Preparation process of full-specification economical photovoltaic steel and product prepared by the process

Abstract

The application discloses a preparation process of full-specification economical photovoltaic steel and a product prepared by the process, and belongs to the technical field of hot-dip plating product manufacturing. The manufacturing steps of the photovoltaic steel are as follows: steelmaking, hot rolling, cold rolling, welding, annealing, hot-dip plating, finishing, passivation and coiling. The structure state of the hot-dip plating base material is selected according to the thickness of the strip steel. When the thickness of the strip steel is less than 2.0 mm, the proportion of deformed ferrite in the base material structure is more than 75%, and 3-8% carbide and the balance of pearlite are further contained; when the thickness of the strip steel is more than or equal to 2.0 mm, the proportion of equiaxed ferrite in the base material structure is more than 80%, and 1-5% carbide and the balance of pearlite are further contained. Through the control of the processes such as welding, annealing and hot-dip plating, the full-specification photovoltaic steel is produced at low cost, stably and continuously and efficiently, and the prepared photovoltaic steel meets the requirements of customers on surface quality and processing performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of hot-dip plating product manufacturing, and more particularly relates to a preparation process of an economic full-spec photovoltaic steel and a product prepared by the process. BACKGROUND

[0002] In recent years, the installed capacity of photovoltaics has increased exponentially, and photovoltaic supports, an important component of photovoltaics, are required to have high corrosion resistance. The required material thickness is concentrated in 1.5-3.5 mm, and mainly includes hot-rolled plates, hot-dip galvanized plates, and hot-dip zinc-aluminum-magnesium plates. To meet the use requirements of photovoltaic supports, the manufacturing methods of the above materials and the existing problems are as follows: (1) the hot-rolled plates are made into parts and then subjected to post-dip plating to obtain good corrosion resistance, but there are problems of poor environmental friendliness, thick plating layer, and high cost; (2) the hot-rolled plates form a stable oxide layer by adding expensive metal materials to achieve the purpose of simulated corrosion, but there is a problem of high cost; (3) the hot-dip galvanized plates have poor corrosion resistance, and the thickness of the plating layer is increased to 800-1000 g / m 2 , not only causing waste of zinc resources, but also being high in cost; (4) the hot-dip zinc-aluminum-magnesium plates have good corrosion resistance, and thin specifications are manufactured using cold-rolled substrates. To meet the demand for thick specifications of zinc-aluminum-magnesium products for photovoltaics, several hot-base zinc-aluminum-magnesium units have been added in China in recent years, but the investment cost is high, low-cost and efficient production of different specifications of materials cannot be realized, and the use of low-cost alloys and processes cannot meet the requirements of high strength. In view of the above problems, the present application provides a continuous hot-dip plating method of an economic photovoltaic steel, which realizes low-cost and continuous efficient production of photovoltaic steels of different thickness specifications on existing units.

[0003] For example, patent CN116710585A discloses a high-strength hot-dip galvanized steel plate with excellent plating adhesion and weldability and a manufacturing method thereof. The hot-dip galvanized steel plate has a base steel plate and a hot-dip galvanized layer formed on one side or both sides of the base steel plate. The base steel plate contains, in terms of weight %, C: 0.1-0.3 %, Si: 0.1-2.0 %, Al: 0.1-1.5 %, Mn: 1.5-3.0 %, and the balance of Fe and inevitable impurities. The patent has a high Mn content. For another example, patent CN107699794A provides a low-cost hot-dip galvanized steel plate and a preparation method thereof. The chemical composition of the hot-dip galvanized steel plate is as follows: in terms of weight percentage, C: 0.03-0.08 %, Si: 0.08-0.20 %, Mn: 0.60-1.1 %, P: 0.010-0.040 %, S: ≤0.015 %, Als: 0.020-0.060 %, Nb: 0.020-0.050 %, and the balance of Fe and inevitable impurities. The steel plate contains Nb, which is relatively high in price. In the above patents, the amount of metal elements added is large, and the economy is not strong.

[0004] For example, patent CN105316612A discloses a production method of continuous hot galvanized product, including: determining the parameter information of zinc liquid and steel plate before galvanizing. The first batch of steel plates with a thickness range of 0.25-2.50 mm are immersed in a zinc pot for galvanizing treatment to generate large zinc flower steel plates; the weight of the first batch of steel plates is determined by a first proportioning formula; the second batch of steel plates with a thickness range of 0.25-2.50 mm are immersed in a zinc pot for galvanizing treatment to generate small zinc flower steel plates; the weight of the second batch of steel plates is determined by a second proportioning formula; the third batch of steel plates with a thickness range of 0.25-0.80 mm are immersed in a zinc pot for galvanizing treatment to generate fine zinc flower steel plates; the weight of the third batch of steel plates is determined by a third proportioning formula; the fourth batch of steel plates with a thickness range of 0.25-2.50 mm are immersed in a zinc pot for galvanizing treatment to generate zinc flower-free steel plates; the weight of the fourth batch of steel plates is determined by a fourth proportioning formula. However, this patent is mainly to control zinc flowers, and the method does not involve specifications above 2.5 mm, and does not involve economic control.

[0005] For example, patent CN116288098A provides a coating method for hot-based galvanized sheet. This patent mainly solves the technical problem of zinc fluctuation on the surface of hot-based galvanized sheet above 3.0 mm, and does not involve the control of hot-dip plating of thinner specifications. Patent CN103911544A provides a low-cost thick-gauge low-alloy structural steel and a production method thereof. It is mainly a control method for hot-rolled sheets above 4 mm in specification. Patent CN109072327A provides a method for manufacturing cold-rolled steel sheets, and the sheets manufactured thereby. This invention mainly relates to a manufacturing method for cold-rolled steel sheets with a thickness of 0.5 mm to 3 mm. None of the above patents involves a hot-dip galvanizing process.

[0006] Other patents such as CN116288097A, CN109371321A, CN103103467A, CN109852883A, CN108480416A, CN101255541A, CN104862629A, etc. are galvanizing methods for high-strength hot-rolled steel sheets, which achieve the purpose by controlling continuous casting, pickling or annealing, and cannot achieve low-cost and efficient hot-dip plating production of photovoltaic steel with different thickness specifications.

[0007] From the above analysis, it can be seen that the existing technology does not involve an economic manufacturing method for full-specification photovoltaic hot-dip plated steel. SUMMARY

[0008] 1. Problem to be solved

[0009] In order to solve the problem that the prior art cannot balance the quality of full-specification photovoltaic steel, the application provides a preparation process of full-specification economic photovoltaic steel, and the photovoltaic steel prepared by the method has qualified mechanical properties, good surface quality and forming performance.

[0010] 2. Technical scheme

[0011] In order to solve the above problems, the technical scheme adopted by the application is as follows:

[0012] The application provides a preparation process of full-specification economic photovoltaic steel, characterized by the following manufacturing steps of the photovoltaic steel:

[0013] 1) Steelmaking;

[0014] 2) Hot rolling;

[0015] 3) Cold rolling;

[0016] 4) Welding;

[0017] 5) Annealing;

[0018] 6) Hot dipping;

[0019] 7) Finishing;

[0020] 8) Passivation;

[0021] 9) Coiling.

[0022] In step 1), the components of steelmaking include, by mass fraction: C 0.02% to 0.08%, Si≤0.06%, Mn 0.2% to 0.8%, P≤0.025%, S≤0.012%, Als 0.02% to 0.06%, Ti 0.03% to 0.08%, N≤0.004%, and simultaneously satisfying 0.02%≤[Ti-3.4N-3S]≤0.05%.

[0023] In step 2), the hot rolling process is as follows: the discharge temperature is 1200-1250℃, the final rolling temperature is 860-900℃, and the coiling temperature is 600-640℃.

[0024] In step 3), the cold rolling process is as follows: when the strip thickness is <2.0mm, 3000t≤cold rolling rolling force≤5000t; and when the strip thickness is≥2.0mm, 100t≤cold rolling rolling force≤300t.

[0025] The hot dipping base material of step 3) controls different base material organization states according to the strip thickness: when the strip thickness is <2.0mm, the proportion of deformed ferrite in the base material organization is more than 75%; and when the strip thickness is≥2.0mm, the proportion of equiaxed ferrite in the base material organization is more than 80%.

[0026] When the thickness of the hot-dip plated base material in step 3) is less than 2.0 mm, the deformed ferrite in the base material structure preferably accounts for more than 85%, and the base material structure further contains 3% to 8% carbide and the balance pearlite; when the thickness is greater than or equal to 2.0 mm, the equiaxed ferrite in the base material structure preferably accounts for 85% to 95%, and the base material structure further contains 1% to 5% carbide and the balance pearlite.

[0027] In the structure of the hot-dip plated base material in step 3), the carbide is one or more of TiC, Ti(CN) and Ti4C2S2, and the size is less than or equal to 20 nm; when the thickness of the strip steel is less than 2.0 mm, the carbide is dispersedly distributed in the crystal; and when the thickness of the strip steel is greater than or equal to 2.0 mm, the carbide is distributed along the grain boundary.

[0028] In step 4), the welding wheel pressure is 12 to 20 KN, the lap joint amount is 19 to 29 mm, and when the thickness of the base material is less than 2.0 mm, the welding speed is 17 to 21 m / min, the welding current is 26 to 30 KA, and the welding temperature is 950 to 1000 ℃; when the thickness of the base material is less than 2.0 mm and the thickness of the base material is greater than or equal to 2.0 mm, the welding speed is 13 to 16 m / min, the welding current is 21 to 25 A, and the welding temperature is 800 to 900 ℃; and when the thickness of the base material is greater than 2.0 mm, the welding speed is 8 to 12 m / min, the welding current is 15 to 20 KA, and the welding temperature is 900 to 950 ℃.

[0029] In step 5), the annealing temperature is 680 to 740 ℃, and when the thickness of the strip steel is less than 2.0 mm, the annealing speed is greater than or equal to 70 m / min; and when the thickness of the strip steel is greater than or equal to 2.0 mm, the annealing speed is greater than or equal to 63 m / min, and the thickness of the strip steel t, the annealing temperature T and the annealing speed v satisfy the formula: t < 0.106T-v < t+6.

[0030] In step 6), the composition of the hot-dip galvanizing liquid is 1% to 6% Al, 1% to 3% Mg and the balance Zn, and the hot-dip galvanizing temperature is 430 to 460 ℃.

[0031] In step 7), the finish elongation rate is 0.5% to 1.2%.

[0032] In step 8), the passivation is one of inorganic passivation, organic passivation and inorganic-organic composite passivation.

[0033] In step 9), the steel coil after coiling is packaged when the temperature is less than or equal to 40 ℃.

[0034] The present application realizes the preparation of full-specification economical photovoltaic hot-dip plated steel plates through the common control of chemical composition and process conditions, which is based on the following principles:

[0035] (1) Chemical composition control:

[0036] Carbon (C): C is an important solid solution strengthening element in steel, and when the content of C is more than 0.08%, it is located in the peritectic zone, and the casting blank needs to be cleaned, and the cost is high, and when C is too little, TiC particles cannot be formed with Ti, and the strengthening effect cannot be played. Therefore, in the application, the content of C element is 0.02% to 0.08%, and preferably controlled to be 0.03% to 0.07%.

[0037] Silicon (Si): Si has a strong strengthening effect in steel, and when the content of Si is too low, the strengthening effect is not obvious, but when the content of Si is too high, oxides are formed, which reduces the coating property of the steel plate. Therefore, the content of Si element in the application is controlled to be ≤0.06%, and preferably controlled to be ≤0.03%.

[0038] Manganese (Mn): Mn is the most effective element to improve strength, but when Mn is too much, it is easy to cause the segregation degree to increase in the continuous casting process, which causes the appearance of banded structure, and affects the plasticity, welding performance and fatigue performance of the material. Therefore, low Mn control is adopted in the application, and the content of Mn element is controlled to be 0.2% to 0.8%, and preferably controlled to be 0.4% to 0.6%.

[0039] Phosphorus (P): P is an inevitable harmful impurity in steel, which affects the stamping performance, secondary processing brittleness and the like of the material, and the content of P element in steel should be strictly controlled. Therefore, the content of P element in the application is ≤0.025%, and preferably controlled to be ≤0.015%.

[0040] Sulfur (S): S is an inevitable harmful impurity in steel, and too much S will form MnS inclusions with Mn, which seriously affects the surface quality of the product, and has adverse effects on the welding performance, cold bending performance and toughness of the steel, and the content of S element in steel should be strictly controlled. Therefore, the content of S element in the application is controlled to be ≤0.012%, and preferably controlled to be ≤0.008%.

[0041] Aluminum (Al): Al is added for deoxidization, and when the content of Als is low, its effect cannot be fully played; on the other hand, too much Al is easy to form alumina inclusions. Therefore, the content of Als element in the application is 0.02% to 0.06%, and preferably controlled to be 0.035% to 0.055%.

[0042] Nitrogen (N): N can improve the strength of steel, but when it is too high, AlN low-melting-point compound will be formed with Als, and AlN will continuously precipitate at the austenite grain boundary in the edge and corner regions of the casting blank, which causes the local plasticity of the slab to decrease, and is easy to produce hot cracks, and will reduce the effective Ti in the steel. Therefore, the content of N element in the application is controlled to be ≤0.004%, and preferably controlled to be ≤0.002%.

[0043] Titanium (Ti) element and [Ti-3.4N-3S]: The Ti element can refine the grain and improve the strength of the steel, but the activity of the Ti element is strong, and it is easy to react with O, S and N in the steel, which will consume part of the Ti. When the effective Ti in the steel, that is, [Ti-3.4N-3S] < 0, the Ti element has been completely consumed and cannot combine with elements such as C in the subsequent rolling process to play a role in precipitation strengthening. When the Ti element is too high, the precipitates are uneven, causing large performance fluctuations; when the [Ti-3.4N-3S] is too low, it cannot effectively play a role in precipitation strengthening. Therefore, the Ti element is controlled to be 0.03% to 0.08%, preferably the Ti element is controlled to be 0.035% to 0.075%, and at the same time, 0.02% ≤ [Ti-3.4N-3S] ≤ 0.05%, the Ti element can achieve the desired strengthening effect.

[0044] (2) Economic control:

[0045] The present application uses single Ti composition, which reduces the alloy cost; secondly, the C element is controlled outside the peritectic zone, avoiding cleaning of casting billet cracks, which can be hot charged and hot sent, reducing the process cost; further, the same composition group is produced for full-specification steel strips, avoiding small pouring steelmaking and batch production, improving production efficiency and reducing cost.

[0046] Further, the same hot rolling process is used for full-specification steel strips to achieve efficient group production, control different base material organizations to realize continuous hot-dip plating production of full-specification photovoltaic steel, avoid investment cost of new unit, and at the same time, reduce the problem of unable to uniformly produce and quickly deliver different thickness steel strips produced by different units.

[0047] Further, when the thickness of the steel strip t < 2.0mm, the cold rolling rolling force is controlled to be ≥ 3000t, so that the proportion of deformed ferrite in the base material organization is more than 75%, preferably the cold rolling rolling force is controlled to be > 3600t, so that the proportion of deformed ferrite in the base material organization is more than 85%, which can increase the cold rolling deformation energy storage, reduce the recrystallization annealing temperature, use a lower annealing temperature to meet the performance requirements, reduce the energy consumption cost of the annealing process, and at the same time, to reduce the rolling roll wear in the cold rolling process, the cold rolling rolling force is controlled to be ≤ 5000t; when t ≥ 2.0mm, when there is more deformed ferrite in the base material organization, a slower process speed must be ensured in the continuous hot-dip galvanizing process to complete the recovery and recrystallization, and the zinc-aluminum-magnesium product coating of the photovoltaic product is 275g / m 2Therefore, the present application controls the cold rolling rolling force to be greater than or equal to 100t when the strip thickness t is greater than or equal to 2.0mm, so that the proportion of the equiaxed ferrite in the substrate structure is greater than or equal to 80%, preferably greater than or equal to 85%, thereby significantly increasing the strip speed during continuous hot galvanizing and reducing the occurrence of defects. Meanwhile, the present inventor has found that when the proportion of the equiaxed ferrite in the substrate structure is greater than 95%, the strength control is not good. Therefore, the present application controls the proportion of the equiaxed ferrite in the substrate structure to be less than or equal to 95% when the strip thickness t is greater than or equal to 2.0mm, and controls the cold rolling rolling force to be less than or equal to 300t.

[0048] Further, during continuous hot dipping, the weld quality is very important, and weld cracking can easily cause strip breakage and other production accidents. Therefore, the present application controls different welding processes according to the different substrate structures of different specifications:

[0049] a. When the welding wheel pressure and the overlap amount are too small, the weld is prone to false welding and cracking. When the welding wheel pressure and the overlap amount are too large, the weld is not easy to penetrate, and is prone to cracking under tension. Therefore, the present application controls the welding wheel pressure to be 12-20KN and the overlap amount to be 19-29mm;

[0050] b. When the thickness of the specifications to be welded is less than 2.0mm, the proportion of the deformed ferrite in the substrate is high, and the strength is high, so a large amount of welding heat input is required. Meanwhile, in order to match the annealing speed of the process section, the present application controls the welding speed to be 17-21m / min, which is equivalent to reducing the heat input time. Therefore, the present application controls the welding current to be 26-30KA and the welding temperature to be 950-1000℃, so as to maintain a high welding heat input;

[0051] c. When the thickness of the specifications to be welded is less than 2.0mm and the thickness of the specifications to be welded is greater than or equal to 2.0mm, the substrate on one side is deformed ferrite, and the substrate on the other side is equiaxed ferrite, so a medium amount of welding heat input is required. Therefore, the present application controls the welding speed to be 13-16m / min, the welding current to be 21-25A, and the welding temperature to be 800-900℃;

[0052] d. When the thickness of the specifications to be welded is greater than 2.0mm, the proportion of the equiaxed ferrite in the substrate is high, and the annealing speed of the process section is relatively low. Therefore, the present application controls the welding speed to be 8-12m / min, which undoubtedly increases the welding heat input time. Therefore, the present application has found that controlling the welding current to be 15-20KA and the welding temperature to be 900-950℃ can ensure that the heat input at this time meets the welding requirements. Through the control of the above welding parameters, good weld quality is achieved, and efficient and stable hot dipping is achieved.

[0053] Further, different thickness specifications adopt similar annealing temperature to reduce the concession loss cost caused by temperature transition coil.

[0054] (3) Performance and surface quality joint control:

[0055] Firstly, 0.02%≤[Ti-3.4N-3S]≤0.05% is adopted to realize good precipitation strengthening effect, so as to meet the performance requirement.

[0056] Further, the temperature of discharging is controlled to be 1200-1250 DEG C, and the coiling temperature is controlled to be 600-640 DEG C, so that the precipitation amount of Ti reaches the maximum, and the precipitation strengthening is maximized; and secondly, the finish rolling temperature is controlled to be 860-900 DEG C, so as to refine the grain and realize the strengthening.

[0057] When the substrate thickness is less than 2.0 mm, the deformed ferrite accounts for more than 75%, the cold rolling deformation storage energy is small, the recrystallization driving force is small, a higher temperature is needed for recrystallization, when annealing at 680-740 DEG C, the material is in a non-complete recrystallization state, which leads to that the elongation rate is not qualified, and the processing cracking problem is prone to occur, therefore, the deformed ferrite accounts for more than 75% when the substrate thickness is less than 2.0 mm in the present application, preferably more than 85%; when the substrate thickness is more than 2.0 mm, in order to reduce the recovery recrystallization time, improve the production line speed and improve the surface quality, the equiaxed ferrite accounts for more than 80% in the substrate structure, preferably more than 85%, but when the account is too high, the substrate strength is too small, the finished product strength is prone to not meet the requirement, and the size is prone to not meet the requirement during forming.

[0058] Secondly, the carbide in the present application is one of TiC, Ti(CN) and Ti4C2S2 and above, and the size is less than or equal to 20 nm, so as to realize good precipitation strengthening effect and meet the strength requirement. Furthermore, when the precipitated carbide is less, the strength does not meet the requirement, and when the precipitated carbide is more, the performance fluctuates greatly in the width and length of the strip steel, and the processing is prone to be poor, therefore, the carbide in the substrate structure is controlled to be 3%-8% when the substrate thickness is less than 2.0 mm, and the carbide in the substrate structure is controlled to be 1%-5% when the substrate thickness is more than 2.0 mm. Finally, the distribution state of the carbide is controlled, when the substrate thickness is less than 2.0 mm, the carbide is controlled to be distributed in the grain interior, so as to reduce the hindering to the recrystallization process when the carbide is located at the grain boundary, and the annealing temperature is reduced; when the substrate thickness is more than 2.0 mm, the carbide is controlled to be located at the grain boundary, because most of the structure is equiaxed ferrite, the grain changes little during the annealing process, the carbide migrates at the grain boundary, on one hand, the diffusion of carbon atoms causes the aging strengthening, and on the other hand, the breaking of the grain boundary carbide can improve the toughness of the material, so as to improve the processing performance.

[0059] Further, when the annealing temperature < 680℃, the base material of the strip steel thickness < 2.0mm cannot complete the recovery recrystallization, which will lead to the elongation of the material not to be qualified, the carbon atom migration driving force is weakened when the annealing temperature > 740℃, which will lead to the strength not to be qualified, and the annealing temperature > 740℃ will cause the increase of energy consumption, which will cause the cost to increase, so the annealing temperature of the application is controlled to be 680-740℃; secondly, when the strip steel thickness < 2.0mm, the annealing speed < 70m / min, on the one hand, the surface is easy to appear tear mark and other defects, on the other hand, the reduction of the annealing speed is easy to cause the strength not to be qualified; when the strip steel thickness ≥ 2.0mm, the annealing speed < 63m / min, on the one hand, the surface is easy to appear tear mark and other defects, on the other hand, the reduction of the annealing speed is easy to cause the C atom to gather into coarse state in the migration process, which will cause the strength not to be qualified, therefore, the annealing speed of the application is controlled to be ≥ 70m / min when the strip steel thickness < 2.0mm, and the annealing speed of the application is controlled to be ≥ 63m / min when the strip steel thickness ≥ 2.0mm. Finally, the inventor finds that when (0.106T-v) ≤ t, the elongation of the material is not qualified, the forming performance is poor, when (0.106T-v) ≥ t+6, the strength of the material is not qualified, and the surface quality is poor, therefore, the application controls t < 0.106T-v < t+6, to realize the balance of the performance and the surface.

[0060] Further, when the zinc pot temperature is too low, the flowability of the zinc liquid is poor, which is easy to appear cloud lines, tear marks and other defects, when the zinc pot temperature is too high, the zinc liquid loss is high, which will cause the cost to increase, therefore, the application controls the zinc pot temperature to be 430-460℃. In addition, when the Al, Mg content in the zinc liquid is low, the corrosion resistance is not obviously improved, when the Al, Mg content is high, it is easy to be oxidized, which will cause the surface defects, therefore, the composition of the zinc liquid is controlled to be 1%-6% Al, 1%-3% Mg and the balance of Zn.

[0061] Further, when the strip steel thickness ≥ 2.0mm, it is easy to appear the bad plate shape, the application controls the cold rolling rolling force to be 100-300t, and controls the light finishing elongation to be 0.5%-1.2%, to improve the plate shape and reduce the occurrence of the uneven passivation of the strip steel surface.

[0062] Further, one of inorganic passivation, organic passivation or inorganic-organic composite passivation is adopted, to enhance the corrosion resistance of the product.

[0063] Further, when the steel coil temperature after coiling is greater than 40℃, the water vapor is easy to form in the inside of the steel coil, which will cause the surface black spot defects. Therefore, the application controls the steel coil temperature after coiling to be ≤ 40℃.

[0064] Through the control of the above ingredients, organization and process, an economic full-spec photovoltaic steel can be obtained. The prepared photovoltaic steel comprises a hot-dip plated substrate and a plated layer, the hot-dip plated substrate has an organization of 90-96% ferrite + 1-8% carbide and the balance pearlite, and the plated layer has a composition of 1%-6% Al, 1%-3% Mg and the balance Zn.

[0065] The prepared photovoltaic steel has stable mechanical properties and surface properties, good surface quality and forming properties, and the mechanical properties meet the requirements of R eH ≥550MPa, R m ≥560MPa, A 80 ≥15%.

[0066] In summary, the present application provides a continuous hot-dip plating method for an economic full-spec photovoltaic steel by controlling the single component of the steel, the same process of hot rolling, different cold rolling organizations, stable welding quality and the stability of the annealing process. The method can obtain a photovoltaic hot-dip plated product with qualified mechanical properties, good surface quality and forming properties, and has significant economic efficiency.

[0067] 3. Beneficial effects

[0068] Compared with the prior art, the beneficial effects of the present application are:

[0069] (1) The present application realizes low-cost and high-efficiency production of steel area through chemical composition design, and realizes different organizations of hot-dip plated base materials of different specifications through hot rolling and cold rolling process control, which lays a foundation for the stability of subsequent continuous hot-dip plating process, product performance and surface quality control;

[0070] (2) The present application realizes low-cost, stable and continuous high-efficiency production of full-spec photovoltaic steel through the control of continuous hot-dip plating processes such as welding, annealing and hot-dip plating, which meets the requirements of customers for surface quality and processing performance. BRIEF DESCRIPTION OF DRAWINGS

[0071] The technical solutions of the present application will be further described in detail below in combination with the drawings and examples, but it should be understood that these drawings are designed only for illustrative purposes, and therefore do not limit the scope of the present application. In addition, unless specifically indicated, these drawings are only intended to conceptually illustrate the structural configurations described herein, and are not necessarily drawn to scale.

[0072] Figure 1 Metallographic organization of the base material of Example 1;

[0073] Figure 2 SEM organization of the base material of Example 1;

[0074] Figure 3Microstructure of substrate for Example 6;

[0075] Figure 4 SEM microstructure of substrate for Example 6;

[0076] Figure 5 Microstructure of substrate for Comparative Example 6;

[0077] Figure 6 Microstructure of substrate for Comparative Example 7;

[0078] Figure 7 Microstructure of substrate for Comparative Example 8;

[0079] Figure 8 Weld quality for Example 1;

[0080] Figure 9 Weld quality for Comparative Example 10;

[0081] Figure 10 Surface quality for Example 1;

[0082] Figure 11 Surface quality for Comparative Example 13;

[0083] Figure 12 Surface quality for Comparative Example 14. DETAILED DESCRIPTION

[0084] The following detailed description of example embodiments of the application references the drawings, which form a part thereof, in which are shown, by way of illustration, example embodiments in which the application can be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the application, and it is to be understood that other embodiments can be utilized and that various changes can be made without departing from the spirit and scope of the present application. The following detailed description of embodiments of the application is not intended to limit the scope of the application, as claimed, but is merely intended to describe exemplary embodiments of the application in sufficient detail to enable one skilled in the art to practice the application, and to present examples of the features and characteristics of the application, which, when combined with the description of the best mode to carry out the application, present the best way of carrying out the application. Therefore, the scope of the application is indicated by the appended claims rather than by the description of the embodiments.

[0085] The present application provides a continuous hot-dip plating method for full-gauge economical photovoltaic steel, which is specifically described by examples.

[0086] In the method, the hot-dip galvanizing solution comprises 1-6% Al, 1-3% Mg and the rest of Zn.

[0087] Table 1 Component control (wt%) of examples and comparative examples

[0088]

[0089]

[0090] The process control of the examples and the comparative examples is shown in Table 2 and Table 3.

[0091] Table 2 Process parameter control of steps 1-3 of the examples and the comparative examples

[0092]

[0093]

[0094] Table 3 Process parameter control of steps 4-7 of the examples and the comparative examples

[0095]

[0096]

[0097] The mechanical properties, surface quality and forming conditions of the examples and the comparative examples of the present application are shown in Table 4. The test method is as follows:

[0098] (1) The mechanical properties are detected according to the national standard;

[0099] (2) The weld quality is tested by cup convex test, and the qualified is marked as "◎", and the unqualified is marked as "×", and the unqualified weld is produced after adjusting the welding process again;

[0100] (3) The surface quality is observed by visual observation, and the FA grade represents poor surface quality and there is apparent defect, and the FB grade represents good surface quality.

[0101] (4) The forming condition is observed by multi-pass rolling, and the normal is marked as "◎", the cracking is marked as "×", and the size inconsistency is marked as "△". The rolling is not performed due to the surface quality not meeting the requirements, and is marked as " / ".

[0102] Table 4 Implementation effect of the photovoltaic steel prepared in the examples and the comparative examples

[0103]

[0104]

[0105] The metallographic structure of the substrate of Example 1 is shown in Figure 1 , the local high magnification SEM structure of the substrate of Example 1 is shown in Figure 2 , the weld quality of Example 1 is shown in Figure 8 , and the surface quality of Example 1 is shown in Figure 10 . It can be known from the figures that the proportion of deformed ferrite in the substrate structure of Example 1 is 90%, and the proportion of carbide is 5%, and the carbide is dispersedly distributed in the grain. Through the control of the whole process, the mechanical properties, surface quality and forming properties meet the requirements.

[0106] The metallographic structure of the substrate in Example 6 is as follows: Figure 3 As shown, the SEM microstructure of the substrate in Example 6 is as follows. Figure 4 As shown in the figure, the substrate microstructure of Example 6 has an isometric ferrite content of 88% and a carbide content of 7%, which are distributed along the grain boundaries. Through the control of the entire process, the mechanical properties, surface quality and forming performance meet the requirements.

[0107] The [Ti-3.4N-3S] in Comparative Example 1 is smaller, with a low content of effective Ti, resulting in limited precipitation strengthening effect, lower product strength, and incorrect dimensions after molding.

[0108] The [Ti-3.4N-3S] in Comparative Example 2 is too large, resulting in more precipitates and large performance fluctuations. The steel coils with this composition have higher strength but lower elongation, leading to forming cracks.

[0109] The lower furnace exit temperature in Comparative Example 3, the lower winding temperature in Comparative Example 4, and the higher winding temperature in Comparative Example 5 all resulted in weaker precipitation strengthening of Ti, leading to inconsistent strength and inconsistent forming dimensions.

[0110] The metallographic structure of the substrate in Comparative Example 6 is as follows: Figure 5 As shown in the figure, it can be seen from the figure that: in the matrix structure of Comparative Example 6, the proportion of deformed ferrite is 70%, the driving force for recrystallization is small, and a higher recrystallization temperature is required. The annealing temperature of 700°C is a non-complete recrystallization state, and the roll forming process causes cracking.

[0111] The metallographic structure of the substrate in Comparative Example 7 is as follows: Figure 6 As shown in the figure, the matrix structure of Comparative Example 7 has an isometric ferrite content of 70%. The hot-dip galvanizing process production line speed cannot be increased, resulting in severe tear-like defects on the surface quality. The surface quality does not meet customer requirements, and the slow speed causes carbide agglomeration and growth, resulting in low strength.

[0112] The metallographic structure of the substrate in Comparative Example 8 is as follows: Figure 7 As shown in the figure, it can be seen that the isoaxial ferrite content in the matrix structure of Comparative Example 8 is 97%, which results in low material strength and causes the dimensions after forming to not meet the requirements.

[0113] In Comparative Example 9, the welding current and welding temperature were too low, resulting in incomplete weld penetration and substandard cup protrusion quality.

[0114] The weld quality of Comparative Example 10 is as follows: Figure 9 As shown in the figure, it can be seen that the weld cup protrusion quality is unqualified due to excessive welding current and welding speed.

[0115] The welding current and welding temperature in Comparative Example 11 were too high, resulting in substandard weld cup quality.

[0116] Comparative Example 12 had a lower production line speed, severe surface clouding defects, and a long annealing time that led to grain growth and inadequate strength.

[0117] The surface quality of Comparative Examples 13 and 14 is as follows: Figures 11-12 As shown in the figure, due to the low production line speed, there are severe tear-like and cloud-like defects on the surface, which do not meet customer requirements. Moreover, the low annealing speed causes carbides to aggregate and grow during migration, resulting in low strength.

[0118] Although the speed of Comparative Example 15 met the requirements, (0.106Tv) > t+6, the annealing temperature, speed and strip thickness were not matched, the product strength was low, and the forming dimensions were not in line with the requirements.

[0119] Although the speed of Comparative Example 16 met the requirements, (0.106Tv) < t, the annealing temperature, speed and strip thickness were not matched, the product elongation was too low, resulting in forming cracks.

[0120] As can be seen from Tables 1, 2, 3, 4 and the accompanying drawings, the control effect of the present invention cannot be achieved under the same composition but different processes, or under different compositions but the same process; that is, the economical and efficient continuous hot-dip galvanizing method described in the present invention cannot be realized.

[0121] The above description is only a specific example of the present invention. It should be noted that the specific implementation of the present invention is not limited to the above-described manner. Any non-substantial improvements made using the technical concept and technical solution of the present invention, or the direct application of the technical concept and technical solution of the present invention to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A process for the production of a full-specification economic steel for photovoltaics, characterized in that, The photovoltaic steel is prepared by a continuous hot-dip plating method using a hot-dip plating base material, and the microstructure of the hot-dip plating base material is selected according to the thickness of the strip steel; when the thickness of the strip steel is less than 2.0 mm, the deformed ferrite accounts for more than 75% in the microstructure of the hot-dip plating base material, and the microstructure further contains 3%-8% carbide and the balance pearlite; when the thickness of the strip steel is greater than or equal to 2.0 mm, the equiaxed ferrite accounts for more than 80% in the microstructure of the hot-dip plating base material, and the microstructure further contains 1%-5% carbide and the balance pearlite; The continuous hot-dip plating method comprises the steps of welding, annealing, hot-dip plating, finishing, passivation and coiling: In the welding step, the welding wheel pressure is 12-20 kN, the overlapping amount is 19-29 mm, when the thickness of the mutually welded specifications is less than 2.0 mm, the welding speed is 17-21 m / min, the welding current is 26-30 kA, and the welding temperature is 950-1000℃; when the thickness of the mutually welded specifications is less than 2.0 mm and greater than or equal to 2.0 mm, the welding speed is 13-16 m / min, the welding current is 21-25 kA, and the welding temperature is 800-900℃; when the thickness of the mutually welded specifications is greater than 2.0 mm, the welding speed is 8-12 m / min, the welding current is 15-20 kA, and the welding temperature is 900-950℃; In the annealing step, the annealing temperature is 680-740℃, and when the thickness of the strip steel is less than 2.0 mm, the annealing speed is greater than or equal to 70 m / min; when the thickness of the strip steel is greater than or equal to 2.0 mm, the annealing speed is greater than or equal to 63 m / min, and the thickness of the strip steel t, the annealing temperature T and the annealing speed v satisfy the formula: t < 0.106T-v < t+6; In the hot-dip plating step, the hot-dip plating zinc liquid contains 1%-6% Al, 1%-3% Mg and the balance Zn, and the hot-dip plating temperature is 430-460℃; The hot-dip plating base material is prepared by steelmaking, hot rolling and cold rolling: The composition of the steelmaking is: C 0.02%-0.08%, Si≤0.06%, Mn 0.2%-0.8%, P≤0.025%, S≤0.012%, Als 0.02%-0.06%, Ti 0.03%-0.08%, N≤0.004%, and 0.02%≤[Ti-3.4N-3S]≤0.05%; The hot rolling process is: the discharge temperature is 1200-1250℃, the final rolling temperature is 860-900℃, and the coiling temperature is 600-640℃; The cold rolling process is: when the thickness of the strip steel is less than 2.0 mm, the cold rolling rolling force is 3000 t≤cold rolling rolling force≤5000 t; when the thickness of the strip steel is greater than or equal to 2.0 mm, the cold rolling rolling force is 100 t≤cold rolling rolling force≤300 t.

2. The manufacturing process of claim 1, wherein, The carbide is one or more of TiC, Ti(CN) and Ti4C2S2, and the size is less than or equal to 20 nm; when the thickness of the strip steel is less than 2.0 mm, the carbide is dispersedly distributed in the crystal; when the thickness of the strip steel is greater than or equal to 2.0 mm, the carbide is distributed along the grain boundary.

3. The preparation process according to claim 2, characterized in that, In the finishing step, the finishing elongation is 0.5%-1.2%; In the passivation step, the passivation is one of inorganic passivation, organic passivation and inorganic-organic composite passivation. In the coiling step, the coiled steel coil is packaged when the temperature of the coiled steel coil is equal to or less than 40 DEG C.

4. A product obtainable by the process according to any one of claims 1 to 3, characterized in that, The photovoltaic steel thus produced has a R eH ≥ 550 MPa, R m ≥ 560 MPa, A 80 ≥ 15%.

5. The product of claim 4, wherein, The steel for photovoltaic applications comprises a hot-dip plated substrate and a plated layer, the hot-dip plated substrate having a structure of 90-96% ferrite + 1-8% carbide and the balance of pearlite, and the plated layer having a composition of 1-6% Al, 1-3% Mg and the balance of Zn.

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