Production method of zinc-aluminum-magnesium-plated high-strength steel strip with yield strength of 390 MPa for completely-annealed and low-cost photovoltaic support

Abstract

The invention discloses a production method of a zinc-aluminum-magnesium-plated high-strength steel strip with the yield strength of 390 MPa for a completely-annealed and low-cost photovoltaic support. The production method comprises the steps of smelting, continuous casting, molten iron pretreatment, converter treatment, LF refining, RH refining and slab continuous casting. Wherein the molten steel for the casting machine comprises the following chemical components in percentage by mass: 0.08 to 0.25 percent of C, less than or equal to 0.08 percent of Si, 0.40 to 1.20 percent of Mn, less than or equal to 0.025 percent of P, less than or equal to 0.020 percent of S, 0.015 to 0.050 percent of Alt, 0.020 to 0.080 percent of Ti, 0.0005 to 0.0030 percent of Ca and the balance of iron and impurities; a hot rolling production process; pickling and cold rolling; and carrying out continuous hot galvanizing and finishing processes. The zinc-aluminum-magnesium-plated high-strength structural steel strip with the yield strength of 390 MPa has the characteristics of high strength, good bending performance, high corrosion resistance, relatively low alloy cost and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgical plates, and in particular relates to a method for producing a fully annealed, low-cost 390MPa-grade galvanized aluminum-magnesium high-strength steel strip for a photovoltaic bracket. Background Art

[0002] Galvanized aluminum-magnesium products are a new type of coated steel material with super corrosion resistance, wear resistance and coating resistance. They are mainly used in industries or fields such as automobiles, home appliances, photovoltaics, animal husbandry, highway guardrails, and metallurgical cable trays. Its corrosion resistance is 10 to 20 times higher than that of conventional galvanized products. The cut after shearing has an automatic sealing function, and the anti-powdering performance of the coating greatly reduces the damage to the processing mold and reduces the user's material cost. It can replace ordinary galvanized sheets, color steel, stainless steel, aluminum sheets and other materials. It is currently a popular direction for production and research and development in the same industry at home and abroad.

[0003] The 390MPa yield strength zinc-aluminum-magnesium high-strength structural steel can be used in harsh external environments while having a high strength level. It has the characteristics of weight reduction, material saving, high corrosion resistance, and environmental protection. It is mainly used in the new energy industry to manufacture photovoltaic brackets. As an important part of the photovoltaic power generation system, photovoltaic brackets have an important impact on the stability and efficiency of photovoltaic power generation. In the field of photovoltaic brackets, the application of zinc-aluminum-magnesium coating products is bringing new developments and advantages.

[0004] At present, the galvanized sheet S390GD+Z product for European standard export structural steel developed by Handan Iron and Steel (Journal name: Gansu Metallurgy, Vol. 36, No. 1, February 2014, "Development of galvanized sheet S390GD+Z for European standard export structural steel of Handan Iron and Steel") is the same as the product of the present invention, which is a structural steel with a yield strength of 390MPa. Its main strengthening methods are carbon and manganese solid solution strengthening and deformation strengthening. It is speculated that a low-carbon, high-manganese, incomplete annealing design is adopted (the chemical composition is not given, and it is speculated through microstructure, performance and process). The product of the present invention adopts medium carbon (0.08-0.25%), an appropriate amount of manganese (0.40-1.20%), a relatively economical titanium microalloying (0.020-0.080%), and a complete annealing design. The alloy cost of the product of the present invention is lower than that of the above-mentioned products.

[0005] The hot-dip galvanized S390GD (S450GD) + Z product for photovoltaic brackets developed by Handan Iron and Steel (Journal Name: Steel Rolling, Volume 38, No. 3, June 2021, "Development of Hot-dip Galvanized S390GD (S450GD) + Z Products for Photovoltaic Brackets of Handan Iron and Steel") has the same use and strength level as the product of the present invention. This product is a heat-based hot-dip galvanized product. The chemical composition adopts a low-carbon and high-manganese design, which is different from the chemical composition and process of the product of the present invention.

[0006] The S450GD+Z product of continuous galvanized steel strip for cold-based photovoltaic brackets developed by Tangshan Iron and Steel Company of Hebei Iron and Steel Group (Journal name: Hebei Metallurgy, Issue 325, Issue 1, 2023 "Development of Continuous Galvanized Steel Strip S450GD+Z for Photovoltaic Brackets") has the same use as the product of the present invention, but the strength level is different. Tangshan Iron and Steel's products mainly use low carbon, appropriate amount of manganese solid solution strengthening, niobium microalloy precipitation strengthening and deformation strengthening, which are different from the chemical composition and process of the product of the present invention, and the alloy cost is higher than the product of the present invention. Summary of the invention

[0007] The purpose of the present invention is to provide a method for producing a fully annealed, low-cost 390MPa grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets. The 390MPa grade galvanized aluminum-magnesium high-strength structural steel strip has the characteristics of high strength, good bending performance, strong corrosion resistance, and relatively low alloy cost, which meets the photovoltaic industry's requirements for high strength, high corrosion resistance, and low cost for photovoltaic bracket steel. Mechanical properties meet: Yield strength R eH :≥390MPa, tensile strength R m :≥460MPa, elongation A 80mm ≥16%.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0009] The present invention discloses a method for producing a fully annealed, low-cost 390 MPa-grade galvanized aluminum-magnesium high-strength steel strip for a photovoltaic support, comprising:

[0010] (1) Smelting-continuous casting production process: molten iron pretreatment-converter-LF refining-RH refining-slab continuous casting; oxygen blowing and decarburization are carried out in the converter top and bottom combined blowing smelting to raise the temperature; aluminum iron, manganese iron and other alloys are added during the converter steelmaking process for deoxidation and alloying, and the P and S components are controlled to prevent overoxidation of the molten steel. The steelmaking temperature is ≥1620℃; LF refining outside the furnace adopts the LF full-process argon blowing process, and aluminum iron, silicon iron, manganese iron and other alloys are added to adjust the composition to the target range; the RH process is vacuum degassing, and titanium iron and other alloys are added to adjust the composition into the target range; the chemical composition of the molten steel supplied to the casting machine is C: 0.08-0.25%, Si≤0.08%, Mn: 0.40-1.20%, P≤0.025%, S≤0.020%, Alt: 0.015-0.050%, Ti: 0.020-0.080%, Ca: 0.0005-0.0030%, and the rest is Fe and impurities; the above-mentioned slab continuous casting superheat is 25-40°C, and the pulling speed is controlled at 1.0-1.8m / min;

[0011] (2) Hot rolling production process: heating of ingot - rough rolling - finishing rolling - coiling; the ingot out-of-furnace temperature is 1220-1280°C, rough rolling is carried out by a 3+3 mode 2-stand rolling mill, finishing rolling is carried out by a 7-stand rolling mill, the finishing rolling temperature is 860-920°C, and the thickness of the hot rolled steel strip is 2.5-5.0 mm; cooling is carried out by laminar cooling equipment, and the coiling temperature is 550-640°C;

[0012] (3) Pickling and cold rolling process: After the hot-rolled steel strip is pickled to remove the surface iron oxide scale, it is cold-rolled on a 5-stand cold rolling mill with a cold rolling reduction rate of 50-72% and a finished product thickness of 0.7-2.5 mm;

[0013] (4) Continuous hot-dip galvanizing and skin-passing process: The cold-hardened steel strip is unrolled and welded for continuous production, with a furnace speed of 60-130 m / min, a uniform heating temperature of 690-760°C, slow cooling to 610-670°C, and then cooling to 410-480°C. The temperature of the zinc pot is 400-470°C, the skin-passing elongation is 0.50-1.00%, and the tensile elongation is ≤0.40%.

[0014] Furthermore, the chemical composition of the steel strip in mass percentage is: C: 0.16%, Si: 0.07%, Mn: 0.63%, P: 0.014%, S: 0.003%, Alt: 0.035%, Ti: 0.064%, Ca: 0.0014%, and the rest is Fe and impurities.

[0015] Furthermore, the chemical composition of the steel strip in mass percentage is: C: 0.17%, Si: 0.05%, Mn: 0.63%, P: 0.017%, S: 0.005%, Alt: 0.031%, Ti: 0.060%, Ca: 0.0016%, and the rest is Fe and impurities.

[0016] Furthermore, the mechanical properties meet the following requirements: yield strength R eH :≥390MPa, tensile strength R m :≥460MPa, elongation A 80mm ≥16%.

[0017] Furthermore, the mechanical properties meet the following requirements: yield strength R eH : 514-561MPa, tensile strength R m : 583-625MPa, elongation A 80mm :17.8-22.0%.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are:

[0019] The product of the present invention has the characteristics of high strength, good bending performance, strong corrosion resistance, relatively low alloy cost, etc., which meets the material selection requirements of photovoltaic products for trial use in most natural environments in my country. Mechanical properties meet: yield strength R eH :≥390MPa, tensile strength R m :≥460MPa, elongation A 80mm ≥16%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below in conjunction with the accompanying drawings.

[0021] Figure 1 The microstructure diagram of the embodiment of the present invention. DETAILED DESCRIPTION

[0022] The present invention is described in detail below through specific examples. The examples are only intended to help understand the present invention but are not intended to limit the present invention.

[0023] According to the above steelmaking production process requirements, the actual slab chemical composition is shown in Table 1.

[0024] Table 1 Chemical composition of the present invention (wt%)

[0025]

[0026]

[0027] According to the above hot rolling process requirements, the actual process is shown in Table 2.

[0028] Table 2 Hot rolling process of the embodiment of the present invention

[0029] Serial number Oven temperature / ℃ Finish rolling temperature / ℃ Coiling temperature / ℃ Require 1220-1280 860-920 550-640 Example 1.1 1242 886 568 Example 1.2 1240 887 569 Example 1.3 1243 887 569 Example 2.1 1243 887 570 Example 2.2 1242 888 569 Example 2.3 1240 888 570

[0030] According to the above cold rolling, hot dip galvanizing and skin-passing process requirements, the actual hot dip galvanizing and skin-passing process is shown in Table 3.

[0031] Table 3 Hot-dip galvanizing and skin-passing process of the embodiment of the present invention

[0032]

[0033] The mechanical properties of the steel strip according to the embodiment of the present invention were tested, and the test results are shown in Table 4.

[0034] Table 4 Mechanical properties of the steel strip in the embodiment of the present invention

[0035] Example <![CDATA[Yield strength R eL / MPa]]> <![CDATA[Tensile strength R m / MPa]]> <![CDATA[Elongation A 80 / %]]> Require ≥390 ≥460 ≥16 Example 1.1 561 625 19.0 Example 1.2 514 583 17.8 Example 1.3 560 624 20.9 Example 2.1 534 603 22.0 Example 2.2 548 609 19.5 Example 2.3 531 597 21.2

[0036] From the data in Table 4, it can be seen that the mechanical properties of the fully annealed, low-alloyed, low-cost photovoltaic bracket with a yield strength of 390MPa grade galvanized aluminum-magnesium high-strength structural steel strip of the present invention are as follows: yield strength R eH : 514-561MPa, tensile strength R m : 583-625MPa, elongation A 80mm : 17.8-22.0%. The steel strip product obtained by the above process has been used by users and has suitable performance and can be promoted for use.

[0037] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for producing a fully annealed, low-cost 390MPa grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets, characterized in that: include: (1) Smelting-continuous casting production process: molten iron pretreatment-converter-LF refining-RH refining-slab continuous casting; In the converter top and bottom combined blowing smelting, oxygen blowing, decarburization and heating are carried out, and aluminum iron, manganese iron and the like are added in the converter tapping process for deoxidation and alloying, and the P and S components are controlled to prevent the molten steel from being overoxidized, and the tapping temperature is ≥1620°C; the LF out-of-furnace refining adopts the LF full-process argon blowing process, and aluminum iron, silicon iron, manganese iron and other alloys are added to adjust the composition to the target range; the RH process is vacuum degassing, and titanium iron and other alloys are added to adjust the composition to the target range; the chemical composition of the molten steel for the casting machine is C: 0.08-0.25%, Si≤0.08%, Mn: 0.40-1.20%, P≤0.025%, S≤0.020%, Alt: 0.015-0.050%, Ti: 0.020-0.080%, Ca: 0.0005-0.0030%, and the rest is Fe and impurities; the above-mentioned slab continuous casting superheat is 25-40°C, and the pulling speed is controlled at 1.0-1.8m / min; (2) Hot rolling production process: heating of ingot - rough rolling - finishing rolling - coiling; the ingot out-of-furnace temperature is 1220-1280°C, rough rolling is carried out by a 3+3 mode 2-stand rolling mill, finishing rolling is carried out by a 7-stand rolling mill, the finishing rolling temperature is 860-920°C, and the thickness of the hot rolled steel strip is 2.5-5.0 mm; cooling is carried out by laminar cooling equipment, and the coiling temperature is 550-640°C; (3) Pickling and cold rolling process: After the hot-rolled steel strip is pickled to remove the surface iron oxide scale, it is cold-rolled on a 5-stand cold rolling mill with a cold rolling reduction rate of 50-72% and a finished product thickness of 0.7-2.5 mm; (4) Continuous hot-dip galvanizing and skin-passing process: The cold-hardened steel strip is unrolled and welded for continuous production, with a furnace speed of 60-130 m / min, a uniform heating temperature of 690-760°C, slow cooling to 610-670°C, and then cooling to 410-480°C. The temperature of the zinc pot is 400-470°C, the skin-passing elongation is 0.50-1.00%, and the tensile elongation is ≤0.40%.

2. The method for producing a fully annealed, low-cost 390MPa grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets according to claim 1, characterized in that: The chemical composition of the steel strip in mass percentage is: C: 0.16%, Si: 0.07%, Mn: 0.63%, P: 0.014%, S: 0.003%, Alt: 0.035%, Ti: 0.064%, Ca: 0.0014%, and the rest is Fe and impurities.

3. The method for producing a fully annealed, low-cost 390MPa grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets according to claim 1, characterized in that: The chemical composition of the steel strip by mass percentage is: C: 0.17%, Si: 0.05%, Mn: 0.63%, P: 0.017%, S: 0.005%, Alt: 0.031%, Ti: 0.060%, Ca: 0.0016%, and the rest are Fe and impurities.

4. The method for producing a fully annealed, low-cost 390MPa-grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets according to claim 1, characterized in that: Mechanical properties meet: yield strength R eH :≥390MPa, tensile strength R m :≥460MPa, elongation A 80mm ≥16%.

5. The method for producing a fully annealed, low-cost 390MPa-grade galvanized aluminum-magnesium high-strength steel strip for photovoltaic brackets according to claim 1, characterized in that: Mechanical properties meet: yield strength R eH : 514-561MPa, tensile strength R m : 583-625MPa, elongation A 80mm :17.8-22.0%.

Images