PLASMA GENERATION FOR THE PLASMA CUTTING PROCESS

This study is an attempt to estimate the overall properties, viz, the thermal power and force, of an intense plasma jet produced by a plasma cutting torch, and to relate the properties of the plasma to the diam eter of the nozzle of the plasma torch and the flow rate of plasma-for ming gas, For cutting metallic plates using a thermal plasma, a narrow plasma jet is produced by means of a transferred electric are between an electrode in a plasma torch and the material to be cut, The power density and pressure exerted by the plasma jet on the material at the region of cut needs to be high so that a straight cut, without dress a t the bottom of the plate, can be obtained. A simple theory to describ e the behavior of the are in a plasma cutting torch has been developed to predict the are radius, pressure, and are voltage at the nozzle ex it as a function of are current for a range of nozzle sizes and air fl ow rates, The results obtained are in good agreement with the measured values for an air plasma cutting torch nominally rated for 100-A oper ation, The relationships between the mass flow rate of plasma gas, pla sma power, and are force have been discussed in the light of design of plasma torches for plasma cutting.