INVESTIGATIONS ON THE RAPID SOLIDIFICATION OF STEEL DROPLETS IN THE PLASMA-ROTATING-ELECTRODE-PROCESS

For a better understanding of the solidification structure of the powd er produced in the plasma-rotating-electrode-process (Prep) a theoreti cal model is developed to calculate the solidification time and coolin g rate. The relative velocity between particle and surrounding medium is the decisive factor in heat transfer. Cooling rates of up to 10(6) K/s can be reached for small particles. To investigate the solidificat ion structure the secondary dendrite arm spacing (Das) of the powders is measured. The relation between Das and solidification time given by Kurz is also valid for Prep. The present paper summarizes the results and describes the mathematical model.