Kevin explains what flux core welding (FCAW or FCA, “flux-cored arc welding”) is and how it compares to welding with gas. Flux core wire is a metal wire with the flux impregnated into the wire. You use it instead of the stick electrode used with arc welding. He explains that flux core welding sort of falls between arc welding and MIG welding. The difference is that, instead of using an arc welding electrode, you use flux core wire. It comes on a spool, which is more like MIG welding (GMAW, or “gas metal arc welding”). But you usually use no gas (although there is some flux core wire that requires gas), whereas with MIG welding, you use gas to shield the molten metal from oxygen until it cools to avoid contamination. The benefits: flux core welding is quick, easy, can be used outside, and is wind-resistant, much like an arc welder. You can also weld longer with flux core than you can with arc’s relativel short welding electrodes, and different size spools of wire are available. The disadvantages: it’s smoky and can be messy, requiring clean up – including having to chip off the slag. With MIG welding, the inert gas helps you get a cleaner weld, and, in his opinion, a better weld. As for the price, the flux core wire is a little more expensive than the solid core welding wire, but you have to buy the gas, bottle, etc. so the cost pretty much washes out. Kevin then demonstrates the difference. He moves to the vise where he has set up a railroad spike for a sculpture he is working on. He fires up his Longevity MigWeld 140 with .035 flux core welding wire, with the wirefeed set at 40 and the volts set at 9. He welds one side of the bottom of one spike to the top of another. The first thing you notice is the soot around the weld, which Kevin removes with a wire brush. He then comes back and chips away the slag with his chipping hammer. Then he turns on his Miller 251 MIG welder with .030 solid core wire at 20.5volts and the wirefeed set to 230 and welds the other side of the spike with it. He displays both welds. The MIG weld is cleaner looking, with additional soot and splatter around the flux core weld. Kevin then bangs the welded spike against his workbench to make sure the welds hold.