Effects of embedding direct reduction followed by magnetic separation on recovering titanium and iron of beach titanomagnetite concentrate

Embedding direct reduction followed by magnetic separation was conducted to fully recover iron and titanium separately from beach titanomagnetite(TTM).The influences of reduction conditions,such as molar ratio of C to Fe,reduction time,and reduction temperature,were studied.The results showed that the TTM concentrate was reduced to iron and iron-titanium oxides,depending on the reduction time,and the reduction sequence at 1 200°C was suggested as follows:Fe_(2.75)Ti_(0.25)O_4→Fe_2TiO_4→FeTiO_3→FeTi_2O_5.The reduction temperature played a considerable role in the reduction of TTM concentrates.Increasing temperature from 1 100 to 1 200°C was beneficial to recovering titanium and iron,whereas the results deteriorated as temperature increased further.The results of X-ray diffraction and scanning electron microscopy analyses showed that low temperature(≤1 100°C)was unfavorable for the gasification of reductant,resulting in insufficient reducing atmosphere in the reduction process.The molten phase was formed at high temperatures of 1 250-1 300°C,which accelerated the migration rate of metallic particles and suppressed the diffusion of reduction gas,resulting in poor reduction.The optimum conditions for reducing TTM concentrate are as follows:molar ratio of C to Fe of 1.68,reduction time of 150 min,and reduction temperature of 1 200°C.Under these conditions,direct reduction iron powder,assaying 90.28 mass%TFe and 1.73 mass% TiO_2 with iron recovery of 90.85%,and titanium concentrate,assaying 46.24mass% TiO_2 with TiO_2 recovery of 91.15%,were obtained.     

Magnetizing roasting of leucoxene concentrate

The phase transformations occurring during magnetizing roasting of leucoxene concentrate in the temperature range 600–1300°C are studied. It is demonstrated, that in the temperature range 600–800°C, only iron oxides are reduced to a metallic state; at temperatures above 800°C, combined reduction of iron and titanium oxides takes place. At 1050°C, reduced specimens are represented by the Ti₅O₉ and Ti₆O₁₃ Magnéli phases. The formation of iron metatitanate (FeTiO₃), under reduction conditions and the existence of ferrous iron ions in the Magnéli phases slightly degrade the magnetic properties of the products of magnetizing roasting. In high temperature region (1200–1300°C), a similar effect is exerted by the formation of iron dititanate or anosovite in the system. The possibilities of eliminating the undesired factors decreasing the magnetic properties of the products of magnetizing roasting are determined.     

Reduction Behavior of Panzhihua Titanomagnetite Concentrates with Coal

The reduction behavior of the Panzhihua titanomagnetite concentrates (PTC) briquette with coal was investigated by temperature-programmed heating under argon atmosphere in a vertical tube electric furnace. The mass loss behavior of the PTC-coal mixture was checked by thermogravimetric analysis method in argon with a heating rate of 5 K (5 °C)/ min. It was found that there are five stages during the carbothermic reduction process of the PTC. The devolatilization of coal occurred in the first stage, and reductions of iron oxides mainly occurred in the second and third stages. The reduction rate of iron oxide in the third stage was much higher than that in the second stage because of the significant rate of carbon gasification reaction. The iron in the ilmenite was reduced in the fourth stage. In the final stage, the rutile was partially reduced to lower valence oxides. The phase transformation of the briquette reduced at different temperatures was investigated by X-ray diffraction (XRD). The main phases of sample reduced at 1173 K (900 °C) are metallic iron, ilmenite (FeTiO₃), and titanomagnetite (Fe_3–x Ti _x O₄). The traces of rutile (TiO₂) were observed at 1273 K (1000 °C). The iron carbide (Fe₃C) and ferrous-pseudobrookite (FeTi₂O₅) appeared at 1473 K (1200 °C). The titanium carbide was found in the sample reduced at 1623 K (1350 °C). The shrinkages of reduced briquettes, which increased with increase in the temperature, were found to depend greatly on the temperature. With increasing the reduction temperature to 1573 K (1300 °C), the iron nuggets were observed outside of the samples reduced. The nugget formation can indicate a new process of ironmaking with titanomagnetite similar to ITmk3 (Ironmaking Technology Mark 3).     

Phase equilibria in titanium-rich alloys of the Ti — Fe — Nb — Al system

Isothermal cross sections at temperatures of 750°C and 550°C of the phase diagram of the quaternary system Ti — Fe — Nb — Al in the region of titanium-rich alloys for a constant aluminum content of 5 mass % were plotted using metallography, x-ray diffraction, and local x-ray spectral analysis. In the temperature range 550–750°C in alloys with 5 mass % aluminum, the maximum solubility of iron in α-titanium reaches ∼2 mass % for a niobium content of 3 ± 0.5 mass %. Translated from Poroshkovaya Metallurgiya, Nos. 3–4(412), pp. 27–32, March–April, 2000.     

Oxidation of porous nanocrystalline titanium nitride. I. Kinetics

We used the continuous weighing method to study the oxidation kinetics in air for TiN specimens pressed and sintered from nanocrystalline powders with particle size ≤55 nm. Oxidation was carried out at 500–1000 °C for 240 min. By comparing with the oxidizability of compact titanium, we estimated the total reaction surface S of the porous specimens as a function of their oxidation conditions. The mass of absorbed oxygen Δm was calculated from the mass gain ΔP, taking into account the volatile component N₂. We have shown that the maximum mass gain Δm at 600 °C is due to reaction of oxygen with the largest reaction surface. Within 120 min, external pores close up, S decreases, and then a continuous oxide layer forms in which diffusion of oxygen is slowed down. At 700–800 °C, the process of closing up of the pores is activated, and S decreases by an order of magnitude compared to 600 °C. After the first 40–50 min, a continuous oxide film forms and virtually no further mass gain occurs. As the temperature increases, the oxidation rate increases. At 900 °C, the reaction surface becomes equal to the external surface of the specimen, but the thickness of the scale increases linearly. We hypothesize that for T > 850 °C, counterdiffusion of titanium ions is superimposed on diffusion of oxygen. __________ Translated from Poroshkovaya Metallurgiya, Nos. 1–2(447), pp. 98–103, January–February, 2006.     

Thermal stability of finely dispersed ferromagnetic powders

The oxidation mechanism and kinetics have been examined for finely dispersed powders of iron and compounds containing it and noble and platinum metals; these powders were made by a thermochemical method and examined at 20–400°C. The powders do not change in composition and magnetic characteristics up to 110°C because the surfaces of the particles are protected by iron oxides and carbide. This allows the powders to be used to make materials for medical purposes, since they can be sterilized at that temperature. Translated from Poroshkovaya Metallurgiya, Nos. 5–6(413), pp. 1–4, May–June, 2000.     

Effect of enriching the blast with oxygen on the production cost of pig iron

Conclusion By mathematically modeling the blast-furnace smelting of conversion pig iron with a change in the oxygen content of the blast from 21 to 30% and a change in blast temperature from 800 to 1400°C, it was possible to determine how blast temperature affects the increases that occur in furnace productivity, coke rate, and pig-iron cost when blast oxygen content is increased by 1% within the ranges from 21 to 25% and from 25 to 30%. Under the furnace operating conditions that were examined, the savings in coke realized when the blast is enriched with oxygen decrease as blast temperature increases. In fact, coke rate increases at blast temperatures above 1100°C when the blast is enriched with oxygen in the range 25–30%. The effect of oxygen enrichment on pig-iron cost within this concentration range is negative throughout the range of blast temperatures examined. Adding more oxygen to the blast reduces the production cost of the pig iron only when blast oxygen content is within the range 21–25% and blast temperature is no greater than 1000–1100°C. At higher temperatures, adding more oxygen to the blast is economically inexpedient even within the lower ranges of oxygen content. Moscow State Institute of Steel and Alloys. Translated from Metallurg, No. 5, pp. 43–44, May, 1999.     

Phase composition and structure of composite powders based on solid solutions of SiC and AlN

The structure of SiC–AlN powders is investigated by x-ray diffraction and transmission electron microscopy methods. The powders were produced by joint carbon reduction and nitriding of silicon and aluminum oxide mixtures. The results show that a mixture of solid solutions forms during joint SiC and AlN synthesis at 1700°C, with SiC forming β (3C) and α (2H) modifications with different grain morphology. The fiber form is characteristic of β-SiC, whereas the grains of the solid solution based on SiC have a predominantly equiaxed form. α-SiC grain dimensions are considerablys smaller than those of AlN. Institute of Materials Science, National Academy of Sciences of Ukraine. Kiev Translated from Poroshkovaya Metallurgiya, Nos. 7–8, pp. 81–86, July–August, 1997.     

Oxidation of porous nanocrystalline titanium nitride. II. Scale structure and composition

We have used x-ray phase analysis to study the composition of the products of reaction between oxygen and nanocrystalline powders with particle sizes 15, 40, 55, and 80 nm, and also specimens pressed (and sintered) from them. The powders were oxidized in air at 100°C (400 h) to 500°C (5 min), while the sintered specimens were oxidized at 600–900°C for 15, 120, and 240 min. In all cases, in the initial oxidation step the oxynitride Ti(O_xN_y) is formed, which over time is oxidized to TiO, Ti₂O₃, Ti₃O₅, TiO₂ (anatase) and TiO₂ (rutile). In the range 600–800°C, formation of a continuous oxide layer and conversion of anatase to rutile slows down diffusion of oxygen in the scale. We have established that at 900°C, the growth rate of the scale thickness increases and so the reflections from the oxynitride are barely noticeable on the diffraction patterns taken from the surface of the oxidized specimen. In these diffraction patterns, along with strong reflections from the rutile, we also observed weak reflections from lower oxides and anatase, which may be due to reaction between oxygen and the titanium ions diffused to the scale surface. We have concluded that at T > 850°C, the mechanism for oxidation of TiN changes. This is due to superposition of counterdiffusion of titanium ions on the diffusion of oxygen. __________ Translated from Poroshkovaya Metallurgiya, Nos. 3–4(448), pp. 72–78, March–April, 2006.     

Microstructural change during liquid phase sintering of W−Ni−Fe alloy

The changes of bulk density and microstructures during heating and liquid phase sintering of 98W-1Ni-1Fe compacts prepared from 1 and 5 μm W powders have been observed in order to characterize the densification behavior. The compact prepared from a fine (1 μm) W powder begins to densify rapidly at about 1200°C in the solid state during heating, attaining about 95 pct density upon reaching the liquid phase sintering temperature of 1460°C. The compact prepared from a coarse (5 μm) W powder begins to densify rapidly at about 1400°C in the solid state, attaining about 87 pct density upon reaching the liquid phase sintering temperature. Thus, the skeleton of grains is already formed prior to liquid formation. During the isothermal liquid phase sintering, substantial grain growth occurs, and the liquid flows into both open and closed pores, filling them sequentially from the regions with small cross-sections. The grains subsequently grow, into, the liquid pockets which have been formed at the pore sites. The sequential pore filling by first liquid thus is shown to be the dominant densification process during the liquid phase sintering of this alloy, as has been demonstrated earlier with spherical model pores and as predicted theoretically.     

Development of RuAl-based cast alloys

Heterophase RuAl-based alloys with a β-RuAl + (1–20) vol % ɛ-Ru structure and alloyed with chromium, titanium, and hafnium are produced by vacuum arc melting. The effect of the method of preparing charge materials on their behavior during alloy formation is studied. The effect of a structure on the deformability of the alloys at room temperature is estimated. All alloys exhibit ductility and can be deformed by upsetting at a strain higher than 10–12%. The effect of deformation by upsetting at 800°C and subsequent heat treatment on the structure and properties of the alloys is investigated. The high-temperature strengths of RuAl-, TiAl-, Ni₃Al-, and NiAl-based alloys are compared by measuring their hot hardnesses at temperatures up to 1100°C. The high-temperature strength characteristics of the RuAl-based alloys are higher than those of the Ni3Al-, TiAl-, and NiAl-based alloys over the entire temperature range under study; at temperatures ≥900°C, the hardness of ruthenium monoaluminide is higher than those of the other alloys by a factor of 2–4.     

Formation of Fe3N, Fe4N and Fe16N2 on the surface of iron

In order to clarify the phenomenon of nitride formation on the surface of iron, highly polished specimens of well refined and coarsened iron grains have nitrided in flowing H2 + NH3 gas. The morphology and the conditions for formation of Fe₃N are clarified; it forms only on the surface of {lll}_α or near {lll}_α grains and grows in {112}_α directions during nitriding treatment at temperatures between 450 and 550°C. Fe₁₆N₂ and Fe₄N are also formed preferentially on the surfaces of {00l}_α and {210}_α grains, respectively. It is suggested that these iron surfaces are those satisfying the coherency relationships between nitrides and iron matrices. The morphologies and the formation temperature regions of Fe₁₆N₂ and Fe₄N on the surface of iron are quite different to those observed in iron. In particular, Fe₁₆N₂, which has been generally accepted as metastable in bulk iron below 200°C, can exist even at temperatures from 450 to 500°C when it is formed on the surface of iron.     

Reduction mechanisms of vanadium–titanomagnetite–non‐coking coal mixed pellet

Abstract

Experiments were carried out by testing the specimens of separate layers of iron and coal and single pellets thermogravimetrically in a nitrogen atmosphere to study the non‐isothermal reduction mechanisms of vanadium–titanomagnetite–non‐coking coal mixed pellets. The degree of reduction was measured by the weight loss. The E values of the pellet reduction were calculated based on the mass action law. It was found that with increasing temperature the reduction processes may be divided into four stages: reduction via CO and H₂ from volatiles at 400–650°C, reduction via H₂ and C generated by cracking of hydrocarbon at 650–850°C, direct reduction of carbon via gaseous intermediates at 850–1050°C and direct reduction of carbon above 1050°C.     

High temperature grain growth during slab reheating of oriented 3 pct Si-Fe made using continuous casting

Studies were made into the process behind the excessive grain growth which is observed in continuous cast slabs of both regular and high permeability oriented 3 Pct Si-Fe during reheating from 1230 °C to 1400 °C. These large grains are undesirable because of the greater difficulty incurred in obtaining the suitably uniform and fine primary grain size desired prior to the final high temperature anneal during which the (110) [001] texture is developed. It was found that the driving force for the growth is the subgrain structure which develops due to the strains of solidification and cooling during continuous casting; however, the temperature at which growth initiates is related to the austenite-ferrite phase relationship. The grain growth begins when the austenite which forms during slab reheating decomposes to form highly perfect ferrite which then grows by consuming the strained preexisting (as-cast) ferrite matrix. Data summarizing studies into the energy storage and recrystallization processes which occur with the use of slab breakdown (or prerolling) prior to reheating from 1230° to 1400 °C are also discussed. This paper is based on a presentation made at the symposium “Physical Metallurgy of Electrical Steels” held at the 1985 annual AIME meeting in New York on February 24–28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee.     

Oxidation of porous nanocrystalline titanium nitride. III. Oxidation mechanism

The air oxidation mechanism of nanocrystalline TiN at 500 to 900 °C is examined. It is shown that at t ≤ 800 °C the oxidation of titanium nitride is controlled by the diffusion of oxygen and at t > 800 °C the interdiffusion of titanium ions is observed. The oxidation properties of porous TiN are determined by the chemical interaction of oxygen and the reaction surface, which includes the external surface of samples and the internal surface of the pores into which oxygen penetrates. The time and temperature dependence of the weight increment complies with the porous material oxidation model. Active initial oxidation is due to the interaction of oxygen and large internal surface. Short-term self-heating of porous samples is also possible. At t ≤ 800 °C, the pores are obliterated with oxides with time, the internal reaction surface reduces, an external oxide film is formed, the oxygen diffusion and weight increment slow down, and the process stabilizes. With temperature increase, these processes are activated and lead to a smaller weight increment at the final stage (2 to 4 h) at 800 °C as compared with 600 °C. At t > 800 °C the pore obliteration rate increases, but due to the interaction of oxygen and titanium ions that diffuse into the external scale surface, weight increment continuously increases with both time and oxidation temperature. The phase composition of the scale also affects the oxidation mechanism of porous TiN. Oxynitride of terminal composition plays a protective role; the transformation of anatase into rutile is accompanied by a decrease in the oxygen diffusion rate; Ti₂O₃ formed in pores accelerates their obliteration. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 95–104, 2007.     

攀西地区白马钒钛磁铁矿工艺矿物学探讨

为了查明攀西地区白马钒钛磁铁矿工艺矿物学特征,利用化学分析、光学显微镜、扫描电子显微镜、矿物自动分析仪(AMICS)等先进的分析手段,对白马钒钛磁铁矿矿石展开了深入研究。结果表明,矿石的主要矿物为钛磁铁矿、钛铁矿、钙长石、透辉石和蛇纹石等。矿石中Fe、Ti、V的质量分数分别为25.05%、3.46%和0.13%,可以综合回收利用;其中有74.13%的铁以钛磁铁矿的形式存在,13.16%的铁以含铁硅酸盐的形式存在,有63.72%的钛以独立矿物钛铁矿及钛铁矿(客晶)的形式存在,33.67%的钛以类质同象形式存在于钛磁铁矿中。矿石中钛磁铁矿、钛铁矿和硫矿物均以中粒为主,钛铁矿(客晶)和镁铝尖晶石(客晶)的嵌布粒度绝大部分为微粒,小于0.010 mm。矿石中13.16%的铁赋存于硅酸盐中以及大部分钛磁铁矿中含钛铁矿(客晶)和镁铝尖晶石(客晶),是影响铁精矿品位的主要因素。     

Kinetics of spreading in initial stages in metallic systems with different types of interaction between components. IV. Effect of chemical reaction on the kinetics of spreading in tin—Iron group metal systems

A droplet flowing over onto a plate introduced from above has been used to study the kinetics of spreading and to describe the observable characteristics of spreading of tin on iron, cobalt, nickel, and the intermetallic compounds Ni₃Sn, Ni₃Sn₂ under a vacuum of (2–4)·10⁻³ Pa at 400–1000°C, droplet mass 0.01–0.06 g. We show by a formal kinetic analysis of experimental data that in the low-temperature range (400–500°C) the kinetic regime dominates, and in the high-temperature range (600–1000°C) the inertial—kinetic regime dominates. In spreading of tin on iron, cobalt, nickel, and the intermetallic compounds Ni₃Sn and Ni₃Sn₂, the nature of the interaction corresponds to the phase equilibrium in the studied systems. The results for the kinetics of spreading of tin on nickel and the intermetallic compound Ni₃Sn showed that spreading of the main bulk is preceded by spreading of a precursor film. Deceased. Institute for Problems of Materials Science, Ukraine National Academy of Sciences, Kiev. Translated from Poroshkovaya Metallurgiya, Nos. 7–8(402), pp. 65–72, July–August, 1998.     

Phase composition of the vanadium-containing titanium slags forming upon the reduction smelting of the titanomagnetite concentrate from the Kuranakhsk deposit

The phase composition of the vanadium-containing titanium slags that form upon the reduction smelting of the titanomagnetite concentrate from the Kuranakhsk deposit with an added CaCO₃ flux is studied by optical microscopy, X-ray diffraction, and scanning electron microscopy. The laws of formation of the phase composition and the interphase distribution of vanadium and other elements are revealed as a function the CaO and FeO contents in the slags. It is shown that, at low CaO contents (up to 5%), the phase composition of the slags containing 15–30% FeO is mainly represented by spinelides (Al-V-Cr and Al-Ti-V spinels and (Fe,Mg)₂TiO₄ ulvospinel), anosovite, and glass. When the CaO content in slag increases, titanium is fixed into perovskite. At 17–20% CaO and ≤8.3% FeO in slag, a new crystalline phase, i.e., Ca-Al-V titanate of a complex composition, forms along with perovskite, the Al-V-Cr spinel, anosovite, and glass. Vanadium in the slags is mainly distributed between anosovite, the spinelides, and the Ca-Al-V titanate, and vanadium is absent in the glassy phase.     

Carbothermal Reduction of a Primary Ilmenite Concentrate in Different Gas Atmospheres

The carbothermal reduction of a primary ilmenite concentrate was studied in hydrogen, argon, and helium. Ilmenite and graphite were uniformly mixed and pressed into pellets. Reduction was studied in isothermal and temperature-programmed reduction experiments in a tube reactor with continuously flowing gas. CO, CO₂, and CH₄ contents in the off-gas were measured online using infrared sensors. The phase composition of reduced samples was characterized by X-ray diffraction (XRD). Oxygen and carbon contents in reduced samples were determined by LECO analyzers (LECO Corporation, St. Joseph, MI). The main phases in the ilmenite concentrate were ilmenite and pseudorutile. The reaction started with the reduction of pseudorutile to ilmenite and titania, followed by the reduction of ilmenite to metallic iron and titania. Titania was reduced to Ti₃O₅ and even more to Ti₂O₃, which was converted to titanium oxycarbide. Reduction was faster in hydrogen than in helium and argon, which was attributed to involvement of hydrogen in the reduction reactions. The formation of titanium oxycarbide in hydrogen started at 1000 °C and was completed in 300 minutes at 1200 °C, and 30 minutes at 1500 °C. The formation of titanium oxycarbide in argon and helium started at 1200 °C and was not completed after 300 minutes at 1300 °C.