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Welding basics: Deciding on a type of welder
What's the difference between a simple, wire-feed electric welder and a more expensive model that allows shielding gas to be used? I'm tempted by the lower price of the basic welder, but I wonder what I'd be losing. –Myles Catherwood, Thornhill, Ont.
A wire-feed welder is very easy to use because it automatically advances a thin wire into the weld area. As with all electric welders, it works by creating an arc that generates enough heat to melt the metal being joined; however, this process also leads to an undesirable side effect. The culprit is oxygen. Heat causes oxygen to react chemically with molten metal unless steps are taken to protect the weld zone while it’s hot.
Self-shielding welding wire and shielding with an inert gas that flows out of the tip of the welder during use are two ways to manage the oxygen reaction. The least expensive wire-feed welders are typically designed to use self-shielding wire only. They don’t have the features necessary to connect to a tank of inert gas and direct that gas down to the tip of the welding gun. More expensive welders, on the other hand, can use both self-shielding wire or bare wire, plus a separate shielding gas–whichever you like. Self-shielding wire is much more expensive than ordinary welding wire, but you don’t need to rent a tank and buy gas.
Self-shielding wire is made for general-purpose welding involving steel. A coating on the outside of the wire vaporizes during use, creating the chemical protection necessary for a good weld. Self-shielding wire creates strong welds, but the results don’t look as smooth as what you’d get from more expensive, gas-shielded, wire-feed welders. (You can see the difference in the above illustration). That’s one main difference between the two machines. Gas-shielded welders (also called MIG welders, which is short for metal inert gas) are also capable of welding aluminum with the appropriate welding wire.