The effect of external magnetic flux field in the QTS weldment on the change of fatigue crack propagation behaviors

Abstract

This investigation discusses fatigue crack propagation behaviors on the welded joint of Hot Rolled Quench Tempered Steel (QTS) in which during welding process the fusion zone of the joint was subjected to magnetic flux field. The QTS weldability is not really excellent due to the change of microstructure into tempered martensite, and the possibility of microcrack defect on the welding area is still high. The purpose of the investigation is to know the effect of External Magnetic Flux (EMF) field during welding process on fatigue crack propagation behaviors. The external magnetic flux is applied transversely from two sides of the workpiece using a DC powered solenoid of 0, 3, 6, 9 and 15 Amperes. The effect of EMF is more sensitive to decrease the tensile strength and the fatigue crack propagation rate of the weld area. The result shows that the electromagnetic force on the weld pool increases. It causes the liquid metal circulation rate to increase and welding defects to decrease. This indicates that the liquid metal and filler metal are easily mixed, the release of gas from liquid metal to surface before solidification easily happens. The finding shows that the effect of EMF is more efficient.