By Brent Boling Feature Understanding Arc Strikes More attention needs to be paid to this often overlooked discontinuity 22 Inspection Trends / July 2013 There appears to be a number of misconceptions with regard to the term “arc strike.” They are often overlooked and/or ignored by many inspectors and, when found, can be the cause of disagreements between inspectors and fabricators. Let’s look at some of the facts about this particular discontinuity. What Arc Strikes Are What do we mean when we use the term “arc strike”? AWS A3.0, Standard Welding Terms and Definitions, defines arc strike as “a discontinuity resulting from an arc, consisting of any localized remelted metal, heat-affected metal, or change in the surface profile of any metal object.” In the Welding Handbook, Vol. 1, Welding Science and Technology, we find this description in Chapter 13, Weld Quality: “An arc strike is a discontinuity that results from intentionally or accidentally initiating the arc momentarily on the surface of the base or weld metal away from the intended weld joint. This can be caused by electrodes or electrode holders contacting the workpiece, ground clamps being too close to the weld location, bare spots in the welding cable, or a combination of these. An arc strike consists of localized re-melted metal and heat-affectedzone metal. Arc strikes can initiate failure of the weldment in bending or cyclic loading as these contain hard spots and usually quench cracks. They create a hard and brittle condition in alloy steels and are inadvisable even on mild steel when high tensile stresses or normal cyclic loading may be encountered.” The Welding Handbook goes on to say, “To prevent the occurrence of this discontinuity, the welder or welding operator should avoid striking an arc on base metal Fig. 1 — Spatter marks. Fig. 2 — An example of a remote arc strike.
Inspection Trends | Summer 2013
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