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

Abstract

The invention discloses a high-strength and 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, 1.40 to 1.50 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, 0.12 to 0.20 percent of Ni, 0.20 to 0.30 percent of Cu, 0.050 to 0.060 percent of Nb, 0.075 to 0.095 percent of Ti, 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 high-strength and high-toughness hot-rolled weather-resistant steel plate, the-40 DEG C impact value KV2 of the full size is larger than or equal to 31J, the-40 DEG C impact value KV2 of the three-quarter size is larger than or equal to 47J, and the problem that an existing high-strength weather-resistant steel plate is low in low-temperature impact toughness can be effectively solved.

Description

Technical Field

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

[0002] Weathering steel is a type of low alloy steel with good corrosion resistance in the atmosphere. Through a large number of studies at home and abroad, it is now 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 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 the coarsening of the product's organization and second-phase particles, and increased organization inhomogeneity, making it difficult to ensure the high strength and high 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 an 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. The thickness of the product is 1.6 to 6.0 mm, which is not suitable for the production of products with a thickness of more than 6.0 mm; a high content of Ti element (0.100 to 0.140%) is added to the steel, which easily forms coarse TiN particles, resulting in a significant decrease in low-temperature impact toughness; after coiling, offline cooling combining wind cooling and air cooling is required to obtain a martensitic structure. The preparation method is complicated and the production is difficult, and the martensitic structure easily leads to a decrease in low-temperature impact toughness. Summary of the invention

[0004] The technical problem to be solved by the present invention is the low low-temperature impact toughness of the existing high-strength weathering steel plates.

[0005] The technical solution adopted by the present invention to solve its technical problem is:

[0006] In the first aspect, the present invention provides a method for preparing a high-strength and high-toughness hot-rolled weathering steel plate, wherein the components of the high-strength and high-toughness hot-rolled weathering steel plate are smelted into a slab, and the slab is then sequentially heated, rough rolled, finish rolled, laminar cooled and coiled to obtain a high-strength and high-toughness hot-rolled weathering steel plate.

[0007] In the above preparation method, the chemical composition of the high-strength and high-toughness hot-rolled weathering steel plate includes the following components by weight percentage: C 0.05-0.07%, Si 0.20-0.30%, Mn 1.40-1.50%, P≤0.020%, S≤0.007%, Cr 0.40-0.50%, Ni 0.12-0.20%, Cu 0.20-0.30%, Nb 0.050-0.060%, Ti0.075-0.095%, Als 0.010-0.045%, N≤0.0050%, and the balance is Fe and unavoidable impurities.

[0008] Furthermore, the chemical composition of the high-strength and high-toughness hot-rolled weathering steel plate includes the following components by weight percentage: C 0.06-0.07%, Si 0.27-0.29%, Mn 1.44-1.48%, P≤0.013%, S≤0.004%, Cr0.44-0.45%, Ni0.14-0.16%, Cu 0.22-0.24%, Nb 0.054-0.058%, Ti 0.085-0.090%, Als 0.027-0.031%, N≤0.0042%, and the balance is Fe and unavoidable impurities.

[0009] In the above preparation method, in the heating step, the heating temperature is 1240-1260° C. and the heating time is 150-250 min.

[0010] In the above preparation method, in the rough rolling step, 5 rough rolling passes are performed, the deformation amount of each pass is ≥18%, and the thickness of the intermediate billet is 41-43 mm; after the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used.

[0011] In the above preparation method, in the finishing rolling step, 7 finishing rolling passes are performed, and the final rolling temperature is 860-900°C.

[0012] In the above preparation method, 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.

[0013] In the above preparation method, in the coiling step, the coiling temperature is 580-620°C.

[0014] In a second aspect, the present invention provides a high-strength and high-toughness hot-rolled weathering steel plate produced by the above-mentioned preparation method.

[0015] The yield strength of the 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.

[0016] The full-size -40°C impact value KV2≥31J of the above-mentioned high-strength and high-toughness hot-rolled weathering steel plate is, and the three-quarter-size -40°C impact value KV2≥47J.

[0017] The corrosion rate of the high-strength and high-toughness hot-rolled weathering steel plate relative to Q355B is ≤65%.

[0018] The thickness of the high-strength and high-toughness hot-rolled weathering steel plate is 3.0 to 8.0 mm.

[0019] The beneficial effects of the present invention are as follows: the present invention solves the contradiction between high strength and high toughness through reasonable alloy composition design and supporting key process design of heating, rough rolling, finish rolling, laminar cooling and coiling for the whole process production, and the product realizes the industrialized production of high-strength and high-toughness hot-rolled weathering steel plates. The product production method is simple, the thickness is 3.0-8.0 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 half-size -40°C impact value KV2≥31J, the three-quarters-size -40°C impact value KV2≥47J, 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 high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1;

[0021] Figure 2 This is the metallographic structure diagram of the 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 high-strength and high-toughness hot-rolled weathering steel plate prepared in Example 1;

[0023] Figure 4 The metallographic structure diagram of the 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 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 and titanium 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, it is easy to form a martensitic structure 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 1.40-1.50%.

[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 0.12-0.20%.

[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] Titanium and nitrogen: Titanium combined with carbon and nitrogen can form tiny carbonitrides to pin grain boundaries, delay recrystallization, inhibit the growth of austenite grains, and produce fine grain strengthening and precipitation strengthening effects; increasing the titanium content can increase the volume fraction of its carbonitrides and enhance the fine grain strengthening and precipitation strengthening effects; increasing the nitrogen content in the steel is conducive to promoting the precipitation of the second phase of titanium; but too high a titanium or nitrogen content is likely to form large-sized TiN, resulting in reduced bending performance, impact performance, and forming performance, and too high a 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, the value range of Ti in the present invention is set to 0.075-0.95%, and the value range of N is set to ≤0.0050%.

[0037] 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%.

[0038] The present invention also discloses a method for preparing the above-mentioned high-strength and high-toughness hot-rolled weathering steel plate. The high-strength and high-toughness hot-rolled weathering steel plate is smelted into a slab according to the composition of the high-strength and high-toughness hot-rolled weathering steel plate described in the above content, and then the slab is heated, rough rolled, finish rolled, laminar cooled and coiled in sequence to obtain the high-strength and high-toughness hot-rolled weathering steel plate.

[0039] Further specifically, 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 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 heating temperature is set to 1240-1260°C and the heating time is set to 150-250min in the heating step.

[0040] 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, each pass deformation ≥ 18%, and the intermediate billet thickness is 41 to 43 mm. In addition, in order to suppress the coarsening of austenite grains of the intermediate billet after rough rolling, and to 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.

[0041] In the finishing step, if the final rolling temperature is too low, there is a risk that the last few stands of finishing rolling will be rolled in the two-phase region, resulting in poor overall product performance; if the final rolling temperature is too high, the deformation of the non-recrystallized region rolled in the last few stands of finishing rolling is insufficient, which is not conducive to the final microstructure refinement. Therefore, the present invention sets the finishing step to be 7 passes of finishing rolling, with a final rolling temperature of 860-900°C.

[0042] To be more specific, in the laminar cooling step, the front-stage cooling mode can achieve a greater degree of supercooling to refine the final structure, and a higher cooling rate can improve the core banded structure to a certain extent, while increasing the precipitation driving force of the Ti element, thereby precipitating fine and dispersed second-phase particles to enhance the precipitation strengthening effect; in the front-stage cooling mode, through a large number of industrial test comparisons and verifications, the mode of "opening 2 pipes and closing 2 pipes" on the upper header and fully opening the lower header can effectively improve the actual cooling rate of the product of the present invention.

[0043] 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 Ti and C elements will be slowed down, which will hinder their precipitation and reduce the 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 580-620°C in the present invention.

[0044] The technical solution and effects of the present invention are further illustrated below through practical examples.

[0045] Example

[0046] In order to facilitate the understanding of the present invention, the present invention is further described below in conjunction with embodiments and comparative examples.

[0047] The yield strength, tensile strength and elongation of the high-strength and high-toughness hot-rolled weathering steel plate 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 the "Bending Test Method for Metallic Materials" (GB / T 232); the impact performance is tested according to the "Charpy Pendulum Impact Test Method for Metallic Materials" (GB / T 229); the corrosion resistance is tested according to Appendix B of "Special Metal Materials for Locomotives and Rolling Stocks - Atmospheric Corrosion Resistant Steel" (TB / T 1979-2023).

[0048] Example 1

[0049] According to the chemical composition shown in Table 1, the slabs are smelted into slabs by conventional methods, and the smelted slabs are further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are carried out in sequence. The specific processing technology is as follows: the heating temperature is 1250℃, and the heating time is 186min; after 5 rough rolling passes, the deformation of each pass is 21%, 26%, 30%, 32%, and 37% respectively, and the thickness of the intermediate slab is 42mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the final rolling temperature is 885℃; the front-end cooling mode is adopted, the upper header is "open 2 and close 2", the lower header is fully open, and the coiling temperature is 595℃.

[0050] The properties of the prepared high-strength and high-toughness hot-rolled weathering steel plate were tested, and the specific properties are shown in Table 2; the metallographic structure was tested, and the results are as follows Figures 1 to 5 As shown: the metallographic structure is composed of polygonal ferrite + pearlite, and the structure uniformity in the thickness direction is good.

[0051] Example 2

[0052] According to the chemical composition shown in Table 1, the slab is smelted into a slab by conventional methods. The slab obtained by smelting is further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are carried out in sequence. The specific processing technology is as follows: the heating temperature is 1248℃, and the heating time is 191min; after 5 rough rolling passes, the deformation of each pass is 18%, 26%, 30%, 32%, and 37% respectively, and the thickness of the intermediate slab is 42mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the final rolling temperature is 880℃; 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℃.

[0053] The performance of the prepared high-strength and high-toughness hot-rolled weathering steel plate was tested, and its specific properties are shown in Table 2.

[0054] Example 3

[0055] According to the chemical composition shown in Table 1, the slab is smelted into a slab by conventional methods, and the slab obtained by smelting is further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the heating temperature is 1253°C, and the heating time is 195min; after 5 rough rolling passes, the deformation of each pass is 26%, 26%, 30%, 32%, and 36% respectively, and the thickness of the intermediate slab is 42mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the final rolling temperature is 885°C; 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.

[0056] The performance of the prepared high-strength and high-toughness hot-rolled weathering steel plate was tested, and its specific properties are shown in Table 2.

[0057] Comparative Example 1

[0058] The slabs were smelted into slabs by conventional methods according to the chemical composition shown in Table 1, and the slabs obtained by smelting were further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling were carried out in sequence. The specific processing technology was as follows: the heating temperature was 1237°C, and the heating time was 188min; after 6 rough rolling passes, the deformation of each pass was 20%, 21%, 21%, 26%, 22%, and 26%, respectively, and the thickness of the intermediate slab was 53mm; after 7 finishing rolling passes, the final rolling temperature was 845°C; the front-end cooling mode was adopted, and the coiling temperature was 595°C.

[0059] The performance of the prepared high-strength and high-toughness hot-rolled weathering steel plate was tested, and its specific properties are shown in Table 2.

[0060] Comparative Example 2

[0061] The slabs were smelted into slabs by conventional methods according to the chemical composition shown in Table 1, and the slabs obtained by smelting were further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling were carried out in sequence. The specific processing technology is as follows: the heating temperature is 1245℃, and the heating time is 186min; after 5 rough rolling passes, the deformation of each pass is 21%, 28%, 33%, 24%, and 40% respectively, and the thickness of the intermediate slab is 42mm. After the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used; after 7 finishing rolling passes, the final rolling temperature is 885℃; the front-end cooling mode is adopted, and the coiling temperature is 630℃.

[0062] The performance of the prepared high-strength and high-toughness hot-rolled weathering steel plate was tested, and its specific properties are shown in Table 2.

[0063] Table 1 Chemical composition by weight

[0064]

[0065] Table 2 Performance test results

[0066]

[0067]

[0068] 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: the comparative example 1 has low strength mainly due to the difference in alloy composition, and the comparative example 2 has low -40°C impact value mainly due to the high coiling temperature and the difference in the development ratio of the upper and lower headers; the embodiments produced according to the alloy composition and key process parameters provided by the present invention achieve high strength and high toughness, good uniformity of the structure in the thickness direction, and have good comprehensive performance and application prospects.

Claims

1. A method for preparing high-strength and high-toughness hot-rolled weathering steel plate, characterized in that: The components of the high-strength and high-toughness hot-rolled weathering steel plate are smelted into a slab, and the slab is then heated, roughly rolled, finely rolled, laminarly cooled and coiled in sequence to obtain the high-strength and high-toughness hot-rolled weathering steel plate; the chemical composition of the high-strength and high-toughness hot-rolled weathering steel plate includes the following components by weight percentage: C 0.05-0.07%, Si 0.20-0.30%, Mn 1.40-1.50%, P≤0.020%, S≤0.007%, Cr 0.40-0.50%, Ni0.12-0.20%, Cu 0.20-0.30%, Nb 0.050-0.060%, Ti 0.075-0.095%, Als 0.010-0.045%, N≤0.0050%, and the balance is Fe and unavoidable impurities.

2. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, characterized in that: The chemical composition of the high-strength and high-toughness hot-rolled weathering steel plate includes the following components by weight percentage: C 0.06-0.07%, Si 0.27-0.29%, Mn 1.44-1.48%, P≤0.013%, S≤0.004%, Cr 0.44-0.45%, Ni 0.14-0.16%, Cu 0.22-0.24%, Nb0.054-0.058%, Ti 0.085-0.090%, Als 0.027-0.031%, N≤0.0042%, and the balance is Fe and unavoidable impurities.

3. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, characterized in that: In the heating step, the heating temperature is 1240-1260° C. and the heating time is 150-250 min.

4. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, 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 41-43 mm; after the rough rolling is completed, two descaling water cooling passes and ultra-fast cooling are used.

5. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, characterized in that: In the finishing rolling step, 7 finishing rolling passes are performed, and the final rolling temperature is 860-900°C.

6. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, 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.

7. The method for preparing a high-strength and high-toughness hot-rolled weathering steel plate according to claim 1, characterized in that: In the coiling step, the coiling temperature is 580-620°C.

8. High-strength and high-toughness hot-rolled weathering steel plate, characterized by: The invention is prepared by the preparation method according to any one of claims 1 to 7.

9. The high-strength and high-toughness hot-rolled weathering steel plate according to claim 8, 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, three-quarter size -40℃ impact value KV2≥47J; relative Q355B corrosion rate ≤65%.

10. The high-strength and high-toughness hot-rolled weathering steel plate according to claim 8, characterized in that: The thickness is 3.0~8.0mm.

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