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.
Key words: 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, Carbon/Low Alloy Steel Sulfide Stress
Cracking. ASTM A694, ASTM A350 LF2, Microalloy