THERMAL STRESS ANALYSIS OF 304 STAINLESS STEEL JOINTS BY SPOT LASER KEYHOLE WELDING

摘要

In this paper, thermo-mechanical models have been developed to study the complex thermal stress evolutions in spot laser keyhole welding of 304SS and the resultant residual stress in final welds. A comprehensive thermal model including keyhole plasma formation and convection in weld pool was used in the study to predict heating, melting, solidification, and cooling processes in spot laser keyhole welding. Thermal stress evolutions and resultant residual stresses have been accurately predicted accordingly. It is found that high heating and cooling rate (~10~7 K/s) exist in welding due to the quick formation and extinguish of the hot keyhole plasma (>104 K) in laser keyhole welding. High compressive residual stress on the top surface causes bumps there in the final weld. Residual tensile stress in the middle part of the final weld is found to exceed the yield stress of 304SS which indicates the potential thermal cracking occurrence there.