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How To Select Gas For CNC Plasma Cutting Machine?

Apr 28, 2018

CNC plasma cutting machines usually have higher no-load voltages and operating voltages. When high-ionization gases such as nitrogen, hydrogen, or air are used, the voltage required for uninhibited plasma arcs will be higher. When the current is constant, the improvement of the voltage means the improvement of the arc enthalpy and the improvement of the cutting ability. When using oxygen for cutting, the cutting mode and CNC flame cutting machine are very imaginable. The high temperature and high energy plasma arc makes the cutting speed faster. However, the spiral duct machine must cooperate with the use of an electrode that resists high temperature oxidation, and at the same time, the electrode should be protected against arcing. Impact protection to extend the life of the electrode. Because plasma arc cutting generally uses a power source with constant current or steep drop characteristics, after the height of the nozzle is increased, the current change is small, but the arc length is increased and the arc voltage is increased, thereby increasing the arc power; but at the same time, The arc length exposed to the environment increases, and the energy lost from the arc column increases.

    Even when using a mixture of argon and other gases, there is a tendency for sticky slag.

    1. The air contains about 78% nitrogen in volume, so the slag formed by air cutting is imaginable when it is cut with nitrogen; the air also contains about 21% oxygen by volume, due to the presence of oxygen, using air The speed of cutting low-carbon steel materials is also high; at the same time, air is the most economical working gas. Moreover, the nozzles and electrodes used have a long service life. At present, the use of steel in China's machinery industry has reached more than 300 million tons, and the amount of steel cutting is very large. With the development of modern machinery industry, the work efficiency and product quality requirements for sheet metal cutting and processing are also improving.

    2. Oxygen can improve the speed of cutting low-carbon steel materials. However, when using air cutting alone, there are problems such as slag dregs, incision oxidation, nitrogen addition, etc., and the low life of electrodes and nozzles will also affect work efficiency and cutting costs. Because hydrogen can significantly improve the arc voltage, the hydrogen plasma jet has a very high enthalpy. When used in combination with argon, the plasma jet cutting ability is greatly improved.

    3. Argon gas hardly reacts with any metal at high temperatures. Argon CNC plasma cutting machine is not messy. As a result, pure argon is rarely used alone for plasma cutting.

    The use and selection of gas in the cutting of CNC plasma cutting machines are often important. The use of gas will severely affect the accuracy of cutting, slag dregs, and other phenomena. Nitrogen can be used alone, or it can be mixed with other gases using a plasma cutter. For example, nitrogen or air is often used as a working gas in automated cutting. These two gases have become the standard gas for high speed cutting of carbon steel. Therefore, the market potential of CNC cutting machine is still great, and the market prospects are more optimistic. Nitrogen is also sometimes used as starting gas for oxygen plasma arc cutting.

    4. Hydrogen is usually used as an auxiliary gas to mix with other gases. For example, the famous gas H35 (having a volume fraction of 35% of hydrogen gas and the rest being argon gas) is one of the gases with the strongest plasma arc cutting ability. This is mainly beneficial to hydrogen gas. . However, the argon plasma arc voltage is low, the enthalpy value is not high, and the cutting capacity is limited. Compared with the air cutting, the thickness of the cutting is reduced by about 25%. In addition, the surface tension of the molten metal is larger in the argon protection environment. More than 30% higher than in the nitrogen environment, so there will be more slag problem. If the diameter of the jet is decreased and the flow rate of the gas is increased while the threshold value is improved, a faster cutting speed and a better cutting quality can be obtained.

    5. Nitrogen is a commonly used working gas. Under the premise of higher power supply voltage, the nitrogen plasma arc has good chaos and higher jet energy than argon, even if it is a material that cuts the viscosity of liquid metal. In stainless steel and nickel-base alloys, the amount of dross on the lower edge of the cut is also small.