IMPROVING TECHNOLOGY FOR MELTING HIGH-ALLOY PRECISION ALLOYS

When producing high alloy, iron-nickel base and iron-nickel-cobalt base precision alloys containing small amounts of elements having an affinity for nitrogen and oxygen, there is an increased tendency towards 'rising' ingots and the appearance of blowholes. With a view to improving the quality of the metal, the optimum technology for melting 80NKhS alloy in 5t electric furnaces was developed. The authors reach the conclusion that nitrogen is the main cause of these defects in ingots. They consider different methods of preventing nitrogen from entering the metal, for instance with the ferroalloys. An effective method of preventing 'rising' ingots and blowholes by optimum deoxidation is described.