Cracking typically manifests as intergranular surface cracks in the HAZ, often within millimeters of the weld toe. TWI Job Knowledge papers note that LME susceptibility increases with heat input, restraint, and zinc coating thickness above 85 ?m per side. AWS D1.1 Annex M provides guidance on reducing LME risk through joint design and process selection.
Prevention strategies include grinding the zinc coating 25-50 mm from the weld zone, using a lower heat input process like GTAW or pulsed GMAW, and maintaining a minimum preheat of 150?C to slow the cooling rate. Post-weld inspection with magnetic particle testing (MT) or dye penetrant (PT) is recommended to detect shallow LME cracks that may escape visual detection.
Understanding LME is critical for fabricators working with hot-dip galvanized structural members, where a single undetected crack can propagate under service loads and lead to catastrophic failure.
Source: AWS D1
How does your shop manage LME risk on galvanized steel welds?