Analysis and Prevention of Staggered Rolls in Short-stress Rolling Mill

1.Introduction

Due to the axial movement of the rolls or other reasons, the pass centers of the upper and lower rolls are not coincident, so the rolled pieces of the correct shape and size cannot be rolled, which affects the quality of the product. This defect is called the wrong roll. Recently, under full-load production conditions, the number of mis-roll defects caused by short-stress rolling mills has increased. This article analyzes the causes of the wrong roller to propose solutions.

2. The cause of the wrong roller

2.1 Reasons for the axial movement of the rolls

Check and analyze the short-stress rolling mills that are offline due to axial movement. The reasons for the axial movement are as follows:

(1) The thrust bearing is damaged, resulting in a large amount of axial movement.

(2) Bearing end cover, internal thread end cover, bearing seat, internal thread through cover end surface or thread is worn, and the clearance is too large, and axial movement will also occur.

 

(3) The tension rod, the pressure-bearing flange, and the pressure-bearing ball pad are worn out, and the elastic damping body fails, etc., which will also cause axial movement.

 

(4) The roll locking device is not tightened, and the axial adjustment device is too loose or too tight, which will also cause axial movement.

 

(5) During roll turning, the gap between the upper and lower roll holes is inconsistent, resulting in misaligned rolls (not axial movement).

 

2.2 Wrong roll caused by steel rolling operation

(1) The axial adjustment mechanism of the short-stress rolling mill has two types of layouts: left and right. The worm gear and worm spare parts of the two arrangements are the same and can be interchanged. However, the direction of axial movement of the adjusting roller is completely opposite (see Figure 1). When the adjusting worm is at the left end of the bearing housing, turn the adjusting worm clockwise, the roller rotates clockwise, and the upper roller moves along the non-adjusting end. When the adjusting worm is at the right end of the bearing seat, turn the adjusting worm counterclockwise, the roller rotates clockwise, and the upper roller moves along the non-adjusting end. Limited by the number of rolling mills, in the state of full-load production, the short-stress rolling mills are used in various lines, and the support operators come from each production line. If the operators do not pay attention to the position of the worm, adjust the direction of the axial movement of the rolling mill. Past experience may make adjustments in the wrong direction. At this time, the more you adjust, the greater the amount of mis-roller. Eventually, the adjustment mechanism will be crushed, and the adjustment will not be possible, and the roller will be forced to change.

After the roll pass is adjusted in the axial direction, if the operator does not lock the set screw, the wrong roll will occur after a period of production.

3. Measures to solve the wrong roller

(1) Re-preload the rolling bearing to eliminate the gap caused by the reduction of the pre-tightening force caused by the wear of the rolling bearing and related parts, and realize the axial pre-tightening.

 

(2) Give a certain axial load when installing the thrust bearing to prevent and eliminate the axial movement caused by the same period vibration.

 

(3) On-site steel rolling operators must fully grasp the principle and adjustment operation of the axial adjustment mechanism.

 

4. Conclusion

The operation of short-stress rolling mill equipment is closely related to the quality of equipment maintenance and repair. The correct rolling operation method is of great significance for improving work efficiency and product quality.

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