Method for eliminating zinc ash defect of galvanized automobile sheet

Abstract

The invention relates to a method for eliminating the zinc ash defect of a galvanized automobile sheet, and belongs to the technical field of hot galvanizing processes. The method comprises the following steps: feeding cold-rolled strip steel into a reaction pot of a hot-dip galvanizing production line; nitrogen and hydrogen humidifying gas is introduced into the furnace nose of the hot-dip galvanizing production line so as to control the dew point in the furnace nose; heating the side wall of the furnace nose to enable the side wall of the furnace nose to reach a first set temperature, and arranging a diffusing pipeline for the furnace nose to reduce accumulation of zinc ash in the furnace nose; adjusting the temperature of the zinc liquid in the reaction pot to a second set temperature to reduce the volatilization speed of the zinc liquid so as to control the generation of zinc ash; and the zinc liquid containing zinc ash and zinc slag overflows into an overflow groove through a zinc liquid overflow device and then is pumped out through a zinc ash pump. By comprehensively applying various measures, the problem of zinc ash defects of the galvanized automobile sheet is effectively solved, and the competitiveness and market value of the product are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of hot galvanizing process, in particular to a method for eliminating zinc ash defects of galvanized automobile sheet. BACKGROUND

[0002] In recent years, with the deep implementation of the concept of low-carbon environmental protection, energy saving and consumption reduction, and the pursuit of maximum economic effect, industrial users have put forward more stringent requirements for the quality and precision of cold-rolled steel products. Under this background, galvanized products, especially galvanized automobile sheet, are widely used in the automobile manufacturing industry due to their excellent corrosion resistance and good processing performance. However, the zinc ash problem faced by galvanized automobile sheet in the production process has become a bottleneck restricting the improvement of product quality and the increase of outer plate production.

[0003] Zinc ash, a by-product produced in the process of cold-rolled galvanizing, not only affects the surface quality of galvanized automobile sheet, but also may cause product downgrading, and even cannot meet the quality requirements of customers. In the production process of cold-rolled galvanized products, the zinc ash problem almost exists in the production line of each factory. Due to the generation of zinc ash, many products that can originally meet high standards have to be downgraded, causing huge economic losses to the production enterprises. SUMMARY

[0004] The present application provides a method for eliminating zinc ash defects of galvanized automobile sheet, to solve the technical problem of how to solve the zinc ash defect problem in the production process of galvanized automobile sheet.

[0005] The present application provides a method for eliminating zinc ash defects of galvanized automobile sheet, which comprises:

[0006] sending the cold-rolled steel strip into the reaction pot of the hot-dip galvanizing production line;

[0007] passing nitrogen-hydrogen humidified gas into the furnace nose of the hot-dip galvanizing production line to control the dew point in the furnace nose;

[0008] heating the side wall of the furnace nose to make the side wall of the furnace nose reach a first set temperature, and setting a diffusion pipeline for the furnace nose to reduce the accumulation of zinc ash in the furnace nose;

[0009] adjusting the temperature of the zinc liquid in the reaction pot to a second set temperature to reduce the volatilization speed of the zinc liquid, thereby controlling the generation of zinc ash;

[0010] using a zinc liquid overflow device to overflow the zinc liquid containing zinc ash and zinc residue into an overflow tank, and then pumping out by a zinc ash pump.

[0011] Optionally, the temperature of the nitrogen-hydrogen humidified gas is 450℃-470℃.

[0012] Optionally, for the machine set without zinc liquid overflow device in the furnace nose, the temperature of the dew point is -25℃ to -15℃; for the machine set with zinc liquid overflow device in the furnace nose, the temperature of the dew point is -20℃ to -10℃.

[0013] Optionally, the oxygen content in the furnace nose is less than 10ppm in volume fraction.

[0014] Optionally, the hydrogen content in the furnace nose is 4% to 6% in volume fraction.

[0015] Optionally, the fluctuation range of the liquid level of the overflow tank is less than or equal to ±2mm.

[0016] Optionally, the first set temperature is 460℃ to 500℃.

[0017] Optionally, the second set temperature is 455℃ to 460℃.

[0018] Optionally, the composition of the zinc liquid includes Al: 0.21% to 0.27% in mass fraction.

[0019] Optionally, the fluctuation range of the liquid level of the zinc liquid is less than or equal to ±2mm.

[0020] Compared with the prior art, the above technical solution provided by the embodiments of the present application has the following advantages:

[0021] The present application provides a method for eliminating zinc dust defects of galvanized automobile sheet, which comprises: feeding a cold-rolled strip into a reaction pot of a hot-dip galvanizing production line; introducing a nitrogen-hydrogen humidifying gas into a furnace nose of the hot-dip galvanizing production line to control the dew point in the furnace nose; heating the side wall of the furnace nose to make the side wall of the furnace nose reach a first set temperature, and setting a diffusion pipeline for the furnace nose to reduce the accumulation of zinc dust in the furnace nose; adjusting the temperature of the zinc liquid in the reaction pot to a second set temperature to reduce the volatilization speed of the zinc liquid, thereby controlling the generation of zinc dust; using a zinc liquid overflow device to overflow the zinc liquid containing zinc dust and zinc residue into an overflow tank, and then pumping out the zinc dust by a zinc dust pump. By controlling the atmosphere in the furnace nose, the generation of zinc vapor is inhibited, and the generation of zinc oxide is reduced. By accurately controlling the temperature and liquid level of the zinc liquid, the galvanizing process conditions are stabilized. By maintaining the continuous and stable overflow of the upper and lower surfaces of the strip in the width direction, the adhesion of zinc dust is reduced, thereby effectively solving the problem of zinc dust defects of the galvanized automobile sheet, and improving the competitiveness and market value of the product. BRIEF DESCRIPTION OF DRAWINGS

[0022] The drawings incorporated into the specification and forming a part thereof, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the application.

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort.

[0024] Figure 1 A flowchart of a method for eliminating zinc dust defects of galvanized automobile sheet provided by the embodiments of the present application. DETAILED DESCRIPTION

[0025] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will combine the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of the present application.

[0026] The various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is only for the convenience and brevity, and should not be understood as a hard limit to the scope of the present application; therefore, it should be considered that the described range has specifically disclosed all possible sub-ranges and single values in the range; for example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which is applicable to any range; in addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0027] In this document, the terms "comprises", "comprising", "includes", "including" or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, includes or includes elements or steps does not include only those elements or steps but can include other elements or steps not expressly listed or inherent to such process, method, article, or apparatus. The terms "first", "second", "third", etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. The term "and / or", describing the relationship between associated objects, means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, B exists alone; where A and B can be singular or plural. "At least one" means one or more, "multiple" means two or more; "at least one", "at least one of the following" or the like means any combination of the items, including single or multiple combinations; for example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, and c can be single or multiple. The "parts ratio" such as weight parts, mass parts, etc. represents the proportional relationship between components. In the proportional relationship described in this document, the parameters that need to be described in order should be understood as the front item of the proportional formula, and the proportional number should be understood as the latter item of the proportional formula, for example, the mass ratio of substance A, substance B and substance C is 1:2:3, then substance A, substance B and substance C should be corresponding to the proportional number in the proportional formula in the order of description, i.e. the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0028] Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in this document can be purchased from the market or prepared by existing methods.

[0029] Figure 1 A flowchart of a method for eliminating zinc dust defects of galvanized automobile sheet provided by the embodiments of the present application.

[0030] Please refer to Figure 1 The embodiments of the present application provide a method for eliminating zinc dust defects of galvanized automobile sheet, which comprises:

[0031] S1, feeding a cold-rolled strip into a reaction pot of a hot-dip galvanizing production line;

[0032] S2, introducing a nitrogen-hydrogen humidifying gas into a furnace nose of the hot-dip galvanizing production line to control the dew point in the furnace nose;

[0033] In the production process of galvanized steel strip, the steel strip must pass through the connecting channel between the annealing furnace and the reaction pot (zinc pot), which is called furnace nose in the steel strip industry.

[0034] In some embodiments, the temperature of the nitrogen-hydrogen humidified gas is 450-470°C.

[0035] In this temperature range, the reaction of the nitrogen-hydrogen humidified gas with the zinc liquid is more complete and stable, which helps to form a uniform zinc oxide film, thereby inhibiting the excessive generation of zinc vapor and reducing the generation of zinc ash.

[0036] In some embodiments, for the unit without a zinc liquid overflow device in the furnace nose, the temperature of the dew point is -25 to -15°C; for the unit with a zinc liquid overflow device in the furnace nose, the temperature of the dew point is -20 to -10°C.

[0037] Dew point control is to inhibit the generation rate of zinc vapor on the zinc liquid surface by adjusting the atmosphere in the furnace nose. In the embodiments of the present application, the nitrogen-hydrogen mixed gas is injected into the furnace nose after being introduced into a humidification tank containing water, and reacts with the zinc liquid at high temperature to generate a ZnO (and part of Al2O3) film to inhibit the generation of zinc vapor. The purpose of generating the oxidation film on the zinc liquid surface is to inhibit the generation rate of zinc vapor on the zinc liquid surface, and the formation rate of the oxidation film is closely related to the dew point value in the furnace nose. The higher the dew point, the more the content of H2O in the furnace nose, and the greater the driving force for the formation of the oxidation film. However, if the dew point is too high, the oxidation film on the zinc liquid surface will partially adhere to the surface of the steel strip subsequently, and a too high dew point will cause the steel strip to generate iron oxide with water vapor, affecting the adhesion of the zinc layer and the surface quality of the steel strip. For the unit without a zinc liquid overflow device in the furnace nose, the dew point is controlled at -25 to -15°C; for the unit with a zinc liquid overflow device in the furnace nose, the dew point is preferably controlled at -20 to -10°C. By accurately controlling the dew point, the possibility of zinc ash accumulating in the furnace nose and falling onto the steel strip can be reduced, which directly improves the product quality of the galvanized sheet and reduces the product degradation or scrap caused by zinc ash defects.

[0038] In some embodiments, the oxygen content in the furnace nose is <10 ppm in volume fraction.

[0039] Oxygen is one of the main factors for the oxidation of zinc liquid, when the oxygen content in the furnace nose is too high (≥10 ppm), the zinc liquid will react with oxygen to generate zinc oxide (ZnO), which is one of the main components of zinc ash. By controlling the oxygen content at a low level of <10 ppm, the contact and reaction of zinc liquid with oxygen can be significantly reduced, thereby reducing the generation amount of zinc ash; in addition, too high oxygen content (≥10 ppm) will not only cause the oxidation of zinc liquid, but also may cause the oxidation of the surface of the steel strip to form impurities such as iron oxide, which will adhere to the surface of the steel strip, affecting the adhesion of the zinc layer and the overall surface quality of the steel strip. Controlling the oxygen content at <10 ppm can effectively avoid this problem and protect the surface quality of the steel strip. Therefore, the furnace nose needs to be well sealed to prevent leakage, and nitrogen gas (or nitrogen-hydrogen protective gas) can also be introduced to reduce the oxygen content.

[0040] In some embodiments, the hydrogen content in the furnace nose is 4% to 6% by volume fraction.

[0041] According to the chemical reaction (reversible reaction), hydrogen can promote the reaction to the right, thereby reducing the amount of ZnO, controlling the hydrogen content in the furnace nose at 4% to 6%, which can optimize this chemical reaction, help to reduce the generation of zinc ash, and improve the product quality of galvanized automobile sheet; in addition, during the galvanizing process, zinc liquid reacts with oxygen to generate zinc oxide, and the presence of hydrogen can inhibit this oxidation process to some extent. By controlling the hydrogen content in the range of 4% to 6%, the oxidation and reduction reactions of the zinc liquid can be balanced, and unnecessary zinc oxide generation can be reduced, thereby further reducing the generation of zinc ash.

[0042] S3, heating the side wall of the furnace nose to reach a first set temperature, and setting a diffusion pipeline for the furnace nose to reduce the accumulation of zinc ash in the furnace nose;

[0043] In some embodiments, the first set temperature is 460°C to 500°C.

[0044] In the furnace nose, zinc vapor is prone to condense into zinc ash when it encounters a cold surface. By heating the side wall of the furnace nose and controlling the temperature at 460°C to 500°C, the temperature of the side wall can be ensured to be higher than the condensation point of zinc vapor, thereby effectively preventing the condensation and adhesion of zinc ash on the side wall, which helps to reduce the pollution of zinc ash to the strip steel and improve the product quality.

[0045] For gaseous or dispersed solid zinc ash in the furnace nose, it can be diffused out by opening the diffusion pipeline at the upper part of the furnace nose, thereby reducing the accumulation in the furnace nose, and also helping to reduce the mixing of zinc vapor into the annealing furnace main body to pollute the furnace roller, furnace wall, cooling air box, etc.

[0046] In some embodiments, the method for eliminating zinc ash defects of galvanized automobile sheet further comprises: removing the zinc ash on the inner wall of the furnace nose.

[0047] The zinc dust on the inner wall of the furnace nose can be removed by regular cleaning and replacement of the furnace nose tip during maintenance, and on-line zinc dust cleaning, etc. Regular cleaning of the inner wall of the furnace nose and replacement of the furnace nose tip can effectively remove the zinc dust accumulated on the inner wall of the furnace nose for a long time, prevent it from falling and polluting the surface of the strip, and thus improve the surface quality of the product. For zinc pots that cannot be lifted during maintenance, a manhole can be opened from the side to insert a pipeline to blow off the zinc dust. The on-line zinc dust cleaning measure can remove the zinc dust adhered to the inner wall of the furnace nose in time during production, avoiding its long-term accumulation and adverse effects on production. The specific method can be: vibrating the steel structure of the furnace nose to loosen and fall off the zinc dust adhered to the inner wall, so as to facilitate subsequent cleaning; using high-pressure gas to blow off the inner wall of the furnace nose can directly blow off the zinc dust from the inner wall to achieve the purpose of cleaning; heating the inner wall of the furnace nose can make the zinc dust expand and fall off, and also help to reduce the adhesion of the zinc dust on the inner wall, facilitating cleaning.

[0048] S4, adjusting the temperature of the zinc liquid in the reaction kettle to a second set temperature to reduce the volatilization speed of the zinc liquid, thereby controlling the generation of zinc dust;

[0049] In some embodiments, the second set temperature is 455-460°C.

[0050] The temperature of the zinc liquid affects the volatilization speed of the zinc liquid, so the temperature range of the zinc liquid should be strictly controlled and the fluctuation should be reduced. In the embodiments of the present application, the temperature of the zinc liquid is 455-460°C, and the fluctuation range is ±2°C. For products with high surface requirements, the optimal plate temperature entering the zinc pot = the temperature of the zinc liquid, because the temperature difference is one of the important factors leading to the generation of zinc dust and impurities. When the plate temperature entering the zinc pot is equal to the temperature of the zinc liquid, the temperature difference between the strip and the zinc liquid is minimized, which can reduce the volatilization of zinc vapor and the generation of zinc oxide caused by temperature fluctuations, thereby reducing the amount of zinc dust and impurities generated, which helps to maintain the cleanliness of the surface of the strip and improve the product quality.

[0051] In some embodiments, the composition of the zinc liquid includes, in terms of mass fraction: Al: 0.21%-0.27%.

[0052] The presence of aluminum can inhibit the oxidation reaction of the zinc liquid to some extent, and reduce the generation of zinc oxide (the main component of zinc dust).

[0053] In some embodiments, the fluctuation range of the liquid level of the zinc liquid is ≤±2mm.

[0054] A large fluctuation range of the liquid level of the zinc liquid can cause the zinc dust and impurities on the surface of the zinc liquid to be stirred and brought into the galvanized layer, forming defects. By controlling the fluctuation range of the liquid level to be ≤±2mm, the pollution can be effectively reduced, the cleanliness of the surface of the strip can be maintained, and the product quality can be improved.

[0055] To keep the liquid level of zinc stable and reduce the fluctuation of zinc liquid level, the following measures can be taken:

[0056] The operation of zinc pot (adding zinc ingot, removing slag) is gentle: when adding zinc ingot, the operation is stable and slow, and is linked with the zinc liquid level; when removing slag, the operation amplitude is gentle, and it is strictly prohibited to remove and scrape slag with large amplitude, especially the slag scraping on the outer plate, and the distance of tool immersion into the zinc liquid surface in the operation of removing and scraping slag cannot be too deep.

[0057] Reduce the fluctuation of strip: keep the stable control of the speed and tension of the strip in the zinc pot during production to reduce the fluctuation of the strip, and it is also beneficial to reduce the vibration of the steel structure of the furnace nose to avoid the falling of zinc ash; when switching from the production of the outer plate to the production of the inner plate (or vice versa), the running speed of the strip during the transition period should be consistent with the running speed of the outer plate (or the currently produced product) to avoid large fluctuation; installing a supporting roller between the hot tensioning roller and the submerged roller in the furnace nose can also reduce the fluctuation of the strip.

[0058] The zinc ash pump is installed stably to avoid large vibration.

[0059] S5, using the zinc liquid overflow device to overflow the zinc liquid containing zinc ash and zinc slag into the overflow tank, and then pumping out through the zinc ash pump.

[0060] Through the zinc liquid overflow device, the zinc ash and zinc slag attached to the upper and lower surfaces of the strip can be overflowed into the overflow tank together with the zinc liquid, and then pumped out to the outside of the furnace nose through the zinc ash pump, effectively reducing the zinc ash and zinc slag on the surface of the strip and improving the surface quality of the product. In addition, the overflow of the zinc liquid helps to optimize the distribution of the zinc liquid on the surface of the strip, making the galvanized layer more uniform and improving the overall performance of the product.

[0061] The main function of the zinc ash pump is to pump out the zinc ash generated during the galvanizing process from the zinc liquid and discharge it to the outside of the system. In the embodiments of the present application, the rotating speed of the zinc ash pump can be 150-200 rpm, which can ensure that the zinc ash is effectively pumped out and discharged, avoiding the accumulation of zinc ash in the zinc liquid and the pollution of the surface of the strip. In addition, the stable operation of the zinc ash pump also helps to improve the production efficiency and stability. When the zinc ash is effectively discharged, the galvanizing process can proceed more smoothly, reducing the production interruption and debugging time caused by the accumulation of zinc ash. At the same time, stable zinc ash discharge also helps to maintain the continuity and consistency of the production process.

[0062] In some embodiments, the fluctuation range of the liquid level of the overflow tank is ≤±2mm.

[0063] The liquid level stability of the overflow tank is an important factor to maintain the quality of the zinc coating. When the fluctuation range of the liquid level is controlled within ±2 mm, it can ensure that the upper and lower surfaces of the strip steel can uniformly and continuously contact the zinc liquid when passing through the overflow tank, thereby forming a zinc coating with uniform thickness and consistent quality. This helps to improve the overall quality and consistency of the product; in addition, excessive fluctuation of the liquid level will agitate the zinc liquid in the overflow tank, causing zinc ash and impurities to be brought into the zinc coating, forming surface defects. By controlling the fluctuation range of the liquid level of the overflow tank within ±2 mm, the bringing-in of such impurities can be effectively reduced, the cleanliness of the surface of the strip steel is maintained, and the appearance quality and corrosion resistance of the product are improved.

[0064] In some embodiments, the method for eliminating zinc ash defects of galvanized automobile sheet further comprises: adjusting the zinc liquid overflow device to ensure continuous and stable overflow of the upper and lower surfaces of the strip steel in the width direction.

[0065] Maintaining continuous and stable overflow of the upper and lower surfaces of the strip steel in the width direction is an effective measure to reduce zinc ash. Maintaining continuous and stable overflow of the upper and lower surfaces of the strip steel in the width direction means that during the galvanizing process, the upper and lower surfaces of the strip steel can uniformly and continuously overflow the zinc liquid along the entire width direction when passing through the zinc pot. Through this overflow mode, the zinc ash, zinc slag and other impurities adhering to the surface of the strip steel can be effectively removed, thereby reducing zinc ash defects and improving the product quality of the galvanized sheet. By adjusting the lip to a wavy lip surface, the problem of uneven overflow caused by poor levelness can be prevented.

[0066] In some embodiments, the method for eliminating zinc ash defects of galvanized automobile sheet further comprises: spraying a special heat-resistant coating on the inner wall of the lower end of the furnace nose and spraying an anti-slagging coating on the overflow lip.

[0067] Spraying a special heat-resistant coating on the inner wall of the lower end of the furnace nose can reduce zinc ash adhesion; spraying an anti-slagging coating on the overflow lip can prevent zinc slag accumulation from affecting the overflow effect. These measures can also reduce zinc ash defects and improve the surface quality of the sheet.

[0068] In summary, by precisely controlling the atmosphere in the furnace nose, optimizing the dispersion and removal of zinc ash, controlling the overflow and liquid level stability of the zinc liquid, and adjusting the temperature of the zinc liquid, the zinc ash defect problem in the production process of galvanized sheet is effectively solved. This method has the advantages of simple operation, significant effect, controllable cost, etc., and is worthy of wide promotion and application in the relevant industry.

[0069] The present application will be further described below in conjunction with specific examples. The experimental methods in the following examples are generally determined according to national standards / industry standards; if there is no corresponding national standard / industry standard, the general international standard, conventional conditions or the conditions recommended by the manufacturer are used.

[0070] Example 1

[0071] Furnace nose environment control: the strip steel enters the zinc pot through the closed furnace nose cavity, 450℃ nitrogen-hydrogen humidification gas is introduced into the furnace nose, the dew point in the furnace nose is controlled at -18℃, the oxygen content and hydrogen content in the furnace nose are monitored online, the oxygen content is kept <10ppm and the hydrogen content is 4% by adjusting the hydrogen and trace nitrogen; the side wall of the furnace nose is heated to reach 460℃.

[0072] Zinc liquid overflow optimization: the zinc liquid circulation system is started to ensure that the fluctuation range of the liquid level of the overflow tank is ≤±2mm.

[0073] Zinc liquid temperature and liquid level precision control: the zinc liquid temperature is maintained at 455±1℃; the liquid level sensor is linked with the pump set, the liquid level fluctuation is controlled within ±2mm; the Al content in the zinc liquid is 0.22%, the zinc ash pump rotation speed is set at 150r / min, and the production line speed is stable.

[0074] After production is completed, the zinc ash defects of the galvanized strip steel are quantitatively analyzed using an online surface defect inspection instrument, there is only 1 place on the upper surface of the strip steel with zinc ash area ≥3mm 2 , the number of zinc ash on the lower surface is 0.6, and the zinc ash defect rate is 0.6%.

[0075] Example 2

[0076] Furnace nose environment control: the strip steel enters the zinc pot through the closed furnace nose cavity, 460℃ nitrogen-hydrogen humidification gas is introduced into the furnace nose, the dew point in the furnace nose is controlled at -12℃, the oxygen content and hydrogen content in the furnace nose are monitored online, the oxygen content is kept <6ppm and the hydrogen content is 6% by adjusting the hydrogen and trace nitrogen; the side wall of the furnace nose is heated to reach 460℃.

[0077] Zinc liquid overflow optimization: the zinc liquid circulation system is started to ensure that the fluctuation range of the liquid level of the overflow tank is ≤±2mm.

[0078] Zinc liquid temperature and liquid level precision control: the zinc liquid temperature is maintained at 455±1℃; the liquid level sensor is linked with the pump set, the liquid level fluctuation is controlled within ±2mm; the Al content in the zinc liquid is 0.26%, the zinc ash pump rotation speed is set at 150r / min, and the production line speed is stable.

[0079] After production is completed, the zinc ash defects of the galvanized strip steel are quantitatively analyzed using an online surface defect inspection instrument, there is only 0.6 place on the average upper surface of the strip steel with zinc ash area ≥3mm 2 , the average number of zinc ash on the lower surface is 0.3, and the zinc ash defect rate is 0.3%.

[0080] Example 3

[0081] Furnace nose environment control: the strip steel enters the zinc pot through the closed furnace nose cavity, 450℃ nitrogen hydrogen humidifying gas is introduced into the furnace nose, the dew point in the furnace nose is controlled at -19℃, the oxygen content and hydrogen content in the furnace nose are monitored online, the oxygen content is kept <9ppm and the hydrogen content is 5% by adjusting by supplementing hydrogen and trace nitrogen; the side wall of the furnace nose is heated to reach 470℃.

[0082] Zinc liquid overflow optimization: the zinc liquid circulation system is started to ensure that the fluctuation range of the liquid level of the overflow tank is ≤±2mm.

[0083] Zinc liquid temperature and liquid level precise control: the zinc liquid temperature is maintained at 455±1℃; the liquid level sensor is linked with the pump set, the liquid level fluctuation is controlled within ±2mm; the Al content in the zinc liquid is 0.24%, the zinc ash pump rotating speed is set at 180r / min, and the production line speed is stable.

[0084] After the production is completed, the on-line surface defect inspection instrument is used to quantitatively analyze the zinc ash defects of the galvanized strip steel, the average zinc ash area on the upper surface of the strip steel is ≥3mm 2 , the average number of zinc ash on the lower surface is 0.6, and the zinc ash defect rate is 0.45%.

[0085] It can be known from the embodiments that the zinc ash of the strip steel after galvanizing is significantly reduced by the specific process parameter control, and the surface quality is good.

[0086] In addition, one or more technical solutions in the embodiments of the present application at least have the following technical effects or advantages:

[0087] The embodiments of the present application greatly reduce the generation of zinc ash, which directly improves the product quality of the galvanized sheet, and reduces the product degradation or scrap caused by zinc ash defects.

[0088] The embodiments of the present application avoid frequent shutdown and cleaning operations in the production process by reducing the generation and accumulation of zinc ash, thereby improving the production efficiency.

[0089] The embodiments of the present application reduce the product degradation and scrap caused by zinc ash defects, and improve the production efficiency, which helps to reduce the production cost.

[0090] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined in the present application can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown in the present application, but will conform to the widest scope consistent with the principles and novel features of the present application.

Claims

1. A method for eliminating zinc ash defects in galvanized automobile sheets, the method comprising: Feeding cold-rolled strip into the reaction pot of hot-dip galvanizing production line; introducing nitrogen and hydrogen humidified gas into the nose of the hot-dip galvanizing production line to control the dew point in the nose of the hot-dip galvanizing production line; heating the side wall of the furnace nose to make the side wall of the furnace nose reach a first set temperature, and simultaneously providing a dissipation pipe for the furnace nose to reduce the accumulation of zinc ash in the furnace nose; Adjusting the temperature of the zinc liquid in the reaction pot to a second set temperature to reduce the volatilization rate of the zinc liquid, thereby controlling the generation of zinc ash; A zinc liquid overflow device is used to overflow the zinc liquid containing zinc ash and zinc slag into an overflow tank, and then the zinc liquid is pumped out through a zinc ash pump.

2. The method according to claim 1, characterized in that For the unit without a zinc liquid overflow device in the furnace nose, the dew point temperature is -25℃~-15℃; for the unit with a zinc liquid overflow device in the furnace nose, the dew point temperature is -20℃~-10℃.

3. The method according to claim 1, characterized in that The temperature of the nitrogen-hydrogen humidified gas is 450°C to 470°C.

4. The method according to claim 1, wherein Measured by volume fraction, the oxygen content in the furnace nose is <10 ppm.

5. The method according to claim 1, wherein Calculated by volume fraction, the hydrogen content in the furnace nose is 4% to 6%.

6. The method according to claim 1, characterized in that The fluctuation range of the liquid level of the overflow tank is ≤±2mm.

7. The method according to claim 1, characterized in that The first set temperature is 460°C to 500°C.

8. The method according to claim 1, characterized in that The second set temperature is 455°C to 460°C.

9. The method according to claim 1, characterized in that Calculated by mass fraction, the components of the zinc solution include: Al: 0.21% to 0.27%.

10. The method according to claim 1, characterized in that The fluctuation range of the liquid level of the zinc liquid is ≤±2mm.

Images