Getting the best quality cuts from your plasma cutting entails a balance combination of a lot of its components. Besides having a properly working torch, table, and consumables, the selection and choice of gases for your entire plasma cutting processes plays a crucial role in getting quality metal cuts. These gases, in the first place, are what make the plasma cutting effective in cutting your metal piece.
The wrong choice on this aspect can bring you a lot of problems during the process of plasma cutting as well as on the next metal fabricating steps. We know that a lot of fabricators use plasma systems with multi-gas or dual-gas capabilities. What this means is the capability of the plasma cutter to be applied on a variety of applications. Yet, it is common for most fabricators to be overwhelmed by the plasma cutting system manuals that provide a confusing array of gas choices and cut charts.
When you ask them why they use a particular gas, they would reply: “Because my supplier told me so”. In this article, we will introduce you to the basic information about plasma cutting gases and the best choice gases that can be used for different materials.
Definition of Gas Types for Plasma Cutting
Before going in knowing the best gas for your plasma cutting, let’s first check out the definition of gases in the plasma cutting processes:
- Plasma Gas: this are all the gases that create or that compose the plasma arc or beam and responsible for cutting your materials. In a plasma arc, two phases are present, namely, the ignition and cutting phase. The plasma gases then are divided into these two phases. These gases differ in gas types and volume flow rate.
- Swirl Gas: this gas functions to cover the plasma arc. This is also called the secondary gas or shield gas that assists in improving the cut quality. This gas protects the plasma gas as well as cools the consumables.
- Control Gas: This gas usually leads to the torch and have control of the protection cap. What it does is determine whether the torch is properly installed for the machine to start.
Plasma Cutting Gas Selection
If there is a plasma gas that is the most versatile, it is air since it can provide an excellent cut quality as well as speed on cutting stainless, mild steel and aluminum. Using this particular gas also lowers your operation cost considering you don’t have to buy it – a reason why plasma cutting` systems utilizing this gas is that it is not popular with suppliers. Nevertheless, it is popular in many shops considering it provides cut quality, low dross levels and good speed. But air is not totally free.
You also must ensure that your shop air is clean from particulates, moisture and oil mist. To use this particular properly, you must invest in a refrigerated dryer, good sized air compressor, and bank of filters so you can take out oil mist, particulate and remaining moisture. There is only one issue that can be derived from the use of air gas. This is the weld-ability of the cut edge. This happens when the air gas reacts with metals resulting to oxidation and nitriding on the cut surface. This can be corrected by using a weld wire with deoxidizers and denitrifiers.
This gas has been the popular gas used during the early days of plasma cutting, though it is still the best choice if you frequently work on a lot of stainless and aluminum. This gas usually provides excellent cut quality as well as prolonged life of consumables. But this type of gas usually does not work well with thick metals, in this case it is proper to switch to Argon-Hydrogen.
As a preferred process, nitrogen is best used alongside air as secondary gas. It is also best applied with water being shield gas if the system allows it. This makes for a shiny cut surface especially on aluminum and stainless. If you are going to use water as secondary gas, the cut process is better done on a water table.
This gas is the industry standard for gas choice for the reason that the plasma cut process results to excellent cut quality and it provides the fastest speed among other plasma gas. However, you must remember that oxygen does not fit well in cutting stainless or aluminum. Oxygen normally reacts with carbon steel and this produces a finer spray of molten metals and can pose on the safety of the plasma cutting process.
Another disadvantage of oxygen as your plasma gas of choice is its cost and reduced life of consumables when you use it. Some plasma cutting system corrected this by using nitrogen as inert starting gas to affect a longer life for consumables similar to what is experienced when using air and nitrogen gas. Additionally, the best secondary or shield gas to use with it is air gas.
4. Argon Hydrogen:
This gas is the perfect choice when cutting thick stainless and aluminum. It is also the hottest burning plasma gas thus provides the best cutting efficiency. When used in multi-gas torches, it can produce a clean, straight quality cut that is almost polished, though some jagged dross might result at the bottom. The most suitable secondary or shield gas for this choice of gas is nitrogen. However, the only disadvantage this brings is the expense.
It is too common for metal fabricators to be overwhelmed by the plasma cutting systems manuals on arrays of plasma gas and variety of cuts you can get. Usually, these fabricators rest their choice of plasma gas on their suppliers, sometimes not considering other gases in their shops. In this article we showed you the different definition of plasma gas in regards to plasma cutting processes. We also gave a brief introduction to the most common plasma gases that can fit well with your metal cutting.