Analysis of factors affecting the shape of cold rolled steel plates

1. The influence of the original plate: including plate thickness fluctuations, hardness fluctuations, original plate shape, etc.
2. The influence of cold rolling itself: The influencing factors of cold rolling itself include roll crown (including thermal crown), roll wear, rolling force, rolling temperature, rolling lubrication, etc.
Generally speaking, the crown of the roll is expressed by the crown value, that is, the diameter difference between the middle and the end of the roll. The comprehensive crown during rolling refers to the crown that combines the initial mechanical crown, thermal crown, rolling force, and roll bending by a roll bending machine. Shape defects
Mainly due to poor operation during rolling and unreasonable roll design. In addition, the strip itself is of poor quality, and improper pickling, heat treatment, etc. will cause shape defects. Common shape defects include:

The length direction of the sickle-bent strip is bent to one side in the horizontal plane.
Causes: Uneven reduction on both sides of the strip; too much thickness difference or uneven hardness on both sides of the strip; incorrect installation of the rolls (the center lines of the upper and lower rollers are not parallel or intersecting); uneven distribution of lubricant; uneven distribution of the strip Uneven pickling; the thermal expansion temperature difference on both sides of the roll is too large, the wear on both sides of the roll is different, and the tension and the center line of the rolling line are not equal.

(2) The horizontal plane of the corrugated arcuate strip along the rolling direction is curved in an undulating wave shape, and protrusions (crests) and depressions (troughs) are alternately and regularly distributed over the entire length or part of the strip.

Causes: The roll convexity is too large or the reduction is too small; the thermal expansion of the roll surface is too large, the tension is too small, improper process lubrication, etc.
Solution: Use coolant to cool the roller surface, increase tension and increase the reduction, or use lubricant reasonably (especially effective for thin strip steel). If the above effect is not great, it means that the roll type is inappropriate or the "falling groove" is serious and the roll should be replaced. (3) The corrugation appears on one or both sides of the strip along the rolling direction. The shape is like a kelp. The corrugation appearing on one side of the strip is called unilateral corrugation. The two sides are called bilateral ripples, and the ones that appear in the middle are called intermediate ripples.
The causes of single-sided wrinkles: Mainly due to uneven pressing on both sides or poor cooling at both ends of the roll body, or roll taper and uneven lubrication, resulting in uneven thickness of the blank. Prevention and elimination methods include controlling the thickness of the blank, adjusting the pressure and lubrication on both sides, and maintaining consistent cooling and lubrication at both ends of the roll body.

The causes of bilateral wrinkles are: the main reasons are that the roll convexity is too small or has no convexity, or the middle of the roll is severely worn and concave, as well as poor lubrication of the two roll necks and poor cooling at both ends of the roll body. Prevention and elimination methods: increase the crown value of the roll, replace worn rolls in time, keep the two roll necks well lubricated and the ends of the roll body well cooled.

The causes of middle wrinkles: mainly the roller convexity is too large, or the reduction amount is too small, and the tension is too small. Prevention method: Use reasonable roller convexity and increase tension appropriately.

(4) The curved strip steel bends in an arc-shaped direction in the transverse direction.

Reasons: The main reason is that the reduction amount is too small or the roll convexity is too large, which causes uneven deformation of the strip in the transverse direction, or the cooling conditions of the middle and edge parts of the strip are inconsistent, and the thickness or hardness of the billet is uneven.