Different Types of MIG Welding: The Complete Guide

A hobbyist buys a 180-amp MIG welder, loads a spool of ER70S-6, hooks up a bottle of 75/25 gas, and gets beautiful beads on 16-gauge sheet — then melts a hole straight through a 1/4-inch plate the same afternoon. Nothing about the machine changed; the type of MIG welding did. Understanding which MIG variant you are actually running is the difference between a clean weld and an afternoon of spatter, burn-through, and guesswork.

What Is MIG Welding, and Why Are There So Many Types?

At its core, MIG welding is almost disarmingly simple. You pull a trigger, a spool of wire spins, and that wire feeds continuously through a handheld gun, out of a contact tip, and into an electric arc that melts it into the joint. The wire is simultaneously the electrode that carries the welding current and the filler metal that becomes the weld itself. A shielding gas flows out around the arc to keep oxygen and nitrogen away from the molten puddle, and a constant-voltage power source holds the arc steady as the operator moves the gun along the joint. That is Gas Metal Arc Welding, or GMAW, in plain language.

Which immediately raises the question this article exists to answer: if the process is that simple, why are there so many different types of MIG welding?

Because “MIG welding” is really four separate decisions stacked on top of each other, and most beginners never realize it until something goes wrong. A welder running short-circuit transfer on 20-gauge sheet and a welder running pulsed spray on half-inch plate are both, technically, “MIG welding.” They are doing almost nothing alike.

The Four Ways to Classify MIG Welding

Every time someone asks which “type” of MIG welding they should use, they are really picking from one or more of these four axes:

• Metal transfer mode — how the wire crosses the arc: short circuiting, globular, spray, or pulsed spray. This is the single biggest lever on heat input, spatter, and position capability.
• Machine or process variant — the named waveform technologies built on top of the basic process, such as pulse MIG, Pulse-on-Pulse, Cold Metal Transfer (CMT), Surface Tension Transfer (STT), and tandem or double-wire setups.
• Electrode type — solid wire, flux-cored wire, or metal-cored wire. This changes whether you need a gas bottle at all, what polarity you run, and how much cleanup you do afterward.
• Base material — mild steel, stainless, aluminum, or copper and nickel alloys. The metal you are joining dictates the wire, the gas, and often the transfer mode before you ever touch a dial.

These axes are not academic. Choose the wrong combination and the symptoms are immediate and physical: burn-through on thin sheet, cold lap and incomplete fusion on thick plate, porosity, spatter that takes twenty minutes to grind off, or a warped panel that no amount of technique can rescue. Heat input, penetration depth, bead appearance, welding position, and usable material thickness all shift as you move between types. The machine in the corner did not change between the perfect bead and the hole in the plate; the type of MIG welding being run did.

A Short History: From Battelle to the Shop Floor

The process came out of research at the Battelle Memorial Institute in the late 1940s, where scientists worked out how to feed a thin electrode wire into a controlled arc without the wire fusing inside the contact tip. Industrial commercialization followed quickly: Unimation, in partnership with General Motors, put robotic MIG welding into automobile production lines in the early 1950s, where its continuous operation and repeatable quality were a near-perfect fit for an assembly line.

That fit is why MIG became the most widely used industrial arc welding process in the world. It is fast, forgiving, and easy to automate. According to NIOSH census data, more than 700,000 workers in the United States are involved in welding or allied processes, and a very large share of that work runs through GMAW and its variants. The process is specified in code work under documents such as AWS A5.18, the governing specification for carbon steel GMAW electrodes and rod. Notably, the 2021 edition of A5.18 replaced prescriptive current and voltage requirements with a qualified heat input range — a quiet but meaningful shift that acknowledges just how much the “type” of MIG you run affects the finished weld.

For a fuller look at the machine-side details behind all of this, see our Aluminum MIG Welding: The Complete Practical Guide.

Quick Reference: Four Classification Axes

Axis	Options	What it changes
Metal transfer mode	Short circuiting, globular, spray, pulsed spray	Heat input, penetration, spatter, welding position
Process variant	Standard CV, pulse MIG, Pulse-on-Pulse, CMT, STT, tandem/double-wire, hot-wire	Bead appearance, thin-material capability, deposition rate, automation potential
Electrode type	Solid wire, gas-shielded flux-cored, self-shielded flux-cored, metal-cored	Gas requirement, polarity, slag cleanup, wind tolerance, deposition rate
Base material	Carbon steel, stainless, aluminum, copper/nickel alloys	Wire selection, shielding gas, transfer mode, feed system, preheat

Work through the rest of this guide in any order you like, but keep that table in mind. The next section covers the four transfer modes, because no matter what wire you load or what metal sits on your bench, the arc still has to get that wire across the gap — and how it does so decides almost everything else.

The Four Metal Transfer Modes in MIG Welding

If there is one concept that separates people who fiddle with MIG settings from people who understand them, it is transfer mode. Transfer mode describes how the wire electrode actually crosses the arc and enters the weld pool. Change it, and you change heat input, penetration, spatter, bead shape, and the positions you can weld in. There are four modes, and most MIG machines you will encounter can run at least two of them.

1. Short-Circuiting Transfer (Short Arc)

Short-circuiting transfer is the mode most beginners live in. The wire touches the workpiece, a short circuit forms, the resistance heat melts the tip of the wire, the arc reignites, and the cycle repeats — between 90 and 200 times per second. Because the arc is off during part of that cycle, this mode puts the least heat into the plate of any transfer type.

That low heat is exactly why short circuit is the standard choice for sheet metal, generally 1/8 inch or thinner, and why it works in every position including overhead. It is also the mode that pairs naturally with the common 75/25 argon/CO2 blend on mild steel. The trade-offs: penetration is shallow, and running it on thick plate invites cold-lap (incomplete fusion at the toes of the bead) rather than a sound weld. Some spatter is normal, though too much usually means your voltage is low rather than the mode being wrong. Short circuit also wants a tight, consistent contact-tip-to-work distance, typically 1/4 to 1/2 inch, because stickout changes the amperage noticeably. For more on dialing in sheet-metal work, see our Aluminum MIG Welding: The Complete Practical Guide.

2. Globular Transfer

Globular transfer happens when droplets larger than the wire diameter form at the tip and cross the arc, driven largely by gravity. It runs at higher parameters than short circuit, the arc becomes erratic, and spatter is heavy — which is why most welders actively avoid it. Globular transfer is nonetheless a real-world reality: it is the mode you get with 100% CO2 on steel and the mode gas-shielded flux-cored wires tend to run in. It works on 1/8-inch material and thicker, and it tolerates a longer stickout, roughly 3/4 inch out to 1 inch. If you are welding overhead or vertical, globular is the mode you want to escape — gravity works against you.

3. Spray Transfer

Above a certain current, the metal transfer character changes abruptly: a fine spray of droplets smaller than the wire diameter streams across the arc with a steady hiss. That threshold is called the transition current, and it rises with wire diameter. Practical numbers to remember:

• .030 wire: approximately 150 amps
• .035 wire: approximately 165 amps
• .045 wire: approximately 220 amps

Getting into spray transfer also requires the right gas — at least 80 to 85 percent argon, since pure CO2 cannot support a true spray arc on most wires. In exchange you get deep penetration, a calm arc, minimal spatter, and high deposition rates. The limitation is position: spray transfer is mostly a flat and horizontal process, and it needs 1/8-inch material or thicker to survive the heat. Hobart Brothers’ transfer mode guide walks through these thresholds in more detail.

4. Pulsed Spray Transfer

Pulsed spray is the clever solution to the “I want spray transfer but my part is thin or I’m welding out of position” problem. The power source alternates between a peak current high enough to pinch off exactly one droplet per pulse and a background current low enough to maintain the arc without transferring metal. Pulse rates run from about 30 to 400 pulses per second. The result is spray-like transfer with the average heat input of a much cooler process, all-position capability, and far less spatter than globular or aggressive short circuit. The catch: it needs an inverter machine with programmable waveforms, not a basic transformer box. For a fuller look at these modern variants, continue to FABTECH’s transfer mode selection resources.

Transfer Mode Comparison at a Glance

Mode	Droplet Size	Heat Input	Typical Thickness	Position	Gas (steel)	CTWD
Short circuit	Wire-sized, via shorts	Lowest	Up to 1/8 in	All positions	75/25 Ar/CO2	1/4–1/2 in
Globular	Larger than wire	Moderate	1/8 in and thicker	Flat/horizontal	100% CO2, flux core	3/4–1 in
Spray	Smaller than wire	High	1/8 in and thicker	Flat/horizontal	≥80–85% argon	1/2–3/4 in
Pulsed spray	One droplet per pulse	Lower average	Thin to heavy	All positions	≥80–85% argon	~3/4 in

The practical takeaway: match the mode to the plate before you touch a dial. Thin sheet and out-of-position work point to short circuit or pulsed spray. Thick plate in the flat position opens up spray and globular. Once the mode is right, wire size, feed speed, and voltage become fine-tuning instead of guesswork — which is exactly where the settings section later in this guide picks up.

Advanced MIG Variants: Pulse-on-Pulse, CMT, STT, and Double-Wire Processes

Short-circuit, globular, and spray transfer can all run on a basic constant-voltage MIG machine. The processes below are different. They rely on a power source that can rewrite its arc waveform thousands of times per second to solve very specific problems, whether that’s excess heat, spatter, or deposition limits. As a general rule, pulsed MIG requires a power source with specific pulsed waveforms built in, and every variant here builds off of that level of control.

Standard Pulse MIG

Pulse MIG is the foundation for the rest of these options. The power supply alternates between a peak current, high enough to pinch a single droplet off the wire, and a background current, low enough to sustain the arc without transferring metal. By sending only one droplet per pulse, pulse MIG can achieve spray-like penetration with a much lower average heat input. This makes it far more usable out of position and on thinner material that would be prone to warping under conventional spray transfer.

There is also a practical health benefit. NIOSH identifies pulsed spray transfer as an engineering control that lowers average arc energy and reduces welding fume generation when compared to conventional axial spray. However, that fume reduction is only attainable within a specific voltage window for each wire feed speed. If the voltage is too low, spatter increases. If it’s too high, fume generation climbs again. Pulsing takes tuning, and it is not a set-and-forget feature.

Pulse-on-Pulse: The TIG-Looking Bead

Pulse-on-Pulse takes standard pulsing a step further by layering a second, lower-amplitude pulse train between the main pulses. The primary pulses handle penetration, while the secondary pulses soften the arc and reshape the ripples as the weld cools. The end result is a tightly stacked, uniform bead that can closely resemble a TIG weld. This is almost entirely a cosmetic advantage, making it most common for stainless steel in food-grade work, visible handrails, and architectural fabrication where the appearance of the weld matters just as much as its integrity.

Cold Metal Transfer (CMT)

Instead of relying on current alone to break a short circuit, Cold Metal Transfer uses the wire feeder to mechanically retract the wire at the moment of short circuit to assist with droplet detachment. This gentle separation drops heat input dramatically. For that reason, CMT excels on thin galvanized steel, automotive body panels, and thin aluminum sheet where burn-through is the biggest concern. It’s especially valuable for tasks like alloy wheel repair, where precision outweighs raw deposition. The trade-off is speed: CMT is a precision process, not one built for high-volume filler passes.

STT, Power Mode, and Controlled Short Circuit

Proprietary controlled-short-circuit processes, such as Lincoln Electric’s Surface Tension Transfer (STT) and Miller’s Power Mode, take this idea even further. Rather than leaving detachment up to inductance alone, the power source monitors each short circuit in real time and shapes the current at the exact moment it clears. This yields significantly less spatter, a stable arc at very low amperages on thin sheet, and more consistent results when stickout changes from the operator’s hand movement. These aren’t niche experiments either. Lincoln Electric’s own training curriculum teaches controlled-short-circuit variants including Power Mode and Surface Tension Transfer alongside the standard transfer modes, showing just how mainstream they have become.

AC and Variable-Polarity MIG for Aluminum

Standard MIG aluminum welding runs on DCEP, but aluminum’s tenacious oxide layer can still make the arc finicky. AC and variable-polarity MIG alternate polarity, using the cleaning half of the cycle to break up oxide and the penetration half to drive the weld into the base metal. This allows for a more stable arc on rolled or lightly dirty aluminum with cleaner bead edges. Even with the right waveform, proper aluminum surface prep is still required. For a more complete breakdown of setup parameters, our aluminum MIG welding guide covers the rest in detail.

Tandem Wire, Double-Wire, and Hot-Wire MIG

For production-scale work, tandem and double-wire MIG feed two wires into one weld pool, often from independently controlled power sources. Hot-wire variants take it a step further by resistively pre-heating an auxiliary wire before it enters the pool, allowing it to melt faster with less arc heat. Together, these methods can drastically increase deposition rates and cut down on multi-pass fills. However, they’re almost exclusively used in mechanized or robotic applications, such as shipbuilding, pressure vessel fabrication, and heavy structural shops.

Variant	Problem it solves	Typical use	Equipment needed
Pulse MIG	Heat input and out-of-position spray	Thin-to-medium steel, structural	Pulse-capable inverter
Pulse-on-Pulse	Bead appearance	Visible stainless, architectural	Programmable waveform source
CMT	Burn-through on thin sheet	Galvanized panel, thin aluminum	CMT-capable wire feeder and source
STT / Power Mode	Spatter and arc instability	Root passes, thin sheet	Controlled-short-circuit inverter
AC / variable polarity	Oxide cleaning on aluminum	Aluminum fabrication	AC-capable MIG source
Tandem / hot wire	Speed and deposition rate	Mechanized and robotic production	Dual feeds, mechanized carriage

Solid Wire, Flux-Cored, and Metal-Cored: The Electrode Types

Ask ten beginning welders what “type of MIG” they are running and most will answer with the wire they loaded into the machine. That answer points at the second way to classify this process: the electrode itself. The wire is where the arc starts, and changing it changes everything downstream — whether you need a gas bottle, whether you get slag, how much deposition you can push, how clean the bead looks, and how much heat the arc actually dumps into the plate.

There are three electrode families, and only one of them is what most people picture when they say “MIG.”

Solid Wire GMAW: The Classic MIG

Solid wire is a bare, continuously fed metal filament, usually copper-coated to improve conductivity and feeding, and it does nothing to shield itself. Every inch of weld metal needs an external shielding gas, which is why classic MIG setups always include a regulator and a cylinder. It is the cleanest, cheapest per pound, and easiest of the three to run, and it produces no slag to chip.

Carbon steel solid wires are classified under AWS A5.18 as ER70S-X. The designator reads like a code: ER means the product works as either an electrode or a rod, 70 means a 70 ksi minimum tensile strength, and S means solid. To carry that designation, the wire must meet demanding mechanical requirements — 70 ksi (roughly 480–490 MPa) tensile strength, 58 ksi yield, 22% elongation, and 20 ft-lbf of Charpy impact energy at −20°F for most classifications.

The suffix tells you the chemistry. ER70S-3 is the general-purpose choice on clean, mill-scaled steel. ER70S-6 carries higher deoxidizers — 1.40–1.85% manganese and 0.80–1.15% silicon — which lets it burn through light rust, mill scale, and oil without smuggling porosity into the weld. That tolerance is why ER70S-6 is the workhorse spool in most shops. For matched welding on higher-strength steels, ER80S-D2 steps the tensile rating up. If you venture into alloy steels and stainless fillers, our alloy steel welding electrodes guide covers the selection and safety side in detail.

Flux-Cored Wire: Two Very Different Flavors

Flux-cored arc welding uses a tubular wire — a thin steel sheath rolled around a powdered flux core. As it melts, the flux creates slag and, in some cases, its own shielding gas. FCAW is really two processes wearing one name:

• Gas-shielded flux-cored (FCAW-G) runs on DCEP (electrode positive) and relies on dual shielding — an external gas, typically CO2, plus the gas generated by the flux. The result is heavy deposition, deep penetration, and a slag cover. It dominates structural steel, heavy fabrication, and ship work, and it is a common complement to open-root pipe welding.
• Self-shielded flux core (FCAW-S) needs no gas bottle at all. It normally runs on DCEN (electrode negative), has deeper penetration, tolerates wind far better than any gas-shielded process, and gives up some smoothness for it: more spatter, more slag, and a rougher bead.

AWS classifies these tubular wires under E71T-X. The 70 is 70 ksi tensile, the 1 indicates 70 ksi class positional capability in the second digit, and the T means tubular. The trailing letter is the shielding gas: C for 100% CO2, M for an argon-CO2 mixture, and designators for self-shielded variants.

Metal-Cored Wire: The Best of Both

Metal-cored wire is also tubular, but instead of flux it is packed with metal powder. It runs exactly like solid wire — external gas, DCEP, no slag to chip — yet delivers deposition rates, bead shape, and gap-bridging ability closer to flux core. Classified as E70C-X (C for composite), it is popular on plate fabrications, out-of-position horizontal fillets, and cosmetic work where you want speed without cleanup. It is also less forgiving of a dirty liner or soft feed setup than solid wire.

Electrode	Shielding	Polarity	Slag	Best use
Solid (ER70S-X)	External gas only	DCEP	None	Clean sheet-to-plate fabrication
Gas-shielded flux core (E71T-X)	Gas + flux	DCEP	Yes	Heavy structural, high deposition
Self-shielded flux core	Flux only	DCEN	Yes	Outdoors, windy, field repairs
Metal-cored (E70C-X)	External gas only	DCEP	None	Fast plate work, gap bridging

One warning keeps repeating in shop classes: flux-cored wires run hot. They generally operate in a globular-style transfer and need noticeably more amperage than solid wire of the same diameter, which makes them a poor choice for 20-gauge sheet and a fast route to burn-through. Use them where the thickness and deposition justify the heat, not as a default substitute for ER70S-6. As Hobart Brothers’ transfer-mode guidance puts it, matching wire type to the required transfer mode is the first step before any dial is touched.

Match the electrode to the job, and the settings conversation — covered next — becomes far simpler.

Types of MIG Welding by Material: Steel, Stainless, and Aluminum

Ask ten welders “which type of MIG should I use?” and most will answer with a metal, not a transfer mode. That is because in the real world the question usually arrives as: what am I about to weld, and will it hold? The base metal quietly decides your wire, your gas, your polarity, and often your transfer mode before you ever touch the dial. A setup that runs beautifully on mild steel can ruin a stainless food tank or burn a hole through an aluminum boat panel, and the machine settings were never the real problem.

As ESAB’s technical guidance on MIG-weldable metals puts it, GMAW is genuinely versatile, but each material family has its own rules. Here is how the three big ones break down.

Mild and Carbon Steel: The Default

Steel is where MIG earns its reputation for being beginner friendly, and the wire selection is simple once you know the pattern. All common carbon steel MIG wires share the ER70S prefix: “E” for electrode, “R” for rod, “70” for 70,000 psi tensile strength, and “S” for solid. The suffix is the deoxidizer package.

• ER70S-2: titanium and zirconium deoxidizers make it the clean-metal choice, ideal for root passes and carefully prepped joints.
• ER70S-3: the general-purpose wire for clean, well-ground stock.
• ER70S-6: the workhorse, and the most widely used MIG wire in the world. Its high manganese and silicon content lets it tolerate mill scale, light rust, and everyday shop contamination without porosity.
• ER80S-D2: a step up in tensile strength for higher-strength applications. For specialty alloys, see our alloy steel welding electrodes guide.

Gas choice splits the same way. Straight CO2 is cheap and gives deeper penetration, while 75/25 argon-CO2 (C25) produces less spatter and a smoother, more attractive bead. Most shops keep both bottles on the rack. Flux-cored wire covers the heavier side of steel work, as covered in the electrode section above.

Stainless Steel: Protect the Carbon Content

Stainless is MIG-weldable but unforgiving of shortcuts. The wire family is the 300 series: ER308L for 304 stainless, ER316L for 316, and ER309L when joining stainless to plain carbon steel. The “L” stands for low carbon, and it matters because excess carbon combined with chromium causes sensitization, which is carbide precipitation at the grain boundaries that robs the weld of its corrosion resistance.

Gas is where most stainless jobs go wrong. CO2 is an oxidizer, so any significant CO2 content picks up carbon and dulls the alloy. Alleima’s shielding gas reference is a useful deeper dive here. Practical rules:

• For spray transfer: 98% argon / 2% oxygen (or 98/2 argon-CO2 at the low end of the CO2 range).
• For short-circuit on thin stainless: a helium tri-mix of roughly 90He / 7.5Ar / 2.5CO2.
• Never C25. Never straight CO2.

Aluminum: Fight the Oxide Layer

Aluminum is the material that turns a routine MIG job into a project. The core obstacle is chemistry: aluminum’s natural oxide layer melts at approximately 2,050°C, while the metal beneath melts at about 660°C. If that oxide is not removed before welding, the arc melts the aluminum while the skin on top stays solid, and you get fused-looking beads that are actually cold-lapped and weak. Proper aluminum pre-weld cleaning is not optional.

The two standard wires solve different problems:

• ER4043 (silicon-bearing): the general-purpose choice. It flows fluidly, resists cracking on 6xxx series alloys, and forgives heat. Start here.
• ER5356 (magnesium-bearing): stronger and stiffer, feeds more crisply, and anodizes to match the base metal color. Choose it when strength or finish appearance matters.

Shielding is 100% argon, full stop, with argon-helium blends added only on thick sections for extra heat. CO2-bearing gases are never acceptable on aluminum. Because the wire is soft, it bird-nests easily, so a spool gun or push-pull feeder is effectively mandatory for anything beyond very short runs. Transfer mode should be spray or pulsed rather than short circuit on most thicknesses. Our aluminum MIG welding guide walks through gun choice and settings in depth, and aluminum flux core welding covers the rare situations where a gas bottle is not practical. Related work, such as alloy wheel repair, follows the same metal-specific logic.

Quick Selection Table

Base Metal	Typical Wire	Shielding Gas	Preferred Transfer
Mild steel (clean)	ER70S-3	C25	Short circuit
Mill-scaled steel	ER70S-6	C25 or 100% CO2	Short / spray
304 stainless	ER308L	98Ar/2O2 or He tri-mix	Spray / short
316 stainless	ER316L	98Ar/2O2 or He tri-mix	Spray / short
Stainless to carbon	ER309L	98Ar/2O2	Spray
Aluminum	ER4043 / ER5356	100% argon	Spray / pulse
Copper, bronze, dissimilar	Silicon bronze / aluminum bronze	Argon or Ar/He	Short circuit

Copper Alloys and Silicon Bronze

Copper, brass, and bronze do get MIG-welded, though usually through brazing-style filler rather than full fusion. Silicon bronze and aluminum bronze fillers run at lower heat, bridge gaps well, and are the standard choice for dissimilar joints, decorative work, and repair where melting the base metal would cause distortion. They reward short-circuit transfer and careful heat control.

Shielding Gas Types for MIG Welding

Here is the part that surprises most beginners: swapping the bottle at the back of your welder changes the process more than turning any dial on the front. Gas choice, not the machine, is what flips a MIG setup from a soft short-circuit arc into a forceful spray arc, and it is also what decides whether your bead comes out clean or peppered with porosity. Shielding gas does three jobs at once — it keeps oxygen and nitrogen out of the molten pool, it shapes the arc plasma, and it controls how heat is delivered to the joint. Argon is a light, stable gas that constricts the arc and promotes fine, projected droplets; carbon dioxide is heavier, hotter on the workpiece, and cheaper, but it breaks down in the arc and produces more spatter. Every useful MIG gas is a recipe built around that trade-off, as set out in Alleima’s technical guidance on shielding the weld.

The Main Shielding Gases and What Each One Does

• 100% CO2. The budget option for carbon steel. It gives deep penetration and is the only inexpensive gas that reliably runs the globular-style transfer used on thick plate, but it produces noticeably more spatter and a rougher bead. It cannot deliver true spray transfer on most wires, and it is unusable on aluminum or stainless.
• C25 (75% Ar / 25% CO2). The beginner standard and the sheet-metal default. It supports stable short-circuit transfer from about 16 gauge up to 1/8 inch with low spatter and a smooth appearance. If you own one bottle, this is it.
• 85/15 and 90/10 Ar/CO2. The versatile middle ground. More argon means the arc starts projecting droplets, so these blends support spray transfer and still tolerate moderate out-of-position work on medium plate.
• 98% Ar / 2% O2 and 98% Ar / 2% CO2. The classic spray-arc gases for carbon steel. Oxygen or a touch of CO2 stabilizes the arc and improves wetting without the spatter penalty of higher CO2 content. As a rule, spray transfer on carbon steel needs roughly 80% argon or higher — the thresholds are covered in Fabtech’s transfer mode selection guide.
• Helium tri-mix (90He / 7.5Ar / 2.5CO2). A short-circuit gas for stainless. Helium adds arc heat and travel speed, while the low CO2 content limits carbon pickup and the intergranular corrosion that follows sensitization.
• 100% argon. Required for aluminum. Nothing else works; CO2 reacts with aluminum and produces a gross, oxidized weld. Argon/helium blends add penetration on thick aluminum sections — a topic covered in depth in our aluminum MIG welding guide.

Gas	Best for	Typical transfer mode
100% CO2	Thick carbon steel, cost-driven work	Short circuit / globular
C25	Sheet and general fabrication	Short circuit
90/10 or 98/2 Ar mix	Medium-to-thick steel, flat position	Spray
90He/7.5Ar/2.5CO2	Stainless short circuit	Short circuit
100% Ar (or Ar/He)	Aluminum, thick sections	Spray or pulsed spray

Flow Rate: Where Most Porosity Problems Start

For solid wire MIG, a typical recommended flow is 15–25 L/min (32–53 CFH), measured at the gun outlet rather than at the regulator. A practical rule of thumb from industrial gas guidance is that flow in liters per minute should roughly equal the gas cup’s internal diameter in millimeters, then adjusted upward for drafts. Pre-flow lets gas establish before the arc strikes; post-flow keeps the crater protected while it solidifies, and many inverter machines set it automatically based on arc time.

More flow is not more protection. Excessive velocity creates turbulence at the nozzle that actually pulls surrounding air into the shield, increasing porosity just as surely as a leaky liner or a too-low setting would. If your bead is porous with the regulator turned high, turn it down before you start hunting for other causes.

Wind is the practical enemy of every gas-shielded process. A light breeze that you barely feel is enough to blow the shield off a short-circuit arc, and no regulator setting fixes it. That single limitation is why outdoor and windy fabrication pushes so many people toward self-shielded flux core, which carries its own protection inside the wire. If you are working outdoors regularly, plan the wire choice around the weather rather than fighting it with flow rate. As Hobart Brothers’ transfer mode tips put it, the gas-metal arc only behaves when the atmosphere around it stays put.

MIG vs. TIG vs. Stick: Choosing the Right Welding Process

Behind nearly every search for “types of MIG welding” is a prior question: is MIG even right for this job? Before you agonize over ER4043 versus ER5356 or debate 90/10 versus 98/2 gas, compare MIG (GMAW) with its two main rivals, TIG (GTAW) and stick (SMAW), plus cousin flux-cored arc welding (FCAW). Picking wrong costs rework, consumables, and patience; picking right makes the settings guidance later in this article feel easy.

MIG vs. TIG: Control Versus Speed

TIG is the fine-detail instrument of arc welding. The operator controls heat with a foot pedal while feeding filler rod separately, so you can pause, reposition, and modulate heat mid-joint in a way no wire process allows. The result is the cleanest bead a handheld arc produces, with tight control of the heat-affected zone. That is why TIG is the default for pipe root passes, thin stainless, aerospace work, and any joint where the alloy is sensitive to overheating.

The trade-offs are real. TIG is slow, needs meticulous joint prep, and demands a steep learning curve because you coordinate heat, travel speed, filler addition, and shielding gas at once. Deposition is a fraction of MIG’s, so long production runs get expensive. For aerospace-grade precision or cosmetic welds on visible aluminum, TIG is the reference standard; see aerospace TIG welding standards and training for what that discipline involves.

MIG wins on speed, deposition efficiency, and how quickly a beginner lays a sound bead. Short-circuit MIG tolerates thinner material and out-of-position work with far less finesse than TIG. Pulsed MIG is the compromise, giving some of TIG’s control at wire-process speed.

MIG vs. Stick: The Outdoors Test

Stick welding is the oldest of the three and remains undefeated in one category: hostility. Wind, rain, rust, paint, poor fit-up, a crawlspace, a pipeline in a ditch, a decade-old farm implement. The flux coating on the electrode makes its own shielding gas and slag, so there is no gas bottle to protect and no gas envelope for a breeze to destroy. That is why SMAW still owns field and pipeline repair, covered in the advantages of stick welding.

Stick is also maximally portable: a power source, a stinger, and a box of rods. The costs are slag and spatter everywhere, weak thin-sheet performance from higher heat input, and slower production than MIG. Thin material belongs to MIG and TIG; heavy dirty repair belongs to stick. For rods that work overhead and vertical, our all-position welding rod guide breaks down options by position.

MIG vs. Flux Core: Same Machine, Different Personality

Flux-cored wire (FCAW) uses the same gun and wire-feed architecture as MIG but swaps solid wire for a tubular wire filled with flux. The payoff is higher deposition and much better wind tolerance in self-shielded mode, the natural pick for heavy structural steel outdoors. Against that: more spatter, mandatory slag removal, and heat input that makes thin sheet a losing proposition. Gas-shielded MIG wins on appearance, cleanup, and thin material; flux core wins on deposition, penetration, and weather.

Side-by-Side Comparison

Factor	MIG (GMAW)	TIG (GTAW)	Stick (SMAW)	Flux Core (FCAW)
Typical deposition rate	High (roughly 3–10 lb/h)	Low (roughly 0.5–3 lb/h)	Moderate (2–6 lb/h)	Highest (5–15+ lb/h)
Position capability	All-position (short circuit, pulsed); spray mostly flat/horizontal	All-position with skill	All-position	All-position (self-shielded especially)
Wind tolerance	Poor (needs gas)	Poor (needs gas)	Excellent	Good to excellent
Joint prep demands	Low to moderate	Very high	Low (tolerates fit-up)	Moderate
Learning curve	Gentle	Steep	Moderate	Gentle to moderate
Cleanup	Minimal spatter, no slag	Cleanest overall	Heavy slag and spatter	Slag removal required
Best fit	Thin-to-medium fabrication, production	Thin, cosmetic, critical-alloy, root passes	Field repair, pipe, dirty/outdoor	Heavy structural outdoors

Deposition figures are typical ranges and vary with wire diameter, transfer mode, and polarity; verify numbers for your procedure against American Welding Society process guidance (AWS process handbook).

Decision Rules That Actually Work

• Pick TIG when the joint is thin, appearance matters, the alloy is heat-sensitive (stainless, aluminum, nickel, titanium), or a pipe root pass depends on it.
• Pick stick for field repairs, dirty or rusty material, windy outdoor sites, and anywhere carrying a gas bottle is impractical.
• Pick MIG for productivity and repeatability: thin-to-medium fabrication, sheet metal, production runs, and anyone learning who wants results fastest.
• Pick flux core for heavy structural steel outdoors and thick sections where deposition and penetration beat appearance.

Most certified fabricators do not pick one process and stop; they qualify several against written welding procedure specifications (WPS) and match process to joint. A pressure vessel shop might run pulsed MIG on sheet skins, TIG for root passes, stick for field tie-ins, and flux core for heavy attachments, each under its own qualified procedure and performance qualification.

Match the process to your material, thickness, position, and environment first. Once that decision is made, the settings guidance later in this article tells you how to dial the machine in.

Settings, Common Mistakes, and Troubleshooting by MIG Type

Everything covered so far only becomes useful once you can translate it into knob turns. The good news: every MIG variant is dialed in with the same four-step sequence, and once you internalize the order, switching between short circuit, spray, pulsed, or flux-cored feels routine rather than guesswork.

The Four-Step Setup Order

1. Pick the wire diameter first. Wire size is dictated by the material in front of you, not by preference. Thinner wire welds thinner metal because it needs less amperage to melt off:

Wire diameter	Typical material range
.023 in (0.6 mm)	22–18 gauge sheet
.030 in (0.8 mm)	18 gauge to 1/8 in, all-purpose light fabrication
.035 in (0.9 mm)	General purpose, 1/8 in and heavier
.045 in (1.2 mm)	Plate work, structural and heavy fabrication

2. Set wire feed speed, which really means setting amperage. On a constant-voltage machine, amperage is largely a slave to wire feed speed: feed more wire and the arc must melt more metal per second, so current climbs. Set this before you touch voltage.

3. Trim voltage by ear and by eye. Add voltage until the arc stops stubbing and the bead wets out smoothly. In short-circuit mode you are listening for a consistent frying-bacon crackle; a harsh, popping snap means too little voltage, while a smooth hum with excessive hiss means too much. Manufacturer charts give you a starting point, but sound and bead shape are the final arbiter, as outlined in Hart Brothers’ transfer mode guidance.

4. Set contact tip-to-work distance (CTWD). Stickout changes resistance, which changes actual current:

• Short circuit: 1/4 to 1/2 inch
• Pulsed spray: about 3/4 inch
• Globular: 3/4 to 1 inch

Polarity, Feed Components, and Heat Control

Polarity is the single most common setup error. Solid wire and gas-shielded flux core run DCEP (electrode positive), while self-shielded flux core typically runs DCEN (electrode negative). Reverse it and you get a wandering arc with massive spatter that no amount of voltage adjustment will fix. Drive-roll tension should pinch the wire firmly enough to push it without crushing it; overtightening flattens the wire and causes feed surges. A dirty or deformed liner adds friction that shows up as erratic arc and bird-nesting, so clean wire and liner maintenance belong in the same routine.

Inductance control, found on most modern machines, changes how quickly current rises during each short circuit. Low inductance gives a crisp, punchy arc with less penetration; high inductance softens the transfer, reduces spatter, and lets the puddle wet out. On thick sections, preheat of 150–300°F helps avoid cracking on higher-carbon and alloy steels, where hydrogen and rapid cooling are real risks. Miller’s GMAW guidelines include recommended CTWD and parameter ranges worth keeping at the machine.

The Troubleshooting Matrix

Symptom	Likely cause	Fix
Excessive spatter	Voltage too low, wrong gas, dirty metal, wrong polarity	Trim up voltage, correct gas, clean the joint, verify polarity
Porosity	Gas leaks, low flow, wind, contaminated wire	Check connections, raise flow modestly, shield the area, replace damp wire
Incomplete fusion	Too cold, travel too fast, poor technique on thick stock	Raise wire speed, slow down, increase preheat, adjust work angle
Burn-through	Too much heat on thin sheet	Drop wire diameter, lower feed speed, stitch-weld, increase travel speed
Bird-nesting / burn-back	Feed problems, wrong drive rolls, excessive stickout	Match rolls to wire, relieve tension, shorten CTWD, replace liner
Distortion	Excessive total heat input	Use short circuit or pulsed transfer, balance welds, use tack sequences

Mistakes That Are Really Type Errors

Most recurring shop mistakes come from running the wrong MIG type for the job:

• Using C25 or straight CO2 on stainless, which causes carbon pickup and sensitization.
• Running gas-shielded flux core on 20-gauge sheet, where its globular-style transfer simply burns through.
• Using spray arc on 16 gauge, where the heat input overwhelms the material.
• Welding aluminum through a steel liner with V-groove drive rolls, which shaves soft wire and jams the feeder. The aluminum MIG setup requires U-groove rolls, a non-metallic liner, and light tension, ideally with a spool gun or push-pull system.
• Skipping the WPS on code work. Procedure qualification is not optional in certified shops.

Safety, Fume Control, and How to Choose Your First MIG Setup

Every type of MIG welding covered in this guide shares one non-negotiable trait: an arc hot enough to melt steel, ultraviolet light intense enough to sunburn skin through a denim jacket, and a plume of metal fume you would never knowingly breathe. Picking a process is partly a health decision, because the transfer mode, electrode, and gas you choose also decide what ends up in your lungs.

The Rules That Govern Every Arc You Strike

Three documents define the compliance landscape in the United States:

• AWS Z49.1, Safety in Welding, Cutting and Allied Processes — the consensus standard for ventilation, protective equipment, and fire prevention. AWS publishes it as a free download, and it is the first document any shop owner should read.
• OSHA 29 CFR 1910 Subpart Q — the enforceable federal standard for welding, cutting, and brazing in general industry. Within it, OSHA’s welding, cutting, and brazing requirements and 1910.252 set hot-work rules covering ventilation, fire watch, and combustible control.
• NFPA 51B — the standard for fire prevention during hot work such as welding, cutting, and grinding.

The most-cited practical rule from these standards: remove or tightly cover combustibles within roughly 35 feet (10.7 m) of the arc, and keep a charged extinguisher plus a trained fire watch on site for at least 30 minutes after the arc goes out. It sounds excessive until a hidden paper-filled wall cavity starts smoldering behind you.

What Welding Fumes Actually Do to You

NIOSH research associates welding fume exposure with a long list of adverse effects: metal fume fever (the flu-like chills and nausea that follow breathing zinc oxide from galvanized steel), chemical pneumonitis, chronic bronchitis, and measurably reduced pulmonary function. More sobering, evidence summarized by NIOSH suggests welders face roughly a 40% increase in relative risk of developing lung cancer because of their work.

Fume composition depends on the type of MIG welding and the material under the arc:

• Stainless and nickel alloys are the worst offenders, generating hexavalent chromium and nickel compounds. If stainless is on your schedule, fume extraction is not optional.
• Coated metals — galvanized, cadmium-plated, or lead-painted steel — release zinc, cadmium, or lead fume. OSHA’s welding safety guidance warns against welding coated or contaminated metal without proper controls, and cadmium-coated work is effectively off-limits without industrial hygiene oversight.
• Carbon steel with solid wire and argon/CO2 is the least hazardous common combination, though far from harmless.

Controls follow a strict hierarchy laid out in AWS Z49.1: engineering controls first (general ventilation, then a local exhaust or extraction arm positioned near the arc), then administrative controls and work practices, then respiratory protection, fitted and user-tested. A $300 fume extractor earns its keep faster than any other accessory in the shop.

Arc Radiation, Shock, and Confined Spaces

The MIG arc emits ultraviolet and infrared radiation that causes arc flash (painful keratitis, essentially a corneal sunburn) and arc burn on exposed skin within minutes. An auto-darkening helmet in shade 10 to 13 for short-circuit work, a flame-resistant jacket, gauntlets, and no exposed ankles are baseline. Electrical shock deserves respect too: CV MIG machines run open-circuit voltages around 80 volts, enough to lock you up in wet conditions or through damaged leads and a bad ground. Inspect the gun liner, contact tip holder, and ground clamp before every session.

Confined spaces add permit requirements, atmosphere monitoring, forced ventilation, and a dedicated attendant outside. Never weld alone in a tank, trench, or crawl space. And never use a MIG welder for structural code work without qualifying the procedure; a properly specified filler metal and documented procedure is what keeps an inspection from turning into a rejection.

Choosing Your First MIG Setup

With safety handled, buying a first machine comes down to five questions:

1. Which transfer modes does it run? Short circuit is the floor. A pulse-capable inverter with adjustable inductance covers nearly everything else, and the manufacturer’s GMAW parameter guidelines are worth reading before you buy.
2. What is the duty cycle? A hobby-class 180 A machine might be rated 20 to 30 percent at full output; a shop machine should hold 100 percent at its rated current.
3. Does it run both gas MIG and flux core? A dual-voltage, dual-process machine lets you gas-weld in the shop and self-shield outdoors.
4. What wire range does it feed? Look for .023 to .045 inch capability, with changeable drive rolls.
5. Which materials will you actually weld? Steel-only keeps things simple. Adding aluminum means a spool gun or push-pull feeder, and aluminum MIG has its own setup demands. Budget for a quality shielding gas supplier from day one; the wrong bottle is as limiting as the wrong machine.

Conclusion: Match the Type to the Job

“Different types of MIG welding” is not one list — it is four: transfer mode, machine variant, electrode type, and base material. Short circuit or pulse for thin and out-of-position work; spray or globular for thick plate. Solid wire, gas-shielded flux core, self-shielded flux core, or metal-cored wire, each with its own polarity and amperage window. Mild steel, stainless, or aluminum, each with its own filler and gas. Name the axis a job sits on, and the settings, the safety controls, and the equipment fall into place.

Frequently Asked Questions

What are the main types of MIG welding?

MIG welding is usually classified four ways: by metal transfer mode (short circuit, globular, spray, and pulsed spray), by process variant (pulse-on-pulse, CMT, STT, tandem wire), by electrode type (solid wire, gas-shielded flux core, self-shielded flux core, metal-cored), and by the material being welded (mild steel, stainless, aluminum, copper alloys). Most confusion about ‘types of MIG’ disappears once you identify which axis someone is asking about.

Which MIG transfer mode is best for beginners?

Short-circuiting transfer is the best starting point. It runs at low voltage and wire feed speed, works in all positions, handles material 1/8 inch and thinner, and is forgiving of technique errors. Most entry-level machines run it on 75/25 argon/CO2 with ER70S-6 wire.

What is the difference between MIG and flux-cored welding?

Solid-wire MIG uses a bare wire and external shielding gas, producing little to no slag and clean beads. Flux-cored wire (FCAW) has flux inside the tubular wire, runs hotter, produces higher deposition and a slag layer that must be chipped off, and comes in gas-shielded and self-shielded versions — the self-shielded type tolerates wind and outdoor work far better than gas-shielded MIG.

What shielding gas should I use for MIG welding?

For mild steel short-circuit work, 75% argon / 25% CO2 is the standard; 100% CO2 is cheaper and deeper-penetrating but spattery. Spray transfer needs argon-rich gas such as 90/10 Ar/CO2 or 98/2 Ar/O2, stainless typically uses 98/2 Ar/O2 or a helium tri-mix, and aluminum always uses pure argon (or argon/helium on thick sections).

What MIG wire should I use for mild steel, stainless, and aluminum?

For mild steel, ER70S-6 is the general-purpose choice, with ER70S-2 or ER70S-3 for cleaner work. For stainless, match the alloy: ER308L for 304, ER316L for 316, ER309L for dissimilar joints. For aluminum, use ER4043 for general 6xxx work or ER5356 when you need more strength or anodize color matching.

Can MIG weld in all positions?

Yes — but only certain types. Short-circuit transfer and pulsed spray transfer are genuinely all-position. Conventional spray transfer is mostly limited to flat and horizontal because of its large fluid weld pool, and globular transfer, while technically usable out of position, is unpleasant and prone to sagging and spatter.

What thickness can MIG welding handle?

MIG covers an enormous range, from roughly 22-gauge sheet with .023 wire in short-circuit mode up to heavy plate with .045 or larger wire in spray or pulsed transfer. Thin material needs small wire and low heat; anything over about 1/8 inch generally wants spray-family transfer to guarantee fusion.

Why does my MIG weld spatter, and how do I fix it?

Spatter usually comes from voltage that is too low for the wire feed speed, an incorrect or contaminated shielding gas, excessive contact tip-to-work distance, dirty base metal, or wrong polarity. Raise voltage until the bead smooths out, verify gas composition and flow, clean the joint, and check that solid wire is running DCEP. Pulsed MIG and metal-cored wire both reduce spatter further.

Do I need a special machine for pulsed MIG welding?

Yes. Pulsed spray transfer requires a power source with programmable waveform control — basic constant-voltage transformer machines cannot produce it. Inverter-based MIG machines with pulse programs cost more, but they let you spray-transfer thinner material, weld out of position, and cut heat input and fume generation.

Is MIG welding safe for beginners at home?

MIG is one of the safer arc processes to learn, but it is not risk-free. Wear a proper filter helmet, flame-resistant clothing, and insulating gloves; ventilate or use local exhaust because welding fumes are hazardous; keep combustibles about 35 feet away or covered; and never weld on closed containers or coated metals without proper precautions and respiratory protection.