A 690MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and its manufacturing method

Abstract

The present invention discloses a 690MPa wear-resistant and corrosion-resistant steel for photovoltaic brackets and a manufacturing method thereof. The chemical composition (wt%) of the steel comprises C 0.083-0.103, Si 0.41-0.59, Mn 0.98-1.19, P 0.092-0.106, S ≤ 0.006, Cr 0.62-0.86, Cu 0.18-0.26, Sb 0.098-0.117, Ti 0.048-0.063, Mo 0.23-0.35, Ce 0.0144-0.0164, and Al 0.048-0.068, wherein the P / Ce ratio is 6.3-6.5, and the Si / Mo ratio is 1.1-2.6. The manufacturing method comprises smelting, slab continuous casting, slab heating, rolling, laminar cooling, and coiling. The Rel of the steel of the present invention is 721-733 MPa, Rm is 788-808 MPa, and A is greater than 29%; the surface hardness of the steel is 234-241 HBW, the wear rate relative to Q345B is 26.4%-27.1%, and the corrosion rate relative to Q345B is 28.62%-30.83%, which solves the problem that the existing technology does not have wear resistance.

Description

Technical Field

[0001] The present invention belongs to the field of corrosion-resistant steel for photovoltaic brackets and relates to a 690MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and a manufacturing method thereof. Background Art

[0002] As a crucial support device in photovoltaic power generation systems, photovoltaic brackets' performance directly impacts the lifespan of photovoltaic power stations. Because they are exposed to the atmosphere for extended periods, they must withstand erosion from external factors, including moisture, light, and temperature. This is particularly true in windy and sandy desert regions, where they are also subject to abrasion from wind and sand, which can affect the bracket's safety and durability. Therefore, the material's corrosion and wear resistance must be considered.

[0003] Currently, the main materials used in the manufacture of photovoltaic brackets are aluminum alloy, hot-dip galvanized steel, and weathering steel. Aluminum alloy brackets are relatively expensive and have low load-bearing capacity, making them uncompetitive. The production process for hot-dip galvanized steel is complex, and the galvanizing process is highly environmentally polluting. Weathering steel, however, is an ideal material for manufacturing photovoltaic brackets due to its inherent corrosion resistance. However, domestic production of weathering steel for photovoltaic brackets often focuses solely on its atmospheric corrosion resistance, ignoring the wear resistance required for the bracket's operational life. Furthermore, with the development of the photovoltaic industry, thin-gauge, high-strength steel for photovoltaic brackets has become the preferred choice. Therefore, there is an urgent need to develop a thin-gauge, high-strength steel for photovoltaic brackets that also exhibits excellent wear and atmospheric corrosion resistance.

[0004] Prior to the present invention,

[0005] Publication number CN 115896613 A, "A high-strength, low-cost weathering steel for photovoltaic brackets, 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 remainder being Fe and unavoidable impurities. This invention incorporates the precious metal W, and the addition of W to the steel inevitably increases the alloy cost. Furthermore, this invention utilizes a tempering process to improve the mechanical properties of the steel, which not only extends the production cycle but also increases production costs. Furthermore, this invention describes the effects of elements on atmospheric corrosion resistance and does not examine the wear resistance of steel for photovoltaic brackets.

[0006] Publication number CN116179961A, "A Low-Cost 800MPa-Grade Titanium-Containing Weathering Steel for Photovoltaic Brackets and Its Preparation Method," states that its composition is as follows: C: ≤0.08%, Si: 0.35%-0.50%, Mn: 0.40%-0.60%, P: 0.08%-0.12%, S: ≤0.010%, Cu: 0.25%-0.45%, Cr: 0.75%-1.00%, Ti: 0.120%-0.170%, N ≤0.0040%, and the remainder is Fe and impurities. The high Cu content in this invention not only increases production costs but, without other process controls, can easily cause "copper brittleness" defects on the edges of the steel plate. The corrosion resistance of this inventive steel is assessed solely using the atmospheric corrosion resistance index (I), which is calculated based on a theoretical formula and has not been verified by corrosion testing. The actual corrosion resistance of this inventive steel is unknown. Furthermore, the invention does not mention the specific impact on wear resistance.

[0007] The publication number CN109402508B, "A low-carbon microalloyed Q690 grade high-strength weathering steel and its preparation method", has the following composition: C: 0.03%~0.10%, Si: 0.10%~0.50%, Mn: 1.20%~2.00%, S: 0.002%~0.010%, P: 0.003%~0.015%, Al: 0.01%~0.05%, V: 0.05%~0.15%, N: 0.01%~0.02%, Cr: 0.30%~0.80%, Ni: 0.30%~0.80%, Cu: 0.15%~0.55%, Mo: 0.15%~0.55%, and the balance is Fe and impurities. This invention utilizes VN-Cr microalloying technology to enhance the material's strength and toughness, and improves its corrosion resistance by adding Cu-Ni elements. However, V, Cu, and Ni are all precious metal elements, and the relatively large amounts added in this invention significantly increase production costs. Furthermore, this invention does not address the specific impact on wear resistance, and corrosion resistance is only predicted using the theoretical parameter I. The specific corrosion resistance indicators of the invented steel are not elaborated, making its actual wear and corrosion resistance unknown.

[0008] Publication number CN114737116B states, "A 700MPa-grade wear-corrosion-resistant steel and its manufacturing method." The composition is as follows: C: 0.069% to 0.090%, Si: 0.65% to 0.93%, Mn: 1.18% to 1.59%, P ≤ 0.018%, S ≤ 0.006%, Cr: 0.91% to 1.48%, Cu: 0.14% to 0.24%, Sb: 0.055% to 0.091%, W: 0.45% to 0.65%, Ti: 0.071% to 0.096%, Al: 0.015% to 0.045%, N ≤ 0.004%, with the remainder being Fe and impurities. This invention improves the material's wear resistance through the synergistic effect of Si, Mn, Cr, and W, forming a certain amount of FeMnCrC, TiC, and WC. However, this invented steel is mainly suitable for the manufacture of container steel, and does not have high requirements on the plasticity and forming performance of the material. It is not suitable for the plasticity requirements of photovoltaic brackets during forming. Summary of the Invention

[0009] The present invention aims to provide a 690 MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets and a method for manufacturing the same. This thin-gauge, high-strength steel also offers excellent wear and atmospheric corrosion resistance, resolving the wear resistance issues of existing technologies.

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

[0011] The present invention proposes a 690MPa-grade wear-resistant and corrosion-resistant steel for a photovoltaic bracket, the chemical composition of which is as follows by weight: C: 0.083%-0.103%, Si: 0.41%-0.59%, Mn: 0.98%-1.19%, P: 0.092%-0.106%, S: ≤0.006%, Cr: 0.62%-0.86%, Cu: 0.18%-0.26%, Sb: 0.098%-0.117%, Ti: 0.048%-0.063%, Mo: 0.23%-0.35%, Ce: 0.0144%-0.0164%, Als: 0.048%-0.068%, wherein the P / Ce ratio is controlled within a range of 6.3-6.5, the Si / Mo ratio is controlled within a range of 1.1-2.6, and the balance is Fe and unavoidable impurities.

[0012] The present invention selects the above alloying element types and contents because:

[0013] C: A key element in ensuring material strength and hardness. In this invention, C primarily enhances the strength of steel plates through solid solution strengthening and precipitation strengthening. When added in combination with Mo, it forms a hard phase, Mo2C3, within the grains, enhancing the steel's hardness and wear resistance. However, excessive C can degrade the steel's plasticity and formability. In this invention, the C content is limited to 0.083% to 0.103%.

[0014] Si: One of the key elements for improving corrosion resistance, strength, and hardness. Si easily accumulates on the surface of steel sheets, forming a dense, matrix-bound SiO2 protective oxide film on the product surface that effectively inhibits the penetration of corrosive media. When added in combination with Mo, it reacts with free Mo in the steel to form Mo2Si3 hard-phase particles. By controlling the finishing and coiling temperatures, micron-sized (40-70 μm) hard-phase Mo2Si3 particles can be dispersed and precipitated near grain boundaries or within grains, effectively improving the steel's hardness and wear resistance. However, excessive Si content not only negatively impacts surface quality but also degrades steel performance by forming large Mo2Si3 particles. Therefore, the present invention limits the Si content to 0.41% to 0.59%. Furthermore, the Si and Mo contents determine the Si-Mo type and the state of the precipitated particles. To obtain more dispersed precipitated particles, the Si / Mo ratio is controlled within a range of 1.1 to 2.6.

[0015] Mn: One of the primary strengthening elements in steel, it increases the strength of steel plates through solid solution strengthening. Furthermore, as a key austenitizing stabilizing element, Mn in this invention expands the austenite phase, enhancing the stability of retained austenite in the steel and improving the material's plasticity. Therefore, to ensure and improve the material's strength and plasticity, the Mn content in this invention is set at 0.98% to 1.19%.

[0016] P: It is one of the elements that significantly improves the strength and corrosion resistance of materials. However, when the content of this element is too high, it is easy to segregate at the grain boundaries, which will not only reduce the plasticity and toughness of the material, but also affect the corrosion resistance of the material. Therefore, in the present invention, it is added in combination with the rare earth element Ce. The solid-solubilized rare earth element can refine the dendrites, increase the equiaxed crystal ratio, and thus inhibit the segregation behavior of P, and can also significantly improve the corrosion resistance of the material. In order to achieve a significant corrosion resistance effect in the present invention, the P content is set to 0.092% to 0.106%. In order to reduce the segregation of the P element in the ingot, the P / Ce value is limited to 6.3 to 6.5.

[0017] S: A harmful impurity element in steel, S easily forms defects such as segregation and inclusions, which can deteriorate the impact toughness and hot workability of the steel plate. However, controlling the S content too low increases smelting costs. Therefore, in the present invention, the S content should be controlled below 0.006%.

[0018] Cr: It mainly improves the strength of steel by solid solution strengthening. At the same time, this element is the main corrosion-resistant element and is often enriched in the rust layer. It not only easily forms a dense oxide film on the surface of the steel plate, but also forms a dense Cr-Cu compound protective rust layer on the surface of the substrate with the Cu element, which can significantly inhibit the penetration of corrosive media, thereby achieving a double-layer corrosion resistance effect and can replace part of the corrosion resistance of Cu. However, when its content is too high, it will not only deteriorate the welding performance of the steel plate but also increase the difficulty of smelting. Therefore, the Cr content in the present invention is controlled to be 0.62% to 0.86%.

[0019] Cu: One of the important corrosion-resistant elements. This element is often enriched in the rust layer, which can effectively improve the permeability of the corrosive medium, and it is easy to form a dense Cu-P compound protective rust layer with the P element on the surface of the substrate, which can further inhibit the penetration of the corrosive medium. At the same time, this element is often dissolved in Fe to form a substitutional solid solution, which has a solid solution strengthening effect, thereby improving the strength of the steel plate. However, when the Cu content is too high, it not only increases the cost, but also easily causes "copper brittleness" defects on the edge of the steel plate in the absence of Ni elements. Therefore, in the present invention, the rare earth Ce element is added to make it dispersed and combined with a heating process to avoid the occurrence of "copper brittleness" defects. The present invention limits its content range to 0.18% to 0.26%.

[0020] Ti: A strong carbon and nitrogen compound former, it's a key element in improving strength. During steel plate heating, it often forms Ti-N compounds with nitrogen, inhibiting austenite grain growth and achieving grain refinement. It also forms fine carbides and nitrides or carbonitrides with carbon and nitrogen, which then precipitate fine compounds during cooling and coiling, contributing to precipitation strengthening. The present invention limits the Ti content to 0.048% to 0.063%.

[0021] Sb: An effective element for improving the corrosion resistance and wear resistance of steel plates. This element easily forms a dense oxide film on the surface of the substrate, improving the passivation ability of the steel plate. By adding it in combination with P, Cu, and Cr, it synergistically concentrates in the rust layer, forming a dense Sb-P-Cu-Cr composite protective rust layer that is tightly bonded to the substrate, further hindering the intrusion of corrosive media. In addition, the Sb3O4 hard phase formed by this element inside the substrate precipitates along the grain boundaries during cooling and coiling, further improving the wear resistance of the steel plate. The Sb content in the present invention is controlled to be 0.098% to 0.117%.

[0022] Mo: There are three main forms of existence in steel. One part dissolves in iron to form a substitutional solid solution, which improves the yield strength of the steel; one part forms a Mo-C hard phase Mo2C3 with the free C in the steel, which can significantly improve the hardness and wear resistance of the steel; and a small part segregates at the grain boundaries; when Mo is added in combination with the rare earth Ce, the strong affinity of Ce can reduce the segregation of Mo at the grain boundaries. Ce promotes the uniform precipitation of the Mo2C3 hard phase and inhibits its aggregation and growth, which can further improve the wear resistance of the steel plate; especially when added in combination with Si, it can form Mo2Si3 hard phase particles with the free Si in the steel. By controlling the final rolling temperature and the coiling temperature, micron-sized (40-70μm) hard phase Mo2Si3 particles will be dispersed and precipitated near the grain boundaries or inside the grains, greatly improving the hardness and wear resistance of the steel. In order to better exert the synergistic wear-resistant effect of Si and Mo, the present invention limits the Si / Mo ratio to 1.1-2.6. However, when the Mo content is too high, the degree of segregation at the grain boundary will increase, and the plasticity, toughness and welding performance of the steel will be deteriorated. The Mo content of the present invention is controlled at 0.23%-0.35%.

[0023] Als: An important deoxidizing element, it purifies the molten steel into a low-oxygen environment. This prevents the rare earth from reacting with excess oxygen in the steel, allowing the rare earth to fully utilize its solid solution properties. This element's primary function is to complement the addition of rare earth. The present invention limits its content to 0.048% to 0.068%.

[0024] Ce: (1) As an effective deoxidizing and desulfurizing element, it can purify the molten steel and improve the mechanical properties of the product; it can change the shape and type of inclusions, reduce the potential difference between the inclusions and the matrix, reduce the tendency of electrochemical corrosion caused by inclusions, and effectively improve the corrosion resistance of the steel plate; (2) It has the function of dispersing Cu, which can avoid the occurrence 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 the steel plate; (3) The addition of Ce can effectively inhibit P segregation, thereby improving the plasticity of the material, especially in the case of high P in the present invention. In order to achieve a significant corrosion resistance effect and inhibit P segregation, the present invention limits the P / Ce value to 6.3-6.5; (4) It improves the segregation of Mo, promotes the uniform precipitation of the hard phases Mo2C3 and Mo2Si3, and inhibits the aggregation and growth of these phases, thereby improving the wear resistance of the steel plate. The present invention limits the range to 0.0144% to 0.0164%.

[0025] The present invention also provides a method for manufacturing 690MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets. The method obtains wear-resistant and atmospheric corrosion-resistant steel containing the above-mentioned chemical components through pre-desulfurization of molten iron, top and bottom blowing of converter, LF refining outside the furnace, slab continuous casting, billet heating, hot rolling, laminar cooling and coiling, and specifically includes the following contents.

[0026] Smelting: First, the molten iron is subjected to a desulfurization pretreatment so that the S content in the desulfurized molten iron is ≤0.002%. A top and bottom composite blowing process is adopted, and the converter tapping temperature is 1651-1666°C. The molten iron is then fed into an LF furnace for heating and composition fine-tuning, and then subjected to Si-Ca wire feeding treatment to further reduce the O and S contents, ensuring that the free O content in the steel is controlled below 3.8ppm. 7-9 minutes before the end of the vacuum treatment in the LF furnace, 1.60-1.82 kg / ton of steel of 20% Ce-Fe rare earth alloy is added to the LF furnace, and then argon weak blowing (argon flow rate 108-128 NL / min, pressure 0.16-0.29 MPa) is carried out with stirring for 3.9-5.9 minutes to ensure that the inclusions are fully floated and denatured.

[0027] Slab continuous casting: Molten slag is used throughout the slab continuous casting process to protect the molten steel and prevent it from being exposed to air. The thickness of the continuous casting slab is 210-230mm. Because the rare earth element Ce in the invention 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 1.28-1.48m / min. Furthermore, the high P content in the invention steel is prone to P segregation, which reduces the plasticity and toughness of the material. Therefore, to reduce centerline segregation of the continuous casting slab, the superheat is controlled between 10-13°C during casting, and electromagnetic stirring technology is used, with an electromagnetic stirring current of 364-368A and a frequency of 5-7Hz.

[0028] Ingot Heating: One of the primary methods used in this invention to improve steel plate strength is microalloying solid solution strengthening, particularly when Si and Mo are added in combination. To ensure sufficient solid solution of these alloying elements, the ingot is heated to 1272-1298°C. The steel of this invention is copper-containing steel, and Cu and Ni are typically added in combination to suppress the occurrence of "copper brittleness." However, to reduce costs, this invention avoids this "copper brittleness" defect by devising a rational heating process rather than adding the precious metal Ni. Therefore, in order to avoid the occurrence of "copper brittleness" defects caused by the precipitation of low-melting-point element Cu on the surface of the steel plate, the heating furnace atmosphere is set to a reducing atmosphere with an air-fuel ratio between 1.6 and 2.0. When the heating temperature is below 1105°C, slow heating is required, and the heating rate is controlled at 6.6-8.7°C / min to ensure uniform temperature inside and outside the billet; when the temperature is above 1105°C, rapid heating is required, and the heating rate is controlled at 16.9-18.9°C / min. Since the longer the heating time, the more conducive it is for Cu to diffuse along the austenite grain boundaries, and the more likely it is to produce "copper brittleness" defects, the furnace time is controlled to be ≤210min, preferably 184-207min, of which the holding time in the soaking section is 36-51min.

[0029] Rolling: The steel is subjected to temperature-controlled rolling in two stages: roughing and finishing. Roughing utilizes high temperature and high reduction. The final roughing temperature is 1109-1141°C, and the cumulative reduction during the roughing stage is 82.3%-85.5%. This high cumulative reduction not only closes existing defects in the ingot but also increases deformation, creating more dislocations and thereby enhancing the material's strength through dislocation strengthening. The start temperature for finishing rolling is 1091-1119°C. To eliminate the negative effects of dislocation strengthening on plasticity during the roughing stage and ensure sufficient precipitation of the Mo2C3 and Mo2Si3 hard phases, a higher final rolling temperature is established, ranging from 938-954°C. To ensure the flatness and precision of the finished steel plate, the reduction during the final finishing pass is controlled between 15.2% and 16.1%. Throughout the rolling process, the target crown is maintained at 34-41μm.

[0030] After finishing rolling, laminar cooling is performed in a two-stage cooling method. In the first stage, the steel is cooled to 739-759°C (this temperature range belongs to the ferrite transformation region) at a cooling rate of 21-28°C / s, followed by air cooling for 8-10s. During this stage, sufficient soft ferrite structure is obtained and the Mo2C3 and Mo2Si3 phases are inoculated, making them easy to precipitate and grow, thereby ensuring the plasticity and wear resistance of the steel plate. Subsequently, the steel is cooled in the second stage at a cooling rate of 33-44°C / s to 587-607°C for coiling. During this stage, sufficient hard bainite is generated to ensure the strength performance of the product. This coiling temperature also has a good effect on refining the grains and inhibiting the coarsening of the Mo2C3 and Mo2Si3 precipitation phases.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] By precisely controlling the composition and microstructure ratio, the 1.5-4.0mm wear-resistant and corrosion-resistant steel coil for photovoltaic brackets produced using the above chemical composition and rolling process has a yield strength of >690MPa, a tensile strength of >780MPa, and an elongation of >29%, with qualified cold bending performance and excellent plasticity. By controlling the hard phase precipitates and their sizes, the surface hardness of the invented steel is 234-241HBW, and the wear rate relative to Q345B is 26.4%-27.1%. By rationally matching the corrosion-resistant elements, in a rapid corrosion evaluation test simulating a C4-grade atmospheric environment, the corrosion rate of the invented steel relative to Q345B is 28.62%-30.83%. The present invention overcomes the shortcomings of the existing technology, making the production of thin-gauge, high-strength wear-resistant and corrosion-resistant steel plates for photovoltaic brackets simple to manufacture, and not only having strong plasticity, but also excellent wear resistance and atmospheric corrosion resistance. This ensures that the photovoltaic bracket will not have defects such as cracks during bending and deformation, and is safe and durable when used in windy and sandy areas. DETAILED DESCRIPTION

[0033] It should be noted that, unless there is a conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other. The described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative work are within the scope of protection of the present invention.

[0034] The present invention is described in more detail below through examples.

[0035] The composition of the steel according to the present invention is shown in Table 1, the main process parameters for smelting and continuous casting of the steel according to the present invention are shown in Table 2, the heating process parameters of the steel according to the present invention are shown in Table 3, the rolling and coiling process parameters of the steel according to the present invention are shown in Table 4, the various properties of the steel according to the present invention are shown in Table 5, the microstructure of the steel according to the present invention is shown in Table 6, and the results of the circumferential immersion corrosion test of the steel according to the present invention are shown in Table 7.

[0036] Table 1 Composition of steel according to the present invention (wt%)

[0037]

[0038] Table 2 Main process parameters for steel smelting and continuous casting according to the embodiment of the present invention

[0039]

[0040] Table 3 Main process parameters for heating steel according to the present invention

[0041] Example Heating temperature / ℃ air-fuel ratio Slow heating rate / ℃ / min Rapid heating rate / ℃ / min Total heating time / t Soaking time / t 1 1272 1.6 6.6 16.9 184 36 2 1275 1.6 6.8 17.2 187 38 3 1279 1.7 7.1 17.5 190 40 4 1282 1.7 7.4 17.8 193 42 5 1286 1.8 7.7 18.1 196 44 6 1290 1.9 8.0 18.4 199 46 7 1294 2.0 8.3 18.7 203 48 8 1298 2.0 8.7 18.9 207 51

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

[0043]

[0044] Table 5 Test results of various performance indicators of the embodiment

[0045]

[0046] Table 6 Microstructure of steel according to the present invention

[0047]

[0048] As can be seen from Table 5, the yield strength of the example steels of the present invention is 721-733 MPa, which is above the design strength of 690 MPa. The tensile strength is between 788-808 MPa, the elongation is greater than 29%, and the cold bending performance is qualified. This shows that the strength of the example steels not only meets the design requirements but also has high plasticity. The hardness value of the example steels is between 234-241 HBW.

[0049] The wear resistance tests reported in Table 5 were conducted on a wet rubber wheel abrasive wear tester. Samples measuring 57.0 mm × 25.5 mm × 6.0 mm were processed in accordance with JB / T 7705-1995, Test Method for Abrasive Wear of Loose Abrasive Grains - Rubber Wheel Method. The test results show that the wear rate of the example steel relative to Q345B ranged from 26.4% to 27.1%, demonstrating the steel's high wear resistance.

[0050] The results in Table 6 show that the microstructure of the invention steel is composed of ferrite + bainite + a small amount of pearlite. The microstructure is uniform and fine, and fine Mo2Si3 hard phase is precipitated in the microstructure. Among them, the proportion of Mo2Si3 in the size range of 40 to 70 μm is 87.6 to 89.7%. This level of precipitate phase is beneficial to improving the wear resistance of the invention steel.

[0051] To simulate corrosion conditions in a C4 atmospheric environment, the invention steel was subjected to a 72-hour immersion rapid corrosion evaluation test according to the test method specified in TB / T 2375-1993. Table 7 compares the corrosion resistance of the invention steel and the reference steel. As can be seen from Table 7, the corrosion resistance of the invention steel is significantly superior to that of the reference steel Q345B.

[0052] Table 7 Comparison results of rapid corrosion test of steel according to the present invention and comparative steel

[0053]

[0054] It should be 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 replacement or modification that does not depart from the essence of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A 690MPa grade wear-resistant and corrosion-resistant steel for photovoltaic brackets, characterized in that: The chemical composition of steel is as follows by weight: C: 0.083% ~ 0.103%, Si: 0.41% ~ 0.59%, Mn: 0.98% ~ 1.19%, P: 0.092% ~ 0.106%, S: ≤ 0.006%, Cr: 0.62% ~ 0.86%, Cu: 0.18% ~ 0.26%, Sb: 0.098% ~ 0.117%, Ti: 0.048% ~ 0.063%, Mo: 0.23% ~ 0.35%, Ce: 0.0144% ~ 0.0164%, Als: The steel has a P / Ce ratio of 0.048% to 0.068%, of which P / Ce is controlled at 6.3~6.5, Si / Mo is controlled at 1.1~2.6, and the balance is Fe and inevitable impurities; the metallographic structure of the steel is ferrite + bainite + a small amount of pearlite, with the ferrite proportion of 26.9%~28.7%, the bainite proportion of 65.2%~66.3%, and the ferrite grain size grade ≥10.5; fine Mo2Si3 hard phase is precipitated in the structure, of which the Mo2Si3 size range of 40~70μm accounts for 87.6%~89.7%.

2. The 690MPa wear-resistant and corrosion-resistant steel for photovoltaic bracket according to claim 1, characterized in that: The yield strength of the steel is between 721~733MPa, the tensile strength is between 788~808MPa, and the elongation is greater than 29%; the surface hardness of the steel is 234~241HBW, and the wear rate relative to Q345B is 26.4%~27.1%.

3. The 690MPa wear-resistant and corrosion-resistant steel for photovoltaic bracket according to claim 1, characterized in that: In the rapid corrosion evaluation test under a simulated C4 atmospheric environment, the corrosion rate of steel was 0.959~1.033g / m 2 .h, the corrosion rate relative to Q345B is 28.62%~30.83%.

4. The 690MPa wear-resistant and corrosion-resistant steel for photovoltaic bracket according to claim 1, characterized in that: The thickness of the steel plate is 1.5 to 4.0 mm.

5. A method for manufacturing the 690 MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic brackets according to any one of claims 1 to 4, comprising smelting, slab continuous casting, slab heating, rolling, laminar cooling and coiling, characterized in that: The ingot is heated to 1272-1298℃, with an air-fuel ratio of 1.6-2.

0. When the heating temperature is below 1105℃, the heating rate is controlled at 6.6-8.7℃ / min; when the temperature is above 1105℃, the heating rate is controlled at 16.9-18.9℃ / min; the furnace time is controlled to be ≤210min; the rolling adopts two-stage controlled rolling of rough rolling and finishing rolling, the finishing rolling temperature of rough rolling is 1109-1141℃, the cumulative reduction rate of rough rolling stage is 82.3%-85.5%; finishing rolling The starting rolling temperature is 1091℃~1119℃, the finishing rolling temperature is 938~954℃, the reduction rate of the last finishing rolling is controlled at 15.2%~16.1%, and the rolling convexity target is controlled at 34~41µm; after finishing rolling, two-stage laminar cooling is adopted. In the first stage, the steel is cooled to 739~759℃ at a cooling rate of 21~28℃ / s, air-cooled for 8~10s, and then cooled in the second stage at a cooling rate of 33~44℃ / s, and cooled to 587~607℃ for coiling.

6. The method for manufacturing 690MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic supports according to claim 5, characterized in that: During smelting, the molten iron is first pre-treated with desulfurization. After desulfurization, the S in the molten iron is ≤0.002%. The top and bottom composite blowing process is adopted, and the converter tapping temperature is 1651~1666℃. After that, Si-Ca wire feeding treatment is carried out to control the free O content in the steel below 3.8ppm; 20% Ce-Fe rare earth alloy 1.60~1.82kg / ton steel is added to the LF furnace 7~9min before the end of the vacuum treatment in the LF furnace, and then argon weak blowing is carried out.

7. The method for manufacturing 690MPa wear-resistant and corrosion-resistant steel for photovoltaic brackets according to claim 6, characterized in that: The flow rate of argon weak blowing is 108~128NL / min, the pressure is 0.16~0.29MPa, and the weak blowing time is 3.9~5.9min.

8. The method for manufacturing 690MPa-grade wear-resistant and corrosion-resistant steel for photovoltaic supports according to claim 5, characterized in that: The heating time of the ingot in the furnace is 184 to 207 minutes, of which the holding time in the soaking section is 36 to 51 minutes.

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