Welding

Incomplete fusion can be significant because it occurs when the intended fusion does not occur between weld metal and the fusion faces or between adjoining weld beads. Incomplete joint penetration occurs at the root of a groove weld when weld metal does not extend through the required joint thickness. The significance of either condition depends on its location and extent, the applicable acceptance criteria, the loading conditions, and whether it contributed to the reported failure.

Cracking in or near a weld can result from several mechanisms, including solidification behavior, hydrogen-assisted cracking, residual stress, material composition, joint restraint, thermal effects, fatigue, or other service loading. The crack location, orientation, and fracture characteristics can be evaluated together with the weld metal, heat-affected zone, base material, fabrication history, and service conditions. This evidence can help determine which cracking mechanism is most consistent with the observed damage.

Nondestructive examination can help detect and characterize weld discontinuities without requiring the component to be destroyed for testing. Common methods include visual, liquid penetrant, magnetic particle, radiographic, and ultrasonic examination, with the appropriate method depending on factors such as material, joint geometry, discontinuity type, orientation, and location. The results can be compared with applicable acceptance criteria and other evidence to assess the condition of the welded joint.