Control of mechanical properties in structural steel welds by numerical simulation of coupling among temperature, microstructure, and macro-mechanics

The mechanical characteristics of steel welded structures such as tensile strength or fracture toughness depend on welding conditions, and multiple welding heat cycles particularly affect the joint performance. It should be controlled under consideration of the microscopic and macroscopic behaviors in materials. In this paper, numerical simulation method of coupling analysis of temperature, microstructure, and stress–strain fields has been developed and applied to investigate the effects of heat input and interpass temperature at multi-pass welded joint of beam-to-column connections on the strength and fracture. Tensile test, Charpy impact test, and three-point bending CTOD test are performed by using welded joint specimen fabricated with various welding conditions. The results of experiments actually show that there exists a welding condition that decreases the joint performance. Three-dimensional thermal elastic–plastic finite-element analysis is developed and performed by using heat source movement and considering phase transformation effect in order to evaluate the proportion of microstructure, distribution of hardness and strength. The parameters of heat input, interpass temperature, and welding direction are changed in the analyses, and the results are used for the consideration of the effect of multiple heat cycles on joint performance. The analytical and the experimental results have shown that controlling heat input and interpass temperature are important features to assure the integrity of welded joints in beam-to-column connections of steel framed structures, and that mechanical properties of the weld metal and the heat-affected zone could be predicted and controlled by using numerical simulation.