铝热还原制备高钛铁的热力学和动力学

对金红石、钛铁矿、铝粉体系热力学进行了计算.结果表明:以Al、Ca、Mg、Ba、Li、Na等金属做还原剂是可行的,标态下反应的吉布斯自由能变化都很负,可以选用这些金属的合金作为复合还原剂.DSC动力学分析结果表明:Al还原TiO2、Fe2O3在1 000 ℃左右开始进行,而Al还原TiO2、Fe2O体系中添加CaO,反应滞后,在1 236 ℃左右发生反应.     

Oxygen content of high ferrotitanium prepared by thermite method with different melt separation temperatures

High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content(≥10 wt%)because of the short slag-metal separation time.In this study,CaO and CaF_2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation.The thermodynamics of the step-by-step reduction process of TiO_2 in the Ti-Al-Fe-Si-O system whose composition is close to the alloy after melt separation were calculated.Samples of alloys and slags before and after melt separation were systematically analyzed.The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO_2.The O content of the alloys slightly decreases with temperature from 1873 to 2023 K,which agrees with the changes in the law of deoxidation limit.It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction.The addition of Al_2 O_3-CaO-CaF_2 slag and high temperature promote the removal of Al_2 O_3 and titanium suboxides.The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%,respectively.     

Tensile deformation behavior of coarse-grained Ti-55 titanium alloy with different hydrogen additions

The effect of hydrogen addition on the deformation behavior of coarse-grained Ti-55 alloys(～20 μm)was studied by uniaxial tension tests at high temperature.The elongation of hydrogenated Ti-55 titanium alloy firstly increases and then decreases with hydrogen content increasing at 875 0 C.The highest elongation of 243.8% is obtained in the hydrogenated alloy with 0.1 wt% H,and the peak stress reaches a minimum value of 29.0 MPa in the hydrogenated alloy with 0.3 wt% H.Compared with that of the unhydrogenated alloy,the elongation of the hydrogenated alloy with 0.1 wt% H increases by 41.3%and its peak stress decreases by 40.6% at 875℃.Hydrogen addition can promote the transformation of β phase and the dislocation movement.Appropriate hydrogen content can evidently improve the deformation properties of coarse-grained Ti-55 titanium alloy.     

碳化法制备复合钛白实验研究

在轻质CaCO3的制备过程中,当碳化率为80%左右时,先后加入钛白浆料和Na2SiO3.9H2O,获得的复合钛白颜料综合性能指标与锐钛型钛白相当。研究了不同TiO2加量时的颜料性能,结果表明,从经济性考虑,TiO2加量为25%时,白度为97.69,遮盖力为37g/m2,吸油量为35g/100g,综合性能符合复合钛白颜料使用性能的需求。     

Corrosion behaviour of as-cast ZK40 with CaO and Y additions

The microstructures of as-cast ZK40, ZK40 with 2% (mass fraction) CaO and ZK40 with 1% (mass fraction) Y were investigated, and the intermetallic phase morphology and the distribution were characterised. By having discrete intermetallic particles at the grain boundaries for the ZK40, the microstructure was modified to a semi-continuous network of intermetallic compounds along the grain boundaries for the ZK40 with CaO or Y additions. The CaO was not found in the microstructure. However, Ca was present in Ca₂Mg₆Zn₃ intermetallic compounds which were formed during casting. Hydrogen evolution and electrochemical impedance spectroscopy tests revealed that the addition of CaO slightly enhanced the corrosion resistance whereas Y had a negative effect on the corrosion resistance of ZK40. Immersion tests showed that severe localised corrosion as well as corrosion along the intermetallic compounds played an important role in the corrosion process of ZK40–Y whereas the localised corrosion was not pronounced for ZK40 or ZK40–CaO alloys. Micro-segregation in the α-Mg matrix was notably higher for the ZK40 alloy compared with the modified alloys. The combination of this effect with a possible formation of a more stable corrosion layer for the ZK40–CaO was attributed as the main reason for an improved corrosion resistance for the ZK40–CaO alloy.     

Multistage desulfurization mechanism to reduce sulfur content of high ferrotitanium prepared using thermite method

High ferrotitanium is used as a deoxidizer and alloying agent in steelmaking processes and is mainly produced using high-cost remelting processes.The ther-mite ...     

自蔓延还原合成BN反应机理

结合差热分析,通过研究Ｂ２Ｏ３和Ａｌ在不同温度下的反应以及在不同氮气压力中的自蔓延实验,搪塞了Ｂ２Ｏ３－Ａｌ－Ｎ２体系自蔓延还原合成ＢＮ的反应机理。结果表明：铝热还原Ｂ２Ｏ３的反应是一个分步过程,低于８２０℃时,Ｂ２Ｏ３与Ａｌ２缓慢反应生成Ａｌ４Ｂ２Ｏ３;高于８２０℃时,Ｂ２Ｏ３与Ａｌ剧烈反应生成Ａｌ４Ｂ２Ｏ９;高于１０５０℃时,Ａｌ与在低温生成的Ａｌ４Ｂ２Ｏ９反应生成Ａｌ１８Ｂ４Ｏ３３;在更高的     

The pre-alloyed powder metallurgy of titanium with boron and carbon additions

Discontinuously reinforced titanium alloys have been produced by gasatomizing Ti-6Al-4V (in weight percent) with additions of boron and/or carbon to make a pre-alloyed, in-situ reinforced titanium-alloy powder. The rapid cooling that takes place during atomization results in a fine and uniform dispersion of titanium carbide and titanium boride. The atomized powder can be consolidated using standard titanium powder consolidation methods such as hot isostatic pressing or extrusion and further processed to produce standard mill forms. Mechanical properties of the consolidated product show room-temperature tensile strengths up to 1,470 MPa with an elastic modulus of approximately 140 GPa. For more information, contact C.F. Yolton, Crucible Research LLC, 6003 Campbells Run Road, Pittsburgh, PA 15205; (412) 923-2955; fax (412) 788-4665; e-mail cfyolton@crucibleresearch.com.     

镁热还原自蔓延高温合成硼化钛微粉的动力学

应用DTA技术分别测定了Mg与TiO2,Mg与B2O3及Mg与TiO2和B2O3之间的多相反应,分析了Mg,TiO2和B2O3三相可能存在的反应机制,应用Freeman-Carroll法和Kissinger法计算了反应的活化能和反应级数。结果表明Mg-B2O3-TiO2之间的反应为复杂的固-液-液反应,TiO2与Mg之间的固-液反应放出的强大热量诱发了B2O3和Mg之间的液-液反应,而Ti与B间的反应放出的热量反过来又促进前两者的反应。表观活化能在温度段760～858℃为E1=297kJ·mol-1,相应的反应级数分别为n1=0.8。采用Kissinger法计算的反应级数为0.9,与Freeman-Carroll法所得的n1=0.8基本一致。     

盐酸法生产高品位富钛料在我国工业化的探讨

介绍了盐酸法生产高品位富钛料的特点、工艺流程和消耗指标 ,论述了盐酸法在我国实现工业化的必要性和可能性。     

Recovery of titania from high titanium slag by roasting method using concentrated sulfuric acid

By means of energy-dispersive X-ray spectroscopy(EDX) and scanning electron microscope(SEM)analysis,the phase structure characteristics of high titanium slag were analyzed.Through the single factor and the orthogonal experiment methods,the effects of material particle size,mass ratio of acid to ore,roasting temperature,and roasting time on the acidolysis ratio of TiO_2during the process of roasting high titanium slag with concentrated sulfuric acid were systematically investigated.The results show that the sequence of each factor affecting the acidolysis ratio of TiO_2 is:mass ratio of acid to ore,roasting time,and roasting temperature.The optimum technological conditions are obtained as mass ratio of acid to ore of 2.1,roasting temperature of 310 ℃,roasting time of 75 min,and material particle size of 45-53 μm.The acidolysis ratio of TiO_2 is over 96%under the optimum conditions.The roasting process is proved to be significant in the exploitation and utilization of high titanium slag.The advantages of the proposed roasting process are of high efficiency,low power consumption,and minimum pollution.     

Ultrasound-assisted preparation of titania-alumina support with high surface area and large pore diameter by modified precipitation method

Titania-alumina supports were prepared successfully using the ultrasound-assisted precipitation method. The resulting supports were characterized by fourier transform infrared analysis (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD) and N₂ physisorption. The effects of precipitants, washing method and the addition of surfactant CTAB were studied. The supports prepared with NH₄HCO₃ showed better textural properties compared with that with NH₃·H₂O, which was attributed to the low NH₄⁺ release rate of NH₄HCO₃. TiO₂-Al₂O₃ support with S_BET = 283 m²/g, V_p = 2.34 mL/g and D_p = 33.0 nm was obtained with this modified precipitation method.     

锻造方式对TC4钛合金小规格板材制备的影响

TC4钛合金小规格板材生产一般采用铸锭镦拔锻造、板坯加热轧制的加工方式进行,对于小规格板材通常锻造时采用镦拔锻造的方式来进行,但组织性能并不能达到相对最优的状态.通过关键过程交叉对比的方式,采用普通自由锻造和镦拔锻造两种加工方式生产出相同尺寸的板坯,再使用相同的轧制工艺进行对比生产,所有的生产环节保持一致性,目的在于探...     

钛粉制取低铁镁的探讨

钛粉能有效地去除粗镁中的铁。粗镁中杂质多,渣量大,精炼中钛粉使用期短,消耗量大,低铁镁产量低。本文介绍的方法是对钛粉制取低镁工艺的改进,低铁镁制取的钛粉消耗明显降低。     

Thermodynamic analysis of production of high purity titanium by thermal decomposition of titanium iodide

High purity titanium was prepared by thermal decomposition of titanium iodide. The feasible synthetic route and optimum decompositon temperaure were obtained by thermodynamic analysis in the process of thermal decomposition of titanium iodide and nucleation growth theory. The temperature for the formation of titanium iodide is in the range of 800–900 K, at which a large amount of titanium iodide vapour can be obtained. The decomposition temperature of titanium iodide is in the range of 1 300–1 500 K, at which a favourable decomposition rate can be achieved. The experiment results show that the purity of the produced titanium is more than 99.995%.     

Martensitic transformation in titanium alloys with a high damping capacity

Results of an x-ray diffraction analysis of the lattice parameters of martensite in titanium alloys are used to refine the crystallography of the martensitic transformation, which has made it possible to explain the extremal dependence of the internal friction on the temperature of heating for quenching. Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 29–31, May, 1998.