Abstract
Heat absorbing characteristics of sand casting molds were examined theoretically with particular emphasis on the effect of geometrical shape of the mold cavity. Dimensionless heat absorbed by a mold plotted against dimensionless time was defined as the characteristic heat absorbing curve of a given mold shape. Heat absorbing curves for several typical shapes were calculated by finite difference method. Difference of solidification time of castings as affected by the shape was judged from the curves to be in the range of ±25%. A simplified method of constructing heat absorbing curves was proposed where a given shape was devided into several unit shapes such as plane, internal corner or external corner and heat absorption by the unit shapes was added together to obtain the total heat absorption. The range of influence of internal and external corners was determined as a function of time and the temperature diffusivity of the mold material. This knowledge was essential in deciding the division of a given shape into unit shapes. Although the method was found sufficiently precise for determining heat absorption by molds, a considerable error was introduced when the method was directly used for determining the solidification time of the castings, since temperature difference within the castings was neglected in the calculation. The method needs future improvement in this respect.
