Production method of thick-specification chromium-free fingerprint-resistant hot galvanized plate

Abstract

The invention belongs to the technical field of production of hot-dip galvanized plates, and particularly relates to a production method of a thick-specification chromium-free fingerprint-resistant hot-dip galvanized plate. Comprising the following steps: in the production process of a hot-dip galvanized plate, controlling the temperature of a pre-oxidation chamber of an annealing furnace, controlling the components and temperature of zinc liquid, controlling the parameters of a roller coater, and controlling the temperature and humidity of a post-treatment drying furnace by adopting a high-pressure and low-speed narrow lap welding mode. According to the invention, through optimization of welding, annealing, galvanization, fingerprint-resistant passivation and post-treatment drying procedures, the product quality is greatly improved, the product percent of pass is improved from 88.36% to 99.37% or more, the unit stability is good, and the hourly yield is improved from 60t / h to 83t / h or more.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-dip galvanized sheet production, and in particular relates to a production method of a thick-gauge chrome-free, fingerprint-resistant hot-dip galvanized sheet. Background Art

[0002] At present, competition in the home appliance and photovoltaic industries is becoming increasingly fierce, and customers' requirements for products are also increasing, pursuing both excellent quality and affordable prices. In this context, steel, as a key raw material supporting these two industries, is undergoing a transformation from traditional materials such as ordinary cold-coated and trivalent chromium galvanized sheets to fingerprint-resistant hot-dip galvanized sheets. Fingerprint-resistant hot-dip galvanized sheets are highly favored for their excellent lubricity, anti-corrosion performance and excellent surface quality.

[0003] However, for fingerprint-resistant hot-dip galvanized sheets with a thickness of more than 1.5 mm, they face challenges in actual applications, such as difficulty in welding, easy deviation in the furnace, uneven surface quality, and insufficient curing ability of the passivation film. These problems seriously restrict the production efficiency and product quality improvement of steel mills.

[0004] At present, the qualified rate of thick-specification fingerprint-resistant hot-dip galvanized sheet is only 88.36%, the average hourly output is 60t / h, the dynamic friction coefficient is only 0.14, and the corrosion area is between 7% and 8% in a 96-hour neutral salt spray test.

[0005] Patent No. CN1974836B provides a method for manufacturing a hot-dip galvanized fingerprint-resistant plate. The patent has stricter requirements on the post-processing drying plate temperature PMT, and its control range is narrower, thereby increasing the difficulty of control.

[0006] Patent No. CN117904516A provides a method for producing hot-dip galvanized fingerprint-resistant coated steel sheets. The method is a conventional method for producing hot-dip galvanized fingerprint-resistant galvanized sheets. The core of the method is to rely on the performance of fingerprint-resistant agents to improve product performance, and product quality fluctuates greatly. Summary of the invention

[0007] The purpose of the present invention is to provide a production method of a thick-gauge chromium-free fingerprint-resistant hot-dip galvanized sheet to solve the problems existing in the prior art.

[0008] The technical solution adopted by the present invention to solve its technical problem is:

[0009] A method for producing thick-gauge chrome-free, fingerprint-resistant hot-dip galvanized sheet comprises the following steps: in the production process of the hot-dip galvanized sheet, a narrow lap welding method with high pressure and low speed is adopted to control the temperature of a pre-oxidation chamber of an annealing furnace, the composition and temperature of zinc liquid, the parameters of a roller coater, and the temperature and humidity of a post-processing drying furnace.

[0010] Furthermore, the production process of hot-dip galvanized sheet is to carry out the following steps in sequence: cold hard coil loading, uncoiling, welding, cleaning, annealing, galvanizing, cooling after plating, finishing, straightening, fingerprint resistance passivation, post-processing drying, post-processing cooling, trimming, inspection, oiling, coiling, coiling, bundling, packaging, and warehousing.

[0011] Furthermore, the thickness of the strip steel used in the production of hot-dip galvanized sheets is above 1.5 mm.

[0012] Furthermore, a narrow lap welding method with high pressure and low speed is adopted, in which the welding speed is controlled at 5-10 m / min and the welding pressure is 16-23 KN during the welding process.

[0013] Furthermore, the temperature of the pre-oxidation chamber of the annealing furnace is controlled so that, during the annealing process, when the temperature of the heating section of the annealing furnace is above 760°C, the temperature of the pre-oxidation chamber in the heating section of the annealing furnace is accurately controlled at 700-750°C to prevent the strip from deviating in the furnace due to thermal shock.

[0014] Furthermore, the composition and temperature of the zinc liquid are controlled so that, in the galvanizing process, the Al content in the zinc liquid is 0.24-0.28%, the Fe content is ≤0.012%, the zinc liquid temperature is 455±3°C, and the temperature of the zinc pot plate is 450-465°C.

[0015] Furthermore, the roller coating machine parameters are controlled such that in the anti-fingerprint passivation process, the coating roller speed ratio of the roller coating machine is 90-150%, and the material roller speed ratio is 70-100%, so that the thickness of the chrome-free anti-fingerprint film is 0.9-1.3g / m 2 .

[0016] Furthermore, the temperature and humidity of the post-processing drying furnace are controlled. In the post-processing drying process, the temperature of the hot air drying furnace is controlled at 300-360°C, the temperature of the drying plate is controlled at above PMT80°C, and the humidity of the drying furnace is controlled below 60%RH.

[0017] Furthermore, when the humidity of the drying furnace is controlled, the power of the dehumidification fan is controlled to discharge the wet air in the drying furnace to the outside, and then the circulating fan is used to draw the dry air outside into the drying furnace.

[0018] The present invention has the following beneficial effects:

[0019] 1. The present invention greatly improves product quality by optimizing welding, annealing, galvanizing, anti-fingerprint passivation, and post-processing drying processes, and the product qualification rate is increased from 88.36% to more than 99.37%. The unit has good stability, and the hourly output is increased from 60t / h to more than 83t / h.

[0020] 2. The narrow lap welding method with high pressure and low speed improves the quality of the weld, prevents deformation, avoids repair and rework, and thus improves production efficiency. The stability of the unit is greatly improved. By controlling the temperature of the pre-oxidation chamber of the annealing furnace, the thermal shock is reduced and deviation is prevented. By controlling the composition and temperature of the zinc liquid, the adhesion of the zinc layer is improved, the zinc slag on the surface of the strip is reduced, the parameters of the roller coater are controlled, so that the hot-dip galvanized sheet has good anti-corrosion and lubrication conditions, and the temperature and humidity of the post-processing drying furnace are controlled, thereby improving the curing effect of the passivation film.

[0021] 3. Greatly improve product processing performance, and reduce the dynamic friction coefficient from 0.14 to below 0.09.

[0022] 4. Greatly improve the corrosion resistance of the product, and the corrosion area in the 96h neutral salt spray test is reduced from 7-8% to less than 5%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a physical photograph of the product obtained in Example 1 of the present invention subjected to a 96-hour neutral salt spray test.

[0024] Figure 2 It is a curve chart of the dynamic friction coefficient test of the product obtained in Example 1 of the present invention.

[0025] Figure 3 It is a comparison chart of the qualified rate of products produced continuously for 6 months by the present invention and the qualified rate of the prior art. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] This embodiment provides a method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet. The thickness of the strip steel used in the production of hot-dip galvanized sheet is 2 mm. The production process of hot-dip galvanized sheet is to carry out the following steps in sequence: cold hard coil loading, uncoiling, welding, cleaning, annealing, galvanizing, cooling after plating, finishing, straightening, fingerprint-resistant passivation, post-processing drying, post-processing cooling, trimming, inspection, oiling, coiling, coiling, bundling, packaging, and warehousing. The key parameters in the production process are shown in the following table:

[0028] Table 1: Key parameter control in the production process of hot-dip galvanized steel sheets

[0029]

[0030] As shown in Table 1, during the welding process, increasing the pressure can make the contact surface of the weld joint closer, thereby improving the shear strength and tensile strength of the weld, which is conducive to forming a good weld and helps to reduce the deformation caused by thermal expansion and contraction during the welding process. Low-speed welding makes the welding process more stable, reduces fluctuations and errors in the welding process, thereby improving the quality of the weld and reducing local deformation caused by heat concentration. Although low speed means a relatively long welding time, a stable welding process and high-quality welds help reduce the time for repair and rework after welding.

[0031] In the annealing process, the temperature of the heating section of the annealing furnace is above 760°C, and the temperature of the pre-oxidation chamber in the heating section of the annealing furnace is precisely controlled at 700-750°C to prevent the strip from running off the furnace due to thermal shock. The pre-oxidation chamber refers to a chamber in the middle of the heating section of the continuous annealing furnace. The chamber has no radiation tubes and is separated from the heating section by sealing rollers and furnace walls. The temperature of the chamber is generally much lower than the temperature of other locations in the heating section. Thermal shock refers to the uneven force caused by large temperature differences when the strip enters the annealing furnace at different times, resulting in deviation.

[0032] In the galvanizing process, the Al content in the zinc liquid is controlled at 0.24-0.28%, the Fe content is ≤0.012%, the zinc liquid temperature is 455±3℃, and the temperature of the zinc pot plate is 450-465℃, which can improve the adhesion of the zinc layer and reduce the zinc slag on the surface of the strip.

[0033] In the anti-fingerprint passivation process, the coating roller speed ratio of the roller coater is 90-150%, and the material roller speed ratio is 70-100%, so that the thickness of the chrome-free anti-fingerprint film is 0.9-1.3g / m 2 , thus making the hot-dip galvanized sheet have good anti-corrosion and lubrication conditions.

[0034] In the post-processing drying process, the temperature of the hot air drying oven is controlled at 300-360℃, the temperature of the drying plate is controlled at above PMT80℃, and the humidity of the drying oven is controlled below 60%RH, so as to improve the curing effect of the passivation film. When controlling the humidity of the drying oven, the humid air in the drying oven is discharged to the outside by controlling the power of the dehumidification fan, and then the dry air outside is drawn into the drying oven by the circulating fan.

[0035] During the production process, the strip steel ran stably without deviation, and the unit output was 86t / h.

[0036] like Figure 1As shown, the thick-gauge chrome-free anti-fingerprint passivation product obtained in this embodiment was subjected to a neutral salt spray test (NSS), and the experimental conditions were: analytical pure NaCl, concentration 50±0.5g / L, pH value: 6.5-7.2, test chamber temperature: 35±2°C, saturated barrel temperature: 45°C, and mist fall: 1.5-2ml / h. Experimental results: The corrosion area of ​​the sample was <1%.

[0037] like Figure 2 As shown, the thick-gauge chrome-free anti-fingerprint passivation product obtained in this embodiment was tested for the dynamic friction coefficient. The experimental conditions were: a reciprocating dynamic friction coefficient was measured with a load of 0.98N and a Stainless steel ball. Experimental results: The dynamic friction coefficient is 0.087.

[0038] like Figure 3 As shown, by using the production method of a thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet provided by the present invention, continuous production was carried out for 6 months, and the average value of the product qualification rate each month was calculated and compared with the prior art. The qualification rate of the obtained thick-gauge chrome-free fingerprint-resistant passivated products was significantly improved.

[0039] The above-described embodiments are merely descriptions of preferred implementations of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made by ordinary persons in the art to the technical solution of the present invention should all fall within the scope of protection of the present invention.

[0040] The techniques, shapes, and structural parts not described in detail in the present invention are all well-known techniques.

Claims

1. A method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet, characterized in that: This includes using high-pressure, low-speed narrow lap welding in the production process of hot-dip galvanized sheets, controlling the temperature of the pre-oxidation chamber of the annealing furnace, controlling the composition and temperature of the zinc liquid, controlling the parameters of the roller coater, and controlling the temperature and humidity of the post-processing drying furnace.

2. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 1, characterized in that: The production process of the hot-dip galvanized sheet is to carry out the following steps in sequence: cold hard coil loading, uncoiling, welding, cleaning, annealing, galvanizing, cooling after plating, finishing, straightening, fingerprint resistance passivation, post-treatment drying, post-treatment cooling, trimming, inspection, oiling, coiling, coiling, bundling, packaging, and warehousing.

3. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The thickness of the strip steel used in the production of the hot-dip galvanized sheet is above 1.5 mm.

4. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The narrow lap welding method using high pressure and low speed is that in the welding process, the welding speed is controlled at 5-10m / min and the welding pressure is 16-23KN.

5. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The temperature of the pre-oxidation chamber of the annealing furnace is controlled in such a way that, in the annealing process, when the temperature of the heating section of the annealing furnace is above 760° C., the temperature of the pre-oxidation chamber in the heating section of the annealing furnace is precisely controlled at 700-750° C. to prevent the strip from deviating in the furnace due to thermal shock.

6. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The composition and temperature of the zinc liquid are controlled such that, in the galvanizing process, the Al content in the zinc liquid is 0.24-0.28%, the Fe content is ≤0.012%, the zinc liquid temperature is 455±3°C, and the temperature of the zinc pot plate is 450-465°C.

7. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The control parameters of the roller coater are as follows: in the anti-fingerprint passivation process, the coating roller speed ratio of the roller coater is 90-150%, and the material feeding roller speed ratio is 70-100%, so that the thickness of the chrome-free anti-fingerprint film is 0.9-1.3g / m 2 .

8. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 2, characterized in that: The temperature and humidity of the post-processing drying furnace are controlled as follows: in the post-processing drying process, the temperature of the hot air drying furnace is controlled at 300-360°C, the temperature of the drying plate is controlled at above PMT80°C, and the humidity of the drying furnace is controlled at below 60%RH.

9. The method for producing thick-gauge chrome-free fingerprint-resistant hot-dip galvanized sheet according to claim 8, characterized in that: When the humidity of the drying furnace is controlled, the power of the dehumidifying fan is controlled to discharge the wet air in the drying furnace to the outside, and then the circulating fan is used to draw the dry air outside into the drying furnace.

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