Selective enrichment of TiO2 and precipitation behavior of perovskite phase in titania bearing slag

1 Introduction China is rich in mineral resources of titanium, 92.4% of which is vanadium-titanium bearing magnetite, deposited mostly around the southwestern part. About 53% titanium is in the iron concentrate after mineral processing, after smelting pro…     

Kinetics of non-isothermal precipitation process of perovskite phase in oxidized Ti-bearing blast furnace slag

Kinetics of non-isothermal precipitation process and crystal growth of perovskite phase in oxidized Ti-bearing slag were investigated. The oxidized slag was obtained by blowing the air into the molten Ti-bearing blast furnace slag through a lance. The experimental results show that the cooling rate has important effect on precipitation and growth of perovskite phase in oxidized slag; the lower cooling rate is in favor of not only the increase of the volume fraction of perovskite phase, but also the growth of perovskite phase grain sizes. The particle coarsening in non-isothermal process has important effect on the crystal growth of perovskite phase. The relative volume fraction of perovskite phase could be approximately described by JMAK equation, and the experiential expression of the average crystal radius of perovskite phase was also obtained.     

含钛高炉渣中钛组分选择性富集及钙钛矿结晶行为

攀钢含钛高炉渣工艺矿物学分析结果表明 ,钙钛矿是主要的富钛相。采用CaO和Fe2 O3对原高炉渣进行改性处理 ,不仅提高了钙钛矿的析出温度 ,而且使另外两种主要含钛矿物攀钛透辉石和富钛透辉石析出的温度显著降低。在适当热处理条件下 ,近 80 %的钛组分进入钙钛矿相中 ,而且钙钛矿的平均晶体尺寸达 90 μm ,实现了熔渣中钛组分的选择性富集并为选矿分离创造了条件。     

Decomposition of acid dissolved titanium slag from Australia by sodium hydroxide

The kinetics of the decomposition of acid dissolved titanium slag with a sodium hydroxide system under atmospheric pressure was studied. The effect of reaction temperature, particle size and NaOH-to-slag mass ratio on titanium extraction was investigated. The results show that temperature and particle size have significant influence on titanium extraction. The experimental data of titanium extraction show that the shrinking core model with chemical reaction controlled process is most applicable for the decomposition of slag, with an apparent activation energy of 62.4 kJ·mol⁻¹. Approximately 85 wt.%−90 wt.% of the titanium can be extracted from the slag under the optimal conditions. In addition, the purity of titanium dioxide obtained in the product is up to 98.5 wt.%.     

Effect of oxidization on enrichment behavior of TiO2 in titanium-bearing slag

1. Introduction There are around 50 million tons of titanium slag piled up in China. Such slag usually contains about 20%-22% TiO2 and cannot be discarded, so this quantity is still increasing at a rate of 3 million tons per year. However, owing to the dispersed distribu-tion of titanium component in various mineral phases, and very fine grains (<10 μm) and complex interfacial combination, it is very difficult to recover titanium component from the slag by conventional separating technique. …     

Post-mortem analysis of high alumina brick attacked by vanadium and titanium bearing slag after service in torpedo ladle

Abstract

High alumina brick after service in a torpedo ladle was analysed by means of atomic emission spectroscopy, X-ray diffraction, electron probe microanalysis and themochemical analysis in order to determine the corrosion mechanism during industrial application in a steel works. The results showed that slag containing vanadium and titanium oxide is more corrosive than common silica slags, and that this facilitates corrosion and penetration into the high alumina brick. Mineralogical observation confirmed that V₂O₅, TiO₂, MnO and FeO and MgO in the slag reacted with native phases presented in high alumina brick to form complex spinel, corundum and anorthite solid solution, etc. The dissolved content of V₂O₅ in the spinel decreased from 6·08 to 2·78 wt-% from the working face to the inner area. However, the FeO and MnO content in the spinel varied little with a slight increase in the TiO₂ content. The expansion coefficient mismatch between the penetrated zone and cold face zones, which results in densification spalling and increased porosity, play a key role in the failure of the high alumina brick.     

Appropriate titanium slag composition during smelting of vanadium titanomagnetite metallized pellets

The suitable titanium slag composition with high titanium content for electric furnace smelting of vanadium titanomagnetite was investigated through thermodynamics and related phase diagram analysis. According to the thermodynamic results, low-melting-point regions and MgTi₂O₅ primary phase area in the phase diagrams, the suggested titanium slag composition for the present vanadium titanomagnetite metallized pellets should consist of 50% TiO₂, 8%–12% MgO and 13% Al₂O₃ (mass fraction) with a binary basicity of 0.8–1.2. Finally, the verified smelting experiments were conducted and successful separation of the molten iron from the titanium slag is obtained. The obtained vanadium-containing molten iron contains 0.681% V and 0.267% Ti, and the obtained titanium slag contains 52.21% TiO₂ (mass fraction), in which MgTi₂O₅ is the primary phase. The titanium resource in the final titanium slag production could be used to produce TiO₂ pigment by acid leaching methods.     

钙热还原二氧化钛的钛粉制备及其中间产物CaTiO3的成因

通过热力学计算以及XRD、SEM和EDS等测试手段,研究TiO2钙热还原制备钛粉过程中钛酸钙(CaTiO3)的形成原因。热力学计算表明:当温度高于800 K时,添加剂CaCl2水解产物CaO与TiO2生成CaTiO3的反应以及还原副产物CaO与TiO2生成CaTiO3的反应均满足反应发生的热力学条件。实验研究表明:CaTiO3的生成主要是由添加剂CaCl2水解生成的CaO与TiO2烧结反应所致,CaTiO3的量随着CaCl2添加量的增加而增加,且CaTiO3更容易被还原为金属钛。当CaCl2与TiO2的质量比约为1:4时、在1 273 K下还原时间为6 h时,反应过程中的CaTiO3被完全还原为金属钛粉,该粉末具有不规则外形,颗粒粒径为8~15μm。经EDS分析,金属钛粉中钛的质量分数达到99.55%。     

钛渣中TiO2作晶核剂对玻璃晶化的影响

制备了以钛渣和铁尾矿为主要原料,以钛渣兼作晶核剂的微晶玻璃材料,研究了Ｔｉ２含量变化对玻璃晶化的影响。采用ＤＴＡ,ＳＥＭ,ＸＲＤ等技术对该体系的晶化机理进行探讨。结果表明,当ＴｉＯ２含量小于１０％时仅产生表面晶化。而当ＴｉＯ２含量为１０％时可发生整体晶化,其活化能为１９０．６ｋｊ．ｍｏｌ＾－１,动力学参数ｍ＝３,晶体从晶界面呈三维生长。ＴｉＯ２、Ｆｅ２Ｏ３能共同促进晶化,晶体从相界面处生长,析出的     

Preparation of Ti-rich material from titanium slag by activation roasting followed by acid leaching

A method of activation roasting followed by acid leaching using titanium slag was introduced to prepare Ti-rich material. The effects of H₃PO₄ dosage, roasting temperature, and roasting time on TiO₂ grade were investigated. A Ti-rich material containing 88.54% TiO₂, 0.42% (CaO+MgO) was obtained when finely ground titanium slag was roasted with 7.5% H₃PO₄ at 1000 °C for 2 h, followed by a two-stage leaching in boiling dilute sulfuric acid for 2 h. The XRD patterns show that the product is titanium dioxide with a rutile structure. Mechanism studies show that structures of anosovite solid solution and silicate minerals are destroyed in the roasting process. As a result, titanium components in titanium slag are transformed into TiO₂ (rutile) while impurities are transformed into acid-soluble phosphate and quartz.     

Oxidization mechanism in CaO-FeOx-SiO2 slag with high iron content

Oxidization mechanism in CaO-FeOx-SiO2 slag with high iron content was investigated by blowing oxygen into molten slag so as to oxidize Fe（ Ⅱ）. The relationship between Fe（ Ⅱ ） content and oxidizing time at different temperatures was obtained by chemical analysis. Microstructure of slag was observed by metallographic microscope and SEM. Phases compositions were ascertained by EDXS and XRD. Grain size and crystallizing quantity of magnetite（Fe3O4 ） were determined by image analyzer. The oxidizing kinetic equations were deduced. Confirmed by graphical construction method, Fe（ Ⅱ ） oxidizing reaction in CaO-FeOx-SiO2 slag system is of first order, and the reaction apparent energy Eo is 296. 67 kJ/mol in the pure oxygen and 340. 30 kJ/mol in air. The enrichment and crystal growth mechanism of magnetite（Fe3O4 ） phases were investigated. In oxidizing process, content of fayalite declines, while that of magnetite（Fe3O4 ） increases, and iron resources enrich into magnetite（Fe3O4 ） phase. All these provide a theoretical base for compressive utilizing of those slags.     

钛渣中钙钛矿的浮选分离及其机理

研究了捕收剂油酸、羟肟酸、十二烷胺双甲基膦酸 ,抑制剂氟硅酸钠、水玻璃对改性渣中钙钛矿浮选的影响。通过浮选溶液化学计算、矿物动电电位、红外光谱等研究 ,探讨了羟肟酸在钙钛矿表面的作用和水玻璃抑制钛辉石的作用机理。结果表明 :以羟肟酸为捕收剂 ,水玻璃为抑制剂可实现钙钛矿与钛辉石等的浮选分离。钙钛矿和钛辉石晶体表面的Ca,Ti质点密度不同 ,所处的位置及活性不同 ,造成二者浮游性有一定的差异 ;钙钛矿在整个研究范围内 ζ电位始终为负值 ,但在阴离子捕收剂C5-9羟肟酸中可浮性良好 ,表明C5-9羟肟酸在钙钛矿表面发生了化学吸附。红外光谱研究证实 ,C5-9羟肟酸的CN ,N—O官能团与钙钛矿表面的钛质点发生了化学键合。     

Beta phase superplasticity in titanium alloys by boron modification

Addition of boron to titanium alloys produces fine TiB whiskers in situ with excellent thermal stability and good chemical compatibility with the matrix. These whiskers stabilize a fine-grain microstructure by restricting grain growth at high temperatures in the β phase field. The hot deformation behavior in the β phase field (temperature range 1050–1200 °C) of Ti-6Al-4V alloys modified with two different levels of B additions (1.6 and 2.9 wt.%) produced by powder metallurgy was investigated using hot compression tests in the strain rate range of 10⁻³ to 10⁻¹ s⁻¹ and hot tensile tests at a nominal strain rate of 6×10⁻⁴ s⁻¹. The β phase exhibits superplasticity, which occurs due to stabilization of a fine-grain microstructure by the TiB. Matrix grain boundary sliding and β/TiB interface sliding appear to contribute to the β superplasticity. The ability to achieve superplasticity at higher temperatures enable lower flow stresses, improved chemical homogeneity, and high strain rate capability due to enhanced accommodation processes. This paper was presented at the International Symposium on Superplasticity and Superplastic Forming, sponsored by the Manufacturing Critical Sector at the ASM International AeroMat 2004 Conference and Exposition, June 8–9, 2004, in Seattle, WA. The symposium was organized by Daniel G. Sanders, The Boeing Company.     

大功率密闭直流电弧炉冶炼钛渣烟气净化工艺研究

根据国内引进的第一台30MW密闭直流电弧炉钛渣生产线的工艺流程,对采用云南省钛铁矿冶炼钛渣过程中产生的烟气进行了气体及烟尘的流量、含量、化学成分等分析。由于产生的烟气具有温度高、含尘量大(1.75%~9.60%)、SO2含量低、CO含量高的特点,选择烟气净化设备时,除了处理能力要符合生产要求,还需要考虑粉尘粒径和烟气温度这两个因素,以实现烟气回收利用的目的。经过研究,烟气净化工艺首先对烟气进行直接水冷使烟气降温,然后选用德国进口涤气机对烟气进行精处理,除尘效率可以达到99.983%。处理净化后的烟气,热值高,气体性质稳定,净化后可安全用于无烟煤/钛渣干燥及渣包/铁包的烘烤,实现节能减排的目标;烟尘可以回收利用。     

Role of phase transformation in chip segmentation during high speed machining of dual phase titanium alloys

Chip segmentation during machining of titanium alloys is primarily due to adiabatic shear localization associated with thermally driven α–β phase transformation at extremely high speeds. Current constitutive material models used in simulating the machining process ignore the role of phase transformation in shear localization and its influence on the material associated dynamic response. This research presents a new phase approach to chip segmentation that includes a recently developed constitutive material model based on the self-consistent method (SCM) that accounts for material composition, as well as α–β phase transformation, during machining. This SCM-based model is implemented in the finite element framework to validate and predict the effects of starting material property, cutting speeds, uncut chip thicknesses, rake angles, tool radius, and friction coefficients on the strains, temperatures and β volume fractions in chip segmentation. It confirms that cutting speed and uncut chip thickness have great impact, rake angle has less effect, tool radius and friction coefficient have the least effects on chip segmentation. However, tool geometry as well as machining parameters have great influence on the machined surface in terms of temperature magnitude, affected depth and the associated α–β phase transformation.     

熔融钒渣纯氧氧化钙化提钒(英文)

在实验室条件下对熔融态钒渣直接氧化钙化提钒新工艺进行研究。在反应过程中利用纯氧氧化,CaO作为添加剂,硫酸浸出熟料。采用XRD、XPS、SEM及EDS等手段对钒渣熟料进行分析,考察不同CaO/V2O5质量比与硫酸浓度对熟料中钒浸出的影响,并与现行焙烧工艺在能耗方面进行对比。结果表明:钒渣熟料中形成了钒的富集相,钒渣的氧化钙化产物主要为CaV2O5和Ca2V2O7,并对钒酸钙的形成机理进行了阐释;XRD和XPS分析得出熔渣中钒的氧化反应在供氧充足的情况下存在一定限制,CaO的增加能促进五价钒在熔渣中的稳定;在优化的实验条件下(CaO/V2O5质量比0.6,粒度120~150μm,浸出时间2 h,浸出温度90°C,液固比5:1 mL/g,H2SO4浓度20%,搅拌强度500 r/min),钒的浸出率能达到90%;能耗计算得到每处理1000 kg钒渣,利用新工艺可以节约能量1.85×106 kJ。实验与计算结果验证新工艺是一种节能减排的提钒手段。     

异种材料淬火过程的有限元模拟

钛合金扩散焊接轴承钢材料由于含有钒、铜、镍中间层,在淬火过程中容易从多层材料界面处开裂.因此利用纳米显微力学探针测量了材料的弹性模量,然后采用ANSYS有限元软件对淬火中钛合金焊接轴承钢材料进行了有限元(FEM)模拟,根据得到的温度场以及应力场分布,找出了容易诱发界面处产生裂纹的原因.模拟表明淬火初期由于整体材料发生收缩而引起整体热应力的增加,淬火后期由于轴承钢发生马氏体相变,轴承钢体积开始膨胀,组织应力相应增加,抵消了一部分热应力的值,最终部件的残余应力是这两种应力共同作用的结果.高的淬火温度,增加了淬火过程中试件内部的应力值,容易引起过渡层处产生微裂纹从而导致局部开裂,因此,合适的淬火温度应取在830～860℃范围内且尽可能取偏其下限.     

Synthesis of titanium carbide by induction plasma reactive spray

A novel method capable of sufficient mixing of titanium powder and methane of carbon source was developed in the synthesis of titanium carbide by induction plasma reactive spray. X-ray diffraction analysis, optical microscopy, scanning electron microscopy, and microhardness test were used to characterize the spray-formed deposit.The experimental results show that both primary carburization of the titanium particles inside the plasma flame and secondary carburization of the growing deposit on high temperature substrate contribute to the forming of titanium carbide. The transitional phase of TiC1-x has the same crystal structure as TiC, but has a slightly low lattice constant. The deposit consists of fine grain structure and large grain structure. The fine grain structure, harder than large grain structure, shows grain boundary fracture.