1.What are the characteristics and main causes of a one-sided wave/single-sided wave?
Wavy patterns only appear on one side of the strip.
Uneven thickness on both sides of the incoming material; uneven cooling or lubrication at both ends of the rolls; tapered wear on the rolls; workpiece misalignment.
2.What are the typical characteristics and main causes of two-sided waves?
Wavy patterns appeared simultaneously on both sides of the strip.
The roll crown is too small or nonexistent; the roll is severely worn in the middle; the tension is too low.
3.How to adjust the hydraulic bending roller?
Increasing the positive bending roll force (positive bending of the work roll) will cause the roll centerline to bulge, increasing the pressure of the roll on the center of the strip, thereby reducing edge elongation and can be used to eliminate double-sided waviness.
Decreasing the positive bending roll force or using a negative bending roll force has the opposite effect, causing the roll centerline to straighten or concave, increasing the pressure on the edges, reducing center elongation, and can be used to eliminate center waviness.
It should be noted that fluctuations in the bending roll force can also cause strip shape problems, so it is necessary to ensure the stability of the hydraulic system.
4.How to optimize the roller shifting strategy?
HC/UCM Mill: By axially shifting the intermediate roll, the harmful contact area between the work roll and the support roll can be altered, effectively controlling edge waviness. For example, in a six-high UCM mill, the shifting amount of the intermediate roll can be precisely calculated based on the strip width: S = B/2 - 300 + δ (where B is the strip width and δ is a correction value). Combined with roll bending technology, edge waviness and wide-intermediate waviness can be well controlled.
CVC Mill: By axially shifting the work roll with a special S-shaped roll profile, the roll gap crown can be continuously and steplessly changed to adapt to different strip shape requirements.
5.How to precisely control tension?
Increasing tension: This allows the strip to be stretched flatter in the width direction, helping to eliminate waviness, especially effective in eliminating center waviness.
Decreasing tension: When excessive tension leads to longitudinal stripes or a risk of breakage, it needs to be appropriately reduced.
A more advanced control method is to establish an optimization model of tension and elongation, finding the optimal tension distribution through iterative calculations to ensure both strip shape and elongation requirements are met.