High speed welding of Friction-Stir-Welding for mild steel by Gas-Tungsten- Arc-Welding hybrid process

Abstract

For the purpose of higher welding speed and lower force in friction-stir-welding (FSW), we investigated the feasibility of preheating using gas-tungsten- arc-welding (GTAW). It can be expected to assist heat input for the plastic flow by using GTAW with high energy density. Defect-free bonding by a GTAW-FSW hybrid process was successfully achieved at a welding speed less than 8.3mm/s, while normal FSW left a defect at welding speed of 5.0mm/s. The axial forces during friction stirring in the GTAW-FSW process were lower than 40% of that in the normal FSW. The joints of GTAW-FSW had stir zones with fine grains similar to the FSW joints. This process could obtain higher productivity, that is, higher welding speed and lower force than the conventional FSW. It is also possible to obtain a high strengthen and unique structure with fine grains of FSW.