HYDROGEN INDUCED CRACKING OF WELDS IN STEEL PIPELINES

摘要

The phenomenon of Hydrogen Induced Cracking (HIC) by the absorption of hydrogen from a sour fluid in carbon steel plates is well known, however the question if HIC cracks can penetrate weld deposits is still subject of controversy in both laboratory and field studies. In this research, plates containing Submerged Arc Welding, Resistance Seam Welding and Shield Metal Arc welds, were exposed to cathodic charging to induce HIC and to determine if HIC cracks can grow and pass through the weld materials. The HIC progress in the plates was detected and monitored by straight beam ultrasonic inspection in the A-Scan mode. The results showed that HIC can occur in the weld by the same mechanism as in normal plate in the case of SAW welds, while in the other two (RSEW, SMAW) the crack deviates from its original trajectory to form radial cracks when the HIC cracks penetrate into the weld material. The study is completed by metallographic and fractographic observations of the cracked specimens.