Hot-rolled weather-resistant steel plate for 420MPa-grade photovoltaic bracket and preparation method of hot-rolled weather-resistant steel plate

Abstract

The invention discloses a hot-rolled weather-resistant steel plate for a 420 MPa-grade photovoltaic support and a preparation method of the hot-rolled weather-resistant steel plate, and belongs to the technical field of steelmaking. In order to improve the corrosion resistance, the invention provides a hot-rolled weather-resistant steel plate for a 420MPa-grade photovoltaic bracket and a preparation method, the hot-rolled weather-resistant steel plate for the 420MPa-grade photovoltaic bracket comprises the following components: 0.06-0.09% of C, 0.35-0.45% of Si, 0.45-0.55% of Mn, 0.07-0.08% of P, less than or equal to 0.008% of S, 1.1-1.2% of Cr, 0.25-0.35% of Cu, 0.015-0.025% of Ti, 0.02-0.06% of Als and less than or equal to 0.005% of N; the components are smelted into a plate blank, and then heating, rough rolling, finish rolling, laminar cooling and coiling are sequentially carried out to obtain the steel plate. The components of the steel plate are optimized, meanwhile, rolling and other processes are improved, the obtained steel plate has excellent mechanical properties, the corrosion resistance is remarkably improved, and the production cost is remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of steelmaking, and specifically relates to a 420MPa-grade hot-rolled weathering steel plate for a photovoltaic support and a preparation method thereof. Background Art

[0003] Photovoltaic brackets are important supporting and protective structures for photovoltaic power generation devices. The choice of bracket materials directly affects the operational safety, breakage rate, construction investment and later maintenance costs of photovoltaic modules. Photovoltaic power stations are generally built in areas with harsh environments such as coastal beaches, deserts, Gobi and water surfaces, and may be subject to extreme weather conditions such as strong winds, hail, and heavy snow. According to the "Photovoltaic Bracket Structure Design Code" (NB / T 10115-2018), the design service life of photovoltaic brackets in photovoltaic power stations should be no less than 25 years, so very high requirements are placed on the bearing capacity and corrosion resistance of photovoltaic brackets. Photovoltaic brackets are generally made of aluminum alloys, stainless steel, hot-dip galvanized steel parts, etc., which generally have problems such as high cost, low bearing capacity, difficulty in recycling, and serious environmental pollution caused by the galvanizing process.

[0004] In order to meet the new requirements of the photovoltaic industry for low-cost, lightweight, green, and highly corrosion-resistant photovoltaic brackets, and to achieve reliable service of photovoltaic brackets in harsh environments, highly corrosion-resistant weathering steel has entered the field of vision of photovoltaic users. After long-term exposure to the atmosphere, a layer of well-protected 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. Therefore, the application of weathering steel in photovoltaic brackets can be exposed or reduced in coating according to the actual service environment, thereby reducing the coating process, construction cycle, maintenance process and environmental pollution, and extending the service life of photovoltaic brackets.

[0005] CN118166290A discloses a sandblasting-free weathering steel for photovoltaic brackets, and its preparation method and application. The precious metal element Ni (0.10-0.20%) is added to the steel, and the Mn element content is relatively high (0.50-0.80%). The corrosion resistance of the product is improved by 50% relative to ordinary carbon steel (Q345B), that is, the corrosion rate relative to Q345B is ≤50%, and the corrosion resistance is relatively poor.

[0006] CN118527481A discloses a weathering steel Q450NH for photovoltaic brackets and a preparation method thereof, wherein the precious metal element Ni (0.12-0.30%) is added to the steel; the added Ti element content is high (0.045-0.070%) and the N element content is not controlled, which easily generates large-sized TiN second phase particles and deteriorates the product forming performance; according to the embodiment, the atmospheric corrosion resistance index of the product is 6.287-6.337, and the corrosion resistance is difficult to meet the requirements for exposed use in photovoltaic brackets. Summary of the invention

[0007] The purpose of the present invention is to improve the corrosion resistance of a steel plate for a photovoltaic support, ensure its mechanical properties, and reduce production costs.

[0008] To achieve the above object, the present invention first provides a method for preparing a 420MPa hot-rolled weathering steel plate for a photovoltaic support, wherein the 420MPa hot-rolled weathering steel plate for a photovoltaic support comprises the following components by weight percentage: C 0.06-0.09%, Si 0.35-0.45%, Mn 0.45-0.55%, P 0.070-0.080%, S≤0.008%, Cr 1.10-1.20%, Cu 0.25-0.35%, Ti 0.015-0.025%, Als 0.020-0.060%, N≤0.0050%, and the balance is Fe and unavoidable impurities;

[0009] The preparation method comprises the following steps: smelting the required components into slabs, and then sequentially heating, rough rolling, finish rolling, laminar cooling and coiling the slabs to obtain the slabs.

[0010] Among them, in the preparation method of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic support, the thickness of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support is 1.5 to 6.0 mm.

[0011] Among them, in the preparation method of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic support, in the heating step, the slab is hot-delivered and hot-loaded, the heating temperature is 1240-1280°C, and the heating time is 130-230min.

[0012] Among them, in the preparation method of the above-mentioned 420MPa-grade hot-rolled weathering steel plate for photovoltaic bracket, in the rough rolling step, after 6 rough rolling passes, the deformation amount of each pass is ≥18%; when the thickness of the finished hot-rolled weathering steel plate is 1.5mm≤thickness<2.5mm, the thickness of the intermediate billet is controlled to be 30-34mm; when the thickness of the finished hot-rolled weathering steel plate is 2.5mm≤thickness<4.0mm, the thickness of the intermediate billet is controlled to be 32-36mm; when the thickness of the finished hot-rolled weathering steel plate is 4.0-6.0mm, the thickness of the intermediate billet is controlled to be 40-44mm.

[0013] Among them, in the preparation method of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic bracket, in the finishing rolling step, after 7 finishing rolling passes, the reduction rates of the last three stands are ≥15%, ≥13% and ≥10% respectively, and the final rolling temperature is 860-900℃.

[0014] Among them, in the preparation method of the above-mentioned 420MPa-grade hot-rolled weathering steel plate for photovoltaic support, a front-stage cooling mode is adopted in the laminar cooling step, and the cooling rate is ≥40°C / s.

[0015] Among them, in the preparation method of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic support, in the coiling step, the coiling temperature is 580-620°C.

[0016] The present invention also provides a 420MPa-grade hot-rolled weathering steel plate for a photovoltaic support, which is prepared by the above-mentioned preparation method.

[0017] Among them, the above-mentioned 420MPa-grade hot-rolled weathering steel plate for photovoltaic bracket has a yield strength ≥420MPa, a tensile strength ≥530MPa, an elongation after fracture ≥30%, and a 180° bending test D=a.

[0018] Among them, the atmospheric corrosion resistance index I of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic brackets is ≥7.5, the relative corrosion rate of Q355B is ≤35%, and the uniform corrosion thinning amount on both sides does not exceed 0.2mm within a 25-year service life under C1-C3 environment.

[0019] In the present invention, all steps not specifically described are performed using conventional operations in the art.

[0020] Beneficial effects of the present invention:

[0021] The present invention adds a certain amount of Si, P, Cr, Cu and other elements to make the atmospheric corrosion resistance index I≥7.5, thereby significantly improving the atmospheric corrosion resistance of the product. Compared with traditional weathering steel, the alloy cost is effectively reduced because the Ni element is not added. By giving full play to the solid solution strengthening effect of elements such as Si and P and the fine grain strengthening and precipitation strengthening effect of the Ti element, precious metal elements such as Nb are not added, and the Mn element content is reduced, so that the alloy cost is further reduced. By setting a reasonable heating temperature and heating time, the performance is guaranteed and the generation of "copper brittleness" defects is avoided. By a reasonable production process design, the stable production of thin-gauge products and the control of organizational performance are guaranteed.

[0022] The hot-rolled weathering steel plate for photovoltaic brackets prepared by the composition and preparation method of the present invention has a yield strength of ≥420MPa, a tensile strength of ≥530MPa, an elongation after fracture of ≥30%, a 180° bending test D=a, a relative Q355B corrosion rate of ≤35%, and a double-sided uniform corrosion thinning amount of no more than 0.2mm within a bare 25-year service life under the C1-C3 environment specified in "Atmospheric Corrosion of Metals and Alloys Part 1: Classification, Determination and Evaluation" (GB / T 19292.1-2018). Application to photovoltaic brackets can effectively reduce material usage, transportation costs, construction cycles, and coating and maintenance costs, thereby achieving green and lightweight applications. DETAILED DESCRIPTION

[0023] Specifically, a method for preparing a 420MPa-grade hot-rolled weathering steel plate for a photovoltaic support, the 420MPa-grade hot-rolled weathering steel plate for a photovoltaic support comprising the following components by weight percentage: C 0.06-0.09%, Si 0.35-0.45%, Mn 0.45-0.55%, P 0.070-0.080%, S≤0.008%, Cr 1.10-1.20%, Cu 0.25-0.35%, Ti0.015-0.025%, Als 0.020-0.060%, N≤0.0050%, and the balance is Fe and unavoidable impurities;

[0024] The preparation method comprises the following steps: smelting the required components into slabs, and then sequentially heating, rough rolling, finish rolling, laminar cooling and coiling the slabs to obtain the slabs.

[0025] Functions and mechanisms of each element and main process in the present invention:

[0026] Carbon: Carbon is an effective strengthening element in steel. It can be dissolved into the matrix to play a role of solid solution strengthening, and can combine with titanium to form carbide precipitation particles, which play a role of fine grain strengthening and precipitation strengthening. Therefore, increasing the carbon content is beneficial to improving strength. However, too high a carbon content is likely to form a segregation zone in the center of the steel plate, and when the cooling rate is high, a martensitic structure is likely to form at the segregation zone, resulting in reduced bending performance, impact performance, and forming performance. Therefore, the value range of C in the present invention is set to 0.06-0.09%.

[0027] Silicon: Silicon can be dissolved in ferrite and austenite to improve 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 0.35-0.45%.

[0028] 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 manganese content is too high, the continuous casting process is prone to cracks in the ingot, and may cause component segregation in the core of the steel plate, resulting in reduced bending performance, impact performance, and forming performance, while increasing production costs. Therefore, the value range of Mn in the present invention is set to 0.45-0.55%.

[0029] Phosphorus: Although phosphorus has a strong solid solution strengthening effect and can effectively improve the atmospheric corrosion resistance of steel with 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 0.070-0.080%.

[0030] 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≤0.008%.

[0031] 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; however, too high a chromium content will increase production costs, and at a high cooling rate, it is easy to cause martensite structure to be produced, which reduces the plasticity and toughness of the steel. Therefore, the value range of Cr in the present invention is set to 1.10-1.20%.

[0032] 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 0.25-0.35%.

[0033] 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, 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 0.015-0.025%, and the value range of N is set to ≤0.0050%.

[0034] 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 0.020-0.060%.

[0035] The present invention also discloses a preparation method of the above-mentioned 420MPa grade hot-rolled weathering steel plate for photovoltaic bracket. The composition of the 420MPa grade hot-rolled weathering steel plate for photovoltaic bracket described in the above content is smelted into a slab, and then the slab is heated, rough-rolled, finish-rolled, laminar-cooled and coiled in sequence to obtain the 420MPa grade hot-rolled weathering steel plate for photovoltaic bracket.

[0036] Further specific to 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 420MPa-grade hot-rolled weathering steel plate for photovoltaic brackets 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 the heating temperature is too high and the heating time is too long, which will lead to coarse austenite grains, as well as problems such as burning, overheating, and overburning; at the same time, compared with traditional weathering steel, in order to reduce the alloy cost, a certain amount of Cu is added to the 420MPa-grade hot-rolled weathering steel plate for photovoltaic brackets of the present invention without adding Ni, and a Ni-containing copper-rich phase cannot be formed to reduce the chance of liquid copper-rich phase formation, so a long heating time will lead to "copper brittle" defects. 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 1240-1280°C and the heating time is 130-230min.

[0037] In the present invention, the thickness of the finished 420MPa-grade hot-rolled weathering steel plate for photovoltaic support is 1.5 to 6.0 mm.

[0038] To be more specific, in the rough rolling step, the rough rolling needs to achieve sufficient deformation to ensure austenite recrystallization, refine 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 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; in addition, when the thickness of the finished product is small, the temperature drop of the strip during the finishing rolling process is faster, and the thickness of the intermediate billet can be appropriately reduced to avoid excessive finishing load while ensuring sufficient finishing deformation. Therefore, the present invention sets the rough rolling step to be carried out through 6 rough rolling passes, with the deformation of each pass ≥18%; when the thickness of the finished product is 1.5~<2.5mm, the thickness of the intermediate billet is 30~34mm; when the thickness of the finished product is 2.5~<4.0mm, the thickness of the intermediate billet is 32~36mm; when the thickness of the finished product is 4.0~6.0mm, the thickness of the intermediate billet is 40~44mm.

[0039] To be more specific, in the finishing step, the three stands after finishing rolling are basically rolled in the austenite non-recrystallization zone. By adopting a large deformation rate, the austenite grains that have been rolled in the recrystallization zone and refined to a certain extent can be flattened and elongated, increasing the grain boundary area of ​​austenite per unit volume. 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; if the final rolling temperature is too low, there is a risk of rolling in the two-phase zone in the last few stands after finishing rolling, especially due to the difference in temperature in the width direction of the strip, the edge temperature is often lower, and as the thickness of the strip decreases, the temperature of the finishing rolling process drops faster. When the last few stands are rolled in the last few stands, the edge temperature of the strip is easily reduced to the austenite-ferrite two-phase zone, resulting in a mixed crystal structure that makes the comprehensive performance of the product worse; if the final rolling temperature is too high, the deformation of the non-recrystallization zone rolled in the last few stands after finishing rolling is insufficient, which is not conducive to the final structure refinement. Therefore, the present invention sets the finishing rolling step to be carried out through 7 passes, the reduction rates of the last three stands are ≥15%, ≥13% and ≥10% respectively, and the final rolling temperature is 860-900°C.

[0040] To be more specific, in the laminar cooling step, the front-stage cooling mode is adopted and the cooling rate is controlled to be ≥40°C / s, which can achieve a larger degree of supercooling and thus refine the final structure. The use of a larger 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.

[0041] 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.

[0042] From the above, it can be seen that the present invention optimizes the composition of the steel plate, adds a certain amount of Si, P, Cr, Cu, Ti and other elements, does not add precious elements such as Ni and Nb, and improves the process at the same time to match the process and the composition. A 420MPa grade hot-rolled weathering steel plate for photovoltaic brackets can be obtained. The steel plate has excellent mechanical properties and corrosion resistance that is significantly better than existing steel plates, and greatly reduces production costs.

[0043] The 355MPa-grade hot-rolled weathering steel plate for photovoltaic brackets provided by the present invention has a yield strength of ≥420MPa, a tensile strength of ≥530MPa, an elongation after fracture of ≥30%, and a 180° bending test D=a.

[0044] The 355MPa-grade hot-rolled weathering steel plate for photovoltaic brackets provided by the present invention has an atmospheric corrosion resistance index I≥7.5, a relative Q355B corrosion rate≤35%, and a double-sided uniform corrosion thinning amount of no more than 0.2mm during a 25-year service life in a bare use under a C1-C3 environment.

[0045] The present invention is further described in detail below by way of examples, but the protection scope of the present invention is not limited to the scope of the examples.

[0046] In the embodiment, the atmospheric corrosion resistance index of the hot-rolled weathering steel plate for photovoltaic bracket is I=26.01(%Cu)+3.88(%Ni)+1.20(%Cr)+1.49(%Si)+17.28(%P)-7.29(%Cu)(%Ni)-9.10(%Ni)(%P)-33.39(%Cu) 2 .

[0047] In the embodiment, the yield strength, tensile strength and elongation of the hot-rolled weathering steel plate for the photovoltaic support 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 "Metallic Material Bending Test Method" (GB / T 232); 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] The chemical composition of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is shown in Table 1, and the remainder is Fe and unavoidable impurities.

[0050] The 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is smelted into slabs by conventional methods according to its composition, and the smelted slabs are further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the ingot is hot-transferred and hot-loaded, the heating temperature is 1275°C, and the heating time is 215min; after 6 rough rolling passes, the deformation amount of each pass is 19%, 25%, 26%, 28%, 30%, and 29% respectively, and the thickness of the intermediate slab is 32mm; after 7 finishing rolling passes, the reduction rates of the last three stands are 15%, 13%, and 11% respectively, and the final rolling temperature is 875-895°C; the front-stage cooling mode is adopted, the cooling rate is 55°C / s, and the coiling temperature is 590-610°C.

[0051] The specific properties of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support obtained in this embodiment are shown in Table 2.

[0052] Example 2

[0053] The chemical composition of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is shown in Table 1, and the remainder is Fe and unavoidable impurities.

[0054] The 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is smelted into slabs by conventional methods according to its composition, and the smelted slabs are further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the ingot is hot-delivered and hot-loaded, the heating temperature is 1250°C, and the heating time is 175min; after 6 rough rolling passes, the deformation amount of each pass is 18%, 25%, 26%, 27%, 29%, and 28% respectively, and the thickness of the intermediate slab is 34mm; after 7 finishing rolling passes, the reduction rates of the last three stands are 15%, 14%, and 10% respectively, and the final rolling temperature is 860-880°C; the front-stage cooling mode is adopted, the cooling rate is 50°C / s, and the coiling temperature is 580-615°C.

[0055] The specific properties of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support obtained in this embodiment are shown in Table 2.

[0056] Example 3

[0057] The chemical composition of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is shown in Table 1, and the remainder is Fe and unavoidable impurities.

[0058] The 420MPa grade hot-rolled weathering steel plate for photovoltaic support of this embodiment is smelted into slabs by conventional methods according to its composition, and the smelted slabs are further processed, and heating, rough rolling, finishing rolling, laminar cooling and coiling are performed in sequence. The specific processing technology is as follows: the ingot is hot-delivered and hot-loaded, the heating temperature is 1265°C, and the heating time is 200min; after 6 rough rolling passes, the deformation of each pass is 18%, 24%, 23%, 25%, 24%, and 23%, respectively, and the thickness of the intermediate slab is 42mm; after 7 finishing rolling passes, the reduction rates of the last three stands are 16%, 14%, and 11%, respectively, and the final rolling temperature is 870-890°C; the front-stage cooling mode is adopted, the cooling rate is 45°C / s, and the coiling temperature is 590-610°C.

[0059] The specific properties of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support obtained in this embodiment are shown in Table 2.

[0060] Comparative Example 1

[0061] This comparative example refers to Example 1 in "A sandblast-free weathering steel for photovoltaic support and its preparation method and application" (CN118166290A).

[0062] The chemical composition of the sandblasting-free weathering steel for the photovoltaic bracket of this comparative example is shown in Table 1, and the remainder is Fe and unavoidable impurities.

[0063] The TMCP process is used to prepare the weathering steel for photovoltaic brackets without sandblasting in this comparative example, including the following steps: heating the ingot → high-pressure dephosphorization → rough rolling → finishing rolling → laminar cooling → coiling for standby use; wherein: heating the ingot, controlling the heating temperature of the ingot at 1180°C; high-pressure dephosphorization, the high-pressure water pressure is 170-190kg / cm 2 The starting temperature of rough rolling is 1060℃, the ending temperature of rough rolling is 900℃, and the reduction rate is 80%; the starting temperature of finishing rolling is 870℃, the ending temperature of finishing rolling is 850℃, and the reduction rate is 85%. After 10 passes of rolling, the steel plate is formed; laminar cooling is carried out, and it is cooled to 550℃ at a cooling rate of 22℃ / s, and coiled for standby use.

[0064] The specific properties of the sandblast-free weathering steel for the photovoltaic bracket obtained in this comparative example are shown in Table 2.

[0065] Comparative Example 2

[0066] This comparative example refers to Example 1 in "A weathering steel Q450NH for photovoltaic support and its preparation method" (CN118527481A).

[0067] The chemical composition of the weathering steel Q450NH used for the photovoltaic support in this comparative example is shown in Table 1, and the remainder is Fe and unavoidable impurities.

[0068] The weathering steel Q450NH for photovoltaic brackets in this comparative example is prepared by CSP process, including the following steps: molten iron dephosphorization pretreatment followed by converter smelting, smelting followed by converter LF furnace refining, and refining followed by casting in a thin slab continuous casting machine, the pulling speed of the continuous casting machine being 4.2m / min, and the continuous casting crystallizer protective slag adopts APH3-C1A protective slag specially used for weathering steel, the protective slag contains LiO2 to improve its lubrication performance, and a continuous casting thin slab with a thickness of 52mm is obtained; the continuously cast thin slab is heated by a tunnel roller bottom heating furnace, and the steel tapping temperature is 1193°C; the slab is descaled in two passes after being discharged from the furnace, and continuous rolling is performed after the two descaling passes, and a third dephosphorization pass is performed after continuous rolling; the first descaling pressure is 18MPa, and the second descaling pressure is 24MPa, and the first and second descaling passes are performed between the heating furnace and the primary frame; the continuous rolling method is six-frame continuous rolling, and the final rolling temperature is 24MPa. 911℃; turn off the front horizontal spray of F1-F6 frames; turn off the cooling water of F1-F3 frames; intervene in the exit speed of the rolling mill and perform constant speed rolling at a speed of 9.6m / s; step 4: after rolling, the plate and strip enter the 8-section laminar cooling section to cool to the coiling temperature, the coiling temperature is 630℃, and the laminar cooling mode uses the "8" mode two-stage segmented cooling; by numbering the 8-section headers and defining the opening sequence in the laminar cooling secondary model, the first and second sections of the headers are all opened, and the seventh and eighth sections of the upper and lower cooling headers are combined with the actual detection of the coiling temperature and the target control deviation, and are intermittently opened from the outlet to the inlet in combination with the actual detection; if the target coiling temperature cannot be guaranteed after all 8 sections are opened, cooling is carried out by opening a group of headers from the seventh section to the sixth section; the laminar cooling water system is controlled according to the maximum water flow rate of the system operation, and the system pressure is 0.8bar.

[0069] The specific properties of the weathering steel Q450NH used for photovoltaic brackets obtained in this comparative example are shown in Table 2.

[0070] Table 1 Chemical composition of the embodiments and comparative examples / wt%

[0071] category C Si Mn P S Cr Example 1 0.07 0.40 0.50 0.075 0.004 1.13 Example 2 0.07 0.39 0.52 0.072 0.004 1.10 Example 3 0.07 0.40 0.51 0.076 0.004 1.15 Comparative Example 1 0.06 0.20 0.50 0.007 0.002 0.52 Comparative Example 2 0.051 0.321 0.161 0.018 0.002 0.46 category Ni Cu Ti Als N I Example 1 — 0.28 0.022 0.046 0.0049 7.9 Example 2 — 0.27 0.025 0.035 0.0045 7.7 Example 3 — 0.27 0.023 0.036 0.0046 7.9 Comparative Example 1 0.20 0.30 — — — 6.2 Comparative Example 2 0.152 0.287 0.060 0.038 — 6.297

[0072] Table 2 Performance test results of embodiments and comparative examples

[0073]

[0074]

[0075] Note: a indicates the relative corrosion rate of Q355B (Q345B); b indicates that the uniform corrosion thinning on both sides does not exceed 0.2mm in a 25-year service life under C1-C3 environment; c indicates that it is used exposed in an atmospheric environment with environmental corrosion level C1-C3 without sandblasting.

[0076] 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 adds the precious metal element Ni, but the atmospheric corrosion resistance index I is low and the corrosion rate is relatively high relative to Q355B (Q345B), so the corrosion resistance of the product is relatively poor; in addition, the elongation after fracture of the comparative example is relatively low; the embodiment produced according to the alloy composition and key process parameters provided by the present invention has a simple production method, the product has high plasticity and excellent corrosion resistance, and has good application prospects.

Claims

1. A method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support, characterized in that: The 420MPa grade hot-rolled weathering steel plate for photovoltaic support comprises the following components by weight percentage: C 0.06-0.09%, Si 0.35-0.45%, Mn 0.45-0.55%, P 0.070-0.080%, S≤0.008%, Cr 1.10-1.20%, Cu 0.25-0.35%, Ti 0.015-0.025%, Als 0.020-0.060%, N≤0.0050%, and the balance is Fe and unavoidable impurities; The preparation method comprises the following steps: smelting the required components into slabs, and then sequentially heating, rough rolling, finish rolling, laminar cooling and coiling the slabs to obtain the slabs.

2. The method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support according to claim 1, characterized in that: The thickness of the 420MPa grade hot-rolled weathering steel plate for photovoltaic support is 1.5 to 6.0 mm.

3. The method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support according to claim 1, characterized in that: In the heating step, the slab is hot transported and hot loaded, the heating temperature is 1240-1280°C, and the heating time is 130-230min.

4. The method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support according to claim 1, characterized in that: In the rough rolling step, after 6 rough rolling passes, the deformation amount of each pass is ≥18%; when the thickness of the finished hot-rolled weathering steel plate is 1.5mm≤thickness<2.5mm, the thickness of the intermediate billet is controlled to be 30-34mm; when the thickness of the finished hot-rolled weathering steel plate is 2.5mm≤thickness<4.0mm, the thickness of the intermediate billet is controlled to be 32-36mm; when the thickness of the finished hot-rolled weathering steel plate is 4.0-6.0mm, the thickness of the intermediate billet is controlled to be 40-44mm.

5. The method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support according to claim 1, characterized in that: In the finishing step, after 7 passes of finishing rolling, the reduction rates of the last three stands are ≥15%, ≥13% and ≥10% respectively, and the final rolling temperature is 860-900°C.

6. The method for preparing a 420MPa grade hot-rolled weathering steel plate for a photovoltaic support according to claim 1, characterized in that: In the laminar cooling step, the front cooling mode is adopted, and the cooling rate is ≥40°C / s.

7. The method for preparing a 420MPa grade hot-rolled weathering steel plate for photovoltaic support according to any one of claims 1 to 6, characterized in that: In the coiling step, the coiling temperature is 580 to 620°C. 8.420MPa grade hot-rolled weathering steel plate for photovoltaic bracket, characterized by: The preparation method is described in any one of claims 1 to 7.

9. The 420MPa grade hot-rolled weathering steel plate for photovoltaic support according to claim 8, characterized in that: Its yield strength is ≥420MPa, tensile strength is ≥530MPa, elongation after fracture is ≥30%, and 180° bending test D=a.

10. The 420MPa grade hot-rolled weathering steel plate for photovoltaic support according to claim 8 or 9, characterized in that: Its atmospheric corrosion resistance index I≥7.5, the relative corrosion rate of Q355B ≤35%, and the uniform corrosion thinning on both sides does not exceed 0.2mm during the 25-year service life under C1-C3 environment.

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