Method for preventing side surface plating leakage of G550 aluminized zinc plate

Abstract

The invention discloses a method for preventing side surface skip plating of a G550 aluminum-plated zinc plate. Non-skip plating of the side surface of an aluminum-plated zinc coil is realized through full-flow process control and horizontal annealing furnace process improvement control. Comprising the steps of raw material input time control, cold rolling total reduction rate process control, aluminum-zinc plating horizontal annealing furnace annealing process improvement, open fire section CO concentration control and the like, so that side surface skip plating of the G550 aluminum-zinc plating plate is prevented, and the produced aluminum-zinc plating product is free of side surface skip plating.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip galvanizing, and in particular to a method for preventing side leakage of a G550 galvanized sheet. Background Art

[0002] G550 galvanized products have been more and more widely used in the construction field in recent years. However, it is easy for the side of the G550 product steel coil to be missed during the galvanized production process. There are two main reasons for this. First, the oxide layer formed on the edge of the steel strip during cold rolling, storage and the open flame section of the horizontal annealing furnace is too thick, which causes the oxide layer on the edge of the steel strip to not be well reduced. Then, when the steel strip enters the galvanized pot, the edge of the steel strip and the aluminum-zinc liquid cannot be well combined through chemical reaction to form an alloy layer FeAl3. Finally, when the steel strip is out of the pot, it is found that the side of the steel coil is missed when it is rolled up at the exit. Second, when producing G550 products, the temperature of the open flame section of the horizontal annealing furnace is low, which is easy to produce carbon deposits. The carbon deposits remain on the furnace rollers and are carried to the edge of the steel strip by contact with the edge of the steel strip. When the edge of the steel strip with residual carbon powder enters the galvanized pot, the aluminum-zinc liquid cannot combine with the iron on the edge of the steel strip to form an alloy layer, which causes missed plating. Summary of the invention

[0003] In view of the defects in the prior art, the present invention provides a method for preventing the side surface leakage of G550 aluminum-zinc plate.

[0004] The present invention is achieved through the following technical solutions: A method for preventing G550 galvanized sheet from leaking plating on the side, characterized by: The process time from pickling and trimming to galvanizing of steel coils is controlled within 3 days, and WD40 industrial rust remover is sprayed on the sides of the steel coils before they are put on the galvanizing machine. The purpose is to prevent the steel coils from being exposed to the air for too long, causing the edges of the steel strips to oxidize too much and form a thick oxide layer. Spraying WD40 can remove part of the oxide layer on the edges of the steel strips. At the same time, the steel coils do not need to be packaged to reduce production costs. This can be achieved through planning in a full-process cold rolling factory. The cold rolling section needs to control the cold rolling reduction rate, so as to reduce the plate temperature during the rolling process, thereby reducing the oxide layer thickness of the steel strip during the cold rolling process. The total cold rolling reduction rate is less than or equal to 85%. Preferably, the reduction rate of each pass is less than 25%, and the temperature of the cold rolled coil immediately after rolling is less than or equal to 105°C, so as to reduce the deformation during the rolling process, thereby reducing the plate temperature during the rolling process, and thereby reducing the oxide layer thickness of the edge of the steel strip during the rolling process; The aluminum-zinc horizontal annealing furnace adopts open flame heating with side burners to make the edge temperature of the steel strip high, which is conducive to the reduction of the edge of the steel strip in the subsequent radiation section; the last zone or the last two zones of the open flame section are opened first, which is conducive to the edge of the steel strip quickly entering the radiation tube section at high temperature for reduction; the furnace temperature of the open flame section is greater than or equal to 1200℃, the plate temperature of the open flame section is greater than or equal to 480℃ and less than or equal to 540℃, and the line speed of aluminum-zinc plating is ≥150m / min; the open flame section should ensure that the edge of the steel strip is in the reduction zone; avoid the oxide layer formed on the edge of the steel strip in the open flame section to be too thick, and the high furnace temperature flame will make the edge temperature of the steel strip higher, which is conducive to the subsequent radiation section hydrogen to better reduce the oxide layer of the steel strip edge at high temperature and avoid side leakage; The radiation tube section needs to control the plate temperature between 550-600℃ to ensure that the edge of the steel strip can be better restored in the radiation section after leaving the open flame section; Stop the circulating cooling fan in the cooling section of the horizontal annealing furnace, start the heater, and control the furnace temperature at 550°C to increase the plate temperature to enhance the hydrogen reduction capacity; The low temperature holding section, thermal tension chamber section and descending section of the horizontal annealing furnace need to control the furnace temperature to ≥550℃ to ensure that hydrogen reduces the oxide layer on the edge of the steel strip.

[0005] Preferably, the hydrogen concentration in the horizontal annealing furnace should be controlled at 25%-30% to better reduce the edge of the steel strip.

[0006] Preferably, the CO concentration in the open flame section of the horizontal annealing furnace is controlled to reduce the formation of carbon deposits. The CO concentration control range is: When the G550 plate product thickness is 0.20mm-0.60mm, the CO concentration is 0.5%-0.8%; When the G550 plate product thickness is 0.61mm-1.50mm, the CO concentration is 0.6%-1.0%; For thin plates, the temperature of the open flame section is low, the burner output is low, and carbon deposits are easily generated, so the CO concentration is controlled at a lower level. However, for thick plates, in order to achieve the same annealing plate temperature, the temperature of the open flame section is relatively higher, the burner output is higher, and less carbon deposits are generated. At the same time, more carbon deposits are burned off at high temperatures, so the CO concentration is controlled at a higher level.

[0007] Oxidation mechanism of steel plate during rolling, storage and open flame section in horizontal annealing furnace: 2Fe+O2=2FeO; Fe+CO2=FeO+CO; Fe+H2O=FeO+H2; Reduction mechanism of steel plate at the edge of open flame section in horizontal annealing furnace: FeO+CO= Fe+CO2; FeO+H2= Fe+H2O; Reduction mechanism of steel plate in the radiation section and the edge of the subsequent section in the horizontal annealing furnace: FeO+H2= Fe+H2O.

[0008] The beneficial effects of the present invention are as follows: the present technical solution realizes no leakage on the side of the galvanized coil through the whole process and key point control, including raw material input time control, total cold rolling reduction process control and galvanized annealing process improvement, so as to prevent leakage on the side of the G550 galvanized sheet, better solve the leakage on the side of the G550 product, and solve the new pain points of the industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0010] Figure 1 This is a picture of cold rolled rust.

[0011] Figure 2 These are product photos of each group of experiments in Example 3 of the present invention.

[0012] Figure 3 These are product photos of each group of experiments in Example 4 of the present invention.

[0013] Figure 4 These are product photos of each group of experiments in Example 5 of the present invention.

[0014] Figure 5 These are product pictures and ingredient analysis screenshots of the first experiment of Example 6 of the present invention.

[0015] Figure 6 These are product pictures and ingredient analysis screenshots of the second experiment of Example 6 of the present invention.

[0016] Figure 7 These are product photos of each group of experiments in Example 7 of the present invention. DETAILED DESCRIPTION

[0017] Many specific details are set forth in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited to the specific embodiments disclosed below.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0019] Example 1: Raw material input time control. If the galvanized substrate (i.e., cold-hardened coil) is produced too early and the galvanized line is not produced in time, the cold-hardened coil will rust over time. Especially in the season of high temperature and high humidity, the end of the steel coil will be severely oxidized and even penetrate into the edge of the steel coil. Figure 1 As shown in the figure, if the degreasing and cleaning section of the galvanizing line cannot be effectively removed, the steel coil enters the horizontal annealing furnace. Due to the low annealing temperature, the open flame section cannot be burned off, and the steel strip enters the plating tank. FeAl3 cannot be formed, and the side of the steel coil cannot be plated. Then the side is leaked, which is manifested as the end face of the product turning black. Therefore, the process time of the steel coil from pickling and trimming to the galvanizing and putting into use is controlled within 3 days, and the comparative experiment of the placement time of the cold hardened coil is shown in Table 1.

[0020] Table 1 It can be seen from Table 1 that controlling the storage time of the cold-hardened coil within three days can effectively avoid the side leakage plating.

[0021] Example 2: Controlling the total cold rolling reduction rate and the plate temperature of the cold rolled coil immediately after rolling to reduce the thickness of the oxide layer of the steel strip during the cold rolling process. Specific experimental data are shown in Table 2.

[0022] Table 2 Note: In order to reflect the leakage situation when only one value of the total reduction rate or the offline coil temperature reaches the requirement, the experimental coils of this embodiment adopt different rolling speeds to achieve the regulation of the offline coil temperature, wherein the rolling speeds of experimental coils 1-2 are the same, the rolling speed of experimental coil 3 is different from that of experimental coils 1-2, and the rolling speeds of experimental coils 4-6 are the same and different from the rolling speeds of experimental coils 1-3.

[0023] In actual production, when the reduction rate is controlled below 85%, the coil temperature can usually meet the requirements. If the coil temperature of the cold-rolled coil is still higher than 105°C when the reduction rate is controlled below 85%, the rolling speed needs to be reduced to reduce the coil temperature, so that the coil temperature of the cold-rolled coil is ≤105°C. In addition, other means can also be used to control the plate temperature. For example, if the coil temperature of the cold-rolled coil is higher than 105°C when the reduction rate is controlled below 85%, the steel coil is cooled during cold rolling to make the coil temperature of the cold-rolled coil ≤105°C. The cooling means include air cooling and other methods.

[0024] It can be seen from Table 2 that when the total reduction rate is controlled below 85% and the temperature of the cold-rolled coil immediately after rolling is controlled at ≤105℃, the side leakage plating can be effectively avoided.

[0025] Example 3: Control of the process speed of aluminum zinc plating and the temperature of the plate in the open flame section. The experimental data are shown in Table 3. The products obtained from each group of experiments are as follows: Figure 2 shown.

[0026] Table 3 From the data in Table 3 and Figure 2 It can be seen that when the plate temperature in the open flame section is greater than or equal to 480℃ and less than or equal to 540℃, and the line speed of aluminum-zinc plating is greater than or equal to 150m / min, the side leakage plating can be effectively avoided.

[0027] Example 4: Ignition sequence of open flame section and plate temperature control. Our horizontal annealing furnace adopts a combination of open flame direct heating and radiation tube heating to anneal the steel plate. The open flame section has 4 zones, each with 8 side burners, and each zone is independently ignited. In order to solve the side leakage defect, we optimized the ignition sequence of the open flame section and the plate temperature process. The open flame section preferentially opens the last zone or the last two zones to facilitate the edge of the steel strip to quickly enter the radiation tube section at high temperature for reduction. The open flame section adopts high plate temperature process control. The experimental data are shown in Table 4. The products obtained from each group of experiments are as follows: Figure 3 shown.

[0028] Table 4 According to the experimental data in Table 4 and Figure 3 It can be seen that when the open flame section has the last zone or the last two zones opened and the plate temperature is greater than or equal to 480℃ and less than 540℃, the side leakage defect problem can be effectively improved.

[0029] Example 5: Controlling the hydrogen concentration of the horizontal annealing furnace. The experimental data are shown in Table 5. The products obtained from each group of experiments are as follows: Figure 4 shown.

[0030] Table 5 From Table 5 and Figure 4 It can be seen that the hydrogen concentration of the horizontal annealing furnace should be controlled at 25%-30%, which can effectively avoid side leakage plating.

[0031] Example 6: Controlling CO concentration to reduce the formation of carbon deposits on furnace rollers.

[0032] Take the product with a plate thickness of 0.8mm as an example; First experiment: CO concentration was 1.9%, and a lot of black edges leaked from both sides. According to SEM research results, the blackening was caused by carbon powder and ferrous oxide. The product and data are as follows: Figure 5 shown.

[0033] Second experiment: When the CO concentration was 0.6%, there was no black side leakage on both sides. The SEM research results showed that the content of all substances was within the normal range. The product and data are as follows: Figure 6 shown.

[0034] Example 7: The temperature of the radiation tube section is controlled between 550-600°C. The experimental data are shown in Table 6. The products obtained in each group of experiments are as follows: Figure 7 shown.

[0035] Table 6 From Table 6 and Figure 7 It can be seen that controlling the temperature of the radiation tube section between 550-600℃ can effectively avoid the side plating leakage.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A method for preventing G550 galvanized sheet from leaking plating on the side, characterized in that: The process time from pickling and trimming to galvanizing of steel coils is controlled within 3 days, and the sides of the steel coils are sprayed with rust remover before galvanizing. The cold rolling section needs to control the cold rolling reduction rate to reduce the plate temperature during the rolling process, thereby reducing the thickness of the oxide layer of the steel strip during the cold rolling process. The total cold rolling reduction rate is less than or equal to 85%, and the temperature of the cold rolled coil immediately off the line after rolling is less than or equal to 105°C; The aluminum zinc plating horizontal annealing furnace adopts side burner open flame heating, the open flame section is first opened in the last zone or the last two zones, the plate temperature in the open flame section is greater than or equal to 480℃ and less than or equal to 540℃, and the aluminum zinc plating line speed is ≥150m / min; The radiation tube section needs to control the plate temperature between 550-600℃ to ensure that the edge of the steel strip can be better restored in the radiation section after leaving the open flame section; Stop the circulating cooling fan in the cooling section of the horizontal annealing furnace, start the heater, and control the furnace temperature at 550°C; The temperature of the low temperature holding section, thermal tension chamber section and descending section of the horizontal annealing furnace must be controlled to be ≥550℃.

2. The method for preventing G550 galvanized sheet side leakage plating as claimed in claim 1, characterized in that: The rust remover is WD40 industrial rust remover.

3. The method for preventing G550 galvanized sheet side leakage plating as claimed in claim 1, characterized in that: The hydrogen concentration in the horizontal annealing furnace should be controlled at 25%-30%.

4. The method for preventing G550 galvanized sheet side leakage plating as claimed in claim 1, characterized in that: The furnace temperature of the open flame section is greater than or equal to 1200℃.

5. The method for preventing G550 galvanized sheet side leakage plating as claimed in claim 1, characterized in that: Control the CO concentration in the open flame section of the horizontal annealing furnace to reduce the formation of carbon deposits. The CO concentration control range is: When the G550 plate thickness is 0.20mm-0.60mm, the CO concentration is 0.5%-0.8%; When the G550 plate thickness is 0.61mm-1.50mm, the CO concentration is 0.6%-1.0%.

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