LAUSR

Phosphorus in steel is detrimental element for mechanical properties and dephosphorization treatment of hot iron is necessary to produce high-grade steel products. Dephosphorization treatment using CaO–SiO2–FeO flux has been studied by many researchers1–5) and fluorite is found an excellent slagging promotion agent. However, its use is currently limited owing to stringent environmental regulations. As a result, it is difficult to attain a high dephosphorization ratio due to low basicity of slag. Ban-ya et al. studied alumina, Al2O3, as a substitute of fluorite and showed that the CaO–Al2O3–FetO flux has sufficient dephosphorization capability where Al2O3/CaO is as low as 1/9.6) Based on these results, one of the present authors performed hot iron dephosphorization experiments using the CaO–SiO2–FeO–Al2O3 flux at 2 kg crucible-type and 2 t converter-type tests and attained a high dephosphorization ratio under the condition that (CaO)/(SiO2) is 1.6–2.0 and (A2O3) is 5–10 mass%.7,8) However, high dephosphorization ratio was not attained when the basicity of the charged flux was above 2.0 because observed slag basicity did not rise over 2.0 owing to the low temperature of the hot iron below 1 673 K. Development of Hot Metal Dephosphorization with Lime Powder Top Blowing: Part 2. High Blowing Rate