Abstract
Tests with a 26 pet Cr ferritic stainless steel have shown that this alloy exhibits excellent weldability and corrosion resistance provided that the concentration of carbon plus nitrogen is in the range of 150 ppm or below. Thermodynamic calculations predict that these low carbon and nitrogen concentrations are attainable with reduced pressure and by gas rinsing. Levitation melting experiments were performed to show that under conditions of intense surface stirring, large metal surface area to volume ratio, and high rinsing gas flow rate, very low nitrogen contents approaching theoretical equilibrium concentrations can be reached. Experiments in which methane, hydrogen and argon were purged through a 30 lb. vacuum induction furnace showed that nitrogen levels below 100 ppm can be reached. However, the required purging times are lengthy and limit the commercial practicality of this method.
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