PREDICTION METHOD FOR DEGREE OF SOFTENING OF STEEL WITH 1GPA GRADE TENSILE STRENGTH

摘要

PURPOSE: A method of predicting softening level of steel with tensile strength of 1GPa is provided to accurately predict the softening level of a softening unit suing time constant equation, which reflects various welding variables, including a focal length, the surface roughness of a welded material, and protective gas. CONSTITUTION: A method of predicting softening level of steel with tensile strength of 1GPa comprises next steps. A laser welding speed is obtained. Time constant to reach transformation temperature is obtained using the laser welding speed. The hardness of the softening unit is predicted using time constant. The steel includes DP(Dual Phase) steel, transformation induced plasticity steel or martensite steel. It is predicted the lower the time constant is, the lower the softening level is. At the step of predicting the hardness of the softening unit, a time constant - hardness table, which is organized by an experiment, is used.