Method for rapidly changing zinc pot straightening roller under abnormal conditions

Abstract

The invention relates to the technical field of zinc pot straightening roller changing, in particular to a zinc pot straightening roller quick changing method under abnormal conditions, which comprises the following steps: (1) when a zinc pot straightening roller is abnormal, a new straightening roller is placed in a preheating furnace to be preheated to T1 temperature, the preheating temperature rise rate is V1, and the heating time is t1; during preheating, the abnormal correction roller is hoisted out; (2) the new straightening roller preheated in the step (1) is subjected to heat preservation at the temperature T1, and the heat preservation time is t2; (3) the temperature of the new straightening roller after heat preservation is reduced to T2, the cooling rate is V2, and the cooling time is t3; and (4) the cooled new straightening roller is hoisted to the position above the zinc pot, the new straightening roller is lowered to the position below the liquid level of the zinc liquid and kept, then the new straightening roller is hoisted to the position above the liquid level of the zinc liquid and kept, the actions are repeated at least three times, and pre-installation is completed. According to the invention, the roller changing time of the straightening roller can be reduced to 3-4 hours, the production downtime is shortened, and the galvanization production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of roll changing of zinc pot leveling rolls, and particularly relates to a method for quickly changing zinc pot leveling rolls in case of abnormal situations. Background Art

[0002] The zinc pot leveling roll is a key equipment component in the continuous hot-dip galvanizing production line. Driven by hydraulic pressure or motor, it realizes fine adjustment of the roll body of the leveling roll in the horizontal and vertical directions, accurately controls the running track of the strip steel, and at the same time applies a reverse bending force to the strip steel to eliminate problems such as wavy edges and warping generated during rolling or transportation, and improves the flatness of the galvanized sheet.

[0003] During the continuous production of hot-dip galvanizing, the position adjustment and shape control of the zinc pot leveling roll before and after the strip steel (metal sheet) enters the zinc pot play a crucial role in ensuring the uniformity of the galvanized layer and the product quality.

[0004] However, during the zinc pot galvanizing production process, it is inevitable that some abnormal situations occur to the leveling roll, such as sudden failure of the leveling roll that requires emergency replacement, or shaft head fracture problem after the leveling roll is put into operation. In these abnormal situations, the traditional preheating and installation methods often take a long time, resulting in long-term shutdown of the production line and huge economic losses. Moreover, if the preheating is not sufficient and uniform, a large amount of zinc slag will be generated when the leveling roll enters the high-temperature zinc pot, resulting in poor quality of the roll surface. In addition, cracks may also occur due to excessive thermal stress, especially the ceramic strips of the bearing bush on the leveling roll are more likely to crack when encountering high-temperature zinc liquid, affecting its service life and the galvanizing quality of the strip steel.

[0005] In the above abnormal situation, it is necessary to replace the leveling roll. Generally, the operation of replacing the leveling roll includes the processes of preheating the leveling roll and its installation after preheating. For example, Patent CN 114000080 A discloses a method for preheating a zinc pot roll to improve the surface quality of hot-dip galvanized steel sheets, which includes the following steps: (1) Lift the zinc pot roll into the preheating box and heat it at a heating rate of 20°C / h to 40°C / h until it reaches 400°C, and keep it at 400°C for 1 h after the temperature reaches 400°C; (2) After keeping it at 400°C for 1 h, continue to heat the zinc pot roll from 400°C to 440°C at a heating rate of 20°C / h to 40°C / h, and then heat the zinc pot roll from 440°C to 460°C at a heating rate of 20°C / h to 30°C / h, and then keep it at 460°C for at least 3 h; (3) Conduct the operation of loading the zinc pot roll into the zinc pot within 1 h before the production line starts. The hoisting is completed within 0.5 h, and the production line starts within 0.5 h after the hoisting is completed. When replacing the leveling roll of the zinc pot in this patent, the heat loss in the air can be minimized as much as possible. The temperature difference between the zinc pot roll and the zinc liquid is very small, avoiding the precipitation of dross caused by the decrease in the temperature of the zinc liquid. This patent is a conventional method for replacing the leveling roll in the field, and its technical defect is that the zinc pot roll is preheated and kept at the process temperature for 16 h and then quickly replaced. The replacement time is relatively long, and the problem of rapid and uniform preheating and installation of the roll surface in a short time has not been solved. Summary of the Invention

[0006] Aiming at the technical problem that the replacement time of the existing zinc pot leveling roll is relatively long, resulting in too long production downtime and affecting production efficiency, the present invention provides a method for quickly replacing the zinc pot leveling roll in case of an abnormal situation, which can realize the quick replacement of the leveling roll in case of an abnormal situation, reduce the replacement time to 3 h to 4 h, shorten the production downtime, and improve the production efficiency of zinc pot galvanizing.

[0007] The technical solution of the present invention is as follows: The present invention provides a method for quickly replacing the zinc pot leveling roll in case of an abnormal situation, including the following steps: (1) When an abnormality occurs in the zinc pot leveling roll, place the new leveling roll in the preheating furnace and preheat it to temperature T1 at a preheating rate of V1 for a heating time of t1; while the new leveling roll is being preheated, lift out the leveling roll with the abnormality. (2) Keep the preheated new leveling roll at temperature T1 in step (1) for a holding time of t2. (3) Cool the new leveling roll after holding in step (2) to temperature T2 at a cooling rate of V2 for a cooling time of t3. (4) Lift the cooled new leveling roll above the zinc pot, lower the new leveling roll to a position below the zinc liquid level and hold it, and then lift the new leveling roll to a position above the zinc liquid level and hold it. Repeat the above actions at least three times to complete the pre-installation. (5) Install the newly pre - installed correction roll onto the zinc pot officially.

[0008] It should be further noted that in step (1), the abnormal conditions of the correction roll include fracture, bruise, coating peeling off, or surface roughness decrease.

[0009] It should be further noted that in step (1), the new correction roll is pre - heated in the pre - heating furnace to T1 = 480 °C, the pre - heating temperature - rising rate V1 ≥ 240 °C / h, and the heating time t1 ≤ 2 h. Further, place a new correction roll in the pre - heating furnace to ensure a relatively large temperature - rising rate. While heating, remove the correction roll with abnormal conditions in the zinc pot, lift it off the zinc pot, and place it on the roll stand. Under the condition of new roll replacement, reduce the time for installing the new roll and then lifting off the old roll.

[0010] It should be further noted that in step (1), the new correction roll is pre - heated in the pre - heating furnace to T1 = 480 °C, the pre - heating temperature - rising rate V1 = 240 °C / h, and the heating time t1 = 2 h. Under the above temperature - rising rate and heating time, it can not only ensure a relatively fast heating speed but also ensure the rapid and uniform roll replacement temperature of the correction roll, avoiding problems such as roll surface slag formation during roll replacement.

[0011] It should be further noted that in step (2), the heat - preservation time t2 of the pre - heated new correction roll is t2 ≤ 0.5 h.

[0012] It should be further noted that in step (2), the heat - preservation time t2 of the pre - heated new correction roll is t2 = 0.5 h. Under this heat - preservation time, the correction roll can be further heated evenly, avoiding uneven heating of the local roll body due to rapid heating of the correction roll.

[0013] It should be further noted that in step (3), the temperature of the heat - preserved new correction roll is reduced to T2 = 460 °C, the temperature - reducing rate is V2 ≥ 40 °C, and the temperature - reducing time is t3 ≤ 0.5 h.

[0014] It should be further noted that in step (3), the temperature of the heat - preserved new correction roll is reduced to T2 = 460 °C, the temperature - reducing rate is V2 = 40 °C, and the temperature - reducing time is t3 = 0.5 h.

[0015] It should be further noted that in step (4), the new correction roll is lowered to a position below the zinc liquid level and held for 10 s, and then the new correction roll is lifted to a position above the zinc liquid level and held for 10 s.

[0016] It should be further noted that as an optimal technical solution, the method for rapid roll replacement of the zinc - pot correction roll in case of abnormal conditions provided by the present invention specifically includes the following steps: (1)When the zinc pot leveling roll malfunctions, place the new leveling roll in the preheating furnace and preheat it to 480 °C at a preheating rate of 240 °C / h for 2 h; while the new leveling roll is being preheated, lift out the malfunctioning leveling roll. (2)In step (1), the preheated new leveling roll is insulated at 480 °C for 0.5 h. (3)In step (2), after insulation, the new leveling roll is cooled to 460 °C at a cooling rate of 40 °C for 0.5 h. (4)In step (3), after cooling, the new leveling roll is lifted above the zinc pot, lowered to a position below the zinc liquid level and held, then lifted above the zinc liquid level and held. Repeat the above actions five times to complete the pre-installation. (5)The pre-installed new leveling roll is officially installed in the zinc pot.

[0017] The beneficial effects of the present invention are as follows: (1)The method for quickly replacing the zinc pot leveling roll in case of an anomaly provided by the present invention can reduce the roll replacement time to 3 h - 4 h, solve the technical problem in the prior art that the preheating and installation of the leveling roll take a long time in case of an anomaly, affect the production efficiency, and improve the economic benefits of the unit.

[0018] (2)The method for quickly replacing the zinc pot leveling roll in case of an anomaly provided by the present invention, through "linear heating + dynamic cooling + progressive pre-installation", eliminates the residual thermal stress inside the roll body by rapid heating and insulation, reduces thermal stress damage. After cooling, it can avoid a large amount of zinc slag accumulating on the roll surface due to a large temperature difference between the zinc liquid and the installed leveling roll, causing damage to the roll surface. At the same time, the present invention adopts a progressive pre-installation method of moving the leveling roll up and down the galvanized liquid level, which can form a gradient temperature layer on the surface of the leveling roll, making it adapt to the high-temperature environment of the zinc pot and reducing the risk of microcracks on the surface of the leveling roll bearing bush caused by sudden heating. Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0020] Figure 1 It is the heating and heat treatment curve graph of the zinc pot leveling roll in the specific embodiment of the present invention. Specific Embodiments

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] A method for quickly replacing the zinc pot leveling roll in case of abnormality includes the following steps: (1) When the zinc pot leveling roll is abnormal, place the new leveling roll in the preheating furnace and preheat it to the temperature T1 at a preheating heating rate of V1 for a heating time of t1; while the new leveling roll is being preheated, lift out the abnormal leveling roll. (2) The preheated new leveling roll in step (1) is kept at the temperature T1 for a holding time of t2. (3) The new leveling roll after holding in step (2) is cooled to the temperature T2 at a cooling rate of V2 for a cooling time of t3. (4) The new leveling roll after cooling in step (3) is lifted above the zinc pot, lowered to a position below the zinc liquid level and held, and then lifted to a position above the zinc liquid level and held. Repeat the above actions at least three times to complete the pre-installation. (5) Install the pre-installed new leveling roll into the zinc pot officially.

[0023] As a preferred embodiment of the present invention, in step (1), the abnormal conditions of the leveling roll include fracture, bruise, coating peeling or surface roughness reduction. The present invention is applicable to several abnormal conditions of the above leveling roll. In these abnormal conditions, the traditional preheating and installation methods often take a long time, resulting in long-term shutdown of the production line and huge economic losses.

[0024] As a preferred embodiment of the present invention, in step (1), the new leveling roll is preheated in the preheating furnace to T1 = 480 °C, the preheating heating rate V1 ≥ 240 °C / h, and the heating time t1 ≤ 2 h. Further, place a new leveling roll in the preheating furnace to ensure a relatively large heating rate. While heating, remove the abnormal leveling roll in the zinc pot, lift it off the zinc pot, and place it on the roll stand. To meet the roll replacement conditions for the new roll, reduce the time for installing the new roll and then lifting off the old roll.

[0025] As a preferred embodiment of the present invention, in step (1), the new straightening roll is preheated in a preheating furnace to T1 = 480 °C, with a preheating heating rate V1 = 240 °C / h and a heating time t1 = 2 h. At the above heating rate and heating time, it can not only ensure a relatively fast heating speed but also ensure a rapid and uniform roll-changing temperature of the straightening roll, avoiding problems such as slag formation on the roll surface during roll change.

[0026] As a preferred embodiment of the present invention, in step (2), the holding time t2 of the preheated new straightening roll is t2 ≤ 0.5 h.

[0027] As a preferred embodiment of the present invention, in step (2), the holding time t2 of the preheated new straightening roll is t2 = 0.5 h. At this holding time, the straightening roll can be further heated evenly, avoiding uneven heating of the local roll body of the straightening roll during rapid heating.

[0028] As a preferred embodiment of the present invention, in step (3), the preheated new straightening roll is cooled to T2 = 460 °C, with a cooling rate V2 ≥ 40 °C and a cooling time t3 ≤ 0.5 h.

[0029] As a preferred embodiment of the present invention, in step (3), the preheated new straightening roll is cooled to T2 = 460 °C, with a cooling rate V2 = 40 °C and a cooling time t3 = 0.5 h. When cooling the straightening roll at this cooling rate, a large amount of zinc slag can be avoided from aggregating on the roll surface due to a large temperature difference between the straightening roll and the zinc liquid during installation, causing damage to the roll surface.

[0030] As a preferred embodiment of the present invention, in step (4), the new straightening roll is lowered to a position below the zinc liquid level and held for 10 s, and then the new straightening roll is lifted to a position above the zinc liquid level and held for 10 s. By adopting a progressive pre-installation method in which the straightening roll moves up and down the galvanizing liquid level, a gradient temperature layer can be formed on the surface of the straightening roll, enabling it to adapt to the high-temperature environment of the zinc pot and reducing the risk of micro-cracks on the roll surface caused by sudden heating.

[0031] The present invention relates to a method for changing the straightening roll of a zinc pot in the case of abnormal conditions such as fracture, collision damage, coating peeling, and a significant reduction in roughness of the straightening roll. The core of the method of the present invention is to establish a heating and heat treatment curve for the zinc pot straightening roll (combined with Figure 1 ), ensuring that the straightening roll quickly and evenly reaches the process roll-changing temperature, avoiding problems such as slag formation on the roll surface during roll change, and optimizing the roll-changing method of the straightening roll to avoid problems such as cracks generated by the release of thermal stress when the ceramic strip of the bearing bush of the straightening roll enters the zinc liquid during installation, thereby realizing rapid and efficient roll change.

[0032] Example 1 At 7 o'clock on December 5, 2023, during the galvanizing production process of a zinc pot in a steel plant, the head of the straightening roller shaft broke, seriously affecting the product quality. It was necessary to stop the machine for replacement, and the roll-changing method of the present invention was used for roll changing.

[0033] A rapid roll-changing method for the straightening roller of a zinc pot in case of abnormality, comprising the following steps: (1) When the head of the straightening roller of the zinc pot breaks, place the new straightening roller in the preheating furnace for preheating. The preheating heating rate is 240 °C / h, and the heating time is 2 h. At 9 o'clock on the same day, the straightening roller is heated to 480 °C; while the new straightening roller is being preheated, remove the roller stand of the abnormal straightening roller and lift and remove the old roller. (2) The preheated new straightening roller in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h. (3) The new straightening roller after heat preservation in step (2) is cooled, the cooling rate is 40 °C, and the cooling time is 0.5 h. At 10 o'clock on the same day, the temperature is cooled to 460 °C. (4) Lift the cooled new straightening roller in step (3) above the zinc pot, lower the new straightening roller to a position below the zinc liquid level and keep it for 10 s, then lift the new straightening roller to a position above the zinc liquid level and keep it for 10 s. Repeat the above actions five times to complete the pre-installation. (5) Officially install the pre-installed new straightening roller into the zinc pot. After the installation is completed, restart the machine, and the restart time is 10:20 on the same day.

[0034] Example 2 At 13 o'clock on March 6, 2024, during the production of 2.5 mm × 1600 mm strip steel in the zinc pot galvanizing process of a steel plant, scratches appeared on the lower surface of the strip steel, accompanied by non-galvanizing. It was judged that the coating of the straightening roller fell off, seriously affecting the product quality. It was necessary to stop the machine for replacement, and the roll-changing method of the present invention was used for roll changing.

[0035] A rapid roll-changing method for the straightening roller of a zinc pot in case of abnormality, comprising the following steps: (1) When the quality of the strip steel is affected by the quality of the straightening roller, place the new straightening roller in the preheating furnace for preheating. The preheating heating rate is 240 °C / h, and the heating time is 2 h. At 15 o'clock on the same day, the straightening roller is heated to 480 °C; while the new straightening roller is being preheated, remove the roller stand of the abnormal straightening roller and lift and remove the old roller. (2) The preheated new straightening roller in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h. (3) The new straightening roller after heat preservation in step (2) is cooled, the cooling rate is 40 °C, and the cooling time is 0.5 h. At 16 o'clock on the same day, the temperature is cooled to 460 °C. (4) The newly corrected roller after cooling in step (3) is lifted above the zinc pot, the newly corrected roller is lowered to a position below the zinc liquid level and maintained for 10 s, then the newly corrected roller is lifted to a position above the zinc liquid level and maintained for 10 s. Repeat the above actions seven times to complete the pre-installation; (5) The newly corrected roller after pre-installation is officially installed in the zinc pot. After installation, the vehicle starts again, and the starting time is 16:30 on the same day.

[0036] Comparative Example 1 For the same abnormal conditions of the corrected roller in Comparative Example 1 and Example 1, both are the fracture of the corrected roller shaft head, which affects the product quality and requires the replacement of the corrected roller. In Comparative Example 1, the operation of replacing the corrected roller is required.

[0037] Comparative Example 1 uses a preheating method for zinc pot rollers to improve the surface quality of hot-dip galvanized steel sheets disclosed in Patent CN 114000080 A for preheating and replacement. The corrected roller is heated stepwise to 460 °C in 13 h and then kept warm for 3 h, and then the corrected roller is installed in the zinc pot and the vehicle starts again within 10 min.

[0038] Comparative Example 2 For the same abnormal conditions of the corrected roller in Comparative Example 2 and Example 1, both are the fracture of the corrected roller shaft head, which affects the product quality and requires the replacement of the corrected roller. In Comparative Example 2, the operation of replacing the corrected roller is required.

[0039] A method for quickly replacing the zinc pot corrected roller in case of abnormality includes the following steps: (1) When the shaft head of the zinc pot corrected roller breaks, the newly corrected roller is placed in the preheating furnace for preheating. The preheating heating rate is 160 °C / h, the heating time is 3 h, and the corrected roller is heated to 480 °C; while the newly corrected roller is being preheated, the roller stand of the abnormal corrected roller is removed, and the old roller is lifted and removed; (2) The newly corrected roller after preheating in step (1) is kept warm at 480 °C, and the holding time is 0.5 h; (3) The newly corrected roller after holding in step (2) is cooled, the cooling rate is 40 °C, the cooling time is 0.5 h, and the temperature is cooled to 460 °C; (4) The newly corrected roller after cooling in step (3) is lifted above the zinc pot, the newly corrected roller is lowered to a position below the zinc liquid level and maintained for 10 s, then the newly corrected roller is lifted to a position above the zinc liquid level and maintained for 10 s. Repeat the above actions five times to complete the pre-installation; (5) The newly corrected roller after pre-installation is officially installed in the zinc pot. After installation, the vehicle starts again.

[0040] Comparative Example 3 Comparative Example 3 has the same abnormal situation of the leveling roll as Example 2. During the production of 2.5 mm × 1600 mm strip steel in the galvanizing pot, scratches and missing plating occurred on the lower surface of the strip steel. It was determined that the coating of the leveling roll had peeled off, seriously affecting the product quality and requiring a shutdown for replacement.

[0041] A method for quickly replacing the leveling roll in a galvanizing pot under abnormal conditions includes the following steps: (1) When the quality of the strip steel is affected by the quality of the leveling roll, place the new leveling roll in a preheating furnace for preheating. The preheating heating rate is 260 °C / h, the heating time is 2 h, and the leveling roll is heated to 520 °C. While the new leveling roll is being preheated, remove the roll stand of the abnormal leveling roll and lift and remove the old roll. (2) The preheated new leveling roll in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h. (3) The new leveling roll after heat preservation in step (2) is cooled down, the cooling rate is 40 °C, the cooling time is 0.5 h, and the temperature is cooled down to 460 °C. (4) The new leveling roll after cooling in step (3) is lifted above the galvanizing pot, lowered to a position below the zinc liquid level and kept for 10 s, then lifted to a position above the zinc liquid level and kept for 10 s. Repeat the above actions seven times to complete the pre-installation. (5) Install the pre-installed new leveling roll into the galvanizing pot formally, and resume starting the machine after installation.

[0042] Comparative Example 4 Comparative Example 4 has the same abnormal situation of the leveling roll as Example 1, that is, the shaft head of the leveling roll is broken, affecting the product quality and requiring replacement of the leveling roll. Comparative Example 4 needs to perform a roll replacement operation on the leveling roll.

[0043] A method for quickly replacing the leveling roll in a galvanizing pot under abnormal conditions includes the following steps: (1) When the shaft head of the leveling roll in the galvanizing pot is broken, place the new leveling roll in a preheating furnace for preheating. The preheating heating rate is 240 °C / h, the heating time is 2 h, and the leveling roll is heated to 480 °C. While the new leveling roll is being preheated, remove the roll stand of the abnormal leveling roll and lift and remove the old roll. (2) The preheated new leveling roll in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 1.0 h. (3) The new leveling roll after heat preservation in step (2) is cooled down, the cooling rate is 40 °C, the cooling time is 0.5 h, and the temperature is cooled down to 460 °C. (4) The new leveling roll after cooling in step (3) is lifted above the galvanizing pot, lowered to a position below the zinc liquid level and kept for 10 s, then lifted to a position above the zinc liquid level and kept for 10 s. Repeat the above actions five times to complete the pre-installation. (5) Install the newly pre-installed correction roll into the zinc pot formally, and resume starting the machine after installation is completed.

[0044] Comparative Example 5 Comparative Example 5 has the same abnormal situation of the correction roll as Example 1, that is, the shaft head of the correction roll is broken, which affects the product quality and requires replacement of the correction roll. Comparative Example 5 needs to perform the roll change operation on the correction roll.

[0045] A method for quickly replacing the zinc pot correction roll under abnormal conditions includes the following steps: (1) When the shaft head of the zinc pot correction roll is broken, place the new correction roll in the preheating furnace for preheating. The preheating heating rate is 240 °C / h, the heating time is 2 h, and the correction roll is heated to 480 °C; while the new correction roll is being preheated, remove the roll stand of the abnormal correction roll and lift and remove the old roll. (2) The preheated new correction roll in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h. (3) The new correction roll after heat preservation in step (2) is cooled down, the cooling rate is 20 °C, the cooling time is 1.0 h, and the temperature is cooled down to 460 °C. (4) The new correction roll after cooling in step (3) is lifted above the zinc pot, the new correction roll is lowered to a position below the zinc liquid level and kept for 10 s, and then the new correction roll is lifted to a position above the zinc liquid level and kept for 10 s. Repeat the above actions five times to complete the pre-installation. (5) Install the newly pre-installed correction roll into the zinc pot formally, and resume starting the machine after installation is completed.

[0046] Comparative Example 6 Comparative Example 6 has the same abnormal situation of the correction roll as Example 1, that is, the shaft head of the correction roll is broken, which affects the product quality and requires replacement of the correction roll. Comparative Example 6 needs to perform the roll change operation on the correction roll.

[0047] A method for quickly replacing the zinc pot correction roll under abnormal conditions includes the following steps: (1) When the shaft head of the zinc pot correction roll is broken, place the new correction roll in the preheating furnace for preheating. The preheating heating rate is 240 °C / h, the heating time is 2 h, and the correction roll is heated to 480 °C; while the new correction roll is being preheated, remove the roll stand of the abnormal correction roll and lift and remove the old roll. (2) The preheated new correction roll in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h. (3) The new correction roll after heat preservation in step (2) is cooled down, the cooling rate is 40 °C, the cooling time is 0.5 h, and the temperature is cooled down to 460 °C. (4)The new straightening roll after cooling in step (3) is hoisted above the zinc pot, and the new straightening roll is lowered below the zinc liquid level to complete the pre-installation; (5)The new straightening roll after pre-installation is officially installed in the zinc pot, and the vehicle is restarted after the installation is completed.

[0048] The straightening rolls after roll change in Examples 1-2 and Comparative Examples 1-6 of the present invention were tested on the machine. The test method was to resume the lowest process speed after going online, and count the number of zinc drosses with a size of more than 0.5 mm on the surface of a specific area of the strip. At the same time, the roll change time, output, and economic benefits of Examples 1-2 and Comparative Examples 1-6 of the present invention were counted, and the results are shown in Table 1.

[0049] Table 1 Statistical data of roll change time, roll change quality, and economic benefits of examples and comparative examples

[0050] As can be seen from Table 1, the roll change method provided in Examples 1-2 of the present invention has the best technical effects in terms of roll change time, number of zinc drosses, microcrack rate on the surface of the bearing bush, and economic benefits.

[0051] At the same time, as can also be seen from Table 1, changing the preheating heating conditions in step (1) (Comparative Examples 2 and 3) can increase the number of zinc drosses on the surface of the strip, and changing the pre-installation conditions in step (4) (Comparative Examples 1 and 6) can increase the microcrack rate on the surface of the bearing bush.

[0052] Example 3 Example 3 has the same abnormal situation of the straightening roll as Example 2. During the production of 2.5 mm × 1600 mm strip by zinc pot galvanizing, scratch marks appeared on the lower surface of the strip, accompanied by missing plating. It was judged that the coating of the straightening roll had peeled off, and the product quality was seriously affected, and it was necessary to stop the machine for roll change.

[0053] A method for quickly changing the straightening roll of a zinc pot in case of an abnormality, comprising the following steps: (1)When the quality of the strip is affected by the quality of the straightening roll, the new straightening roll is placed in a preheating furnace for preheating. The preheating heating rate is 280 °C / h, the heating time is 1.7 h, and the straightening roll is heated to 480 °C; while the new straightening roll is being preheated, the roll stand of the abnormal straightening roll is removed, and the old roll is hoisted and removed; (2)The new straightening roll after preheating in step (1) is kept at 480 °C for heat preservation, and the heat preservation time is 0.5 h; (3)The new straightening roll after heat preservation in step (2) is cooled, the cooling rate is 40 °C, the cooling time is 0.5 h, and the temperature is cooled to 460 °C; (4) The new straightening roll after cooling in step (3) is hoisted above the zinc pot, the new straightening roll is lowered to a position below the zinc liquid level and kept for 10 s, then the new straightening roll is hoisted to a position above the zinc liquid level and kept for 10 s, and the above actions are repeated seven times to complete the pre-installation; (5) The new straightening roll after pre-installation is formally installed into the zinc pot, and the vehicle is restarted after the installation is completed.

[0054] Example 4 Example 4 has the same abnormal situation of the straightening roll as Example 1, that is, the shaft head of the straightening roll is broken, which affects the product quality and requires replacement of the straightening roll. The roll change operation needs to be carried out on the straightening roll.

[0055] A method for quickly changing the straightening roll of a zinc pot in case of abnormality includes the following steps: (1) When the shaft head of the zinc pot straightening roll is broken, the new straightening roll is placed in the preheating furnace for preheating. The preheating temperature rising rate is 160 °C / h, the heating time is 3 h, and the straightening roll is heated to 480 °C; while the new straightening roll is being preheated, the roll stand of the abnormal straightening roll is removed, and the old roll is hoisted away and taken out; (2) The preheated new straightening roll in step (1) is kept at 480 °C for 0.3 h; (3) The new straightening roll after heat preservation in step (2) is cooled, the cooling rate is 60 °C, the cooling time is 0.33 h, and the temperature is cooled to 460 °C; (4) The new straightening roll after cooling in step (3) is hoisted above the zinc pot, the new straightening roll is lowered to a position below the zinc liquid level and kept for 10 s, then the new straightening roll is hoisted to a position above the zinc liquid level and kept for 10 s, and the above actions are repeated five times to complete the pre-installation; (5) The new straightening roll after pre-installation is formally installed into the zinc pot, and the vehicle is restarted after the installation is completed.

[0056] Example 5 In Example 5, the surface coating of the straightening roll falls off, which affects the product quality and requires replacement of the straightening roll. The roll change operation needs to be carried out on the straightening roll.

[0057] A method for quickly changing the straightening roll of a zinc pot in case of abnormality includes the following steps: (1) When the surface coating of the zinc pot straightening roll falls off, the new straightening roll is placed in the preheating furnace for preheating. The preheating temperature rising rate is 240 °C / h, the heating time is 2 h, and the straightening roll is heated to 480 °C; while the new straightening roll is being preheated, the roll stand of the abnormal straightening roll is removed, and the old roll is hoisted away and taken out; (2) The preheated new straightening roll in step (1) is kept at 480 °C for 0.4 h; (3) The newly straightened roller after heat preservation in step (2) is cooled at a cooling rate of 50 °C for a cooling time of 0.40 h until it reaches 460 °C. (4) The newly straightened roller after cooling in step (3) is hoisted above the zinc pot, lowered to a position below the zinc liquid level and held for 10 s, then hoisted above the zinc liquid level and held for 10 s. The above actions are repeated four times to complete the pre-installation. (5) The newly straightened roller after pre-installation is officially installed into the zinc pot, and after installation, the vehicle starts again.

[0058] In the method of the present invention, for the purpose of illustration rather than limitation, specific details such as specific system structures and technologies are proposed to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details.

[0059] In the method of the present invention, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0060] Although the present invention has been described in detail by referring to the drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person familiar with the technical field of the present invention can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all should be covered within the protection scope of the present invention.

Claims

1. A method for quickly replacing the leveling rolls of a zinc pot in case of abnormal situations, characterized in that, It includes the following steps: (1) When the zinc pot leveling roll is abnormal, place the new leveling roll in the preheating furnace and preheat it to temperature T1 at a preheating rate of V1 for a heating time of t1; while the new leveling roll is being preheated, lift out the abnormal leveling roll; (2) Keep the preheated new leveling roll at temperature T1 for a holding time of t2 in step (1); (3) Cool the new leveling roll after holding in step (2) to temperature T2 at a cooling rate of V2 for a cooling time of t3; (4) Lift the cooled new leveling roll in step (3) above the zinc pot, lower the new leveling roll to a position below the zinc liquid level and hold it, then lift the new leveling roll to a position above the zinc liquid level and hold it, repeat the above actions at least three times to complete pre-installation; (5) Officially install the pre-installed new leveling roll into the zinc pot.

2. The method for quickly replacing the leveling roll of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (1), the abnormal conditions of the leveling roll include fracture, bruise, coating peeling, or surface roughness decrease.

3. The method for quickly replacing the leveling roll of the zinc pot in case of abnormal conditions according to claim 1, wherein, In step (1), the new leveling roll is preheated in the preheating furnace to T1 = 480 °C, the preheating rate V1 ≥ 240 °C / h, and the heating time t1 ≤ 2 h.

4. The method for quickly replacing the leveling roll of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (1), the new leveling roll is preheated in the preheating furnace to T1 = 480 °C, the preheating rate V1 = 240 °C / h, and the heating time t1 = 2 h.

5. The method for quickly replacing the leveling roll of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (2), the holding time t2 of the preheated new leveling roll ≤ 0.5 h.

6. The method for quickly replacing the leveling rolls of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (2), the holding time t2 of the preheated new leveling roll = 0.5 h.

7. The method for quickly replacing the leveling rolls of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (3), the new leveling roll after holding is cooled to T2 = 460 °C, the cooling rate is V2 ≥ 40 °C, and the cooling time is t3 ≤ 0.5 h.

8. The method for quickly replacing the leveling roll of the zinc pot in case of abnormal conditions as described in claim 1, characterized in that, In step (3), the new leveling roll after holding is cooled to T2 = 460 °C, the cooling rate is V2 = 40 °C, and the cooling time is t3 = 0.5 h.

9. The method for quickly replacing the zinc pot leveling roll under abnormal conditions according to claim 1, characterized in that In step (4), lower the new leveling roll to a position below the zinc liquid level and hold it for 10 s, then lift the new leveling roll to a position above the zinc liquid level and hold it for 10 s.

10. The method for quickly replacing the leveling roll of the zinc pot in case of abnormality as claimed in claim 1, wherein, Specifically, it includes the following steps: (1) When the zinc pot leveling roll is abnormal, place the new leveling roll in the preheating furnace and preheat it to 480 °C at a preheating rate of 240 °C / h for a heating time of 2 h; while the new leveling roll is being preheated, lift out the abnormal leveling roll; (2) Keep the preheated new leveling roll at 480 °C for a holding time of 0.5 h in step (1); (3) Cool the new leveling roll after holding in step (2) to 460 °C at a cooling rate of 40 °C for a cooling time of 0.5 h; (4) Lift the cooled new leveling roll in step (3) above the zinc pot, lower the new leveling roll to a position below the zinc liquid level and hold it, then lift the new leveling roll to a position above the zinc liquid level and hold it, repeat the above actions five times to complete pre-installation; (5) Officially install the pre-installed new leveling roll into the zinc pot.

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