MIG vs TIG welding, for buyers

The short answer

For work outside, welders often use stick instead. More on it below.

What MIG is

MIG, or GMAW, is wire welding. The welder holds a gun that feeds wire from a spool. The wire melts into the joint while gas from the gun shields it.

• It's fast. Miller says wire welding can run up to four times faster than stick on farm repairs.
• It covers a lot: from 24 gauge sheet up to 1/4 inch on car work, in steel, stainless and aluminum
• Looks vary: more carbon dioxide in the gas means more spatter and a rougher bead
• No slag with solid wire, though spatter may still need grinding

What TIG is

TIG, or GTAW, uses a torch with a tungsten tip. The tungsten makes the heat but doesn't melt into the weld. The welder adds filler rod with the other hand.

• It's precise. The welder controls heat, filler and travel separately.
• It handles thin metal, down to .010 inch with the right machine
• It welds steel, stainless, aluminum and chromoly. Aluminum needs an AC/DC machine.
• It's clean: no sparks, spatter or slag. The neat ripples are often called stacked dimes.
• It's slow. Miller calls it much more time consuming than MIG on thin sheet.

Stick and flux core

• Stick (SMAW): a rod coated in flux, held in a clamp welders call a stinger. The flux makes its own shield and leaves slag.
• Flux core (FCAW): like MIG, but the wire is hollow and filled with flux. It leaves slag too.
• Self-shielded flux core needs no gas bottle. Some flux core wires still use gas.

Outside and in the wind

Wind blows the shielding gas away and leaves small holes in the weld. So welders working outside often switch to stick or self-shielded flux core. Miller shows self-shielded flux core welding heavy steel piles on a jobsite.

If your job is outside, ask how the welder will deal with wind.

What it means for your price

• TIG takes longer, so it usually costs more in labour
• Some shops charge more an hour for it. One Texas mobile welder adds US$20 an hour for TIG.
• MIG is the usual pick when speed matters and the weld won't show
• Not sure? If either would work, ask the shop to price it both ways

More on prices: what welding costs.

Which one to ask for

The shop picks the process from the metal, thickness, joint and setting. Ask it why.

Certified welds

• Canada: CWB certifies companies to CSA W47.1 for steel. Welders test for each process and position, with a CWB representative watching.
• US: under AWS D1.1, a welder's record lists the processes and positions they qualified for
• Ask that the welder's ticket covers your process and position. See shop certifications.

Questions to ask a shop

1. Which process fits this metal and thickness, and what will the weld look like?
2. Will you weld it on site, and how will you handle wind?
3. Does the welder's ticket cover this process and position?

Ready for a price? Send one request to welding shops near you.

Sources

• Miller: MIG welding tips
• Miller: TIG welding basics and MIG vs TIG equipment
• Miller: choosing a welder for the farm and wire welding on the farm
• Miller: heat input on thin metal and welding sheet metal
• Miller: MIG for car repair
• Miller: stick electrodes and common welding terms
• Miller: flux core basics and solid wire or flux core
• Miller: filler metal for outdoor work and heavy structural welding
• Iron Trail Welding pricing, Texas
• CWB: test centre accreditation
• AWS: welder qualification and passing a weld test