A low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method

Abstract

This invention discloses a low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. The chemical composition of the steel contains C: 0.064%~0.082%, Si: 0.34%~0.52%, Mn: 0.81%~1.06%, P: 0.088%~0.102%, S: ≤0.008%, Cu: 0.13%~0.21%, Sb: 0.104%~0.124%, Ti: 0.027%~0.047%, Mo: 0.18%~0.29%, Ce: 0.0139%~0.0158%, and Als: 0.048%~0.071%, wherein the P / Ce ratio is controlled at 6.3~6.5 and the Si / Mo ratio is controlled at 1.1~2.8. The manufacturing method includes smelting, slab continuous casting, billet heating, rolling, laminar flow cooling, and coiling. The steel has a Rel of 571–598 MPa, Rm of 697–714 MPa, and A > 25%; the surface hardness of the steel is 205–211 HBW, the wear rate relative to Q345B is 30.3%–31.5%, and the corrosion rate relative to Q345B is 32.78%–34.3%. The steel of this invention is low in cost and is a high-strength steel for photovoltaic brackets that combines excellent wear resistance and atmospheric corrosion resistance, solving the problems of high cost and lack of wear resistance in existing alloys.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant steel for photovoltaic brackets, and relates to a low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. Background Technology

[0002] As a crucial support device for fixing photovoltaic modules in a photovoltaic power generation system, the performance of photovoltaic (PV) brackets directly affects the lifespan of the PV power station. Because PV brackets are constantly exposed to the atmosphere, they suffer varying degrees of atmospheric corrosion, especially in windy, sandy areas like the Gobi Desert. Therefore, the key requirements for the steel used in PV brackets are resistance to atmospheric corrosion and abrasion. Currently, the main materials used to manufacture PV brackets are aluminum alloys, hot-dip galvanized steel, and weathering steel. Aluminum alloy brackets are expensive and have low load-bearing capacity, lacking a competitive advantage; hot-dip galvanized steel has a complex production process, and the galvanizing process is highly polluting; weathering steel often increases costs due to the addition of high amounts of precious metal corrosion-resistant elements. Furthermore, PV brackets made from these materials often only consider atmospheric corrosion resistance while neglecting the necessary abrasion resistance. Simultaneously, with the increasing demands for the strength of bracket steel, there is an urgent need to develop a high-strength steel for PV brackets that is simple to manufacture, energy-efficient, cost-effective, and possesses excellent abrasion and corrosion resistance.

[0003] Prior to this invention,

[0004] The invention patent with publication number CN 113528949 A, entitled "A 550MPa Grade Hot-Rolled Steel Coil for Solar Panel Mounts and Its Production Method," has the following composition: 0.03%≤C≤0.05%, Si≤0.10%, 1.20%≤Mn≤1.40%, P≤0.025%, S≤0.015%, 0.02%≤ALs≤0.06%, 0.015%≤Nb≤0.030%, 0.10%≤Cu≤0.15%, 0.40%≤Cr≤0.60%, 0.01%≤V≤0.02%, with the balance being Fe and unavoidable impurities. This invention improves the mechanical properties of the steel by adding high amounts of Nb and V, and enhances its atmospheric corrosion resistance by adding Cr and Cu. The high variety and content of precious metals in this invention increase production costs. Furthermore, the invention describes the effect of elements on atmospheric corrosion resistance, but does not study the wear resistance of steel used in photovoltaic brackets.

[0005] The invention patent with publication number CN 115896613 A, entitled "A High-Strength, Low-Cost Weathering Steel for Photovoltaic Supports and Its Preparation Method and Application," has the following composition: C ≤ 0.10%, Si: 0.02%–0.50%, Mn: 0.80%–2.00%, P ≤ 0.030%, S ≤ 0.005%, Cr: 0.20%–0.80%, Cu: 0.20%–0.60%, W: 0.05%–0.50%, Als: 0.010%–0.050%, with the balance being Fe and impurities. This invention adds the precious metal W, which inevitably increases the alloy cost. Furthermore, the invention employs a tempering process to improve the steel's mechanical properties, which not only prolongs the production cycle but also increases production costs. Moreover, this invention only describes the influence of elements on atmospheric corrosion resistance and does not study the wear resistance of the steel used in photovoltaic supports.

[0006] The invention patent CN101423916B, entitled "A Low-Alloy Wear-Resistant and Corrosion-Resistant Steel and Its Manufacturing Method," has the following composition: C: 0.10%–0.16%, Si: 1.0%–1.6%, Mn: 0.8%–1.6%, Cr: 1.0%–1.6%, Mo: 0.3%–0.4%, Ni: 0.3%–0.4%, Al: 0.6%–1.0%, rare earth + Nb: ≤0.1%, with the balance being Fe and impurities. This invention improves the wear and corrosion resistance of the steel by adding Al and Nb, elements that enhance corrosion resistance, and through rare earth modification treatment, forming a Mn-Si-Cr-Mo-Al system of carbide-free bainitic steel. However, it is suitable for use in marine sediment abrasion and corrosion environments. Furthermore, the inclusion of precious metals such as Cr, Ni, and Nb in this invention results in higher production costs.

[0007] The invention patent CN114686763B, entitled "A 550MPa Grade Wear-Resistant Corrosion Steel," has the following composition: C: 0.065%–0.086%, Si: 0.58%–0.86%, Mn: 0.90%–1.47%, P≤0.018%, S≤0.006%, Cr: 0.85%–1.39%, Cu: 0.14%–0.24%, Sb: 0.051%–0.084%, W: 0.25%–0.45%, Ti: 0.066%–0.086%, Als: 0.015%–0.045%, N≤0.004%, with the remainder being Fe and impurity elements. This invention improves the wear resistance of the material through the synergistic effect of Si, Mn, Cr, and W elements, and the formation of certain amounts of FeMnCrC, TiC, and WC. However, this invention is mainly applicable to the manufacture of steel for containers, and does not have high requirements for the plasticity and formability of the material. It is not suitable for the plasticity requirements of photovoltaic brackets during forming. Summary of the Invention

[0008] The purpose of this invention is to provide a low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. This high-strength steel for photovoltaic brackets is inexpensive and has excellent wear resistance and atmospheric corrosion resistance, solving the problems of high cost and lack of wear resistance of existing alloys.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] This invention proposes a low-cost, 550MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets. The chemical composition, by weight percentage, is: C: 0.064%–0.082%, Si: 0.34%–0.52%, Mn: 0.81%–1.06%, P: 0.088%–0.102%, S: ≤0.008%, Cu: 0.13%–0.21%, Sb: 0.104%–0.124%, Ti: 0.027%–0.047%, Mo: 0.18%–0.29%, Ce: 0.0139%–0.0158%, Als: 0.048%–0.071%, wherein the P / Ce ratio is controlled at 6.3–6.5, the Si / Mo ratio is controlled at 1.1–2.8, and the balance is Fe and unavoidable impurities.

[0011] The reason for selecting the above alloying elements and their contents in this invention is as follows:

[0012] Carbon (C): As one of the key elements ensuring the strength and hardness of materials, C in this invention mainly improves the strength of steel plates through solid solution strengthening and precipitation strengthening. Furthermore, when added synergistically with Mo, it can generate a hard phase Mo₂C₃ within the grains, improving the hardness and wear resistance of the steel. However, excessive C will deteriorate the plasticity and formability of the steel plate. Therefore, the C content in this invention is limited to 0.064%–0.082%.

[0013] Si (Si): As one of the important elements for improving corrosion resistance, strength, and hardness, Si easily accumulates on the surface of steel plates, forming a dense and tightly bonded SiO2 oxide protective film that effectively inhibits the penetration of corrosive media. When added in combination with Mo, it can form Mo2Si3 hard phase particles with free Mo in the steel. By controlling the final rolling temperature and coiling temperature, micron-sized (40-70 μm) hard phase Mo2Si3 particles can be dispersed and precipitated near grain boundaries or inside grains, effectively improving the hardness and wear resistance of the steel. However, excessive Si content not only adversely affects surface quality but also deteriorates the steel's properties due to the formation of large-sized Mo2Si3 particles. Therefore, the Si content is limited to 0.34%-0.52% in this invention. Furthermore, the Si and Mo contents determine the type of Si-Mo and the state of the precipitated particles. To obtain more dispersed precipitated phase particles, the Si / Mo ratio is controlled between 1.1 and 2.8.

[0014] Mn is one of the main strengthening elements in steel, and it can improve the strength of steel plates through solid solution strengthening. Meanwhile, in this invention, Mn, as an important austenitizing stabilizing element, can expand the austenite phase region, thereby improving the stability of residual austenite in steel and enhancing the material's plasticity. Therefore, to ensure and improve the strength and plasticity of the material, the Mn content in this invention is set at 0.81% to 1.06%.

[0015] Phosphorus (P): Primarily used to significantly improve the strength and corrosion resistance of materials. However, excessively high P content can lead to segregation at grain boundaries, reducing the material's plasticity and toughness, and also affecting its corrosion resistance. Therefore, in this invention, it is added in combination with the rare earth element Ce. The dissolved rare earth element not only refines dendrites and increases the equiaxed crystal ratio, suppressing P segregation, but also significantly improves the material's corrosion resistance. In this invention, to achieve significant corrosion resistance, the P content is set at 0.088%–0.102%, and to reduce P segregation in the cast billet, the P / Ce ratio is limited to 6.3–6.5.

[0016] Sulfur (S) is a harmful impurity element in steel, which easily forms defects such as segregation and inclusions, and deteriorates the impact toughness and hot working performance of steel plates. However, if the S content is controlled too low, it will increase the smelting cost. Therefore, in this invention, the S content should be controlled below 0.008%.

[0017] Cu: One of the important corrosion-resistant elements. This element often accumulates within rust layers, effectively increasing the permeability of corrosive media. It also readily combines with phosphorus (P) to form a dense Cu-P compound protective rust layer on the substrate surface, further inhibiting the penetration of corrosive media. Simultaneously, this element often dissolves in femines (Fe) to form substitutional solid solutions, exhibiting solid solution strengthening effects and thus improving the strength of the steel plate. However, high Cu content not only increases costs but also easily leads to "copper embrittlement" defects at the edges of the steel plate in the absence of nickel (Ni). Therefore, this invention avoids the "copper embrittlement" defect by adding rare earth element Ce to achieve a dispersed distribution and combining it with a heating process. This invention limits its content to a range of 0.13% to 0.21%.

[0018] Ti: A strong C and N compound forming element, and an important element for improving strength. During the heating process of steel plates, it often forms Ti-N compounds with N to inhibit austenite grain growth and achieve the purpose of grain refinement; it also forms fine carbides and nitrides or carbonitrides with C and N, which precipitate fine compounds during the cooling and coiling of the steel plate, playing a precipitation strengthening role. This invention limits its range to 0.027% to 0.047%.

[0019] Sb: An effective element for improving the corrosion resistance and wear resistance of steel plates. This element readily forms a dense oxide film on the substrate surface, enhancing the passivation ability of the steel plate. Through the combined addition of P, Cu, and Cr, it synergistically accumulates in the rust layer, forming a dense and tightly bonded Sb-P-Cu-Cr composite protective rust layer, which further hinders the intrusion of corrosive media. Furthermore, the Sb3O4 hard phase formed within the substrate precipitates along grain boundaries during cooling and coiling, further improving the wear resistance of the steel plate. In this invention, the Sb content is controlled at 0.104%–0.124%.

[0020] Mo exists in steel primarily in three forms: some dissolves in iron to form a substitutional solid solution, increasing the yield strength of the steel; some reacts with free carbon in the steel to form the Mo-C hard phase Mo2C3, significantly improving the hardness and wear resistance of the steel; and a small amount segregates at grain boundaries. When Mo is added in combination with rare earth element Ce, Ce's strong affinity reduces Mo segregation at grain boundaries. Ce promotes the uniform precipitation of the Mo2C3 hard phase and inhibits its aggregation and growth, further improving the wear resistance of the steel plate. Especially when added in combination with Si, it can form Mo2Si3 hard phase particles with free Si in the steel. By controlling the final rolling temperature and coiling temperature, micron-sized (40-70 μm) Mo2Si3 hard phase particles will be dispersed near grain boundaries or inside grains, greatly improving the hardness and wear resistance of the steel. To better leverage the synergistic wear-resistant effect of Si and Mo, this invention limits the Si / Mo ratio to 1.1-2.8. However, excessive Mo content will increase its segregation at grain boundaries, deteriorating the steel's ductility, toughness, and weldability. The Mo content should be controlled between 0.18% and 0.29%.

[0021] Als: An important deoxidizing element that purifies molten steel into a low-oxygen environment, preventing excessive reaction between rare earth elements and the oxygen content in the steel. This allows the rare earth elements to fully exert their solid solution properties. A significant portion of its function is to be added in conjunction with rare earth elements. This invention limits its content to 0.048%–0.071%.

[0022] Ce: (1) As an effective deoxidizing and desulfurizing element, it can purify molten steel and improve the mechanical properties of the product; it can change the morphology and type of inclusions, reduce the potential difference between inclusions and the matrix, reduce the tendency of electrochemical corrosion caused by inclusions, and effectively improve the corrosion resistance of steel plates; (2) It has the effect of dispersing Cu, which can avoid the generation of "copper brittleness" defects on the one hand, and improve the utilization rate of Cu on the other hand, thereby increasing the ratio of the protective phase α-FeOOH / γ-FeOOH, improving the stability of the rust layer, and further improving the corrosion resistance of steel plates; (3) The addition of Ce can effectively inhibit P segregation, thereby improving the plasticity and toughness of the material, especially in the case of high P in this invention. In order to make the corrosion resistance effect significant and inhibit P segregation, the P / Ce value is limited to 6.3 to 6.5 in this invention; (4) It improves the segregation of Mo, promotes the uniform precipitation of hard phases Mo2C3 and Mo2Si3 and inhibits the aggregation and growth of this phase, thereby improving the wear resistance of steel plates. The present invention limits its range to 0.0139% to 0.0158%.

[0023] This invention also provides a low-cost method for manufacturing wear-resistant and corrosion-resistant steel for photovoltaic brackets of 550MPa grade. The method involves pre-desulfurization of molten iron, top and bottom reblowing in a converter, LF ladle refining, slab continuous casting, billet heating, hot continuous rolling, laminar cooling, and coiling to obtain wear-resistant and atmospheric corrosion-resistant steel containing the above-mentioned chemical composition. The specific contents include the following.

[0024] Smelting: First, the molten iron undergoes desulfurization pretreatment to ensure that the S content in the desulfurized molten iron is ≤0.002%. A combined top and bottom blowing process is adopted, and the converter tapping temperature is 1641-1655℃. Then, it is fed into the LF furnace for heating and composition fine-tuning. After that, Si-Ca wire feeding is performed to further reduce the O and S content, ensuring that the free O content in the steel is controlled below 4.0ppm. 7-9 minutes before the end of vacuum treatment in the LF furnace, 1.54-1.76 kg / ton of 20% Ce-Fe rare earth alloy is added to the LF furnace. Then, weak argon blowing (argon flow rate 106-126 NL / min, pressure 0.14-0.27 MPa) and stirring are performed for 3.7-5.7 minutes to ensure that inclusions are fully floated and modified.

[0025] Slab continuous casting: During slab continuous casting, protective slag is used throughout the process to protect the molten steel and prevent it from being exposed to air. The thickness of the continuously cast slab is 210–230 mm. Because the rare earth element Ce in the steel has a strong affinity and easily forms a large number of rare earth inclusions with the O and S elements in the steel, affecting the fluidity of the molten steel, the casting speed is controlled at 1.26–1.46 m / min. Furthermore, the high P content in this invention makes P segregation highly likely, thus reducing the plasticity and toughness of the material. Therefore, to reduce center segregation of the continuously cast slab, the superheat is controlled between 14–17°C during casting, and electromagnetic stirring technology is employed with a stirring current of 364–368 A and a frequency of 5–7 Hz.

[0026] Billet heating: One of the main ways this invention improves the strength of steel plates is through microalloying solid solution strengthening, especially with the addition of Si and Mo elements. To ensure sufficient solid solution of Si, Mo, and other alloying elements, the billet is heated to 1268–1294°C. The steel of this invention is copper-containing steel. Normally, Cu and Ni elements should be added together to suppress the "copper embrittlement" defect. However, to reduce costs, this invention does not add the precious metal Ni, but instead avoids the "copper embrittlement" defect in copper-containing steel by developing a reasonable heating process. Therefore, to avoid the "copper embrittlement" defect caused by the precipitation of low-melting-point element Cu on the steel plate surface, the heating furnace atmosphere is set to a reducing atmosphere with an air-fuel ratio between 1.7 and 2.1. When the heating temperature is below 1105℃, slow heating is required, with the heating rate controlled at 5.8 to 7.8℃ / min to ensure uniform temperature inside and outside the billet. When the temperature is above 1105℃, rapid heating is required, with the heating rate controlled at 15.7 to 17.7℃ / min. Since the longer the heating time, the more favorable it is for Cu to diffuse along the austenite grain boundaries, the easier it is to generate the "copper embrittlement" defect. Therefore, the furnace time is controlled to ≤190min, preferably 165 to 188min, of which the holding time in the soaking section is 29 to 44min.

[0027] Rolling: A two-stage temperature-controlled rolling process is adopted, consisting of roughing and finishing rolling. Roughing employs a high-temperature, high-reduction method, with a final rolling temperature of 1099–1134℃ and a cumulative reduction rate of 81.9%–85.1%. This high cumulative reduction not only compresses defects in the cast billet but also increases deformation to form more dislocations, thereby enhancing the material's strength through dislocation strengthening. The initial rolling temperature for finishing rolling is 1081℃–1108℃. To eliminate the adverse effects of dislocation strengthening on plasticity during roughing and to ensure the sufficient precipitation of Mo2C3 and Mo2Si3 hard phases, a higher final rolling temperature is set at 928–944℃. To ensure the flatness and precision of the finished steel plate, the reduction rate in the final finishing rolling is controlled at 16.7%–17.8%. Furthermore, the rolling crown is controlled to be between 42μm and 48μm during the rolling process.

[0028] After finishing rolling, a two-stage laminar flow cooling method is used. The first stage involves cooling at a rate of 16–23 °C / s to 751–771 °C (this temperature range corresponds to the ferrite transformation region), followed by air cooling for 6–9 seconds. This stage ensures sufficient soft-phase ferrite structure and facilitates the precipitation and growth of Mo2C3 and Mo2Si3 phases, guaranteeing the steel plate's plasticity and wear resistance. The second stage involves cooling at a rate of 26–36 °C / s to 607–627 °C before coiling. This stage generates sufficient hard-phase bainite to ensure the product's strength. Furthermore, this coiling temperature effectively refines the grains and inhibits the coarsening of the Mo2C3 and Mo2Si3 precipitates.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The aforementioned chemical composition and production process can significantly reduce the production cost of wear-resistant and corrosion-resistant steel for photovoltaic brackets. Through precise control of the composition and microstructure ratio, the produced steel plates with a thickness of 2.0–4.0 mm exhibit a yield strength >550 MPa, tensile strength >690 MPa, elongation >25%, and satisfactory cold bending performance, demonstrating excellent mechanical properties. By controlling the hard phase precipitates and their size, the surface hardness of this invented steel is 205–211 HBW, with a wear rate of 30.3%–31.5% relative to Q345B. Through a reasonable combination of corrosion-resistant elements, in rapid corrosion evaluation tests under simulated C4 atmospheric conditions, the corrosion rate of this invented steel relative to Q345B is 32.78%–34.3%. The steel of this invention has a simple manufacturing process and low cost. It not only has excellent mechanical properties, but also excellent wear resistance and atmospheric corrosion resistance. It can ensure that no defects such as cracks will occur in the photovoltaic bracket during subsequent processing such as bending. The photovoltaic bracket made of it can be widely used in harsh environments such as deserts and areas with heavy industrial pollution. Detailed Implementation

[0031] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0032] The present invention will be described in more detail below through examples.

[0033] The composition of the steel in the embodiments of the present invention is shown in Table 1. The main process parameters for smelting and continuous casting of the steel in the embodiments of the present invention are shown in Table 2. The heating process parameters of the steel in the embodiments of the present invention are shown in Table 3. The rolling and coiling process parameters of the steel in the embodiments of the present invention are shown in Table 4. The various properties of the steel in the embodiments of the present invention are shown in Table 5. The microstructure of the steel in the embodiments of the present invention is shown in Table 6. The results of the peripheral immersion corrosion test of the steel in the embodiments of the present invention are shown in Table 7.

[0034] Table 1. Composition (wt%) of steel in embodiments of the present invention

[0035]

[0036] Table 2 Main process parameters for steel smelting and continuous casting in the embodiments of the present invention.

[0037]

[0038] Table 3 Main process parameters for heating steel in the embodiments of the present invention

[0039]

[0040]

[0041] Table 4 Main process parameters for steel rolling and cooling in the embodiments of the present invention

[0042]

[0043] Table 5. Test results of various performance indicators in the embodiments.

[0044]

[0045] Table 6. Microstructure of steel in embodiments of the present invention

[0046]

[0047]

[0048] As can be seen from Table 5, the yield strength of the steel in the embodiments of the present invention is between 571 and 598 MPa, all of which reach the design strength of 550 MPa or more. The tensile strength is between 697 and 714 MPa, the elongation is greater than 25%, and the cold bending performance is qualified. This indicates that the strength of the steel in each embodiment not only meets the design requirements, but also has high plasticity. The hardness value of the steel in the embodiments is between 205 and 211 HBW.

[0049] The wear resistance tests in Table 5 were conducted on a wet rubber wheel abrasive wear testing machine. Samples with dimensions of 57.0 mm × 25.5 mm × 6.0 mm were used for the abrasive wear test. The wear test was conducted according to the "JB / T 7705-1995 Test Method for Wear of Loose Abrasives - Rubber Wheel Method". The test results showed that the wear rate of the steel in the example was between 30.3% and 31.5% relative to Q345B, indicating that the steel in the example has higher wear resistance.

[0050] Table 6 shows that the microstructure of the invented steel consists of ferrite, bainite, and a small amount of pearlite. The microstructure is uniform and fine, and fine Mo2Si3 hard phases are precipitated in the microstructure. Among them, the proportion of Mo2Si3 with a size range of 40-70 μm is 85.7%-87.6%. This level of precipitated phase is beneficial to improving the wear resistance of the invented steel.

[0051] To simulate corrosion under C4 atmospheric conditions, a 72-hour cyclic immersion rapid corrosion evaluation test was conducted on the invented steel according to the test method specified in TB / T 2375-1993. The corrosion resistance of the invented steel was evaluated using the weight loss method. Table 7 shows the comparison results of the corrosion resistance of the steel in the embodiments of the present invention and the comparative steel. As can be seen from Table 7, the corrosion resistance of the steel in the embodiments of the present invention is significantly better than that of the comparative steel Q345B.

[0052] Table 7 Comparison of rapid corrosion test results between the steel of the present invention embodiment and the comparative steel.

[0053]

[0054] It is hereby noted that the above embodiments are only for illustrating the technical concept and features of the present invention, and are not intended to limit the present invention. Any equivalent substitutions or modifications made without departing from the essence of the present invention fall within the protection scope of the present invention.

Claims

1. A low-cost, 550MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets, characterized in that, The chemical composition of the steel, by weight percentage, is as follows: C: 0.064%–0.082%, Si: 0.34%–0.52%, Mn: 0.81%–1.06%, P: 0.088%–0.102%, S: ≤0.008%, Cu: 0.13%–0.21%, Sb: 0.104%–0.124%, Ti: 0.027%–0.047%, Mo: 0.18%–0.29%. Ce: 0.0139%~0.0158%, Als: 0.048%~0.071%, with P / Ce controlled at 6.3~6.5, Si / Mo controlled at 1.1~2.8, and the balance being Fe and unavoidable impurities; the manufacturing method includes smelting, slab continuous casting, slab heating, rolling, laminar flow cooling and coiling, with the slab heated to 1268~1294℃, the air-fuel ratio between 1.7 and 2.1, and the heating temperature... The heating rate is controlled at 5.8–7.8℃ / min below 1105℃; and at 15.7–17.7℃ / min above 1105℃; the furnace time is controlled to be ≤190min; rolling adopts a two-stage controlled rolling process of roughing and finishing, with the roughing finishing temperature at 1099–1134℃ and the cumulative reduction rate at the roughing stage at 81.9%–85.1%; the finishing rolling starting temperature is 1081℃–1108℃, and the finishing... The final rolling temperature is 928–944℃. The reduction rate of the last rolling in the finishing mill is controlled at 16.7%–17.8%, and the rolling crown is controlled at 42µm–48µm. After finishing milling, a two-stage laminar flow cooling is adopted. The first stage is cooled to 751–771℃ at a cooling rate of 16–23℃ / s, followed by air cooling for 6–9s. Then, the second stage of cooling is carried out at a cooling rate of 26–36℃ / s, cooling to 607–627℃ before coiling.

2. The low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 1, characterized in that, The metallographic structure of the steel consists of ferrite, bainite, and a small amount of pearlite, with ferrite accounting for 33.5% to 34.9% and bainite accounting for 52.3% to 53.9%. The ferrite grain size is ≥10.

5. Fine Mo2Si3 hard phases are precipitated in the microstructure, of which Mo2Si3 with a size range of 40 to 70 μm accounts for 85.7% to 87.6%.

3. The low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 1, characterized in that, The steel has a yield strength between 571 and 598 MPa, a tensile strength between 697 and 714 MPa, and an elongation greater than 25%. The surface hardness of the steel is 205 to 211 HBW, and the wear rate relative to Q345B is 30.3% to 31.5%.

4. The low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 1, characterized in that, In rapid corrosion evaluation tests under simulated C4 atmospheric conditions, the corrosion rate of the steel was 1.101~1.152 g / m³. 2 The corrosion rate relative to Q345B is 32.78%~34.3%.

5. The low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 1, characterized in that, The thickness of the steel plate is 2.0 to 4.0 mm.

6. A method for manufacturing low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets as described in any one of claims 1 to 5, comprising smelting, slab continuous casting, slab heating, rolling, laminar flow cooling, and coiling, characterized in that, The billet is heated to 1268–1294℃, with an air-fuel ratio between 1.7 and 2.

1. When the heating temperature is below 1105℃, the heating rate is controlled at 5.8–7.8℃ / min; when the temperature is above 1105℃, the heating rate is controlled at 15.7–17.7℃ / min. The furnace time is controlled to be ≤190min. Rolling is a two-stage controlled rolling process, with roughing and finishing. The final rolling temperature of the roughing stage is 1099–1134℃, and the cumulative reduction rate during the roughing stage is 81.9%–85.1%. Finishing... The rolling temperature is 1081℃~1108℃, the finishing rolling temperature is 928~944℃, the reduction rate of the last finishing rolling is controlled at 16.7%~17.8%, and the rolling crown is controlled at 42µm~48µm. After finishing rolling, a two-stage laminar flow cooling is adopted. The first stage is cooled to 751~771℃ at a cooling rate of 16~23℃ / s, followed by air cooling for 6~9s. Then, the second stage of cooling is carried out at a cooling rate of 26~36℃ / s, cooling to 607~627℃ before coiling.

7. The method for manufacturing low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 6, characterized in that, In the smelting process, the molten iron is first desulfurized and pretreated. After desulfurization, the S content in the molten iron is ≤0.002%. A combined top and bottom blowing process is adopted, and the tapping temperature of the converter is 1641~1655℃. Then, Si-Ca wire feeding treatment is carried out to control the free O content in the steel to below 4.0ppm. 7~9 minutes before the end of vacuum treatment in the LF furnace, 1.54~1.76kg / ton of 20% Ce-Fe rare earth alloy is added to the LF furnace, followed by weak argon blowing.

8. The method for manufacturing low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 7, characterized in that, The flow rate of argon gas for weak blowing is 106~126 NL / min, the pressure is 0.14~0.27 MPa, and the weak blowing time is 3.7~5.7 min.

9. The method for manufacturing low-cost 550MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 6, characterized in that, The heating time of the billet in the furnace is 165 to 188 minutes, of which the holding time in the soaking zone is 29 to 44 minutes.

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