An Experimental Investigation of the Sandwich Rolling of Thin Hard Sheets

Abstract

The rolling of hard metals, particularly to thin gauges, presents many sheet manufacturers with considerable difficulties. The high forces to which the rolling mill is subjected may cause excessive elastic distortion of the rolls, thereby imposing a limit on the reduction that can be achieved, or even resulting in roll breakage. The use of small diameter rolls reduces the roll force substantially but the need to support the rolls to prevent them from bending makes such a mill expensive and uneconomic unless the level of production is high. However, a considerable reduction in roll separating force can be achieved on a conventional mill at an economic level by rolling the hard metal sandwiched between softer metal. Also, the rolling of clad metals is necessary to meet particular technological requirements. An experimental investigation of the rolling of high carbon steels sandwiched between the softer metals, mild steel, copper and aluminium, has been carried out on a laboratory 2-high mill instrumented for the measurement of roll force and torque. The effect of various parameters (such as interface friction, relative metal hardness ratios and thickness ratios) on the roll force is considered and an outline of the theoretical analysis of the process given. It is concluded that a reduction of more than 50 per cent in roll force can be achieved with a consequent increase in the maximum reduction possible, and that the process has considerable potentiality particularly for the rolling of thin, hard sheets on a small or medium scale.