METALLURGICAL AND ELECTROCHEMICAL FACTORS FOREVALUATION OF SULFIDE STRESS CRACKING OF HIGHSTRENGTH LINEPIPE STEEL

摘要

A proper evaluation on sulfide stress cracking (SSC) of high strength linepipe steel requires a srnound understanding of both metallurgical and electrochemical properties. By measuring independently hyrndrogen flux (J), area fraction of inclusion (Ri), and hardness value (Hv) of steel, the effect of a number ofrnalloying elements (Mo, Cr, CuNi, Ti) on the susceptibility to SSC is evaluated in a sour environment withrnrespect to hydrogen permeation, crack nucleation and crack propagation. On the basis of these 3 factors, arnn index for SSC resistance was estimated, and this index provides information about individual contributirnon of each parameter, which is valuable for alloy design of SSC resistant high strength steel. Optimizationrnof both the metallurgical and electrochemical parameters by addition of proper alloying elements can be arnttained by controlling those 3 factors.