What types of metals can you MIG weld?
April 22, 2024
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What types of metals can you MIG weld?

MIG welding is one of the most versatile arc welding processes available — capable of joining a wide range of metals and alloys across a broad thickness range. But the metals you are welding directly determine the wire type, shielding gas, transfer mode, and technique required. Using the wrong combination of consumable and gas for a given base metal will produce poor results regardless of operator skill. This guide covers the most common base metals for MIG welding, what makes each one distinctive, and the key considerations for each.

For a full introduction to how MIG welding works, transfer modes, and equipment selection, see our article on what is MIG welding.

Steel: Carbon Steel and Mild Steel

Carbon steel and mild steel are the most commonly MIG welded materials globally. Their weldability is generally excellent — they are tolerant of a range of parameters and shielding gases, and a wide range of filler wires is available.

Key considerations for MIG welding carbon and mild steel:

  • Filler wire — for general structural and fabrication work, ER70S-6 classification wires (such as OK AristoRod 12.63) are the standard choice. The higher silicon and manganese content improves tolerance to mill scale and light surface contamination. For cleaner base materials, ER70S-3 classification (such as OK AristoRod 12.50) provides excellent mechanical properties
  • Shielding gas — 75–80% Ar / 20–25% CO₂ (M21 classification) is the standard for most mild and carbon steel MIG welding, giving good arc stability, low spatter, and acceptable penetration. Pure CO₂ increases penetration and reduces cost but produces more spatter
  • Transfer mode — short circuit for thin sheet and positional work; spray or pulse for thicker sections and flat/horizontal welding where higher deposition rates are needed
  • Wire feed speed — verify wire feed speed settings against the manufacturer's recommended parameters for the wire diameter and material thickness. Incorrect wire feed speed is the most common cause of poor results on mild steel

For high-strength carbon and low-alloy steels, filler metal selection requires more careful attention — the wire must meet the mechanical property requirements of the base material. See our welding consumables selection guide and our article on low manganese filler metals for heavy industrial applications.

Stainless Steel

Stainless steel's resistance to corrosion and oxidation makes it essential in food processing, pharmaceutical, chemical, and marine applications. MIG welding stainless steel is well established but requires specific consumable and gas combinations to maintain corrosion resistance in the finished weld.

Key considerations for MIG welding stainless steel:

  • Filler wire — the filler wire must match or closely match the alloy type of the base material. Grade 304 base material is typically welded with 308L wire; grade 316 with 316L wire. The 'L' designation indicates a low-carbon variant that reduces the risk of sensitisation (carbide precipitation at grain boundaries) in the heat-affected zone
  • Shielding gas — pure argon or argon with a small addition of CO₂ or oxygen (typically 98% Ar / 2% CO₂) is used for stainless steel MIG welding. Higher CO₂ levels oxidise the weld metal surface and impair corrosion resistance. Do not use the same M21 gas used for mild steel on stainless steel
  • Heat input control — excessive heat input causes sensitisation and distortion. Use the minimum heat input necessary for the joint thickness and keep interpass temperature controlled
  • Cleanliness — stainless steel welds must be made on clean, contaminant-free surfaces. Cross-contamination from carbon steel tools, wire brushes, or grinding discs can introduce corrosion sites. Use dedicated tooling for stainless steel work

For dissimilar material joints involving stainless steel, or for duplex and super-duplex stainless steels, see our article on specialised filler metals for exotic alloys.

Aluminium

Aluminium MIG welding is widely used in automotive, marine, aerospace, and general fabrication. The process works well but requires different equipment setup and technique compared to steel — aluminium's lower melting point, higher thermal conductivity, and tendency to form a refractory oxide layer all require careful management.

Key considerations for MIG welding aluminium:

  • Filler wire — the most common aluminium MIG filler wires are OK Autrod 4043 (AlSi, general purpose, good fluidity, lower crack sensitivity) and OK Autrod 5356 (AlMg, higher strength, anodising-compatible). The choice depends on the base alloy series, service conditions, and whether the component will be anodised. See our aluminium filler alloy selection guide for full guidance
  • Shielding gas — pure argon is standard for aluminium MIG welding. For thicker sections, argon/helium mixtures increase heat input and penetration. Do not use CO₂-containing gases on aluminium. See our article on argon vs helium for aluminium welding
  • Wire feeding — aluminium wire is softer than steel wire and more susceptible to birdnesting and burn-back. A push-pull torch system is strongly recommended for reliable feeding, particularly on cable runs over 3–4 metres. Non-metallic liners (Teflon or nylon) must be used. See our article on feedability and wire delivery in aluminium MIG welding
  • Pre-weld cleaning — the natural oxide layer on aluminium must be removed before welding using a stainless steel wire brush (dedicated to aluminium only) or chemical cleaning. The oxide layer melts at approximately 2,050°C — far above aluminium's melting point of 660°C — and will cause fusion defects if not removed
  • Travel speed — aluminium's high thermal conductivity means heat dissipates rapidly. Higher travel speeds than steel are typically required to prevent excessive heat build-up on thinner sections, while pass sequencing and interpass cooling require attention on thicker sections
  • Transfer mode — spray transfer is standard for aluminium MIG welding. Pulse MIG gives better control on thinner sections and is well suited to aluminium, reducing heat input while maintaining good fusion

For troubleshooting common aluminium MIG welding problems, see our article on aluminium MIG troubleshooting at the arc.

Copper and Copper Alloys

Copper's high thermal conductivity — approximately eight times that of mild steel — means heat dissipates very rapidly from the weld area, making fusion more difficult to achieve. MIG welding of copper and copper alloys (bronze, brass, copper-nickel) is possible but requires higher heat input and preheat on thicker sections to overcome the thermal conductivity disadvantage. Filler wire selection must account for the specific alloy being welded — copper-silicon (CuSi3) and copper-aluminium (CuAl) wires cover most common applications. Argon shielding gas is standard.

Nickel and Nickel Alloys

Nickel alloys — including Inconel, Hastelloy, and Monel — are used in high-temperature and highly corrosive service environments where standard steels and stainless steels cannot perform. MIG welding of nickel alloys requires matched or compatible nickel-based filler wires, controlled heat input to prevent hot cracking, and strict contamination control. Argon shielding gas or argon/helium mixtures are used. For detailed guidance on filler metal selection for nickel alloys, see our article on specialised filler metals for exotic alloys and the Exaton nickel alloy filler range.

Titanium

Titanium is highly reactive at elevated temperatures and will absorb oxygen, nitrogen, and hydrogen from the atmosphere if shielding is inadequate — causing severe embrittlement of the weld. While MIG welding of titanium is possible, TIG (GTAW) with comprehensive atmospheric shielding (trailing shields, back purging, and pure argon at 99.999%) is the preferred process for most titanium applications. For guidance on titanium welding and contamination control, see our article on welding exotic alloys.

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