1992 Volume 32 Issue 5 Pages 685-692
Electron beam melting enables to evaporate the volatile alloying elements and remove carbon, oxygen and nitrogen by high-temperature, high-vacuum melting. A rod melting technique with 250 kW EB furnace was applied to stainless steel and high chromium steel.
Evaporation reaction of alloying elements during melting was of the first order and was considered to be rate-controlled by free evaporation. Rate of evaporation of alloying elements was higher for element with higher vapor pressure. Further the speed of evaporation was in proportion to the square root of melting energy of electron beam, and this relation was possible to be derived from Langmuir's equation. Deoxidation and decarburization reactions were enhanced by CO degassing reaction. The removal of nitrogen was remarkably enhanced with increasing amount of the CO degassing reaction, and removal ratio of higher than 30% was possible.
Based on the results above, controlling compositions of melted ingots was made possible, and achievement of high purification of [O]+[C]+[N]≤50 ppm in 25% chromium steel was made possible.
