Hideaki Furumoto

Pair Cross Type Rolling Mill for Hot Rolling

It has been long recognized that the shape and crown of rolled strips are important for in terms not only of product quality but also of material yield and stable rolling. Furthermore, to raise productivity and to save energy, it is necessary that schedule of rolling, for example thickness, width or materials, is free from constraints. Consequently, it has strongly required that the development of rolling mill to control the shape and crown of rolled strips. A “pair cross type” rolling mill (hereinafter PC mill) has been developed for these requirements. The upper rolls and lower rolls are skewed in a pair which consists of work roll and back-up roll, and PC mills are capable of freely controlling the shape and crown of rolled strips. The first PC mill was put into a practical use at Nippon Steel Corporation Hirohata Works (Now, Nippon Steel & Sumitomo Metal Corporation) in 1984 and PC mills are widely used in the world and they contribute to the achievement of high accuracy and quality of rolled strips through the superior strip crown and flatness controllability.

6-High Type Rolling Mill for Cold Rolling

The rolled strip shape is one of important factors in determining the quality of rolled products. The improved strip shape increases not only productivity but also product quality. Thus, it was desired to develop a new type of mill which is capable of controlling the rolled strip shape even with changes in rolling conditions. The performance of a conventional 4-High mill is not satisfactory in these requirements. A new 6-High cold rolling mill (hereinafter HC-MILL) has been developed in order to solve these shape problems. The HC-MILL for steel rolling was put into a practical operation at Nippon Steel Corporation at Yahata Works (now, Nippon Steel & Sumitomo Metal Corporation) in 1974 and HC-MILLs are widely used in the world and they contribute to the achievement of the controllability of the rolled strip shape and quality through the superior strip flatness controllability.

Endless Hot Strip Rolling

In hot rolling, the productivity or quality of rolled strips is required to be improved and the ultra-thin rolled strips are also required. In order to achieve these requirements, it is necessary that unstable rolling is prevented, especially for head and tail ends, and that cooling of rolled strips is uniform. To meet these requirements, the completely continuous finish rolling, so called” endless hot strip rolling “,has been developed and put into a practical operation at Kawasaki Steel Corporation (now, JFE Steel Corporation) in 1996. This unique technology has realized finish rolling under an uninterrupted tension between rolling stands. As a result, the productivity, quality and stability of rolling have been improved. In addition, the ultra-thin strips with a thickness of less than 1.0mm, and strips with excellent workability by applying heavy lubrication over the full length of the rolled strips have been produced.

Development of Looper Shape Meter and Verification Test Results in Hot Rolling

The harder and thinner strips, such as high strength steel and so on, have been needed to be rolled. When the rolled strip becomes thinner and harder, the unstable state rolling and tail end pinching might occur and so the strip shape measurement during rolling is strongly required under the condition that tension is applied to the strip. Visual-type shape meter, which has been already used, could not measure the strip shape when tension is applied to the strip. Looper Shape Meter, hereinafter referred as LSM, has been developed which could measure the strip shape under the tension. LSM is installed between mill stands and consists of 7 segment rolls along the width direction and a segment roll has two torque meters. LSM could accurately measure the tension distribution along the width direction without hysteresis and is protected with purge air and internal cooling system against severe environment in hot rolling. In order to verify the performance of LSM, the verification test was carried out in laboratory and production line. As a result, enough durability and good results of measured strip shape are obtained. LSM is easily replaced with existing conventional looper and it is expected that LSM contributes to the stable rolling and improve the productivity of rolling.