This paper presents results from a testing program designed to investigate sulfide stress cracking susceptibility of local hard areas in weld heat affected zones evaluated by 4-point bend testing. Girth welds were made in ASTM A694 Grade F60 and A350 Grade LF2 carbon steel materials. Samples were stressed to 80% and 90% of their actual yield strengths in NACE TM0177 Solution A environments. Cracking of localized hard zones was confirmed in this testing program, which reinforces using Vickers (HV10) instead of Rockwell C Hardness to determine weld compliance with NACE MR0175/ISO15156. The results of this program suggest that the threshold of “applied” stress for cracking of hard zones can be very low, particularly where imbedded weld slag acts as a starting trap for molecular hydrogen to generate high local cavity pressure and initiate cracking in adjacent hard zones. The results of this testing program also suggest that observation of samples using the criteria presented in TM0177 (inspection under 10X magnification) may not be sufficient in cases where local hard zones are present along the heat affected zone (HAZ). With one exception, all cracks detected in this program were found during cross section analysis using standard metallographic practices.

Subject
Rockwell hardness, Test methods, Materials, Welding, Stress cracking, Stress, Stress oriented hydrogen induced cracking, Surveys, Sulfide stress cracking, Hardness, Inclusions, Samples, Hydrogen stress cracking
Keywords:
Sulfide Stress Cracking, Local Hard Zones, Vickers Hardness Survey, Four-point bend testing, Heat Affected Zones, Severe Sour Service, Heat Affected Zone Hardness, Hydrogen Induced Cracking, Weld Hardness, Weld Cracking Susceptibility
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2011
Association for Materials Protection and Performance (AMPP)
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