Development of Hydrogen Gas Injection Method for Promoting Decarburization of Ultra-low Carbon Steel in RH Degasser

摘要

Kawasaki Steel has developed a hydrogen gas injection method at the RH degasser for promoting the decarburization reaction of the ultra-low carbon steel in the range of a carbon content of less than 20ppm. Hydrogen gas is blown into the molten steel in the snokel of 260-t RH at Chiba Works in the later period of decarburization treatment at a flow rate of up to 4 m~3-norm/min. Part of the hydrogen gas is dissolved in the molten steel to raise the hydrogen concentration of the molten steel up to about 3 ppm, which promotes the evolution of gas bubbles in the molten steel in the vacuum vessel and increases the inter-facial area between the gas and metal. The apparent rate constant of decarburization in the range of carbon content from 20 ppm to 10 ppm is increased from 0.05 min~(-1) to 0.1 min~1 by this method. The carbon content can be decreased to 7 ppm in average in 25 min of decarburization treatment. Ultra-low carbon steel of [C]≤ 10 ppm can be obtained with certainty in 25 min of decarburization treatment.