ABSTRACT
This chapter examines the operational and technological developments of the direct chill (DC) casting process for a high volume commercial extrusion business. The provision of consistent high quality DC cast billets of predictable performance is of fundamental importance in operating extrusion presses at maximum efficiency, while meeting the stringent quality requirements of the market place. The DC casting process from melting, through melt in-line treatment, casting and homogenization is discussed in terms of the present best practice and promising novel techniques. The purpose of grain refinement is to produce a refined, equiaxed grain structure with modified second phase particle morphology through the thickness of the DC cast log. Molten metal pre-treatments, carried out in the melting or holding furnace, can be distinguished from in-line treatments given during laundering of the melt to the casting machine. Certain melt treatments, namely grain refinement, degassing and filtration, must be given in-line during laundering to the casting machine to accrue maximum benefit.
