Strip steel hot dipping process, steel plate, frame for photovoltaic module and photovoltaic module

Abstract

The invention discloses a strip steel hot dipping process, a steel plate, a frame for a photovoltaic module and the photovoltaic module, relates to the technical field of photovoltaic module materials, and aims to solve the problem that micro-cracks are extremely easy to form when zinc-aluminum-magnesium strip steel is processed into a complex section. The strip steel hot dipping process comprises the following steps: refining an intermediate alloy ingot; completely immersing the refined intermediate alloy ingot in the zinc liquid, and uniformly stirring to obtain a hot-dip galvanizing liquid; the strip steel is immersed in the hot-dip galvanizing liquid for hot-dip galvanizing; and the strip steel subjected to hot dipping is subjected to first cooling, heat preservation is conducted for a certain time, then second cooling is conducted, and the zinc-aluminum-magnesium coated steel plate is obtained. When the zinc-aluminum-magnesium coated steel plate is used as a frame raw material for manufacturing a photovoltaic frame, the characteristics of excellent corrosion resistance, high hardness and few microcracks are achieved, the content of Mg2Zn11 in the prepared coating is obviously increased, the microcrack rating is greatly improved, but the hardness is only reduced to III from IV, the crack gap ratio after cold bending processing reaches the optimal level, and the performance of the photovoltaic frame is greatly improved. Compared with the same industry, the method is higher in level.

Description

Technical Field

[0001] This application relates to the technical field of photovoltaic module materials, and particularly to a strip hot-dip plating process, a steel plate, a frame for a photovoltaic module, and a photovoltaic module. Background Art

[0002] For galvanized steel, by plating the more active metal zinc on the surface of the steel, a primary battery reaction occurs on the steel surface, replacing the corrosion of steel / iron with the corrosion of zinc (sacrificing the anode), thereby extending the service life of the steel. Based on this, the zinc-aluminum-magnesium coated steel has not only the anti-corrosion function of sacrificing the anode, but also the dense products (such as MgAl-LDH (Mg6Al2(OH)16CO3·4H2O), ZnAl-LDH (Zn2Al(OH)6(CO3)1 / 2·xH2O), etc.) formed after the zinc-aluminum-magnesium alloy on the surface of the zinc-aluminum-magnesium coated steel is corroded can block the contact between corrosive media (water vapor, oxygen, and corrosive gases) and steel / iron. Therefore, the zinc-aluminum-magnesium coated steel has a longer service life than galvanized steel.

[0003] However, in the prior art, after the zinc-aluminum-magnesium coated steel is stored for a long time in a harsh corrosion environment such as high temperature and high humidity, the coating surface of the zinc-aluminum-magnesium coated steel plate is easily oxidized, and sometimes discoloration occurs, forming a gray-black "blackening". To solve the above technical problems, Chinese Patent Document CN110832105A discloses a molten Zn-Al-Mg series coated steel plate, which has a coating containing 1% by mass to 22% by mass of Al and 0.1% by mass to 10% by mass of Mg on the steel plate surface, and the intensity ratio of the X-ray diffraction peak of the Mg-Zn compound phase in the coating to MgZn2 / Mg2Zn 11 is 0.2 or less. By adopting the above technical solution, in the prepared zinc-aluminum-magnesium coated steel plate, the Mg-Zn compound phase is mainly the Mg2Zn 11 phase, and the Mg2Zn 11 phase crystallizes in a specific amount in the whole coating, so that a molten Zn-Al-Mg series coated steel plate without black spots can be manufactured.

[0004] However, the above-mentioned technologies do not consider the processability and coating cracking problems during the processing of zinc-aluminum-magnesium coated steel sheets, resulting in the easy formation of microcracks when the zinc-aluminum-magnesium coated steel sheets are processed into complex cross-sections. For example, when processing the zinc-aluminum-magnesium coated steel sheet into the frame of a photovoltaic module, due to the complex cross-sectional shape of the frame of the photovoltaic module, it needs to undergo dozens of cold bending processes, and finally forms multiple 90-degree and 180-degree bending regions. This leads to problems such as coating cracking (microcracks) and peeling during the cold bending process of the zinc-aluminum-magnesium coated steel sheet, resulting in poor corrosion resistance of the steel frame processed from the zinc-aluminum-magnesium coated steel sheet, and further affecting the service life and long-term stability of the photovoltaic module composed of the frame. Summary of the Invention

[0005] In order to solve the problems of poor processability and easy coating cracking of zinc-aluminum-magnesium coated steel sheets in the prior art, the present invention provides a strip hot-dip plating process, a steel sheet, a frame for a photovoltaic module, and a photovoltaic module. The steel sheet prepared by this process has better hardness and ductility, and is more suitable for the processing and use of the frame of a photovoltaic module.

[0006] In the first aspect, the present invention provides a strip hot-dip plating process, including the following steps:

[0007] Refine intermediate alloy ingots, including Al-Si alloy, Al-rare earth metal alloy (i.e., Al-rare earth metal alloy), and Al-Mg alloy;

[0008] Immerse the refined intermediate alloy ingots in zinc liquid and stir to obtain a hot-dip galvanized liquid of Zn-Al-Mg-Si-rare earth metal;

[0009] Immerse the strip in the hot-dip galvanized liquid for hot-dip plating;

[0010] Perform the first cooling on the hot-dip plated strip, cool it down to 335°C to 355°C, keep it warm for 15S to 30S, and then perform the second cooling, gradually cool it down to below 220°C to obtain a zinc-aluminum-magnesium coated steel sheet.

[0011] Compared with the prior art, in the above technical solution, silicon, magnesium, and rare earth metals are respectively refined with aluminum into intermediate alloy ingots, and then immersed in zinc liquid to form a hot-dip galvanizing solution. First, the hot-dip galvanizing solution formed by using the intermediate alloy ingots can reduce the loss caused by the direct melting of the above silicon, aluminum, magnesium, and rare earth metals in the zinc liquid. Secondly, since both rare earth metals and magnesium are active metals, alloying can reduce the oxidation of active metals, thereby reducing the influence of oxides on the performance of the hot-dip galvanizing solution. Moreover, it can also reduce the generation of zinc slag in the hot-dip galvanizing solution caused by the direct melting of active metals in the zinc liquid. In summary, the hot-dip galvanizing solution formed by forming intermediate alloy ingots and immersing them in zinc liquid has the advantages of high content of effective components and relatively low content of impurities such as oxides and zinc slag, and thus can improve the surface coating quality of the zinc-aluminum-magnesium coated steel sheet after hot-dip galvanizing.

[0012] In addition, in the above technical solution, it should be understood that the main alloy phases in the zinc-aluminum-magnesium coating include aluminum-rich phase, zinc-rich phase, zinc-magnesium binary eutectic, and zinc-aluminum-magnesium ternary eutectic. Among them, the binary eutectic and ternary eutectic can be further divided into Zn-Mg2Zn 11 or Zn-MgZn2 binary eutectic and Zn-Al-Mg2Zn 11 or Zn-Al-MgZn2 ternary eutectic. The inventors have found that by adding a heat preservation process and controlling different heat preservation times in the present invention, the ratio of the above two metal compounds of Mg2Zn 11 and MgZn2 can be adjusted to obtain a zinc-aluminum-magnesium coated steel sheet with different relative proportions of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ). Since the mechanical properties of Mg2Zn 11 and MgZn2 are different, the ductility and hardness of the coating can be adjusted by changing the content of the two in the coating. The zinc-aluminum-magnesium coated steel sheet prepared under the process conditions of the present invention improves the corrosion resistance of the zinc-aluminum-magnesium coated steel sheet, reduces the coating thickness, and has an appropriate relative proportion of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ), so that the adjusted zinc-aluminum-magnesium coated steel sheet has characteristics such as hardness, ductility, and toughness. When it is used to manufacture a photovoltaic steel frame, it not only has excellent corrosion resistance but also has the characteristics of scratch resistance and few microcracks.

[0013] Furthermore, the mass percentage of silicon in the Al-Si alloy is 10-20 wt%; and / or,

[0014] the mass percentage of rare earth metals in the Al-rare earth metal alloy is 5-15 wt%; and / or,

[0015] the mass percentage of magnesium in the Al-Mg alloy is 35-45 wt%.

[0016] Compared with the prior art, in the above technical solution, adding an appropriate amount of Si element to the zinc-aluminum-magnesium plated steel can not only inhibit the zinc rare earth from improving the processability of the plated steel, but also improve the corrosion resistance by reducing the self-corrosion current of the coating. Adding an appropriate amount of rare earth metal to the zinc-aluminum-magnesium plated steel can improve the fluidity of the zinc bath, thereby thinning the coating; in addition, the rare earth metal can also prevent the excessive growth of grains, refine the coating structure, and make the binary eutectic and ternary eutectic in the zinc-aluminum-magnesium coating more evenly distributed. The above technical solution can improve the corrosion resistance of the zinc-aluminum-magnesium plated steel by limiting the content of each component in the alloy and making each component act synergistically, and has good hardness and ductility on the premise of ensuring corrosion resistance.

[0017] Further, based on the mass percentage of the hot-dip galvanizing bath, the hot-dip galvanizing bath includes 1-12 wt% of aluminum, 0.5-5.5 wt% of magnesium, 0.1-1 wt% of silicon, and 0.05-0.14 wt% of rare earth metal, and the balance is Zn and impurities.

[0018] Compared with the prior art, the above technical solution can ensure that the content of each component in the hot-dip galvanizing bath is appropriate by controlling the content of each component in the hot-dip galvanizing bath, and further ensure that in the hot-dip plating process, the Mg2Zn in the formed hot-dip coating 11 / (MgZn2 + Mg2Zn 11 ) can reach an appropriate ratio. After the zinc-aluminum-magnesium plated steel prepared by the above technical solution is subjected to performance testing, according to the result data in Table 1, it can be known that its microcrack rating can reach an excellent level.

[0019] Further, based on the mass percentage of the hot-dip galvanizing bath, the hot-dip galvanizing bath includes 9-12 wt% of aluminum, 3.5-5.5 wt% of magnesium, 0.8-1 wt% of silicon, and 0.12-0.14 wt% of rare earth metal, and the balance is Zn and impurities.

[0020] Compared with the prior art, the above technical solution further controls the aluminum content in the hot-dip galvanizing bath to be 9-12 wt%. After experimental verification, for the zinc-aluminum-magnesium coating with an aluminum content higher than 9 wt%, combined with the above specific amounts of zinc, magnesium, silicon, and rare earth metal, after 15 s - 30 s of heat preservation, the content of Mg2Zn 11 significantly increases, and the microcrack rating is greatly improved, but the hardness only drops from IV to III. The comprehensive performance of hardness and ductility of this kind of zinc-aluminum-magnesium coating is better and is more suitable for the processing and use of the zinc-aluminum-magnesium coated steel frame of photovoltaic modules.

[0021] Further, the rare earth metal is lanthanum and / or cerium.

[0022] Compared with the prior art, the above technical solution further defines that the rare earth metal is lanthanum and / or cerium. These two rare earth metals have more excellent performance in improving the fluidity of the zinc liquid, and can effectively prevent the excessive growth of grains on the surface of the coating, refine the coating structure, and further improve the uniformity of the binary eutectic and ternary eutectic distributions in the zinc-aluminum-magnesium coating.

[0023] Further, the cooling rate of the first cooling is 20°C / second to 50°C / second; and / or,

[0024] The cooling rate of the second cooling is 5°C / second to 100°C / second.

[0025] Compared with the prior art, the above technical solution further defines the cooling rate. By controlling the first cooling rate, a zinc-aluminum-magnesium alloy coating can be initially formed on the steel plate. Then, it is gradually cooled to below 220°C at the second cooling rate. During the gradual cooling process, the grains can be further refined, making the coating more uniform and reducing the generation of microcracks.

[0026] Further, the refined intermediate alloy ingot is completely immersed in the zinc liquid and stirred evenly to obtain a hot-dip galvanized zinc liquid of Zn-Al-Mg-Si-rare earth metal, including:

[0027] The zinc ingot is heated to melt above 500°C and then heated up to 660°C - 680°C;

[0028] The refined Al-Si alloy, Al-rare earth metal alloy, and Al-Mg alloy are pressed into the zinc liquid until completely immersed;

[0029] During the melting process of the intermediate alloy ingot, it is fully stirred to make the components in the zinc liquid evenly distributed.

[0030] Compared with the prior art, adopting the above technical solution, heating the zinc ingot to melt above 500°C can ensure that the zinc ingot is completely melted. Since the melting temperatures of the aluminum alloy ingot and the zinc ingot are different, after heating up to 660°C - 680°C, the refined Al-rare earth metal alloy, Al-Si alloy, and Al-Mg alloy can be melted with the zinc liquid. Full stirring during the melting process can ensure uniform melting of the alloy.

[0031] In a second aspect, the present invention also provides a zinc-aluminum-magnesium coated steel plate, including a strip steel plate and a hot-dip coating formed on the surface of the strip steel plate, prepared by applying the above strip steel hot-dip plating process. Calculated by mass percentage of the hot-dip coating, it includes 1 - 12wt% of aluminum, 0.5 - 5.5wt% of magnesium, 0.1 - 1wt% of silicon, and 0.05 - 0.14wt% of rare earth metal, and the balance is Zn and impurities.

[0032] Compared with the prior art, the beneficial effects of the zinc-aluminum-magnesium coated steel sheet of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here.

[0033] Further, the hot-dip coating layer includes a MgZn2 alloy phase and a Mg2Zn 11 alloy phase. Among them, Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) has a relative proportion of 60% to 100%.

[0034] Compared with the prior art, by limiting the relative mass proportion of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) in the hot-dip coating layer to be 60% to 100%, a zinc-aluminum-magnesium coated steel sheet with better anti-corrosion performance, ductility, and toughness performance can be obtained, which is more suitable for the processing and use of the zinc-aluminum-magnesium coated steel frame of photovoltaic modules.

[0035] In the third aspect, the present invention also provides a frame for a photovoltaic module, which is prepared by using the above zinc-aluminum-magnesium coated steel sheet.

[0036] Compared with the prior art, the beneficial effects of the frame for a photovoltaic module of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here.

[0037] In the fourth aspect, the present invention also provides a photovoltaic module, including the above frame for a photovoltaic module.

[0038] Compared with the prior art, the beneficial effects of the photovoltaic module of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here. Specific Embodiments

[0039] In order to make the technical problems, technical solutions, and beneficial effects to be solved by the present application clearer, the following further describes the present application in detail with reference to embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0040] In the first aspect, an embodiment of the present invention provides a strip hot-dip coating process, including the following steps:

[0041] Step S1, refining an intermediate alloy ingot, including an Al-Si alloy, an Al-rare earth metal alloy, and an Al-Mg alloy.

[0042] In the above technical solution, the source of the Al-Si alloy can be directly purchasing commercial Al-Si alloy products or obtaining the Al-Si alloy through a smelting method. Of course, during smelting, both aluminum and silicon can be commercially available products, or silicon can be obtained by recycling the solid waste silicon material generated during the manufacturing process of crystalline silicon batteries. For example, taking the silicon in the recycled solid waste silicon material and commercial aluminum as examples, the Al-Si alloy smelting method can be referred to as follows:

[0043] Step S11: Wash, pickling, and alkali wash the collected solid waste silicon material, and then perform secondary water washing on it. After drying, it is reserved as recycled silicon. Specifically, the process conditions such as water washing, pickling, and alkali washing involved in recycling silicon from solid waste silicon material can refer to the existing technology.

[0044] Step S12: Heat the aluminum ingot with the oxide layer removed in a resistance furnace until it is completely melted. After the temperature of the aluminum liquid drops to about 600°C - 680°C, add the recycled silicon and stir. For example, the temperature of the aluminum liquid can be selected to drop to about 600°C, 650°C, or 680°C before adding the recycled silicon. At this time, the silicon content can be controlled to account for 10 - 20 wt% of the total mass of the Al-Si alloy. For example, the silicon content can be 10 wt%, 15 wt%, or 20 wt% of the total mass of the Al-Si alloy. Then, heat up to about 800°C - 880°C again and keep it warm for 1.0 - 2.0 hours to melt the silicon material. It should be understood that in the actual application process, the temperature for reheating can be selected as 800°C, 840°C, or 880°C, and the holding time can be specifically selected as 1.0 hour, 1.5 hours, or 2.0 hours. Subsequently, cool it to about 650°C - 700°C. For example, the cooling temperature can be selected as 650°C, 670°C, or 700°C. After skimming, pour and cast the ingot. Argon is used as the protective atmosphere during the smelting process.

[0045] In another example, in the above technical solution, the smelting of the Al-rare earth metal alloy ingot can be referred to as follows:

[0046] Step S13: Heat the aluminum ingot with the oxide layer removed in a resistance furnace until it melts completely. After the temperature of the molten aluminum stabilizes at 800°C - 880°C, for example, the temperature of the molten aluminum can be selected as 800°C, 850°C, or 880°C, add rare earth metals wrapped in aluminum foil and stir. The rare earth metal can be a lanthanum-cerium mixture. In the lanthanum-cerium mixture, the total mass of metallic lanthanum and metallic cerium in the lanthanum-cerium mixture is ≥80wt%, and the cerium content in the lanthanum-cerium mixture is ≥50wt%. It should be understood that the proportion of the lanthanum-cerium mixture in the total mass of the Al-rare earth metal alloy can be further controlled to be 5 - 15wt%. For example, the proportion of the lanthanum-cerium mixture in the total mass of the Al-rare earth metal alloy can be selected as 5wt%, 7wt%, 9wt%, 11wt%, 13wt%, or 15wt%, etc. Under the above ratios, the hot-dip galvanizing solution can have better fluidity, thereby further improving the surface quality of the coating, reducing defects such as zinc grains, and refining the coating grains, but has no obvious effect on corrosion resistance, formability, and adhesion. In addition, through experimental verification, the applicant also found that when the lanthanum-cerium mixture accounts for 9 - 11wt% of the total mass of the Al-rare earth metal alloy, the fluidity of the prepared hot-dip galvanizing is the best, the formed coating has excellent ductility, and the micro-crack rating is the best. After the lanthanum-cerium mixture accounts for more than 15wt% of the total mass of the Al-rare earth metal alloy, the quality of the formed coating deteriorates, and it is difficult to repair micro-cracks. Skim the slag after holding for 1 - 1.5 hours, and then pour it into ingots. Argon is used as the protective atmosphere during the smelting process.

[0047] In another example, in the above technical solution, the refining of the Al-Mg alloy ingot can be referred to as follows:

[0048] Step S14: Heat the aluminum ingot with the oxide layer removed in a resistance furnace until it melts completely. After the temperature of the molten aluminum stabilizes at 550°C - 650°C, put the magnesium ingot into a graphite bell jar and quickly press it into the molten aluminum to keep the magnesium ingot completely submerged until it melts completely. Among them, the mass of the magnesium ingot can be further controlled to account for about 35wt% - 45wt% of the mass of the Al-Mg alloy ingot, then stir evenly, hold for 1 - 1.5 hours, skim the slag again, and pour it into ingots. Argon is used as the protective atmosphere during the smelting process.

[0049] Step S2: Immerse the refined intermediate alloy ingot completely in the zinc solution, stir evenly, and obtain a hot-dip galvanizing solution of Zn-Al-Mg-Si-rare earth metal.

[0050] In the above technical solution, it should be understood that the zinc ingot needs to be melted first to obtain the zinc solution. For example, the preparation method of the zinc solution can be referred to as follows: Add the weighed zinc ingot to the zinc pot and heat it to above 500°C to make it melt completely, thereby obtaining the zinc solution.

[0051] In order to make the master alloy ingot better melt in the zinc liquid, the embodiment of the present invention further controls to heat the zinc liquid to 660°C - 680°C, and then immerse the aforementioned refined Al-rare earth metal alloy, Al-Si alloy and Al-Mg alloy in the zinc liquid. Specifically, the Al-rare earth metal alloy, Al-Si alloy and Al-Mg alloy are placed in a graphite bell and quickly pressed into the zinc liquid to be completely immersed. During the alloy melting process, it is fully stirred to make the components in the zinc liquid evenly distributed. Of course, in order to obtain a coating with more excellent performance, after the master alloy ingot is completely melted, stirring can be continued for 10 - 30 minutes, and the temperature of the hot-dip galvanized liquid molten with the alloy ingot is maintained between 410°C and 480°C. By controlling the temperature of the hot-dip galvanized liquid, it is possible to avoid the hot-dip galvanized liquid from getting cold and affecting the subsequent coating effect.

[0052] Further, the hot-dip galvanized liquid obtained in the above technical solution, calculated by mass percentage of the hot-dip galvanized liquid, includes 1 - 12 wt% of aluminum, 0.5 - 5.5 wt% of magnesium, 0.1 - 1 wt% of silicon and 0.05 - 0.14 wt% of rare earth metal, and the balance is Zn and impurities. Under this ratio, combined with the heat preservation procedure, the Mg2Zn in the formed hot-dip coating 11 / (MgZn2 + Mg2Zn 11 ) can reach an appropriate proportion. Of course, it is also possible to further control that the hot-dip galvanized liquid includes 9 - 12 wt% of aluminum, 3.5 - 5.5 wt% of magnesium, 0.8 - 1 wt% of silicon and 0.12 - 0.14 wt% of rare earth metal, and the remaining part is Zn and impurities. For example, through further optimization, the inventor found that in the zinc-aluminum-magnesium coating with an aluminum content higher than 9 wt%, combined with the specific amounts of zinc, magnesium, silicon and rare earth metal, after heat preservation for 15s - 30s, the content of Mg2Zn 11 significantly increases, and the microcrack rating is greatly improved, but the hardness only drops from IV to III. The comprehensive performance of hardness and ductility of this kind of zinc-aluminum-magnesium coating is better and more suitable for the processing and use of the zinc-aluminum-magnesium coating steel frame of photovoltaic modules.

[0053] Step S3: Immerse the strip in the hot-dip galvanized liquid for hot-dip galvanizing; cool the strip after hot-dip galvanizing for the first time to 335°C - 355°C, keep it warm for 15S - 30S, and then cool it for the second time to gradually cool it below 220°C to obtain a zinc-aluminum-magnesium coated steel sheet.

[0054] In the above technical solution, immersing the strip in the hot-dip galvanized liquid for hot-dip galvanizing can specifically refer to the following steps:

[0055] Step S31: Uncoil the strip steel. After degreasing with alkali, pickling to remove rust, and drying, transfer it to an annealing furnace. To avoid the oxidation reaction of oxygen, metal oxidation will cause a decline in coating quality. Therefore, the strip steel is heated to 420°C to 490°C in a reducing atmosphere, and the reducing atmosphere is a mixed gas of hydrogen, inert gas, and nitrogen.

[0056] Step S32: Immerse the strip steel into the above-mentioned mixed zinc bath with a temperature between 410°C and 480°C through the furnace nose, and perform hot-dip coating for 3 seconds to 80 seconds.

[0057] Step S33: Pull out the strip steel that has completed hot-dip coating from the zinc bath, blow it with a nitrogen air knife and cool it, and then cool it down to 335°C to 355°C. In this step, the cooling rate can be selected as 20°C / second to 50°C / second. By controlling the cooling rate, it is beneficial to the alloying of the coating on the strip steel surface.

[0058] Step S34: Transfer the hot-dip coated strip steel in Step S33 to an alloying furnace and keep it warm for 15 seconds to 30 seconds. Through the heat preservation process and controlling the heat preservation time, the ratio of the two metal compounds Mg2Zn 11 and MgZn2 can be adjusted to obtain a zinc-aluminum-magnesium coated steel sheet with an appropriate mass ratio of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ). The adjusted zinc-aluminum-magnesium coated steel sheet has characteristics such as hardness, ductility, and toughness. When it is used to manufacture a photovoltaic steel frame, it not only has excellent corrosion resistance but also has the characteristics of scratch resistance and few microcracks.

[0059] Step S35: Subsequently, gradually cool the hot-dip coated strip steel in the alloying furnace (cooling rate is about 5°C / second to 100°C / second), and control the temperature of the strip steel reaching the top turning roll to be below 220°C. By controlling the cooling rate, the hot-dip coated strip steel is gradually cooled, which can make the coating more uniform and further reduce the generation of microcracks. Further, in the embodiment of the present invention, the obtained hot-dip coated strip steel can be further cooled by air mist cooling to room temperature. After skin pass rolling and tension leveling, zinc-aluminum-magnesium coated steel sheets with different Zn-Al-Mg-Si-rare earth metal ratios can be obtained.

[0060] In the second aspect, the present invention also provides a zinc-aluminum-magnesium coated steel sheet, including a strip steel sheet and a hot-dip coating formed on the surface of the strip steel sheet. It is prepared by applying the above strip steel hot-dip coating process. By mass percentage of the hot-dip coating, it includes 1 - 12wt% of aluminum, 0.5 - 5.5wt% of magnesium, 0.1 - 1wt% of silicon, and 0.05 - 0.14wt% of rare earth metal, and the balance is Zn and impurities.

[0061] Compared with the prior art, the beneficial effects of the zinc-aluminum-magnesium coated steel sheet of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here.

[0062] Further, the hot-dip coating layer includes a MgZn2 alloy phase and a Mg2Zn 11 alloy phase, wherein the Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) has a relative proportion of 60% to 100%.

[0063] Compared with the prior art, when the relative mass proportion of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) in the hot-dip coating layer is 60% to 100% through the above technical solution, a zinc-aluminum-magnesium coated steel sheet with better anti-corrosion performance, ductility and toughness can be obtained, which is more suitable for the processing and use of the zinc-aluminum-magnesium coated steel frame of photovoltaic modules.

[0064] In the third aspect, the present invention also provides a frame for a photovoltaic module, which is prepared by using the above zinc-aluminum-magnesium coated steel sheet. Specifically, the frame for a photovoltaic module can be prepared by referring to the following forming process: obtaining a zinc-aluminum-magnesium coated steel sheet, and processing the zinc-aluminum-magnesium coated steel sheet through machining processes such as cutting, leveling, cold pressing and bending, and deburring to prepare the frame for a photovoltaic module.

[0065] Compared with the prior art, the beneficial effects of the frame for a photovoltaic module of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here.

[0066] In the fourth aspect, the present invention also provides a photovoltaic module, including the above frame for a photovoltaic module.

[0067] Compared with the prior art, the beneficial effects of the photovoltaic module of the present invention are the same as those of the strip hot-dip coating process described in the above technical solution, and will not be elaborated here.

[0068] Further, the present invention embodiment also provides a method for evaluating the Mg2Zn 11 content in the zinc-aluminum-magnesium coated steel sheet processed by hot-dip coating:

[0069] First, obtain a high-resolution XRD pattern through an X-ray diffractometer.

[0070] X-ray diffraction measurement conditions: the light source is a copper target (Cu, Kα1, λ = 0.154056 nm), the measurement voltage is 20 KV to 40 KV, the current is 100 mA, the measurement range (2Theta) is 5 - 55°, stepwise scanning is 0.02° / step, and each step stays for 1 second or 2 seconds.

[0071] Secondly, perform phase analysis on the obtained spectrum, determine the ideal crystal structure, and import it into the structure refinement software.

[0072] Finally, through fitting calculations, determine the mass percentage content of each metal compound, where the content of Mg2Zn 11 is a, and the content of MgZn2 is b. Then the relative proportion x of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) is x = a / (a + b) × 100%.

[0073] When 0 ≤ x ≤ 20, the content of Mg2Zn 11 is defined as --;

[0074] When 20 < x ≤ 40, the content of Mg2Zn 11 is defined as -;

[0075] When 40 < x ≤ 60, the content of Mg2Zn 11 is defined as +;

[0076] When 60 < x ≤ 80, the content of Mg2Zn 11 is defined as ++;

[0077] When 80 < x ≤ 100, the content of Mg2Zn 11 is defined as +++.

[0078] The larger the proportion of Mg2Zn 11 , the better the ductility but the lower the hardness.

[0079] Hardness evaluation method for zinc-aluminum-magnesium coated steel sheet:

[0080] Use a micro Vickers hardness tester to measure the hardness (H min , H max , H c ) of the surface layer of the pure zinc, pure MgZn2 alloy, and the zinc-aluminum-magnesium coated steel sheet obtained by hot-dip plating respectively. The test force range is 20 grams to 100 grams, and the load time is 10 seconds.

[0081] Hardness ratio y = (Hc - Hmin) / (Hmax - Hmin) × 100%.

[0082] When y ≤ 10, the hardness of the coated steel sheet is defined as grade I;

[0083] When 10 < y ≤ 20, the hardness of the coated steel sheet is defined as grade II;

[0084] When 20 < y ≤ 30, the hardness of the coated steel sheet is defined as grade III;

[0085] When 30 < y ≤ 40, the hardness of the coated steel sheet is defined as grade IV;

[0086] When 40 < y ≤ 80, the hardness of the coated steel sheet is defined as grade V.

[0087] Microcrack evaluation method:

[0088] The zinc-aluminum-magnesium coated steel sheet with the same coating composition and immersion plating conditions is denoted as the N-number coated steel.

[0089] On the zinc-aluminum-magnesium coated steel sheet after hot dip plating, a total of five 100 mm × 50 mm zinc-aluminum-magnesium coated steel sheet segments are intercepted, and each is subjected to 0T cold bending. On each segment of the sample sheet, a bending area is randomly selected, and the fracture size of the coating microcracks on the bent surface is measured. During measurement, the bent area is observed under magnification (50 - 200 times), the fracture spacing of the microcracks is measured, and the fracture size can be obtained by converting with the corresponding scale. Five areas are measured for each segment.

[0090] The simple arithmetic mean of the maximum gap sizes measured for a total of 25 areas of the 5 segments is denoted as

[0091] For all the gap sizes measured for a total of 25 areas of the 5 segments, after deducting the 25 maximum gap sizes, the simple arithmetic mean is denoted as

[0092] Then the microcrack rating of the coated steel sheet is as follows:

[0093] When the rating is excellent;

[0094] When the rating is excellent -;

[0095] When the rating is good;

[0096] When the rating is medium;

[0097] When the rating is poor.

[0098] The present invention will be specifically described below through embodiments. The content of the present invention is not limited to the following embodiments.

[0099] The cold-rolled carbon steel with a thickness of 0.8 mm is used as the base steel sheet, and the zinc-aluminum-magnesium coated steel sheet is made under the conditions described in Table 1 by using the above hot dip plating process flow, and the coating amount is controlled at about 200 g / m 2 .

[0100] Example 1

[0101] A hot dip plating process for the strip steel of the photovoltaic module frame is as follows:

[0102] S1. Refine aluminum alloy ingots according to the above-described method, including Al-Si alloy, Al-rare earth alloy, and Al-Mg alloy; among them, the Si content of the Al-Si alloy is about 16 wt%, the rare earth content of the Al-rare earth alloy is about 10 wt%, and the Mg content of the Al-Mg alloy is about 40 wt%. Further, the rare earth elements in the Al-rare earth alloy are a lanthanum-cerium mixture, that is, the lanthanum-cerium mixture accounts for about 10 wt% of the total mass of the Al-rare earth alloy. The lanthanum-cerium mixture selected in this example is a commercially available product.

[0103] S2. Prepare a hot-dip galvanizing solution with 12 wt% Al, 5.5 wt% Mg, 1.0 wt% Si, 0.14 wt% rare earth metal, and the rest being Zn and unavoidable impurities; add the weighed zinc ingots to the zinc pot and heat it to above 500 °C to completely melt it. Heat the zinc solution to 660 °C, place the previously refined Al-rare earth metal alloy, Al-Si alloy, and Al-Mg alloy in a graphite bell and quickly press it into the zinc solution to completely immerse it. During the melting process of the alloy, stir well to make the components in the zinc solution evenly distributed. After complete melting, continue stirring for 10 minutes and keep the temperature of the zinc solution at 480 °C.

[0104] S3. Hot-dip galvanizing of strip steel: Unroll the strip steel, transfer it to the annealing furnace after degreasing with alkali washing, rust removal with acid pickling, and drying steps; heat it to 490 °C in a reducing atmosphere, immerse the strip steel into the zinc solution at 480 °C through the furnace nose for 3 seconds of hot-dip galvanizing; pull out the strip steel that has completed hot-dip galvanizing from the zinc solution, blow it with a nitrogen air knife and cool it (the cooling rate is about 20 °C / second to 50 °C / second), and cool it down to about 355 °C; transfer the above hot-dip galvanized strip steel to the alloying furnace and keep it at 355 °C for 30 seconds; then, gradually cool the hot-dip galvanized strip steel in the alloying furnace (the cooling rate is about 60 °C / second), control the temperature of the strip steel when it reaches the top turning roll to be below 220 °C, cool the strip steel to room temperature through aerosol cooling, and then obtain a zinc-aluminum-magnesium coated steel sheet through skin pass rolling and tension leveling. The results are shown in Table 1.

[0105] Example 2

[0106] Implement according to the process described in Example 1,

[0107] The difference is that in S2, the Al content is 9 wt%, the Mg content is 3.5 wt%, the Si content is 0.8 wt%, the rare earth metal content is 0.12 wt%, and the rest are Zn and unavoidable impurities; the temperature of the zinc solution is kept at 465 °C;

[0108] In S3, the heating temperature of the strip steel is 475 °C; the holding temperature is 345 °C; the holding time is 15 seconds; the cooling rate is 40 °C / second. The results are shown in Table 1.

[0109] Example 3

[0110] Implement according to the process described in Example 1,

[0111] The difference is that in S2, the Al content is 6 wt%, the Mg content is 5.5 wt%, the Si content is 0.6 wt%, the rare earth metal content is 0.1 wt%, and the rest is Zn and inevitable impurities; the temperature of the zinc bath is maintained at 440 °C;

[0112] In S3, the heating temperature of the strip is 450 °C; the holding temperature is 350 °C; the hot-dip plating time is 10 seconds; the holding time is 5 seconds; the cooling rate is 20 °C / second. The results are shown in Table 1.

[0113] Example 4

[0114] Implement according to the process described in Example 1,

[0115] The difference is that in S2, the Al content is 1 wt%, the Mg content is 0.5 wt%, the Si content is 0.1 wt%, the rare earth metal content is 0.05 wt%, and the rest is Zn and inevitable impurities; the temperature of the zinc bath is maintained at 410 °C;

[0116] In S3, the heating temperature of the strip is 420 °C; the holding temperature is 335 °C; the hot-dip plating time is 5 seconds; the holding time is 10 seconds; the cooling rate is 5 °C / second. The results are shown in Table 1.

[0117] Comparative Example 1

[0118] Implement according to the process described in Example 1,

[0119] The difference is that in S3, the hot-dip plated strip transferred to the alloying furnace is not subjected to heat preservation treatment, and the results are shown in Table 1.

[0120] Comparative Example 2

[0121] Implement according to the process described in Example 2,

[0122] The difference is that in S3, the hot-dip plated strip transferred to the alloying furnace is not subjected to heat preservation treatment, and the results are shown in Table 1.

[0123] Comparative Example 3

[0124] Implement according to the process described in Example 3,

[0125] The difference is that in S3, the hot-dip plated strip transferred to the alloying furnace is not subjected to heat preservation treatment, and the results are shown in Table 1.

[0126] Comparative Example 4

[0127] Implement according to the process described in Example 4,

[0128] The difference is that in S3, the hot-dip galvanized strip transferred to the alloying furnace is not heat-insulated, and the results are shown in Table 1.

[0129] Comparative Example 5

[0130] Implemented according to the process described in Example 1,

[0131] The difference is that the content of smelting aluminum alloy ingots in S1 is cancelled; in S2, the zinc bath directly submerges magnesium-aluminum-silicon and rare earth metals. In this comparative example, a violent oxidation reaction occurred when a large amount of Mg metal was directly added to the zinc bath, forming a large amount of dross on the surface of the zinc bath, and the plating effect of the strip was extremely poor. Therefore, subsequent tests and ratings were not carried out, and the results are shown in Table 1.

[0132] Comparative Example 6

[0133] Implemented according to the process described in Example 2,

[0134] The difference is that the content of smelting aluminum alloy ingots in S1 is cancelled; in S2, the zinc bath directly submerges magnesium-aluminum-silicon and rare earth metals. In this comparative example, an oxidation reaction occurred when Mg metal was directly added to the zinc bath, forming more dross on the surface of the zinc bath, and the plating effect of the strip was poor. Therefore, subsequent tests and ratings were not carried out, and the results are shown in Table 1.

[0135] Comparative Example 7

[0136] Implemented according to the process described in Example 3,

[0137] The difference is that the content of smelting aluminum alloy ingots in S1 is cancelled; in S2, the zinc bath directly submerges magnesium-aluminum-silicon and rare earth metals. In this comparative example, a violent oxidation reaction occurred when a large amount of Mg metal was directly added to the zinc bath, forming a large amount of dross on the surface of the zinc bath, and the plating effect of the strip was extremely poor. Therefore, subsequent tests and ratings were not carried out, and the results are shown in Table 1.

[0138] Comparative Example 8

[0139] Implemented according to the process described in Example 4,

[0140] The difference is that the content of smelting aluminum alloy ingots in S1 is cancelled; in S2, the zinc bath directly submerges magnesium-aluminum-silicon and rare earth metals. In this comparative example, each component can be mixed with the zinc bath more evenly. The plating effect is almost the same as that of Example 4, and the results are shown in Table 1. Although a good plating effect is achieved in this comparative example, direct addition of a large amount of Mg metal during continuous production may still cause problems such as oxidation reaction and dross. Therefore, this comparative example is not preferred.

[0141] Comparative Example 9

[0142] Implemented according to the process described in Example 1,

[0143] The difference is that the strip is not heat-treated in a reducing atmosphere before hot-dip galvanizing, and the direct hot-dip galvanizing method is adopted. In this comparative example, a large amount of iron on the strip surface is oxidized, and when it enters the zinc bath, it causes a drastic temperature change, cooling the zinc bath. Eventually, the plating effect is extremely poor, so subsequent tests and ratings are not carried out, and the results are shown in Table 1.

[0144] Comparative Example 10

[0145] Implement according to the process described in Example 2.

[0146] The difference is that the strip is not heat-treated in a reducing atmosphere before hot-dip galvanizing, and the direct hot-dip galvanizing method is adopted. In this comparative example, a large amount of iron on the strip surface is oxidized, and when it enters the zinc bath, it causes a drastic temperature change, cooling the zinc bath. Eventually, the plating effect is extremely poor, and subsequent tests and ratings are not carried out, and the results are shown in Table 1.

[0147] Comparative Example 11

[0148] Implement according to the process described in Example 3.

[0149] The difference is that the strip is not heat-treated in a reducing atmosphere before hot-dip galvanizing, and the direct hot-dip galvanizing method is adopted. In this comparative example, a large amount of iron on the strip surface is oxidized, and when it enters the zinc bath, it causes a drastic temperature change, cooling the zinc bath. Eventually, the plating effect is extremely poor, and subsequent tests and ratings are not carried out, and the results are shown in Table 1.

[0150] Comparative Example 12

[0151] Implement according to the process described in Example 4.

[0152] The difference is that the strip is not heat-treated in a reducing atmosphere before hot-dip galvanizing, and the direct hot-dip galvanizing method is adopted. In this comparative example, a large amount of iron on the strip surface is oxidized, and when it enters the zinc bath, it causes a drastic temperature change, cooling the zinc bath. Eventually, the plating effect is extremely poor, and subsequent tests and ratings are not carried out, and the results are shown in Table 1.

[0153] Comparative Example 13

[0154] Implement according to the process described in Example 1.

[0155] The difference is that in S1, the lanthanum-cerium mixture accounts for 18 wt% of the total mass of the Al-rare earth alloy. In this comparative example, the plating effect of the strip is poor, showing powdering and graying phenomena, and the coating film is easy to fall off, not meeting the basic use requirements of zinc-aluminum-magnesium coated steel. Therefore, subsequent tests and ratings are not carried out, and the results are shown in Table 1.

[0156] Table 1

[0157]

[0158]

[0159] For the examples shown in Table 1, the Mg2Zn content, hardness ratio, and microcrack rating before and after heat preservation of zinc-aluminum-magnesium coatings with different components were analyzed. According to the Al-Mg content, they can be divided into 4 groups, namely 1-0.5, 6-5.5, 9-3.5, and 12-5.5. Only the heat preservation conditions were changed for each group, and other hot-dip coating conditions were the same. By comparison, it can be seen that the Mg2Zn content, hardness ratio, and microcrack rating of zinc-aluminum-magnesium coatings with different components all change before and after heat preservation. Especially for zinc-aluminum-magnesium coatings with an Al content higher than 9 wt%, after heat preservation for 15 s - 30 s, due to the significant increase in the Mg2Zn content, the microcrack rating is greatly improved, but the hardness only drops from IV to III. The comprehensive performance of hardness and ductility of this kind of zinc-aluminum-magnesium coating is better, and it is more suitable for the processing and use of the zinc-aluminum-magnesium coating steel frame of photovoltaic modules. 11 In the present invention, the solid waste silicon material generated during the manufacturing process of crystalline silicon cells is used as Si in the coating. This substitution highly valorizes the solid waste (silicon material, silicon powder) generated in the production process of crystalline silicon cells. It reduces the refining cost of Al-Si alloy ingots. It improves the corrosion resistance of zinc-aluminum-magnesium coated alloy steel and reduces the coating thickness. After being blown by an air knife, heat preservation is first carried out for a period of time, and then gradual cooling is carried out to form a zinc-aluminum-magnesium coated steel. By adding the heat preservation process, Mg2Zn and MgZn2 metal compounds can coexist in the coating. By carrying out heat preservation for different times, the ratio of the above two metal compounds can be adjusted. Therefore, when the zinc-aluminum-magnesium coated steel plate is processed into a steel frame, microcracks can be avoided, and the corrosion resistance is not significantly affected. 11 In particular, for zinc-aluminum-magnesium coatings with an Al content higher than 9 wt%, after heat preservation for 15 s - 30 s, due to the significant increase in the Mg2Zn content, the microcrack rating is greatly improved, but the hardness only drops from IV to III. 11 The comprehensive performance of hardness and ductility of this kind of zinc-aluminum-magnesium coating is better, and it is more suitable for the processing and use of the zinc-aluminum-magnesium coating steel frame of photovoltaic modules.

[0160] In the present invention, the solid waste silicon material generated during the manufacturing process of crystalline silicon cells is used as Si in the coating. This substitution highly valorizes the solid waste (silicon material, silicon powder) generated in the production process of crystalline silicon cells. It reduces the refining cost of Al-Si alloy ingots. It improves the corrosion resistance of zinc-aluminum-magnesium coated alloy steel and reduces the coating thickness. After being blown by an air knife, heat preservation is first carried out for a period of time, and then gradual cooling is carried out to form a zinc-aluminum-magnesium coated steel. By adding the heat preservation process, Mg2Zn 11 and MgZn2 metal compounds can coexist in the coating. By carrying out heat preservation for different times, the ratio of the above two metal compounds can be adjusted. Therefore, when the zinc-aluminum-magnesium coated steel plate is processed into a steel frame, microcracks can be avoided, and the corrosion resistance is not significantly affected.

[0161] In addition, in the strip hot-dip coating process of the present invention, by controlling the mass percentage of rare earth metals in the Al-rare earth metal alloy to be 5 - 15 wt%, the mass percentage of silicon in the Al-Si alloy to be 10 - 20 wt%, and the mass percentage of magnesium in the Al-Mg alloy to be 35 - 45 wt%, the content of each component in the prepared hot-dip galvanizing solution can reach 1 - 12 wt% of aluminum, 0.5 - 5.5 wt% of magnesium, 0.1 - 1 wt% of silicon, and 0.05 - 0.14 wt% of rare earth metals, with the balance being Zn and impurities. Under the above ratio, combined with the heat preservation control program of the present invention, the relative proportion of Mg2Zn and MgZn2 metal compounds in the prepared coating can reach Mg2Zn 11 / (MgZn2 + Mg2Zn 11 / (MgZn2 + Mg2Zn 11) is 60% to 100%, so that the obtained coating has excellent ductility, the microcrack rating is greatly improved, and it is more suitable for the processing and use of the zinc-aluminum-magnesium coated steel frame of photovoltaic modules.

[0162] As described above, it is only the specific implementation manner of this application, but the protection scope of this application is not limited thereto. Any person skilled in the art within the technical scope disclosed in this application can easily think of changes or substitutions, which should all be covered within the protection scope of this application. Therefore, the protection scope of this application should be subject to the protection scope of the said claims.

Claims

1. A hot-dip galvanizing process for strip steel, characterized in that, The following steps are involved: Refining master alloy ingots, including Al-Si alloys, Al-rare earth metal alloys and Al-Mg alloys; Immersing the refined master alloy ingot in zinc liquid and stirring it to obtain a Zn-Al-Mg-Si-rare earth metal hot-dip galvanizing liquid; Immersing the steel strip in the hot-dip galvanizing solution for hot-dip galvanizing; The hot-dip coated steel strip is subjected to a first cooling process to reduce the temperature to 335° C. to 355° C., kept at this temperature for 15S to 30S, and then subjected to a second cooling process to reduce the temperature to below 220° C., thereby obtaining a zinc-aluminum-magnesium coated steel plate.

2. The hot-dip galvanizing process for strip steel according to claim 1, characterized in that, The mass percentage of silicon in the Al-Si alloy is 10-20wt%; and / or, The mass percentage of rare earth metal in the Al-rare earth metal alloy is 5-15wt%; and / or, The mass percentage of magnesium in the Al-Mg alloy is 35-45wt%.

3. The hot-dip galvanizing process for strip steel according to claim 1, characterized in that, Calculated by mass percentage of the hot-dip galvanizing solution, the hot-dip galvanizing solution includes 1-12wt% of aluminum, 0.5-5.5wt% of magnesium, 0.1-1wt% of silicon and 0.05-0.14wt% of rare earth metals, and the remainder is Zn and impurities.

4. The hot-dip galvanizing process for strip steel according to claim 3, wherein Calculated by mass percentage of the hot-dip galvanizing solution, the hot-dip galvanizing solution includes 9-12wt% of aluminum, 3.5-5.5wt% of magnesium, 0.8-1wt% of silicon and 0.12-0.14wt% of rare earth metals, and the remainder is Zn and impurities.

5. The hot-dip galvanizing process for strip steel according to any one of claims 1 to 4, characterized in that, The rare earth metal is lanthanum and / or cerium.

6. The hot dip galvanizing process for strip steel according to any one of claims 1 to 4, characterized in that, The cooling rate of the first cooling is 20°C / sec to 50°C / sec; and / or, The second cooling has a cooling rate of 5° C. / sec to 100° C. / sec.

7. The hot-dip galvanizing process for strip steel according to claim 1, characterized in that, The step of completely immersing the refined intermediate alloy ingot in zinc liquid and stirring it evenly to obtain a hot-dip galvanizing solution of Zn-Al-Mg-Si-rare earth metal comprises: Heat the zinc ingot to above 500°C to melt it, and then raise the temperature to 660°C to 680°C; Press the refined Al-Si alloy, Al-rare earth metal alloy and Al-Mg alloy into the zinc liquid until they are completely immersed; During the melting process of the master alloy ingot, the ingot is fully stirred to ensure that the components in the zinc liquid are evenly distributed.

8. A zinc-aluminum-magnesium coated steel sheet, comprising a strip steel sheet and a hot-dip coating formed on the surface of the strip steel sheet, characterized in that, The hot-dip coating is prepared by the hot-dip coating process for steel strip according to any one of claims 1 to 7, and comprises, by mass percentage, 1-12wt% aluminum, 0.5-5.5wt% magnesium, 0.1-1wt% silicon and 0.05-0.14wt% rare earth metals, with the remainder being Zn and impurities.

9. The hot-dip galvanized Al-Zn-Mg coated steel sheet according to claim 8, wherein, The hot-dip coating layer comprises a MgZn2 alloy phase and a Mg2Zn 11 alloy phase, wherein the relative mass ratio of Mg2Zn 11 / (MgZn2 + Mg2Zn 11 ) is 60% to 100%.

10. A frame for a photovoltaic module, characterized in that, The zinc-aluminum-magnesium coated steel sheet is prepared using the zinc-aluminum-magnesium coated steel sheet as described in claim 8 or 9.

11. A photovoltaic module, characterized in that, Including the frame for photovoltaic components as claimed in claim 10.

Images