Effect of microstructure on near-neutral pH SCC resistance of pipeline steels

摘要

In this work, the relationship between the near neutral pH SCC resistance and the yield strength of pipeline steels was investigated and an attempt was made to understand the microstructural effect on such a relationship. Pipeline steels X52, X60, X70, X80 and X100 were used as test materials and various heat-treatments were used to achieve different microstructure and strength (hardness) levels. The results indicate that the near-neutral pH SCC resistance of pipeline steel is reduced with an increase in the strength level but the strength dependence of SCC resistance is heavily affected by the microstructures of the pipeline steels. The steels with a fine-grained bainite + ferrite structure possess much better combination of strength and SCC resistance than those with ferrite + pearlite structure. An increase in pearlite content in the microstructure has a detrimental effect on the SCC resistance.