Advanced Materials Research Vol. 402

Abstract: At present, the nitrogen content in aimed molten steel is 18.32ppm on average in PISCO（Panzhihua Iron & Steel Co.）, and there is big fluctuation for nitrogen content. To solve this problem, factors affected the nitrogen content while blowing is discussed, and a comprehensive nitrogen control technology is formed. Experimental results show that with this technology the nitrogen content in aimed molten steel can be controlled in 15ppm, with the average value is 12.53ppm. The average nitrogen content in aimed molten steel is reduced by 5.79ppm, and nitrogen content of aimed molten steel is well controlled.

Abstract: This paper has studied the formation mechanism of frame-shaped segregation in 40Cr wire rod rolled from bloom by means of the composition measurement, the electron microscopic observation and the energy spectrum analysis method. The results show that the frame-shaped segregation in wire rod originated from the positive segregation in columnar-to-equiaxed grain transition zone of bloom. The main influence factors are the solidification behavior of liquid steel in columnar-to-equiaxed grain transition zone, the temperature gradient of different solidification regions in bloom, the diffusion rate of the solute and inclusions in transition zone and so on. It may reduce the frame-shaped segregation by improving the purity of liquid steel, adopting the electromagnetic stirring in secondary cooling zone and enhancing the cooling intensity of the secondary cooling zone.

Abstract: The effects of four inorganic binders and four organic binders on strength of green pellet containing carbon were studied. The results show that phenolic resin is the best binder, compressive strength and drop strength of preheated pellet are 312.5 N and 15.1 times, respectively, when the matching was 2%. The reason is that chemical adsorption effect occurs in pellet. Strength of wet pellet is mainly maintained by capillary force. However, preheated pellet is mainly maintained by chemical adsorption effect and viscous force. Chemical adsorption effect is better than viscous force.

Abstract: Abstract The feature and formation of and preventive measures against common black and bright slivers on the surface of cold-rolled strip are described. Research reveals that the formation of slivers is closely related to the processes of steel making and rolling as well as conditions of equipment in operation, and, in most cases, due to different factors affecting together. Only when the actual forming mechanism is made clear could effective measures be formulated.

Abstract: In order to understand the equilibrium condition of phosphorus between slag and hot metal saturated with carbon in the high phosphorus hot metal dephosphorization process, the dephosphorization capacity of CaO-FeO*-SiO₂-P₂O₅(15%) -CaF₂(B₂O₃) slag system at 1573 K was studied, by applying the method that phosphorus distribution ratio between slag and solid iron was firstly measured and the one between slag and hot metal was then calculated. The results showed that phosphorus distribution ratio decreased with increase in basicity of CaO/(SiO₂ +P₂O₅), a proper increase in SiO₂ content is helpful to the absorption of phosphorus into slag, an increase in FeO* content from 10.52% to 13.40% resulted in a dramatic reduction of phosphorus distribution ratio from 126.43 to 33.25, by completely substituting CaF₂ with B₂O₃ at 2.5 of basicity and 0.07 of B₂O₃/CaO ratio not only was acquired a high phosphorus distribution ratio of 171, but also was decreased pollution to the environment.

Abstract: The RDI of vanadium-titanium sinter is serious， which has directly affected on BF production. The mineral compositions and microstructure of two vanadium-titanium sinters are studied in this article: Chenggang respectively granulating sinter and common sinter. And the Influent factors on improving the RDI of vanadium-titanium sinter by respectively granulating sintering had been ensured.

Abstract: A process has been developed at the laboratory scale for leaching of vanadium from a vanadium residue using mixed hydrofluoric and sulfuric acid solutions, and NaClO as an oxidant. The extraction studies were carried out using various acid concentrations, liquid/solid ratios, addition of oxidant, reaction temperatures and leaching times. The optimum leaching conditions were then determined. Characterization of the leach residues was carried out by SEM and EDS analysis. Results indicate that the silicates can be effectively destroyed by HF, and the vanadium contained in the vanadium-iron spinel can be leached by the mixed acid solutions. The addition of NaClO enhanced the leaching process by the oxidation of V3+(s) to V4+ and V5+. The leaching efficiency was also improved by raising the leaching temperature, prolonging the reaction rime and using a higher liquid/solid ratio. A vanadium recovery of 81.8% was obtained by the direct acid leaching process

Abstract: To predict the effect of Fe₂O₃ on slag splashing properties in the nickel smelting converter, Factsage software was used to calculate the proportion of the liquid phase and the viscosity for MgO-FeO-Fe₂O₃-SiO₂ melts, the melting temperature was measured using slag column deformation, and the microstructure was also observed. The results show that, when the content of Fe₂O₃ is increased from 13.79% to 24.14%, the liquid phase at 1250°C maintains a high proportion of 82.68% and the melting temperature is below 1200°C; The magnetite and hortonolite with high melting points are considerably increased, and the viscosity rises accordingly. The melting and viscous properties for the slag with high content of Fe₂O₃ were improved by adding MgO. Desired slag splashed layer was formed with the saturated Fe₂O₃ and MgO slag.

Abstract: Leaching of an extracted vanadium residue in sodium sub-molten salt medium was investigated. The significant effects of reaction temperature, particle size of residue, reaction time and NaOH-to-residue mass ratio on vanadium extraction were studied. By the orthogonal experiment study, it can be concluded that the impact order of factors is Tr> t>R according to the significance to the leaching process. Under conditions of reaction temperature 170°C, NaOH-to-residue 4:1, stirring speed 700 rpm, particle size -74 µm and reaction time around 180 min, leaching efficiency of vanadium obtained is higher than 90%. And, the leaching process of vanadium, with activation energy 27.69 kJ•mol-1, is controlled by the chemical reaction-controlled as the following rate equation. ln(1-x)=-kt

Abstract: We realize the goal of removing ammonia nitrogen in ammonium paratungstate crystal parent by using strong sodium tungstate liquid to transform-magnesium salt to take off ammonium thoroughly. The results show that removal rate of ammonia can up to 98.88%, ammonia nitrogen contented in the liquid can down to 0.042g/l. Diluting sodium tungstate solution which has been disposed through the above way can be used to confect liquid before the ion exchange,the liquid with the ion exchange can reach the national effluent standard..