process production, thereby realizing the industrial production of thick-specification, high-strength and high-toughness hot-rolled weathering steel plates, the product thickness is 10.0-16.0 mm, the yield strength is ≥690 MPa, the tensile strength is ≥800 MPa, the elongation after fracture is ≥14%, the 180° bending test D=2a, the full-size -40°C impact value KV2≥31J, and the product can be applied to railway vehicles, bridges, building structures and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The metallographic structure diagram of the surface of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1;

[0021] Figure 2 The metallographic structure diagram of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1 at 1 / 4 of the thickness;

[0022] Figure 3 This is the metallographic structure diagram of the core of the thick high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1;

[0023] Figure 4 The metallographic structure diagram of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1 at 3 / 4 of the thickness;

[0024] Figure 5 This is the metallographic structure diagram of the lower surface of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention can be specifically implemented in the following manner.

[0026] Functions and mechanisms of each element and main process in the present invention:

[0027] Carbon: Carbon is an effective strengthening element in steel. It can be dissolved into the matrix to play a role in solid solution strengthening, and can combine with niobium, vanadium, titanium, and molybdenum to form carbide precipitation particles, which play a role in fine grain strengthening and precipitation strengthening. Therefore, increasing the carbon content is beneficial to improving strength. However, too high a carbon content will increase the carbon equivalent of the steel and reduce weldability; at the same time, it is easy to form a segregation band in the center of the steel plate, and when the cooling rate is high, a martensitic structure is easily formed at the segregation band, resulting in reduced bending performance, impact performance, and forming performance. Therefore, the value range of C in the present invention is set to 0.05-0.07%.

[0028] Silicon: Silicon can be dissolved in ferrite and austenite to increase the hardness and strength of steel, which is beneficial to refine the rust layer structure and reduce the overall corrosion rate of steel. However, too high a content will reduce the plasticity and toughness of the steel and make it difficult to remove scale during rolling. Therefore, the value range of Si in the present invention is set to 0.20-0.30%.

[0029] Manganese: Manganese has a strong solid solution strengthening effect, can significantly reduce the phase transition temperature of steel, refine the microstructure of steel, and is an important strengthening element. However, when the Mn content is too high, the continuous casting process is prone to cracks in the ingot, and it may cause the core component segregation of the steel plate, resulting in reduced bending performance, impact performance, and forming performance. Therefore, the value range of Mn in the present invention is set to 1.85-1.95%.

[0030] Phosphorus: Although phosphorus can effectively improve the atmospheric corrosion resistance of steel and has low cost, excessive phosphorus content will significantly reduce the plasticity and low-temperature toughness of steel. Therefore, the value range of P in the present invention is set to P≤0.020%.

[0031] Sulfur: Sulfur will have an adverse effect on the structure and properties of steel plates. Too high a sulfur content will increase the hot brittleness tendency of steel. At the same time, sulfur will form sulfide inclusions that deteriorate the properties of steel. Therefore, the value range of S in the present invention is set to S≤0.007%.

[0032] Chromium: Chromium has a significant effect on improving the passivation ability of steel, and can promote the formation of a dense passivation film or protective rust layer on the steel surface. Its enrichment in the rust layer can effectively improve the selective permeability of the rust layer to corrosive media; in addition, chromium can significantly improve the hardenability of steel, which is beneficial to improving the cooling rate and structural uniformity in the thickness direction of thick-gauge steel; however, too high a chromium content will increase production costs, and at a higher cooling rate, it is easy to cause the formation of martensitic structure, which reduces the plasticity and toughness of the steel. Therefore, the value range of Cr in the present invention is set to 0.40-0.50%.

[0033] Nickel: Adding nickel to steel will significantly improve the corrosion resistance of the steel. At the same time, nickel and copper elements form a copper-rich phase containing Ni, and are retained in the outer oxide layer in a solid state, reducing the copper enrichment in the matrix and the chance of forming a liquid copper-rich phase, thereby avoiding the occurrence of hot brittle defects. Therefore, Ni / Cu in steel is generally controlled to be ≥1 / 2; but too high nickel will increase the adhesion of the oxide scale, and pressing it into the steel will form hot rolling defects on the surface. Nickel is a precious metal, and too high a content of it will significantly increase the alloy cost of the steel; therefore, the value range of Ni in the present invention is set to 0.20-0.25%.

[0034] Copper: Copper added to steel is conducive to forming a dense, well-adhesive amorphous oxide (hydrocarbon oxide) protective layer on the surface of the steel, which has a significant corrosion resistance effect; in addition, copper and sulfur form insoluble sulfides, thereby offsetting the harmful effects of S on the corrosion resistance of steel; however, when the copper content is too high, due to the low melting point of copper, which is lower than the heating temperature of the steel billet, the precipitated copper is in liquid and aggregates at the austenite grain boundary. When the precipitated copper content reaches a certain level, it is easy to produce cracks during heating or hot rolling, that is, "copper brittleness" defects; in addition, according to the calculation formula of the atmospheric corrosion resistance index I, too little or too much copper content will reduce the calculated value of I. Therefore, the value range of Cu in the present invention is set to 0.20-0.30%.

[0035] Niobium: Niobium can pin austenite grain boundaries to prevent grain growth, ultimately refining the grains, which is beneficial to improving strength, plasticity, and toughness; but niobium is a precious metal, and excessive content thereof will significantly increase production costs; therefore, the value range of Nb in the present invention is set to 0.050-0.060%.

[0036] Vanadium, titanium, and nitrogen: The solid solution of vanadium in austenite can inhibit static and dynamic recrystallization during hot deformation, thereby expanding the unrecrystallized zone of austenite, increasing the strain in the unrecrystallized zone during finishing rolling, promoting the transformation of austenite to ferrite, and refining the ferrite grains; vanadium, titanium, carbon, and nitrogen can form tiny carbonitrides to pin the grain boundaries, delay recrystallization, inhibit the growth of austenite grains, and produce fine grain strengthening and precipitation strengthening effects; increasing the content of vanadium and titanium elements can increase the volume fraction of their carbonitrides, enhance fine grain strengthening and precipitation strengthening. Increasing the nitrogen content in the steel is beneficial to promoting the second phase precipitation of vanadium and titanium; however, if the titanium or nitrogen content is too high, it is easy to form large-sized TiN, resulting in reduced bending performance, impact performance, and forming performance, and too high nitrogen content will increase the aging tendency and cold brittleness and hot brittleness of the steel, and damage the welding performance and cold bending performance of the steel; therefore, in the present invention, the value range of V is set to 0.04-0.06%, the value range of Ti is set to 0.075-0.95%, and the value range of N is set to ≤0.0050%.

[0037] Molybdenum: Mo added to steel is beneficial to promote the precipitation of niobium, vanadium and titanium carbides, while effectively avoiding the coarsening of carbide particles, thereby improving the precipitation strengthening effect; however, molybdenum is a precious metal, and excessive content thereof will significantly increase production costs; therefore, the value range of Mo in the present invention is set to 0.25-0.30%.

[0038] Aluminum: Aluminum is added to steel to deoxidize and improve the quality of steel. However, if the aluminum content is too high, its nitrogen oxides are easily precipitated at the austenite grain boundaries, causing cracks in the casting. Therefore, the value range of Als in the present invention is set to 0.010-0.045%.

[0039] The present invention also discloses a method for preparing the above-mentioned thick-gauge high-strength and high-toughness hot-rolled weathering steel plate. The composition of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate described in the above content is smelted into a slab, and the slab is then heated, rough rolled, finish rolled, laminar cooled and coiled in sequence to obtain a thick-gauge high-strength and high-toughness hot-rolled weathering steel plate.

[0040] In the heating step, the slab is heated in a regenerative heating furnace. The purpose of heating the slab is to homogenize the as-cast structure and component segregation, and to dissolve the alloy elements. The thick-gauge high-strength and high-toughness hot-rolled weathering steel plate of the present invention has many types of alloy elements and high content, and the precipitate solution temperature of Ti is high, so the heating process requires sufficient temperature and time; but too high a heating temperature and too long a heating time will lead to coarse austenite grains, as well as problems such as burning, overheating, and overburning. Therefore, in the present invention, the casting is required to be hot-sent and hot-loaded in the heating step, and the heating temperature is set to 1240-1260°C and the heating time is 150-250min.

[0041] Further specifically to the rough rolling step, the rough rolling needs to achieve sufficient deformation to ensure austenite recrystallization, refine the austenite grains, and prevent the appearance of mixed crystal structure. If the thickness of the intermediate billet is too small, the deformation of the finishing rolling may be insufficient; if the thickness of the intermediate billet is too large, the deformation of the rough rolling may be insufficient, and at the same time, it will promote the strain-induced phase transformation precipitation during the finishing rolling process and after the finishing rolling, resulting in the consumption of Ti elements, etc., thereby weakening the supersaturated precipitation in the coiling stage, resulting in a reduction in the final precipitation strengthening effect. Therefore, the present invention sets the rough rolling step to undergo 5 passes of rough rolling, the deformation of each pass is ≥18%, and the thickness of the intermediate billet is 51-53mm. In addition, in order to improve the rolling rhythm while ensuring a low finishing rolling start temperature, inhibit the coarsening of the austenite grains of the intermediate billet after rough rolling, and achieve a good dephosphorization effect to improve the surface quality of the strip, two passes of descaling water cooling and ultra-fast cooling are used after the rough rolling is completed.

[0042] To be more specific, in the finishing rolling step, the last few stands after finishing rolling are basically rolled in the austenite non-recrystallization zone, so polishing the F3 stand is beneficial to increasing the reduction of the finishing rolling stands, which can flatten and elongate the austenite grains that have been rolled in the recrystallization zone and have a certain degree of refinement, increase the grain boundary area of ​​austenite per unit volume, and at the same time, a large number of deformation bands and high-density dislocations will be generated in the grains, thereby increasing the ferrite nucleation rate and obtaining a fine structure after phase transformation; using a low finishing rolling start temperature is beneficial to improving the finishing rolling process in austenite. The deformation amount of the non-recrystallized zone is increased, thereby refining the structure; if the final rolling temperature is too low, the difference with the start rolling temperature is too large, so that the cooling rate of the finishing rolling process is too fast, and there is a risk of rolling in the two-phase region in the last few stands after finishing rolling, and the comprehensive performance of the product is poor. If the final rolling temperature is too high, the deformation amount of the non-recrystallized zone is insufficient, which is not conducive to the final structure refinement; fully opening the cooling water between the stands is beneficial to increasing the temperature drop during the finishing rolling process, and is beneficial to increasing the rolling speed while ensuring that the finishing rolling start rolling temperature and the final rolling temperature are met, and the cooling rate of the subsequent laminar cooling section is correspondingly increased. Therefore, the present invention sets the finishing rolling step to go through 7 passes of finishing rolling, the finishing rolling start rolling temperature ≤960℃, and the final rolling temperature 840~880℃; the cooling water between the stands is fully opened, and the F3 stand is polished.

[0043] To be more specific, in the laminar cooling step, the front-stage cooling mode can achieve a larger degree of supercooling to refine the final structure, and a larger cooling rate can improve the core banded structure to a certain extent, while increasing the precipitation driving force of elements such as V, Ti, and Mo, thereby precipitating fine and dispersed second-phase particles to enhance the precipitation strengthening effect; in the front-stage cooling mode, the ratio of open water in the upper and lower headers has a significant effect on the cooling rate and uniformity in the thickness direction of thick-gauge strip steel. Through a large number of industrial test comparisons and verifications, the mode of "opening 2 and closing 2" on the upper header and fully opening the lower header can effectively improve the actual cooling rate of the product of the present invention and the uniformity of the structure in the thickness direction.

[0044] In the coiling step, if the coiling temperature is too low, the cooling rate will be too high during the cooling process, resulting in the formation of martensite structure, which will reduce plasticity and toughness. At the same time, the diffusion rate of elements such as V, Ti, and Mo will be slowed down, resulting in their precipitation being blocked, resulting in a reduction in precipitation strengthening effect. If the coiling temperature is too high, the grains and second phase particles will be coarse, resulting in reduced strength, plasticity and toughness. Therefore, the coiling temperature is set to 550-590°C in the present invention.

[0045] The technical solution and effects of the present invention are further illustrated below through practical examples.

[0046] Example

[0047] In order to facilitate the understanding of the present invention, the present invention is further described below in conjunction with embodiments and comparative examples.

[0048] 1. Preparation of thick high-strength and high-toughness hot-rolled weathering steel plates

[0049] (1) The chemical composition of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plates described in Examples 1 to 3 and Comparative Examples 1 to 3 is shown in Table 1, with the remainder being Fe and unavoidable impurities.

[0050] Table 1 Chemical composition by weight

[0051]

[0052] (2) The components in Table 1 are smelted into slabs by conventional methods, and the slabs obtained by smelting are further processed, and heating, rough rolling, finish rolling, laminar cooling and coiling are performed in sequence. The specific processing technology of each embodiment and comparative example is as follows.

[0053] Example 1 The heating temperature is 1253°C and the heating time is 193min; after 5 rough rolling passes, the deformation of each pass is 18%, 23%, 26%, 28%, and 33%, respectively, and the intermediate billet thickness is 52mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the finishing rolling start temperature is 945°C, the final rolling temperature is 850°C, the cooling water between the racks is fully opened, and the F3 rack is cast; the front-end cooling mode is adopted, the upper header "opens 2 roots and closes 2 roots", the lower header is fully opened, and the coiling temperature is 560°C.

[0054] Example 2 The heating temperature is 1254°C and the heating time is 220min; after 5 rough rolling passes, the deformation of each pass is 23%, 23%, 24%, 29%, and 29% respectively, and the intermediate billet thickness is 52mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the finishing rolling start temperature is 940°C, the final rolling temperature is 855°C, the cooling water between the racks is fully opened, and the F3 rack is cast; the front-end cooling mode is adopted, the upper header "opens 2 roots and closes 2 roots", the lower header is fully opened, and the coiling temperature is 580°C.

[0055] Example 3 The heating temperature is 1249°C and the heating time is 191min; after 5 rough rolling passes, the deformation of each pass is 18%, 23%, 26%, 28% and 32% respectively, and the intermediate billet thickness is 52mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the finishing rolling start temperature is 955°C, the final rolling temperature is 865°C, the cooling water between the racks is fully opened, and the F3 rack is cast; the front-end cooling mode is adopted, the upper header "opens 2 roots and closes 2 roots", the lower header is fully opened, and the coiling temperature is 585°C.

[0056] In comparative example 1, the heating temperature is 1250°C and the heating time is 199min; after 5 rough rolling passes, the deformation amounts of each pass are 18%, 23%, 26%, 28% and 33% respectively, and the intermediate billet thickness is 52mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the finishing rolling start temperature is 950°C, the final rolling temperature is 850°C, the cooling water between the stands is fully opened, and the F3 stand is cast; the front-end cooling mode is adopted, the upper header is "open 2 and close 2", the lower header is fully opened, and the coiling temperature is 540°C.

[0057] In comparative example 2, the heating temperature is 1250°C and the heating time is 212min. After 5 rough rolling passes, the deformation amounts of each pass are 18%, 22%, 26%, 29% and 33% respectively, and the intermediate billet thickness is 51mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used. After 7 finishing rolling passes, the finishing rolling start temperature is 950°C, the final rolling temperature is 860°C, the cooling water between the stands is fully opened, and the F3 stand is cast. The front-end cooling mode is adopted, the upper header is "open 2 and close 2", the lower header is fully opened, and the coiling temperature is 600°C.

[0058] In comparative example 3, the heating temperature is 1255°C and the heating time is 201min; after 5 rough rolling passes, the deformation amounts of each pass are 21%, 21%, 22%, 27% and 26% respectively, and the intermediate billet thickness is 60mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the finishing rolling start temperature is 955°C, the final rolling temperature is 840°C, the cooling water between the stands is fully opened, and the F3 stand is cast; the front-end cooling mode is adopted, the upper and lower headers are fully opened, and the coiling temperature is 585°C.

[0059] 2. Performance Test

[0060] (1) Taking the thick high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1 as an example, its metallographic structure is detected as follows: Figures 1 to 5 As shown in the figure, the metallographic structure of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plate prepared by the method of the present invention is composed of polygonal ferrite + pearlite, and the uniformity of the structure in the thickness direction is good.

[0061] (2) The specific properties of the thick-gauge high-strength and high-toughness hot-rolled weathering steel plates obtained in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 2; wherein the yield strength, tensile strength and elongation after fracture are tested according to "Tensile test of metallic materials Part 1: Room temperature test method" (GB / T 228.1); the bending performance is tested according to "Metallic material bending test method" (GB / T 232); the impact performance is tested according to "Metallic material Charpy pendulum impact test method" (GB / T 229); the corrosion resistance is tested according to Appendix B of "Special metal materials for locomotives and rolling stock - Atmospheric corrosion resistant steel" (TB / T 1979-2023).

[0062] Table 2 Performance test results

[0063]

[0064]

[0065] In combination with the preparation methods of the embodiments and comparative examples, according to the chemical composition in Table 1 and the performance test results of the embodiments and comparative examples obtained in Table 2, it can be seen that: Comparative Example 1 is mainly due to the low strength caused by the low coiling temperature, Comparative Example 2 is mainly due to the low -40°C impact value caused by the high coiling temperature, and Comparative Example 3 is mainly due to the difference in alloy composition and laminar cooling water method. The embodiment produced according to the alloy composition and key process parameters provided by the present invention achieves thick specifications, high strength and high toughness, good uniformity of thickness direction structure, and has good comprehensive performance and application prospects.

Claims

1. Thick specification high strength and high toughness hot rolled weathering steel plate, characterized in that: The invention comprises the following components by weight percentage: C 0.05-0.07%, Si 0.20-0.30%, Mn 1.85-1.95%, P≤0.020%, S≤0.007%, Cr 0.40-0.50%, Ni 0.20-0.25%, Cu 0.20-0.30%, Nb 0.050-0.060%, V 0.04-0.06%, Ti 0.075-0.095%, Mo 0.25-0.30%, Als 0.010-0.045%, N≤0.0050%, and the balance is Fe and unavoidable impurities.

2. The thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 1 is characterized in that: C 0.06%, Si0.26~0.29%, Mn 1.90~1.92%, P≤0.016%, S≤0.004%, Cr 0.45~0.46%, Ni 0.21~0.23%, Cu0.22~0.23%, Nb 0.057~0.058%, V 0.05%, Ti 0.079~0.089%, Mo0.27%, Als 0.021~0.028%, N≤0.0045%, and the balance is Fe and unavoidable impurities.

3. The thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 1 or 2, characterized in that: Yield strength ≥690MPa, tensile strength ≥800MPa, elongation after fracture ≥14%, 180° bending test D=2a, full-size -40℃ impact value KV2≥31J, corrosion rate relative to Q355B ≤55%.

4. The thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 1 or 2, characterized in that: The thickness is 10.0~16.0mm.

5. The method for preparing a thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to any one of claims 1 to 4, characterized in that: The components of thick-gauge high-strength and high-toughness hot-rolled weathering steel plates are smelted into slabs, and the slabs are then heated, rough-rolled, finish-rolled, laminar-cooled and coiled in sequence to obtain thick-gauge high-strength and high-toughness hot-rolled weathering steel plates.

6. The method for preparing thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 5, characterized in that: In the heating step, the ingot is heated by hot delivery and hot loading, the heating temperature is 1240-1260° C., and the heating time is 150-250 min.

7. The method for preparing thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 5, characterized in that: In the rough rolling step, after 5 rough rolling passes, the deformation amount of each pass is ≥18%, and the thickness of the intermediate billet is 51-53 mm; after the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used.

8. The method for preparing thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 5, characterized in that: In the finishing rolling step, 7 passes of finishing rolling are performed, the starting rolling temperature of finishing rolling is ≤960° C., and the final rolling temperature is 840-880° C.; the cooling water between the racks is fully turned on, and the F3 rack is polished.

9. The method for preparing thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 5, characterized in that: In the laminar cooling step, the front section cooling mode is adopted, and the upper header of the laminar cooling section is "2 open and 2 closed", and the lower header is fully open.

10. The method for preparing thick-gauge high-strength and high-toughness hot-rolled weathering steel plate according to claim 5, characterized in that: In the coiling step, the coiling temperature is 550-590°C.

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