The invention provides a gas shielded
welding technology of steel Q420GJC for a building structure. The technology comprises the steps that a
welding material is prepared, wherein
welding wires WH5-GJ with the
diameter phi of 1.2 mm are prepared; the welding environment temperature is higher than or equal to minus 10 DEG C; the preheating temperature is 100 DEG C-150 DEG C; multi-layer and multi-pass welding is performed, and the interlayer temperature is no lower than the preheating temperature; weld joint priming is performed, wherein the welding current is 240-260 A, the welding
voltage is 26-28 V, the welding speed is 30-32 cm / min, and heat input is performed at 9.4-10.2 KJ / cm; weld joint filling is performed, wherein the welding current is 280-300 A, the welding
voltage is 28-30 V, the welding speed is 34-36 cm / min, and heat input is performed at 10.4-11.3 KJ / cm; weld joint capping is performed, wherein the welding current is 300-320 A, the welding
voltage is 28-30 V, the welding speed is 36-38 cm / min, and heat input is performed at 10.5-11.4 KJ / cm. Q420GJC steel welding is performed by adopting the welding technology, the
mechanical property same as that of
base metal is obtained, the quality requirements of
engineering welding are met, and a gap of gas shielded welding of the Q420GJC steel is filled.