Cracking in the HAZ or weld metal of carbon and low-alloy steels that often appears hours or days after welding, hence its other names, delayed or cold cracking. It needs three ingredients: diffusible hydrogen from moisture, oil or cellulosic electrodes; a hard, susceptible microstructure; and tensile stress. Low-hydrogen consumables, dry storage, preheat, interpass control and slow cooling each remove part of that triangle.
MT found toe cracks a day after the weld passed VT, classic hydrogen cracking, check their rod oven log.
On high-strength steels many specs require waiting a day or two before final inspection, so delayed cracks have time to show.
Also heard as
- cold cracking
- delayed cracking
- underbead cracking
- hydrogen-assisted cracking
Related terms
Preheat
Heating base metal before welding to slow cooling and drive off moisture, preventing hydrogen cracks.
7018
A low-hydrogen stick electrode with 70 ksi minimum tensile strength, the workhorse rod for structural and pressure work.
HAZ
Heat-affected zone: base metal next to a weld whose structure changed from the heat but did not melt.
PWHT
Postweld heat treatment: heating a finished weld to relieve stress and temper the heat-affected zone.
MT
Magnetic particle testing: finding surface and near-surface cracks in steel with a magnetic field and iron powder.