Papers by Author: Mao Fa Jiang

Abstract: The separation of niobium and iron from the low grade niobium ore was researched by the technology process of reductive roasting and magnetic separation. Experiments of reductive roasting and magnetic separation were carried out in order to investigate the separation effect at different conditions of roasting temperature and addition amount of coal powders. The results show that the separation of niobium and iron can be realized, meanwhile the niobium can be enriched in the magnetic tailings. The main mineral phase of niobium in magnetic tailings changes into NbC from (Ce,Nd)NbTiO₅ when the roasting temperature exceeds 1150°C. By magnetic separation after roasting with adding 37.5% coal powders at 1050°C, w(T.Fe) of the reduced iron is 86.11%, the percentage metallization is 87.6%, and the yield ratio of iron is 77.4%. Meanwhile, w(Nb₂O₅) of the magnetic tailings is 7.35% which is 2.4 times higher than low grade niobium ore, and the yield ratio of niobium is 98.1%.

Abstract: The mixture calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. The calculation results show that the required total consumption of chrome ore, coke and limestone in the smelting reduction process is 224.942 kg, 154.9 kg and 99.223 kg, respectively, under the conditions of this calculation. The total amount of slag includes the amounts of hot metal elements oxidation into slag, lining erosion into slag and chromium ore, coke and adding flux into the slag, which is calculated respectively according to the basic raw data and the set values of process parameters. The slag component is confirmed, namely, the actual basicity w(CaO)/w(SiO2)=2.6, the percentage of CaF2 in slag is 3~4 wt%, and the calculated w(MgO)/w(Al2O3)=0.7. In the actual production, the addition of chrome ore, coke and flux is increased by 3%, 2% and 1%, respectively.

Abstract: The production process of stainless steel by chromium ore smelting reduction and direct alloying is an important and advanced way to raise the productivity of stainless steel, decrease the production cost, save electric energy and improve the economic profit. The material balance calculation of producing stainless steel crude melts by chromium ore smelting reduction in a 150 t converter is carried out by use of the empirical data and the calculation method of refining plain carbon steel in a converter, according to the blowing conditions of 185 t smelting reduction converter of No.4 steelmaking shop in Chiba Works of JFE Steel. It includes the actual oxygen consumption, furnace gas composition and occurrence amount, mass calculation of stainless steel crude melts and preparation of total material balance table. The absolute error of material balance is -2.859 kg and the relative error is -0.169%. The error is very small, so the material balance calculation can provide certain quantitative basis for determining reasonable design parameters and increasing smelting technology economic indicators.

Abstract: Utilizing Pakistan chromite as raw material, the rapid leaching of chromium and iron could be realized by the sulfuric acid leaching process on the condition of atmospheric pressure and the addition of oxidant A. And the leaching rate of chromium and iron would be 98.5% and 71.9%, respectively. The sulfuric acid leaching processes with different temperature were systematically studied by chemical analysis and phase analysis. The results showed that, with the increase of reaction temperature, the leaching rate of chromium would increase gradually, but the leaching rate of iron increased at first and then decreases and reached its maximum at 140°C. When the temperature > 160°C, the phases of the leaching residue were magnesium iron silicate and a few of silica, no chromohercynite, chrompicotite and magnesioferrite existed in the chromite. The leaching solution of sulfuric acid leaching process could be used for preparing the basic chrome sulfate, and there is no Cr⁶⁺ in the leaching residue and solution. The results would provide theoretical guidance for solving environmental pollution problem of Cr⁶⁺ in traditional chromate production process.

Abstract: Based on the silicate structure theory, the molten slag structure and the existential state of and during micro-carbon Cr-Fe alloy production process were analysised, and then their diffusion coefficients were calculated. The results showed that, during the initial stage, the average diffusion coeffecient of and is close to the , the reaction process is controlled by the diffusion of () and corporately, during the later stage, the diffusion coefficient of is less than average diffusion coefficient of and , the controlling step is the diffusion of . According to the evolution of diffusion coefficient, molten slag composition optimization method was advised to increase the diffusion ability of and for enhancing the reaction efficiency and the recovery rate of chromium.

Abstract: Effects of TiO₂ on crystalline phase of mold fluxes were studied by the mineral phase microscope and the XRD. The results showed that on the experimental condition, the main crystalline phase of mold fluxes were cuspidine, wollastonite and melilite. When TiO₂ added into the mold fluxes, perovskite would be found. TiO₂ promoted Perovskite to crystallization and limited Cuspidine to growth. The morphologies and content of wollastonite and melilite were greatly affected by TiO₂ adding, especially, as 20% TiO₂ added into the mold fluxes.

Abstract: The effects of Li2CO3 on melting temperature, viscosity, fluidity, surface tension and Al2O3 inclusion adsorption of mould flux for high speed continuous casting were studied. The results showed that with the increase of Li2CO3 content, melting temperature, viscosity and viscous activation energy of mould flux decreased obviously, fluidity increased, surface tension changed little, and Al2O3 inclusion adsorption of mould flux increased. In order to play an effective role, the Li2CO3 content should be less than 4 per cent. The results will play a guiding role in designing of mould flux for high speed continuous casting.

Abstract: Selective Reduction of Cold Bound Pellet – Smelting Separation – Ferroniobium Smelting Technology’ is an effective enrichment and extraction process of Nb from iron tailings of Bayan Obo deposit. Theoretical basis for the thermodynamic feasibility of smelting separation process was provided aiming at the thermodynamic problems in the process by analyzing and calculating through thermodynamic diagram, isothermal equation, and the calculation model of activity for slag system of CaO–SiO₂–FeO–CaF₂–TiO₂–La₂O₃–Nb₂O₅. The results show that the separation of iron and Nb in arc furnace by smelting separation is feasible. In smelting separation process the valence state of Nb in slag is mainly pentavalent and the activity coefficient of Nb₂O₅ is 0.4×10^-5~5.8×10^-5. The distribution ratio of Nb between slag and molten iron decreases with increasing temperature or [%C], whereas increases with increasing basicity (CaO/SiO₂). The temperature should be controlled under 1450°C, the basicity (CaO/SiO₂) should be elevated appropriately, and [%C] should be controlled under 3.6% at the final stage of smelting separation process.