Zinc-aluminum-magnesium coated steel plate for photovoltaic bracket and preparation method of zinc-aluminum-magnesium coated steel plate

Abstract

The invention discloses a zinc-aluminum-magnesium coated steel plate for a photovoltaic support and a preparation method of the zinc-aluminum-magnesium coated steel plate, the zinc-aluminum-magnesium coated steel plate is prepared by smelting and casting raw material steel to prepare a plate blank, and the plate blank is subjected to hot rolling, acid pickling, leveling, degreasing cleaning, continuous annealing, hot dipping, finishing and withdrawal and straightening procedures to prepare the zinc-aluminum-magnesium coated steel plate. The steel plate is a hot-based hot-galvanized aluminum-magnesium alloy, is low in production cost, is more excellent in corrosion resistance compared with an existing galvanized product, not only conforms to the green and low-carbon development trend of the photovoltaic industry, but also is higher in product surface quality, coating adhesive force and ductility, and the comprehensive performance completely meets the requirements of steel for a photovoltaic bracket, so that the steel plate has a good application prospect. The zinc-aluminum-magnesium coated steel plate provided by the invention meets the urgent requirements of the photovoltaic industry on high-strength, high-corrosion-resistance and low-cost coated steel plates for photovoltaic brackets, and has a wide application prospect in the photovoltaic field.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip galvanized aluminum-magnesium steel plates, and in particular to a zinc-aluminum-magnesium coated steel plate for a photovoltaic support and a preparation method thereof. Background Art

[0002] Photovoltaic brackets are an important part of photovoltaic power stations. They are used to protect photovoltaic modules from damage such as light, corrosion and strong winds. Photovoltaic power stations are mostly built in open areas such as deserts, Gobi deserts, and tidal flats. The environment is relatively harsh and the bracket materials are easily corroded. Photovoltaic power stations usually have high requirements for the service life of photovoltaic bracket materials, which generally cannot be less than 25 years. The selection of photovoltaic bracket materials and their subsequent maintenance directly affect the safe operation and economy of photovoltaic modules. In view of the complex environment around photovoltaic power stations, high-strength, low-cost steel structure brackets are highly favored. In recent years, users have also put forward higher requirements for the surface quality, mechanical properties, corrosion resistance and deformation ductility of photovoltaic bracket materials.

[0003] Currently disclosed photovoltaic bracket production methods include: Patent Publication No. CN111041359A provides an economical hot-dip galvanized steel plate with excellent surface quality for photovoltaic brackets and its production method. Due to the use of hot-dip galvanized coating, the coating is prone to corrosion under relatively harsh environmental conditions, and the subsequent maintenance cost is relatively high. Patent Publication No. CN117127106A provides a 500MPa-grade hot-dip galvanized aluminum-magnesium steel plate for photovoltaic brackets and its manufacturing method. The substrate used is a cold-rolled plate, and the production cost is relatively high. Patent Publication No. CN2023112750 provides a weathering steel for photovoltaic brackets and its preparation method. It does not involve a hot-dip galvanizing process. Corrosion-resistant elements such as Ni, Cr, and Cu need to be added to the steel, and the production cost is relatively high.

[0004] At present, facing the development trend of green, low-carbon, high-strength and corrosion-resistant photovoltaic industry, it is an urgent need for the photovoltaic industry to develop a high-strength, high-corrosion-resistant and low-cost coated steel plate for photovoltaic brackets. Summary of the invention

[0005] In view of this, the present disclosure provides a zinc-aluminum-magnesium coated steel plate for photovoltaic brackets and a preparation method thereof, so as to solve the problems of high bracket production costs due to the relatively harsh working environment of current photovoltaic brackets, the easy corrosion of economical hot-dip galvanized steel plate brackets, and the use of cold-rolled plates as substrates.

[0006] To achieve the above-mentioned purpose of the invention, in a first aspect, a method for preparing a zinc-aluminum-magnesium coated steel sheet for a photovoltaic support comprises:

[0007] The raw steel used to prepare the steel plate has a chemical composition, in terms of mass percentage, of:

[0008] C: 0.10~0.30%; Si: 0.5~2.0%; Mn: 1.0~3.0%; P≤0.1%; S: ≤0.01%;

[0009] Als: 0.020~0.070%; Ti: 0.040~0.060%; N: ≤0.01%; the balance is Fe and unavoidable impurities;

[0010] The raw steel is made into slabs after smelting and casting, and the slabs are processed through hot rolling, pickling, flattening, degreasing, continuous annealing, hot-dip galvanizing, skin finishing and straightening to obtain the zinc-aluminum-magnesium coated steel plate.

[0011] Preferably, in the hot rolling process, the starting temperature of the hot rolling is controlled to be 1200-1300°C, the final rolling temperature of the finish rolling is controlled to be 850-950°C, and the coiling temperature is controlled to be 550-620°C.

[0012] Preferably, the starting temperature of hot rolling is 1240-1300°C, the final rolling temperature of fine rolling is 850-900°C, and the coiling temperature is 600-650°C; the mechanical properties of the hot-rolled finished product are controlled as follows: yield strength ≥400MPa, tensile strength ≥480MPa, and elongation A80 ≥16%.

[0013] Preferably, in the pickling process, the hot-rolled strip is subjected to jet pickling, the hydrochloric acid concentration used for pickling is 90-130 g / L, the pickling temperature is 80-90° C., and the pickling speed is 100-170 m / min; and / or,

[0014] In the leveling process, the leveling machine elongation is controlled to be 3-5%.

[0015] Preferably, in the degreasing and cleaning process, the steel strip after being processed in the flattening process is degreased and decontaminated by using a cleaning method of alkali solution spraying + alkali solution brushing + alkali solution electrolysis.

[0016] Preferably, in the continuous annealing process, the strip after the degreasing and cleaning process is annealed in a continuous annealing furnace, the annealing time is controlled to be 40 to 60 seconds, the dew point of the annealing furnace is -20 to 10°C, the furnace pressure is 0.4 to 1.0 mbar, the hydrogen content is 5 to 11%, the temperature of the annealing furnace soaking section is 750 to 830°C, and the temperature of the strip entering the zinc pot is 460 to 500°C.

[0017] Preferably, the chemical composition of the alkali solution is: 20-40 g / L sodium hydroxide, 10-20 g / L sodium carbonate, 5-10 g / L trisodium phosphate, 3-5 g / L sodium pyrophosphate, 3-5 g / L sodium silicate and 1-2 g / L sodium dodecylbenzene sulfonate.

[0018] Preferably, the electrolysis current density used in the alkali solution electrolysis is 15 to 20 A / dm 2 The solution temperature for electrolytic cleaning and hot water rinsing is 75-85°C.

[0019] Preferably, the total content of residual oil and residual iron on one side of the strip after degreasing and cleaning is controlled to be ≤10mg / m 2 , reflectivity ≥80%.

[0020] Preferably, in the hot-dip galvanizing process, the strip steel after the continuous annealing process is immersed in a zinc pot for hot-dip galvanizing of aluminum-magnesium alloy, the bath temperature is controlled to be 450-490° C., and the balanced wetting force of the zinc liquid on the steel plate is ≥0.6 N / m;

[0021] Calculated by mass percentage, the plating solution components used are: Al: 6-13%, Mg: 1-6%, Si: 0.2-1.0%, impurity elements ≤ 0.1%, and the rest is Zn.

[0022] Preferably, the composition of the plating solution is: Al: 6-13, Mg: 1-3, Si: 0.2-0.5, impurity elements ≤ 0.1, and the rest is Zn; the hot dip plating time is 3-5s, and the coating weight is 200-400g / m 2 .

[0023] Preferably, the hot-dip coated steel strip is rapidly cooled by gas injection forced cooling, and the cooling rate is controlled to be ≥30°C / s and the high span temperature is ≤200°C;

[0024] The coating after controlled hot-dip plating consists of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic structures. The thickness of the intermediate alloy layer is ≤2μm, and the content of the Zn-rich phase is ≤30%.

[0025] Preferably, in the skinning and straightening process, the surface roughness of the galvanized sheet after skinning is controlled to be 0.8μm≤the arithmetic mean value of the surface roughness of the galvanized sheet Ra≤1.2μm, 60≤the number of peaks Rpc≤120, the maximum surface roughness Rmax≤3Ra, the skinning elongation is 1-3%, and the straightening elongation is 0.2-0.3%.

[0026] In a second aspect, the zinc-aluminum-magnesium coated steel plate for the photovoltaic support described in the present disclosure is prepared by the method described in any one of the first aspects.

[0027] The present invention has the following beneficial effects:

[0028] The zinc-aluminum-magnesium coated steel plate for photovoltaic brackets of the present invention adopts heat-based hot-dip galvanized aluminum-magnesium alloy, has low production cost and better corrosion resistance than existing galvanized products, which not only conforms to the green and low-carbon development trend of the photovoltaic industry, but also has high surface quality, coating adhesion and elongation, and the comprehensive performance fully meets the requirements of steel for photovoltaic brackets. Therefore, the zinc-aluminum-magnesium coated steel plate for brackets provided in this application meets the urgent needs of the photovoltaic industry for high-strength, high-corrosion-resistant and low-cost coated steel plates for photovoltaic brackets, and has broad application prospects in the photovoltaic field.

[0029] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0030] Figure 1 This is the microstructure of the zinc-aluminum-magnesium coating. DETAILED DESCRIPTION

[0031] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure. At the same time, unless the context clearly requires, the words "including", "comprising" and the like in the entire specification and claims should be interpreted as including rather than exclusive or exhaustive meanings; that is, the meaning of "including but not limited to".

[0032] The present disclosure describes in detail the zinc-aluminum-magnesium coated steel sheet for photovoltaic brackets and the preparation method thereof through specific embodiments. The preparation method of the zinc-aluminum-magnesium coated steel sheet for photovoltaic brackets uses raw steel whose chemical composition, in terms of mass percentage, is as follows:

[0033] C: 0.10~0.30%; Si: 0.5~2.0%; Mn: 1.0~3.0%; P≤0.1%; S: ≤0.01%;

[0034] Als: 0.020~0.070%; Ti: 0.040~0.060%; N: ≤0.01%; the balance is Fe and unavoidable impurities.

[0035] The method is prepared according to the process of hot rolling, pickling, leveling, degreasing and cleaning, continuous annealing, hot dip plating, skin pass and straightening. The specific control parameters of each process are as follows:

[0036] 1. Hot rolling process:

[0037] In the hot rolling process of a specific embodiment, the starting temperature of hot rolling is 1200-1300°C, the final rolling temperature of finish rolling is 850-950°C, and the coiling temperature is 550-620°C.

[0038] Preferably, the starting temperature of the hot rolling is 1240-1300°C, the final rolling temperature of the fine rolling is 850-900°C, and the coiling temperature is 600-650°C; the mechanical properties of the hot-rolled finished product are controlled as follows: yield strength ≥400MPa, tensile strength ≥480MPa, and elongation A80 ≥16%.

[0039] 2. Pickling process:

[0040] In a pickling process of a specific embodiment, the hot-rolled strip is subjected to jet pickling, the hydrochloric acid concentration used for pickling is 90-130 g / L, the pickling temperature is 80-90° C., and the pickling speed is 100-170 m / min.

[0041] Preferably, the free acidity of the pickling is 80-120 g / L, and the total acidity is 220-230 g / L.

[0042] 3. Leveling process:

[0043] In a leveling process of a specific embodiment, the pickled steel strip is leveled at a light reduction rate, and the elongation of the leveling machine is controlled to be 3-5% to improve the shape and surface quality of the steel strip.

[0044] 4. Degreasing and cleaning process:

[0045] In a specific embodiment, in the degreasing and cleaning process, the strip steel after the flattening process is degreased and decontaminated by alkali spraying, alkali brushing and alkali electrolytic cleaning. The chemical composition of the alkali solution used is: 20-40 g / L sodium hydroxide, 10-20 g / L sodium carbonate, 5-10 g / L trisodium phosphate, 3-5 g / L sodium pyrophosphate, 3-5 g / L sodium silicate and 1-2 g / L sodium dodecylbenzene sulfonate.

[0046] The electrolysis current density of the alkali solution electrolysis is controlled to be 15-20A / dm 2 The solution temperature for electrolytic cleaning and hot water rinsing is 75-85°C.

[0047] After the degreasing and cleaning process, the total content of residual oil and residual iron on one side of the strip is controlled to be ≤10mg / m 2 , reflectivity ≥80%.

[0048] 5. Continuous withdrawal process:

[0049] In the continuous annealing process of a specific embodiment, the strip is annealed after the degreasing and cleaning process in the continuous annealing furnace, the steel plate is kept in the furnace (annealing time) for 40 to 60 seconds, the dew point of the induction heating furnace is -20 to 10°C, the furnace pressure is 0.4 to 1.0 mbar, the hydrogen content is 5 to 11%, the temperature of the annealing furnace soaking section is 750 to 830°C, and the temperature of the strip entering the zinc pot is 460 to 500°C.

[0050] 6. Hot dip galvanizing process:

[0051] In the hot-dip plating process of a specific embodiment, the steel strip treated by the continuous annealing process is immersed in a zinc pot for hot-dip galvanizing of aluminum-magnesium alloy, and the plating solution temperature is controlled to be 450-490°C; the plating solution components used are, in terms of mass percentage, Al: 6-13%, Mg: 1-6%, Si: 0.2-1.0%, impurity elements ≤0.1%, and the rest is Zn; the balanced wetting force of the zinc liquid on the steel plate is ≥0.6N / m, which not only ensures that the steel strip has good wettability in the zinc liquid, but also that the coating has good adhesion.

[0052] Preferably, the composition of the plating solution is: Al: 6-13%, Mg: 1-3%, Si: 0.2-0.5%, impurity elements ≤ 0.1%, and the rest is Zn; the hot dip plating time is 3-5s, and the coating weight is 200-400g / m 2 .

[0053] Preferably, a gas injection forced cooling method is used to rapidly cool the hot-dip coated steel strip, with a cooling rate of ≥30°C / s and a high span temperature of ≤200°C.

[0054] Preferably, the coating after hot-dip plating is controlled to be composed of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic structure, the thickness of the intermediate alloy layer is ≤2μm, and the content of Zn-rich phase is ≤30%.

[0055] 7. Finishing and straightening process:

[0056] In the skinning and straightening process of a specific embodiment, the strip steel after the hot-dip galvanizing process is subjected to skinning, straightening, passivation and coiling to obtain the zinc-aluminum-magnesium coated steel plate for the photovoltaic support.

[0057] Preferably, the surface roughness of the galvanized sheet after skin-passing is 0.8 μm ≤ the arithmetic mean value of the surface roughness of the galvanized sheet Ra ≤ 1.2 μm, 60 ≤ the number of peaks Rpc ≤ 120, the maximum surface roughness Rmax ≤ 3Ra, the skin-passing elongation is 1 to 3%, and the tensile elongation is 0.2 to 0.3%.

[0058] After the skin-passing and straightening processes, the finished mechanical properties of the zinc-aluminum-magnesium coated steel sheet are controlled to be: yield strength ≥ 350MPa, tensile strength ≥ 420MPa, and elongation A80 ≥ 16%.

[0059] The following are preferred embodiments of the present disclosure.

[0060] Example 1

[0061] The zinc-aluminum-magnesium coated steel sheet for photovoltaic brackets is prepared according to the method of the present invention, which is specifically as follows:

[0062] 1. The chemical composition of the raw steel used, calculated by mass percentage, is:

[0063] C: 0.2, Si: 0.5, Mn: 1.0, P: 0.020, S: 0.005, Als: 0.070; Ti: 0.060; N: 0.003; the remainder is Fe and inevitable impurities.

[0064] 2. Hot rolling:

[0065] The steel is made into slabs after smelting and casting. The slabs are heated at a heating temperature of 1320℃ and kept warm for 1h before hot rolling. The starting temperature of hot rolling is 1240℃ and the finishing rolling is completed at a final rolling temperature of 850℃. The thickness of the hot rolled steel plate is about 2.5mm and the hot rolled coiling temperature is about 600℃.

[0066] The mechanical properties of the hot-rolled finished product are: yield strength of 580 MPa, tensile strength of 720 MPa, and elongation A80 of 16%.

[0067] 3. Pickling:

[0068] The hot-rolled strip was subjected to jet pickling, with a hydrochloric acid concentration of 130 g / L, a pickling temperature of 80° C., and a pickling speed of 170 m / min.

[0069] 4. Leveling:

[0070] The pickled strip is leveled, and the elongation of the leveler is about 5%.

[0071] 5. Degreasing and cleaning:

[0072] The flattened strip is degreased and cleaned by alkali spraying + alkali brushing + alkali electrolytic cleaning, wherein the chemical composition of the alkali solution used is: 40g / L sodium hydroxide, 20g / L sodium carbonate, 10g / L trisodium phosphate, 5g / L sodium pyrophosphate, 5g / L sodium silicate, and 2g / L sodium dodecylbenzene sulfonate.

[0073] The current density of electrolytic cleaning is 20A / dm 2 , the solution temperature for electrolytic cleaning and hot water rinsing is 75°C.

[0074] After degreasing and cleaning, the total content of residual oil + residual iron on one side of the strip is 3mg / m 2 , the reflectivity is 86%.

[0075] 6. Continuous retreat:

[0076] The strip after degreasing and cleaning is annealed for 60 seconds, the dew point of the induction heating furnace (annealing furnace) is 10°C, the furnace pressure is 0.4 mbar, the hydrogen content is 5%, the temperature of the annealing furnace soaking section is 830°C, and the temperature of the strip entering the zinc pot is 500°C.

[0077] 7. Hot dip galvanizing:

[0078] The annealed strip is immersed in a molten bath with an aluminum content of 11%, a magnesium content of 3%, a silicon content of 0.5%, and the rest being zinc for hot-dip galvanizing of an aluminum-magnesium alloy. The bath temperature is 480°C, and the balanced wetting force of the zinc bath on the steel plate is 1.0N / m. The hot-dip galvanizing time is 5s, and the double-sided coating weight is 350g / m 2 .

[0079] The hot-dip galvanized strip is rapidly cooled by gas injection forced cooling method, with a cooling rate of 30°C / s and a high span temperature of 170°C.

[0080] The coating after hot-dip galvanizing consists of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic. The thickness of the intermediate alloy layer is 1.5 μm, and the content of Zn-rich phase is 27%.

[0081] 8. Finishing and straightening:

[0082] The hot-dip galvanized strip steel is subjected to skin finishing and straightening treatment to obtain the zinc-aluminum-magnesium coated steel plate for the photovoltaic support of this embodiment 1.

[0083] During the skinning, the skinning roller is subjected to laser roughening and polishing. After skinning, the surface roughness Ra of the galvanized sheet is 0.8 μm, the number of peaks Rpc is 100, the maximum surface roughness Rmax is 2.0 μm, the skinning elongation is 3%, and the tensile elongation is 0.3%.

[0084] According to the tensile test method for metal materials in GB / T 228, the yield strength of the zinc-aluminum-magnesium coated steel plate obtained in this Example 1 is 504 MPa, the tensile strength is 640 MPa, the elongation A80 is 18%, there is no shedding of the coating during 0T bending, and there are no defects on the surface of the steel strip that affect the quality of the product appearance.

[0085] Figure 1 The microscopic morphology of the zinc-aluminum-magnesium coating in Example 1 is shown in FIG. Figure 1As shown, the coating is composed of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic. The thickness of the intermediate alloy layer is about 2 μm, and the content of the Zn-rich phase is about 30%.

[0086] The obtained coating sample had no red rust on the surface after 6000h of salt spray corrosion, which met the requirements for steel used in photovoltaic brackets.

[0087] Example 2

[0088] The zinc-aluminum-magnesium coated steel sheet for photovoltaic brackets is prepared according to the method of the present invention, which is specifically as follows:

[0089] 1. The chemical composition of the raw steel used, calculated by mass percentage, is as follows:

[0090] C: 0.3, Si: 2.0, Mn: 2.0, P: 0.030, S: 0.005, Als: 0.050; Ti: 0.060; N: 0.0030; the remainder is Fe and inevitable impurities.

[0091] 2. Hot rolling:

[0092] The steel is made into slabs after smelting and casting. The slabs are heated at a heating temperature of 1380℃ and kept warm for 1h before hot rolling. The starting temperature of hot rolling is 1300℃ and the finishing rolling is completed at a final rolling temperature of 900℃. The thickness of the hot rolled steel plate is about 2.0mm and the hot rolled coiling temperature is about 650℃.

[0093] The mechanical properties of the hot-rolled finished product are as follows: yield strength is 510MPa, tensile strength is 630MPa, and elongation A80 is 22%.

[0094] 3. Pickling:

[0095] The hot-rolled strip was subjected to jet pickling, with a hydrochloric acid concentration of 90 g / L, a pickling temperature of 90° C., and a pickling speed of 120 m / min.

[0096] 4. Leveling:

[0097] The pickled strip is leveled, and the elongation of the leveler is about 5%.

[0098] 5. Degreasing and cleaning:

[0099] The flattened strip is degreased and cleaned by alkali spraying + alkali brushing + alkali electrolytic cleaning, wherein the chemical composition of the alkali solution is: 20g / L sodium hydroxide, 10g / L sodium carbonate, 5g / L trisodium phosphate, 5g / L sodium pyrophosphate, 5g / L sodium silicate, and 2g / L sodium dodecylbenzene sulfonate.

[0100] The current density of electrolytic cleaning is 15A / dm2 , the solution temperature for electrolytic cleaning and hot water rinsing is 85°C.

[0101] After degreasing and cleaning, the total content of residual oil + residual iron on one side of the strip is 10mg / m 2 , the reflectivity is 81%.

[0102] 6. Continuous retreat:

[0103] The strip after degreasing and cleaning is annealed for 50 seconds, the dew point of the induction heating furnace (annealing furnace) is 0°C, the furnace pressure is 0.4 mbar, the hydrogen content is 11%, the annealing furnace soaking temperature is 750°C, and the strip entering the zinc pot temperature is 460°C.

[0104] 7. Hot dip galvanizing:

[0105] The annealed steel strip is immersed in a molten bath with an aluminum content of 6%, a magnesium content of 1%, a silicon content of 0.2%, and the rest of zinc for hot-dip galvanizing of aluminum-magnesium alloy. The bath temperature is 470°C, and the balanced wetting force of the zinc liquid on the steel plate is about 0.7N / m. The hot-dip galvanizing time is 5s, and the coating weight is 270g / m 2 .

[0106] The hot-dip coated strip is rapidly cooled by gas injection forced cooling method, with a cooling rate of 30°C / s and a high span temperature of 170°C.

[0107] The coating after hot-dip galvanizing consists of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic. The thickness of the intermediate alloy layer is 1.5 μm, and the content of Zn-rich phase is 25%.

[0108] 8. Finishing and straightening:

[0109] After the hot-dip galvanized strip steel is subjected to skin finishing and tension straightening treatment, the zinc-aluminum-magnesium coated steel plate for the photovoltaic support of this embodiment 2 is obtained.

[0110] During the skinning, the skinning roller is subjected to laser roughening and polishing. After skinning, the surface roughness Ra of the galvanized sheet is 1.0 μm, the number of peaks Rpc is 60, the maximum surface roughness Rmax is 2.5 μm, the skinning elongation is 2%, and the tensile elongation is 0.2%.

[0111] After testing, the yield strength of the zinc-aluminum-magnesium coated steel plate obtained in Example 2 is 436MPa, the tensile strength is 554MPa, the elongation A80 is 24%, the 0T bending coating does not fall off, and the strip surface has no defects that affect the product appearance quality. And the obtained coating sample has no red rust on the plate surface after 4000h salt spray corrosion, which meets the requirements for photovoltaic bracket steel.

[0112] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A method for preparing a zinc-aluminum-magnesium coated steel plate for a photovoltaic support, characterized in that: include: The raw steel used to prepare the steel plate has a chemical composition, in terms of mass percentage, of: C: 0.10~0.30%; Si: 0.5~2.0%; Mn: 1.0~3.0%; P≤0.1%; S：≤0.01％； Als: 0.020~0.070%; Ti ：0.040～0.060％； N: ≤0.01%; the balance is Fe and unavoidable impurities; The raw steel is made into slabs after smelting and casting, and the slabs are processed through hot rolling, pickling, flattening, degreasing, continuous annealing, hot-dip galvanizing, skin finishing and straightening to obtain the zinc-aluminum-magnesium coated steel plate.

2. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 1, characterized in that: In the hot rolling process, the starting rolling temperature of the hot rolling is controlled to be 1200-1300°C, the final rolling temperature of the finish rolling is controlled to be 850-950°C, and the coiling temperature is controlled to be 550-620°C.

3. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 2, characterized in that: The hot rolling start temperature is 1240-1300°C, the finishing rolling temperature is 850-900°C, and the coiling temperature is 600-650°C; the mechanical properties of the hot-rolled finished product are controlled as follows: yield strength ≥400MPa, tensile strength ≥480MPa, and elongation A80 ≥16%.

4. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 3, characterized in that: In the pickling process, the hot-rolled strip is subjected to jet pickling, the hydrochloric acid concentration used for pickling is 90-130 g / L, the pickling temperature is 80-90° C., and the pickling speed is 100-170 m / min; and / or, In the leveling process, the leveling machine elongation is controlled to be 3-5%.

5. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 4, characterized in that: In the degreasing and cleaning process, the strip steel treated in the flattening process is degreased and decontaminated by using a cleaning method of alkali solution spraying + alkali solution brushing + alkali solution electrolysis; and / or, In the continuous annealing process, the strip steel after the degreasing and cleaning process is annealed in a continuous annealing furnace, the annealing time is controlled to be 40 to 60 seconds, the dew point of the annealing furnace is -20 to 10°C, the furnace pressure is 0.4 to 1.0 mbar, the hydrogen content is 5 to 11%, the temperature of the annealing furnace soaking section is 750 to 830°C, and the temperature of the strip steel entering the zinc pot is 460 to 500°C.

6. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 5, characterized in that: The chemical composition of the alkali solution is: 20-40 g / L sodium hydroxide, 10-20 g / L sodium carbonate, 5-10 g / L trisodium phosphate, 3-5 g / L sodium pyrophosphate, 3-5 g / L sodium silicate and 1-2 g / L sodium dodecylbenzene sulfonate; and / or, The electrolysis current density used in the alkali solution electrolysis is 15 to 20 A / dm 2 , the solution temperature of electrolytic cleaning and hot water rinsing is 75-85°C; and / or, After degreasing and cleaning, the total content of residual oil and residual iron on one side of the strip steel should be ≤10mg / m 2 , reflectivity ≥80%.

7. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 6, characterized in that: In the hot-dip galvanizing process, the strip steel after the continuous annealing process is immersed in a zinc pot for hot-dip galvanizing of aluminum-magnesium alloy, the bath temperature is controlled to be 450-490° C., and the balanced wetting force of the zinc liquid on the steel plate is ≥0.6 N / m; The composition of the plating solution used is calculated by mass percentage: Al: 6-13%, Mg: 1-6%, Si: 0.2-1.0%, impurity elements ≤ 0.1%, and the rest is Zn.

8. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 7, characterized in that: The composition of the plating solution is: Al: 6-13, Mg: 1-3, Si: 0.2-0.5, impurity elements ≤ 0.1, and the rest is Zn; the hot dip plating time is 3-5s, and the coating weight is 200-400g / m 2 and / or, The hot-dip galvanized strip is rapidly cooled by gas injection forced cooling method, and the cooling rate is controlled to be ≥30℃ / s and the high span temperature is ≤200℃; The coating after controlled hot-dip plating consists of Zn-rich phase, Al-rich phase, Zn / MgZn2 / Al ternary eutectic, Zn / Al binary eutectoid, and Zn / MgZn2 binary eutectic structures. The thickness of the intermediate alloy layer is ≤2μm, and the content of the Zn-rich phase is ≤30%.

9. The method for preparing the zinc-aluminum-magnesium coated steel sheet for photovoltaic bracket according to claim 8, characterized in that: In the skinning and straightening process, the surface roughness of the galvanized sheet after skinning is controlled to be 0.8μm≤the arithmetic mean value of the surface roughness of the galvanized sheet Ra≤1.2μm, 60≤the number of peaks Rpc≤120, the maximum surface roughness Rmax≤3Ra, the skinning elongation is 1-3%, and the straightening elongation is 0.2-0.3%.

10. A zinc-aluminum-magnesium coated steel plate for photovoltaic support, characterized in that: The steel plate is: The method is prepared by any one of claims 1 to 9.

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