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What is the width control method for the rough rolling stage of packaging steel strip?
by：Hongmei
2021-03-15
What is the width control method for the rough rolling stage of packaging steel strip?
Answer: (1) Control of the difference between the actual width and the target width. The width of the finished product of the hot-rolled wide strip steel mill is completely controlled by the vertical rolling mill of the roughing mill, and is achieved by adjusting the side pressure of the vertical rolling mill. Width reduction (total lateral pressure) is calculated as follows:
The width tolerances of hot rolled strip steel are all positive deviations and no negative deviations. According to technical standards, the width tolerance is 0-25mm when the thickness is 1.2-12.7mm.
Wugang made statistics on the width tolerance, and found that the deviation of the average width of each roll minus the target width was less than 10mm, indicating that the vertical roll width control model has high accuracy.
The width change along the length of a steel coil is very small, and the width change of the head and tail can be controlled within 3mm.
The control accuracy of the difference between the actual width of the coil and the target depends on the accuracy of the width control model. The change in width along the direction of the steel's degree depends on the change in temperature and reduction along the length of the strip.
(2) The control of the width difference along the length of the strip. The width of the hot-rolled strip along the length direction is uneven. Generally, the width of the head and tail is narrower than the middle (the head and tail are not wide) and the width of the length except the head and tail is uneven. The head and tail loss occurs when the slab is heavily side-pressed. The metal at the head and tail ends of the slab does not extend uniformly, but slips along the direction of 45°, so that the head and tail lose width for a longer period of time. It is also difficult to correct in the process of control.
The width fluctuation along the length direction is generally due to the uneven original width of the slab, such as defect cleaning or the transition billet of continuous casting on-line width adjustment, etc. The temperature along the length direction is uneven, resulting in uneven width after rolling . Usually the temperature unevenness is caused by the black marks on the slide rail of the heating furnace, and accidents during the heating and rolling process sometimes also cause the temperature unevenness. At present, there are two methods to solve the above problems: one is to prevent the cause of uneven width, if the wide side pressure process is not used, if the wide side pressure process is used, a hydraulic short-stroke control system is required. The original uniform width of the slab adopts double-layer heat insulation, and the sliding rails are staggered and the walking heating furnace is arranged to make the temperature of the slab uniform along the length. The second is to correct the uneven width during the rolling process, and finally Make the strip width uniform. The specific method is:
1) The hydraulic short-stroke device control is mainly to avoid the head and tail loss of width when the slab is large laterally pressed. In order to avoid the head and tail loss of the slab when the side pressure is large, the side pressure of the vertical roll should be changed during the rolling fire and the tail section, that is, the pressure measurement of the head starts to be smaller, and the length of the head enters the rolling mill. Increasing the side pressure increases in phase until the side pressure is set in the middle section. The distance between the tail ends is reduced, and the amount of side pressure is also reduced. In this way, the vertical roll gap adjustment is carried out by an antilog function, and the slab head and tail correction are carried out by a linear function.
2) PWC continuous width control is mainly used to correct the width difference caused by the flame cleaning point and the watermark of the slide rail. The temperature at the point where the slab contacts the slide rail becomes lower. Although it reaches a uniform width after being pressed by the width side, the width will be uneven after horizontal rolling. In order to prevent this phenomenon, the side pressure is slightly larger at low temperature than at high temperature. The uneven width caused by flame cleaning has to be retained on the finished strip.
After being out of the furnace, the maximum values u200bu200bof the width and temperature of each section of the slab along the length direction will be stored in the computer. When the slab enters the vertical roll gap, it will operate according to the calculated value of the width and temperature of each section. The device must be equipped with slab actual tracking measuring rolls, photocells and a roll gap detector that uses logic to estimate rolling force signals.
3) AWC width automatic control, this function uses the rolling force change to correct the width difference. Using the principle of the horizontal rolling mill AGC, when the rolling force changes, the vertical roll gap will also change. AWC is to offset this change to ensure that the width fluctuation is within the required range.
Answer: (1) Control of the difference between the actual width and the target width. The width of the finished product of the hot-rolled wide strip steel mill is completely controlled by the vertical rolling mill of the roughing mill, and is achieved by adjusting the side pressure of the vertical rolling mill. Width reduction (total lateral pressure) is calculated as follows:
The width tolerances of hot rolled strip steel are all positive deviations and no negative deviations. According to technical standards, the width tolerance is 0-25mm when the thickness is 1.2-12.7mm.
Wugang made statistics on the width tolerance, and found that the deviation of the average width of each roll minus the target width was less than 10mm, indicating that the vertical roll width control model has high accuracy.
The width change along the length of a steel coil is very small, and the width change of the head and tail can be controlled within 3mm.
The control accuracy of the difference between the actual width of the coil and the target depends on the accuracy of the width control model. The change in width along the direction of the steel's degree depends on the change in temperature and reduction along the length of the strip.
(2) The control of the width difference along the length of the strip. The width of the hot-rolled strip along the length direction is uneven. Generally, the width of the head and tail is narrower than the middle (the head and tail are not wide) and the width of the length except the head and tail is uneven. The head and tail loss occurs when the slab is heavily side-pressed. The metal at the head and tail ends of the slab does not extend uniformly, but slips along the direction of 45°, so that the head and tail lose width for a longer period of time. It is also difficult to correct in the process of control.
The width fluctuation along the length direction is generally due to the uneven original width of the slab, such as defect cleaning or the transition billet of continuous casting on-line width adjustment, etc. The temperature along the length direction is uneven, resulting in uneven width after rolling . Usually the temperature unevenness is caused by the black marks on the slide rail of the heating furnace, and accidents during the heating and rolling process sometimes also cause the temperature unevenness. At present, there are two methods to solve the above problems: one is to prevent the cause of uneven width, if the wide side pressure process is not used, if the wide side pressure process is used, a hydraulic short-stroke control system is required. The original uniform width of the slab adopts double-layer heat insulation, and the sliding rails are staggered and the walking heating furnace is arranged to make the temperature of the slab uniform along the length. The second is to correct the uneven width during the rolling process, and finally Make the strip width uniform. The specific method is:
1) The hydraulic short-stroke device control is mainly to avoid the head and tail loss of width when the slab is large laterally pressed. In order to avoid the head and tail loss of the slab when the side pressure is large, the side pressure of the vertical roll should be changed during the rolling fire and the tail section, that is, the pressure measurement of the head starts to be smaller, and the length of the head enters the rolling mill. Increasing the side pressure increases in phase until the side pressure is set in the middle section. The distance between the tail ends is reduced, and the amount of side pressure is also reduced. In this way, the vertical roll gap adjustment is carried out by an antilog function, and the slab head and tail correction are carried out by a linear function.
2) PWC continuous width control is mainly used to correct the width difference caused by the flame cleaning point and the watermark of the slide rail. The temperature at the point where the slab contacts the slide rail becomes lower. Although it reaches a uniform width after being pressed by the width side, the width will be uneven after horizontal rolling. In order to prevent this phenomenon, the side pressure is slightly larger at low temperature than at high temperature. The uneven width caused by flame cleaning has to be retained on the finished strip.
After being out of the furnace, the maximum values u200bu200bof the width and temperature of each section of the slab along the length direction will be stored in the computer. When the slab enters the vertical roll gap, it will operate according to the calculated value of the width and temperature of each section. The device must be equipped with slab actual tracking measuring rolls, photocells and a roll gap detector that uses logic to estimate rolling force signals.
3) AWC width automatic control, this function uses the rolling force change to correct the width difference. Using the principle of the horizontal rolling mill AGC, when the rolling force changes, the vertical roll gap will also change. AWC is to offset this change to ensure that the width fluctuation is within the required range.
