Kunio Sekiguchi

Optimal multivariable looper control for hot strip finishing mill

An optimal multivariable looper control system based on optimal-regular theory has been developed for hot-strip finishing mills. Loopers of the mill are installed between stands and are in many cases driven by motors. The goal of looper control is to maintain product quality at a high level by stabilizing the rolling operation. Stability is achieved by keeping the looper angle and tension applied to the strip at given reference values. Control-system features are outlined. It is shown that the control system can maintain a relatively constant strip tension without operator intervention in the presence of rapid change of hydraulic screw down such as automatic gauge control operation. Data obtained at a commercial plant demonstrates that optimal multivariable looper control is more effective than conventional control or noninteractive control.<<ETX>>

Looper H-infinity control for hot strip mills

The H-infinity control theory has been applied to some engineering fields including the steel making process. The H-infinity control theory makes it possible to apply multivariable control with frequency domain design method and to get robust stable control systems. The author developed a looper H-infinity multivariable control system for hot strip finishing mills, and have obtained better results than conventional control methods. The looper control is one of the most important control methods in hot strip mills. The loopers are placed between each rolling stand, and control the interstand strip tension. It is very important to control stably both looper and strip tension at each of their target values. Especially, the authors intended to reduce strip tension fluctuation than looper angle fluctuation, because strip tension severely affects thickness and width gage. This paper presents the design method of the looper H-infinity control system. Also showing some actual control data, they compare the performance of conventional PI control, noninteractive control, and H-infinity control.

Tension Control of a Hot Strip Mill Finisher

Abstract This paper describes interstand tension control by looper and looper less tension control of a hot strip mill finisher. The looper tension control methods are conventional, non-interactive, LQ (Linear Quadratic), H∞, and ILQ(Inverse Linear Quadratic) control.

Hot strip mill mathematical models and set-up calculation

A hot strip mill setup calculation approach has been developed with particular emphasis on the development of a method of optimizing the load distribution among the stands and on the development of accurate setup models. The calculation system includes mathematical models of temperature and deformation resistance in rolling materials. The setup calculation has been carried out for a New Zealand hot strip mill that consists of a reversing rougher and a four-stand finishing mill. With this configuration, a strip was successfully rolled with a finished thickness of 2 mm and a width of 1250 mm. It is concluded that: (1) an effective algorithm for the redistribution of stand rolling powers when the power exceeds the limit can be achieved using the influence coefficient of strip thickness to power: (2) effective temperature modeling can be achieved using a model that incorporates the insulating effect of the coil box and represents the heat loss in the finishing mill with an effective heat transfer coefficient; and (3) for a finishing mill with a coil box, higher accuracies can be achieved by using the cumulative strain to calculate the strip deformation resistance.<<ETX>>

Application of a Temperature Control System to a New Hot Strip Finishing Mill

Abstract Material temperature on the delivery side of the finisher is an important factor in the mechanical properties of the product coils. In order to achieve and maintain the target delivery temperature of the finishing mill, a finisher delivery temperature control system (FDTC) was developed for implementation in a newly built hot strip mill. The temperature control system includes mathematical models of finishing mill temperature, which are used to preset the rolling speed and interstand cooling spray (ISC) flow rates, and a temperature control algorithm that uses the interstand cooling system. FDTC has two main control modes. Feedforward control using the temperature models is very effective. This control system was applied to the China Steel Corporation (CSC) No.2 hot strip mill which began rolling at the end of 1996. The control system achieved excellent temperature performance in the product coils.

Development of strip tension stabilization by decentralized control strategy based on Advanced mill drive system suppressing resonant vibrations in hot strip finisher mill

Abstract Recently, Steel Industry has faced serious demands of products quality improvement and drastic competition of cost reduction in production. Hot strip finisher mill, in particular, is the important process in steel industry, and has to satisfy product quality and reduction of production cost as the users demand. Now as for the products quality, thickness accuracy at head end and tail end remains open area to be improved by advanced control methods. And the operation support system at strip threading of strip is necessary to reduce the production cost. So this paper shows that AC drive system performance is successfully combined to decentralized method and that strip tension control has realized quicker response, and thai as the results, thickness accuracy has been improved drastically.

Automatic Flatness Control of Cold Rolling Mill

One of the subjects of cold rolling is a flatness of the rolled strip. Conventionally, measured strip flatness was approximated by polynomial (2th, 4th, 6th) equation across the entire strip width. This made it difficult to deal with desired loose edge or any desired flatness across the entire strip width. Also conventional flatness control was done for the entire strip width, so if there is a different flatness error among drive side and work side, conventional flatness control can not control properly. We propose independent strip flatness control among drive side and work side, and also automatic flatness control (AFC) system with arbitrary desired strip flatness. Also some applied results to cold mill are shown.

Flying Gauge Change Control for Hot Strip Finishing Mill

Abstract The technology for an FGCC (Flying Gauge Change Control) system to be used in hot strip finishing mills has been developed by Toshiba Corporation and Nippon Steel Corporation. The recent need for continuous rolling in finishing mills necessitates an FGCC system which can perform rapid gauge change in hot strip mills. One of the most important elements of FGC is efficient change of roll gap and roll speed at each stand. The complete FGCC system comprises AGC (Automatic Gauge Control) and OMFC (Optimal Mass Flow Control) subsystems. Data from Hirohata Works of Nippon Steel Corporation indicates that the system has performed well in controlling flying gauge change during rolling.

Strip Profile Control System for Aluminium Hot Strip Mill

Abstract This paper discusses the strip profile control that was carried out at an aluminum hot strip mill. Calculation procedures for setting up the actuators for each stand of the 3-stand finishing mill involving the double chock work roll bender, VC backup roll/ and work roll coolant spray pattern, necessary for achieving the target strip profile without adverse effect on flatness are presented here in this paper. The work roll thermal crown model and strip profile model that are used for the above strip profile setup are also explained. The results of applying this control system tc the hot strip mill in the Fukui works of Furukawa Aluminum Co. Ltd. are also shown.