METAL-MOLD HEAT TRANSFER COEFFICIENTS DURING HORIZONTAL AND VERTICAL UNSTEADY-STATE SOLIDIFICATION OF Al-Cu AND Sn-Pb ALLOYS

摘要

In this work, metal-mold heat transfer coefficients (h) are determined during unidirectional solidification of Al-Cu and Sn-Pb alloys. The effects of casting assembly (horizontal and vertical), alloy composition, material and thickness of the mold and melt superheat are investigated. By using measured temperatures in both casting and metal, together with numerical solutions of the solidification problem, metal-mold heat transfer coefficients are quantified based on solution of the inverse heat conduction problem. Experimental temperatures are compared with simulations furnished by an explicit finite difference numerical model, and an automatic search selects the best theoretical-experimental fitting from a range of values of metal-mold heat transfer coefficients. Experiments were conducted to analyze the evolution of h during solidification of Al-2,4.5,5,8,10,15,33 wt% Cu alloys and Sn-5,10,15,20,30,39wt% Pb in horizontal and vertical steel chills. The results permitted the establishment of expressions as a power function of time, for different alloy compositions, casting assembly material and thickness of the mold and melt superheat.