Method for eliminating tail scratch of thick hot-rolled strip steel coiling

Abstract

The invention discloses a method for eliminating tail scratches of thick-specification hot-rolled strip steel coiling, which comprises the following steps: in a hot rolling process, acquiring a target coiling temperature; and according to the obtained target coiling temperature, the temperature of the tail of the strip steel passing through a pinch roll of the hot rolling coiling machine is controlled, and the temperature of the tail of the strip steel is controlled to be higher than the target coiling temperature. According to the method for eliminating the tail scratch of the thick-specification hot-rolled strip steel coiling, the coiling temperature of the strip steel tail, the roll gap of the pinch roll, the pressure of the pinch roll and the pressure of the screw-down roll are controlled, the tail scratch of the thick-specification hot-rolled strip steel coiling can be effectively eliminated, equipment does not need to be transformed, and the method is simple and effective.

Description

Technical Field

[0001] The invention belongs to the technical field of hot-rolled strip steel production process, and in particular to a method for eliminating scratches on the coiling tail of a thick-gauge hot-rolled strip steel. Background Art

[0002] In the conventional hot rolling production process, the slab is descaled once after leaving the heating furnace to remove the surface oxide scale, and then rolled into an intermediate slab by the rough rolling unit, and then rolled into a strip by the seven-stand finishing rolling unit. After laminar cooling, the strip is guided by the upper and lower pinch rollers into a coiler drum, and then transported to the transport line by the unloading car and enters the finished product warehouse. The steel plate first passes through the pinch rollers and enters the coiler. The pinch rollers are composed of an upper pinch roller and a lower pinch roller. The center line of the lower pinch roller is in front, and the center line of the upper pinch roller is in the back. When the steel plate passes through the pinch rollers, the upper pinch roller exerts a certain pressure downward on the steel plate, and the steel plate is deformed to a certain extent, and enters the coiler along the lower guide plate, and then is pressed on the drum by the auxiliary coiling roller to be rolled into a steel coil. When rolling thick plates, the tail part of the steel plate will arch upward after passing through the pinch rollers, and then contact the bottom of the inclined groove after arching (see Figure 2 ), from which it can be concluded that the scratches are caused by contact friction here. When a steel plant produces 20mm and above specifications, 1-2 circles of scratches often appear at the tail of the steel coil, which directly causes quality disputes. In order to reduce the occurrence of quality disputes, the only way is to cut off 1-2 circles of the tail offline, which seriously affects the hot rolling yield and product quality. Therefore, it is urgent to solve this problem.

[0003] The Chinese patent with publication number CN115921543A discloses a method for controlling scratch defects on the surface of ultra-low carbon hot-rolled strip steel, which includes the following measures: increasing the sled coefficient of the head of rough rolling; increasing the reduction rate of the first two passes of rough rolling; adjusting the steel biting speed and rolling speed of the last two passes of rough rolling; reducing the reduction rate of the last two passes of rough rolling; and reducing the difference in the reduction amount of the last two passes of rough rolling. The control method of the present invention is simple and easy to operate, and improves the scratch defects in the production process of hot continuous rolling strip steel. However, the patent does not involve the problem of scratches at the tail of the coiling.

[0004] A Chinese patent with the publication number CN116765125A discloses a device and method for preventing hot-rolled strip from being scratched on the output roller table. The device for preventing hot-rolled strip from being scratched on the output roller table is arranged on a strip hot rolling mill, and the device includes: a plurality of Hall current transformers, a first temperature sensor, a second temperature sensor, and a control center. Among them, a Hall current transformer is arranged on the power transmission line of the motor corresponding to each roller table of the strip hot rolling mill. A first temperature sensor is installed on the bearing end of each motor. A second temperature sensor is installed on the bearing end of each roller table. The control center is electrically connected to the plurality of Hall current transformers, the plurality of first temperature sensors, and the second temperature sensors. This invention only relates to the scratching of the laminar roller table and cannot solve the problem of scratching at the tail of the thick-gauge coiling.

[0005] Through research on the scratching at the tail of thick-gauge strip, it is found that the thicker the target thickness of the strip, the lower the coiling temperature, the larger the gap of the pinch roll at the tail, and the greater the probability of scratching in the first 1-2 turns at the tail of the strip: the pressing force of the pinch roll is small and insufficient to provide enough pressing force to deform the steel plate; the pressing force of the compacting roll in front of the pinch roll is too large, resulting in a seesaw effect of the steel plate with the contact point of the pinch roll as the fulcrum, and the steel plate at the outlet is lifted and rubbed against the bottom of the chute. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a method for eliminating scratching at the tail of thick-gauge hot-rolled strip during coiling, aiming to eliminate scratching at the tail of thick-gauge hot-rolled strip during coiling.

[0007] To achieve the above object, the technical solution adopted by the present invention is: The method for eliminating scratching at the tail of thick-gauge hot-rolled strip during coiling includes:

[0008] During the hot rolling process, obtain the target coiling temperature;

[0009] According to the obtained target coiling temperature, control the temperature of the strip tail when passing through the pinch roll of the hot rolling coiler, and control the temperature of the strip tail to be higher than the target coiling temperature.

[0010] According to the difference of the target coiling temperature, control the temperature of the strip tail when passing through the pinch roll to be different. CT represents the target coiling temperature of the strip. If 650°C < CT ≤ 700°C, then control the temperature of the strip tail to be 30-50°C higher than the target coiling temperature, and the length of the strip tail is set to 3-5m.

[0011] According to different target coiling temperatures, control the temperature of the strip tail when passing through the pinch rolls differently. CT represents the target coiling temperature of the strip. If 600°C < CT ≤ 650°C, then control the temperature of the strip tail to be 50 - 100°C higher than the target coiling temperature, and the length of the strip tail is set to 5 - 8 m.

[0012] According to different target coiling temperatures, control the temperature of the strip tail when passing through the pinch rolls differently. CT represents the target coiling temperature of the strip. If CT ≤ 600°C, then control the temperature of the strip tail to be 100 - 150°C higher than the target coiling temperature, and the length of the strip tail is set to 8 - 10 m.

[0013] Set the roll gap of the pinch rolls according to the strip thickness. Specifically: the set value of the roll gap of the pinch rolls = H - (1 - 2.0) mm, where H is the strip thickness.

[0014] When the strip tail exits the finishing mill F7, set the coiling temperature to be higher than the target coiling temperature.

[0015] When the strip tail exits the finishing mill F7, adjust the water ratio of the upper and lower surface cooling water of the laminar cooling to increase the upper surface temperature.

[0016] According to different strip thicknesses and strengths, increase the pressure of the pinch rolls before the strip tail reaches the entrance of the coiling guide guard.

[0017] According to different strip thicknesses and strengths, reduce the pressure of the backup rolls before the strip tail reaches the entrance of the coiling guide guard.

[0018] The method for eliminating the scratches at the coiling tail of thick - gauge hot - rolled strips of the present invention can effectively eliminate the scratches at the coiling tail of thick - gauge hot - rolled strips by controlling the coiling temperature, the roll gap and the pressure of the pinch rolls of the strip tail, without the need to modify the equipment, which is simple and effective. Brief Description of the Drawings

[0019] This specification includes the following drawings, and the shown contents are respectively:

[0020] Figure 1 is the flow chart of the method for eliminating the scratches at the coiling tail of thick - gauge hot - rolled strips of the present invention;

[0021] Figure 2 is the schematic diagram of the scratch position of the strip;

[0022] In the figure, the markings are: 1, strip; 2, upper pinch roll; 3, lower pinch roll; 4, lower guide plate; 5, roller table; 6, friction part; 7, chute. Detailed Embodiments

[0023] The following will further describe the specific embodiments of the present invention in detail with reference to the accompanying drawings through the description of the embodiments, aiming to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention, and facilitate its implementation.

[0024] As Figure 1 shown, the present invention provides a method for eliminating scratches at the tail of a thick-gauge hot-rolled strip during coiling, including the following steps:

[0025] S1. During the hot-rolling process, obtain the target coiling temperature;

[0026] S2. According to the obtained target coiling temperature, control the temperature of the strip tail when passing through the pinch rolls of the hot-rolling coiler, and control the temperature of the strip tail to be higher than the target coiling temperature.

[0027] Specifically, in the present invention, the thickness H of the strip ≥ 20 mm. In the above step S2, the strip with a thickness ≥ 20 mm is conveyed to the mandrel through the pinch rolls of the coiler. According to different target coiling temperatures, the temperature of the strip tail when passing through the pinch rolls is controlled differently. CT represents the target coiling temperature of the strip. If 650 °C < CT ≤ 700 °C, then control the temperature of the strip tail to be 30 - 50 °C higher than the target coiling temperature, and the length of the strip tail is set to 3 - 5 m.

[0028] In the above step S2, according to different target coiling temperatures, the strip with a thickness ≥ 20 mm is conveyed to the mandrel through the pinch rolls of the coiler, and the temperature of the strip tail when passing through the pinch rolls is controlled differently. CT represents the target coiling temperature of the strip. If 600 °C < CT ≤ 650 °C, then control the temperature of the strip tail to be 50 - 100 °C higher than the target coiling temperature, and the length of the strip tail is set to 5 - 8 m.

[0029] In the above step S2, according to different target coiling temperatures, the strip with a thickness ≥ 20 mm is conveyed to the mandrel through the pinch rolls of the coiler, and the temperature of the strip tail when passing through the pinch rolls is controlled differently. CT represents the target coiling temperature of the strip. If CT ≤ 600 °C, then control the temperature of the strip tail to be 100 - 150 °C higher than the target coiling temperature, and the length of the strip tail is set to 8 - 10 m.

[0030] Set the roll gap of the pinch rolls according to the strip thickness, specifically: the set value of the roll gap of the pinch rolls = H - (1 - 2.0) mm, where H is the strip thickness.

[0031] Preferably, in the above step S2, when the strip tail exits the finishing mill F7, set the coiling temperature to be higher than the target coiling temperature.

[0032] Preferably, in the above step S2, when the strip tail exits the finishing mill F7, adjust the water ratio of the upper and lower tables of the laminar cooling to increase the upper table temperature.

[0033] Preferably, in the above step S2, according to different thicknesses and strengths of the strip, the pressure of the pinch roller is increased before the tail of the strip reaches the coiling guide entrance.

[0034] Preferably, in the above step S2, according to the different thicknesses and strengths of the strip, the pressure of the pressing roller is reduced before the tail of the strip reaches the coiling guide entrance.

[0035] Embodiment 1

[0036] In this embodiment, a strip steel with a thickness of 20 mm is produced, and the target coiling temperature is 650° C. The coiling process parameters are set as follows.

[0037] (1) The temperature of the tail of the strip is shown in the following table:

[0038]

[0039] (2) The water ratio of the upper and lower nozzles of the layer cooling is set as follows:

[0040] When the tail of the strip leaves the finishing mill F7, the ratio of upper water spray to lower water spray in laminar cooling is 0.85:1.

[0041] (3) The gap between the pinch rollers is set as follows:

[0042] When the tail of the strip reaches the entrance of the coiling guide, the gap between the pinch rollers is pressed down by 1mm.

[0043] (4) The pinch roller pressure is set as follows:

[0044] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller increases by 40Kn compared with the target value.

[0045] (5) The pressure of the pressing roller is set as follows:

[0046] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller is reduced by 20Kn compared with the target value.

[0047] (6) Implementation Effect

[0048] The scratch rate of the tail of thick hot-rolled strip is 0.

[0049] Embodiment 2

[0050] In this embodiment, a strip steel with a thickness of 22 mm is produced, and the target coiling temperature is 600° C. The coiling process parameters are set as follows.

[0051] (1) The temperature of the tail of the strip is shown in the following table:

[0052]

[0053] (2) The water ratio of the upper and lower nozzles of the layer cooling is set as follows:

[0054] When the tail of the strip is F7, the ratio of laminar upper spray and shock spray is 0.8:1.

[0055] (3) The pinch roller gap is set as follows:

[0056] When the tail of the strip reaches the entrance of the coiling guide, the gap between the pinch rollers is pressed down by 1.5mm.

[0057] (4) The pinch roller pressure is set as follows:

[0058] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller increases by 50Kn compared with the target value.

[0059] (5) The pressure of the pressing roller is set as follows:

[0060] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller is reduced by 20Kn compared with the target value.

[0061] (6) Implementation Effect

[0062] The scratch rate of the tail of thick hot-rolled strip is 0.

[0063] Embodiment 3

[0064] In this embodiment, a strip steel with a thickness of 22 mm is produced, and the target coiling temperature is 500° C. The coiling process parameters are set as follows.

[0065] (1) The temperature of the tail of the strip is shown in the following table:

[0066]

[0067] (2) The water ratio of the upper and lower nozzles of the layer cooling is set as follows:

[0068] When the tail of the strip is F7, the ratio of laminar upper spray and shock spray is 0.75:1.

[0069] (3) The pinch roller gap is set as follows:

[0070] When the tail of the strip reaches the entrance of the coiling guide, the gap between the pinch rollers is pressed down by 1.5mm.

[0071] (4) The pinch roller pressure is set as follows:

[0072] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller increases by 60Kn compared with the target value.

[0073] (5) The pressure of the pressing roller is set as follows:

[0074] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller is reduced by 20Kn compared with the target value.

[0075] (6) Implementation Effect

[0076] The scratch rate of the tail of thick hot-rolled strip is 0.

[0077] Embodiment 4

[0078] In this embodiment, a strip steel with a thickness of 24 mm is produced, and the target coiling temperature is 600° C. The coiling process parameters are set as follows.

[0079] (1) The temperature of the tail of the strip is shown in the following table:

[0080]

[0081] (2) The water ratio of the upper and lower nozzles of the layer cooling is set as follows:

[0082] When the tail of the strip is F7, the ratio of laminar upper spray and shock spray is 0.7:1.

[0083] (3) The gap between the pinch rollers is set as follows:

[0084] When the tail of the strip reaches the entrance of the coiling guide, the gap between the pinch rollers is pressed down by 1.5mm.

[0085] (4) The pinch roller pressure is set as follows:

[0086] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller increases by 60Kn compared with the target value.

[0087] (5) The pressure of the pressing roller is set as follows:

[0088] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller is reduced by 15Kn compared with the target value.

[0089] (6) Implementation Effect

[0090] The scratch rate of the tail of thick hot-rolled strip is 0.

[0091] Embodiment 5

[0092] In this embodiment, a strip steel with a thickness of 25 mm is produced, and the target coiling temperature is 500° C. The coiling process parameters are set as follows.

[0093] (1) The temperature of the tail of the strip is shown in the following table:

[0094]

[0095] (2) The water ratio of the upper and lower nozzles of the layer cooling is set as follows:

[0096] When the tail of the strip is F7, the ratio of laminar upper spray and shock spray is 0.65:1.

[0097] (3) The gap between the pinch rollers is set as follows:

[0098] When the tail of the strip reaches the entrance of the coiling guide, the gap between the pinch rollers is pressed down by 2.0 mm.

[0099] (4) The pinch roller pressure is set as follows:

[0100] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller increases by 60Kn compared with the target value.

[0101] (5) The pressure of the pressing roller is set as follows:

[0102] When the tail of the strip reaches the entrance of the coiling guide, the pressure of the pinch roller is reduced by 20Kn compared with the target value.

[0103] (6) Implementation Effect

[0104] The scratch rate of the tail of thick hot-rolled strip is 0.

[0105] The present invention is described above by way of example in conjunction with the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-mentioned methods. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the protection scope of the present invention.

Claims

1. A method for eliminating scratches on the coiling tail of thick hot-rolled strip, characterized in that: Including: During hot rolling, obtain the target coiling temperature; According to the obtained target coiling temperature, control the temperature of the strip tail when passing through the pinch rolls of the hot rolling coiler, and control the temperature of the strip tail to be higher than the target coiling temperature.

2. The method for eliminating scratches on the coiling tail of thick hot-rolled strip according to claim 1, characterized in that: According to the difference of the target coiling temperature, control the temperature of the strip tail when passing through the pinch rolls to be different. CT represents the target coiling temperature of the strip. If 650°C < CT ≤ 700°C, then control the temperature of the strip tail to be increased by 30 - 50°C compared with the target coiling temperature, and the length of the strip tail is set to 3 - 5 m.

3. The method for eliminating scratches on the coiling tail of thick hot-rolled strip according to claim 1, characterized in that: According to the difference of the target coiling temperature, control the temperature of the strip tail when passing through the pinch rolls to be different. CT represents the target coiling temperature of the strip. If 600°C < CT ≤ 650°C, then control the temperature of the strip tail to be increased by 50 - 100°C compared with the target coiling temperature, and the length of the strip tail is set to 5 - 8 m.

4. The method for eliminating scratches on the coiling tail of thick hot-rolled strip according to claim 1, characterized in that: According to the difference of the target coiling temperature, control the temperature of the strip tail when passing through the pinch rolls to be different. CT represents the target coiling temperature of the strip. If CT ≤ 600°C, then control the temperature of the strip tail to be increased by 100 - 150°C compared with the target coiling temperature, and the length of the strip tail is set to 8 - 10 m.

5. The method for eliminating scratches at the coiling tail of thick hot-rolled strip according to any one of claims 1 to 4, characterized in that: Set the roll gap of the pinch rolls according to the strip thickness. Specifically: the set value of the pinch roll gap = H - (1 - 2.0) mm, where H is the strip thickness.

6. The method for eliminating scratches at the coiling tail of thick hot-rolled strip according to any one of claims 1 to 5, characterized in that: When the strip tail exits the finishing mill F7, set the coiling temperature to be greater than the target coiling temperature.

7. The method for eliminating scratches at the coiling tail of thick hot-rolled strip according to any one of claims 1 to 6, characterized in that: When the strip tail exits the finishing mill F7, adjust the water ratio of the upper and lower tables of laminar cooling to increase the upper table temperature.

8. The method for eliminating scratches at the coiling tail of thick hot-rolled strip according to any one of claims 1 to 6, characterized in that: According to the different strip thicknesses and strengths, increase the pinch roll pressure before the strip tail reaches the coiling guide entrance.

9. The method for eliminating scratches at the coiling tail of thick hot-rolled strip according to any one of claims 1 to 6, characterized in that: According to the different strip thicknesses and strengths, reduce the pressure of the reduction rolls before the strip tail reaches the coiling guide entrance.

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