Using two welding processes

high-frequency pulse MAG welding and conventional pulse MAG welding

the welding process test was carried out on the 12 mm thick SMA490BW weather-resistant steel plate T-joint（fillet weld）

the macroscopic

penetration and the microstructure of the welded joint were analyzed

and the Vickers hardness HV10 and welding residual stress of the welded joint were also tested. The results show that comparing to the ordinary pulse MAG welding at the similar welding heat input value

the penetration of highfrequency pulse MAG welding increases by 20% ～30%

the residual stress at the HAZ（12 mm from weld toe） reduces by about 11%～26%

the high-frequency pulse MAG welded joint shows ideal microstructure characteristics

there is high content of acicular ferrite（AF） in weld

no ferrite side plate（FSP） and less content of grain boundary ferrite（GBF） in bond

and the grain coarseness of the grain coarsened zone（CGZ） is less. The vickers hardness HV10 value of the welded joint in two welding processes is less than 380 HV10

which meets the requirements of the welding procedure qualification standard.