Causes and control of strip rolling
In the process of plastic deformation, the strip steel has different degrees of damage to the strip due to excessive local pressure, and the abnormal accident that causes the perforation of the strip to be damaged is called rolling through. Rolling through not only severely restricts the stability of production, but once it is rolled through, it will cause the roll to stick steel and affect the quality of the strip.
Rolling through is a non-uniform deformation in the roll gap area. In fact, it is the mismatch between the convexity of the strip and the shape of the load roll. The main reasons for the changes are:
- Thermal expansion of the rolls
Generally, the strip steel will generate a large amount of heat due to plastic deformation during rolling and friction with the roll during high-speed rolling. Due to the change of continuous rolling speed and the inconsistency of cold and heat in the entire working area of the roll surface, the hot crown of the roll is always A change in volume results in a change in the shape of the load roll gap. If the convexity of the strip is assumed to be constant at this time, the change in the shape of the roll will affect the change of the shape of the strip.
- Strip misalignment
Due to the influence of the convexity, the wedge and the bending of the material, once the sharp change or the deviation is too large to correct the deviation, the center of the strip will deviate from the rolling center line, and as the degree of deformation increases, the rolling force increases. The severity of the strip will increase.
- strip thickness and tension change
Both changes will cause the rolling force to change, but the former causes the actual deflection of the work roll to change, and the latter will also affect the lateral distribution of the strip to change and cause uneven deformation.
- Adjust the relative reduction rate
The reduction rate set by the secondary model is lowered to reduce the rolling force fluctuation. By reducing the relative reduction ratio, the load of the F1 frame is reduced, so that the rolling force coefficient of the unit plate width is controlled to be in a lower range, so that the strip section is uniformly deformed in the roll gap region, thereby reducing the occurrence of the rolling through accident.
- Adjusted tension parameters
The rolling through accident is positively correlated with the tension parameter, and the larger the deviation of the tension, the more likely the rolling wear occurs. The inlet unit tension is adjusted to reduce the tension deviation. The increase of the inlet unit tension not only reduces the rolling force, but also improves the deviation of the strip caused by the tension fluctuation and the tension deviation. At the same time, as the rolling force decreases, the back tension increases and the front slip value of F1 can be controlled. In a smaller range. After taking this measure, the F1 rack rolling through accident was greatly reduced.