by Jeff Carver
Most of this is from the AWS (American Welding Society), the leading authority in the US on welding. One thing they have been trying to do is to educate people on consistent terminology, due to common use of brand and outdated names. The AWS is VERY tight about getting info out, unless one BUYS their overpriced books.
Welding: A joining process that produces a unification of materials by heating. Can be done with or without pressure or filler material.
As a generic term welding includes brazing and soldering.
As a specific term welding means that the base material melts along with the filler material.
Brazing: A process of joining materials with a filler material that melts above 450degC (840degF), but below the melting point of the base material.
Most common braze filler materials are is brass, bronze, & aluminum.
Soldering: Same as brazing, but with a filler material below 450degC (840degF), usually using lead or more recently tin based filler material.
Raising the temperature of metal causes it to oxidize very rapidly. Some form of shielding is necessary to keep the air (oxygen) from contaminating the weld. One technique is to use an inert gas in the weld area, usually argon, CO2, helium or a mixture, depending on particulars of the weld itself. Using flux is another technique that uses a solid, paste or powdered material that melts at a lower temperature and physically and chemically protects the weld. Flux usually hardens after cooling off and needs to be chipped, ground, chemically, etc removed. But usually cheaper that gas shielding.
Since heat leads to oxidization (rust), if at all possible, gain access to the backside of welds and clean them up and protect for rusting by paint or other coating.
And now on to some welding processes:
GMAW = Gas Metal Arc Welding, aka MIG (old term) Solid metal weld material. Arc created between the filler metal and the work. Filler metal usually on a coil. Gas shielding for the welding. Usually a point and shoot type of welder. Well suited for thin sections, most popular for body work. Gas costs can be high. Easy to use.
FCAW = Flux Cored Arc Welding, a metal tube with flux in the center, the metal being the weld material, the electric arc being made between the metal tube and the work. Usually this wire is supplied as a coil. Very easy to weld, point and shoot. Difficult to control for thin metal.
Cleanup of flux is necessary after welding. Works well in difficult orientations and in difficult weather conditions (Flux protects weld, as gas would get blown away)
SMAW = Shielded Metal Arc Weld, aka stick welding. A solid metal rod with flux on the outside surface. Well suited to large welds, weld suited to field repairs. A VERY good welder can do thinner materials. Can actually be done using a car battery (not while running though). Weld rods are relatively short, not on a coil.
GTAW = Gas Tungsten Arc Welding, aka TIG (old term), or Heliarc (brand). Weld arc created between tungsten handpiece (torch) and work. Filler metal added in using other hand. Gas shielding from torch.
Can weld VERY thin material (Have seen soda pop cans welded with this process). Slow process, very precise as welder has complete control of welding. Slow learning curve. Filler material usually 36in long.
Flux core and MIG are separate and different processes. Apparently one can get a GMAW machine and use FCAW wire in it without the gas shielding. Sounds logical, but recognize the differences.
As for which rod to use with which base metal,
for the particular machine and at what settings, ask at your local
supplier.
