Refining of high nitrogen steels in a closed pressure vessel

The simultaneous removing of oxygen, sulphur and phosphorus during nitriding with nitriding from a gas phase of the austenitic type (18 % Cr, 9 % Ni) High Nitrogen Steels were investigated. A process named "Plasma Pressure Melting Process" (PPMP) was carried out in the air-tight plasma furnace equipped with the 100 kW D.C. plasma torch. Refining, nitriding and casting of the liquid steels were actualized under elevated pressure inside the furnace - up to 0.5 MPabs. The intensity of the calcium vaporization from the liquid CaF2-Ca flux used as a refining agent was quantified. The relation of [Ca](tot)=f(a[O]) was established based on the measurement results of the oxygen activity in the liquid steel.