Fundamental Study on Thermal Stress Generation during Simulated Welding Heat Cycles

—Studies on Numerical Simulation of Temperature, Microstructure, and Thermal Stress Histories during Welding Process and Their Application to Welded Structures (Report 1)—

Abstract

Characteristics of a welded joint should be evaluated considering not only mechanical but also metallurgical properties, and weld residual stress is possible to be controlled by considering and changing mechanical / metallurgical properties of the materials. History of thermal stress due to phase transformation and residual stress during welding heat cycles are studied in order to clarify the generating mechanism of residual stress and the effects of material properties such as phase transformation on stress generation. Two materials of high-tensile strength steels are used in the numerical simulation and experiment. Material property of each microstructural phase is used and the time- and temperature-dependant proportion of microstructure are considered by using CCT-diagram in the analysis. Thermal stress history obtained by the numerical simulation agrees well with the experimental result during welding heat cycles. The effects of welding heat cycles on thermal stress histories and residual stress are then investigated.