1998 Volume 38 Issue 10 Pages 1107-1113
Scientific and technical progress is presently impossible without the application of a new generation of materials with unique properties. Fine-grained alloys, obtained by rapid solidification technique in twin-roll casting process, belong to this class of materials. The commercial success of the twin-roll casting technique depends on the quality of its cast products, first of all on the cross-sectional shape of the strip. Otherwise, an additional post treatment of the as-cast strip such as cold rolling can deteriorate the unique properties of the strip.
To gain a better understanding of the influence of technological parameters on the cross-sectional shape of the strip, a laboratory-size twin-roll casting process has been investigated both theoretically and experimentally. It was found that the geometry of the nozzle slot, the roll sleeve thickness, diameter and length of the roll and the pressure profile between the rolls may influence the cross-sectional shape of the strip. Increasing the nozzle slot length, the flow rate and the distance between the nozzle and the melt bath surface increases the probability of formation of the thickness non uniformity across the strip width. The design of the roll plays a major role in the formation of the cross-sectional shape of the strip: a convex profile is produced by bending of the rolls whilst a concave profile results from thermal expansion of the rolls, in the case of a thick, water-cooled sleeve. The shape of the pressure profile between the rolls depends on the ratio strip width to roll length. Optimisation of the sleeve thickness, diameter and length of the roll is one of the possible ways of improving the cross-sectional profile and the flatness of the as-cast-strip.