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MIG Wire Sizes

For most welding types, you’ll use a stick electrode or a filler rod, but it’s not the case with MIG welding (also known as GMAW – Gas Metal Arc Welding). In MIG welding, you use a metal wire spool that deposits and makes a joint.

MIG welding is popular for its use in product fabrication and structural welding cases. It works on the basic principle of melting the wire to produce a weld pool and the shielding gas that is stored in a Gas Tank. The shielding gas is mostly C02 and O2. This weld is done by pushing the wire out of the brass nozzle of the MIG welding machine, which provides pinpoint accuracy to the joint.

MIG, which is also taken as “Metal Inert Gas” is easier to perform as its gun holds a long mile of wire inside it, making it not load again and again.
In this article, we’ll be discussing the best MIG wire sizes depending on different factors for your welding guns. So let’s Deep dive into it without wasting a second.

Wire Classification

Wire Classification is the first and main step in the finalization of your wire spool size. You have to be very careful and choosey while making the perfect decision. You must take care of your weld material, the condition of your workpiece, and its nature to decide which wire spool will work best for you.

The wire Classification method has been put forward by the Mechanical Engineers of American Society. They have various codes assigned for several Wire sizes.

Mostly two types are present for steel. One is AWS classification ER70S-3 for all-purpose weld and the other is ER70S-6 for rusty and dirty steel.

Let’s understand what the code says about the classification.

  • ER – an abbreviation for Electric Rod.
  • 70 – this code could sometimes be of two to three numbers. It tells the tensile strength of the welding wire in PSI (pound per square inch), multiplied by 1,000.
  • S – an abbreviation for Solid wire
  • 3 – This number tells us about the chemicals added to the wire, which may affect the polarity.

In the case of the above code, the wire spool doesn’t contain chemical additives and is best to use on new and clean workpieces. While in the case of ER70S-6, it has chemical additives such as deoxidizers which are added to remove any kind of rust or dust piled.

Other aluminum Mig wires include Er5056 and ER5356. The former wire has quite amazing deductibility, while the latter is harder and has more tensile strength.

1. Wire Diameter

After deciding your wire spool classification, you must identify its diameter to work it accordingly. For this, you must consult a chart from an experienced welder to find yours best.

The most common diameters used are 0.30-inch, 0.23inch, and 0.45-inch:

  • 0.30-inch has usually been used in home and motorsports applications as an all-rounder.
  • 0.23-inch is popular for heat input resistance.
  • 0.45-inch is used if it’s in your welding output range.

2. Wire Quantity

Let’s say you’ve decided on your wire spool class and the diameter. Now the last thing you have to decide is its quantity and how much wire spool you need according to your MIG machine.
A non-industrial MIG machine takes a much smaller spool of wire as compared to the industrial MIG machine. It means you have to decide according to your industry.

If you’re not guessing the right spool of wire, you can make orders in “TIG cut lengths.” This includes three-foot strands, just as they are used in TIG welding.

3. Wire setting

The last step in the whole process is setting up your welding machine. You must set the equipment, shielding gas, and all the necessities according to your welding process.

Flux-Cored Wire

The flux-cored wire is usually used in MIG welding as a substitute for the Shielding gas. It performs the same function as the gas and prevents any environmental interference during the welding process.

Just like the stick road coatings, the flux wire contains agents that act as shielding for the wire and helps a lot in outdoor welding processes. Because a little breeze can disperse the shielding gas, it is advisable to use the flux-cored wires to never let that happen to you.

The use of flux-cored wire in MIG welding is known as Fluxed-cored arc welding (FCAW).
Regular Flux-cored wire is usually called Self-shielded wire and that’s why the process is commonly called (FCAW-S).

The advantages of using the Flux-cored wire are as follows:

  • You can use high Amperages.
  • You can Deal with larger Diameters.
  • It works amazingly outdoors in structural welding.
  • They have more strength than solid wires.
  • You don’t have to deal with a gas tank separately.

Flux Core Wire Classification

Flux-Cored Wire classification varies very slightly from the MIG Solid wire code.E70C-6 is a common example of it. Let’s interpret it to easily understand it:

  • E (instead of ER) – stands for Electrode
  • T/C (instead of S) – stands for tubular or composite
  • 7 – refers to the tensile strength (multiplied by 10,000)
  • 0 – refers to the welding position. Rather horizontal or flat.

The most common wire used in Lincoln Electric’s inner shield is NR-232 as AWS E71T-8.

Where 1 indicates that the wire is workable in all positions, while 8 is for low hydrogen.

The most common wire used in Earthquake areas like California is NR-232 due to its seismic eligibility.

Using Shielding Gas And Flux – Cored Wire Together

As we were discussing using Shielding gas and flux cored wire separately earlier, now we are going to combine them. You can use both of these together to make welding.

Both of these act as shielding from the interference of the external environment, this is known as dual-shielded flux-core welding or gas-shielded welding. This works like a double coating of prevention in your weld process.


As we have seen, choosing a wire takes a lot of information to be considered. You can gradually come up with all the characteristics and choose the perfect wire spool size for your weld machine. It’s okay to start with minor details and then broaden your area. You just have to start. Try following the steps below and find your proper spool and start welding. If you’ve got any queries, comment below to let us know.

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