Numerical analysis of twin-roll casting to fabricate a laminated sheet from melts

Abstract

Two types of twin-roll casting process to fabricate a laminated sheet were numerically analyzed in two dimensions. In Type I, which is asymmetric, melts of Mg-AZ31 and aluminum alloy are solidified into a two-layer laminated sheet. In Type II, which is symmetric, these melts are solidified into a three-layer laminated sheet. Assuming the viscosity of a melt and the proportional constant of the flow rule of a Mises material to be equivalent, the rigid-thermoviscoplastic finite-element method was applied to these analyses. As a result, occurrence of buckling and thickening in the clad layer and incomplete solidification in the base layer were predicted as potential problems of the processes. The former was resolved by modifying the separator profile as well as by inducing incomplete solidification in the base layer near the roll exit. The latter was resolved by a subsequent cooling process with pressure rolls, which enhance the bonding strength at an interface and collapse potential voids that would occur during solidification. Details of flow, temperature distribution, solidification, roll torque and roll-separating force were obtained from the analyses.