Avoiding cold lap
To the uninitiated, the term cold lap may seem more like a medical condition that a welding term. While in reality cold lap is a serious condition, it is a welding related problem. Cold lap in welding has a lot to with poor welding technique. To a novice weldor, it may look like a nice “fat” weld that might have strong rounded look to the top of the weld. Upon closer inspection though cold lap will show light fusion along the edge or “toes” of the weld. There may be a visible line along the area of the weld where it meets the base metal, or a dotted line appearance along the weld “toes”.
Cold lap is typically created by welding with too little heat or incorrect travel speed or technique. Its not uncommon to see cold lap while MIG welding, steel or aluminum, since many people run too low of voltage with too high of wire speed to try to make a nice stack of dimes look. It’s far better to have a smooth appearance of the weld than to have a nice looking “bead” that is not properly fused.
Stick welding can create cold lap by trying to weave too wide of a weld and “over-reinforcing the weld” and not properly pausing to heat up the edge of the weld so that the filler metal and the base metal will actually fuse. A slow moving low amp weld will pile up weld in the center, and allow the bead to spill over before it is fused to the side of the weld groove.
Though possible to create a cold lap or improperly fused weld with a TIG welder, cold lap is less likely, if a small amount of filler is added at a time and the torch is worked side to side to make sure the filler wets in to the side.
Cold lap can occur in out of position welds such as horizontal welds where gravity works to pull the molten metal, but careful manipulation by holding the weld to the top side longer than the bottom side will keep the weld from lapping over.
Cold lap can be difficult to spot initially, but look for bulges along the edge of the weld or lines that form between the filler metal and the weld itself. Another sign of cold lap is where slap may be difficult to remove and sticks to the edge of the weld.