The effect of SMAW welding parameters on stress corrosion cracking of the X65 gas pipelines steel

Abstract

Steel pipelines used for oil and gas transmission are at risk of stress corrosion cracking (SCC). Extensive research has been carried out to evaluate the SCC susceptibility of pipeline steels. Those research studies were mainly specific to the steels of pipes without welding. In this research, pieces of X65 steel plates were welded by the shielded metal arc welding process. The speeds of electrode travel were set as the main welding parameter. Slow strain rate tests (SSRTs) in the air and the NS4 standard solution were conducted. The results showed that the tensile behavior of the samples in the solution was very different from that in the air. For the samples tested in the solution, the strength amounts of the weld zones were higher than the strength of the base metal, but in the case of SSRT in the air, the strength of the base metal was higher. As a result, the UTS strength of one of the weld zones reached levels as high as 480 MPa and also 34% elongation under the SSRT. Therefore, the conditions of welding have a high degree of importance and must be controlled to have less SCC susceptibility.