Mig welding
MIG welding was developed in the 1940's and 60 years later the general principle is still very much the same. MIG welding uses an arc of electricity to create a short circuit between a continuously fed anode (+ the wire-fed welding gun) and a cathode ( - the metal being welded).
The heat produced by the short circuit, along with a non-reactive (hence inert) gas locally melts the metal and allows them to mix together. Once the heat is removed, the metal begins to cool and solidify, and forms a new piece of fused metal.
A few years ago the full name - Metal Inert Gas (MIG) welding was changed to Gas Metal Arc Welding (GMAW) but if you call it that most people won't know what the heck your talking about - the name MIG welding has certainly stuck.
MIG welding is useful because you can use it to weld many different types of metals: carbon steel, stainless steel, aluminium, magnesium, copper, nickel, silicon bronze and other alloys.
Some advantages of MIG welding:
- The ability to join a wide range of metals and thicknesses
- All-position welding capability
- A good weld bead
- A minimum of weld splatter
- Easy to learn
Tig welding
Getting the knack of TIG welding is mostly in getting the weld pool to form, at the same time, on both pieces of metal.
The easiest type of weld is the "fillet", two metals jointed at right angles. (The one shown in this instructable).
The next is the "lap" weld, which is two metals resting flat against each other.
Trickier is the "butt" weld, where two metals touch along the edges - it is difficult to keep the electrode travelling in a straight line along the joint, and tough to keep the weld pool going well on both.
Corners require some skill, as the heat is not dissipated evenly.
You can create "cosmetic" or "strength" welds.
Cosmetic welds tend to look more even over long lengths. Create them by making a weld pool, dipping in the rod, and then moving to the next point. Use them on highly visible joints, like on bicycles.
Strength welds are a lot stronger - use them for things that aren't designed to be seen, or are designed for strength rather than beauty. Anything that needs to bear a load (e.g., a gas canister or propane tank) will have a strength weld. These are the welds where you simply draw the weld pool along continuously, while constantly feeding rod in.
Argon Gas
The use of argon is predominantly for welding Aluminium and Stainless Steel with either Mig or Tig welders
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