I’ve done some welding in my time, mainly stick welding. I know there are different types of welders namely stick, TIG, and MIG welding, but what is the difference between the three? Is there certain times to use a certain method?
Any info?
I tried google. Lots there.
From the little experience I’ve had…
Stick welding is (was?) the most inexpensive. Just a high-amp power supply and a welding rod. But since its arc is exposed to the air, it builds up oxide (scale) in the weld and adjacent. MIG welding is like stick welding except He, CO2, argon (etc.) gas is blown across the arc to keep the oxygen out of the hot part, and rather than using a welding rod, thin wire is fed into the arc with a trigger and motor. You have to buy gas bottles and wire spools, and I THINK the welders are still more expensive than stick welders. TIG welders also blow gas across the arc, but unlike MIG they have wire feed with an entirely separate electrode (and high-volt power supply) producing the arc.
I think you left out gas welding (as well as some of the newer more esoteric forms of welding.) And as a quick aside don’t confuse MIG with the wire feed units available at Home Depot. These are wire feed flux core welders and are essentially continuous feed stick welders. But no matter.
All these forms do basically two things: They heat the joint, and protect it from atmospheric oxygen which will form oxides and wreck the strength of the joint. They vary in their methods, of course.
Welding rods used in stick welding, as you know, have a solid flux coating that vaporizes and melts as the arc heats it. The outgassing serves to drive atmospheric oxygen, and God knows what else, away from the molten metal being fused at the site of the arc.
Shielded gas welding, a form of arc welding of which TIG and MIG are varieties, use a flow of inert gas to shield (hence the name) the developing weld. Helium and argon are popular gases to use although nitrogen and, paradoxically, hydrogen are also used. In TIG a tungsten (it’s the ‘T’ in TIG) electrode is used to create an arc and heat the adjoining metals to be welded. The torch containing the electrode has a nozzle which blows a continuous stream of inert gas (the ‘IG’ in TIG) over the electrode and out around the weld area. Supplementary metal to increase the size of the weld bead is usually fed into the weld in the form of an uncoated metal rod.
MIG is similar in that a stream of inert gas protects the arc and the weld. The difference is the metal wire creating the arc is also being fed into the joint, thus killing two birds with one stone.
For fun you can try pressure welding, which is what blacksmiths used to do. You just heat up two pieces of metal really hot and bang 'em together until your forearms look like Popeye’s. Hard to believe it really works!
And lest you think that’s horribly low tech, it’s essentially how spin welding, a current new method of welding, is done…
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- Gas welding was the first type, and hasn’t really changed much since it began. If you know how to run a modern torch, you could pick up one made 100 years ago and use it. Oxygen and acetylene are typical and can be used for both steel and aluminun, but other gasses are used also–hydrogen and oxygen are optimum for aluminum for one example.
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- Stick welding was the first electrical type of welding. It uses “consumed” electrodes that are also the filling metal. Flux may or may not be used on the stick electrodes.
- MIG is an acronym for “Metal Inert Gas”, a type of wire-feed welding. All MIG welders are wire-feed, but not all wire-feed welders directly support the use of shielding gas. You can buy MIG-gun kits for most name-brand wire-feed welders.
- Wire-feed welding is a type that uses a continuous roll of wire as the electrode and filling metal. The wire may contain a flux covering, and gas-shielding (inert gas blown out around the wire nozzle, to shield the molten metals from atmospheric air) may be used–as some metals require or benefit from gas-shielding while joining (electrically-welding aluminum requires shielding gas, regular steel does not). Wire-feed welding is the lowest-quality weld, but is the fastest to perform in terms of inches-welded-per-second–it was invented originally for heavy industry for doing long welds on heavy equipment.
- TIG is Tungsten Inert Gas–a tungsten electrode shielded and partly cooled with surrounding inert gas flow is used to strike an arc, into which another piece of metal is melted to form the weld. TIG torches are also often water-cooled, which requires a constant-flow of runoff water (from a tap to a drain) or a circulating radiator system. The tungsten itself wears down but isn’t ever melted directly into the work. TIG is lowest-speed but by far the most precise and the most expensive: a TIG setup for welding steel will cost around $1000, one that can do aluminum will be up around $2000.
- One you probably won’t be doing much yourself is induction welding–used mostly for joining bridge substrates: workers build a frame of heavy steel rods for the roadway surface, then pour conrete over all the rods and after the concrete has cured they attach electrical supplies to the rods in such a way that the steel rods melt together inside the cured concrete… -There’s also exotica such as lasers (CO2 usually), ultrasound (for tiny precision work), friction welding (rub two pieces together until they heat up and stick–lots of turbochargers are made this way) and others less common but these aren’t the sorts of things that you can order from JCWhitney.
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I’ll further point out that MIG is “metal inert gas,” the inert gas avoiding the problems bbeaty pointed out. TIG, then is “tungsten inert gas.” In MIG the wire is the electrode. In TIG, you have a tungsten electrode and feed in another filler metal. Tungsten, as you may know, doesn’t melt at too low a termperature, allowing TIG to weld metals that require higher temperatures.
Then arc of course, is the normal stick welding you’re talking about. It’s generally very course and suitable for really thick stuff.
Me? I prefer resistance welding. You don’t need fillers, plus it’s what I dedicate my life to. 
Well, I see that I’m slow and that my descriptions aren’t nearly verbose enough compared to the winners ;).