A single cold rolling mill can handle small-scale rolling tasks with lower initial equipment investment. Its production organization is more flexible, allowing for quick adjustments to specifications based on market demand.
The old system’s operation and production process relied heavily on operator input setting and field adjustments, with fault diagnosis depending on the operator’s experience. This resulted in high labor intensity and low efficiency. The upgraded system provides accurate settings from model calculations, clear fault causes, and replaces field adjustments with real-time model calculation feedforward compensation, significantly reducing operation intensity and improving fault diagnosis efficiency.
The mechanical control system of a single stand cold rolling mill aims to improve strip surface quality and shape, reduce strip thickness overshoot length, and enhance the lifespan of rolls.
During the rolling process, friction in the roll gap changes significantly with different rolling speeds. If the corresponding system does not respond in time, it can cause noticeable defects in the plate shape, such as corrugations, edge waves, intermediate waves and etc.. This issue is addressed through the calculation of various online feedforward compensation coefficients and continuous self-learning optimization, providing optimal conditions for improving plate shape.
Before the upgrade, inlet and outlet tensions required manual adjustment. Post-upgrade, the system automatically compensates and dynamically adjusts without manual intervention. Previously, manual intervention lagged, causing significant defects, e.g. hundreds of meters of side waves and middle waves wrinkle, during speed changes. After the upgrade, no manual intervention is needed, and speed changes maintain consistent plate shape.
Typically, this type of rolling mill has low dynamic accuracy as one disadavantage. After the upgrade, dynamic accuracy is greatly improved, nearly matching static accuracy due to accurate model preset values and feedforward compensation.
Before the upgrade, when the target rolling thickness was 0.3mm, overshoot length and thickness difference were substantial, and it took a long time to achieve accuracy (red GAUGE1 thickness difference curve). Post-upgrade, with a target rolling thickness of 0.36mm, the overshoot length was reduced by about half, with a 67.5% decrease compared to before. After achieving the target thickness, there is minimal overshoot, resulting in fast and stable performance. Post-upgrade, the overshoot length is consistently between 10-15m, significantly increasing yield.
During the rolling process, strip steel undergoes plastic deformation in the roll gap. The heat from deformation and high-speed friction between the strip steel and the roll greatly raises the temperature in the deformation zone. Before the upgrade, a broken strip would stick to the roll at high temperatures, damaging the work roll, middle roll, and even the support roll, leading to high roll consumption. Additionally, unreasonable manual intervention and adjustments by the operator caused high roll change frequency, more roll grinding times and high roll consumption. Post-upgrade, the advanced control strategy for joint regulation of roll bending force and rolling force, combined with the system’s rapid response, allows for quick adjustment of the roll gap during belt breaks, protecting the rolls and preventing damage. The mathematical model’s precise calculations provide safe and reasonable settings for the roll system, reducing roll loss and belt break probability, thereby extending the roll’s service life.
