Basics of MIG Wire Selection – A Comprehensive Guide for Welders

The welding wire used in MIG welding plays an important role in deciding the quality and performance of your weld. No matter how strong or durable the metal alloy you weld on, the wire that you select determines the overall welding experience. The increased cost of raw materials, higher energy rates, transportation costs, and shipping competition. The welding process and type of metal used in the welding process determine the wire that is compatible with your welding process. Below is a guide to MIG wire selection.

Basics to the Ideal MIG wire selection

  • Analyzing your metal: The three most common metals used for MIG welding are carbon steel, stainless steel, and aluminum.
  • Match your wire: Generally when you weld with ideal wire conditions, the type of welding wire used will be the same as the metal type. For example, stainless steel works well with stainless steel wires, carbon steel metal sheets with carbon steel wires, and so on.
  • Don’t avoid Mixed-metals: MIG wires commonly have a mixture of metals along with the type of metal they weld on. Manganese, silicon, and titanium are added to wires to make the welds stronger and more durable with minimal porosity and oxidation.
  • Thickness Matters: Based on the thickness of your base metal, you will determine the thickness of the welding wires used. The wire packaging will include a chart to analyze the wire thickness for the metal you use.
MIG Wire

When we look at the total welding costs, the cost of the wire used is as low as 4% of the total cost and this is because the overall cost is expensive enough just for labor and overhead costs. Producing a sound weld is majorly dependent on the MIG wire that you select and the most commonly used wire thicknesses range from 0.023 – 0.045 especially for heavy-industry purposes.

MIG wire manufacturers nowadays make wires that have an addition of manganese, silicon, and titanium along with the primary metal used. Creating a stable arc by deoxidizing the weld is the primary reason for the inclusion of several elements in the MIG wire.

Similarly, steel wires have some amount of copper coated on them also to avoid oxidation. It is recommended to ask your wire supplier or looking up at the chart included in the welding machine that can provide you all the information to choose the right kind of welding wire used for a particular metal.

The thickness of Welding Wire

While choosing the thickness of the welding wire, make sure you have a good idea about the thickness of the base metal. Using the detailed wire thickness chart from the manufacturer will give you more in-depth knowledge to become proficient in choosing the ideal thickness for you.

When it comes to welding thin sheets of mild steel, going for the ER70S-6 is the best choice. For thin metal sheets, wire thickness up to 0.24 inches can be used effectively.


24 ga*
22 ga**
20 ga**
18 ga***
16 ga**
14 ga***


Influence of Manganese and Silicon

One of the most essential decisions that we must take would be to choose either manganese or silicon-based metal wires used in the welding process. The Al, Ti, and Zr deoxidizers in Spool-arc 65 wire tend to make its puddle somewhat sluggish. The “stiff” puddle characteristic makes this wire ideal for pipe, especially small diameter pipe – and many other out-of-position welding jobs.

Influence of Shielding Gas and Arc Voltage

Argon-based shielding gases provide a more stable, uniform wire-to-base plate metal transfer, well-shaped beads, minimal spatter loss, and a lower fume generation rate.

Increasing arc voltage tends to increase puddle fluidity, flatten the weld bead, increase edge wetting, and increase spatter. Higher voltages also reduce penetration and may cause additional loss of alloying elements.

Spoolarc wires, either copper-coated or “bare,” provide excellent feed ability and arc stability under the toughest shop conditions and most demanding applications even at high wire feed speeds… which means less downtime, greater productivity.

Solid GMAW Wire

MIG Solid Wire

GMAW or MIG welding requires the use of a solid wire electrode for welding and these electrodes are commonly referred to as GMAW electrodes.

The chemical structure of the wire and shielding gas used enables us to understand the mechanical properties and durability of the wire used.

Shielding gas must be supplied in the right amounts to protect the weld from atmospheric strains.

  • Dirty Steel: Under GMAW wires, there are several types available where each type has its own type of deoxidizing nature. The deoxidizing nature of the wire enables it to handle light to medium amounts of contamination. The ER70S-6 wire has huge amounts of silicon and manganese in it when compared to the ER70S-3 wire. The ER70S-4 is an intermediate wire between the ER70S-3 and ER70S-6 wires.
  • Travel Speed: Solid GMAW wire performs really well when we work on a blasted plate which has been showing to fire quite early in the welding process. The same electrode wire does not perform well enough on a heavy-mill scaled-plate. Oxidizing properties being low, the bead shape and travel speeds are affected adversely.
  • Positional Welding: Using a short-arc method you can do MIG welding at low amperages and that too only in the vertical position when using metal-cored wire. Pulse welding will show better results to improve out of position welding performance rates when using a solid GMAW wire.
  • Mechanical Properties: The strength and durability of the weld produced using the solid GMAW wire isn’t as good as expected. Metal-cored and flux-cored MIG wires are much more preferred to work with low-alloy and high tensile-strength metals.
  • Post-weld Operations: Short-arc and globular modes of metal transfer require some cleanup after the weld. This is because after the GMAW is completed, silicon release and some spatter need to be removed before the next coating is done.

Metal-cored Wire

Metal-cored electrode wires are cylindrically-shaped and contain maximum amounts of metallic constituents. Just like solid GMAW wires, these electrode wires produce some slag-less welds that require minimal clean-up after the weld.

Metal Cored Wire
Source: Manufacturing Automation

The metal-cored wire was earlier referred to as flux-cored wire and now is known as a composite GMAW electrode.

  • Dirty Steel: Unlike solid GMAW wires, these electrodes can handle mill-scale and surface contaminants more efficiently due to the metallic components that it possesses and hence more deoxidation is done when compared to the solid GMAW wire.
  • Deposition: At a particular high-amperage the metal composition of the tubular wire is high than that of the solid wire given the same diameter. Large diameter metal-cored wire is not apt enough to be used for semi-automatic welding because of the heat radiation given by the arc at high amperage levels.
  • Travel-speeds: If you consider travel speeds, using metal-cored wire is the best choice for you. On a mill-scale plate, this electrode produces some amazing bead shape and performance producing less spatter and good overall weld performance.
  • Positional Welding: Just like solid GMAW wire, the metal-cored wire can also be used for pulse welding for out-of-position deposition rates.
  • Mechanical Properties: Low-alloy metallic components can be added to the core to achieve the desired mechanical properties. This ability to add components can make it easier to produce the desired mechanical properties with metal-cored electrodes than with solid wires of comparable strength.

Gas-shielded FCAW Wire

The gas-shielded wire is also a tubular electrode with a fluxing agent in the core, along with deoxidizers providing a great amount of protection from the atmospheric conditions. FCAW electrodes can be used for both in-position and out-position welding situations.

Gas-shielded FCAW Wire
Source: Airgas
  • Dirty Steel: Out of the above two types of electrode wires, FCAW wire is the most resistant and hence can be easily used in dirty metal bases. It also has additional layers of flux and uses shielding gas that adds a great amount of atmospheric protection.
  • Deposition: Large-diameter and gas-shielded FCAW wires offer more deposition of weld in terms of pounds per hour than solid GMAW or a metal-cored wire. Tandem GMAW has advantages that are similar to that of automatic metal-cored welding but with higher rates of deposition when compared to gas-shielded FCAW wires.
  • Mechanical Properties: FCAW wires achieve good mechanical properties as they have some additional flux and slagging agents added to them during manufacture.
  • Positional Welding: Choosing a smaller-diameter ranging from 0.035-1.16 inches in diameter is used. When welding in the out-of-position, using AWS E71T-1 or E71T-12 can lend you a good amount of deposition rates.
  • Post-weld Operations: This type of MIG wire requires the most needed maintenance and post-weld cleanup. A slag needs to be removed that is formed between multiple-pass applications before coating or painting it.