Continuous casting mould powder and casting process interaction: why powders do not always work as expected

Why does a continuous casting mould powder, which works successfully on a particular caster with respect to semi quality, fail to perform on a caster of a similar design utilising liquid steel from a similar route for an identical product without some tuning of its make-up and composition? In casting sequences of the same steel grade why do some apparently random heats produce poor surface quality with respect to cracking when otherwise good surface quality is realised? The answer to these questions lies in the interaction of the mould powder, the casting hardware, and the casting process variables. Using, as examples, data collected from within Corus UK and during collaborative work on the assessment of mould powder performance and its effects on surface quality, the interaction of the mould powder, the casting hardware and the casting process variables is explored. The steelmaking route and its associated alumina load, unexpected changes to slag chemistry, infiltration of the slag into the mould-strand gap and the nature of the slag film are all shown to affect powder performance.