THE SULFIDE STRESS CORROSION CRACKING CHARACTERISTICS OF THE PIPE WELD IN THE PETROCHEMICAL PLANT

Sulfide stress corrosion cracking (SSCC) in crude oil field environment including hydrogen sulfide (H₂S) has been recognized as a materials failure mechanism. Welding residual stress generation and metallurgical change by fusion welding process increase the cracking driving force and reduce the resistance of brittle fracture as well as environmental fracture. On the base of this understanding, firstly, we analyzed welding residual stresses of welded ASTM A106 Gr B steel pipe using in the petrochemical plant. And next, SSCC tests were conducted to assess SSCC resistance of the weld with smooth specimens. From the result, influence of temperature on corrosion rate was sensitive in order of HAZ, base metal and weld metal. Therefore, the most sensitive region in the weld is HAZ, and its corrosion rate increases with the temperature of corrosion environment increase. And failure positions of the most cases among failed specimens were at HAZ of the weld. Low limit (σ_SSCC) of A106 Gr B steel pipe was assessed as 0.6 σ_y (7271.6N)