A group of full penetration butt weld joints are made by MAG welding of P355 NL2 normalized fine-grained steel

the microstructure and properties of welded joints are studied by tensile

bending

impact

hardness and microscopic metallographic tests.The result shows that the welded joint of P355 NL2 normalized fine-grained steel has good tensile and bending properties;the hardness value distribution of base metal is slightly low

while that of HAZ is a little high

both are within the scope of the standard;the impact energy values of the weld and HAZ both are higher than the standard requirement

and both have good impact toughness at low temperature. The central weld microstructure is distributed on the eutectoid ferrite

and the HAZ is composed of ferrite and pearlite with different grain size and strip distribution along the rolling direction.