The electroslag remelting of high-nitrogen steels

Steels containing nitrogen at levels which are at or above the 1 Bar saturation solubility limit in the liquid at the liquidus temperature offer considerable metallurgical property advantages in many respects. For example, when nitrogen is used as a substitute for carbon in stainless grades, the alloys have superior corrosion properties especially in biomedical applications: nitrogen as a strengthening element in tool steels offers advantages in freedom from carbide particles which affect the polishability. Most of the steels grade of interest require electroslag remelting to control segregation without loss of nitrogen and the behaviour of nitrogen during this process is the subject of this work. It is concluded that the required process pressures are closely related to the alloy composition and that to prevent porosity in the product the ESR step must be carried out at an appropriate overpressure of either nitrogen or argon. The addition of nitrogen during ESR is also discussed and it is shown that this is possible only through solid additives. (C) 2004 Kluwer Academic Publishers.