A 390MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method

Abstract

This invention discloses a 390MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. The chemical composition of the steel contains C: 0.044%–0.064%, Si: 0.23%–0.39%, Mn: 0.51%–0.71%, P: 0.073%–0.087%, S: ≤0.01%, Cr: 0.43%–0.67%, Cu: 0.09%–0.17%, Sb: 0.077%–0.097%, Mo: 0.09%–0.21%, Ce: 0.0118%–0.0138%, and Als: 0.043%–0.067%, wherein the P / Ce ratio is controlled at 6.1–6.4, and the Si / Mo ratio is controlled at 1.8–2.6. The manufacturing method includes smelting, slab continuous casting, slab heating, rolling, laminar flow cooling, and coiling. The steel has a Rel > 390 MPa, Rm > 530 MPa, and A > 27%; its surface hardness is 158–163 HBW, its wear rate relative to Q345B is 35.2%–36.2%, and its corrosion rate relative to Q345B is 35.43%–36.71%. This invention provides a photovoltaic bracket steel that simultaneously possesses excellent wear resistance and atmospheric corrosion resistance, solving the problem of existing technologies lacking wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of corrosion-resistant steel for photovoltaic brackets, and relates to a 390MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. Background Technology

[0002] As the "skeleton" supporting photovoltaic modules, the performance of photovoltaic (PV) mounting systems directly affects the lifespan of a photovoltaic power station. During operation, PV mounting systems must withstand not only the loads of the modules themselves, wind, and snow, but also the corrosive effects of external environments such as moisture, light, and temperature.

[0003] Especially in windy and sandy desert areas, photovoltaic (PV) brackets must withstand wind and sand erosion. Therefore, the most important characteristic of PV brackets during application is their wear resistance and atmospheric corrosion resistance. Currently, the commonly used materials for PV brackets in the industry are aluminum alloy, hot-dip galvanized steel, and weathering steel. Among them, aluminum alloy brackets are expensive and have no price advantage. Moreover, aluminum alloys are usually used on the roofs of civil buildings, and their load-bearing capacity is low, making them unsuitable for large-scale PV power generation projects. Traditional hot-dip galvanized steel brackets not only have long manufacturing cycles and a polluting galvanizing process that is detrimental to the environment, but this production process can no longer meet the requirements for controlling project costs. Weathering steel often only considers its atmospheric corrosion resistance while neglecting the wear resistance required for the brackets during service. Therefore, there is an urgent need to develop a PV bracket steel that is simple to manufacture, environmentally friendly, and possesses excellent wear resistance and atmospheric corrosion resistance.

[0004] Prior to this invention,

[0005] The invention patent with publication number CN 114438411 A, entitled "A Weathering Steel for Photovoltaic Brackets and Its Production Method", has the following composition: C: 0.030%~0.070%, Si: 0.20%~0.50%, Mn: 0.30%~0.20%, P: ≤0.020%, S: ≤0.005%, Nb: 0.01%~0.05%, Ti: 0.010%~0.030%, Ni: 0.05%~0.30%, Cu: 0.20%~0.50%, Cr: 0.4%~0.8%, N: ≤0.006%, Ca: 0.0010%~0.0030%, with the remainder being Fe and impurity elements. This invention improves product strength through Nb-Ti microalloying. It incorporates high levels of precious metals such as Nb, Cu, and Ni, resulting in higher production costs. The target rolling thickness of the steel used for photovoltaic brackets is not specified, but based on low-temperature impact performance test requirements and example results, the steel plate thickness is relatively thick (at least 10mm). The corrosion resistance of this steel is assessed using the atmospheric corrosion resistance index I, which is calculated based on a theoretical formula but not verified through corrosion testing. Furthermore, this theoretical formula does not consider the influence of other elements on corrosion resistance. Therefore, the actual corrosion resistance of this steel is unknown, and the patent does not explain the influence of elements on wear resistance.

[0006] The invention patent with publication number CN 115747644 A, entitled "A Rare Earth Weathering Steel for Photovoltaic Brackets and Its Production Method," has the following composition: C: 0.06%–0.12%, Si: 0.30%–0.50%, Mn: 0.8%–1.0%, P: ≤0.018%, S: ≤0.005%, Cu: 0.20%–0.35%, Cr: 0.40%–0.55%, Ni: 0.05%–0.15%, Ti: 0.020%–0.030%, La: 15–25 ppm, Alt: 0.020%–0.050%, with the remainder being Fe and impurity elements. The addition of the precious metal Ni to this steel inevitably increases its cost. Furthermore, the patent only describes the steel's good corrosion resistance without providing specific corrosion resistance parameters, and it fails to explain the impact on wear resistance.

[0007] The invention patent with publication number CN 114574782 A, entitled "A 450MPa Grade Wear-Resistant Corrosion Steel and Its Manufacturing Method," has the following composition: C: 0.061%–0.082%, Si: 0.51%–0.79%, Mn: 0.45%–0.89%, P≤0.018%, S≤0.006%, Cr: 0.81%–1.31%, Cu: 0.14%–0.24%, Sb: 0.041%–0.075%, W: 0.15%–0.35%, Ti: 0.051%–0.072%, Als: 0.015%–0.045%, N≤0.004%, with the balance being Fe and unavoidable impurities. 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.

[0008] The composition of the rare earth wear-resistant steel NM400 coil with excellent low-temperature toughness and its production method, published in CN 112322976 A, is as follows: C: 0.18%~0.20%, Si: 0.30%~0.50%, Mn: 1.30%~1.45%, P: ≤0.012%, S: ≤0.003%, Nb: 0.015%~0.025%, Ti: 0.010%~0.025%, Cr: 0.25%~0.40%, Ce: 0.0005%~0.0015%, Ca: 0.0010%~0.0030%, Al: 0.020%~0.050%, H: ≤2ppm, O: ≤30ppm, N: ≤50ppm, with the balance being Fe and impurity elements. This invention steel is an ultra-high strength wear-resistant steel produced using a heat treatment process (quenching + tempering). This heat treatment process obtains the target microstructure (ferrite + martensite and a small amount of retained austenite) to ensure the wear resistance of the steel. However, this process is lengthy and costly, and the resulting microstructure is highly brittle, leading to poor formability of the steel plate. Summary of the Invention

[0009] The purpose of this invention is to provide a 390MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method. This photovoltaic bracket steel has excellent wear resistance and atmospheric corrosion resistance, solving the problem that the existing technology does not have wear resistance.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] This invention proposes a wear-resistant and corrosion-resistant steel for photovoltaic brackets with a strength of 390MPa. The chemical composition by weight percentage is: C: 0.044%–0.064%, Si: 0.23%–0.39%, Mn: 0.51%–0.71%, P: 0.073%–0.087%, S: ≤0.01%, Cr: 0.43%–0.67%, Cu: 0.09%–0.17%, Sb: 0.077%–0.097%, Mo: 0.09%–0.21%, Ce: 0.0118%–0.0138%, Als: 0.043%–0.067%, wherein the P / Ce ratio is controlled at 6.1–6.4, the Si / Mo ratio is controlled at 1.8–2.6, and the balance is Fe and unavoidable impurities.

[0012] The reason for selecting the above alloying elements and their contents in this invention is as follows:

[0013] 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 0.044%–0.064%.

[0014] 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 (20-50 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 0.23%-0.39% 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 1.8 and 2.6.

[0015] 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 0.51% to 0.71%.

[0016] 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 0.073%–0.087%. To reduce P segregation in the cast billet, the P / Ce ratio is limited to 6.1–6.4.

[0017] Sulfur (S) is a harmful impurity element in steel, easily forming defects such as segregation and inclusions, which deteriorates the impact toughness and hot working properties of the steel plate. However, excessively low S content increases smelting costs. Therefore, the S content in this invention should be controlled below 0.01%.

[0018] Cr: Primarily enhances steel strength through solid solution strengthening. Simultaneously, this element is also an important corrosion-resistant element, often accumulating within rust layers. It readily forms a dense oxide film on the steel plate surface and also combines with Cu to form a dense Cr-Cu compound protective rust layer on the substrate surface, significantly inhibiting the penetration of corrosive media and achieving a dual-layer corrosion resistance effect, thus partially replacing the corrosion resistance function of Cu. However, excessively high Cr content not only deteriorates the weldability of the steel plate but also increases the difficulty of smelting. Therefore, the Cr content in this invention is controlled at 0.43%–0.67%.

[0019] 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 0.09% to 0.17%.

[0020] 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 0.077%–0.097%.

[0021] 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 Mo2Si3, 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 Mo2Si3 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 (20-50 μm) hard phase Mo2Si3 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 1.8-2.6. 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 0.09% and 0.21%.

[0022] 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 0.043%–0.067%.

[0023] 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 function 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 value of P / Ce is limited to 6.1 to 6.4 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 0.0118% to 0.0138%.

[0024] This invention also provides a method for manufacturing wear-resistant and corrosion-resistant steel for photovoltaic brackets of grade 390MPa. 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.

[0025] 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 1634-1646℃. 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 4.2ppm. 7-9 minutes before the end of vacuum treatment in the LF furnace, 1.31-1.53 ​​kg / ton of 20% Ce-Fe rare earth alloy is added to the LF furnace. Then, weak argon blowing (argon flow rate 103-123 NL / min, pressure 0.12-0.24 MPa) and stirring are performed for 3.4-5.4 minutes to ensure that inclusions are fully floated and modified.

[0026] 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 Ce, a rare earth element in the steel, has a strong affinity and easily forms a large number of rare earth inclusions with O and S elements in the steel, affecting the fluidity of the molten steel, the casting speed is controlled at 1.22–1.42 m / min. Furthermore, the high P content in this invention makes P segregation highly likely, thus reducing the material's plasticity and toughness. Therefore, to reduce center segregation in the continuously cast slab, the superheat is controlled between 16–19°C during casting, and electromagnetic stirring technology is employed with a stirring current of 364–368 A and a frequency of 5–7 Hz.

[0027] Billet heating: One of the main ways this invention improves the strength of the steel plate 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 1261–1287°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 1.5 and 1.8. When the heating temperature is below 1105℃, slow heating is required, with the heating rate controlled at 5.3 to 7.3℃ / 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 14.7 to 16.7℃ / min. Since the longer the heating time, the more favorable it is for Cu to diffuse along the austenite grain boundaries, the more likely "copper embrittlement" defects will occur. Therefore, the furnace time is controlled to be ≤190min, preferably 152 to 175min, of which the holding time in the soaking zone is 22 to 37min.

[0028] 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 1091–1124℃ and a cumulative reduction of 81.2%–84.3%. 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 1071℃–1098℃. To eliminate the adverse effects of dislocation strengthening on plasticity during roughing and to ensure the full precipitation of the Mo2C3 and Mo2Si3 hard phases, a higher final rolling temperature is set at 921–937℃. To ensure the flatness and precision of the finished steel plate, the reduction rate in the final finishing rolling is controlled at 19.3%–20.8%.

[0029] After finishing rolling, a two-stage laminar flow cooling method is used. The first stage involves cooling at a rate of 11–18 °C / s to 761–781 °C (this temperature range corresponds to the ferrite transformation region), followed by air cooling for 5–8 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 22–32 °C / s to 619–639 °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.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The 4.0–8.0 mm thick photovoltaic support steel produced using the aforementioned chemical composition and process exhibits excellent performance. Through precise control of the composition and microstructure ratio, the steel achieves a yield strength >390 MPa, tensile strength >530 MPa, elongation >27%, and satisfactory cold bending performance, demonstrating excellent plasticity. By controlling the hard phase precipitates and their size, the surface hardness of the steel is 158–163 HBW, with a wear rate relative to Q345B of 35.2%–36.2%. Through a rational combination of corrosion-resistant elements, in rapid corrosion evaluation tests under simulated C4 atmospheric conditions, the corrosion rate of the steel relative to Q345B is 35.43%–36.71%. The photovoltaic support steel of this invention features a simple process, excellent plasticity, and superior wear resistance and atmospheric corrosion resistance, preventing defects such as cracks during bending and other processing deformations. Photovoltaic supports manufactured using this steel can be widely applied in harsh environments such as deserts and areas with heavy industrial pollution. Detailed Implementation

[0032] 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.

[0033] The present invention will be described in more detail below through examples.

[0034] 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.

[0035] Table 1. Composition (wt%) of steel in embodiments of the present invention

[0036]

[0037] Table 2 Main process parameters for steel smelting and continuous casting in the embodiments of the present invention.

[0038]

[0039]

[0040] Table 3 Heating process of steel in embodiments of the present invention

[0041] Example Heating temperature / ℃ air-fuel ratio Slow heating rate / ℃ / min Rapid heating rate / °C / min Total heating time / t Heat preservation time / t 1 1261 1.5 5.3 14.7 152 22 2 1265 1.6 5.6 14.9 156 25 3 1269 1.6 5.9 15.2 159 28 4 1274 1.7 6.2 15.5 163 31 5 1278 1.6 6.5 15.8 167 33 6 1281 1.8 6.8 16.1 169 35 7 1284 1.7 7.0 16.4 172 37 8 1287 1.8 7.3 16.7 175 36

[0042] Table 4 Main process parameters for steel rolling and cooling in the embodiments of the present invention

[0043]

[0044] Table 5 shows the test results of various performance indicators in the embodiments.

[0045]

[0046] Table 6. Microstructure of steel in the embodiments of the present invention

[0047]

[0048]

[0049] As can be seen from Table 5, the yield strength of the steel in the embodiments of the present invention is between 420 and 447 MPa, all of which reach the design strength of 390 MPa or more. The tensile strength is between 537 and 556 MPa, the elongation is greater than 27%, 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 ductility and formability. The hardness value of the steel in the embodiments is between 158 and 163 HBW.

[0050] 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, which was performed according to the "JB / T7705-1995 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 35.2% and 36.2% relative to Q345B, indicating that the steel in the example has higher wear resistance.

[0051] The results in Table 6 show 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 20-50 μm is 81.2%-83.6%. This level of precipitated phase is beneficial to improving the wear resistance of the invented steel.

[0052] 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.

[0053] Table 7 Comparison of rapid corrosion test results between the steel of the present invention embodiment and the comparative steel.

[0054]

[0055] 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 wear-resistant and corrosion-resistant steel for photovoltaic brackets with a strength of 390MPa, characterized in that, The chemical composition of the steel, by weight percentage, is as follows: C: 0.044%–0.064%, Si: 0.23%–0.39%, Mn: 0.51%–0.71%, P: 0.073%–0.087%, S: ≤0.01%, Cr: 0.43%–0.67%, Cu: 0.09%–0.17%, Sb: 0.083%–0.097%, Mo: 0.09%–0. 21%, Ce: 0.0118%~0.0138%, Als: 0.043%~0.067%, with P / Ce controlled at 6.1~6.4, Si / Mo controlled at 1.8~2.6, 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 1261~1287℃ and the air-fuel ratio at 1.5~1. Between 0.8 and 0.8, when the heating temperature is below 1105℃, the heating rate is controlled at 5.3~7.3℃ / min; when the temperature is above 1105℃, the heating rate is controlled at 14.7~16.7℃ / min; the furnace time is controlled at ≤190min; the rolling adopts a two-stage controlled rolling process of roughing and finishing, the finishing temperature of roughing is 1091~1124℃, and the cumulative reduction rate of the roughing stage is 81.2%~84.3%; the starting temperature of finishing is 1071~1098℃, the finishing temperature is 921~937℃, and the reduction rate of the last finishing rolling is controlled at 19.3%~20.8%; after finishing, a two-stage laminar flow cooling is adopted. The first stage is cooled to 761~781℃ at a cooling rate of 11~18℃ / s, followed by air cooling for 5~8s, and then the second stage is cooled to 619~639℃ at a cooling rate of 22~32℃ / s before coiling.

2. The wear-resistant and corrosion-resistant steel for photovoltaic brackets of 390MPa grade 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 46.4% to 49.3% and bainite accounting for 28.5% to 30.3%. The ferrite grain size is ≥10. Fine Mo2Si3 hard phases are precipitated in the microstructure, of which the proportion of Mo2Si3 with a size range of 20 to 50 μm is 81.2% to 83.6%.

3. The wear-resistant and corrosion-resistant steel for photovoltaic brackets of 390MPa grade according to claim 1, characterized in that, The steel has a yield strength > 390 MPa, tensile strength > 530 MPa, and elongation > 27%; the surface hardness of the steel is 158~163 HBW, and the wear rate relative to Q345B is 35.2%~36.2%.

4. The wear-resistant and corrosion-resistant steel for photovoltaic brackets of 390MPa grade according to claim 1, characterized in that, In rapid corrosion evaluation tests under simulated C4 atmospheric conditions, the corrosion rate of the steel was 1.184~1.227 g / m³. 2 The corrosion rate relative to Q345B is 35.43%~36.71%.

5. The wear-resistant and corrosion-resistant steel for photovoltaic brackets of 390MPa grade according to claim 1, characterized in that, The thickness of the steel plate is 4.0 to 8.0 mm.

6. A method for manufacturing the 390MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets as described in any one of claims 1 to 5, comprising smelting, continuous casting of slabs, heating of slabs, rolling, laminar flow cooling, and coiling, characterized in that, The billet is heated to 1261–1287℃, with an air-fuel ratio between 1.5 and 1.

8. When the heating temperature is below 1105℃, the heating rate is controlled at 5.3–7.3℃ / min; when the temperature is above 1105℃, the heating rate is controlled at 14.7–16.7℃ / min. The furnace time is controlled to be ≤190 min. Rolling is a two-stage controlled rolling process consisting of roughing and finishing. The finishing temperature of the roughing stage is 1091–1124℃, and the cumulative reduction rate during the roughing stage is 81.2%. ~84.3%; the initial rolling temperature of finishing mill is 1071~1098℃, the final rolling temperature of finishing mill is 921~937℃, and the reduction rate of the last rolling of finishing mill is controlled at 19.3%~20.8%; after finishing mill, two-stage laminar flow cooling is adopted. The first stage is cooled to 761~781℃ at a cooling rate of 11~18℃ / s, followed by air cooling for 5~8s. Then, the second stage of cooling is carried out at a cooling rate of 22~32℃ / s, and the temperature is cooled to 619~639℃ before coiling.

7. The method for manufacturing the 390MPa 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 1634~1646℃. Then, Si-Ca wire feeding treatment is carried out to control the free O content in the steel to below 4.2ppm. 7~9 minutes before the end of vacuum treatment in the LF furnace, 1.31~1.53kg / ton of 20% Ce-Fe rare earth alloy is added to the LF furnace, followed by weak argon blowing.

8. The method for manufacturing the 390MPa 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 103~123 NL / min, the pressure is 0.12~0.24 MPa, and the weak blowing time is 3.4~5.4 min.

9. The method for manufacturing the 390MPa 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 152 to 175 minutes, of which the holding time in the soaking zone is 22 to 37 minutes.

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