Analysis of tandem cold reduction mill with automatic gauge control

MOST of the cold rolled steel strip which is produced today is rolled on tandem cold reduction mills. Fig. 1 shows a 5-stand mill with its unwind and winding reels. The strip fed into the mill has previously been hot rolled and pickled. Each stand, using a combination of pressure transmitted through the work rolls and interstand tension, reduces the strip thickness by as much as 50 per cent. When the delivered strip is later to be plated and made into tin cans, the nominal input thickness to this mill may be 90 mils and the delivered thickness 8 mils. Typical delivery speeds for this product are 3,000 feet per minute up to nearly 6,000 feet per minute. The subsequent operations upon the steel to obtain the finished product require that each coil of strip be rolled to close thickness tolerance. Although mill operators can and do control thickness by manual adjustment, this is difficult and tedious even for the most alert operators. Therefore, a completely integrated automatic gauge (thickness) control for a tandem cold strip mill has been built and placed in service for more than a year. Other equipments are being manufactured and some are being installed on other mills.