Argon is the workhorse shielding gas of modern welding. Across TIG, MIG, plasma welding, and a range of specialised processes, argon‘s inert nature protects the molten weld pool from atmospheric contamination, producing cleaner welds, more stable arcs, and less spatter. This guide covers the main applications of argon in welding processes: which processes use argon welding gas, how it is used pure and in blends, what each common mix is for, how argon shield gas compares with CO2, and practical guidance on matching an argon shielding gas cylinder to the job.
Why Argon Is the Standard Shielding Gas for Welding
Argon makes up just under 1% of the atmosphere and is produced industrially by the cryogenic distillation of air. As a shielding gas it has three properties that matter to welders.
It is fully inert. Argon does not react with molten metal at any temperature, so it cannot oxidise the weld, alter its chemistry, or introduce porosity. That makes it suitable across almost every common weldable metal: carbon steel, stainless steel, aluminium, titanium, copper, nickel alloys, and magnesium.
It is heavier than air. At 1.38 times the density of air, argon settles over and around the weld pool and stays there, which gives better coverage than lighter gases like helium. In open-air conditions with a reasonable flow rate, argon maintains a clean shielding envelope.
It produces a stable, low-turbulence arc. A stable arc means consistent penetration, predictable bead profile, and less rework. These are the reasons argon shielding gas is the default for TIG welding globally and the primary component of nearly every MIG blend used on carbon steel.
Argon in TIG Welding
TIG welding (Gas Tungsten Arc Welding) uses a non-consumable tungsten electrode with a separate filler rod fed in by hand. The weld pool has no flux and no slag, so shielding gas is the only thing protecting it. Argon is the standard.
Pure argon is used for most TIG work: carbon steel, stainless, titanium, copper, and nickel alloys on DC polarity, and aluminium on AC (the AC current cleans the oxide layer as argon shields the pool). Flow rates typically sit between 7 and 15 litres per minute depending on joint geometry, cup size, and position, with a short post-flow as the weld cools to stop the hot metal oxidising.
For aerospace, pharmaceutical and nuclear-grade tubing, 100% argon is usually a specification requirement and cannot be substituted. For thicker aluminium or faster production speeds, an argon and helium shielding gas blend is often used to lift penetration and heat input. The argon helium shielding gas approach keeps argon’s clean shielding while adding helium’s higher arc voltage.
For stainless steel TIG on the inside of tubing, a small percentage of hydrogen (argon/H2, typically 2-5%) is added to argon to produce a narrower, cleaner bead. This mix is not suitable for ferritic or carbon steels because of hydrogen embrittlement risk.
Argon in MIG Welding
MIG welding (Gas Metal Arc Welding) uses a continuously fed consumable wire and a shielding gas delivered through the torch. Pure argon is standard for MIG on non-ferrous metals (aluminium, copper, nickel alloys). On carbon steel it is almost always blended.
The usual blends for steel MIG in Australian workshops:
80% argon / 20% CO2 (PacShield 8020). A reliable all-rounder for general carbon steel fabrication, FCAW, and metal fabrication. Good penetration, controllable spatter, stable short-circuit and spray transfer.
92% argon / 5% CO2 / 2% oxygen (PacShield 52 argon mix). A tri-mix designed for MIG welding across stainless steel, mild steel, and aluminium alloys. Delivers arc stability and reduced spatter, which is why it is common in structural and automotive fabrication.
92% argon / 8% CO2 (generic blend). Lower spatter, cleaner welds, best on thin gauge material and where weld appearance matters.
98% argon / 2% oxygen (generic blend). Stainless MIG in spray transfer mode. The small oxygen addition improves arc stability and fluidity of the weld pool.
The trade-off is straightforward: more CO2 gives more heat and penetration but more spatter; more argon gives a cleaner, narrower bead with less cleanup but a cooler, shallower weld. Most workshops settle on 80/20 as the workhorse blend and keep a cylinder of pure argon for non-ferrous work.
Argon in Plasma Arc Welding and Cutting
Plasma arc welding (PAW) and plasma cutting both use argon as the plasma-forming gas, superheated and ionised to form the constricted arc. Shielding gas around the plasma is also typically argon or an argon/hydrogen blend. Plasma welding gives a narrow weld profile with precise heat control, so it is common in precision tubing, aerospace, electronics, and thin stainless work. Plasma cutting with argon/hydrogen is the standard approach for cutting stainless steel and aluminium because the hydrogen adds heat while argon shields the cut face.
Common Argon Blends and What Each Is For
Pacific Gas and other suppliers stock a range of pre-blended argon mixes because mixing gases accurately on-site is impractical. The useful blends to know:
Argon/CO2 (various ratios, 5% to 25% CO2). Primary MIG gas for carbon steel fabrication. Ratio choice depends on material thickness, transfer mode, and bead cosmetic requirements.
Argon/oxygen (typically 1-5% O2). Spray transfer MIG on stainless steel. Oxygen stabilises the arc and improves bead wetting.
Argon/helium (various ratios, 25% to 75% helium). TIG and MIG on thicker aluminium, copper alloys, and where deep penetration is needed. Helium increases heat input without altering the chemistry of the weld.
Argon/hydrogen (2-5% hydrogen). Austenitic stainless TIG, plasma cutting of stainless and aluminium. Not for carbon steel.
Argon/helium/CO2 tri-mix. Stainless MIG where both high penetration and low spatter are required.
Argon Shielding Gas vs CO2: When to Use Each
The CO2 shielding gas vs argon choice is a common one for MIG welders setting up a workshop, and there is no universally right answer, only a right answer for a given job.
Pure CO2 is the cheapest shielding gas available and produces hotter penetration than argon. It only runs in short-circuit transfer mode, it spatters heavily, and bead appearance is rougher. It remains popular for heavy plate carbon steel where speed and penetration outweigh cosmetics.
Pure argon gives the cleanest weld and the most stable arc but is more expensive and produces shallower penetration on steel. It allows spray transfer mode, which is faster for positional welding and thicker material.
An argon/CO2 blend combines the best of both: stable short-circuit or spray transfer, controllable penetration, acceptable bead cosmetics, manageable spatter. For most Australian fabrication shops running carbon steel MIG, 80% argon / 20% CO2 is the default choice, with pure CO2 reserved for the cheapest bulk work and pure argon kept for non-ferrous.
Matching an Argon Shielding Gas Cylinder to the Job
Argon and argon-blend cylinders come in a range of sizes, and choosing correctly saves downtime.
Size D (1.7m3). Portable, the choice for mobile welders, site repair work, and hobbyists. A TIG welder running weekend projects will typically get weeks of use from one D-size argon cylinder.
Size E (4.8m3). Workshop standard for daily-use fabricators, suiting most single-welder setups for moderate continuous operations.
Size G (10.5m3). Production capacity for shops with multiple stations or high-duty cycles.
Bulk or liquid argon. Large manufacturing sites, automotive production, aerospace, and any facility running multiple welders around the clock step up to bulk liquid argon with on-site vaporisation.
Pacific Gas offers two supply models. Rental suits high-volume users: the customer doesn’t own the cylinder, and empties are swapped for full ones at the local distributor. Customer-owned suits lower-volume users who would rather not rent: the customer owns the cylinder outright and can exchange it at any stockist that sells customer-owned cylinders, similar to BBQ swap bottles.
Frequently Asked Questions
What is argon shielding gas?
Argon shielding gas is pure argon (or an argon-based blend) used to protect the molten weld pool from atmospheric oxygen and nitrogen during welding. It is the primary shielding gas for TIG welding and the main component of most MIG shielding blends.
Is argon the best shielding gas for welding?
For TIG welding on most metals, yes: argon is the standard. For MIG on carbon steel, an argon/CO2 blend is usually better than pure argon. For MIG on non-ferrous metals, pure argon is standard. The right answer depends on the process and the metal.
Can I use CO2 instead of argon for welding?
For MIG welding on carbon steel, yes, pure CO2 works but produces more spatter and a rougher bead. It cannot be used for TIG (which needs an inert gas) or on non-ferrous metals. For most fabrication, an argon/CO2 blend is the better compromise.
What is argon welding gas made of?
Argon welding gas is pure argon (around 99.995% purity for welding grade). Industrial argon is produced by the cryogenic distillation of atmospheric air, where argon is separated from nitrogen and oxygen based on boiling point.
How long does an argon cylinder last?
It depends on size and flow rate. A D-size argon cylinder (1.7m3) at 10 L/min running flow delivers around three hours of continuous arc time, typically two to four months for a hobbyist. An E-size (4.8m3) at the same flow lasts around eight hours of arc time, or roughly two to three weeks for a daily-use fabricator.
What is the difference between argon and argon/helium shielding gas?
Pure argon gives a stable arc and clean shielding but lower heat input. Argon/helium blends raise the arc voltage and heat, giving better penetration on thicker material (especially aluminium and copper). Pure argon is the default; argon/helium is specified where penetration or travel speed matters.
Argon and Argon Blend Supply for Welding Workshops
Pacific Gas supplies argon and pre-blended argon mixes (including PacShield 8020 and PacShield 52 argon mix) in cylinders through a national distributor network. Cylinders are available in sizes D, E and G across rental and customer-owned options.
For workshops setting up shielding gas supply, find a distributor in your area or contact Pacific Gas. For aluminium-specific guidance, the argon for aluminium welding article covers TIG and MIG settings for aluminium in more detail.
