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Plasma Cutting |
| Plasma (arc) cutting was developed in the 1950s, to cut metals that could not be flame-cut (e.g., stainless steel, aluminum and copper). Plasma cutting requires an electrical power source; its investment costs are higher than those for oxy-fuel cutting, but much lower than for laser cutting.
With plasma cutting, gas is ionized in the nozzle and focused the nozzle’s special design. This hot plasma stream alone can be used to cut materials such as plastics (non-transferred arc). In metal cutting, an electrical arc is also ignited between the electrode and the workpiece, to increase the energy transfer. A very narrow nozzle orifice focuses the arc and the plasma stream. Additional lacing of the discharge path can be achieved by a secondary (i.e., shroud) gas. For environmental reasons, plasma cutting is often done underwater, in a basin. |
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| Plasma gases include argon, hydrogen, nitrogen and mixtures thereof, as well as air and oxygen. Because of the intense heat of the plasma, i.e. 39,992°F (22,200°C), compared to the 5,702°F (3,150°C) of and oxy-fuel flame, the cut is clean and virtually dross-free.
High-precision plasma-cutting units are based on the highly effective focus of the plasma stream (e.g., by rotating the stream).
In plasma cutting, the gas combination is often specified by the equipment manufacturer. Linde supplies:
- Argon/hydrogen mixtures: used with hydrogen content of 5–35%. Mixtures with higher hydrogen content are more suitable for cutting stainless steel and aluminum. Lower hydrogen mixtures are used to cut carbon and low-alloy steel.
- Nitrogen: frequently used in dual-gas torches, for cutting all metals. Nitrogen is also used as a plasma-cutting shielding gas, when argon/hydrogen is the plasma gas.
- Air: dry, compressed air is often used – particularly in small, manually operated units – for sheet-metal cutting.
- Oxygen: normally used only as the plasma gas, when cutting carbon and low-alloy steels.
- Carbon Dioxide: used for cooling the nozzle, when nitrogen is used as the plasma gas.
Make sure to study safety precautions to minimize risk. Contact Us to obtain this information and discuss which gas mixtures are best for your particular application. |
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