Reliability Engineering Snapshot TM

Corrosion - Case Study No. 68: Weld Arc Strike Becomes Corrosion Nucleation Site

Haphazard welding arc strikes that occur outside of the weld bead area can come back to haunt you. While doing a failure analysis in a completely different area, the analyst happened to notice a random arc strike well outside of the weld HAZ area. What was unique about this seemingly innocent strike was that it was being aggressively attacked, as there were several hairline cracks that had already traveled some distance into the metal. What was even more scary was the fact that it wasn't even in a load zone. A close up of the arc strike is shown in the picture to the lower left. It is quite evident that the micro structure in this vicinity had completely changed.

The AWS structural steel code D 1.1 addresses this potent problem. Unfortunately they address it in the "Commentary Section" of the code, stuck way way way back on page 402. It is titled "Arc Strikes"(C5.29) "Arc strikes result in heating and very rapid cooling. When located outside the intended weld area they may result in hardening or localized cracking, and may serve as potential sites for initiating fracture." You got that right.

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