Study on Desiliconization and Niobium Conservation in Nb-Containing Hot Metal Pretreatment

To prevent niobium from extracting from the hot metal during desiliconization of hot metal pretreatment,the behavior of desiliconization and niobium-conservation as well as variations of elements in hot metal with time was studied in Nb-bearing hot metal pretreatment in an intermediate frequency induction electric furnace with bottom-blowing oxygen device.The experimental results show that Nb begins to oxidize and removes from the molten iron when the content of silicon decreases to 0.012%,the content of phosphorus is not changed and the desulfurization ratio is up to 83% under the conditions of the molten iron smelted at 1 623 K,blown oxygen at 0.5 m3/(t·min) and covered with a CaO-SiO2-CaF2 slag system in which the basicaty indux of the slag is 4.0;However,in the non-slag experiments with the same factor of oxygen supply intensity [0.5 m3/(t·min)] and the smelted temperature(1 623 K),the content of niobium of the hot molten don′t begin to decrease until the silicon in hot metal reduce to 0.16%,and the sulfur and phosphorus of the hot molten don′t change with the other elements with time in the bottom-blowing oxygen process.So the content of silicon in hot iron in blowing end in the slag smelted process is about 10% of the content of silicon with no slag condition and the desulfurization in the process with the slag is more significant than that with no-slag smelted method.