Air knife control method for producing super-thick plated aluminum-zinc-magnesium product

Abstract

The application relates to a gas-knife control method for producing super-thick plated aluminum-zinc-magnesium products, which comprises gas-knife lip opening degree control: the gas-knife lip is evenly divided into 14-18 equal parts, each equal part is regarded as a standard position, the bolt tightness of each standard position is adjusted, so that the gas-knife lip opening degree is adjusted to be 1.2-1.35 mm; gas-knife gas medium flow control: when the super-thick plated aluminum-zinc-magnesium products are produced, the gas-knife gas medium flow is not less than 3100 m 3 / h; gas-knife process parameters: (1) gas-knife height: when the super-thick plated products are produced, the gas-knife height is between 650-1050 mm; (2) gas-knife distance: when the super-thick plated products are produced, the gas-knife distance is between 22-30 mm; (3) gas-knife wind pressure: when the super-thick plated products are produced, the gas-knife wind pressure is between 60-200 mbar; without increasing equipment investment, the purpose of stably controlling zinc flow wave defects is achieved, the stable, high-quality and high-efficiency production of the super-thick plated aluminum-zinc-magnesium products is realized, and the stable operation of the unit and the product quality are ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cold rolling, in particular to a gas knife control method for suppressing production of super-thick plated aluminum-zinc-magnesium products. BACKGROUND

[0002] Aluminum-zinc-magnesium alloy plated product is a brand-new high corrosion resistance plated product developed in 2021, which combines the excellent corrosion resistance of aluminum and the cathodic corrosion protection of zinc. At the same time, the problem of poor notch protection of aluminum-zinc plated products is effectively solved by adding a certain amount of Mg element. Therefore, aluminum-zinc-magnesium steel plate has excellent atmospheric corrosion resistance, and its corrosion resistance is 8-10 times that of hot-dipped zinc steel plate with the same plated thickness. In addition, the aluminum-zinc-magnesium plated layer also shows good paintability, processability and excellent heat reflection performance. Due to its good comprehensive performance, the development of aluminum-zinc-magnesium products is very rapid, and it is widely used in the fields of construction, automobile, agriculture, household appliances, etc.

[0003] However, compared with conventional specifications of aluminum-zinc-magnesium alloy plated products, the super-thick plated aluminum-zinc-magnesium product has lower viscosity of aluminum-zinc-magnesium zinc liquid and better flowability than hot-dipped pure zinc zinc liquid during production. In the process of gas knife blowing, zinc flow wave defects are easily produced, which leads to unqualified surface quality of the product and cannot be delivered to the user, resulting in serious quality cost loss. In order to reduce the influence of low zinc liquid viscosity on the surface quality of super-thick plated aluminum-zinc-magnesium products, according to the research on the mechanism and process of plated layer cooling, the accurate control of plated layer cooling rate is the core key factor, and the gas knife lip opening degree, blowing medium and flow, gas knife height, gas knife distance and gas knife pressure are the core of the core. Therefore, in order to ensure the stable control of zinc flow wave defects of super-thick plated aluminum-zinc-magnesium products, realize the stable, high-quality and efficient production of such products, ensure the stable operation of the unit and the quality of the products meeting the requirements, it is necessary to specially study and innovate the process parameters such as gas knife lip opening degree, blowing medium and flow, gas knife height, gas knife distance and wind pressure of super-thick plated aluminum-zinc-magnesium products, form parameter algorithm formula based on automatic control, and write into gas knife control program, and finally form a comprehensive technical scheme. Through the implementation of the scheme, the function of automatically adjusting the key process parameters of the gas knife according to the real-time changes of the external key conditions such as the main line speed of the unit and the zinc liquid temperature is realized, the real-time accurate control of the gas knife parameters is achieved, the most reasonable plated layer cooling rate is ensured, and the automatic accurate control function of the zinc flow wave defects of all specifications of products is realized. Through the application of this method, the unqualified product rate caused by surface quality defects in the production process of such products is effectively reduced, the production cost is reduced, and the timely delivery of the contract is ensured.

[0004] The Chinese patent with publication number CN113430478A discloses a method for eliminating zinc wave defect of alloyed hot-dip galvanized steel sheet, which realizes the elimination of zinc wave defect of alloyed hot-dip galvanized steel sheet by controlling the temperature of zinc liquid in zinc pot and the temperature of strip entering the pot, controlling the mass percentage content of aluminum in zinc liquid and the running speed of strip, adjusting the air knife parameter, and controlling the rolling force of the finishing mill; the patent is a design of the whole zinc plating process technology scheme for alloyed hot-dip galvanized steel sheet, but the air knife process parameter is the main influencing factor of zinc flow wave defect, there is a lack of systematic technical scheme for the air knife process parameter, and there is no targeted innovative design for the zinc liquid flowability aiming at the feature of super-thick plating layer, therefore, it is not enough to support the control of zinc flow wave defect for super-thick plating layer aluminum-zinc-magnesium product.

[0005] The Chinese patent with publication number CN111534774A discloses a method for reducing hot-dip galvanized zinc flow wave defect, which includes 1) the speed of strip passing through the zinc pot is 65-95 m / min; 2) the air knife adopts air and nitrogen double purging mode, specifically as follows: a. the FC surface zinc-plated sheet adopts nitrogen purging; b. the FB surface with annealing temperature below 800℃: when the sheet thickness is ≥1.5 mm or the zinc layer thickness is ≥180 g / m 2 , nitrogen purging is adopted; c. the FB surface zinc-plated sheet with annealing temperature above 800℃: when the sheet thickness is ≥1.5 mm, the zinc layer thickness is ≥120 g / m 2 , or the sheet width is >1400 mm, the sheet thickness is ≥1.0 mm, or the zinc layer thickness is ≥180 g / m 2 , the plating layer with ≥180 g / m above adopts nitrogen purging; d. the FA surface adopts air purging; the main design content of the patent is the control method for suppressing zinc flow wave defect for producing hot-dip pure zinc plating layer product, and there is no involvement in the related control of 55% Al-Zn-Mg-1.6% Si alloy plating layer super-thick plating layer, and the parameters of air knife control are only different purging media for different specifications, and there is no detailed control of air knife parameters aiming at the aluminum-zinc-magnesium plating liquid flowability, therefore, it is also not enough to support the control of zinc flow wave defect for super-thick plating layer aluminum-zinc-magnesium product. SUMMARY

[0006] The present application provides an air knife control method for suppressing zinc flow wave defect of super-thick plating layer aluminum-zinc-magnesium product, which achieves the purpose of suppressing zinc flow wave defect without increasing equipment investment, realizes stable, high-quality and efficient production of super-thick plating layer aluminum-zinc-magnesium product, and ensures stable operation of the unit and that the product quality meets the requirements.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] An air knife control method for producing super-thick plating layer aluminum-zinc-magnesium product, which includes the following contents:

[0009] 1) Air knife lip opening control: the air knife lip is evenly divided into 14-18 equal parts, each equal part is a standard position, and the tightness of the bolt at each standard position is adjusted to adjust the air knife lip opening to 1.2-1.35 mm;

[0010] 2) Air knife gas medium flow control: when producing super-thick plated aluminum-zinc-magnesium products, the air knife gas medium uses nitrogen, and the nitrogen flow is not less than 3100 m 3 / h;

[0011] 3) Air knife process parameters:

[0012] (1) Air knife height: when producing super-thick plated products, the air knife height is between 650-1050 mm;

[0013] The air knife height is calculated based on the zinc liquid temperature T and the unit speed V, and the formula is as follows:

[0014] H=a*T*1000-b*V (1)

[0015] Wherein, a is the zinc liquid temperature coefficient, b is the unit speed coefficient, T is the actual temperature of the zinc liquid, unit ℃, V is the actual speed of the unit, unit m / min, H is the air knife height, unit mm;

[0016] (2) Air knife distance: when producing super-thick plated products, the air knife distance is between 22-30 mm;

[0017] The air knife distance is calculated based on the zinc liquid temperature T and the unit speed V, and the formula is as follows:

[0018] D=a*T*30-b*V / 100 (2)

[0019] Wherein, D is the air knife distance, unit mm;

[0020] (3) Air knife wind pressure: when producing super-thick plated products, the air knife wind pressure is between 60-200 mbar;

[0021] The air knife wind pressure is calculated based on the zinc liquid temperature T and the unit speed V, and the formula is as follows:

[0022] P=c*T*15+d*V / 2 (3)

[0023] Wherein, c is the zinc liquid temperature coefficient, d is the unit speed coefficient, P is the air knife wind pressure, unit mbar.

[0024] Further, the double-sided plated thickness of the super-thick plated aluminum-zinc-magnesium product is 180-280 g / m 2 .

[0025] Further, the gas knife lip opening degree takes the opening degree of the center 4-6 positions in the length direction of the gas knife lip as the reference value, the opening degree is set to 1.2±0.005mm, then the opening degree of the adjacent positions is increased in turn with the increasing gradient of 0.025mm symmetrically to both sides, the control accuracy of each position is ±0.005mm, and the opening degree of the two positions at the most edge is not more than 1.35mm.

[0026] Further, the zinc liquid temperature coefficient a is valued according to the actual temperature T of the zinc liquid: when 575≤T<585, a=0.0013-0.0014; when 585≤T<590, a=0.0015-0.0016; when 590≤T<603, a=0.0017-0.0018.

[0027] The unit speed coefficient b is valued according to the unit speed V: when 120≤V<145, b=0.98-1.12; when 100≤V<120, b=0.83-0.97; when 80≤V<100, b=0.55-0.82; when 55≤V<80, b=0.38-0.54.

[0028] 5, Further, the zinc liquid temperature coefficient c is valued according to the actual temperature T of the zinc liquid: when 575≤T<585, c=0.016-0.019; when 585≤T<590, c=0.008-0.015; when 590≤T<603, c=0.004-0.007.

[0029] The unit speed coefficient d is valued according to the unit speed V: when 120≤V<145, d=0.31-0.41; when 100≤V<120, d=0.42-0.56; when 80≤V<100, d=0.57-0.73; when 55≤V<80, d=0.74-0.88.

[0030] Compared with the prior art, the beneficial effects of the present application are:

[0031] By optimizing the gas knife lip opening degree, blowing medium and flow, gas knife height, gas knife distance and wind pressure and other related process parameters, under the premise of not increasing the equipment investment, when producing the super-thick plated aluminum zinc magnesium product, the purpose of stably controlling the zinc flow ripple defect is achieved, the stable high-quality and efficient production of the super-thick plated aluminum zinc magnesium product is realized, the stable operation of the unit is ensured, and the product quality meets the requirements. DETAILED DESCRIPTION

[0032] The specific embodiments of the present application are further described below:

[0033] The application discloses a kind of air knife control methods for suppressing production of super-thick plated aluminum-zinc-magnesium product, and the double-sided coating thickness of super-thick plated aluminum-zinc-magnesium product is 180-280 g / m 2 The air knife process parameter control specifically includes the following contents:

[0034] 1) Air knife lip opening degree control: divide the air knife lip into 14-18 equal parts on average, take each equal part as a standard position, adjust the bolt tightness of each standard position to adjust the air knife lip opening degree to 1.2-1.35 mm, the air knife lip opening degree is taken as the opening degree of 4-6 positions in the center of the lip length direction as a reference value, which is set to 1.2±0.005 mm, then symmetrically increase the air knife lip opening degree of adjacent positions by 0.025 mm in turn, the control accuracy of each position is ±0.005 mm, and the opening degree of the two positions on the most edge is not more than 1.35 mm, as shown in Table 1,

[0035] Table 1

[0036] Position 0 1 2 3 4 5 6-11 12 13 14 15 16 17 Opening (mm) 1.35 1.325 1.3 1.275 1.25 1.2 1.225 1.25 1.275 1.3 1.3 1.325 1.35

[0037] 2) Air knife gas medium flow control:

[0038] (1) Medium type: when producing super-thick plated aluminum-zinc-magnesium product, the air knife medium is nitrogen;

[0039] (2) Medium flow: the air knife gas medium flow is not less than 3100 m 3 / h.

[0040] 3) Air knife process parameters:

[0041] (1) Air knife height: in order to ensure that the coating has no flowability after being blown by the air knife blowing plane, the air knife height needs to be limited, and the air knife height control range is generally 650-1050 mm; at the same time, the air knife height is calculated based on the zinc liquid temperature T and the unit speed V, and the formula is as follows:

[0042] H=a*T*1000-b*V (4)

[0043] Wherein, a is the zinc liquid temperature coefficient, b is the unit speed coefficient, T is the actual temperature of the zinc liquid, the unit is ℃, V is the actual speed of the unit, the unit is m / min, H is the air knife height, the unit is mm, and the assignment range of the zinc liquid temperature coefficient a and the unit speed coefficient b is shown in Table 1 and Table 2:

[0044] Table 1 Assignment range table of zinc liquid temperature coefficient a

[0045] Zinc bath temperature T range (°C) a value 575≤T＜585 0.0013 585≤T＜590 0.0015 590≤T＜603 0.0017

[0046] Table 2 Assignment range table of unit speed coefficient b

[0047] Machine speed V range (m / min) b value 120≤V＜145 1.12 100≤V＜120 0.97 80≤V＜100 0.82 55≤V＜80 0.54

[0048] (2) Air knife distance: In order to effectively improve the air knife wind pressure, when producing super-thick plated products, in order to ensure that the air knife has sufficient blowing airflow momentum, the air knife distance is between 22-30 mm; at the same time, the air knife distance is calculated based on the zinc liquid temperature T and the machine set speed V, and the formula is as follows:

[0049] D = a * T * 30 - b * V / 100 (5)

[0050] Wherein, D is the air knife distance, unit mm; the assignment range of zinc liquid temperature coefficient a and machine set speed coefficient b is the same as table 1 and table 2;

[0051] (3) Air knife wind pressure: when producing super-thick plated products, in order to ensure that the air knife has sufficient blowing airflow momentum and has sufficient cooling capacity to the plated layer, the air knife wind pressure is between 60-200 mbar; at the same time, the air knife wind pressure is calculated based on the zinc liquid temperature T and the machine set speed V, and the formula is as follows:

[0052] P = c * T * 15 + d * V / 2 (6)

[0053] Wherein, c is the zinc liquid temperature coefficient, d is the machine set speed coefficient, P is the air knife wind pressure, unit mbar; the assignment range of zinc liquid temperature coefficient c and machine set speed coefficient d is shown in table 3 and table 4;

[0054] Table 3 zinc liquid temperature coefficient c assignment range table

[0055] Zinc bath temperature T range (°C) c value 575≤T＜585 0.019 585≤T＜590 0.015 590≤T＜603 0.007

[0056] Table 4 machine set speed coefficient d assignment range table

[0057] Machine speed V range (m / min) d value 1 0.5 50-60 0.5 0.5 50-60 0.5 0.5 2 0.5 50-60 0.5 0.5 50-60 0. 120≤V＜145 0.31 100≤V＜120 0.42 80≤V＜100 0.57 55≤V＜80 0.74

[0058] For different specifications and different plated thickness products, the control qualified rate of the air knife process parameters reaches the purpose of stable control of zinc flow ripple defects, as shown in table 5,

[0059] Table 5

[0060]

[0061] The above examples are implemented on the premise of the technical scheme of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the above examples. The methods used in the above examples are all conventional methods unless otherwise specified.

Claims

1. A method for controlling an air knife in the production of ultra-thick coated aluminum-zinc-magnesium products, characterized in that, Includes the following: 1) Control of air knife lip opening: Divide the air knife lip into 14 to 18 equal parts, with each part as a standard position. Adjust the tightness of the bolts at each standard position to adjust the air knife lip opening to 1.2 to 1.35 mm. 2) Air knife gas medium flow control: When producing ultra-thick coated aluminum-zinc-magnesium products, the air knife gas medium is nitrogen, and the nitrogen flow rate is not less than 3100 m³ / h. 3 / h; 3) Air knife process parameters: (1) Air knife height: When producing ultra-thick coating products, the air knife height is between 650 and 1050 mm; The air knife height is calculated based on the zinc liquid temperature T and the unit speed V, using the following formula: H=a*T*1000-b*V (1) Where a is the zinc liquid temperature coefficient, b is the unit speed coefficient, T is the actual zinc liquid temperature in °C, V is the actual unit speed in m / min, and H is the air knife height in mm. (2) Air knife distance: When producing ultra-thick coating products, the air knife distance is between 22 and 30 mm; The air knife distance is calculated based on the zinc liquid temperature T and the unit speed V, using the following formula; D=a*T*30-b*V / 100 (2) Where D is the air knife distance, in mm; (3) Air knife pressure: When producing ultra-thick coated products, the air knife pressure is between 60 and 200 mbar; The air knife pressure is calculated based on the zinc liquid temperature T and the unit speed V, using the following formula: P = c * T * 15 + d * V / 2 (3) Where c is the zinc liquid temperature coefficient, d is the unit speed coefficient, and P is the air knife pressure in mbar.

2. The air knife control method for producing ultra-thick coated aluminum-zinc-magnesium products according to claim 1, characterized in that, The double-sided coating thickness of the ultra-thick aluminum-zinc-magnesium products is 180-280 g / m. 2 .

3. The air knife control method for producing ultra-thick coated aluminum-zinc-magnesium products according to claim 1, characterized in that, The opening degree of the air knife lip is based on the opening degree at the center of the 4th to 6th positions along the length of the lip, which is set to 1.2 ± 0.005 mm. Then, the opening degree of the air knife lip at adjacent positions is increased symmetrically to both sides in increments of 0.025 mm. The control accuracy of each position is ± 0.005 mm, and the opening degree at the two outermost positions does not exceed 1.35 mm.

4. The air knife control method for producing ultra-thick coated aluminum-zinc-magnesium products according to claim 1, characterized in that, The zinc liquid temperature coefficient 'a' is determined based on the actual zinc liquid temperature 'T': when 575 ≤ T < 585, a = 0.0013 ~ 0.0014; when 585 ≤ T < 590, a = 0.0015 ~ 0.0016; when 590 ≤ T < 603, a = 0.0017 ~ 0.0018. The unit speed coefficient b is determined based on the unit speed V: when 120≤V<145, b=0.98~1.12; when 100≤V<120, b=0.83~0.97; when 80≤V<100, b=0.55~0.82; when 55≤V<80, b=0.38~0.

54.

5. The air knife control method for producing ultra-thick coated aluminum-zinc-magnesium products according to claim 1, characterized in that, The zinc liquid temperature coefficient c is determined based on the actual zinc liquid temperature T: when 575≤T<585, c=0.016~0.019; when 585≤T<590, c=0.008~0.015; when 590≤T<603, c=0.004~0.

007. The unit speed coefficient d is determined based on the unit speed V: when 120≤V<145, d=0.31~0.41; when 100≤V<120, d=0.42~0.56; when 80≤V<100, d=0.57~0.73; when 55≤V<80, d=0.74~0.88.

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