Optimization of secondary cooling percentage during semi-continuous copper casting process

Abstract

Sufficient cooling is essential to reduce casting defects and to get high productivity in semi-continuous casting of copper billet. On the other hand, low rate solidification is desired in order to develop coarser grain size and softer metal for less energy losses and metal discards in extrusion. Cooling intensity and percentage in both primary and secondary cooling stages was inspected to optimize microstructure and quality of billets. A three-dimensional steady-state numerical model was developed including solidification behavior of copper through mushy zone. Solid shell thickness, pool length, and mushy zone thickness are monitored during the reduction of the cooling rate in the mold region. Adequate primary cooling range is concluded, as a function of mold inlet water temperature, to be between 43 and 63°C. For moderate pool length according to solidification time, not reduced total heat removal, a cooling rate with less available inequality along the billet, and at the range of adequate primary cooling, perfect secondary cooling percentage sets at the range of 52−67%. At this range and for a specified speed of casting, melt at the core needs between 600 and 750 s to start solidification and solidification needs between 125 and 225 s to complete.