Answers to possible problems in steel rolling

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Answers to possible problems in steel rolling

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This paper mainly describes the answers to possible problems in steel rolling

Keyword：

work roll, middle rollers, rolling line, cold rolled, unilateral waves, middle wave, small side wave

Realed product：

Rolling mill rolls

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1. Why do you need to pre-press each time you change the roll?

Because the pre-compression has a memory function, for example, the work roll has a diameter of 300, and the roll gap is 20 cm when the pre-compression is completed. When the roll is changed, the new roll diameter is 290. Because the pre-pressing is against the memory of the working roll with a diameter of 300, after changing the 290 diameter roll, the roll gap is 30 cm, but the roll gap is displayed as 20 centimeter. The roll gap display is not accurate, so it must be pre-pressed. It is not necessary to do pre-pressing when the roll diameter is the same.

2. How to calculate the elevation of the rolling line?

Rolling line elevation calculation method (upper support roll maximum diameter-upper support roll actual roll diameter) / 2 + (upper middle roll maximum roll diameter-upper middle roll actual roll diameter) + (upper work roll maximum roll diameter-upper work Actual roll diameter) + original value = actual value of rolling line elevation

3. How to calculate the horizontal movement of the upper and lower middle rollers? 

(Length of intermediate roll-width of strip-chamfer length of intermediate roll) / 2 = number of intermediate rolls traversed

4. What are the main shape defects of cold rolled strip steel during rolling?

The main steel plate defects in the rolling strip are (single-side wave, two-side wave, middle wave, two small side waves, single-side small side wave, two-rib wave and single-rib wave)

5. Under what circumstances are unilateral waves appearing? How to control unilateral waves?

• The roll gap is not accurate. The rolling force on the two sides is different, and unilateral waves are prone to appear on the side with greater force. Control method: adjust the roll gap to adjust the deviation, find the roll gap difference.
• Unilateral waves are also prone to appear in places with wrong rolls and deviations. Control method: timely adjust roll gap adjustment according to strip deviation or wrong coil position.

6. Under what circumstances are there waves on both sides? How to control unilateral waves?

• When the bending force of the work roll is small, it is easy to have waves on both sides. Control method: Increase the bending force of the work roll.
• Two-sided waves are prone to appear when the head and tail rolling force is large. Control method: increase the bending force. The bending force is not enough when necessary. Increase the tension to cancel the thickness monitoring, and manually adjust the rolling force within the range of sufficient bending force.

7. Under what circumstances will there be a middle wave? How to control the middle wave?

• Intermediate waves are prone to appear when the work roll is large. Control method: reduce the bending force of the work roll.
• Intermediate waves are prone to appear when the rolling force is small. Control method: reduce the bending force. When the bending force is reduced to zero, there are still intermediate waves. Reduce the tension of the roll to help. The rolling force is relatively large. It can also control the middle waves.

8. Under what circumstances are there small waves on both sides? How to control small side waves?

• When rolling thin materials, the strip steel is prone to two-sided waves after work hardening. Because of the high rolling force in the case of work hardening of the rolled thin material, the stress that the roll bears has reached the limit. The roll is deformed into a concave shape, and the two sides of the roll touch together, the edge of the strip is thinned, and there are waves on both sides. Control method: Increase the bending force of the work roll. Adjust the amount of process deformation.
• The low hardness of the roll is also prone to small waves on both sides when rolling thin materials. Control method: Replace the work roll.

9.Under what circumstances will unilateral small waves appear? How to control unilateral small side waves?

• There is a single small edge wave when rolling thin materials because the roll gap is not accurate, and it can’t show up when rolling thick materials. Control method: adjust roll gap or increase unilateral roll bending force.
• 2. The roll hardness is uneven and the unilateral hardness is low. Control method: Replace the work roll.

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