INFLUENCE OF SULFUR CONTENT AND MICROSTRUCTURE OF PIPELINE STEELS ON MECHANICAL PROPERTY AND H2S-RESISTANT BEHAVIOR

Mechanical properties and sulfide stress cracking (SSC) resistances of four pipeline steels with sulfur contents of 5×10~(-6),17×10~(-6),50×10~(-6) and 100×10~(-6) and different microstructures were investigated.The results showed that the high sulfur content of 100×10~(-6) led to the formation ofⅡtype MnS inclusions and worsened the fracture toughness,but has no obvious effect on tensile property and SSC resistance.The steel with acicular ferrite (AF) microstructure exhibited better strength and toughness than that with polygonal ferrite (PF) plus pearlite (P),but their SSC resistant abilities were opposite,which is related to large amount of mobile dislocations in the AF,these dislocations can carry hydrogen atoms and resulted in the hydrogen accumulation.