Inward and outward solidification of cylindrical castings: The role of the metal/mold heat transfer coefficient

The numerical simulation of cylindrical castings can only produce reliable information if the thermal boundary conditions, such as the metal/mold heat transfer coefficient (h), are known accurately. Despite the importance of h for cylindrical shaped castings, information available in the literature is meager. In the present study, an extensive experimental study has been developed encompassing horizontal and vertical cylindrical shaped castings. Alloys having quite different thermal properties and freezing ranges have been selected for the experimental study. An inverse heat conduction method supported by temperature measurements at known locations inside the cylindrical heat conducting bodies has been used to derive time-varying heat transfer coefficients in both concave and convex mold/alloy surfaces (inward and outward solidification, respectively). It is shown that the h(t) profiles are given by an expression of the form h = at±m, where (−) refers to the inward solidification and (+) to the outward solidification against an inner mold.

► Heat transfer coefficients, h, are reliable information for the design of castings.
► For cylindrical shaped castings, h as a function of time, t, is given by h = at±m.
► For convex mold/alloy surfaces h increases with time during solidification.
► For concave mold/alloy surfaces h decreases with time during solidification.