A method of coating and plating a hot-dipped galvanized steel sheet

Abstract

The application relates to the field of steel rolling technology, in particular to a coating and plating method of hot-based galvanized plate. The method comprises the following steps: flattening a pickling plate to make the surface microstructure of the pickling plate uniform, and obtaining a steel plate matrix; under the conditions of setting a zinc liquid temperature, setting a steel plate matrix into a zinc pot temperature and setting a gas knife parameter, plating zinc on the steel plate matrix, and then cooling under the condition of setting a cooling speed to obtain a hot-based galvanized plate. The application solves the technical problem of zinc fluctuation on the surface of the hot-based galvanized plate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of steel rolling technology, in particular to a hot-base galvanized plate coating method. BACKGROUND

[0002] The hot-base galvanized plate uses pickled plate as a substrate to directly produce galvanizing, thus omitting the cold rolling process, and has the advantages of fewer processes, lower energy consumption and lower cost.

[0003] However, there is a significant difference between the surface state of the pickled plate and the surface state of the cold-rolled strip, and the unevenness of the surface of the pickled plate can easily cause uneven plating. In addition, the hot-base galvanized plate has the characteristics of thick specifications and slow strip speed, and the air knife process parameters are significantly different from those of the traditional cold-base galvanizing production line. In addition, the hot-base galvanized plate has thick specifications, and the core heat inside the strip is large, which can easily cause the zinc liquid to flow, resulting in zinc undulation on the surface of the hot-base galvanized plate. SUMMARY

[0004] The present application provides a hot-base galvanized plate coating method to solve the technical problem of zinc undulation on the surface of the hot-base galvanized plate.

[0005] In a first aspect, the present application provides a hot-base galvanized plate coating method, which comprises:

[0006] The pickled plate is leveled to make the surface microstructure of the pickled plate uniform, and a steel plate substrate is obtained.

[0007] The steel plate substrate is galvanized under the condition of setting the zinc liquid temperature, setting the steel plate substrate temperature entering the zinc pot and setting the air knife parameters, and then cooled under the condition of setting the cooling speed to obtain a hot-base galvanized plate.

[0008] Optionally, the leveling of the pickled plate to make the surface microstructure of the pickled plate uniform to obtain a steel plate substrate comprises:

[0009] The pickled plate is leveled under the condition of setting the parameters of the leveler to make the surface microstructure of the pickled plate uniform, and a steel plate substrate is obtained.

[0010] The setting of the parameters of the leveler comprises: the surface roughness of the roller is 2.5-3.5 μm; and the leveling unit rolling force is ≥1500 kN / m.

[0011] Optionally, the setting of the zinc liquid temperature and the setting of the steel plate substrate temperature entering the zinc pot satisfy the following relationship:

[0012] M-N = 2-8

[0013] In the formula, M represents the set zinc liquid temperature; and N represents the set steel plate substrate temperature entering the zinc pot.

[0014] Optionally, the zinc liquid temperature is set to 410-450 DEG C.

[0015] Optionally, the gas knife parameter setting includes: gas knife lip opening, gas knife and steel plate base spacing, and gas knife edge baffle and steel plate base spacing.

[0016] Optionally, the gas knife lip opening is 1.1-1.4 mm.

[0017] Optionally, the gas knife and steel plate base spacing satisfies the relationship: Z < 7*d, wherein Z represents the gas knife and steel plate base spacing, and d represents the gas knife lip opening.

[0018] Optionally, the gas knife edge baffle and steel plate base spacing and the gas knife and steel plate base spacing satisfy the relationship: Y < 0.3*Z, wherein Z represents the gas knife and steel plate base spacing, and Y represents the gas knife edge baffle and steel plate base spacing.

[0019] Optionally, the cooling speed is set to 5-12 DEG C / s.

[0020] Optionally, the hot-dip galvanized steel plate has a thickness of greater than or equal to 3.0 mm.

[0021] The above technical solution provided by the embodiments of the present application has the following advantages compared with the prior art:

[0022] The method provided by the embodiments of the present application further improves the unevenness of the coating caused by poor substrate surface uniformity by leveling the pickled plate surface; the gas knife flow stability is effectively improved, and the strip steel coating uniformity is improved by controlling the gas knife opening and correspondingly setting the gas knife and steel plate base spacing and the gas knife edge baffle and steel plate base spacing; the unevenness of the coating caused by the zinc liquid flow behind the gas knife due to the internal heat of the strip steel is effectively improved by controlling the strip steel entry temperature and the cooling speed. In summary, the present application solves the technical problem of solving the zinc fluctuation on the surface of the hot-dip galvanized steel plate. BRIEF DESCRIPTION OF DRAWINGS

[0023] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the specification, serve to explain the principles of the present application.

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0025] Figure 1A flowchart of a coating and plating method of a hot-dip galvanized sheet provided by an embodiment of the present application;

[0026] Figure 2 A white light interferometer test chart of a pickled sheet without leveling treatment provided by an embodiment of the present application;

[0027] Figure 3 A white light interferometer test chart of a pickled sheet after leveling treatment provided by an embodiment of the present application;

[0028] Figure 4 A coating surface morphology of a hot-dip galvanized sheet provided by Comparative Example 1 of the present application;

[0029] Figure 5 A coating surface morphology of a hot-dip galvanized sheet provided by Example 1 of the present application. DETAILED DESCRIPTION

[0030] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below in connection with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0031] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limitation on the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the described range, such as 1, 2, 3, 4, 5 and 6, which applies to any range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0032] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" or "at least one of a, b, and c" can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be a single or multiple.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Firstly, this application provides a coating method for hot-dip galvanized steel sheets; please refer to [link to relevant documentation]. Figure 1 The method includes:

[0035] S1. Flatten the pickled plate to make the surface microstructure of the pickled plate uniform, and obtain the steel plate substrate;

[0036] S2. Under the conditions of setting the zinc bath temperature, setting the temperature of the steel plate substrate entering the zinc pot, and setting the air knife parameters, the steel plate substrate is galvanized, and then cooled under the condition of setting the cooling rate to obtain a hot-dip galvanized sheet.

[0037] In the embodiments of this application, "coating" means using a chemical method to uniformly adhere metallic zinc to the surface of a steel plate substrate to form a thin zinc layer. Figure 2 , Figure 3 The uniformity of the pickled plate before and after flattening is characterized using a white light interferometer. It can be seen that the surface of the pickled plate is more uniform after flattening. Figure 4 and Figure 5 Microscopic morphology images of hot-dip galvanized sheets prepared by different processes are shown. It can be seen that the above-mentioned coating methods for hot-dip galvanized sheets solve the problem of zinc fluctuations during the galvanizing process. Figure 5(Example 1) The surface of the hot-based galvanized sheet is more smooth and uniform. The method can also be used for the production of hot-based pure zinc plated products and hot-based zinc-aluminum-magnesium plated products.

[0038] Hot-based galvanized sheet uses pickled sheet as substrate to directly produce galvanized sheet, omitting the cold rolling process, thus having the advantages of fewer processes, lower energy consumption, and lower cost. However, due to the significant difference between the surface state of the pickled sheet and the surface state of the cold-rolled strip, the unevenness of the pickled sheet surface can easily cause uneven plating. In addition, hot-based galvanized sheet has the characteristics of thick gauge and slow strip speed, and the air knife process parameters are significantly different from the traditional cold-based galvanized production line. In addition, the hot-based galvanized sheet has a thick gauge, and the core heat inside the strip is large, which can easily cause the zinc liquid to flow, resulting in zinc undulation on the surface of the hot-based galvanized sheet.

[0039] In the present application, the pickled sheet is smoothed by using a roughening roller to improve the uniformity of the microstructure of the pickled sheet surface, thereby further improving the uneven plating phenomenon caused by the poor uniformity of the substrate surface. By controlling the opening degree of the air knife and correspondingly setting the distance between the air knife and the steel plate substrate and the distance between the air knife edge baffle and the steel plate substrate, the stability of the air knife airflow can be effectively improved, and the uniformity of the strip plating can be improved. By controlling the strip entry temperature and the cooling speed after galvanizing to force cooling, the uneven plating caused by the flow of zinc liquid due to the heat inside the strip can be effectively improved.

[0040] In the embodiments of the present application, the final hot-based galvanized sheet is prepared by the steps of pickling-smoothing-coiling-uncoiling-welding-cleaning-annealing-galvanizing-finishing-coiling. In the annealing stage of the heating furnace, the annealing temperature of the high-strength steel is appropriately increased, and the tension in the soaking section (the unit tension of the strip is increased by 10%-15% on the basis of the basic tension) is increased to release the internal residual stress of the high-strength steel and increase the plastic deformation in the high-temperature section, thereby improving the strip entry shape.

[0041] In some embodiments, the pickled sheet is smoothed to make the microstructure of the surface of the pickled sheet uniform, to obtain a steel plate substrate, comprising:

[0042] The pickled sheet is smoothed under the condition of setting the parameters of the smoothing machine to make the microstructure of the surface of the pickled sheet uniform, to obtain a steel plate substrate.

[0043] The setting of the parameters of the smoothing machine includes: the surface roughness of the roller is 2.5 μm-3.5 μm; the smoothing unit rolling force is ≥1500 kN / m.

[0044] In the embodiments of the present application, the rolling mill roll is electric spark roughened to increase the roughness of the roll surface, and the roughness of the roughened roll surface is controlled at 2.5-3.5 μm. The positive effect is that the large roughness can cover the unevenness of the surface structure of the pickled plate. If the roughness of the roll surface is too large, the roughness will decay too fast to some extent, and the surface uniformity of the steel substrate will be poor; if the roughness of the roll is too small, the surface cannot be effectively covered to some extent, and the surface structure of the steel substrate will be uneven. Specifically, the roughness of the roll surface can be 2.5 μm, 2.7 μm, 2.9 μm, 3.1 μm, 3.3 μm, 3.5 μm, etc.

[0045] The positive effect of controlling the unit rolling force of the skin pass mill to be greater than or equal to 1500 kN / m is that the surface roughness transfer rate is improved. If the unit rolling force of the skin pass mill is too low, the roughness transfer rate will be insufficient to some extent. Specifically, the unit rolling force of the skin pass mill can be 1500 kN / m, 1600 kN / m, 1700 kN / m, 1800 kN / m, 1900 kN / m, 2000 kN / m, etc.

[0046] In some embodiments, the set zinc liquid temperature and the set steel plate substrate temperature into the zinc pot satisfy the following relationship:

[0047] M-N = 2-8

[0048] In the formula, M represents the set zinc liquid temperature; and N represents the set steel plate substrate temperature into the zinc pot.

[0049] The positive effect of controlling the set zinc liquid temperature to be 2-8 °C higher than the set steel plate substrate temperature into the zinc pot is that the strip steel core heat is reduced. If the value of M-N is too high, the flow trend of the zinc layer after passing the air knife will be increased to some extent; and if the value of M-N is too low, the difficulty of scraping the zinc by the air knife will be increased to some extent. Specifically, the value of M-N can be 2, 4, 6, 8, etc.

[0050] In some embodiments, the set zinc liquid temperature is 410-450 °C.

[0051] The positive effect of controlling the set zinc liquid temperature to be 410-450 °C is that the flowability of the zinc liquid can be ensured, and the strip steel surface zinc liquid flow caused by too high zinc liquid temperature can be avoided. If the set zinc liquid temperature is too high, the flow trend of the zinc layer after passing the air knife will be increased to some extent; and if the set zinc liquid temperature is too low, the difficulty of scraping the zinc by the air knife will be increased to some extent. Specifically, the set zinc liquid temperature can be 410 °C, 420 °C, 430 °C, 440 °C, 450 °C, etc. Specifically, the chemical composition of the zinc liquid is Al: 6 wt%, Mg: 2.5 wt%, and the rest is Zn.

[0052] In some embodiments, the setting the gas knife parameters comprises: a gas knife lip opening, a distance between the gas knife and the steel plate base, and a distance between the gas knife edge baffle and the steel plate base.

[0053] The function of the gas knife: it can wipe off the zinc on the outlet steel strip of the zinc pot to achieve the function of controlling the thickness of the zinc layer. The positive effects of controlling the gas knife opening and setting the distance between the gas knife and the steel plate base and the distance between the gas knife edge baffle and the steel plate base: it can effectively improve the stability of the gas flow and improve the uniformity of the strip steel coating.

[0054] In some embodiments, the gas knife lip opening is 1.1mm-1.4mm.

[0055] The positive effect of controlling the gas knife lip opening to be 1.1mm-1.4mm: it can ensure the zinc wiping ability while improving the stability of the gas flow. If the gas knife lip opening is set too high, it will increase the turbulence of the gas flow to a certain extent; if the gas knife lip opening is set too low, it will lead to insufficient zinc wiping ability to a certain extent. Specifically, the gas knife lip opening can be 1.1mm, 1.2mm, 1.3mm, 1.4mm, etc.

[0056] In some embodiments, the distance between the gas knife and the zinc liquid satisfies the relationship: Z<7*d, wherein Z represents the distance between the gas knife and the steel plate base, and d represents the gas knife lip opening.

[0057] The positive effect of controlling the distance between the gas knife and the steel plate base to satisfy the relationship: Z<7*d: it can ensure that the gas flow is in a laminar flow state and reduce the influence of vortex. If the distance between the gas knife and the steel plate base is too high, it will increase the turbulence to a certain extent, making the gas flow unstable; if the distance between the gas knife and the steel plate base is too low, it will touch the strip steel to a certain extent, causing zinc sticking. Specifically, the distance between the gas knife and the steel plate base can be 7mm, 8mm, 9mm, etc.

[0058] In some embodiments, the distance between the gas knife edge baffle and the steel plate base and the distance between the gas knife and the zinc liquid satisfy the relationship: Y<0.3*Z, wherein Z represents the distance between the gas knife and the steel plate base, and Y represents the distance between the gas knife edge baffle and the steel plate base.

[0059] The positive effect of controlling the distance between the gas knife edge baffle and the steel plate base and the distance between the gas knife and the steel plate base to satisfy the relationship: Y<0.3*Z: it can reduce the thickening of the edge zinc layer. If the distance between the gas knife edge baffle and the steel plate base is too high, it will lead to obvious thickening of the coating edge to a certain extent; if the distance between the gas knife edge baffle and the steel plate base is too low, it will affect the gas baffle slag sticking to a certain extent. Specifically, the distance between the gas knife edge baffle and the steel plate base can be 2mm, 2.2mm, 2.5mm, etc.

[0060] In some embodiments, the set cooling speed is 5-12 ℃ / s.

[0061] The positive effect of controlling the set cooling speed to be 5-12 ℃ / s is to make the zinc liquid solidify as soon as possible and avoid the uneven zinc coating caused by the flow of the zinc liquid. In the cooling process, since the thickness of the hot-dip galvanized sheet is relatively large, the moving cooling fan is used 2-3 m above the air knife to improve the cooling speed for forced cooling, which can effectively improve the uneven coating formed by the flow of the zinc liquid behind the air knife due to the internal heat of the strip steel. If the set cooling speed is too low, the flowability of the coating behind the air knife will be increased to some extent. Specifically, the set cooling speed can be 5 ℃ / s, 6 ℃ / s, 7 ℃ / s, 8 ℃ / s, 9 ℃ / s, 10 ℃ / s, 11 ℃ / s, 12 ℃ / s, etc.

[0062] In some embodiments, the thickness of the hot-dip galvanized sheet is ≥3.0 mm.

[0063] In the embodiments of the present application, the thickness of the hot-dip galvanized sheet obtained by the above-mentioned hot-dip galvanizing method can be 3.0 mm, 3.5 mm, 4.0 mm, etc.

[0064] The present application will be further described in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. The experimental methods not specified in the following examples are generally determined according to the national standards. If there is no corresponding national standard, the international standard, the conventional condition, or the condition suggested by the manufacturer is used.

[0065] Example 1

[0066] The pickling plate is subjected to a skin pass treatment by using a skin pass mill, and the roll is roughened by EDT, and the roughness of the roll surface after roughening is 2.5 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the air knife lip opening degree is 1.1 mm, the distance between the air knife and the steel plate base body is 7 mm, and the distance between the air knife edge baffle and the steel plate base body is 2 mm. The zinc liquid temperature is controlled to be 450 ℃, and the strip steel temperature entering the zinc pot is 445 ℃. After galvanizing, the moving cooling fan is used 2.5 m above the air knife for forced cooling, and the cooling speed is 10 ℃ / s, and the hot-dip galvanized sheet with a thickness specification of 3.0 mm, a width specification of 1100 mm, and a coating thickness of Z140 is obtained.

[0067] Example 2

[0068] The pickling plate is subjected to the skin pass treatment by a skin pass mill, the roll is subjected to the EDT roughening, and the roughened roll surface roughness is 2.5 μm. The skin pass unit rolling force is 1500 KN. In the galvanizing production process, the gas knife lip opening degree is 1.1 mm, the gas knife and the steel plate base spacing is 7 mm, the gas knife edge baffle and the steel plate base spacing is 2 mm. And the zinc liquid temperature is controlled to be 410 ℃, the strip steel into the zinc pot temperature is 408 ℃. After the galvanizing, the 2 m above the gas knife is subjected to the moving cooling fan, the forced cooling is adopted, the cooling speed is 8 ℃ / s, the hot base galvanizing plate with the thickness specification of 3.0 mm, the width specification of 1100 mm and the plated layer thickness of Z140 is obtained.

[0069] Example 3

[0070] The pickling plate is subjected to the skin pass treatment by a skin pass mill, the roll is subjected to the EDT roughening, and the roughened roll surface roughness is 3.5 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the gas knife lip opening degree is 1.1 mm, the gas knife and the steel plate base spacing is 7 mm, the gas knife edge baffle and the steel plate base spacing is 2 mm. And the zinc liquid temperature is controlled to be 450 ℃, the strip steel into the zinc pot temperature is 442 ℃. After the galvanizing, the 3 m above the gas knife is subjected to the moving cooling fan, the forced cooling is adopted, the cooling speed is 12 ℃ / s, the hot base galvanizing plate with the thickness specification of 3.5 mm, the width specification of 1100 mm and the plated layer thickness of Z140 is obtained.

[0071] Example 4

[0072] The pickling plate is subjected to the skin pass treatment by a skin pass mill, the roll is subjected to the EDT roughening, and the roughened roll surface roughness is 3.5 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the gas knife lip opening degree is 1.4 mm, the gas knife and the steel plate base spacing is 9 mm, the gas knife edge baffle and the steel plate base spacing is 2.5 mm. And the zinc liquid temperature is controlled to be 450 ℃, the strip steel into the zinc pot temperature is 442 ℃. After the galvanizing, the 3 m above the gas knife is subjected to the moving cooling fan, the forced cooling is adopted, the cooling speed is 5 ℃ / s, the hot base galvanizing plate with the thickness specification of 3.0 mm, the width specification of 1100 mm and the plated layer thickness of Z140 is obtained.

[0073] Example 5

[0074] The pickling plate is treated by using a skin pass mill, and the roughness of the roll surface is 3.0 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the gas knife lip opening is 1.25 mm, the distance between the gas knife and the steel plate base is 8 mm, the distance between the gas knife edge baffle and the steel plate base is 2.2 mm; and the zinc liquid temperature is controlled to be 430 ℃, and the strip steel temperature entering the zinc pot is 426 ℃. After galvanizing, the 2.5 m above the gas knife is cooled by using a moving cooling fan, and forced cooling is adopted, and the cooling speed is 10 ℃ / s, so that the hot-dip galvanized sheet with the thickness specification of 3.0 mm, the width specification of 1100 mm and the coating thickness of Z140 is obtained.

[0075] Comparative Example 1

[0076] The pickling plate is treated by using a skin pass mill, and the roughness of the roll surface is 3.0 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the gas knife lip opening is 1.25 mm, the distance between the gas knife and the steel plate base is 8 mm, the distance between the gas knife edge baffle and the steel plate base is 2.2 mm; and the zinc liquid temperature is controlled to be 430 ℃, and the strip steel temperature entering the zinc pot is 426 ℃. After galvanizing, the 2.5 m above the gas knife is cooled by using a moving cooling fan, and forced cooling is adopted, and the cooling speed is 10 ℃ / s, so that the hot-dip galvanized sheet with the thickness specification of 3.0 mm, the width specification of 1100 mm and the coating thickness of Z140 is obtained.

[0077] Comparative Example 2

[0078] The pickling plate is treated by using a skin pass mill, and the roughness of the roll surface is 3.0 μm. The skin pass unit rolling force is 2000 KN. In the galvanizing production process, the gas knife lip opening is 1.25 mm, the distance between the gas knife and the steel plate base is 8 mm, the distance between the gas knife edge baffle and the steel plate base is 2.2 mm; and the zinc liquid temperature is controlled to be 430 ℃, and the strip steel temperature entering the zinc pot is 426 ℃. After galvanizing, the 2.5 m above the gas knife is cooled by using a moving cooling fan, and forced cooling is adopted, and the cooling speed is 10 ℃ / s, so that the hot-dip galvanized sheet with the thickness specification of 3.0 mm, the width specification of 1100 mm and the coating thickness of Z140 is obtained.

[0079] Table 1 shows the results of the zinc undulation phenomenon on the surface of the hot-dip galvanized sheet of Examples 1-5 and Comparative Examples 1-2.

[0080] Serial number Presence or absence of zinc undulation phenomenon on the surface of hot-dip galvanized steel sheet Example 1 Absence of zinc undulation phenomenon Example 2 Absence of zinc undulation phenomenon Example 3 Absence of zinc undulation phenomenon Example 4 Absence of zinc undulation phenomenon Example 5 Absence of zinc undulation phenomenon Comparative Example 1 Presence of zinc undulation phenomenon Comparative Example 2 Presence of zinc undulation phenomenon

[0081] As shown in Table 1, the coating method of the hot-dip galvanized sheet of the present application can solve the zinc undulation phenomenon on the surface of the hot-dip galvanized sheet, and the hot-dip galvanized sheet of Examples 1-5 has no zinc undulation phenomenon.

[0082] The foregoing detailed description of the application has been presented for purposes of illustration and description. Various modifications and changes can be made to these embodiments without departing from the spirit and scope of the application. It is intended that the scope of the application should not be limited by the particular representative embodiments described above.

Claims

1. A coating and plating method for hot-dip galvanized steel sheet, characterized by, The method comprises: flatting the pickling plate to make the surface microstructure of the pickling plate uniform, to obtain a steel plate base; galvanizing the steel plate base under the condition that the zinc liquid temperature, the steel plate base temperature entering the zinc pot and the air knife parameters are set, and then cooling under the condition that the cooling speed is set, to obtain a hot base galvanized plate; the flatting parameters comprise: the roughness of the roll surface is 2.5-3.5 μm; the flatting unit rolling force is ≥1500 kN / m; the set zinc liquid temperature M and the set steel plate base temperature entering the zinc pot N satisfy the following relation: M-N=2-8; the set zinc liquid temperature is 410-450 ℃; the distance between the air knife and the steel plate base satisfies the relation: Z<7*d, the distance between the air knife edge baffle and the steel plate base and the distance between the air knife and the steel plate base satisfy the relation: Y<0.3*Z; in the formula, Z represents the distance between the air knife and the steel plate base; d represents the air knife lip opening degree, and Y represents the distance between the air knife edge baffle and the steel plate base; the air knife lip opening degree is 1.1-1.4 mm; the set cooling speed is 5-12 ℃ / s; the thickness of the hot base galvanized plate is ≥3.0 mm.

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