If you’re looking for fast and clean cuts in your metal projects, then plasma arc cutting should be your go-to method. But which gas should you use with your plasma cutter? In this article, we’ll explore four different types of gases that are commonly used for plasma cutting. We’ll discuss the metals they’re best suited for, as well as the advantages and disadvantages of each gas.
What Gas Do Plasma Cutters Use?
The choice of gas for plasma cutting depends on the type of material and its thickness. Different gases can achieve different cut qualities, so finding the right balance between results, speed, part life, and operating costs is crucial. Let’s take a look at the four most common gases used with plasma cutters.
Compressed Air
Compressed air is the most versatile gas for plasma cutting. It works well with low current cutting and provides excellent cuts for plasma gouging on mild and stainless steel, aluminum, and carbon steel. One of the advantages of using compressed air is that it is an economical option as air is provided for free. However, you will need a separate air compressor to run this setup. It is commonly used for cutting metals up to 1 inch thick.
Advantages:
- Economical
- Can also be used for gouging
Disadvantages:
- Leaves oxidized cut areas that affect solderability
- Oxidation and nitriding of the cut surface may occur, leading to porosity in the weld
- Requires a separate air compressor unit
Oxygen
Using oxygen in a plasma torch offers the fastest cutting speeds and the best cut quality compared to other plasma gases. It is suitable for carbon steel up to 1-1/4″ thick when high-quality cuts are required. When oxygen plasma gases react with carbon steel, they produce a fine spray of molten metal, which can be easily expelled from the cut. However, using oxygen on stainless steel and aluminum may result in a rougher cut surface.
Advantages:
- Cutting speed
- Best cut quality for mild steel
Disadvantages:
- Expensive gas
- Wear parts have a shorter service life (although high-quality oxygen plasma torches can achieve similar results using an inert gas and an oxygen plasma, such as nitrogen)
While oxygen may have higher costs, minimizing post-weld operations like dross removal and straightening beveled parts can help offset those expenses.
Nitrogen
Nitrogen is ideal for high current plasma cutters and provides excellent cut quality on mild steel, stainless steel, and aluminum up to 3 inches thick. It is often used with argon as a stabilizer to enhance wetting to weldments and reduce costs. Nitrogen plasma works well when combined with CO2 as an assist gas, resulting in faster cuts and longer part life compared to using air alone. Water can also be used as a secondary assist gas.
Advantages:
- Excellent cut quality
- Enduring part life
Disadvantages:
- Higher cost when combined with CO2
- Nitrogen can be expensive
Argon-Hydrogen
Argon-Hydrogen is primarily used for cutting stainless steel and aluminum. It produces a clean, straight, and smooth surface on stainless steel. The optimal ratio for this gas is 65% Argon and 35% Hydrogen, which provides the hottest plasma combustion gases for a near-perfect, clean cut. However, cutting mild steel with this combination is not recommended. Water injection torches use argon-hydrogen to cut stainless steel up to 6 inches thick. It can also be used for plasma gouging, but it may leave jagged slag on the bottom edge of the material.
Advantages:
- Produces the hottest plasma for cutting materials
- Suitable for plasma gouging on any material
Disadvantages:
- High operating costs
- Slag may appear along the bottom edge of the material being cut
Choosing the Right Gas
When selecting a gas for plasma cutting, several factors need to be considered, including the type of material, desired cut quality, and budget. The table below provides a guide to choosing the best gas for various materials:
| Plasma Gas and Shielding | Mild Steel | Anti-rust | Aluminum |
|---|---|---|---|
| Air and air | Good cutting quality, faster cutting speeds, cost-effective | Good cutting quality, faster cutting speeds, cost-effective | Good cutting quality, faster cutting speeds, cost-effective |
| Oxygen and air | Good cutting quality, faster cutting speeds, very little slag | Not recommended | Not recommended |
| Nitrogen and air | A little scum, fair cut quality, impressive part life | Impressive component life, good cut quality | Impressive component life, excellent cut quality |
| Nitrogen and carbon dioxide | Little scum, impressive component life, fair cut quality | Impressive part life, good cut quality | Impressive part life, good cut quality |
| Nitrogen and water | A little scum, fair cut quality, impressive part life | Excellent cut quality, impressive part life | Excellent cut quality, impressive part life |
| Argon hydrogen water | Not recommended | Ideal for thicknesses >1/2″ | Ideal for thicknesses >1/2″ |
Related Reading: Best Plasma Cutters – Top Picks and Reviews
Wrapping It Up
In conclusion, when it comes to plasma cutting, the choice of gas plays a significant role in the overall cut quality. Oxygen plasma is ideal for mild steel, while argon and nitrogen work well for aluminum and stainless steel. When cost-effectiveness is a priority, clean compressed air is the best choice for cutting aluminum, mild steel, and stainless steel. So, consider the type of material, the desired cut quality, and your budget when selecting the right gas for your plasma cutting needs.