Development of the twin-roll casting process

Twin-roll casting has been used for approximately 40 years for the production of aluminium strip. Traditionally, the process has been one of low productivity and has been restricted to a limited range of alloys and a minimum cast thickness of approximately 6 mm. Moreover, strip produced by this process is susceptible to a number of characteristic casting defects. Despite these limitations, the technique is inherently sound and the current paper describes a development programme that has largely overcome some of the shortcomings of the traditional process. Casting thin (typically 1-2 mm) has the advantage of reducing the downstream processing requirement and in addition it has been demonstrated that significant increases in productivity are possible for a wide range of alloys. However, the increased exit temperatures and increased separating forces associated with casting at thin gauges result in an increase in the tendency for the cast strip to stick to the easter rolls. The phenomenon of sticking is described and a number of methods of overcoming the problems are discussed.