The construction of the new hot strip mill of 1 840 mm in width was started to replace the old one in June, 1982 and was completed on its commercial operation on August 1, 1984, in Nippon Steel's Hirohata Works. The computer control systems of the mill have enabled us to achieve high-accuracy quality controls.
First, we have developed absolute mode AGC system which gives the high accuracy of strip thickness for full strip length. The system is composed of four main functions as described below.
(1) Quick-response AGC with hydraulic screw down system
(2) Compensating control for mass flow balance
(3) Decoupling control of bender and screw down systems for gauge, crown and shape of strip
(4) Set up function for control parameters
Secondly, we have developed crown and shape control system which has high capability by adopting "pair cross roll system" for the first time in the world and work roll bender system of servo-valve drive type. The main functions are described below.
(1) Pre-set function of roll cross angles corresponding to crown schedule for each strip
(2) Feedback crown and shape control of work roll bender system within each strip
