Heat transfer mechanism and mechanical properties of triple-wire gas indirect arc welding for low carbon steel

In order to reduce the welding heat input of low carbon steel and optimize the welding deformation and other defects, the triple-wire indirect arc welding (TW-GIA welding) method was used, and the heat transfer mechanism of TW-GIA was discussed based on the infrared temperature measurement system and high-speed imaging measurement results. The results show that TW-GIA welding has a significant advantage of small heat input, and can realize single-pass welding without obvious welding deformation. The width of the heat affected zone was smaller than that of MIG welding. Unlike traditional arc welding, the heat input of TW-GIA welding gradually decrease with the increase of welding height. Heat transfer mode changed from arc heat convection + molten pool heat conduction to only molten pool heat conduction when the welding height increased from 4 mm to 24 mm. The grain size of TW-GIA fusion zone and heat affect zone was small, and the widmannstatten structure was eliminated. The average microhardness of TW-GIA weld zone reached 289.8 HV, the maximum tensile strength was 472 MPa, and the elongation was 26.5%.