What is the role of the gas used by the CNC plasma cutter?

What is the role of the gas used by the CNC plasma cutter

1. Oxygen can increase the speed of cutting low carbon steel materials. When using oxygen for cutting, the cutting mode is very similar to flame cutting. The high temperature and high energy plasma arc make the cutting speed faster, but the electrode must be used with high-temperature oxidation resistance. At the same time, the electrode is protected against impact when the arc is started to extend the electrode. Life.
2. Hydrogen is usually used as auxiliary gas to mix with other gases. For example, the famous gas H35 (the volume fraction of hydrogen is 35%, and the rest is argon) is one of the most powerful gases for plasma arc cutting, which is mainly beneficial hydrogen. Because hydrogen can significantly increase the arc voltage, the hydrogen plasma jet has a high enthalpy value. When mixed with argon, the cutting ability of the plasma jet is greatly improved. Generally, for metal materials with a thickness of more than 70mm, argon + hydrogen is commonly used as cutting gas. If the water jet is used to further compress the argon + hydrogen plasma arc, higher cutting efficiency can be obtained.

Air compressor

3. The air contains about 78% of nitrogen by volume, so the dross formed by air cutting is very similar to that when cutting with nitrogen; the air also contains about 21% of oxygen by volume. Because of the existence of oxygen, use air The cutting speed of low carbon steel materials is also very high; at the same time, the air is also the most economical working gas. However, when air cutting is used alone, there will be problems such as slagging, incision oxidation, and nitrogen increase, and the low life of electrodes and nozzles will also affect work efficiency and cutting costs. Since plasma arc cutting generally uses a power supply with a constant current or steep drop characteristics, after the nozzle height increases, the current change is small, but it will increase the arc length and cause the arc voltage to increase, thereby increasing the arc power; but at the same time The arc length exposed to the environment increases, and the energy lost by the arc column increases. In the case of the combined effect of the two factors, the role of the former is often completely offset by the latter, which will reduce the effective cutting energy and reduce the cutting ability. The usual performance is that the blowing force of the cutting jet is weakened, the residual slag in the lower part of the incision increases, and the upper edge is over melted and rounded.
4. Nitrogen is a commonly used working gas. Under the condition of higher power supply voltage, nitrogen plasma arc has better stability and higher jet energy than argon, even for cutting liquid metal with high viscosity materials such as In the case of stainless steel and nickel-based alloys, the amount of dross on the lower edge of the cut is also small. Nitrogen can be used alone or mixed with other gases. For example, nitrogen or air is often used as the working gas in automated cutting. These two gases have become the standard gas for high-speed cutting of carbon steel. Sometimes nitrogen is also used as the starting gas for oxygen plasma arc cutting.
5. Argon hardly reacts with any metal at high temperature, and the argon CNC plasma cutting machine is very stable. Moreover, the nozzles and electrodes used have a higher service life. However, the voltage of the argon plasma arc is low, the enthalpy value is not high, and the cutting ability is limited. Compared with air cutting, the cutting thickness will be reduced by about 25%. Also, in an argon atmosphere, the surface tension of molten metal is relatively large, which is about 30% higher than in a nitrogen atmosphere, so there will be more slagging problems. Even cutting with a mixture of argon and other gases will tend to stick to slag. Therefore, it is rare to use pure argon alone for plasma cutting.

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