International Journal of Minerals, Metallurgy and Materials

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Effects of Na₂SO₄ on iron and nickel reduction in a high-iron and low-nickel laterite ore

Xiao-ping Wang, Ti-chang Sun, Chao Chen, Jue Kou

2018, 25(4): 383-390. doi: 10.1007/s12613-018-1582-y

中文摘要(540) PDF(18) SpringerLink

摘要:
This study investigates the reactions of Na₂SO₄ and its effects on iron and nickel reduction in the roasting of a high-iron and low-nickel laterite ore through gas composition, X-ray diffraction, and scanning electron microscope analyses. Results showed that a reduction reaction of Na₂SO₄ to SO₂ was performed with roasting up to 600℃. However, no clear influence on iron and nickel reductions appeared, because only a small amount of Na₂SO₄ reacted to produce SO₂. Na₂SO₄ reacted completely at 1000℃, mainly producing troilite and nepheline, which remarkably improves selective reduction of nickel. Furthermore, the production of low-melting-point minerals, including troilite and nepheline, accelerated nickel reduction and delayed iron reduction, which is attributed to the concurrent production of magnesium magnetite, whose structure is more stable than the structure of magnetite. Reduction reactions of Na₂SO₄ resulted in weakening of the reduction atmosphere, and the main product of Na₂SO₄ changed and delayed the reduction of iron. Eventually, iron metallization was effectively controlled during laterite ore reduction roasting, leading to iron mainly being found in wustite and high iron-containing olivine.

研究论文

Effect of Cr₂O₃ addition on the oxidation induration mechanism of Hongge vanadium titanomagnetite pellets

Wei Li, Nan Wang, Gui-qin Fu, Man-sheng Chu, Miao-yong Zhu

2018, 25(4): 391-398. doi: 10.1007/s12613-018-1583-x

中文摘要(363) PDF(10) SpringerLink

摘要:
As part of a research project to develop a novel clean smelting process for the comprehensive utilization of Hongge vanadium titanomagnetite (HVTM), in this study, the effect of Cr₂O₃ addition on the oxidation induration mechanism of HVTM pellets (HVTMPs) was investigated in detail. The results showed that the compressive strength of the HVTMPs was greatly weakened by the Cr₂O₃ addition, mainly because of a substantial increase in the porosity of the HVTMPs. The Cr₂O₃ addition marginally affected the phase composition but greatly affected the microstructural changes of the HVTMPs. Increased amounts of Cr₂O₃ resulted in a decrease in the uniform distribution of the hematite grains and in an increase in the Fe-Cr solid solutions (Fe_1.2Cr_0.8O₃ and Fe_0.7Cr_1.3O₃) embedded in the hematite grains. Moreover, the compact hematite was destroyed by forming a dispersed structure and the hematite recrystallization was hindered during the oxidation induration, which adversely affected the compressive strength. On the basis of these results, a schematic was formulated to describe the oxidation induration mechanism with different amounts of added Cr₂O₃. This study provides theoretical and technical foundations for the effective production of HVTMPs and a reference for chromium-bearing minerals.

研究论文

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF₂-CaO-SiO₂-based slags

Sheng-chao Duan, Chuang Li, Han-jie Guo, Jing Guo, Shao-wei Han, Wen-sheng Yang

2018, 25(4): 399-404. doi: 10.1007/s12613-018-1584-9

中文摘要(549) PDF(9) SpringerLink

摘要:
The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO-SiO₂-MgO-FeO-MnO-Al₂O₃-TiO₂-CaF₂ was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step (RCS) for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide (MnO), the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol^-1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the "specific reaction interface" (SRI) value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

研究论文

Study on reduction of MoS₂ powders with activated carbon to produce Mo₂C under vacuum conditions

Guo-hua Zhang, He-qiang Chang, Lu Wang, Kuo-chih Chou

2018, 25(4): 405-412. doi: 10.1007/s12613-018-1585-8

中文摘要(552) PDF(12) SpringerLink

摘要:
A method of preparing Mo₂C via vacuum carbothermic reduction of MoS₂ in the temperature range of 1350-1550℃ was proposed. The effects of MoS₂-to-C molar ratio (α, α=1:1, 1:1.5, and 1:2.5) and reaction temperature (1350 to 1550℃) on the reaction were studied in detail. The phase transition, morphological evolution, and residual sulfur content of the products were analyzed by X-ray diffraction, field-emission scanning electron microscopy, and carbon-sulfur analysis, respectively. The results showed that the complete decomposition of MoS₂ under vacuum is difficult, whereas activated carbon can react with MoS₂ under vacuum to generate Mo₂C. Meanwhile, higher temperatures and the addition of more carbon accelerated the rate of carbothermic reduction reaction and further decreased the residual sulfur content. From the experimental results, the optimum molar ratio α was concluded to be 1:1.5.

研究论文

Effects of Fe₂O₃ on the properties of ceramics from steel slag

Yu Li, Li-hua Zhao, Ya-kun Wang, Da-qiang Cang

2018, 25(4): 413-419. doi: 10.1007/s12613-018-1586-7

中文摘要(592) PDF(16) SpringerLink

摘要:
Ferric oxide is one of the key factors affecting both the microstructure and the properties of CaO-MgO-SiO₂-based ceramics. Research on this effect is significant in the utilization of iron-rich solid wastes in ceramics. Ceramic samples with various Fe₂O₃ contents (0wt%, 5wt%, and 10wt%) were prepared and the corresponding physical properties and microstructure were studied. The results indicated that Fe₂O₃ not only played a fluxing role, but also promoted the formation of crystals. Ceramics with 5wt% of Fe₂O₃ addition attained the best mechanical properties with a flexural strength of 132.9 MPa. Iron ions were dissolved into diopside, consequently causing phase transformation from diopside and protoenstatite to augite, thereby contributing to the enhancement of its properties. An excess amount of Fe₂O₃ addition (10wt% or more) resulted in deteriorated properties due to the generation of an excess volume of liquid and the formation of high-porosity structures within ceramics.

研究论文

Analysis on composition and inclusions of ballpoint pen tip steel

Qian-kun Yang, Ping Shen, Dong Zhang, Yan-xin Wu, Jian-xun Fu

2018, 25(4): 420-428. doi: 10.1007/s12613-018-1587-6

中文摘要(629) PDF(10) SpringerLink

摘要:
Ballpoint pen tip steel, a super free-cutting stainless steel, exhibits excellent corrosion resistance and good machining properties. In this study, inductively coupled plasma spectroscopy, metallographic microscopy, and scanning electron microscopy were used to determine the elemental contents in five ballpoint pen tips and their components, morphologies, and inclusion distributions. The results showed that the steels were all S-Pb-Te super free-cutting ferritic stainless steel. The free-cutting phases in the steels were mainly MnS, Pb, and small amounts of PbTe. MnS inclusions were in the form of chain distributions, and the aspect ratio of each size inclusion in the chain was small. The stress concentration effect could substantially reduce the cutting force when the material was machined. Some of the Pb was distributed evenly in the steel matrix as fine particles (1-2 μm), and the rest of the Pb was distributed at the middle or at both ends of the MnS inclusions. The Pb plays a role in lubrication and melting embrittlement, which substantially increases the cutting performance. PbTe was also usually distributed in the middle and at both ends of the MnS inclusions, and Te could convert the sulfides into spindles, thereby improving the cutting performance of the steel.

研究论文

Aging behavior of a copper-bearing high-strength low-carbon steel

Babak Shahriari, Reza Vafaei, Ehsan Mohammad Sharifi, Khosro Farmanesh

2018, 25(4): 429-438. doi: 10.1007/s12613-018-1588-5

中文摘要(652) PDF(17) SpringerLink

摘要:
The effects of aging temperature and time on the hardness and impact toughness of a copper-bearing high-strength low-carbon steel were investigated. The hardness of the aged samples reached maxima after 1 h and 5 h of aging at 500 and 450℃, respectively; this increase in hardness was followed by a decrease in hardness until a temperature of 700℃, at which secondary hardening was observed. The impact toughness of the aged steel was found to be higher for 5 h of aging. Transmission electron microscopy confirmed the presence of carbide and copper precipitates; also, the secondary hardening could be the result of the transformation of austenite (formed in the aging treatment) to martensite. Differential scanning calorimetry of the steel was performed to better understand the precipitation behavior. The results revealed that the precipitation of the steel exhibited two significant stages of copper precipitate nucleation and coarsening of the precipitates, with corresponding activation energies of 49 and 238 kJ·mol^-1, respectively.

研究论文

Characterization and in-situ formation mechanism of tungsten carbide reinforced Fe-based alloy coating by plasma cladding

Mi-qi Wang, Ze-hua Zhou, Lin-tao Wu, Ying Ding, Ze-hua Wang

2018, 25(4): 439-443. doi: 10.1007/s12613-018-1589-4

中文摘要(575) PDF(11) SpringerLink

摘要:
The precursor carbonization method was first applied to prepare W-C compound powder to perform the in-situ synthesis of the WC phase in a Fe-based alloy coating. The in-situ formation mechanism during the cladding process is discussed in detail. The results reveal that fine and obtuse WC particles were successfully generated and distributed in Fe-based alloy coating via Fe/W-C compound powders. The WC particles were either surrounded by or were semi-enclosed in blocky M₇C₃ carbides. Moreover, net-like structures were confirmed as mixtures of M₂₃C₆ and α-Fe; these structures were transformed from M₇C₃. The coarse herringbone M₃C carbides did not only derive from the decomposition of M₇C₃ but also partly originated from the chemical reaction at the α-Fe/M₂₃C₆ interface. During the cladding process, the phase evolution of the precipitated carbides was WC → M₇C₃ → M₂₃C₆+M₃C.

研究论文

Enhancement of ductility and improvement of abnormal Goss grain growth of magnetostrictive Fe-Ga rolled alloys

Ji-heng Li, Chao Yuan, Xing Mu, Xiao-qian Bao, Xue-xu Gao

2018, 25(4): 444-452. doi: 10.1007/s12613-018-1590-y

中文摘要(480) PDF(13) SpringerLink

摘要:
The influences of initial microstructures on the mechanical properties and the recrystallization texture of magnetostrictive 0.1at% NbC-doped Fe₈₃Ga₁₇ alloys were investigated. The directionally solidified columnar-grained structure substantially enhanced the tensile elongation at intermediate temperatures by suppressing fracture along the transverse boundaries. Compared with tensile elongations of 1.0% at 300℃ and 12.0% at 500℃ of the hot-forged equiaxed-grained alloys, the columnar-grained alloys exhibited substantially increased tensile elongations of 21.6% at 300℃ and 46.6% at 500℃. In the slabs for rolling, the introduction of <001>-oriented columnar grains also promotes the secondary recrystallization of Goss grains in the finally annealed sheets, resulting in an improvement of the saturation magnetostriction. For the columnar-grained specimens, the inhomogeneous microstructure and disadvantage in number and size of Goss grains are improved in the primarily annealed sheets, which is beneficial to the abnormal growth of Goss grains during the final annealing process.

研究论文

Evaluation of precipitation hardening in TiC-reinforced Ti₂AlNb-based alloys

Ya-ran Zhang, Qi Cai, Yong-chang Liu, Zong-qing Ma, Chong Li, Hui-jun Li

2018, 25(4): 453-458. doi: 10.1007/s12613-018-1591-x

中文摘要(444) PDF(12) SpringerLink

摘要:
Ti₂AlNb-based alloys with 0.0wt%, 0.6wt%, and 2.0wt% carbon nanotube (CNT) addition were fabricated from spherical Ti-22Al-25Nb powder by sintering in the B2 single-phase region. Phase identification and microstructural examination were performed to evaluate the effect of carbon addition on the hardness of the alloys. Carbon was either in a soluble state or in carbide form depending on its concentration. The acicular carbides formed around 1050℃ were identified as TiC and facilitated the transformation of α₂+B2 → O. The TiC was located within the acicular O phase. The surrounding O phase was distributed in certain orientations with angles of 65° or 90° O phase particles. The obtained alloy was composed of acicular O, Widmanstatten B2+O, and acicular TiC. As a result of the precipitation of carbides as well as the O phase, the hardness of the alloy with 2.0wt% CNT addition increased to HV 429±9.

研究论文

Sintering behavior and thermal conductivity of nickel-coated graphite flake/copper composites fabricated by spark plasma sintering

Hui Xu, Jian-hao Chen, Shu-bin Ren, Xin-bo He, Xuan-hui Qu

2018, 25(4): 459-471. doi: 10.1007/s12613-018-1592-9

中文摘要(623) PDF(20) SpringerLink

摘要:
Nickel-coated graphite flakes/copper (GN/Cu) composites were fabricated by spark plasma sintering with the surface of graphite flakes (GFs) being modified by Ni-P electroless plating. The effects of the phase transition of the amorphous Ni-P plating and of Ni diffusion into the Cu matrix on the densification behavior, interfacial microstructure, and thermal conductivity (TC) of the GN/Cu composites were systematically investigated. The introduction of Ni-P electroless plating efficiently reduced the densification temperature of uncoated GF/Cu composites from 850 to 650℃ and slightly increased the TC of the X-Y basal plane of the GF/Cu composites with 20vol%-30vol% graphite flakes. However, when the graphite flake content was greater than 30vol%, the TC of the GF/Cu composites decreased with the introduction of Ni-P plating as a result of the combined effect of the improved heat-transfer interface with the transition layer, P generated at the interface, and the diffusion of Ni into the matrix. Given the effect of the Ni content on the TC of the Cu matrix and on the interface thermal resistance, a modified effective medium approximation model was used to predict the TC of the prepared GF/Cu composites.

研究论文

Effect of TiO₂ nanoparticles on hydrogen evolution reaction activity of Ni coatings

Revanna Kullaiah, Liju Elias, Ampar Chitharanjan Hegde

2018, 25(4): 472-479. doi: 10.1007/s12613-018-1593-8

中文摘要(627) PDF(15) SpringerLink

摘要:
The electrocatalytic activity of electrodeposited Ni and Ni-TiO₂ coatings with regard to the alkaline hydrogen evolution reaction (HER) was investigated. The Ni coatings were electrodeposited from an acid chloride bath at different current densities, and their HER activities were examined in a 1.0-mol·L^-1 KOH medium. The variations in the HER activity of the Ni coatings with changes in surface morphology and composition were examined via the electrochemical dissolution and incorporation of nanoparticles. Electrochemical analysis methods were used to monitor the HER activity of the test electrodes; this activity was confirmed via the quantification of gases that evolved during the analysis. The obtained results demonstrated that the Ni-TiO₂ nanocomposite test electrode exhibited maximum activity toward the alkaline HER. The surface appearance, composition, and the phase structure of all developed coatings were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), respectively. The improvement in the electrocatalytic activity of Ni-TiO₂ nanocomposite coating toward HER was attributed to the variation in surface morphology and increased number of active sites.

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2018年第25卷第4期

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2018年第25卷第4期