Steel refinement by injection of powdered materials

The paper presents results of application of the developed complex technology of refinement of high-duty alloy structural steels by injection of powdered materials in an arc furnace or ladle for deep dephosphorization, desulphurization and correction of carbon content. Fundamentals of deep dephosphorization technology are formulated, including the composition, consumption and granulometry of dephosphorizing mixture, composition and temperature of metal, position of tuyere and intensity of blowing, in order to decrease phosphorus content to trace levels and obtain phosphorus concentration in metal product not greater than 0.005 % after 5-6 min of mixture injection by a jet of oxygen. Subsequent deep desulphurization is achieved by injection of powdered mixture to the ladle by a jet of argon. Effect of composition and consumption of desulphurizing mixture on completeness of sulfur removal is considered. Addition of high active reagents (alloys of aluminium and calcium) to the slag mixture of lime and fluor-spar significantly accelerates and increases the degree of desulphurization and provides after a short time of blowing the sulfur content of about 0.002 %. It is also shown that injection of coke powder permits to solve the problem of correction of carbon content in steel, which is especially important for high-power arc furnaces. Application of complex technology of steel treatment by injection of powdered materials in the furnace and ladle yields stable low contents of phosphorus (≤ 0.005 %), sulfur (≤ 0.003 %) and non-metallic inclusions.