Some hobbyist welders in the market for a new wire machine will call it just that; a wire machine.  Some will casually use the term MIG (Metal Inert Gas) or the more formal term from where MIG came,  GMAW (Gas Metal Arc Welding).  What’s with all the terms and what do they mean?

First, there are many types of welding wires for the various welding processes.  MIG wire for the GMAW process, to a hobbyist, is referring to a solid wire, usually carbon steel, that’s almost always copper coated for enhanced conductivity, feedability, and arc quality.  Solid or “hard” wire must have some type of “shielding” to protect the fluid weld puddle from the enemy, nitrogen, while it’s solidifying.  The shielding for MIG wire is almost always either 100% CO2 or an argon/CO2 mix, the most common being 75%Ar/25%CO2.  The latter mix is far more common as 100% CO2 produces excessive spatter (molten droplets that have solidified on the base plate usually outside of the weld = ugly, difficult to remove) and tends to blow through thin gauge plate.

Another common hobbyist welding wire is self-shielded fluxcore wire used in the FCAW-S (Fluxcore Arc Welding-Self Shielded) arc welding process. This wire uses an internal flux that, upon melting, produces both CO2 for shielding and also a physical slag (melted flux) coverage.  Again, Nitrogen is the enemy.  Essentially, the flux has taken the place of a MIG wire’s required shielding gas.  If you’re familiar with STICK welding, think of fluxcore wires as in inside-out stick electrode.

While the GMAW and FCAW-S processes and their associated wires are distinctly different, they both run on a constant voltage power source.  Therefore, with very few exceptions, hobbyist “wire machines” are compatible with both the GMAW and FCAW process.  From an operational standpoint, it’s important to know that MIG wire always runs on DC+ polarity with V groove drive rolls while FCAW-S wire always runs on DC- polarity with knurled (have little teeth) drive rolls.

ADVANTAGES

GMAW                                                                                        FCAW-S

Cleaner weld, no flux to chip off                                            Outdoor use, no shielding gas to be blown away

All position welding with practice                                         All position welding easier than MIG

Best for sheet metal                                                                Better penetration for heavier plate

Solid wires present fewer feeding problems                      Great on dirty, oily, highly scaled plate

Last, is important to know that the little things matter when welding with any kind of wire.  The type of drive rolls, shielding gas (if required), gas flow, polarity, contact tip size/type, input voltage, welding technique and plate condition have to be correct to get the desired result.  Perhaps most critical to making a high quality weld, a balanced welding procedure must be dialed in.  This means understanding the impact that weld variables (wire feed speed (amps), volts, travel speed, CTWD (contact tip to work distance, torch placement/angle/direction of travel) have on a weld.

To this end, General Air has Saturday classes in our state-of-the-art weld school that focuses on the fundamentals of wire processes.  Happy welding!