A technique for the estimation of instantaneous heat transfer at the mold/metal interface during casting

Many current advancements responsible for improving the accuracy of solidification algorithms have resulted from the incorporation of additional complex casting related phenomena into the numerical calculation scheme. More recently, however, the proper specification of boundary conditions has been found to play a critical role in limiting model inaccuracy. Of particular interest to casting are the temperature boundary conditions, which when adopted by many models appear to be the most troublesome. Temperature boundary. conditions can vary significantly with time and position along the face of the casting and accurate heat transfer coefficients are notoriously difficult to obtain experimentally for all points on the mold/metal interface, especially when the influence of thermal contraction is acknowledged. A novel technique which minimizes the error associated with selecting boundary conditions without experimentation is proposed. Advance knowledge of the air gap formation and its correlation to the heat transfer coefficient at the mold/metal interface is used to formulate a coupled mathematical model which determines the increase of the air gap and predicts the instantaneous cooling conditions at a given mold wall. The objective is to allow the modeler to estimate the effect of thermal contraction on the heat loss at mold/metal interfaces without resorting to experimentation.