Plasma arc cutting is a process in which a gas-constricted arc is employed to produce a high temperature, high velocity jet at the base metal. During cutting with a stationary arc the base metal is penetrated completely and a hole is formed at the point of the torch that is moved along as the cutting progresses. This phenomenon is called keyholing.
The broad objective of this study is to analyze the keyholing phenomenon by a numerical method. To do this the transfer characteristics of plasma energy to the metal was investigated by using a simplified model for calculating the heat input from plasma. The convection was shown to be extraordinarily important in heat transfer mechanism of arc plasm. About 18 to 42% of the total power input of the arc (VI) was convectively transferred to the base metal during forming the keyhole.
The temperature distribution of the solution domain was calculated using a body-fitted coordinate system in which coordinate lines are coincident with all boundaries. For generating the coordinate system the successive over relaxation method was adopted and the solution of the heat conduction problem in the base metal was solved by using the alternative directional implicit scheme of the finite difference method.
The theoretical prediction of the transient temperature and keyhole shape were compared and discussed with experimental results. The keyholing process could be accurately predicted by using the proposed model but the measured temperature histories showed a considerable discrepancy from the calculated results.
