RECENT ADVANCES IN Q-BOP STEELMAKING.

The rapid reactions occurring in the Q-BOP are attributed to a mechanism involving gas-diffusion-limited enhanced vaporization. This mechanism is thought to bring about dephosphorization of the bath to phosphorus levels significantly below those associated with conventional slag-metal equilibria. The rate of oxidation of carbon at carbon levels above 0. 2% is controlled by diffusion of CO//2 in the gas stream to the gas bubble/metal interface. At carbon levels below about 0. 2% the rate of decarburization is believed to be controlled by diffusion of carbon from the bulk metal to the bubble surface. Carbon levels as low as 0. 01% can easily be attained. The ladle hydrogen and nitrogen contents of Q-BOP steel are comparable with the hydrogen and nitrogen contents of BOP steel. The present life of the stationary lining on the 200 t Q-BOP at both the Gary and Fairfield Works of the United States Steel Corporation is about 1 000 heats. A consistent life of more than 1 200 heats now appears to be attainable. The average life of the bottom plugs is currently about 300 heats, with many in the range of 400-550 heats. The goal of 300 heats as the minimum life of a bottom plug appears to be within reach.