A contribution to the Development of a Continuous Oxygen Steelmaking Process

Abstract

Results obtained with our experimental 5-tph shallow-bath reactor, or forehearth, demonstrated that continuous steelmaking by the progressive oxygen lancing of a hot metal stream is technically feasible. Carbon, silicon, manganese, phosphorus, and sulfur are removed as a function of distance along the furnace, and metal composition and temperature gradients are well defined. Ease of access to the bath permits rapid measurement of metal carbon and temperature with frequency required for process control. By controlling input variables and end-point temperature, steels have been produced with carbon concentrations ranging from the 0.03 to 1.10%. Product sulfur and phosphorus concentrations of less than 0.02 and 0.01%, respectively, have been attained. The cost of metallics, fluxes, and oxygen per net ton of product is comparable to that of other modern oxygen steelmaking processes. Although the technical feasibility of the process with parallel slag-metal flow has been demonstrated, more extensive testing on a larger scale would be required before it could be considered for commercialization. For example, experimental difficulties were encountered in maintaining steady carbon in the product and in utilizing ore efficiently in the process. Hot metal input to the small forehearth could not be controlled closer than ±10% of the target rate of five tons per hour, and consequently the variation in product carbon ranged from ±0.03 to ±0.12% C. In the runs where control of bath temperature was attempted, only about 35% of the ore was accounted for in the bath, the balance remaining in the slag. In addition to efficient utilization of iron and oxygen units from iron ore, the process economics would require the development of materials or techniques to extend refractory life. Use of prepared scrap as a coolant instead of iron ore would increase the versatility of the process. Also, counter slag-metal flow2,8 might be used to advantage for lowering residual sulfur and phosphorus and for increasing product yield.