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Plasma cutting is one of the most popular methods of custom metal fabrication, and it is commonly used to process mild steel, stainless steel, carbon steel, aluminum, and other electrically conductive metals. Why does plasma cutting only work on electrically conductive metals? Because the plasma itself is electrically conductive, and it must react to the metal in order to cut through it. Generating the plasma requires the introduction of a gas, such as oxygen, nitrogen, argon, hydrogen, or compressed air. Which gas is used will depend on the type and thickness of the metal plate. Before we take a closer look at how each gas is used, let’s review how plasma cutting works.
Generating Plasma—the Fourth Element
The cutting head of a plasma cutting machine forces gas through the miniscule opening of the nozzle. At the same time, an electrical arc is passed through the gas, drastically increasing its temperature to 45,000 degrees Fahrenheit (25,000 degrees Celsius). That’s hot enough for the plasma cutter to slice through the metal plate with ease and melt away the dross, leaving behind clean cut lines.
Types of Gasses That Are Used to Generate Plasma for Metal Fabrication
As noted above, the type of gas that is used to generate the plasma will depend on the metal’s chemical makeup, as well as its thickness and dimensions. Sometimes, two gasses are used in tandem to create specific results. Here are some details about the most common types of gasses used in plasma cutting:
Oxygen
Boasting the fastest cutting speeds of all the gas types, oxygen is the go-to choice for fabricating mild steels measuring up to 1 ¼ inches thick. It produces high-quality cuts and leaves behind smooth edges, and it works well with other gasses. However, oxygen is more expensive and has a shorter lifespan than other gasses, and it is less effective on metals with shiny surfaces, such as aluminum and stainless steel.
Nitrogen
When custom fabricators need to process aluminum, stainless steel, and other shiny metals, they will typically use nitrogen in the plasma cutter. Nitrogen is not only more effective at cutting these materials than oxygen, but it can also process thicker plates, measuring up to three inches thick. And because nitrogen is an abundant resource, it is one of the least expensive gasses used in plasma cutting.
Argon
Argon generates the hottest-burning plasma and is therefore ideal for processing thick plates. It also produces a highly stable arc, resulting in clean cuts and less atmospheric contamination. One drawback to argon, however, is that it has low conductivity and therefore needs to be paired with a secondary gas for optimal results. Also, because it is a rare, inert gas, argon is more expensive than other gasses.
Compressed Air
Perhaps the most common gas used for plasma cutting is compressed air, an affordable option that can be easily stored and paired with other gasses. Compressed air is highly versatile and works best for low-current cutting of mild steel, stainless steel, aluminum, and other metals measuring up to an inch thick.
Where to Purchase a Plasma Cutting Machine
Machitech is a leading manufacturer of heavy-duty CNC plasma cutting tables. If you’re looking to take your custom fabrication shop to the next level, contact us today to learn how our automated solutions can help. When you do, be sure to ask about the free and unlimited lifetime support that you’ll receive with your purchase.