英文原文 Development of a new type of cold rolling mill for sheet productsMARKET demand in cold rolled steel products has recently increased for thiner and higher strength materials with better flatness.To meet this demand ,Nippon Kokan K.K.and Ishikawajima-Harima Heavey Industuies developed a new type of 5-h cold rolling mill. This flexible flatness control (FFC) mill consists of a small diameter work roll for large reductions at arelatively high speed and a horizontal roll bending system combined with a double-chock roll bending device with the ablility to correct a wide range of shape defects.The FFCmill was introduced successfully as a double-cold reduction mill in NKKs Fukuyama works in June 1982(Fig.1). To clarify the characteristics of the mill,mill experiments have been carried out and an analytical model of the FFC mill developed to campare both shape controllability with other mill types and to establish an automatic shape control system.Concept of the FFC millShmaller work roll diameters are required to achieve higher reductions and to roll more difficult mareial such as steel foil or high strength steel because of the necessity to reduce roll separating force and driving torque. However,since slender woek rolls have large dimensional ratios(ie,barrel length vs diameter), they are deflected easily in the horizontal direction by the roll separating force and strip shape deteriorates. A vertical work roll bending system,which is applied inconventional 4-h mills, is effective in improving strip shape only near the strip edge, especially with small work roll diameters. Therefore, in the case of slender work rolls, it is essential that concepts be developed to prevent the horizontal deflection of the work roll and to expand the ability to correct the strip shape. For this purpose, cluster-tupe mills have been installed which consist of several backup and intermediate rolls. However, these mills have more complex structures and require specially designed housing. In addition, they need a backup roll drive because the diameters of the work rolls are too small to be driven. Hence, these mills hace not been used in the revamp or conversion of 4-h mills.Moreover, strip shape correcting devices with improved functions are now required to correct not only simple shape defects such as wavy edge or center buckle but also more complex defects such as quarter buckle or a combination of center-buckle and wavy edge.The FFC mill solces these problems by applying the following new concepts:A combination of work rools in which one work roll has a diameter similar to those used in conventional 4-h mills with the other work roll having a smaller diameter. Thus, the average diameter of the two rolls is smaller than in a conventional mill. The circumferential speed of the work.rolls is also different.A horizontal bending mechanism with horizontal support rolls which are devede into short segments along the barrel together with a larger offset between both work rolls.A 5-h configuration with an intermediate roll and a doublue-chock vertical bending device between the intermediate roll and work roll with the larger diameter.Design featuresRoll arrangement-The FFC mill is a 5-h type with work rolls of different diameters, an intermediate roll placed between the smaller diameter work roll and the backup roll, and a larger offset between work rolls(Fig.2).with one of the work rolls having a smaller diameter as well as the mean diameter of the two work rolls being smaller than the conventional 4-h mill, it is possible to reduce the rolling load and the roll driving torque.Horizontal bending mechanism - The horizontal bending unit for the smaller diameter work roll consists of a support roll, sectional backup rolls,movable plates,hydraulic cylinders and a supporting brdge(Fig.3). The sectional backup roll unit has six needle bearings with thick outer races arranged at regular intervals.The outer races have a smooth chamfer at the edges of the roll surface to equalize the contact pressure. Between each bearing there are movable plates sliding on the guides of the supporting brdige. The bridge has seven hydraulic cylinders which apply individual horizontal bending forces to the plates. The cylinders are equipped with sensores to measures the stroke of the plungers and the hydraulic pressure.The supporting bridge, which is tightly attached to the mill housing post, has high rigidity.Control system for horizontal roll bending - Seven hydraulic cylinders apply horizontal bending forces to the smaller diameter work roll. Each cylinder has a Magnerscale to detect the stroke position and a pressure. It is able to select a position control or pressure control mode depending on the control scheme.The pressure distribution or pattern produced by the seven cylinders can be symmetrical (to the center of center of the strip width) or asymmetrical. In addition, the total force of