A control method for reducing the amount of zinc residue produced by a zinc-aluminum-magnesium unit

Abstract

The present application belongs to the technical field of cold-rolled steel coating, and specifically discloses a control method for reducing the amount of zinc residue produced by a zinc-aluminum-magnesium unit, which controls the residue reduction from four aspects. First, the degreasing cleaning before the strip steel enters the pot is optimized, and the whole process parameters of alkaline washing, electrolysis and rinsing are limited. Second, the working condition of the zinc pot is stabilized, the zinc ingot pretreatment and automatic zinc adding operation are standardized, the zinc liquid temperature and liquid level are strictly controlled, and the plate temperature entering the pot is matched according to the thickness of the strip steel. Third, the protective atmosphere of the annealing furnace and the furnace nose is optimized, the oxygen content and dew point of each zone are strictly controlled, the furnace is fully washed and replaced before starting, and the zinc residue pump is adjusted to inhibit the oxidation of the zinc liquid. Fourth, the frequency and path of the rake residue and the residue are standardized. In view of the high residue production ratio and the zinc residue defect on the plate surface in the existing zinc-aluminum-magnesium hot-dip production, the present application can reduce the residue production ratio of the unit, reduce the occurrence rate of zinc residue defects of the strip steel, and reduce the consumption of zinc ingots.

Description

Technical Field

[0001] This invention relates to the field of coating technology for cold-rolled steel, and specifically to a method for controlling the amount of zinc slag generated in zinc-aluminum-magnesium units. Background Technology

[0002] Zinc-aluminum-magnesium coatings offer excellent corrosion resistance and are widely used in photovoltaics, construction, and home appliances. However, during continuous hot-dip galvanizing, the molten zinc reacts with the steel strip, equipment, and environmental media, easily generating zinc ash (dross) and bottom dross. This not only increases zinc ingot consumption and production costs but also causes defects such as zinc scars and dross on the steel strip surface, affecting product quality.

[0003] Factors contributing to zinc dross generation during production include: insufficient cleanliness of the strip steel before it enters the furnace, large fluctuations in the temperature and composition of the zinc bath, inadequate control of the furnace nose atmosphere, and non-standard dross removal and zinc addition operations. These factors result in a high dross production ratio, approximately 9% for photovoltaic products, with double-sided coatings ≤40g / m². 2 The slag production ratio of thin-gauge products is about 15%, and the zinc slag defect rate is 1.57%, which makes it difficult to meet the requirements of high efficiency, low consumption and production quality assurance.

[0004] In the existing technology, the literature entitled "Mechanism and Control Measures for Zinc Dross Generation on Steel Strip Surface" studies and analyzes the mechanism of zinc dross generation and introduces a method to solve the zinc dross defect on the surface of galvanized steel sheets. However, it does not clearly address the control of zinc addition and dross removal operations in the process control requirements for reducing zinc dross generation in zinc-aluminum-magnesium units. Therefore, there is an urgent need for a control method to reduce zinc dross generation by optimizing the entire process from raw material cleaning, process control, equipment operation and maintenance, and operation specifications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for controlling the amount of zinc slag produced by zinc-aluminum-magnesium power plants, so as to solve the problems of large amount of zinc slag produced and high slag production ratio in existing zinc-aluminum-magnesium power plants.

[0006] To achieve the above objectives, the basic solution provided by this invention is: a control method for reducing the amount of zinc slag generated in a zinc-aluminum-magnesium unit, including improving the cleanliness of the strip steel before it enters the boiler, controlling the temperature of the zinc bath and the zinc addition, optimizing the atmosphere of the annealing furnace and the furnace nose, and standardizing the slag removal operation. The method for improving the cleanliness of the strip steel before it enters the boiler is as follows: alkaline spraying, brushing, and electrolytic degreasing processes. The spraying pressure is ≥0.3MPa, the brush rotation speed is ≥300r / min, and the electrolytic current density is 10~15A / dm³. 2The hot water washing and rinsing process uses demineralized water at a temperature of 65±5℃, with a washing time of ≥15s. After rinsing, the water film on the strip surface remains continuous without breakage. The zinc liquid temperature and zinc addition control are achieved by purging the zinc ingots with compressed air and wiping them clean with cotton cloth before they are put into the pot. The zinc ingots are automatically controlled by the zinc addition hoist, with a descent speed ≤0.5m / s, a zinc pot liquid level fluctuation ≤2mm, and a zinc liquid temperature set at 430℃, with a control range of 430±3℃. The furnace nose atmosphere is optimized by maintaining the zinc slag pump opening at 40%~60%, adjusting it to 60% when the slag coverage on the liquid surface is >1 / 3, setting the electric heating temperature at 460±10℃, and keeping the furnace nose dew point <-20℃, while monitoring the sealing status in real time.

[0007] The beneficial effects of this invention are as follows: by limiting the degreasing and cleaning process parameters, oil stains, impurities and oxide layers on the surface of the strip steel are removed, eliminating the problem of zinc liquid reaction and slag formation induced by substrate impurities. At the same time, by stabilizing the zinc liquid temperature, liquid level and zinc addition conditions, the dew point and sealing status of the furnace nose are strictly controlled, inhibiting zinc ash and bottom slag generated by zinc liquid oxidation and abnormal alloy reaction.

[0008] Option 2, which is the preferred option of the basic option, has an alkaline point of 24±2, an electrical conductivity of 70~80ms / cm, and a temperature of 45±5℃ in the alkaline spraying, brushing and electrolytic degreasing processes.

[0009] Option 3, which is the preferred option of the basic option, involves monitoring and recording the temperature of the zinc liquid every 30 minutes. The temperature of the strip entering the pot is adjusted according to its thickness. The adjustment method is as follows: when the thickness is ≤1.5mm, the plate temperature is 430~440℃; when the thickness is >1.5mm, the plate temperature is 420~430℃.

[0010] Option 4 is the preferred option of the basic option. The annealing furnace atmosphere is optimized as follows: oxygen content in RTF, JCF, LTH, and TDS sections is <20ppm, dew point is <-20℃, furnace is cleaned and replaced 8 hours before start-up, and the temperature can be increased only after the oxygen content meets the standard.

[0011] Option 5, which is the preferred option of the basic option, is to standardize the control of slag removal operations as follows: once per hour, slag removal is carried out along the path from the stabilizing roller, the zinc-adding area, and the top of the submerged roller to the zinc-adding area, with a stirring depth not exceeding 10cm; once every 4 hours, slag removal is carried out only in the zinc-adding area, with a slag removal spoon capacity ≤5L. Detailed Implementation

[0012] The present invention will be further described in detail below through specific embodiments: Example 1

[0013] A method for reducing zinc slag production in zinc-aluminum-magnesium (ZAM) annealing units includes improving the cleanliness of the strip steel before it enters the boiler, controlling the temperature and zinc addition of the zinc bath, optimizing the atmosphere of the annealing furnace and furnace nose, and standardizing the slag removal operation. The method for improving the cleanliness of the strip steel before entering the boiler involves alkaline spraying, brushing, and electrolytic degreasing processes. The spraying pressure is ≥0.3 MPa, the brush rotation speed is ≥300 r / min, the alkaline point of the alkaline spraying, brushing, and electrolytic degreasing processes is 24±2, the conductivity is 70~80 mS / cm, the temperature is 45±5℃, and the electrolytic current density is 10~15 A / dm³. 2 The hot water washing and rinsing processes use demineralized water at a temperature of 65±5℃, with a washing time of ≥15s. After rinsing, the water film on the strip surface remains continuous and unbroken. Simultaneously, the magnetic filter is classified as Class A equipment, ensuring 100% utilization and cleaning once a week. The sludge bucket is emptied during shift handover and inspected twice daily. The nozzles in the cleaning section are unclogged monthly to ensure 100% spray coverage. The zinc bath temperature and zinc addition control methods are as follows: before the zinc ingots are put into the pot, they are blown clean with compressed air and wiped clean with cotton cloth to remove surface dust and oil. It is strictly forbidden to put damp zinc ingots into the pot. The zinc ingots are automatically controlled by the zinc addition hoist, with a descent speed ≤0.5m / s and a zinc pot liquid level fluctuation ≤2mm. The zinc bath temperature is set at 430℃, with a control range of 430±3℃. The zinc bath temperature is monitored and recorded every 30 minutes. The strip steel plate temperature is adjusted according to the thickness. The adjustment method is as follows: when the thickness is ≤1.5mm, the plate temperature is 430~440℃; when the thickness is >1.5mm, the plate temperature is 420~430℃. The furnace nose atmosphere optimization method is to maintain the zinc slag pump opening at 40% to 60%, adjust it to 60% when the slag coverage on the liquid surface is >1 / 3, set the electric heating temperature to 460±10℃, keep the furnace nose dew point <-20℃, and monitor the sealing status in real time. The annealing furnace atmosphere optimization method is to keep the oxygen content in the RTF, JCF, LTH, and TDS sections <20ppm, keep the dew point <-20℃, clean and replace the furnace 8 hours before starting, and only raise the temperature after the oxygen content meets the standard. The standardized control method for slag removal operation is as follows: once per hour, slag removal operation is carried out along the path from the stabilizing roller, zinc addition zone, and above the submerged roller to the zinc addition zone, with a stirring depth not exceeding 10cm; once every 4 hours, slag removal operation is carried out only in the zinc addition zone, with a slag removal spoon capacity ≤5L.

[0014] Example 2

[0015] A method for controlling the amount of zinc slag generated in a zinc-aluminum-magnesium unit, wherein the electrical conductivity of the cleaning section is 72 mS / cm and the temperature is 44℃; the zinc liquid temperature is 430℃; the oxygen content at the furnace nose is 15 ppm and the dew point is -28℃; the zinc slag pump opening is 50%; and slag is raked and removed according to standard procedures.

[0016] Results: The slag production ratio was 5.2%, zinc ash bottom slag was separated and collected, and the defect rate of zinc slag in the product was 0.27%.

[0017] Example 3 (double-sided coating ≤40g / m) 2 product) A method for controlling the amount of zinc slag generated in a zinc-aluminum-magnesium unit, wherein the strip thickness is 0.3 mm, the temperature of the plate entering the boiler is 435℃, the temperature of the zinc liquid is 431℃, the zinc slag pump opening is 55%, and the cleaning and slag removal specifications are strictly implemented.

[0018] Results: The slag production ratio was 10.3%, and the zinc slag defect rate was 0.36%.

[0019] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for controlling the generation of zinc slag in zinc-aluminum-magnesium power plants, characterized in that, This includes improving the cleanliness of the strip steel before it enters the furnace, controlling the temperature and zinc addition of the zinc bath, optimizing the atmosphere of the annealing furnace and furnace nose, and standardizing the slag removal operation. The methods for improving the cleanliness of the strip steel before it enters the furnace are alkaline spraying, brushing, and electrolytic degreasing processes. The spraying pressure is ≥0.3MPa, the brush speed is ≥300r / min, and the electrolytic current density is 10~15A / dm³. 2 The hot water washing and rinsing process uses desalinated water at a temperature of 65±5℃ and a washing time of ≥15s. After rinsing, the water film on the strip surface is continuous and unbroken. The zinc liquid temperature and zinc addition control methods are as follows: before the zinc ingots are put into the pot, they are purged with compressed air and wiped clean with cotton cloth. The zinc ingots are automatically controlled by the zinc addition hoist, with a descent speed ≤0.5m / s, zinc pot liquid level fluctuation ≤2mm, zinc liquid temperature set at 430℃, and control range 430±3℃. The furnace nose atmosphere is optimized by maintaining the zinc slag pump opening at 40%~60%, adjusting it to 60% when the slag coverage on the liquid surface is >1 / 3, electric heating temperature at 460±10℃, furnace nose dew point <-20℃, and real-time monitoring of sealing status.

2. The method for controlling the generation of zinc slag in a zinc-aluminum-magnesium unit according to claim 1, characterized in that, The alkaline point of the alkaline spraying, brushing and electrolytic degreasing processes is 24±2, the electrical conductivity is 70~80ms / cm, and the temperature is 45±5℃.

3. The method for controlling the generation of zinc slag in a zinc-aluminum-magnesium unit according to claim 1, characterized in that, The temperature of the zinc bath is monitored and recorded every 30 minutes. The temperature of the strip steel entering the pot is adjusted according to its thickness. The adjustment method is as follows: when the thickness is ≤1.5mm, the plate temperature is 430~440℃; when the thickness is >1.5mm, the plate temperature is 420~430℃.

4. The method for controlling the generation of zinc slag in a zinc-aluminum-magnesium unit according to claim 1, characterized in that, The annealing furnace atmosphere optimization method is as follows: oxygen content in RTF, JCF, LTH, and TDS sections <20ppm, dew point <-20℃, furnace cleaning and replacement 8 hours before start-up, and heating can only be carried out after the oxygen content meets the standard.

5. The method for controlling the generation of zinc slag in a zinc-aluminum-magnesium unit according to claim 1, characterized in that, The standardized control method for slag removal operation is as follows: once per hour, slag removal operation is carried out along the path from the stabilizing roller, zinc addition zone, and above the submerged roller to the zinc addition zone, with a stirring depth not exceeding 10cm; once every 4 hours, slag removal operation is carried out only in the zinc addition zone, with a slag removal spoon capacity ≤5L.