If you want fast, clean cuts in your metal projects, then plasma arc cutting has to be your first choice.
But what type of gas does a plasma cutter use and how does it work?
In this quick guide, we explore four different types of gases that are suitable for plasma cutting.
Read on to learn what types of metals they're best for cutting and the pros and cons of each.
What gas do plasma cutters use?
Depending on the type of material and its thickness, different gases can achieve different cut qualities.
Ideally, you want a good balance of results, speed, part life and operating costs.
Below are the four most common gases used with plasma cutters.
compressed air
It is the most versatile of all the plasma gases commonly used in low current cutting and provides excellent cuts for plasma gouging on mild and stainless steel as well as aluminum and carbon steel.
Compressed air proves to be an economical option since air is provided for free. You will need a separate air compressor to run this setup, or a built in plasma cutter.
However, you'll still need to remove any dust particles or moisture, which can kick the expense up a notch. It is most commonly used for cutting metals up to 1 inch thick.
advantage
- tend to be economical
- Can also be used for gouging
shortcoming
- Leaves oxidized cut areas that affect solderability
- Oxidation and nitriding of the cut surface may occur, which can lead to porosity in the weld. You can solve this problem by using a high quality welding wire with denitrification and deoxidizer.
- Requires separate air compressor unit
oxygen
Using oxygen in a plasma torch provides the fastest cutting speeds while still delivering the best cut quality of any other plasma gas.
This gas is suitable for carbon steel up to 1 -1/4" thick where the highest quality cuts are required.
When oxygen plasma gases are applied to carbon steel, they react to produce a fine spray of molten metal, each droplet having low surface tension. This fine spray can be easily expelled from the cut.
When using an oxygen plasma, air acts as the shielding gas. Oxygen can also be used on stainless steel and aluminum, but produces a rougher cut surface.
advantage
- cutting speed
- Best cut quality for mild steel
shortcoming
- Oxygen is expensive.
- Wear parts have a shorter service life. However, high-quality oxygen plasma torches use an inert gas and an oxygen plasma, such as nitrogen, to achieve the same results.
That said, you can offset the high cost of consumables and the gas itself by minimizing the expense of post-weld operations, such as removing dross and straightening beveled parts.
nitrogen
Nitrogen is best for high current plasma cutters. It provides excellent cut quality on mild steel and stainless steel or aluminum up to 3 inches thick.
Nitrogen is often used with argon as a stabilizer to increase wetting to weldments while reducing costs.
Nitrogen plasma works very well with CO2 as an assist gas for faster cuts and longer part life than air. You can also use water as a secondary water level.
advantage
- Excellent cut quality.
- enduring part of life.
shortcoming
- Using CO2 is much more expensive than air and means using multiple cylinders to provide enough flow to meet this demand.
- Nitrogen is expensive.
argon-hydrogen
This particular compound is primarily used for cutting stainless steel and aluminum.
Argon Hydrogen produces a clean, straight and very smooth surface on stainless steel.
The perfect stoichiometric ratio to provide optimal conditions is 65% Argon and 35% Hydrogen. This combination of ratios provides the hottest plasma combustion gases for a near-perfect, clean cut. Therefore, cutting mild steel is not recommended.
Water injection torches use argon hydrogen to cut stainless steel up to 6 inch gauge. It is suitable for cutting any material thicker than three inches.
Another advantage of using this combination is that it can also be used for plasma gouging of any material. However, you may find jagged slag on the bottom edge of the material, which can be annoying to handle at times.
As a countermeasure, nitrogen was used as an argon-hydrogen shielding gas. Such gas mixtures also tend to be expensive, adding to operating costs.
advantage
- Produces the hottest plasma for cutting materials.
- Plasma gouging for any material.
shortcoming
- Due to high operating costs, it is uneconomical.
- A layer of slag may appear along the bottom edge of the material being cut.
choose the right gas
When choosing a gas for plasma cutting, you need to consider several key factors, from the type of material you'll be processing, the quality of cut you want, to your budget.
The table below provides the key to selecting the best gas for plasma cutting.
| 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 parts 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 parts 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
wrap it up
When it comes to plasma cutting, the general cut quality depends not only on the welder's expertise, but also on the type of gas used.
Based on industry practice, recommendations on which gas is best for which material are as follows:
- Oxygen plasma is best suited for mild steel with air as the shielding gas, providing the best cut quality and lowest dross. This leaves little chance for rework while still maintaining excellent weldability and high cutting speeds.
- Use Argon and Nitrogen as assist gases for optimum cut quality in aluminum and thick stainless steel. Make sure your system is safe and compatible with Argon Hydrogen.
- Cut stainless steel and aluminum with CO2 nitrogen plasma for best cost effectiveness.
- For the most economical plasma cutting, clean compressed air is best for cutting aluminum, mild steel and stainless steel.