Effect by Welding Material on Microstructure Properties of X70 SAWL Pipe

The welding tests with two types of welding wires are conducted addressing the problem that owing to the remarkable change of the chemical composition of the blank steel plate which causes the mismatching between the primary welding material and the base metal,and in turn causes the nonconformance of the weld seam low-temperature impact toughness of the SAWL pipe.Based on observation and testing of the microstructure and mechanical properties of the weld seam,the effect by the welding material on the weld seam microstructure properties of the X70 SAWL pipe is analyzed.The test results show that when using the welding wire containing rather high contents of Mn,Si,Cr and Ti to weld the steel pipes of the same batch and the same size with the same welding process parameters,the pro-eutectoid ferrite and the acicular ferrite grains in the weld seam are much thinner,the low-temperature impact toughness value is higher,and the toughness is better.