Effect of cold deformation on Sulfide Stress Cracking of High Strength Steels

摘要

During pipe-end dimensional modification prior to connection threading operation, the material is subjected to a cold deformation process followed by a post deformation treatment (PDT) with the objective of recovering the material properties to the pipe body condition. If PDT is not correctly understood, it could have both mechanical and metallurgical effect on the pipe-end performance in service; being a primary concern for OCTG manufacturers and Oil & Gas operators. This work is focused on providing a quantitative assessment of remnant cold deformation and effectiveness of PDT on sour resistance and mechanical properties of a C110 grade by macroscopically reproducing uniform deformation with tensile/compressive tests followed by heating/soaking/cooling cycles representing induction PDT. Reduction of sour resistance is attributed to the increment of micro-stress of the iron lattice (measured by XRD) resultant from remnant deformation coupled with an incomplete recovery that increases hydrogen solubility. In certain conditions, strain aging/hardening can be produced by the combination of low deformation levels and low energy cycles producing an additional impairment on Kissc recovery kinetics. Results show that the recovery of yield strength conduces to recovery of sour resistance; being faster as the temperature increases.