Recent Advances on 20-HI Cluster Mill Optimization

by REMN-MIN GUO

Publisher - TENOVA I2S

Category - General Novel

A 20-hi cluster mill is simply a precision mill used to roll ultra-thin and/or ultra-high-strength material. The conventional monoblock mill provides the greatest mill modulus among all types of mills, which prevents the mill from control instability and to guarantee the target thickness. The mechanical advantage of 20:1 ratio let the AGC cylinders take only 4~6% of separation force and also substantially increase the gage control resolution. The closed loop shape control composed of the shapemeter roll, the intermediate roll shifting, and power crown backing bearings offers a very precise shape control with selectable target shape pattern. However, there are still some areas for further improvement, such as fast rolling pressure release during cobble, large mill opening for easy cleaning after mill cobble, mill tilting for wedge strip from slit coils of upstream operation, accommodation of larger work rolls for multi-purpose rolling, measurement of separation force and other effective rolling parameters, semi-automatic threading for better productivity, improved roll utilization ratio for cost saving, optimal roll configuration for bearing life extension, and various force and crown/shape rolling models to upgrade control performance. Facing these additional critical features, the new mill design should mingle the conventional advantages with modern design concepts – a hybrid design. Recent advances on the cluster mill can be discussed from the viewpoints of conceptual novelty, mechanical design, and achievements of various control innovations. This article will start from the pro and con of the conventional monoblock cluster mill, followed by optimization methods and related design concept. The basic mechanical design, the creative concept, and the supporting theory shuttles through the entire article so as to better describe the additional features of the 20-hi cluster mill.

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