CN111270297A - Method for reducing zinc or zinc particle defects of hot-dip galvanized sheet surface strip - Google Patents
Method for reducing zinc or zinc particle defects of hot-dip galvanized sheet surface strip Download PDFInfo
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- CN111270297A CN111270297A CN202010161992.1A CN202010161992A CN111270297A CN 111270297 A CN111270297 A CN 111270297A CN 202010161992 A CN202010161992 A CN 202010161992A CN 111270297 A CN111270297 A CN 111270297A
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
- C25F1/02—Pickling; Descaling
- C25F1/04—Pickling; Descaling in solution
- C25F1/06—Iron or steel
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B45/00—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills
- B21B45/02—Devices for surface or other treatment of work, specially combined with or arranged in, or specially adapted for use in connection with, metal-rolling mills for lubricating, cooling, or cleaning
- B21B45/0269—Cleaning
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
- C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/04—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the coating material
- C23C2/06—Zinc or cadmium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
- C23C2/34—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor characterised by the shape of the material to be treated
- C23C2/36—Elongated material
- C23C2/40—Plates; Strips
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Abstract
The invention belongs to the field of hot-dip galvanized plate preparation, and particularly relates to a method for reducing the defects of zinc or zinc particles on the surface of a hot-dip galvanized plate. Aiming at the problems of serious zinc or zinc particle defects of the surface strip of the hot-dip galvanized sheet and poor steel quality, the invention provides a method for reducing the zinc or zinc particle defects of the surface strip of the hot-dip galvanized sheet, which comprises the following steps: a. the rolling cleanliness of the strip steel; b. when the strip steel is degreased and cleaned, controlling the temperature and the alkalinity of alkali liquor, the electrolytic current of an electrolytic bath and the free alkalinity of a cleaning bath during the degreasing and cleaning of the strip steel; c. controlling hydrogen in the furnace during continuous annealing; d. when in hot dipping, controlling the Al content in the plating solution, the temperature of the strip steel in a zinc pot and the temperature of the plating solution; a step-by-step zinc adding method or automatic zinc adding is adopted; e. the slag is removed in time and fished out from the side of the strip steel to the edge part, thus avoiding the fluctuation of the plating solution. Through the operation, the defects of strip zinc or zinc particles in the hot-dip galvanized sheet are reduced, the surface quality of the product is improved, the FC group yield is improved, the degradation rate is improved, the economic benefit is obvious, and the application prospect is wide.
Description
Technical Field
The invention belongs to the field of hot-dip galvanized plate preparation, and particularly relates to a method for reducing the defects of zinc or zinc particles on the surface of a hot-dip galvanized plate.
Background
Hot dip galvanized steel sheets (GI, GA) have excellent corrosion resistance, formability, paintability, weldability and other quality characteristics, and thus are widely used in the industries of buildings, automobiles, home appliances, and the like. With the improvement of hot dip coating technology and the improvement of the quality of hot dip coating products, the hot dip coating technology has gradually replaced Electrogalvanizing (EG) in the household electrical appliance and automobile industries. In recent years, with the rapid development of domestic household appliances and automobile manufacturing industries, the demand of hot-dip galvanized steel sheets is rapidly increased, resulting in explosive construction of hot-dip galvanizing units and rapid improvement of hot-dip galvanizing productivity. At present, the domestic hot galvanizing capacity is seriously surplus, the market competition of users in the building industry tends to be disordered, the market competition of users in the household appliance industry tends to be white, and the market competition of users in the automobile industry also tends to be intense day by day. In order to capture a certain share in the fierce market competition, various hot-galvanized plate manufacturers take great time on the quality of products, and the zinc particle/strip defects are the key points to be treated. Aiming at the zinc particle/strip zinc defect, the Bao steel is respectively provided with 1 zinc liquid pump at two sides of the furnace nose, and zinc ash and zinc slag on zinc liquid surfaces at two sides in the furnace nose are pumped out of the furnace nose and fished out, so that the zinc ash and the zinc slag are prevented from being adhered to the surface of the strip steel to influence the surface quality of the strip steel; the first steel adopts a bi-component cleaning process, the components of the cleaning fluid are added together from the liquid of single components (alkali, surfactant, defoaming agent and the like) commonly used in China at present, and are changed into the components of the alkali, the surfactant, the defoaming agent and the like which are respectively and independently added according to the process requirements, the cleanliness of the surface of the strip steel is improved, and the defect of strip zinc or zinc particles is further reduced.
The functions of the unit equipment such as steel-climbing galvanizing and the like are gradually aged, and the problems of zinc particles/zinc strips on the surface and the like are more, so that the surface quality of the hot-dip galvanized plate is seriously influenced. The invention aims to reduce the defects of zinc or zinc particles on the surface of the hot-dip galvanized sheet and improve the quality of the hot-dip galvanized sheet by process improvement under the condition of the existing equipment.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the surface of the hot galvanized sheet has serious defects of zinc or zinc grains and poor quality of the steel sheet.
The technical scheme for solving the technical problems comprises the following steps: provides a method for reducing the defects of zinc or zinc particles on the surface of hot-dip galvanized sheet. The method comprises the following steps:
a. after rolling the strip steel, controlling the cleanliness to ensure that the content of the miscellaneous oil in the emulsion is 6-15%;
b. when the strip steel is degreased and cleaned, controlling the temperature of alkali liquor in an alkali liquor tank to be 40-90 ℃, the alkalinity of the alkali liquor to be 30-90 Pt., the electrolytic current of the electrolytic tank to be 6000-10000A, and the free alkalinity of a cleaning tank to be lower than 15 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 2.0 percent;
d. when hot dipping, controlling the Al content in the plating solution to be 0.15-0.25%, the temperature of strip steel entering a zinc pot to be 440-480 ℃, and the temperature of the plating solution to be 455-475 ℃; a step-by-step zinc adding method or automatic zinc adding is adopted, and zinc ingots are added for multiple times;
e. the slag is removed in time and fished out from the side of the strip steel to the edge part, thus avoiding the fluctuation of the plating solution.
In the method for reducing the zinc or zinc particle defects on the surface of the hot-dip galvanized sheet, the emulsion miscellaneous oil in the step a is at least one of rolling mill oil mist or Morgan, gears and engine oil generated by a main hydraulic system and an auxiliary hydraulic system mixed in the emulsion.
In the method for reducing the zinc or zinc particle defects on the surface of the hot-dip galvanized sheet, the strip steel in the step b is dried at the temperature of more than or equal to 90 ℃ after being degreased and cleaned.
In the method for reducing the zinc or zinc particle defects of the hot-dip galvanized sheet surface strip, the absolute value of the temperature difference between the strip steel entering a zinc pot temperature and the plating solution temperature is controlled to be less than or equal to 5 in the step d.
In the method for reducing the defects of zinc or zinc particles on the surface of the hot-dip galvanized sheet, the step d is repeated for 3 to 5 times.
Wherein, in the method for reducing the defects of zinc or zinc particles on the surface of the hot-dip galvanized sheet, the specific operation method for gradually adding zinc in the step d comprises the following steps: adding 200kg of zinc, marking the zinc liquid as a liquid level 1 after the liquid level of the zinc is determined, and calculating the liquid level height 2 of 1/5-1/3 reduced zinc liquid by 200kg according to the size of a zinc pot and the density of plating liquid; when the plating solution drops to the liquid level 2, adding a zinc ingot to the liquid level height 1.
In the method for reducing the zinc or zinc particle defects of the hot-dip galvanized sheet surface strip, the timely slag skimming and slag salvaging in the step e is carried out once every 0.5-2 hours.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, through controlling the surface cleanliness of the rolled strip steel, degreasing and cleaning, annealing atmosphere, hot dipping process, zinc adding mode, slag skimming and slag fishing mode and other processes, under the combined action, the defects of strip zinc or zinc particles in the hot-dip galvanized plate are reduced, the surface quality of the product is improved, the FC group yield is improved, the degradation rate of change and the spot rate are greatly reduced, and the rate of change is reduced from more than 2% to less than 0.6%. The method greatly reduces the defects of zinc bars or zinc particles under the condition of the existing equipment, and has the advantages of simple operation, low cost, obvious economic benefit and wide application prospect.
Drawings
FIG. 1 is a photograph showing the surface macro-topography of a hot-dip galvanized sheet prepared in example 1;
FIG. 2 is a photograph showing the macro-morphology of the surface of the hot-dip galvanized sheet prepared in comparative example 1;
fig. 3 is a photograph showing the macro topography of the surface of the hot-dip galvanized sheet prepared in comparative example 2.
Detailed Description
The zinc bar means: the hot dip galvanized steel sheet is strip-shaped along the rolling direction, is indefinite in position, is about 1-10 mm long and about 1-2 mm wide, and is mainly distributed on the surface of a hot dip galvanized steel sheet with the thickness of 0.4-1.5 mm; the zinc particles are dense and fine zinc particles on the whole plate surface, can be seen by naked eyes, have hand feeling, have the diameter of about 0.3-1 mm, and are mainly distributed on the surface of the hot-dip galvanized plate with the plate thickness of more than 1.5 mm.
In hot-dip galvanized sheet produced by the existing steel production process, about two percent or more of steel sheets have the defects of zinc bars or zinc particles.
The invention provides a method for reducing the defects of zinc or zinc particles on the surface of hot-dip galvanized sheet, which comprises the following steps:
a. after rolling the strip steel, controlling the cleanliness to ensure that the content of the miscellaneous oil in the emulsion is 6-15%;
b. when the strip steel is degreased and cleaned, controlling the temperature of alkali liquor in an alkali liquor tank to be 40-90 ℃, the alkalinity of the alkali liquor to be 30-90 Pt., the electrolytic current of the electrolytic tank to be 6000-10000A, and the free alkalinity of a cleaning tank to be lower than 15 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 2.0 percent;
d. when hot dipping, controlling the Al content in the plating solution to be 0.15-0.25%, the temperature of strip steel entering a zinc pot to be 440-480 ℃, and the temperature of the plating solution to be 455-475 ℃; a step-by-step zinc adding method or automatic zinc adding is adopted, and zinc ingots are added for multiple times;
e. the slag is removed in time and fished out from the side of the strip steel to the edge part, thus avoiding the fluctuation of the plating solution.
In the method for reducing the zinc or zinc particle defects on the surface of the hot-dip galvanized sheet, the emulsion miscellaneous oil in the step a is at least one of rolling mill oil mist or Morgan, gears and engine oil generated by a main hydraulic system and an auxiliary hydraulic system mixed in the emulsion. The lower the content of the miscellaneous oil is, the higher the content of the effective oil in the emulsion is, the lubrication effect is improved, and impurities such as residual iron and the like are reduced; in addition, the miscellaneous oil is easier to remain on the surface of the strip steel, and the reduction of the miscellaneous oil is beneficial to reducing the residual oil quantity of the strip steel after rolling, so the lower the miscellaneous oil is, the better the miscellaneous oil is; but the miscellaneous oil can not be completely eliminated, the lower the miscellaneous oil is, the greater the control difficulty is, the higher the cost is, and the invention is best when the content of the miscellaneous oil in the emulsion is controlled to be 6-15% through multiple tests verification on the premise of comprehensively considering the cost and the galvanizing quality.
In addition, the temperature and the concentration of the alkali liquor in the alkali liquor tank are controlled during degreasing and cleaning of the strip steel, the higher the temperature and the concentration of the alkali liquor in the alkali liquor tank are, the higher the activity of the alkali liquor is, the easier the impurities on the surface of the strip steel are removed, but after the concentration of the alkali liquor reaches a certain concentration, the cleaning capability is not improved any more, and the cleaning difficulty is increased instead. Experiments prove that the cleaning effect is best when the temperature of the alkali liquor in the alkali liquor tank is 40-90 ℃ and the alkalinity of the alkali liquor is 30-90 Pt..
The electrolytic bath removes residues on the surface of the steel plate by electrolysis, and the cleaning capacity is higher as the current is higher. The invention controls the electrolytic current of the electrolytic cell to be 6000-10000A, and the range is determined by combining the cleaning capability and the unit capability. The cleaning tank is used for cleaning alkali liquor remained on the surface of the steel plate, the lower the free alkalinity is, the better the free alkalinity is, and the invention can ensure that the cleanliness of the steel plate can meet the requirement of hot dip coating by controlling the free alkalinity of the cleaning tank to be lower than 15 Pt..
In order to prevent the surface of the strip steel from being oxidized, the hydrogen in the furnace is controlled to be more than or equal to 2.0 percent during continuous annealing.
The plating solution has low Al content, which easily produces bottom slag which is not easy to be removed, and has high Al content, which easily produces more floating slag, influences the thickness of the intermediate alloy layer, and is not beneficial to controlling the surface quality. In order to ensure that bottom slag is not generated in the zinc liquid, the generation amount of the zinc slag is reduced, and the thickness of the intermediate alloy layer is ensured, the Al content in the plating liquid is 0.15-0.25% in the plating liquid; the temperature of the plating solution is determined to be 455-475 ℃ by combining with the texture change of the plating layer forming process, and the temperature difference between the temperature of the strip steel entering the zinc pot and the temperature of the plating solution is controlled to be less than or equal to 5 ℃ in order to control the quality. The absolute value of the temperature difference is controlled to be less than or equal to 5, so that the stability of the temperature of the plating solution and the steel plate can be ensured, and the temperature fluctuation is reduced, thereby improving the surface quality. Therefore, the temperature of the strip steel in the zinc pot is controlled to be 440-480 ℃.
In the method for reducing the zinc or zinc particle defects on the surface of the hot-dip galvanized sheet, the strip steel in the step b is dried at the temperature of more than or equal to 90 ℃ after being degreased and cleaned.
In the method for reducing the defects of zinc or zinc particles on the surface of the hot-dip galvanized sheet, the step d is repeated for 3 to 5 times.
Wherein, in the method for reducing the defects of zinc or zinc particles on the surface of the hot-dip galvanized sheet, the step d of gradually adding zinc comprises the following specific operation steps: adding 200kg of zinc, marking the zinc liquid as a liquid level 1 after the liquid level of the zinc is determined, and calculating the liquid level height 2 of 1/5-1/3 reduced zinc liquid by 200kg according to the size of a zinc pot and the density of plating liquid; when the plating solution drops to the liquid level 2, adding a zinc ingot to the liquid level height 1.
In the method for reducing the zinc or zinc particle defects of the hot-dip galvanized sheet surface strip, the timely slag skimming and slag salvaging in the step e is carried out once every 0.5-2 hours. The invention adopts the multi-time zinc adding to reduce the adding amount each time, so that the fluctuation of the liquid level of the plating solution is small, the temperature change is small, and the process stability is improved.
The method for reducing the defects of zinc or zinc particles of the hot-dip galvanized sheet surface strip is obtained by matching a plurality of processes such as controlling the surface cleanliness of the rolled strip steel, degreasing and cleaning, annealing atmosphere, hot-dip plating process, zinc adding mode, slag removing and dredging mode and the like. The degradation rate of judgment and the current rate of the defects of the strip zinc or the zinc particles of the hot-dip galvanized sheet are greatly reduced, the rate of judgment is reduced from 2% to 0.6%, and the defects are effectively treated. At present, the average monthly output and sales volume of the steel-climbing hot galvanizing products is 4 ten thousand tons, and the average sale price difference between the current goods and the certified goods is about 800 yuan/ton. Therefore, the implementation of the patent has obvious economic and social benefits.
Meanwhile, the defects of zinc or zinc particles of the hot-dip galvanized sheet surface noodles are effectively treated, so that the galvanizing unit can continue to produce normally, the requirements of the household appliance user market on corresponding products are met, the adverse effects of the users caused by the surface defects are avoided, and the share of the steel product market is ensured.
The following examples are intended to illustrate specific embodiments of the present invention without limiting the scope of the invention to the examples.
Example 1 hot-dip galvanized sheet prepared by the method of the present invention
The hot-dip galvanized sheet is prepared by adopting the existing production line, wherein the control is as follows:
a. after the strip steel is rolled, the cleanliness is controlled to ensure that the miscellaneous oil content of the emulsion is 14 percent;
b. when the strip steel is degreased and cleaned, the temperature of alkali liquor in an alkali liquor tank is controlled to be 45 ℃, the alkalinity of the alkali liquor is controlled to be 30Pt., the electrolytic current of an electrolytic tank is 6000A, and the free alkalinity of a cleaning tank is controlled to be 14 Pt.;
c. during continuous annealing, controlling hydrogen in the furnace to be 2.5 percent;
d. when in hot dipping, the Al content in the plating solution is controlled to be 0.16 percent; the temperature of the strip steel in a zinc pot is 450 ℃; the temperature of the plating solution is 455 ℃; the zinc ingot is added by 3 times by adopting a gradual zinc adding method.
e. And timely slagging off and dredging slag, and fishing out from the side scraping to the edge of the strip steel every 0.5h, and avoiding the fluctuation of the plating solution.
In example 1, the current defective rate of zinc bar or zinc particle defects was controlled to about 0.75% and 0.80% or less. The texture map of the prepared zinc plate is shown in figure 1.
Example 2 Hot-dip galvanized sheet prepared by the method of the present invention
The hot-dip galvanized sheet is prepared by adopting the existing production line, wherein the control is as follows:
a. after the strip steel is rolled, the cleanliness is controlled to ensure that the content of the miscellaneous oil in the emulsion is 10 percent;
b. when the strip steel is degreased and cleaned, the temperature of alkali liquor in an alkali liquor tank is controlled to be 60 ℃, the alkalinity of the alkali liquor is controlled to be 60Pt., the electrolytic current of an electrolytic tank is 8000A, and the free alkalinity of a cleaning tank is 10 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 3.5 percent;
d. when in hot dipping, the Al content in the plating solution is controlled to be 0.20 percent; the temperature of the strip steel in a zinc pot is 460 ℃; the temperature of the plating solution is 460 ℃; a step-by-step zinc adding method is adopted, and zinc ingots are added for 5 times;
e. and timely slagging off and dredging slag, and fishing out from the side scraping to the edge part of the strip steel every 1h to avoid fluctuation of the plating solution.
In example 2, the current defective rate of zinc bar or zinc particle defects was controlled to about 0.50% and to 0.80% or less.
Example 3 Hot-dip galvanized sheet prepared by the method of the present invention
The hot-dip galvanized sheet is prepared by adopting the existing production line, wherein the control is as follows:
a. after the strip steel is rolled, the cleanliness is controlled to ensure that the miscellaneous oil content of the emulsion is 6 percent;
b. when the strip steel is degreased and cleaned, the temperature of alkali liquor in an alkali liquor tank is controlled to be 90 ℃, the alkalinity of the alkali liquor is controlled to be 80Pt., the electrolytic current of an electrolytic tank is 9500A, and the free alkalinity of a cleaning tank is 6 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 5.0 percent;
d. when in hot dipping, the Al content in the plating solution is controlled to be 0.20 percent; the temperature of the strip steel in a zinc pot is 480 ℃; the temperature of the plating solution is 475 ℃; an automatic zinc adding method is adopted;
e. and timely slagging off and dredging slag, and fishing out from the side scraping to the edge part of the strip steel every 2 hours to avoid fluctuation of the plating solution.
In example 3, the in-line defect stock ratio of zinc bars or zinc particles was controlled to about 0.45% and to 0.80% or less.
Comparative example 1 a hot-dip galvanized sheet was prepared without using the method of the present invention
The hot-dip galvanized sheet is prepared by adopting the existing production line, wherein the control is as follows:
a. after the strip steel is rolled, the cleanliness is controlled to ensure that the miscellaneous oil content of the emulsion is 16 percent;
b. when the strip steel is degreased and cleaned, the temperature of alkali liquor in an alkali liquor tank is controlled to be 35 ℃, the alkalinity of the alkali liquor is controlled to be 25Pt., the electrolytic current of an electrolytic tank is 5000A, and the free alkalinity of a cleaning tank is 16 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 2.3 percent;
d. when in hot dipping, the Al content in the plating solution is controlled to be 0.26 percent; the temperature of the strip steel in a zinc pot is 485 ℃; the temperature of the plating solution is 480 ℃; adding 200kg of zinc ingot at one time;
e. and (4) timely slagging off and slag fishing, and fishing out from the side of the strip steel to the edge part every 3h to avoid fluctuation of the plating solution.
The hot-dip galvanized sheet prepared by the production process does not adopt any measures, the current rate of defects of strip zinc or zinc particles is 2.8 percent, and the texture map of the prepared zinc sheet is shown in figure 2.
Comparative example 2 production of a Hot-galvanized sheet without Using the method of the present invention
The current rate of defects of the zinc strip or the zinc particles is 1.60% only by adopting a method for controlling degreasing cleaning, and the texture chart of the prepared zinc plate is shown in figure 3.
Comparative example 3 production of a Hot-galvanized sheet without Using the method of the invention
The method for controlling the surface cleanliness of the rolled strip steel is only adopted, and the spot rate of the defects of the strip zinc or zinc particles is 1.50 percent.
Comparative example 4 production of a Hot-galvanized sheet without Using the method of the present invention
Only the method of controlling the zinc adding mode and the slag skimming and dragging technology is adopted, and the current rate of the defects of zinc bars or zinc particles is 1.90 percent.
The current rate of the defects of the zinc strips or the zinc particles is as follows: and (3) when the serious condition that the surface of the galvanized steel sheet with strip zinc or zinc particle defects has obvious hand feeling or is densely distributed in sheets cannot meet the requirements of users, treating the galvanized steel sheet according to degradation judgment (namely, spot goods), wherein the proportion of the weight of the degradation judgment to the total weight of production is the spot goods rate (or the degradation judgment rate).
Claims (7)
1. The method for reducing the defects of zinc or zinc particles on the surface of hot-dip galvanized sheet is characterized by comprising the following steps:
a. after rolling the strip steel, controlling the cleanliness to ensure that the content of the miscellaneous oil in the emulsion is 6-15%;
b. when the strip steel is degreased and cleaned, controlling the temperature of alkali liquor in an alkali liquor tank to be 40-90 ℃, the alkalinity of the alkali liquor to be 30-90 Pt., the electrolytic current of the electrolytic tank to be 6000-10000A, and the free alkalinity of a cleaning tank to be less than 15 Pt.;
c. during continuous annealing, controlling the hydrogen in the furnace to be more than or equal to 2.0 percent;
d. when hot dipping, controlling the Al content in the plating solution to be 0.15-0.25%, the temperature of strip steel entering a zinc pot to be 440-480 ℃, and the temperature of the plating solution to be 455-475 ℃; a step-by-step zinc adding method or automatic zinc adding is adopted, and zinc ingots are added for multiple times;
e. the slag is removed in time and fished out from the side of the strip steel to the edge part, thus avoiding the fluctuation of the plating solution.
2. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: the emulsified mixed oil in the step a is at least one of rolling mill oil mist or oil generated by a Morgan, a gear and a main and auxiliary hydraulic system mixed in the emulsified liquid.
3. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: and (b) after degreasing and cleaning the strip steel, drying the strip steel at the temperature of more than or equal to 90 ℃.
4. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: and d, controlling the absolute value of the temperature difference between the temperature of the strip steel entering the zinc pot and the temperature of the plating solution to be less than or equal to 5.
5. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: and d, repeating the step d for 3-5 times.
6. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: the specific operation method for gradually adding zinc in the step d comprises the following steps: adding 200kg of zinc, marking the zinc liquid as a liquid level 1 after the liquid level of the zinc is determined, and calculating the liquid level height 2 of 1/5-1/3 reduced zinc liquid by 200kg according to the size of a zinc pot and the density of plating liquid; when the plating solution drops to the liquid level 2, adding a zinc ingot to the liquid level height 1.
7. The method for reducing zinc or zinc particle defects on the surface of hot-dip galvanized sheet according to claim 1, wherein: and e, timely slag skimming and slag fishing refers to skimming and slag fishing once every 0.5-2 hours.
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| CN114150249A (en) * | 2021-11-25 | 2022-03-08 | 山东钢铁集团日照有限公司 | Method for controlling zinc slag on surfaces of galvanized household appliances and automobile plates |
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