In the practical application of plasma cutting, there are many working gasses, which are mainly selected according to the cutting environment and cutting materials. For example, air, pure oxygen, carbon dioxide, etc. can be used as working gasses to participate in cutting, but no matter which working gas is used, several key issues need to be paid attention to.
1. Ensure the correct air pressure and flow of the plasma gas. The correct air pressure and flow of the plasma gas are very important to the service life of the wearing parts. If the air pressure is too high, the life of the electrode will be greatly shortened; if the air pressure is too low, the life of the nozzle will be affected.
2. After replacing the wearing parts, the advanced residual gas in the cutting torch should be discharged. After replacing the wearing parts or after a long shutdown, the remaining gas in the cutting torch should be discharged (2-3 minutes is appropriate) to ensure that the gas is discharged from the cutting torch. of moisture.
3. Keep the plasma gas dry and clean. The plasma system needs dry and clean plasma gas to work properly. The gas compression system often pollutes the gas, which can easily shorten the service life of the wearing parts and cause abnormal damage to the wearing parts. The way to test the gas quality is to set the system in the test state, put a mirror under the cutting torch, and if the gas discharged from the cutting torch produces water vapor or mist on the mirror, you need to start from the gas compression system and check it in time.
Khí và Vật liệu cắt cần thiết để cắt Plasma
Commonly used plasma cutting working gases are argon, hydrogen, nitrogen, oxygen, air, water vapor, and some mixed gases. Plasma cutting machines are widely used in automobiles, locomotives, pressure vessels, chemical machinery, nuclear industry, general machinery, construction machinery, steel structures, etc. Plasma cutting machines are mainly used for cutting metal sheets, including some that cannot be cut with other equipment. It can be used for various metal materials with different properties, including stainless steel, alloy steel, carbon steel, copper, and other non-ferrous metal materials. This machine can cut sheets into complex shapes as needed. Its features: stable, reliable, lightweight, energy-saving, noise-free, fast cutting speed, smooth cutting, and no need to polish.
The operation method is as follows: Turn on the power switch and set the power switch to the “ON” position. At this time, the fan starts to rotate, and the meter screen displays the set current value. Adjust the air pressure knob to the desired pressure and open the compressed air valve. Press the control button on the cutting gun, and the solenoid valve will act, and the high-frequency arc discharge sound can be heard in the machine. At the same time, the gas should flow out from the nozzle of the cutting gun, and a plasma arc should be ejected from the nozzle of the cutting gun. According to the thickness of the workpiece to be cut, set the corresponding cutting current. Place the copper nozzle of the cutting gun at a distance of 2mm from the workpiece. After pressing the button on the cutting gun to ignite the arc, the high-frequency arc ignition spark in the machine disappears immediately, and the cutting can be started at this time.
Huyết tương cắt with different working gases can cut various metals that are difficult to cut by oxygen cutting, especially for non-ferrous metals (stainless steel, aluminum, copper, titanium, nickel), the cutting effect is better; its main advantage is that the cutting thickness of metals is not large. At times, the plasma cutting speed is fast, especially when cutting ordinary carbon steel sheets, the speed can reach 5~6 times that of the oxygen cutting method, the cutting surface is smooth, the thermal deformation is small, and there is almost no heat-affected zone!
Working gas includes cutting gas and auxiliary gas. The choice of working gas is usually based on the type, thickness, and cutting method of the cutting material. Common working gases are argon, nitrogen, oxygen, air, H35, argon-nitrogen mixed gas, etc. The following introduces the characteristics of several working gases:
1. Nitrogen (N2) is a commonly used working gas. Under the condition of higher power supply voltage, N2 plasma arc has better stability and higher jet energy than argon, even when cutting liquid metal with high viscosity The amount of slag hanging on the lower edge of the incision is also very small when using materials such as stainless steel and nickel alloys. N2 can be used alone or mixed with other gases. For example, N2 or air is often used as working gas in automatic cutting. These two gases have become standard gases for high-speed cutting of carbon steel. Nitrogen is sometimes used as a starting gas for oxygen plasma arc cutting.
2. Oxygen (O2) can increase the speed of cutting mild steel materials. When using O2 for cutting, the cutting mode is similar to flame cutting. The high-temperature and high-energy plasma arc make the cutting speed faster, but the electrode that resists high-temperature oxidation must be used together, and the electrode should be protected from impact during arcing to prolong the electrode. life.
3. The air contains about 78% of N2 by volume, so the slag formation formed by air cutting is very similar to that when cutting with N2; the air also contains about 21% of O2 by volume, because of the presence of oxygen, use air The cutting speed of mild steel materials is also high; at the same time, the air is also an economical working gas. However, when using air cutting alone, there will be problems such as slag hanging, kerf oxidation, and nitrogen addition, and the low life of electrodes and nozzles will also affect work efficiency and cutting costs.
4. Argon gas (Ar) hardly reacts with any metal at high temperatures, and the Ar plasma arc is very stable. Moreover, the nozzles and electrodes used have a high service life. However, the Ar plasma arc has a low voltage, low enthalpy, and limited cutting ability. Compared with air cutting, the cutting thickness will be reduced by about 25%. In addition, in the Ar protection environment, the surface tension of the molten metal is larger, which is about 30% higher than that in the N2 environment, so there will be more slag problems. Even cutting with mixtures of Ar and other gases can have slag sticking problems. Therefore, pure Ar is rarely used alone for plasma cutting these days.
5. Hydrogen (H2) is usually used as auxiliary gas to mix with other gases, such as the well-known gas H35 (the volume fraction of H2 is 35%, and the rest is Ar) is one of the gases with a strong plasma arc cutting ability, which mainly benefits from H2. Since H2 can significantly increase the arc voltage, the hydrogen plasma jet has a high enthalpy value. When it is mixed with Ar, the cutting ability of the plasma jet is greatly improved. Generally, for metal materials with a thickness of more than 70mm, Ar+H2 is often used as the cutting gas. If a water jet is used to further compress the Ar+H2 plasma arc, higher cutting efficiency can also be obtained.
In the actual cutting process, customers still need to start from their own cutting requirements and economic costs, comprehensively consider, and select the appropriate working gas for cutting.
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