Semi-solid forming characteristics of Al-12%Si alloy strip surface cast by melt drag process with a forming roll

In order to improve the free solidification surface of strip, the property in case of semi-solid forming of Al-12 mass%Si strip by melt drag process with a forming roll was studied. The effect of some producing factors, such as, roll separating force, roll angle to contact and roll speed on strip property was investigated. As the result, a higher roll speed or a smaller roll angle to contact made the solid fraction of the solidifying strip between rolls lower. Considering solid fraction, the forming pattern of forming roll side surface was classified into two types. On the condition that the solid fraction between rolls is low, it was possible to produce strip with improved free solidification surface under low roll separating force (0.1 kN). On each roll speed, the roll-separating force which causes sticking between strip and roll was obtained. And the relation between roll separating force and reduction, surface quality and microstructure was made clear. From these results, a roll speed higher than 50 m/min is suited for the melt drag process applied of semi-solid forming.