等离子切割（Plasma cutting）.doc

等离子切割（Plasma cutting） Six sections of plasma arc welding and cutting and safety operation The formation of plasma arc The plasma arc is a free arc compression. The electric arc is compressed by water - cooled nozzles and limits its diameter. The temperature of the gas is low, and the gas temperature in the inner wall of the nozzle is extremely low, forming a certain thickness of the air-cooled film. The air-cooled film further forces the section of the arc column to decrease, which is called thermal compression. The shrinkage of the arc column has greatly increased the current density and enhanced the magnetic shrinkage effect, which is called magnetic compression. Under the action of three kinds of compression, the energy concentration of the plasma arc (energy density can reach 105 ~ 106W/cm2), the temperature is high (the center temperature of arc column is 18000 ~ 24000K), and the flame flow rate is large (up to 300m/s). These characteristics make plasma arc widely used in welding, spraying, surfacing and cutting. The characteristics of plasma arc Due to the characteristics of plasma arc, the following features are compared with the tungsten electrode argon arc welding. (1) the plasma arc energy concentration and temperature is high, and the small hole effect can be obtained for most metals in a certain thickness, which can be fully fused and the reverse forming uniform weld. (2) the stiffness of the arc is good, only 5 ° or so, the spread of the plasma arc Angle is basically cylindrical, arc length changes on the workpiece heating area and current density on the influence is small. Therefore, the change of arc length of plasma arc is not obvious to weld forming. (3) welding speed is faster than tungsten electrode argon arc welding. (4) be able to weld finer and thinner parts. (5) the equipment is more complex and expensive, and the matching of process parameters is more complicated. The type of plasma arc According to the power connection mode, the plasma arc h