Analysis of crack causes and effects of the A333 low carbon pipeline steel after thermite welding

By thermite welding on steel pipelines with an anode material to protect the cathode, cathodic protection has been widely used to prevent steel base pipelines from erosion. In this paper, some cracks were found in an accidental magnetic particle examination by the workers after thermite welding on steel pipelines. Therefore, a series of characterizations were conducted on the macro/microscopic morphologies, mechanical properties of the cracked A333 low carbon pipeline steel to find out the causes and effects. The obtained results show that the coarse martensite with a certain thickness in HAZ come into being bringing about plasticity reducing, strength and hardness increasing. And large welding stress and uncoordinated deformation lead liquid copper to infiltrate into the prior austenite grain boundaries in HAZ of the pipeline causing the formation of the copper penetration cracks.