Production method of 420 MPa grade photovoltaic support steel

Abstract

The invention relates to a production method of 420MPa grade photovoltaic support steel, which comprises the steps of converter treatment, LF refining, casting machine treatment, heating furnace treatment, hot continuous rolling, cold continuous rolling and the like, and the molten steel comprises the following components: 0.15-0.22% of C, 0.10-0.20% of Si, 0.4-0.6% of Mn, 0.055-0.080% of Ti, less than or equal to 0.025% of P, less than or equal to 0.020% of S, 0.020-0.040% of Als and the balance of Fe and inevitable impurities. Carbon, manganese and titanium are adopted for strengthening, it is guaranteed that after coating is conducted by a user, the yield strength is larger than or equal to 420 MPa, the tensile strength is larger than or equal to 530 MPa, the percentage elongation after fracture is larger than or equal to 20%, the strength meets the requirement, and the performance is stable; and the dimensional precision and the surface quality of the steel strip are effectively ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of steel material production, and specifically relates to a production method of steel for 420 MPa grade photovoltaic brackets. Background Art

[0002] ‌Under the background of "carbon neutrality", photovoltaic power generation, as a clean energy source, has been highly valued in China. In recent years, the photovoltaic industry has made rapid progress in technology, achieving relatively large breakthroughs and accelerating the development of China's photovoltaic industry. Photovoltaic brackets, known as the "bones" of photovoltaic power stations, are special structural components designed and installed in photovoltaic power generation systems to support, fix, and rotate photovoltaic modules. As an important support structure in the photovoltaic system, safety and installation convenience are its core requirements. Therefore, photovoltaic brackets have relatively high requirements for the strength and toughness of steel materials, ensuring both the firmness and reliability of the brackets and strong load-bearing capacity, as well as excellent processing performance.

[0003] Patent CN 117583387 A, titled "A Preparation Method of 1.5 mm Hot-Rolled High-Strength Weather-Resistant Steel for Photovoltaic Brackets", mainly introduces weather-resistant hot-rolled steel strips with a thickness of 1.5 mm, adding elements such as Cu: 0.25% - 0.45%, Cr: 0.75% - 1.00%. Different from the present invention, it is a steel material for user coating.

[0004] Patent CN 117701978 A, titled "A Production Method of Steel for 400 MPa Grade Photovoltaic Brackets", uses a relatively high Si: 0.06 - 0.5% in its composition. When the Si content is higher than 0.25%, it will cause the ζ phase of the iron-zinc alloy layer in the zinc layer to thicken violently, forming a gray coating and deteriorating the adhesion of the galvanized layer. Therefore, this invention is not suitable for coated products. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a production method of steel for 420 MPa grade photovoltaic brackets. The product is mainly strengthened by carbon, manganese, and titanium. After coating by users, the yield strength is greater than or equal to 420 MPa, the tensile strength is greater than or equal to 530 MPa, and the elongation after fracture is greater than or equal to 20%. The strength meets the requirements and the performance is stable, so as to solve the above problems.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a production method of steel for 420 MPa grade photovoltaic brackets, including the following steps: Step 1: Converter. First, smelt in the top-bottom combined blowing mode with low-carbon steel. Endpoint control: [C] ≥ 0.08%, [P] ≤ 0.020%, [S] ≤ 0.025%, endpoint temperature 1610 - 1680°C. Then, carry out deoxidation alloying. About 2 minutes after tapping, add ferrosilicon manganese alloy first and then aluminum cored wire for deoxidation. The target control range of [Alt] at the argon station is 0.010 - 0.050%; Step 2: LF refining. Control aluminum throughout the process to ensure [Als] ≥ 0.010% throughout. Feed aluminum according to the aluminum content in the steel. Feed enough aluminum at one time to avoid feeding aluminum in the middle and later stages. The feeding amount of calcium wire is 150 - 400 m / furnace. Deoxidation must be complete before feeding the calcium wire to ensure the calcium content in the steel. Take a sample 3 minutes after the wire feeding is completed. The soft stirring time ≥ 8 minutes. The soft stirring effect is based on the slight fluctuation of the slag surface without exposing the molten steel surface. The ladle tapping temperature: 1556 - 1571°C; Step 3: Caster. The tundish temperature is 1525 - 1545°C. Pouring starts when the tundish steel is more than 25 tons. During the pouring process, the tundish molten steel shall not be less than 25 tons. The casting speed remains constant during the pouring process. The normal casting speed control range is 0.8 - 1.4 m / min. Protect throughout the above production process to ensure good argon sealing of the long nozzle, good sealing of the submerged nozzle, and good centering of the submerged nozzle. Use covering agent and low-carbon steel protective slag in the tundish and mold respectively to isolate the molten steel from contact with air. The cross-sectional specifications of the cast slab produced are 230 mm thick * 800 - 1630 mm wide.

[0007] Step 4: The heating furnace temperature is 1240~1280°C, and the residence time in the furnace is greater than 130 min; Step 5: Hot continuous rolling. Adopt 2 roughing stands + 7 stands of continuous rolling. The roughing finishing rolling temperature is 1040~1080°C, the finishing rolling temperature of the finishing mill is 860 - 900°C, and the coiling temperature is 580 - 610°C. Vertical rolls must be used in roughing to control the width and edge quality of the intermediate slab. Insulation covers should be used for all rolling specifications to avoid excessive temperature difference between the head and tail of the strip; Step 6: Cold continuous rolling. Adopt pickling + 5 stands of cold continuous rolling, with a reduction rate of 40% - 60%. The surface roughness range of the plate is Ra: 0.2~0.6 μm.

[0008] Preferably, the composition of the molten steel is as follows: C: 0.15% - 0.22%, Si: 0.10% - 0.20%, Mn: 0.4% - 0.6%, Ti: 0.055 - 0.080%, P ≤ 0.025%, S ≤ 0.020%, Als: 0.020% - 0.040%, and the rest is Fe and inevitable impurities. Carbon atoms play an interstitial solid solution strengthening role, which is the most economical and effective strengthening method in steel. As the carbon content in steel increases, the yield strength and tensile strength increase, but the plasticity will be lower. Manganese mainly exists in a solid solution state in steel. Roughly, every 1% of solid solution manganese (mass fraction) can produce a strength increment of 40 - 60 MPa. At the same time, manganese can lower the Ar1 temperature of steel, making the ferrite after γ-α phase transformation significantly refined. Grain refinement can not only increase the yield strength of steel but also lower the plastic-brittle transition temperature, which is beneficial to improving the toughness of steel. Titanium has a high precipitation and a certain grain refinement strengthening effect. Titanium has a strong affinity with carbon, nitrogen, and oxygen in steel, forming stable carbides and nitrides. At high temperatures, TiN precipitates, hindering the growth of austenite grains and playing a grain refinement strengthening role; at low temperatures, fine and dispersed TiC particles precipitate, playing a precipitation strengthening role and increasing the strength.

[0009] The beneficial effects of the present invention are as follows: Through the strengthening of carbon, manganese, and titanium elements and an appropriate reduction ratio, after being coated by users, high-strength photovoltaic steel with a yield strength of ≥420 MPa, a tensile strength of ≥530 MPa, and an elongation after fracture A80 ≥ 20% can be produced. The strength meets the requirements and the performance is stable; By using hot tandem rolling and cold tandem rolling, a fine heating system, reasonable rough rolling finishing temperature, finishing rolling temperature, and coiling temperature, and a reasonable reduction ratio, the dimensional accuracy and surface quality of the steel strip are effectively guaranteed. Specific Embodiments

[0010] The present invention will be further described in detail below in conjunction with specific embodiments: Example 1 Produce with a thickness of 1.9 mm and a width of 1250 mm.

[0011] (1) Converter end-point control: [C]: 0.08%, [P]: 0.015%, [S]: 0.020%, end-point temperature 1650 °C; [Alt] at the argon station: 0.030%.

[0012] (2) Throughout the LF refining process, [Als]: 0.025%; the feeding amount of calcium wire is 200 m / furnace, the soft stirring time is 10 min, and the ladle tapping temperature is 1560 °C.

[0013] (3) The tundish temperature is 1530 °C, the weight of the tundish molten steel is 28 tons, and the constant casting speed is 1.2 m / min.

[0014] (4)The soaking temperature of the reheating furnace is 1250 °C, and the residence time in the furnace is 150 min.

[0015] (5)The finishing rolling temperature of rough rolling in hot continuous rolling is 1060 °C, the finishing rolling temperature of finishing rolling is 880 °C, and the coiling temperature is 600 °C.

[0016] (6)The reduction rate of cold continuous rolling is 52%, and the surface roughness Ra of the plate surface is 0.5 μm.

[0017] (7)The chemical composition of the molten steel is C: 0.18%, Si: 0.14%, Mn: 0.54%, Ti: 0.063%, P: 0.017%, S: 0.010%, Als: 0.025%, and the rest is Fe and inevitable impurities.

[0018] Example 2 The produced thickness is 2.4 mm and the width is 1250 mm.

[0019] (1)Converter end-point control: [C]: 0.06%, [P]: 0.016%, [S]: 0.018%, end-point temperature 1660 °C; [Alt] at the argon station: 0.040%.

[0020] (2)The whole process of LF refining: [Als]: 0.020%; the feeding amount of calcium wire is 260 m / furnace, the soft stirring time is 12 min, and the tapping temperature of the ladle is 1575 °C.

[0021] (3)The tundish temperature is 1550 °C, the weight of the tundish molten steel is 26 tons, and the constant casting speed is 1.3 m / min.

[0022] (4)The soaking temperature of the reheating furnace is 1260 °C, and the residence time in the furnace is 1450 min.

[0023] (5)The finishing rolling temperature of rough rolling in hot continuous rolling is 1070 °C, the finishing rolling temperature of finishing rolling is 890 °C, and the coiling temperature is 610 °C.

[0024] (6)The reduction rate of cold continuous rolling is 42%, and the surface roughness Ra of the plate surface is 0.5 μm.

[0025] (7)The chemical composition of the molten steel is C: 0.19%, Si: 0.15%, Mn: 0.56%, Ti: 0.065%, P: 0.015%, S: 0.008%, Als: 0.030%, and the rest is Fe and inevitable impurities.

[0026] Example 3 The produced thickness is 2.2 mm and the width is 1250 mm.

[0027] (1)Converter end-point control: [C]: 0.07%, [P]: 0.016%, [S]: 0.017%, end-point temperature 1670 °C; [Alt] at the argon station: 0.035%.

[0028] (2) [Als] throughout the LF refining process: 0.023%; the feeding amount of calcium wire is 200 m / furnace, the soft stirring time is 16 min, and the ladle tapping temperature is 1560 °C.

[0029] (3) The tundish temperature is 1530 °C, the weight of tundish molten steel is 27 tons, and the constant casting speed is 1.2 m / min.

[0030] (4) The soaking temperature of the heating furnace is 1260 °C, and the residence time in the furnace is 160 min.

[0031] (5) The finishing rolling temperature of rough rolling in hot continuous rolling is 1070 °C, the finishing rolling temperature of finishing rolling is 890 °C, and the coiling temperature is 610 °C.

[0032] (6) The reduction ratio of cold continuous rolling is 44%, and the surface roughness Ra of the sheet surface is 0.6 μm.

[0033] (7) The chemical composition of the molten steel: C: 0.20%, Si: 0.19%, Mn: 0.60%, Ti: 0.073%, P: 0.015%, S: 0.007%, Als: 0.036%, and the rest are Fe and inevitable impurities.

[0034] Through the strengthening of carbon, manganese, and titanium elements and the appropriate reduction ratio, after being coated by the user, high-strength steel for photovoltaic applications with a yield strength of ≥420 MPa, a tensile strength of ≥530 MPa, and an elongation after fracture A80 ≥ 20% can be produced, with the strength meeting the requirements and stable performance; the use of hot continuous rolling, cold continuous rolling, a fine heating system, reasonable finishing rolling temperatures of rough rolling and finishing rolling, coiling temperature, reasonable reduction ratio effectively ensures the dimensional accuracy and surface quality of the steel strip.

[0035] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for producing 420MPa grade photovoltaic support steel, characterized in that: The following steps are involved: Step 1: Converter, first use the top and bottom blowing combined blowing mode of low carbon steel for smelting, the end point control: [C] ≧ 0.08%, [P] ≤ 0.020%, [S] ≤ 0.025%, the end point temperature is 1610-1680℃, and then deoxidation and alloying are carried out. About 2 minutes after steel is tapped, silicon manganese alloy is first added and then steel core aluminum is added for deoxidation. The target control range of [Alt] of the argon station is 0.010-0.050%; Step 2: LF refining, using full-process aluminum control to ensure that [Als] is ≥ 0.010% throughout the process. Aluminum feeding is performed according to the aluminum content in the steel. Aluminum is fed enough at one time to avoid feeding aluminum in the middle and late stages. The calcium wire feeding amount is 150-400m / furnace. Deoxidation must be complete before feeding the calcium wire to ensure the calcium content in the steel. Samples are taken 3 minutes after the feeding line is completed. The soft stirring time is ≥ 8 minutes. The soft stirring effect is based on the slag surface slightly fluctuating without revealing the steel liquid surface. The ladle outlet temperature is: 1556-1571℃; Step 3: Casting machine, tundish temperature 1525-1545℃, pouring of more than 25 tons of steel in the tundish, the molten steel in the tundish shall not be less than 25 tons during the pouring process, the casting speed is kept constant during the casting process, and the normal casting speed control range is 0.8-1.4m / min. The above production is fully protected to ensure that the long nozzle is well sealed with argon, the submerged nozzle is well sealed, and the submerged nozzle is well aligned. Covering agent and low-carbon steel protective slag are used in the tundish and the crystallizer respectively to keep the molten steel isolated from the air. The cross-sectional specifications of the cast billet produced above are 230mm thick and 800-1630mm wide; Step 4: The heating furnace temperature is 1240~1280℃, and the time in the furnace is greater than 130min; Step 5: Hot rolling, using 2 rough rolling + 7 stand continuous rolling, rough rolling final rolling temperature 1040 ~ 1080 ℃, finishing rolling final rolling temperature 860-900 ℃, coiling temperature 580-610 ℃, rough rolling must be put into vertical roller to control the width and edge quality of the intermediate billet, and all specifications must be rolled with a heat preservation cover to avoid excessive temperature difference between the head and tail of the strip; Step 6: Cold rolling, using pickling + 5-stand cold rolling, with a reduction rate of 40%-60%, and a plate surface roughness range of Ra: 0.2~0.6μm.

2. The method for producing 420MPa grade photovoltaic support steel according to claim 1, characterized in that: The composition of the molten steel is: C: 0.15%-0.22%, Si: 0.10%-0.20%, Mn: 0.4%-0.6%, Ti: 0.055-0.080%, P≤0.025%, S≤0.020%, Als: 0.020%-0.040%, and the rest is Fe and unavoidable impurities.