The strip forms a loop between the rolling mills, resulting in a large wrap angle between the strip and the upper roll, which increases the contact area and pressure;
The retention of the regenerated iron scale on the upper surface of the strip increases the wear of the upper roll.
The wear amount of the work roll is distributed unevenly along the length direction of the roll, and the process of forming the worn roll profile is related to the following factors,
1. The size of the rolling unit pressure and its lateral distribution along the strip.
According to the principle of tribology, the amount of wear has a linear relationship with the positive pressure, and the wear of the roll also increases with the increase of the rolling unit pressure, but the lateral distribution of the rolling pressure and the pressure between the rolls is not uniform, so the general pressure Higher parts will cause increased wear.
Seen from the semi-steel roll, the changing trend between rolling pressure and wear is the same, and the pressure is the smallest. Its wear is correspondingly reduced. The wear of cast iron rolls becomes smaller in turn;
2. The total length of rolling, the number of contact times between a certain point on the circumference of the roll and the rolling piece, and the relative slippage between the roll and the rolling piece, including the values of forward slip and backward slip.
At present, there are many sites that use the weight of the rolled strip as a sign to measure the wear of the roll. In fact, the amount of roll wear has a linear relationship with the rolling length, but has no exact relationship with the rolling weight, because the weight of the rolled piece is not only related to the length of the rolled piece, but also related to the width and thickness of the rolled piece. Therefore, it is unreasonable to simply use the weight of the rolled piece as an indicator to measure the wear of the roll. During the rolling process, there is a relative slip between the rolling piece and the roll. Reduced relative slip values lead to reduced wear;
3. Roll surface roughness, friction coefficient and roll surface hardness,
4. The surface condition of the roll, such as the condition of the regenerated iron scale;
5. The relative slip between the work roll and the back-up roll and the lateral distribution of the pressure between the rolls;
6. Arrangement of product types (width, weight, material) and rolling sequence in each rolling unit.
If the strips of each width are stacked according to the width from large to small, and according to the rolled quantity, a ladder shape can be formed, and its outer contour is very close to the shape of the roll wear profile curve;
7. The uneven distribution of the surface temperature of the rolled piece and the roll;
8. Serial movement of work rolls.
The serial movement of the work rolls can promote the uniformity of wear, and at the same time, it can avoid the increase of local wear caused by the temperature drop at the edge of the strip.
