Hot dipping production method of high-grade surface aluminum-zinc plated steel plate

Abstract

The invention relates to the technical field of steel rolling, in particular to a hot dipping production method of a high-grade surface aluminum-zinc plated steel plate, which comprises the following steps of: arranging a heating device and a temperature detection device on a lower chute of an annealing furnace, calling a temperature set value of the lower chute of the annealing furnace as a control value according to the thickness of strip steel, and adjusting the power of the heating device according to an actual value of the temperature detection device; the temperature of the lower chute of the annealing furnace is constant; the strip steel is in a non-shaking state according to the magnetic adsorption torque; the Fe element is promoted to be separated out in the form of zinc slag by utilizing a mode of repeatedly increasing and decreasing the temperature of a plating solution in a production intermission period; and the concentration of the finishing liquid is judged through an on-line conductivity detection device. The method has the advantages that on the premise that equipment investment is not greatly increased, the occurrence probability of the problems such as uneven spangles on the surface of the high-grade surface hot-dip aluminum-zinc product, zinc dross, zinc ash and finishing chromatic aberration which seriously affect the surface quality of the product is reduced, high-quality and high-efficiency production of the high-grade surface hot-dip aluminum-zinc product is achieved, and the production cost is reduced. And stable operation of the unit and product quality meeting requirements are ensured.

Description

Technical Field

[0001] The invention relates to the technical field of steel rolling, and in particular to a hot-dip plating production method for a high-grade surface aluminum-zinc-plated steel plate. Background Art

[0002] At present, all major steel enterprises generally adopt the modified Sendzimir process and the US Steel Union process to produce hot-dip galvanized (55% AL~1.6% Si~Zn) steel plates. Because galvanized products have excellent corrosion resistance, and the surface has a strong three-dimensional zinc flower, the appearance decoration effect is excellent, and the painting process can be eliminated. For users, it can not only increase the service life, but also reduce the cost and environmental pressure caused by painting. Therefore, galvanized products are very popular in industries such as home appliance manufacturers and electric control cabinet manufacturers, and the market demand is huge. However, due to the influence of the plating solution composition, process and equipment of hot-dip galvanized (55% AL~1.6% Si~Zn) products, it is difficult to stably produce galvanized products with high-level surface quality, especially due to the influence of variables such as specification changes, speed changes, temperature changes during production scheduling, as well as changes in coating thickness, fluctuations in plating solution temperature and composition, and fluctuations in furnace atmosphere, it is very easy to have problems such as uneven surface zinc flowers, zinc slag and zinc ash, and color difference in finishing that seriously affect the surface quality of the product. The key to determining the surface quality of products and the quality of coating adhesion is the precise control and timely adjustment of process parameters. Therefore, this patent conducts in-depth research and innovation on how to optimize the linkage control function of equipment and process parameters based on the improvement of the intelligent level of equipment, so as to achieve fine control of key process parameters, reduce surface defects of finished products, and achieve high-quality and efficient production of hot-dip aluminum-zinc products with advanced surface quality without significantly increasing equipment investment, thus ensuring stable operation of the unit and product quality that meets requirements.

[0003] In the prior art, the patent application number is CN201210525392.4, and the patent name is "A method for removing slag from an aluminum-zinc pool in a continuous aluminum-zinc plating production line", which is characterized in that: a high-speed aluminum-zinc pump (2) is connected to an aluminum-zinc plating pool (18) through an aluminum-zinc liquid inlet pipe (1), and the high-speed aluminum-zinc liquid is sprayed into a centrifugal cyclone body (8) at a high speed from an inlet (4) of the centrifugal cyclone through a guide pipe (3), and the aluminum-zinc liquid separates the aluminum-zinc slag contained in the centrifugal cyclone under the action of the centrifugal cyclone; the purified aluminum-zinc liquid flows back to the aluminum-zinc plating pool (18) through an overflow pipe (5) at a top cover (6) of the centrifugal cyclone; the separated aluminum-zinc slag flows through a valve (12) on a centrifugal cyclone base (10) and through a slag discharge pipe (12). 4) enters the aluminum-zinc slag collector (15) to complete the slag removal process of the aluminum-zinc liquid; when there is excessive aluminum-zinc slag in the aluminum-zinc slag collector, it can be refluxed to the aluminum-zinc plating pool (18) through the reflux pipe (16); wherein the high-speed aluminum-zinc pump (2), the centrifugal cyclone inlet (4), the centrifugal cyclone top cover (6), the centrifugal cyclone body (8), the aluminum-zinc liquid inlet pipe (1), the guide pipe (3), the overflow pipe (5) and the slag discharge pipe (14) are assembled and preheated to 600-650° C.; the high-speed aluminum-zinc pump (2) is immersed in the aluminum-zinc pool (18) before starting, and the immersion depth is 50-80 cm; the high-speed aluminum-zinc pump (2) needs to be immersed in the aluminum-zinc liquid for about 5-15 minutes to fully dissolve the aluminum-zinc liquid remaining in the high-speed aluminum-zinc pump (2). The main design contents of this patent are basically methods and devices for simply removing zinc slag from the zinc pot. It lacks other technical solutions related to the overall quality control of high-quality surface-plated aluminum-zinc products. At the same time, the method it adopts is only to remove the existing zinc slag in the zinc pot, but does not consider the solution of reducing the Fe content to eliminate the hidden dangers of zinc slag regeneration. Therefore, it is not sufficient to support the control of stable production of high-quality surface-plated aluminum-zinc products.

[0004] The application number is CN202110694253.3, and the patent name is "A hot-dip galvanized sheet production process monitoring system". It is characterized by including: a hot-dip galvanized sheet production monitoring host and an galvanized monitoring terminal; the hot-dip galvanized sheet production monitoring host includes: a data acquisition module, a hot-dip galvanized process data processing module, a hot-dip galvanized data adjustment module and a hot-dip galvanized process data output module; the data acquisition module is used to obtain the production process data information of the hot-dip galvanized sheet; the hot-dip galvanized process data processing module is used to store the production process data information of the hot-dip galvanized sheet, and compare to determine whether the corresponding threshold value is exceeded, and issue an alarm prompt; the hot-dip galvanized data adjustment module is used to obtain the user's production process data information of the hot-dip galvanized sheet Adjust the control instructions and adjust the process data; the hot-dip galvanizing process data output module is used to display the production process data information of the hot-dip galvanizing plate, and also display the alarm information; the monitoring personnel carry the galvanizing monitoring terminal, communicate with the hot-dip galvanizing plate production monitoring host through the galvanizing monitoring terminal, and obtain the hot-dip galvanizing process data through the hot-dip galvanizing plate production monitoring host; the galvanizing monitoring terminal receives the hot-dip galvanizing monitoring data input by the monitoring personnel, and uploads it to the hot-dip galvanizing plate production monitoring host; the hot-dip galvanizing plate production monitoring host sends a collection instruction to the hot-dip galvanizing equipment, and within the first hot-dip galvanizing data collection time after obtaining the collection instruction, the fluctuation range of the hot-dip galvanizing process data is greater than the fluctuation range of the hot-dip galvanizing equipment; The galvanized sheet production monitoring host locates the galvanized monitoring terminal in real time, and locates the galvanized monitoring terminal within the second hot-dip galvanized data collection time before the collection instruction; it is used to determine the position of the galvanized monitoring terminal, and to determine whether it is near the hot-dip galvanized equipment where the data fluctuation of the hot-dip galvanized production process exceeds the threshold; if the galvanized monitoring terminal is not in the hot-dip galvanized equipment where the fluctuation of the hot-dip galvanized production process exceeds the threshold, no reminder information is sent; according to the preset hot-dip galvanized production process judgment rules, it is determined whether the galvanized monitoring terminal needs to receive the hot-dip galvanized production process information; the hot-dip galvanized sheet production monitoring host obtains the hot-dip galvanized process monitoring log of the galvanized monitoring terminal; extracts Output the keywords of the hot-dip galvanizing production process; determine whether the number of occurrences of the keywords of the hot-dip galvanizing production process exceeds the preset threshold; if the number of occurrences of the keywords of the hot-dip galvanizing production process exceeds the threshold, determine that the galvanizing monitoring terminal needs to receive the hot-dip galvanizing production process information corresponding to the number of occurrences; the hot-dip galvanizing sheet production monitoring host determines whether the galvanizing monitoring terminal needs to receive the hot-dip galvanizing production process information according to the preset hot-dip galvanizing production process judgment rules; if the galvanizing monitoring terminal does not need to receive the hot-dip galvanizing production process information, determine whether the hot-dip galvanizing production process information of the hot-dip galvanizing equipment within the first hot-dip galvanizing data collection time after the collection instruction exists in the preset over-threshold hot-dip galvanizing production data table;If it exists in the super-threshold hot-dip galvanizing production data table, the time point when the hot-dip galvanizing equipment exceeds the threshold is obtained, and the hot-dip galvanizing equipment's hot-dip galvanizing production process information is actively sent to the galvanizing monitoring terminal. The main design content of this patent is basically to compare the galvanizing unit information to determine whether it corresponds to the super-threshold, but it does not involve the parameter setting of key process equipment, the linkage control with the main line material specifications, and the overall quality control of galvanized sheets. Therefore, it is not enough to support the control of stable production of advanced surface galvanized products. ;

[0005] The application number is CN202310036870.3, "A solid-liquid boundary line automatic control type aluminum-zinc plating sheet production line", which is characterized by: comprising a controller, an aluminum-zinc liquid hot-dip bath and a post-plating quick cooling box, an air knife assembly is provided at the lower end of the post-plating quick cooling box, and a water mist high-pressure nozzle assembly and a camera are provided on the side wall of the post-plating quick cooling box, the water mist high-pressure nozzle assembly is connected to a high-pressure water pipeline, and a flow regulating solenoid valve is installed on the high-pressure water pipeline; the water mist high-pressure nozzle assembly is located above the camera to spray water mist onto the hot-dip plate; the camera is located above the air knife assembly to detect the position of the solid-liquid boundary line on the surface of the plate after hot-dip, the plate enters the aluminum-zinc liquid hot-dip bath for hot-dip, and the hot-dip plate is passed through the air knife assembly After the plate enters the post-plating quick cooling box, the camera transmits the position information of the solid-liquid dividing line to the controller, and the controller controls the flow regulating solenoid valve to adjust the cooling speed of the post-plating quick cooling box to the hot-dip plate, so as to adjust the actual position of the solid-liquid dividing line to the predetermined position; when the actual position of the solid-liquid dividing line is too low, the cooling speed of the post-plating quick cooling box to the hot-dip plate is reduced; when the actual position of the solid-liquid dividing line is too high, the cooling speed of the post-plating quick cooling box to the hot-dip plate is increased; the predetermined position of the solid-liquid dividing line is 2.3 to 3.9 m above the air knife assembly, and the predetermined position of the solid-liquid dividing line is related to the thickness of the hot-dip plate. When the thickness of the plate is thicker, the predetermined position of the solid-liquid dividing line is higher. When the plate thickness is 0.2, the preset plating solution temperature is 614-615°C; when the plate thickness is 0.4, the preset plating solution temperature is 612-613°C; when the plate thickness is 0.6, the preset plating solution temperature is 611-612°C; when the plate thickness is 0.8, the preset plating solution temperature is 610-611°C; when the plate thickness is 1.0, the preset plating solution temperature is 609-610°C; when the plate thickness is 1.2-1.5, the preset plating solution temperature is 608-609°C; when the plate thickness is 2.0-2.5, the preset plating solution temperature is 607-608°C. The main design content of this patent is basically to control the cooling rate of the coating simply by the height of the solid-liquid dividing line. The core is only to control the size and appearance of zinc flowers, but it does not involve how to systematically control various defects such as zinc slag, zinc ash, and finishing color difference. Therefore, it is not enough to support the stable production control of high-end surface aluminum-zinc plating products. Summary of the invention

[0006] The purpose of the present invention is to provide a method for producing a high-grade surface aluminum-zinc coated substrate, to ensure the stable production of high-grade surface hot-dip aluminum-zinc products, to reduce the probability of surface defects, to reduce the adhesion defects and shutdown accidents of the finished product coating without significantly increasing the equipment investment, to ensure the high-quality and efficient production of high-grade surface hot-dip aluminum-zinc products, to ensure the stable operation of the unit and the compliance of the product quality with the requirements.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A hot-dip production method for high-grade surface aluminum-zinc coated steel sheet, comprising:

[0009] S1. The lower chute of the annealing furnace is equipped with a heating device and a temperature detection device. The temperature setting value of the lower chute of the annealing furnace is called as the control value according to the thickness of the strip steel, and the power of the heating device is adjusted according to the actual value of the temperature detection device to make the temperature of the lower chute of the annealing furnace constant;

[0010] S2. Add an electromagnetic detection device in the post-cooling section to detect the edge-middle-edge distance of the strip, control the magnetic output value of the upper and lower surface electromagnets of the corresponding area of ​​the lower chute of the annealing furnace, and keep the strip in a non-shaking state according to the magnetic adsorption torque;

[0011] If 0.35≤t<0.50, I=120*t+10, the deflection distance range setting value of the strip steel on the OS side is ±2.0, the deflection distance range setting value of the middle strip steel is ±1.0, and the deflection distance range setting value of the strip steel on the DS side is ±2.0;

[0012] If 0.50≤t<0.80, I=120*t+20, the deflection distance range setting value of the strip steel on the OS side is ±2.5, the deflection distance range setting value of the middle strip steel is ±1.5, and the deflection distance range setting value of the strip steel on the DS side is ±2.5;

[0013] If 0.80≤t<1.10, I=100*t+40, the deflection distance range setting value of the strip steel on the OS side is ±3.0, the deflection distance range setting value of the middle strip steel is ±2.0, and the deflection distance range setting value of the strip steel on the DS side is ±3.0;

[0014] If 1.10≤t<1.5, I=100*t+50, the deflection distance range setting value of the strip steel on the OS side is ±4.0, the deflection distance range setting value of the middle strip steel is ±3.0, and the deflection distance range setting value of the strip steel on the DS side is ±4.0;

[0015] If 1.50≤t<2.00, I=90*t+50, the deflection distance range setting value of the strip steel on the OS side is ±4.5, the deflection distance range setting value of the middle strip steel is ±4.0, and the deflection distance range setting value of the strip steel on the DS side is ±4.5;

[0016] If 2.00≤t<2.50, I=90*t+60, the deflection distance range setting value of the strip steel on the OS side is ±5.0, the deflection distance range setting value of the middle strip steel is ±5.0, and the deflection distance range setting value of the strip steel on the DS side is ±5.0;

[0017] t represents the strip thickness in mm, I represents the output current value of the electromagnet magnetic force control in A;

[0018] S3, according to the solubility of Fe element in aluminum-zinc solution changes with temperature, and has irreversible property that it cannot be dissolved again after precipitation, the plating solution temperature is raised and lowered by reciprocating cycle 4-6 times during the production interval, so as to promote the precipitation of Fe element in the form of zinc slag, and the precipitated zinc slag is fished out;

[0019] Step 1: The target temperature of the zinc pot is set to 610℃, the allowable fluctuation range of the temperature setting value is ±5℃, and the holding time is 4h;

[0020] Step 2: The target temperature of the zinc pot is set to 600°C, the allowable fluctuation range of the temperature setting value is ±3°C, and the holding time is 3h;

[0021] Step 3: The target temperature of the zinc pot is set to 590°C, the allowable fluctuation range of the temperature setting value is ±2°C, and the holding time is 3h;

[0022] Step 4: The target temperature of the zinc pot is set to 610°C, the allowable fluctuation range of the temperature setting value is ±5°C, and the holding time is 5h;

[0023] Step 5: The target temperature of the zinc pot is set to 590°C, the allowable fluctuation range of the temperature setting value is ±3°C, and the holding time is 5h;

[0024] Step 6: The target temperature of the zinc pot is set to 580°C, the allowable fluctuation range of the temperature setting value is ±2°C, and the holding time is 5h;

[0025] S4. Determine the concentration of the finishing liquid by an online conductivity detection device.

[0026] In S1, the strip thickness calls the annealing furnace lower chute temperature setting value, which is based on the online strip thickness, queries the thickness-temperature data already entered in the system database, and selects the lower chute temperature data corresponding to the current online strip thickness as the annealing furnace lower chute temperature setting value;

[0027] The power of the heating device is adjusted according to the actual value of the temperature detection device. The temperature detection device compares the actual temperature value detected with the temperature setting value. When the difference between the actual temperature value detected and the temperature setting value exceeds -5°C, the heating device increases the power output value. When the difference between the actual temperature value detected and the temperature setting value exceeds +5°C, the heating device reduces the power output value.

[0028] In S2, the distance between the edge of the strip and the center of the strip, "center" is the position that coincides with the center line in the width direction of the strip, and "edge" is the position along the width direction of the strip from the center line to the two sides at a set distance;

[0029] The magnitude of the magnetic adsorption torque is proportional to the magnetic output value. By adjusting the magnetic output value of the electromagnet, the magnetic adsorption torque generated on various parts of the strip can be balanced. At this time, the combined torque of the torque applied to the strip in the running direction (longitudinal) and the width direction (transverse) are both in a balanced state, and the strip will remain stable without shaking.

[0030] In S1, the heating device is a plurality of groups of resistance heating belts, which are evenly distributed on the inner arms of the upper and lower surfaces of the lower chute of the annealing furnace, and centralized heating is adopted; the temperature detection device is a thermocouple, which is arranged on the transmission side of the unit on the upper and lower surfaces of the lower chute of the annealing furnace.

[0031] The power range of each set of resistance heating belt is 600~800kw.

[0032] In S1, the lower chute of the annealing furnace is a passage connecting the outlet of the annealing furnace and the zinc pot, and the strip steel passes through the lower chute of the annealing furnace.

[0033] In S4, the correspondence between the online conductivity of the finishing liquid and the actual finishing liquid concentration is calculated. It is only necessary to measure the correspondence between the finishing liquid concentration and the conductivity at room temperature (25°C). The relationship between the finishing liquid concentration and the conductivity is as follows:

[0034] Y=-20.63X 2 +315.5X+8.405 ①

[0035] In formula ①, Y represents the conductivity of the finishing solution, the unit is us / cm, and X represents the concentration of the finishing solution, the unit is %;

[0036] The real-time data detected by the online conductivity detection device is used to determine whether the concentration of the finishing liquid is within the set value range, and to control the start and stop and operating time of the finishing liquid proportioning pump.

[0037] In S4, the conductivity detection device is arranged in the light-smoothing circulation box.

[0038] The chemical composition of the substrate is calculated by mass percentage as follows: C 0.001% to 0.80%, Si 0.001% to 2.2%, Mn 0.06% to 10.50%, P ≤ 0.04%, S ≤ 0.04%, Al 0.02% to 3.00%, Ti ≤ 0.20%, B ≤ 0.005%, Cr 0.03% to 0.70%; Mo 0.01% to 1.60%, Cu ≤ 0.70%, Ni 0.15% to 1.2%, Nb ≤ 0.08%; the rest is Fe and unavoidable impurities.

[0039] The chemical composition of the galvanized coating is as follows by mass percentage: Al 55%~65%, Si 1.2%~15%; Ti 0.03%~0.50%, Re 0.01%~0.20%, Li 0.05%~3%, Cu 0.1%~5.0%, Fe 0.03%~1.0%, Mn 0.5%~3.0%, Ni 0.5%~4.0%, V 0.01%~0.5%, Zr 0.5%~1.0%, Cr 0.1%~1.0%; the rest is Zn and unavoidable impurities.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] By optimizing the precise control equipment and process parameter scheme of the lower chute temperature of the galvanizing unit, through the equipment and process scheme for controlling the stability of the strip in the post-cooling section, and the transformation of the zinc pot slag removal equipment and methods, without significantly increasing the equipment investment, the probability of problems that seriously affect the surface quality of high-level hot-dip galvanized products, such as uneven zinc spangles, zinc slag and zinc ash, and color difference in finishing, can be reduced, and high-quality and efficient production of high-level hot-dip galvanized products can be achieved, ensuring stable unit operation and compliance with product quality requirements. DETAILED DESCRIPTION

[0042] The present invention is described in detail below, but it should be noted that the implementation of the present invention is not limited to the following embodiments.

[0043] The following examples are implemented on the premise of the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following examples. The methods used in the following examples are conventional methods unless otherwise specified.

[0044] [Example 1]

[0045] A hot-dip production method for high-grade surface aluminum-zinc coated steel sheet, applicable to the following requirements for the chemical composition of the substrate and coating:

[0046] The chemical composition of the substrate is calculated by mass percentage as follows: C 0.001% to 0.80%, Si 0.001% to 2.2%, Mn 0.06% to 10.50%, P ≤ 0.04%, S ≤ 0.04%, Al 0.02% to 3.00%, Ti ≤ 0.20%, B ≤ 0.005%, Cr 0.03% to 0.70%; Mo 0.01% to 1.60%, Cu ≤ 0.70%, Ni 0.15% to 1.2%, Nb ≤ 0.08%; the rest is Fe and unavoidable impurities;

[0047] The chemical composition of the galvanized coating is as follows by mass percentage: Al 55% ~ 65%, Si 1.2% ~ 15%; Ti 0.03% ~ 0.50%, Re 0.01% ~ 0.20%, Li 0.05% ~ 3%, Cu 0.1% ~ 5.0%, Fe 0.03% ~ 1.0%, Mn 0.5% ~ 3.0%, Ni 0.5% ~ 4.0%, V 0.01% ~ 0.5%, Zr 0.5% ~ 1.0%, Cr 0.1% ~ 1.0%; the rest is Zn and unavoidable impurities.

[0048] The production method of high-grade surface aluminum-zinc clad substrate is as follows:

[0049] S1, Annealing furnace lower chute temperature control

[0050] In order to ensure that the ambient temperature in the lower chute is between 560 and 600°C and to prevent the aluminum-zinc plating solution from evaporating and condensing on the inner wall of the lower chute to form solid zinc ash foreign matter, a heating device and a temperature detection device are added to the lower chute area. The specific plan is as follows:

[0051] Three groups of resistance heating belts are evenly distributed on the inner wall of the upper and lower surfaces, and the power of each group is 600-800Kw. A centralized control mode is adopted without partitioning. At the same time, a temperature setting interface for the lower chute area is added to the main line control screen, and the control mode is set to manual / automatic. The set temperature is adjustable within the range of 550-610℃, and the setting accuracy is 1℃. A temperature measuring thermocouple is installed on the transmission side of the unit on the upper and lower surfaces of the lower chute, and the temperature display interface is set on the main line screen. At the same time, a program is compiled. When the automatic control mode is selected, the PLC / DCS system calls the temperature setting value of the lower chute area of ​​the annealing furnace as the control value according to the thickness of the strip, and adjusts the power of the resistance heating belt according to the actual value detected by the thermocouple, so as to realize constant control of the temperature of the lower chute area and reduce the strip zinc ash defects formed on the surface of the strip due to the zinc ash falling. The specific data table of the lower chute temperature setting value determined according to the strip thickness is shown in Table 1.

[0052] Table 1 is the temperature setting table for the lower chute.

[0053] Strip thickness t(mm) Lower chute temperature setting value (℃) Allowable fluctuation range (℃) 0.35≤t＜0.50 600 ±3 0.50≤t＜0.80 595 ±4 0.80≤t＜1.10 593 ±5 1.10≤t＜1.5 590 ±5 1.50≤t＜2.00 586 ±6 2.00≤t＜2.50 583 ±6

[0054] In Table 1, the system determines the automatically called lower chute temperature setting value according to the actual thickness value of the online strip. The specific calling method is to look up Table 1, that is, according to the online strip thickness, automatically query the thickness-temperature comparison table already entered in the system database, and select the lower chute temperature value corresponding to the current online strip thickness in the table as the setting value.

[0055] S2, Strip stability control in post-cooling section

[0056] In order to avoid uneven zinc layer defects caused by the shaking of the strip in the post-cooling section due to the air flow of the air knife, cooling fan, etc., an electromagnetic sensor is added in the post-cooling section. The electromagnetic sensor is installed in six boxes evenly distributed on the upper and lower surfaces of the electromagnetic correction device. The electromagnetic sensor is used to detect the edge-middle-edge distance of the strip, and the upper and lower surfaces of the corresponding chute area under the annealing furnace are linked to control the magnetic output values ​​of a total of six electromagnets, so as to achieve the magnetic adsorption torque to ensure that the strip is always in a state of slight shaking or no shaking; the display and operation interface of the electromagnetic stabilization system is set on the main line operation screen, and the database of the electromagnetic stabilization system of the strip in the post-cooling section of the galvanizing line is assigned to realize the function of automatic control according to the strip (that is, according to the edge-middle-edge distance of the strip detected by the electromagnetic detection device The system measures the distance from the sensor according to the requirements of the magnetic strength output mode for different strip thicknesses and the setting values ​​of the strip deflection distance range. The system measures the distance from the edge-middle-edge distance sensor of the strip detected by the electromagnetic detection device, and compares the strip thickness with the setting values ​​of the deflection distance range of each position according to the strip thickness specified in Table 2. By dynamically adjusting the magnetic output value (magnetic strength mode) of the electromagnets installed at different positions, the magnetic adsorption torque generated on various parts of the strip is balanced. At this time, the resultant torques of the strip in the running direction (longitudinal) and the width direction (transverse) are both in a balanced state, the strip will remain stable and will not shake, reducing the uneven coating defects caused by the strip shaking. The specific data table is shown in Table 2.

[0057] Table 2 shows the parameter settings of the strip stabilization system.

[0058]

[0059] S3, zinc pot deslagging

[0060] Taking advantage of the fact that the solubility of Fe element in aluminum-zinc solution changes with temperature and has the irreversibility of not being able to dissolve again after precipitation, a program is set in the zinc pot temperature detection and control system, and the plating solution temperature is raised and lowered by reciprocating 4-6 times (each Step from Step 1 to Step 6 in the following table is defined as 1 time) during the production interval to promote the precipitation of Fe element in the form of zinc slag, and the precipitated zinc slag is fished out to reduce the amount of zinc slag defects during production. The specific plan is as follows:

[0061] While utilizing the existing zinc pot detection thermocouple and PLC / DCS control device, a temperature curve is added, a database is established in the temperature control unit, and the temperature control curve is compiled, see Table 3, to realize the cyclic heating and cooling function; at the end of each production interval, the zinc pot temperature control system is started, and the Fe element is precipitated in the form of zinc slag through temperature change, and the precipitated zinc slag is scooped out using a slag scooping tool during the rotary pot production preparation period.

[0062] Table 3 is the zinc pot temperature control curve.

[0063]

[0064]

[0065] Table 3 shows the steps of the whole process of zinc pot deslagging operation. The execution of step 1 to step 6 is a complete deslagging operation process, in which each step is executed according to the zinc pot set temperature and insulation time specified in the table.

[0066] S4. Intelligent equipment and method for polishing liquid concentration of polishing machine:

[0067] Stable control of the concentration of finishing liquid is very beneficial for controlling finishing color difference defects. However, due to the influence of the high-pressure cleaning device of the finishing machine constantly adding new water to the finishing liquid circulation system, the concentration of the finishing liquid is always in a downward trend. Therefore, by upgrading the online conductivity device of the finishing liquid, stable and intelligent control of the finishing liquid concentration can be achieved. Because the finishing liquid is used in the room temperature environment, when calculating the corresponding relationship between the online conductivity of the finishing liquid and the actual concentration, it is only necessary to measure the corresponding relationship between the finishing liquid concentration and conductivity at room temperature (25°C). The relationship between the finishing liquid concentration and conductivity can be obtained as follows:

[0068] Y=-20.63X 2 +315.5X+8.405 ①

[0069] In formula ①, Y represents the conductivity of the finishing solution, the unit is us / cm, and X represents the concentration of the finishing solution, the unit is %;

[0070] Formula ① is used as the core calculation formula for controlling the concentration of the finishing liquid and is written into the program. The real-time data detected by the online conductivity detection device installed in the finishing circulation box is used to determine whether the concentration of the finishing liquid is within the set value range, and the start and stop and operating time of the finishing liquid proportioning pump are controlled in conjunction to achieve real-time intelligent and precise control of the finishing liquid concentration.

[0071] Table 4 is an example of production practice using the specific method described in this patent. Each group of items is the specific key parameter value in the production process at that time.

[0072] project 1 2 3 4 5 Strip steel specifications, mm 0.45*1000 0.65*1150 1.08*1260 1.35*1250 1.85*1180 Lower chute temperature, ℃ 600 595 593 590 586 Stabilizer Magnetic Mode LOW LOW MEDIUM MEDIUM HIGH OS side deflection setting value, mm ±2.0 ±2.5 ±3.0 ±4.0 ±4.5 Intermediate deflection setting value, mm ±1.0 ±1.5 ±2.0 ±3.0 ±4.0 DS side deflection setting value, mm ±2.0 ±2.5 ±3.0 ±4.0 ±4.5 Conductivity setting value of finishing liquid, us / cm 220 250 260 310 330 Zinc slag, zinc ash, finishing color difference, scrap rate, % 0 0 0 0 0

[0073] The present invention achieves the goal of reducing the probability of problems that seriously affect the surface quality of high-level hot-dip galvanized products, such as uneven zinc spangles, zinc slag, zinc ash, and color difference in finishing, without significantly increasing equipment investment, by optimizing the precise control equipment and process parameter scheme of the lower chute temperature of the galvanizing unit, by controlling the equipment and process scheme of the stability of the strip in the post-cooling section, and by modifying the zinc pot slag removal equipment and method, thereby achieving high-quality and efficient production of high-level hot-dip galvanized products and ensuring stable operation of the unit and compliance of product quality with requirements, through the premise of not substantially increasing equipment investment.

Claims

1. A hot-dip production method for high-grade surface aluminum-zinc coated steel sheet, characterized in that: include: S1. The lower chute of the annealing furnace is equipped with a heating device and a temperature detection device. The temperature setting value of the lower chute of the annealing furnace is called as the control value according to the thickness of the strip steel, and the power of the heating device is adjusted according to the actual value of the temperature detection device to make the temperature of the lower chute of the annealing furnace constant; S2. Add an electromagnetic detection device in the post-cooling section to detect the edge-middle-edge distance of the strip, control the magnetic output value of the upper and lower surface electromagnets of the corresponding area of ​​the lower chute of the annealing furnace, and keep the strip in a non-shaking state according to the magnetic adsorption torque; If 0.35≤t<0.50, I=120*t+10, the deflection distance range setting value of the strip steel on the OS side is ±2.0, the deflection distance range setting value of the middle strip steel is ±1.0, and the deflection distance range setting value of the strip steel on the DS side is ±2.0; If 0.50≤t<0.80, I=120*t+20, the deflection distance range setting value of the strip steel on the OS side is ±2.5, the deflection distance range setting value of the middle strip steel is ±1.5, and the deflection distance range setting value of the strip steel on the DS side is ±2.5; If 0.80≤t<1.10, I=100*t+40, the deflection distance range setting value of the strip steel on the OS side is ±3.0, the deflection distance range setting value of the middle strip steel is ±2.0, and the deflection distance range setting value of the strip steel on the DS side is ±3.0; If 1.10≤t<1.5, I=100*t+50, the deflection distance range setting value of the strip steel on the OS side is ±4.0, the deflection distance range setting value of the middle strip steel is ±3.0, and the deflection distance range setting value of the strip steel on the DS side is ±4.0; If 1.50≤t<2.00, I=90*t+50, the deflection distance range setting value of the strip steel on the OS side is ±4.5, the deflection distance range setting value of the middle strip steel is ±4.0, and the deflection distance range setting value of the strip steel on the DS side is ±4.5; If 2.00≤t<2.50, I=90*t+60, the deflection distance range setting value of the strip steel on the OS side is ±5.0, the deflection distance range setting value of the middle strip steel is ±5.0, and the deflection distance range setting value of the strip steel on the DS side is ±5.0; t represents the strip thickness in mm, I represents the output current value of the electromagnet magnetic force control in A; S3, according to the solubility of Fe element in aluminum-zinc solution changes with temperature, and has irreversible property that it cannot be dissolved again after precipitation, the plating solution temperature is raised and lowered by reciprocating cycle 4-6 times during the production interval, so as to promote the precipitation of Fe element in the form of zinc slag, and the precipitated zinc slag is fished out; Step 1: The target temperature of the zinc pot is set to 610℃, the allowable fluctuation range of the temperature setting value is ±5℃, and the holding time is 4h; Step 2: The target temperature of the zinc pot is set to 600°C, the allowable fluctuation range of the temperature setting value is ±3°C, and the holding time is 3h; Step 3: The target temperature of the zinc pot is set to 590°C, the allowable fluctuation range of the temperature setting value is ±2°C, and the holding time is 3h; Step 4: The target temperature of the zinc pot is set to 610°C, the allowable fluctuation range of the temperature setting value is ±5°C, and the holding time is 5h; Step 5: The target temperature setting value of the zinc pot is 590℃, the allowable fluctuation range of the temperature setting value is ±3℃, and the holding time is 5h; Step 6: The target temperature setting value of the zinc pot is 580℃, the allowable fluctuation range of the temperature setting value is ±2℃, and the holding time is 5h; S4. Determine the concentration of the finishing liquid by an online conductivity detection device.

2. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: In S1, the strip thickness calls the annealing furnace lower chute temperature setting value, which is based on the online strip thickness, queries the thickness-temperature data already entered in the system database, and selects the lower chute temperature data corresponding to the current online strip thickness as the annealing furnace lower chute temperature setting value; The power of the heating device is adjusted according to the actual value of the temperature detection device, that is, the temperature detection device compares the actual temperature value detected with the temperature setting value. When the difference between the actual temperature value detected and the temperature setting value exceeds -5°C, the heating device increases the power output value. When the difference between the actual temperature value detected and the temperature setting value exceeds +5°C, the heating device reduces the power output value.

3. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: In S2, the distance between the edge of the strip and the center of the strip is such that the center of the strip coincides with the center line in the width direction of the strip, and the edge of the strip is a distance set from the center line to both sides along the width direction of the strip; The magnitude of the magnetic adsorption torque is proportional to the magnetic output value. By adjusting the magnetic output value of the electromagnet, the magnetic adsorption torque generated on various parts of the strip can be balanced. At this time, the combined torque of the torque applied to the strip in the running direction (longitudinal) and the width direction (transverse) are both in a balanced state, and the strip will remain stable without shaking.

4. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: In S1, the heating device is a plurality of groups of resistance heating belts, which are evenly distributed on the inner arms of the upper and lower surfaces of the lower chute of the annealing furnace, and centralized heating is adopted; the temperature detection device is a thermocouple, which is arranged on the transmission side of the unit on the upper and lower surfaces of the lower chute of the annealing furnace.

5. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 4, characterized in that: The power range of each group of resistance heating belts is 600-800kw.

6. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: In S1, the lower chute of the annealing furnace is a passage connecting the outlet of the annealing furnace and the zinc pot, and the strip steel passes through the lower chute of the annealing furnace.

7. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: In S4, the correspondence between the online conductivity of the finishing liquid and the actual finishing liquid concentration is calculated. It is only necessary to measure the correspondence between the finishing liquid concentration and the conductivity at room temperature (25°C). The relationship between the finishing liquid concentration and the conductivity is as follows: <h2 style=";text-align:left;direction:ltr">Y = -20.63X<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +315.5X+8.405 1 In formula ①, Y represents the conductivity of the finishing solution, the unit is us / cm, and X represents the concentration of the finishing solution, the unit is %; The real-time data detected by the online conductivity detection device is used to determine whether the concentration of the finishing liquid is within the set value range, and to control the start and stop and operating time of the finishing liquid proportioning pump.

8. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 7, characterized in that: In S4, the conductivity detection device is arranged in the light-smoothing circulation box.

9. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: The chemical composition of the substrate is calculated by mass percentage as follows: C 0.001% to 0.80%, Si 0.001% to 2.2%, Mn 0.06% to 10.50%, P ≤ 0.04%, S ≤ 0.04%, Al 0.02% to 3.00%, Ti ≤ 0.20%, B ≤ 0.005%, Cr 0.03% to 0.70%; Mo 0.01%~1.60%, Cu ≤0.70%, Ni 0.15%~1.2%, Nb ≤0.08%; the rest are Fe and unavoidable impurities.

10. The hot-dip production method of high-grade aluminum-zinc coated steel sheet according to claim 1, characterized in that: The chemical composition of the aluminum-zinc coating is calculated by mass percentage as follows: Al 55%-65%, Si 1.2%-15%, Ti 0.03%-0.50%, Re 0.01%-0.20%, Li 0.05%-3%, Cu 0.1%-5.0%, Fe 0.03%-1.0%, Mn 0.5%-3.0%, Ni 0.5%-4.0%, V 0.01%-0.5%, Zr 0.5%-1.0%, Cr 0.1%-1.0%; the rest is Zn and unavoidable impurities.

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