| 摘要 |
PURPOSE:To manufacture of the title ferrochrome by subjecting low-carbon ferrochrome to nitriding, thereafter to iron removing treatment by dissolving with acid and successively to denitrifying treatment by vacuum heating. CONSTITUTION:Low-carbon ferrochrome contg., by weight, >50% Cr, <1.0% C and the balance essential Fe with Si and Co is crushed into the shape of grains of <=3mm and is thereafter heated to 1000 to 1300 deg.C in a heating furnace in the atmosphere of N2 gas to execute nitriding treatment. The nitrided ferrochrome is constituted of a phase of ferrochrome nitride essentially consisting of Cr2N and a metallic phase contg. 10 to 20% Cr, small amounts of Si and Co and essential Fe, and it is furthermore crushed into the size of 0.3 to 3mm and is subjected to secondary nitriding treatment to convert Cr2N into CrN. It is subjected to acid treatment in 8 to 25% proportion by outer ratio to sulfuric acid of 1 to 3N to remove Fe in the metallic phase by dissolving, which is thereafter neutralized and cleaned by aqueous ammonia. It is then mixed with about 0.7% carbon and the mixture is heated to 1250 deg.C in vacuum to subject the ferrochrome nitride to denitriding treatment, by which the high Cr-contg. low carbon ferrochrome contg. 70 to 95% Cr can be manufactured. |
