Processes for producing low nitrogen metallic chromium and chromium-containing alloys and the resulting products

Abstract

Processes for producing low-nitrogen metallic chromium or chromium-containing alloys, which prevent the nitrogen in the surrounding atmosphere from being carried into the melt and being absorbed by the metallic chromium or chromium-containing alloy during the metallothermic reaction, include vacuum-degassing a thermite mixture comprising metal compounds and metallic reducing powders contained within a vacuum vessel, igniting the thermite mixture to effect reduction of the metal compounds within the vessel under reduced pressure i.e., below 1 bar, and conducting the entire reduction reaction in said vessel under reduced pressure, including solidification and cooling, to produce a final product with a nitrogen content below 10 ppm. The final products obtained, in addition to low-nitrogen metallic chromium in combination with other elements, can be used as raw materials in the manufacture of superalloys, stainless steel and other specialty steels whose final content of nitrogen is below 10 ppm.

1 - 8 . (canceled) 
     
     
         9 . A metallic chromium or chromium-containing alloy having a nitrogen content below 10 ppm. 
     
     
         10 . A chromium-containing alloy additionally containing an element selected from the group consisting of nickel, iron, cobalt, boron, carbon, silicon, aluminum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, molybdenum, tungsten, rhenium, copper, and mixtures thereof having a nitrogen content less than 10 ppm prepared by a process comprising:
 i) vacuum-degassing a thermite mixture comprising chromium compounds and metallic reducing agents, contained within a vacuum vessel capable of withstanding a thermite reaction, to an initial pressure less than 1 mbar;   ii) igniting the thermite mixture to effect reduction of the chromium compounds within said vessel under reduced pressure;   iii) solidifying the reaction products under reduced pressure; and   iv) cooling the reaction products to about ambient temperature under reduced pressure,
 wherein steps ii) through iv) are conducted under a pressure below 1 bar, and wherein the thermite mixture additionally contains an element selected from the group consisting of nickel, iron, cobalt, boron, carbon, silicon, aluminum, titanium, zirconium, hafnium, vanadium, niobium, tantalum, molybdenum, tungsten, rhenium, copper, and mixtures thereof in their metallic form or as compounds thereof capable of metallothermic reduction.