Automatic strip thickness control in tandem mill - corrects thickness at differents speeds through first or second, or first and second stands respectively

摘要

Thickness control of a strip in a tandam mill having >=3 roll stands is effected firstly at a low strip speed by sensing an error in the strip thickness between first and second stands and correcting the error solely at the second stand downstream of the first stand. The error is then sensed at a higher strip speed between the first and second stands and corrected at a stand downstream of the second stand. Strip thickness error is then sensed between the first and second stands at an intermediate speed and corrected at the second stand and a stand downstream of the second stand. The proportion of error corrected at the second stand decreases as the speed rises and increases at the stand downstream of the second stand. the thickness error correction is obtained over a wide range of strip feed speeds without the use of variable time delays. The ratio of the correction applied in the stands at any given strip feed speed is modified during a long term strip thickness error so as to distribute the rolling loads between the stands to avoid load concentration at a single stand.