Development of a Technology for the Production of Vacuum-Degassed Steel with an Increased Nitrogen Concentration

A method of producing nitrogen-alloyed steel is considered. The nitrogen alloying technologies based on the use of nitrided ferromanganese and nitrogen purge gas are analyzed and compared to choose the most effective one for the TAGMET conditions. To produce SA 20A steel with a regulated nitrogen content (100-300 ppm), it is proposed to purge metal with nitrogen and argon during treatment in a ladle furnace and during and after degassing. Proprietary software controlling the purging of steel with nitrogen and argon from the control panel of the ladle furnace and the vacuum degassing unit has been developed. This ensured effective control of the nitriding process and achievement of the required nitrogen content in steel. Changing over from alloying with nitrided ferromanganese to purging with nitrogen gas made it possible to eliminate the pyroelectric effect and to reduce the secondary oxidation and contamination of steel with non-metallic inclusions.