This study is used to construct a mathematical model to analyze melting solidification process considering condition phenomena to an alloy metal in a square section. The aim of the present study, know the time that the metal is solidification in the mold to Know the time that open the mold. After the fluid inters the mold as a liquid, the heat is transferred by conduction and convection, including de thermal phase change phenomena. The mathematical model consists of square section which has length L and [a*b] dimensions. The metal enters the mold from upper end and go to fill all the mold use explicit technique is used to calculate the temperature during the mold and use the thermal phase phenomena from liquid to solid. In this study used Finite difference method to solve the mathematical model also used computer program Fortran 90 to solve this model. The result represented by Golden Software Surfer 8. Also this study may be used in refrigeration of water and studying solidification from the water to ice.