ZPUSOB RAFINACE TAVENIN ZELEZNYCH KOVU

摘要

1420179 Nitrogen control in refining of molten metal JOSLYN Mfg & SUPPLY CO and UNION CARBIDE CORP 19 April 1973 [20 April 1972] 18900/73 Heading C7D The nitrogen content of molten ferrous metal and alloys thereof (e.g. low carbon iron, carbon steel, stainless steel or iron containing nickel based alloy) is adjusted to any desired level from 10 p.p.m to 90% of the level at which nitrogen at ambient pressure is in equilibrium with the nitrogen dissolved in the melt by injecting during an initial period of decarburization a gas mixture consisting essentially of oxygen and nitrogen (e.g. by injection below the surface of the melt) wherein the percentage of nitrogen is such that the partial pressure of nitrogen in the atmosphere in contact with the melt is greater than the partial pressure of nitrogen in equilibrium with the desired nitrogen content of the melt and injecting through the remaining period of the decarburization a mixture of oxygen and a monatomic gas (e.g. argon) or oxygen, a monatomic gas and nitrogen and continuing injection with a monatomic gas and /or nitrogen and optionally oxygen until the nitrogen content of the melt reaches the desired level. The gas mixture used during the remaining period of the decarburization may have an oxygen to monatomic gas or oxygen to monatomic gas and nitrogen ratio lower than the oxygen to nitrogen ratio used in the first period of decarburization which may be terminated after 50-70% of the oxygen recessory for decarburization has been injected. The decarburized melt may be reduced during the continued injection following decarburization using silicon, aluminium, hydrogen, anmonia, methane, propane or natural gas and desulphurized, deslagged and final composition and temperature adjustments made thereto (e.g. by injecting nitrogen to increase the nitrogen content to the desired level up to within 90% of its equilibrium value).