Numerical modeling of the melting and solidification process is a complex phenomenon. It involves the coupling of various physics, such as thermal, structural & fluid flow. This article examines the solidifying of structural steel metal simulated by coupled thermal, structural, and fluid flow physics was taken in to account and run in COMSOL Multiphysics software. In this present study, both solid and fluid phases are taken in a single domain and separated with a fusion temperature boundary. With the help of Stefan energy balance condition, the moving front (interface boundary of solid & liquid region) through time is calculated. A coupled heat transfer and laminar flow distribution and phase transition by a moving boundary interface were considered. Later, structural analysis is coupled with the study of stress distribution. Numerical modeling of transient coupled multiphysics is used for investigating the thermal distribution, velocity profiles, and stress distributions during the solidification process.