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⚡ Welding II: MIG & TIG

Advance to the two most versatile welding processes. You'll compare MIG and TIG, understand shielding gas and settings, and know when each belongs on the job.

15
lessons
~90 min
to learn
🔬 Science
subject
Adults
level
Start the course →

What you’ll learn

  1. Why Wire and Tungsten Took OverPlace MIG and TIG historically and explain the problems each was invented to solve.TIG (Heliarc) arrived in 1941 to weld aircraft aluminum and magnesium; MIG followed in 1948 from Battelle to multiply deposition speed. Together they now span modern welding from robotic production to aerospace precision.
  2. MIG: How the Machine WorksExplain the MIG system: wire drive, constant-voltage self-regulation, and the two main dials.A MIG machine feeds electrode wire continuously through a gun while gas shields the arc. Constant voltage makes arc length self-correcting, and wire feed speed effectively sets amperage while voltage shapes the bead.
  3. Shielding GasesChoose shielding gases for steel and aluminum MIG and set correct flow.Shielding gas keeps air out of molten metal: CO2 is cheap and deep, argon smooth, and 75/25 C25 the steel workhorse; MIG on aluminum and all TIG run pure argon. Flow around 20–25 CFH protects; excessive flow entrains air.
  4. Metal Transfer ModesIdentify short-circuit, globular, spray, and pulsed transfer and their limits.Voltage, current, and gas determine how wire crosses the arc. Short-circuit runs cool for thin metal in all positions; spray runs hot, smooth, and flat/horizontal only; pulsed spray buys spray quality with positional freedom.
  5. Setting Up a MIG WelderSet up a MIG machine end to end: gas, consumables, tension, chart settings, test bead.Repeatable setup order beats improvisation: verify gas and flow, match wire to rolls/liner/tip, set drive tension, dial chart settings, and test on scrap. Stickout is the hidden control — longer runs cooler. A correct arc sounds like frying bacon.
  6. MIG TechniqueApply push/pull direction, gun angle, travel speed, and fit-up discipline.Push gas-shielded MIG for flat, well-covered beads; drag slag processes. Hold 10–15° travel angle and read the puddle's trailing edge for speed. Preparation — clean joints, clamping, tacks, and a shrinkage-aware sequence — is half the weld.
  7. Flux-Core: MIG's Outdoor CousinDistinguish self-shielded and dual-shield flux-core and when each beats MIG.FCAW hides flux inside tubular wire: self-shielded versions defeat wind and own outdoor structural work, while gas-assisted dual-shield adds arc quality for fabrication. Both run hot, penetrate deeply, and leave slag to clean.
  8. TIG: The Precision ProcessDescribe the GTAW torch and the two-hands-one-foot coordination it demands.TIG separates heat (tungsten arc) from filler (hand-fed rod), giving unmatched control at the cost of difficulty. The torch is a collet, ceramic cup, and tungsten; the welder coordinates arc gap, filler dips, and a foot amperage pedal simultaneously.
  9. Tungsten: The Electrode That Never MeltsSelect, grind, and protect tungsten electrodes.Tungsten survives the arc because it melts at 3,422 °C — the highest of any metal. Modern lanthanated/ceriated electrodes replaced radioactive-dust thoriated rods; grind points lengthwise on a dedicated wheel, and regrind after any puddle contact.
  10. TIG on Steel and StainlessRun DCEN TIG on steel and stainless, manage heat tint, and prevent sugaring.Steel and stainless run DC electrode negative, roughly one amp per thousandth of thickness. Stainless shows overheating as color tint, and its back side sugars without an argon purge — the rule on sanitary and corrosion-critical pipe.
  11. TIG on AluminumExplain why aluminum needs AC, cleaning action, and fanatical cleanliness.Aluminum's oxide melts at ~2,072 °C while the metal melts at 660 °C and wicks heat away fast. AC alternates a cleaning half-cycle that shatters oxide with a heating half-cycle, and dedicated stainless-brush prep keeps the weld uncontaminated.
  12. Heat Control: Pedal, Puddle, and RhythmUse the foot pedal, filler rhythm, and puddle-size discipline to control heat.Parts absorb heat as you weld, so amperage must fall to keep the puddle constant — the pedal is a throttle and the puddle is the gauge. The dip-advance rhythm, kept even, produces the stacked-dimes bead; taper heat at the end to avoid crater cracks.
  13. Troubleshooting MIG and TIGDiagnose porosity, feeding failures, and distortion systematically.Porosity indicts the gas system first — bottle, flow, nozzle, drafts — then the metal. MIG burnback and bird-nesting trace to feeding friction. Weld shrinkage warps parts, countered by short welds, skip sequences, clamping, and planned order.
  14. Choosing the Process for the JobMatch MIG and TIG to jobs by speed, precision, metal, and consequence of failure.MIG wins deposition speed and production economics; TIG wins precision, thin and exotic metals, and appearance. Repetition points to wire (often robotic); rising consequence of failure points to tungsten, up to orbital TIG on critical pipe.
  15. Building Skill and Getting CertifiedBuild deliberate practice habits and understand AWS performance qualification.Skill grows from structured practice: one variable at a time, cut-and-etch checks, and honest bead review. AWS qualification bend-tests a welded coupon and certifies you per process, position, and thickness — stackable credentials that raise pay.

Questions this course answers

TIG welding was invented in 1941 primarily to solve what problem?

Russell Meredith at Northrop patented the tungsten-and-helium 'Heliarc' process to weld the light metals wartime aircraft needed — metals stick welding handled poorly.

On a MIG machine, turning up the wire feed speed also increases:

The power source supplies whatever current is needed to burn off the wire being fed — so wire feed speed effectively sets amperage, while the voltage knob shapes the arc.

Why is a MIG arc called 'self-regulating'?

With constant voltage, moving closer raises current and burns wire back faster; moving away does the opposite — the arc length stabilizes itself.

The common 'C25' MIG gas for steel is:

C25 balances argon's smooth arc with CO2's penetration and low cost — the workhorse mix for short-circuit MIG on steel.

Setting shielding gas flow far above the recommended rate causes:

Excess flow becomes turbulent at the nozzle and entrains the surrounding air — causing exactly the contamination the gas is meant to prevent.

Which transfer mode sounds like frying bacon and works in all positions?

In short-circuit transfer the wire dips and shorts many times a second — the bacon sizzle. It runs cool enough for thin metal and any position.

Grounded in trusted sources

  • American Welding Society (AWS) — GMAW and GTAW process resources
  • Miller Electric — Guidelines for Gas Metal Arc Welding (GMAW)
  • Miller Electric — TIG Handbook (GTAW)
  • Lincoln Electric — GMAW and GTAW Welding Guides
  • ASM Handbook, Vol. 6: Welding, Brazing, and Soldering
  • ANSI Z49.1: Safety in Welding, Cutting, and Allied Processes

Every Wunder lesson is built from real, reputable sources — never invented.

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