HIC Material
HIC Material
(OP)
Some times for sour services, HIC steel is preferred. In some specifications, simulated post weld heat treatment cycles need to be performed for a certain steel to qualify as HIC steel. For example, three simulated PWHT cycles need to be performed on a test coupon before carrying out detailed chemical analysis and mechanical testing of that coupon. Temperature need to be maintained at 1150°F for a total of three (3) hours.
Question: What happens to the steel when it is held at 1150°F for a long period of time. Why is such a steel which after such simulated PWHT meets certain chemical and mechanical testing criteria, good for sour service?





RE: HIC Material
In general, to enhance HIC-resistance, plate steels like SA-516 are specified to have a lower sulfur content and are heat treated. The heat treatment can be quenched and tempered (Q&T) or normalized (N).
During fabrication of vessels, the application of heat from welding locally alters the original heat treatment condition of the plate (Q&T or N). In some cases, post weld heat treatment (PWHT) is required to reduce residual stress and to decrease the hardness of the base metal heat affected zone from welding, thus reducing susceptibility to in-service cracking ( or HIC). Extensive testing is performed after several or one long PWHT cycle to evaluate the reduction in mechanical properties and HIC-resistance of the plate base material.
If you want more information on this topic, the web site below contains information on HIC-resistant plate steels;
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RE: HIC Material
Excellent link. Thanks,
RE: HIC Material
Steve Jones
Materials & Corrosion Engineer
http://www.pdo.co.om/pdo/