Production method for eliminating tooth mark defects on surface of zinc-aluminum-magnesium coated steel plate and zinc-aluminum-magnesium coated steel plate

Abstract

The invention relates to the field of metal materials, and discloses a production method for eliminating tooth mark defects on the surface of a zinc-aluminum-magnesium coated steel plate and the zinc-aluminum-magnesium coated steel plate. The production method comprises the following steps: S1, controlling the temperature of strip steel entering a zinc pot; s2, the distance between the dam top of a flow guide dam in the furnace nose and the liquid level of the plating solution is controlled to be 2-5 mm, and the rotating speed of a zinc slag pump is controlled to be 80-120 r / min; and S3, the ingot adding speed of the zinc-aluminum-magnesium ingot is controlled. By means of controlling the temperature of the zinc pot, the ingot adding speed, the distance between the top of the flow guide dam and the liquid level of the plating solution, the rotating speed of the zinc slag pump and the like, generation and flowing of the zinc slag are reduced, and the tooth mark defect on the surface of the thick-specification thick-plating zinc-aluminum-magnesium-plating steel plate is eliminated.

Description

Technical Field

[0001] The invention relates to the field of metal materials, and in particular to a production method for eliminating tooth mark defects on the surface of a zinc-aluminum-magnesium coated steel plate and a zinc-aluminum-magnesium coated steel plate. Background Art

[0002] With the increasing requirements for energy saving, environmental protection and safety of key parts such as automobiles, home appliances and structural parts, it is necessary to ensure that steel materials are not seriously corroded during their service life. Adding appropriate amounts of metal magnesium and aluminum to pure zinc can improve the corrosion resistance of the coating, greatly extend the service life of the coated steel plate, and reduce the consumption of zinc by reducing the weight of the coating, which has high social benefits and promotion and application value.

[0003] In the field of photovoltaic brackets, double-sided 275g / m 2 Zinc-aluminum-magnesium coating products, replacing the traditional double-sided 600g / m 2 The above batch galvanized products have the same service life as the coating, meeting the 25-year service life requirement in the photovoltaic field. At the same time, the zinc-aluminum-magnesium plate can be directly processed into photovoltaic brackets at the user end, reducing the pickling, galvanizing, passivation and other processes at the user end of the batch galvanizing process of hot-rolled products, thus helping the green development of the client end.

[0004] Due to the addition of easily oxidized elements such as Al and Mg, zinc-aluminum-magnesium coated products produce more zinc slag during the production process, making surface quality control more difficult. When the thickness of the zinc-aluminum-magnesium coated steel plate is ≥1.5mm and the double-sided coating weight is ≥275g / m 2 When the steel plate is coated with zinc, aluminum and magnesium, a large number of tooth mark defects are easily generated on the surface of the steel plate. Therefore, a method for improving the surface quality of thick-coated zinc-aluminum-magnesium coated steel plates is urgently needed.

[0005] CN 110438427 A "A method for eliminating surface defects of thick zinc-aluminum-magnesium coated steel" discloses a method for eliminating circular black spot defects on the surface of thick zinc-aluminum-magnesium coated steel. The method mainly achieves the elimination of surface black spot defects by controlling the zinc pot temperature to 445-455°C and controlling the cooling tower fan power during post-plating cooling. The scheme is aimed at black spot defects, and does not specify the zinc pot immersion plating process, air knife parameter control, post-plating cooling temperature and finishing process.

[0006] CN 108018514A "A method for controlling surface defects of Zn-Al-Mg alloy plate and Zn-Al-Mg alloy plate" discloses a method for controlling surface defects of Zn-Al-Mg alloy plate. The mass percentage of the components of the plating bath is: Al 0.15%-6.5%, Mg 0.2%-7%, RE≤0.2%, Sr 0.002%-0.2%, the remainder is Zn and other inevitable impurities, and Mg / Al is greater than 1.0; the temperature of the plating bath is 360-480℃; the air knife scraping medium used is limited to a gas with an oxygen content of less than 5% by volume. The scheme mainly completes the production of high surface quality zinc-aluminum-magnesium plating products by limiting the oxygen content of the air knife medium and the Mg / Al ratio to be greater than 1.

[0007] CN 113584346A "An excellent corrosion-resistant zinc alloy coating" discloses an excellent corrosion-resistant zinc alloy coating. It includes a substrate and a coating coated on the surface of the substrate, and the coating contains the following chemical components in weight percentage: Al 0.5% to 6%; Mg 0.1% to 3%; Si 0.05% to 0.1%; Re 0.05% to 0.1%; total impurities less than 0.01%; the balance is Zn. This solution can significantly reduce the coating thickness by controlling the coating elements and element content, and at the same time can slow down the oxidation of the plating solution surface, reduce the surface defects of the coating, and improve the corrosion resistance of the hot-dip galvanized aluminum-magnesium alloy steel plate; thereby ensuring the surface quality of the steel plate.

[0008] CN 110760774 A "Zinc-aluminum-magnesium steel plate and preparation method for effectively controlling black spots on the surface of hot-dip galvanized aluminum-magnesium steel plate by CSP process" discloses a zinc-aluminum-magnesium steel plate and a preparation method for effectively controlling black spots on the surface of hot-dip galvanized aluminum-magnesium steel plate by CSP process. The scheme ensures that the surface quality of the formed zinc-aluminum-magnesium steel plate is good and there is no black spot defect on the surface by controlling the chemical composition of the coating and the substrate and the amount of each chemical component, so that the zinc-aluminum-magnesium steel plate has good corrosion resistance and bonding strength. At the same time, by combining the CSP process and the continuous hot-dip process, the surface quality of the prepared zinc-aluminum-magnesium steel plate is good and there is no black spot defect on the surface, thereby ensuring the corrosion resistance, strength and oxidation resistance of the zinc-aluminum-magnesium steel plate.

[0009] CN 108642493 A "A method for improving the color difference defect on the surface of zinc-aluminum-magnesium alloy coating" discloses a method for improving the color difference defect on the surface of zinc-aluminum-magnesium alloy coating. By adding other alloy elements (any one or more of the following alloy elements: boron, silicon, copper, nickel, manganese) to the zinc-aluminum-magnesium alloy coating, the stability of the coating in the atmospheric environment is improved, the defect of color difference on the surface of the coating is overcome, and the effect of improving the appearance quality of the zinc-aluminum-magnesium coating is achieved.

[0010] CN104060209A "A hot-dip galvanized aluminum-magnesium steel sheet and manufacturing method" discloses a production method of zinc-aluminum-magnesium components. The composition of the plating solution is Al: 1.9%-3.9%, Mg: 1.9%-3.9%, and the balance is Zn and unavoidable impurities. This solution has a high Mg content, a lot of scum, and a surface quality deviation. It is mainly to improve the corrosion resistance of the product, the immersion plating time is long, and the product's blackening resistance performance is biased.

[0011] CN 103966537 A "A method for controlling zinc flow lines of thick material and thick coating hot-dip galvanized products" discloses a method for controlling zinc flow lines of thick material and thick coating hot-dip galvanized products. The temperature of the spraying medium is adjusted to improve the cooling capacity of the spraying medium on the strip steel, and the process parameters of the air knife are optimized at the same time. The specific parameters are selected as follows: 1) before production, the temperature in the fan room is controlled within the range of 0 to 10°C; 2) the air knife parameters are optimized: the distance between the knife lip and the liquid surface is 600 to 1000 / mm; the distance between the knife lip and the strip steel is 15 to 30mm; according to the unit speed and the coating thickness, the air knife pressure is 100 to 300mbar.

[0012] CN 110684929 A "An ultra-thick coated hot-dip galvanized steel strip for underground corridor corrugated pipe and its production method" discloses an ultra-thick coated hot-dip galvanized steel strip for underground corridor corrugated pipe and its production method. By reducing the air knife height, increasing the distance between the knife lip and the strip steel, and controlling the knife lip opening in sections, the generation of zinc flow lines and edge thickness defects is suppressed. The thickness is 1.3-2.0 mm, the width is 1000-1480 mm, the process speed is 90-130 m / min, the annealing temperature is 690-710 ° C, the insulation time is 2-4 min, the zinc liquid temperature is 457-463 ° C, the pot temperature is 420-450 ° C, the air knife height is 150-180 mm, the distance between the knife lip and the strip steel is 50-56 mm, and the air knife pressure is 100-120 mbar. In this scheme, there is a large difference between the temperature entering the pot and the zinc liquid, which can easily cause large fluctuations in the plating solution temperature. The induction heater works at high power, and the plating solution stirs a lot of zinc slag. The distance between the knife lip and the strip is large, and the uniformity of the coating blown by the air knife is poor, which can easily cause the defect of too thick coating on the edge of the strip.

[0013] At present, there are many technical solutions for zinc-aluminum-magnesium alloy coating. The existing solutions mainly focus on the composition and surface treatment of zinc-aluminum-magnesium alloy coating. The control of tooth mark defects on the surface of thick-specification and thick-coated zinc-aluminum-magnesium products is not involved. Summary of the invention

[0014] The purpose of the present invention is to overcome the problem of difficulty in controlling the surface quality of thick-specification and thick-coated zinc-aluminum-magnesium products in the prior art, and to provide a production method and a zinc-aluminum-magnesium coated steel plate for eliminating tooth mark defects on the surface of zinc-aluminum-magnesium coated steel plates. The scheme adopts means such as controlling the zinc inlet pot temperature, ingot adding speed, the distance between the top of the diversion dam and the plating solution surface, and the speed of the zinc slag pump to reduce the generation and flow of zinc slag and eliminate the tooth mark defects on the surface of thick-specification and thick-coated zinc-aluminum-magnesium coated steel plates.

[0015] In order to achieve the above object, the present invention provides a production method for eliminating tooth mark defects on the surface of zinc-aluminum-magnesium coated steel plates, the production method comprising:

[0016] S1. Control the temperature of the strip entering the zinc pot according to formula (1):

[0017] T2=T1-0.01v-0.005s (1)

[0018] In formula (1), T2 represents the temperature of the strip entering the zinc pot, in °C; T1 represents the temperature of the zinc pot, in °C; v represents the speed of the steel plate in the zinc pot, in m / min; s represents the cross-sectional area of ​​the strip, in mm 2 The present invention controls the temperature T2 of the steel strip entering the zinc pot, relies on the heat of the steel strip to ensure the temperature of the zinc pot is stable, and further maintains the operating power of the zinc pot induction heater to be stable, preventing high-power operation from causing zinc slag to be stirred and affecting the surface quality of the steel strip.

[0019] S2, control the distance between the top of the diversion dam in the furnace nose and the surface of the plating solution to be 2-5mm, and the speed of the zinc slag pump to be 80-120 rpm;

[0020] S3. Control the feeding speed of zinc, aluminum and magnesium ingots according to formula (2):

[0021] v1=100×(2×c 2 ×t 2 ×w) / (v×8.47×10 8 ) (2)

[0022] In formula (2), v1 represents the speed of adding zinc-aluminum-magnesium ingots, in cm / min, that is, in the present invention, the speed of adding zinc-aluminum-magnesium ingots refers to the speed at which the zinc-aluminum-magnesium ingots descend relative to the surface of the plating solution; t represents the thickness of the finished zinc-aluminum-magnesium coated steel sheet, in mm; c represents the width of the finished zinc-aluminum-magnesium coated steel sheet, in mm; w represents the double-sided coating weight of the finished zinc-aluminum-magnesium coated steel sheet, in g / m 2 .

[0023] The main process flow of preparing zinc-aluminum-magnesium coated steel plates of the present invention includes: annealing the steel strip in an annealing furnace, cooling it to the zinc pot entry temperature, sending it into the zinc pot for hot dip plating (the plating solution will be consumed during the hot dip plating process, and zinc-aluminum-magnesium ingots need to be added for replenishment. During the melting of the zinc-aluminum-magnesium ingots, the zinc pot induction heater provides the temperature), and then adjusting the air knife parameters to control the double-sided coating weight.

[0024] In the present invention, when the steel strip is annealed, the annealing temperature of the steel strip is controlled to be 550-700°C. By controlling the annealing temperature within this range, the core heat carried inside the steel plate can be reduced, and a high temperature when the steel strip enters the zinc pot can be prevented, resulting in a large amount of zinc slag. Because when there is a large amount of zinc slag, part of the zinc slag will follow the plating solution and adhere to the surface of the steel strip during the immersion plating process, and then when the air knife is used to blow and wipe to control the weight of the coating, part of the zinc slag will fall off under the action of airflow and gravity, and the position where it falls off will form a tooth mark defect, so it is necessary to prevent the occurrence of a large amount of zinc slag.

[0025] In step S1 of the present invention, the zinc pot contains the following components in weight percentage: Al content is 1-13wt%, Mg content is 1-6wt%, and the rest is Zn and inevitable impurities such as Fe.

[0026] Further, in a preferred case, in step S1, 420°C ≤ T1 ≤ 460°C is controlled. Controlling the zinc pot temperature T1 within this range can effectively reduce the core heat carried inside the steel plate. When T1 is higher, more zinc slag is produced. When T1 is lower, the fluidity of the plating solution will deteriorate. Therefore, it is more appropriate to control T1 within the above range.

[0027] In step S1 of the present invention, 65m / min≤v≤75m / min is controlled, and the running speed v of the steel plate in the zinc pot is increased to within this range. The greater the linear speed, the faster the flow of the plating solution, the faster the speed at which the zinc slag floats driven by the plating solution, and the smaller the possibility that the zinc slag adheres to the surface of the steel strip.

[0028] In the present invention, the induction heater of the zinc pot needs to be kept in a low-power operating state during production, with an operating power of 10-30KW, to prevent the plating solution flow field from being disturbed when the induction heater works at high power, thereby stirring up the zinc slag.

[0029] In the present invention, the cross-sectional area s of the steel strip is equal to the product of the steel strip width and the steel strip thickness.

[0030] Since the coating will not change the width of the finished zinc-aluminum-magnesium coated steel plate, it will affect the thickness of the finished zinc-aluminum-magnesium coated steel plate, but the change in thickness is at the micron level and can be ignored. Therefore, in the present invention, the width of the finished zinc-aluminum-magnesium coated steel plate is equal to the width of the strip steel, and the thickness of the finished zinc-aluminum-magnesium coated steel plate is equal to the thickness of the strip steel.

[0031] In the production method described in the present invention, the position of the guide dam in the zinc boiler nose and the speed of the zinc slag pump are controlled to keep the plating solution overflowing in the guide dam. In this way, the zinc slag in the furnace nose can be discharged to the outside of the furnace nose, which can reduce the contact with the strip steel. Therefore, it is more appropriate to control the distance between the top of the guide dam and the plating solution surface and the speed of the zinc slag pump within the range described in step S2.

[0032] Since the plating solution in the zinc pot will gradually be consumed during the hot-dip plating process, zinc-aluminum-magnesium ingots need to be added to replenish the plating solution. The composition of the zinc-aluminum-magnesium ingots used is basically consistent with the composition of the zinc pot, that is, the added zinc-aluminum-magnesium ingots contain the following weight percentage components: Al content is 1-13wt%, Mg content is 1-6wt%, and the rest is Zn and unavoidable impurities such as Fe.

[0033] Furthermore, the added zinc-aluminum-magnesium ingot is in the shape of a rectangular parallelepiped. When adding the zinc-aluminum-magnesium ingot to the zinc pot, it is preferably added to the plating solution along the length direction of the zinc-aluminum-magnesium ingot. In this way, the cross-sectional area of ​​the zinc-magnesium-aluminum ingot in contact with the plating solution can be controlled to be minimum, and the disturbance of the plating solution in the zinc pot when adding the zinc-magnesium-aluminum ingot can be prevented as much as possible; the amount of the zinc-aluminum-magnesium ingot added is only required to ensure that the content requirements of each component in the plating solution are met.

[0034] In a specific embodiment of the present invention, the size of the added zinc-magnesium-aluminum ingot is: length×width×height=1180mm×600mm×200mm.

[0035] When adding zinc-magnesium-aluminum ingots, it is also necessary to control the speed of adding the zinc-magnesium-aluminum ingots at the same time. The speed of adding the zinc-magnesium-aluminum ingots is controlled according to formula (2) in step S3 to achieve slow addition of the ingots to prevent excessive single addition of zinc-aluminum-magnesium ingots, which would cause the temperature of the zinc liquid near the zinc-aluminum-magnesium ingots to drop sharply, causing the flow field of the zinc pot to be disturbed, stirring up zinc slag and attaching it to the surface of the steel strip.

[0036] Further in step S3 of the present invention, 1.5 mm ≤ t ≤ 2.5 mm, 275 g / m 2 ≤w≤450g / m 2 .

[0037] In the present invention, the gas source of the gas knife is an inactive gas, the purity of the gas is greater than 99.9%, and further the gas source of the gas knife is nitrogen.

[0038] In the preferred embodiment of the present invention, the air knife lip clearance is controlled to be 1-1.3 mm, the distance between the air knife lip and the strip steel is 14-25 mm, the air knife height is 180-250 mm, and the air knife pressure is 110-150 mbar.

[0039] A second aspect of the present invention provides a zinc-aluminum-magnesium coated steel sheet produced by the above production method.

[0040] The solution of the present invention is mainly for steel plate finished product thickness of 1.5-2.5mm, double-sided coating weight of 275-450g / m 2 For zinc-aluminum-magnesium coated steel plates, the generation and flow of zinc slag can be reduced by controlling the temperature of the zinc pot, the speed of adding ingots, the distance between the top of the diversion dam and the liquid surface of the plating solution, and the speed of the zinc slag pump, so as to eliminate the tooth mark defects on the surface of thick-specification and thick-layer zinc-aluminum-magnesium coated steel plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 is a schematic diagram of the zinc-aluminum-magnesium ingot added in the present invention;

[0042] Figure 2 This is the surface quality diagram of the zinc-aluminum-magnesium coated steel sheet produced in Example 1;

[0043] Figure 3 This is a surface quality diagram of the zinc-aluminum-magnesium coated steel sheet produced in Example 1. DETAILED DESCRIPTION

[0044] The specific implementation of the present invention is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described here is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0045] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0046] The composition of the zinc pot in the following embodiments and comparative examples is as follows: Al content is 5.8wt%, Mg content is 2.5wt%, and the rest is Zn and unavoidable impurities such as Fe; the composition of the added zinc-magnesium-aluminum ingot is the same as that of the zinc pot.

[0047] Example 1

[0048] A production method for eliminating tooth mark defects on the surface of zinc-aluminum-magnesium coated steel plates, the production method comprising:

[0049] S1. The annealing temperature of the strip is controlled to be 650°C. The temperature of the strip entering the zinc pot is controlled according to formula (1):

[0050] T2=T1-0.01v-0.005s (1)

[0051] In formula (1), the zinc pot temperature T1 is 460℃; the running speed v of the steel plate in the zinc pot is 75m / min; the cross-sectional area s of the strip is 1875mm 2(the product of t and c); the strip entering the zinc pot temperature T2 is calculated to be 450°C; and the operating power of the induction heater of the zinc pot is controlled to be 15KW;

[0052] S2, control the distance between the top of the diversion dam in the furnace nose and the plating solution surface to be 2mm, and the speed of the zinc slag pump to be 120 rpm;

[0053] S3. Control the feeding speed of zinc, aluminum and magnesium ingots according to formula (2):

[0054] v1=100×(2×c 2 ×t 2 ×w) / (v×8.47×10 8 ) (2)

[0055] In formula (2), the thickness t of the finished zinc-aluminum-magnesium coated steel plate is 1.5 mm; the width c of the finished zinc-aluminum-magnesium coated steel plate is 1250 mm; the double-sided coating weight w of the finished zinc-aluminum-magnesium coated steel plate is 350 g / m 2 ; The calculated ingot adding speed v1 of zinc-aluminum-magnesium ingot is 3.87cm / min; the added zinc-aluminum-magnesium ingot is in the shape of a rectangular parallelepiped, with a length × width × height of 1180mm × 600mm × 200mm, such as Figure 1 As shown, the zinc-aluminum-magnesium ingot is added into the plating solution along the length direction of the zinc-aluminum-magnesium ingot, and the composition of the zinc-aluminum-magnesium ingot is consistent with that of the zinc pot;

[0056] Among them, the air knife gas source is nitrogen, the gas purity is greater than 99.9%, the air knife lip gap is controlled to be 1.0mm, the distance between the lip and the strip is 14mm, the air knife height is 220mm, and the air knife pressure is 110mbar.

[0057] The specific process parameters of Examples 1-3 are shown in Tables 1 and 2 (the gas sources of the air knives are all nitrogen, and the gas purity is greater than 99.9%). Comparative Examples 1-3 are all implemented according to the production method of Example 1, and the process parameters are different from those of Example 1. The specific process parameters are shown in Tables 1 and 2 (the annealing temperature of the strip in Examples 2-3 and Comparative Examples 1-3 is 650°C).

[0058] Table 1

[0059]

[0060] Table 2

[0061]

[0062] Using the above production method, the zinc-aluminum-magnesium coated steel sheet produced in Example 1 has excellent surface quality and no tooth mark defects. Figure 2As shown; the zinc-aluminum-magnesium coated steel sheets produced in Examples 2-3 are similar to those in Example 1, and the surface quality is excellent, and there are no tooth mark defects; the zinc-aluminum-magnesium coated steel sheets produced in Comparative Example 1 have obvious tooth mark defects on the surface, such as Figure 3 As shown; the zinc-aluminum-magnesium coated steel plates produced in Comparative Examples 2-3 also have obvious tooth mark defects on their surfaces.

[0063] It can be seen that the present invention can reduce the generation and flow of zinc slag by controlling the process conditions, and effectively eliminate the tooth mark defects on the surface of thick-coated zinc-aluminum-magnesium coated steel plates.

[0064] It should be understood that parts not elaborated in detail in this specification belong to the prior art.

[0065] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A production method for eliminating tooth mark defects on the surface of zinc-aluminum-magnesium coated steel plates, characterized in that: The production method comprises: S1. Control the temperature of the strip entering the zinc pot according to formula (1): T2=T1-0.01v-0.005s (1) In formula (1), T2 represents the temperature of the steel strip entering the zinc pot; T1 represents the temperature of the zinc pot; v represents the speed of the steel plate in the zinc pot; s represents the cross-sectional area of ​​the steel strip; S2, control the distance between the top of the diversion dam in the furnace nose and the surface of the plating solution to be 2-5mm, and the speed of the zinc slag pump to be 80-120 rpm; S3. Control the feeding speed of zinc, aluminum and magnesium ingots according to formula (2): v1=100×(2×c 2 ×t 2 ×w) / (v×8.47×10 8 ) (2) In formula (2), v1 represents the ingot adding speed of zinc-aluminum-magnesium ingots; t represents the thickness of the finished zinc-aluminum-magnesium coated steel plate; c represents the width of the finished zinc-aluminum-magnesium coated steel plate; and w represents the double-sided coating weight of the finished zinc-aluminum-magnesium coated steel plate.

2. The production method according to claim 1, characterized in that The annealing temperature of the strip is controlled at 550-700°C.

3. The production method according to claim 1, characterized in that In step S1, 420°C ≤ T1 ≤ 460°C.

4. The production method according to claim 1 or 3, characterized in that: In step S1, the zinc pot contains the following components in weight percentage: Al content is 1-13wt%, Mg content is 1-6wt%, and the rest is Zn and unavoidable impurities.

5. The production method according to claim 1, characterized in that: In step S1, 65 m / min≤v≤75 m / min.

6. The production method according to claim 1, characterized in that: In step S1, the operating power of the zinc pot is 10-30KW.

7. The production method according to claim 1, characterized in that: In step S3, 1.5 mm ≤ t ≤ 2.5 mm, 275 g / m 2 ≤w≤450g / m 2 .

8. The production method according to claim 1, characterized in that: The air knife gas source is inactive gas.

9. The production method according to claim 1 or 8, characterized in that: Control the air knife lip gap to 1-1.3mm, the distance between the air knife lip and the strip to 14-25mm, the air knife height to 180-250mm, and the air knife pressure to 110-150mbar.

10. The zinc-aluminum-magnesium coated steel sheet produced by the production method according to any one of claims 1 to 9.

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