MIG welding uses a hand-held gun that contains a spool-fed wire electrode, along with a gas nozzle that delivers a stream of gas to the weld site. This gas prevents the contact of oxygen, nitrogen, and other environmental gases with the weld bead – which helps ensure consistent, strong results.
Contamination can lead to a low-quality weld on your workpiece, so choosing the right gas is absolutely essential for the best results. But what’s the best gas for MIG welding? Unfortunately, the answer is not that simple.
Different metals require different types of gases for the best results, although in most cases, a 75/25 argon and CO2 mix will let you get good results on most metals. But let’s take a look at some of your options now, and discuss how you can choose the right MIG welding gas for your job.
MIG Welding Gas – Choosing The Right Gas
Many MIG welding applications lend themselves to a variety of shielding gas choices. You need to evaluate your welding goals and your welding applications in order to choose the correct one for your specific application. Consider the following as you make your selection:
- The cost of the gas
- The finished weld properties
- Preparation and post-weld clean up
- The base material
- The weld transfer process
- Your productivity goals.
The four most common shielding gases used in MIG welding are Argon, Helium, Carbon Dioxide, and Oxygen. Each provides unique benefits and drawbacks in any given application.
Carbon Dioxide (CO2)
The most common of the reactive gases used in MIG welding is Carbon Dioxide (CO2). It is the only one that can be used in its pure form without the addition of inert gas. CO2 is also the least expensive of the common shielding gases, making it an attractive choice when material costs are the main priority.
Pure CO2 provides very deep weld penetration, which is useful for welding thick material. However, it also produces a less stable arc and more spatters than when it is mixed with other gases. It is also limited to only the short circuit process.
For companies that place an emphasis on weld quality, appearance, and reducing post-weld cleanup, a mixture of between 75 – 95 percent Argon and 5 – 25 percent CO2 may be the best option. It will provide a more desirable combination of arc stability, puddle control, and reduced spatter than pure CO2.
This mixture also allows the use of a spray transfer process, which can produce higher productivity rates and more visually appealing welds. Argon also produces a narrower penetration profile, which is useful for fillet and butt welds. If you’re welding a non-ferrous metal, aluminum, magnesium, or titanium you’ll need to use 100 percent Argon.
Oxygen, also a reactive gas, is typically used in ratios of nine percent or less to improve weld pool fluidity, penetration, and arc stability in mild carbon, low alloy, and stainless steel. It causes oxidation of the weld metal, however, so it is not recommended for use with aluminum, magnesium, copper, or other exotic metals.
Helium, like pure Argon, is generally used with non-ferrous metals, but also with stainless steel. Because it produces a wide, deep penetration profile, Helium works well with thick materials and is usually used in ratios between 25-75 percent Helium to 75-25 percent Argon.
Adjusting these ratios will change the penetration, bead profile, and travel speed. Helium creates a ‘hotter’ arc, which allows for faster travel speeds and higher productivity rates. However, it is more expensive and requires a higher flow rate than Argon.
You’ll need to calculate the value of the productivity increase against the increased cost of the gas. With stainless steel, Helium is typically used in a tri-mix formula of Argon and CO2.
Hydrogen serves as a shielding gas in high-temperature applications, such as stainless steel. It is often mixed with argon for use on austenitic stainless steel.
Nitrogen is used as a purging gas for welding stainless steel tubes. Added to argon in small amounts, it can also be used as a shielding gas for stainless steel.
Propane is typically used in scrap yards for cutting carbon steel where cut quality is not important. If your application does not require high cut quality, propane is a rather cost-effective option.
What’s the Best Gas for MIG Welding Different Metals?
The basic gas for MIG/MAG welding is argon (Ar). Helium (He) can be added to increase penetration and fluidity of the weld pool. Argon or argon/helium mixtures can be used for welding all grades.
If you want a “one-size-fits-all” option, a MIG welding shielding gas with a 75/25 mix of argon and CO2 is likely going to be your best bet. We carry a high-quality 75/25 argon and CO2 mix at Vern Lewis Welding Supply, which is an ideal, cost-effective option that can be used to weld most metals, including mild steel and nonferrous metals.
Conclusion: How to Choose the Best Gas for MIG Welding
If you’re searching for the best gas to use for MIG welding that has broad application, the 25% carbon dioxide and 75% argon or anything similar to that such as an 80/20 mix, is possibly your best choice.
If you’re on a budget and won’t mind cleaning up a little additional spatter, carbon dioxide is inexpensive at excellent when it comes to experimentation and hobby welding. 100% argon is the way to go for MIG welding aluminum, or generally TIG welding.
With stainless steel, things get more costly when more helium is mixed with argon and carbon dioxide or Oxygen. There, you also have the option of selecting a cheaper C2 with a 98/20 mix.
Always take into account the metals you want to weld and ensure that you’re getting the most out of your gas flow. Don’t forget that the key to a dependable bead pattern and avoiding overheating the metal is your preferred gas and your gas’ flow rate.