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.     

Solidification microstructure of high borated stainless steels with rare earth and titanium additions

To study the effects of rare earth(RE) and Ti on the solidification micros true ture of high borated stainless steels,1.6 wt% B stainless steel doped with RE and2.1 wt% B stainless steel doped with Ti were prepared by ingot casting,respectively.The solidification microstructure of researched steels was characterized in detail.The modification mechanism was clarified based on the heterogeneous nucleation theory and the thermodynamic calculation.The solidification microstructure of 1.6 wt% B and 2...     

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。     

不同高浓度气体对金刚石薄膜制备的影响

采用微波等离子体化学气相沉积(MPCVD)法,分别制备了CH4/H2体系、CH4/H2/N2体系以及CH4/H2/Ar体系金刚石薄膜。主要采用了扫描电子显微镜(SEM)、激光拉曼光谱(Raman)和X射线衍射光谱(XRD)等方法对不同体系中制备的金刚石薄膜的晶粒尺寸及其品质进行了分析,研究了不同高浓度气体对金刚石薄膜的影响。结果显示:利用高浓度的甲烷可以在很大程度上细化晶粒,制备出纳米晶金刚石薄膜,但是薄膜的非晶相较多,品质下降;加入70%N2,薄膜中的金刚石晶粒生长速度较慢,但可制备出均匀的纳米晶金刚石薄膜;70%的Ar气氛中,金刚石晶粒生长较快,制得的薄膜中的金刚石晶粒是微米级别的。     

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.     

多级深度还原法直接制备钛粉

针对传统钙、镁等金属热还原TiO_2制备金属钛粉过程存在的效率低、脱氧不彻底的技术瓶颈,基于TiO_2分步还原的热力学平衡特点,结合镁钙电负性差异,提出了多级深度还原法直接制备钛单质的工艺:即TiO_2先镁热自蔓延一次还原得到一次还原产物,然后将一次还原产物进行钙热深度还原制备还原钛粉。采用对比研究法,考察了TiO_2镁热还原和钙热还原的热力学及动力学差异;考察了镁热一次还原过程中TiO_2机制与还原程度,以及一次还原产物不同深度还原模式下脱氧机制。结果表明:一次还原产物先酸浸预除杂,然后进行钙热深度还原更利于彻底脱氧,最终制备出氧含量仅为0.21%(质量分数),纯度99.0%可以商用的钛粉。     

低成本高性能粉末冶金钛合金

粉末冶金是短流程制备低成本、高性能钛及钛合金的有效方法。低成本氢化脱氢（HDH）钛粉可用于制备粉末冶金钛合金制件,但由于受间隙原子含量高、烧结致密度低和微观组织粗大等因素影响,使粉末冶金钛制品的组织性能优势得不到发挥。实验采用氢化脱氢钛粉—冷等静压—真空烧结的技术路线制备了Ti-6Al-4V烧结坯,间隙原子含量低（O<0.16 wt.%, N<0.05 wt.%, H<0.015 wt.%）,具有均匀细小的近等轴?组织,良好的室温拉伸性能（UTS>930 MPa, YS>870 MPa, El>14%）。实验同时表明了HDH工艺制备低间隙原子含量钛粉的可行性,间隙原子含量的增加主要源于粉末及压坯的操作、转移和储存过程。得益于粉末冶金钛合金的细晶和近终成形特点,它无需通过开坯锻造,并且近成型的烧结坯能够提高材料利用率,减少后续热加工变形量及加工道次。因此,以粉末钛合金烧结坯替代锻坯进行后续的塑性加工能够大幅度降低钛合金构件及型材的成本。     

熔盐电脱氧法制取Ti的反应机理

通过低电压电解实验、不同阴极电解对比实验和反电动势测定实验,并结合循环伏安法研究了熔盐电脱氧法制取金属Ti过程中阴极的还原过程。结果表明,还原过程是分步进行的。TiO2先被还原为Ti3O5或Ti2O3,再进一步被还原为Ti3O、Ti2O、TiO或金属Ti。另外,阴极进行的主要电极反应是TiO2的直接电还原反应,同时在阴极也存在一定的钙热还原反应,只是反应强度较弱。另外,分别以钼丝和二氧化钛为研究电极,进行了循环伏安曲线测定。     

Microstructures and wear resistance of high boron and low carbon ferroalloy using hybrid powder/ wire overlaying method

The high boron alloy surfacing layer was easily cracked due to its insufficient toughness by using hybrid powder/wire overlaying method. In order to explore the cracked mechanism, the microstructures and the wear resistance of the samples with different boron contents were studied. Further, phases analysis, microhardness, macrohardness and wear test were also carried out. The boron content depended microstructures were observed. The precipitation of the Fe ₂ B, Fe ₃ ( C, B) , Fe ₂₃ ( C, B) ₆ were increased with the increase of boron content. It was found that the wear resistance was independent of the macrohardness as the macrohardness increased firstly and then remained steady at ~ 62 HRC. However, the wear resistance was depended on the boron contents, and which increased with the increase of the boron contents. The abrasive loss mechanism changed from plastic deformation removal to fracture removal.     

氮气保护粉/丝复合堆焊高硼铁基合金的组织及结构

为改善高硼铁基堆焊合金韧性不足、易引发裂纹的问题,采用N₂保护堆焊并添加氮化铬铁的方式引入合金元素N,同时添加强氮化物形成元素,制备高硼铁基堆焊合金,通过显微组织结构、微区成分、硬度等试验检验,分析合金元素N对高硼铁基堆焊合金组织与性能的影响. 结果表明,氮气保护堆焊高硼铁基合金由初晶Fe₂B、共晶α-Fe+ Fe₂B及粒状复合物M(C,N)组成,N元素的引入促使大量粒状复合物M(C,N)析出,有效细化初晶Fe₂B相,抑制堆焊裂纹的出现. 堆焊合金的宏观硬度也因氮的引入而达到67.8 HRC,但过多的氮会导致Fe₂B生长不完全,硬度略有下降.