During the rolling process, the stress of the backup rolls and work rolls on the shoulder is large, and the work hardening caused by stress fatigue is distributed in the saddle shape on the busbar, which can cause the shoulder to fall off or even spalling.
The roll change cycle of the backup rolls should be adjusted according to the work hardening of the shoulder, and the hardness increase during use should not exceed 5HS. After grinding, the work hardening layer should be completely removed, the hardness of the roll surface should be detected after grinding, and the hardness value should be restored to the original hardness of the roll.
In order to reduce the stress on the roll shoulder, it is necessary to grind chamfer of backup rolls. Using large arc Angle and large arc compound chamfer on the side of backup rolls can significantly reduce the stress concentration of roll shoulder. If the chamfer is too small, there will no effect during the rolling cycle; if the chamfer is too large, the new stress is formed at the chamfer root.
According to the experience of roll use in recent years, if we make the circular arc compound chamfering 1.5mm with circular arc radius above 6000mm in the radius direction of the 200-300 length can effectively eliminate rolling accidents during the service cycle of the backup rolls.