In the coiling process of common carbon hot-rolled steel strip, interlayer misalignment is one of the key defects affecting coil shape quality, and its occurrence is closely related to equipment precision, process control, and operating procedures. To effectively avoid this defect, a comprehensive and systematic solution is needed, encompassing aspects such as side guide plate positioning, coiling tension management, strip shape control, pinch roll maintenance, and process model optimization.
Precise positioning of the side guide plate is the primary step in preventing interlayer misalignment. Traditional side guide plates often cause axial reciprocating movement of the strip due to inaccurate positioning, leading to misalignment. By developing automatic side guide plate positioning technology, when the strip head enters the side guide plate area, both sides simultaneously activate pressure control modes, pressing the strip until contact is achieved. At this point, the positioning control side automatically exits the pressure mode, ensuring the pressing speed and accuracy of the side guide plate on the strip. This technology significantly improves the clamping stability of the side guide plate on the strip and reduces the risk of misalignment caused by movement. Furthermore, for thin-gauge strips, the side guide plate translation mode can be further optimized. By fine-tuning the opening of the side guide plates, unevenness at the strip edges can be compensated, avoiding misalignment caused by sickle-shaped bends or wavy patterns.
Properly setting the coiling tension is a core element in ensuring coil stability. Insufficient tension leads to loose coiling and increased interlayer gaps; excessive tension may cause tensile deformation during coiling, increasing the risk of misalignment. Operators need to dynamically adjust the coiling tension value according to the specifications, material, and rolling speed of the common carbon hot-rolled steel strip. For example, a lower tension can be used to establish the coil shape at the beginning of coiling, gradually increasing the tension as the coil diameter increases to ensure uniform tension distribution throughout the coiling process. Simultaneously, the roll should not be reversed after coiling to prevent the inner coil from loosening due to tension release, which could lead to misalignment.
Strip shape control has a direct impact on reducing interlayer misalignment. If defects such as camber or waviness occur during the rolling process of common carbon hot-rolled steel strip, it will cause instability in the strip's movement on the cold-roll table, leading to poor centering before the coiling guide, resulting in vibration and misalignment. Operators need to ensure the straightness of the strip's head and tail by reducing rolling speed in the finishing mill and setting pre-leveling values after roll changes. For narrow-section specifications such as cold-rolled stock, special attention should be paid to controlling the waviness at the head and tail to avoid strip misalignment during coiling due to poor shape.
Maintenance and optimization of pinch rolls are key measures to avoid misalignment. Pinch rolls must maintain synchronous movement with the strip during coiling. If the positional deviation on both sides is too large or the pressure applied to the strip is uneven, it will cause unbalanced stress on the strip, leading to misalignment. Using a lower pinch roll design with a convexity allows wear to begin from the highest point of the convexity, helping to maintain a better roll shape and improve clamping stability later on. Simultaneously, the wear condition of the pinch rolls needs to be checked regularly, and severely worn rolls should be replaced promptly. The feedback values from the pressure sensors on both sides of the pinch rolls should also be observed to ensure uniform pressure distribution.
Continuous optimization of the process model is the technical support for improving coil shape control capabilities. For different specifications and materials of common carbon hot-rolled steel strip, suitable coiling control models need to be developed to dynamically adjust parameters such as tension and speed. For example, by optimizing the parameters of the laminar cooling model, the hysteresis rate of the laminar cooling roller table and pinch rolls can be reduced, thereby lowering temperature fluctuations and stress changes in the strip during the coiling process. Furthermore, for thin-gauge strips, specialized coiling process packages can be developed. By adjusting the roll gap setting and opening setting of the auxiliary coiling rolls, the strip head tension loss caused by roll surface wear can be eliminated, reducing the occurrence of inner ring misalignment.
