International Journal of Minerals, Metallurgy and Materials

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Grate-kiln pelletization of Indian hematite fines and its industrial practice

De-qing Zhu, Feng Zhang, Zheng-qi Guo, Jian Pan, Wei Yu

2017, 24(5): 473-485. doi: 10.1007/s12613-017-1428-z

中文摘要(419) PDF(15) SpringerLink

摘要:
Indian hematite fines normally have a high iron grade and minor impurities; they are usually used as sinter fines for feeding into a blast furnace. In this work, the grindability properties of two kinds of Indian hematite fines and the roasting behaviors and induration characteristics of pellets made from these fines were revealed through experiments involving dry ball milling and small-scale and pilot-scale tests. In addition, the microstructures of the particles of ground India hematite fines and fired pellets were investigated using optical microscopy. On the basis of the results, a grate-kiln production line with an annual output of 1.2 Mt of oxidized pellets was established in India. This pellet plant operates stably and reliably, further confirming that preparing high-quality pellets with Indian hematite fines pretreated by dry ball milling is an industrially feasible process.

研究论文

Kinetics of magnetite oxidation under non-isothermal conditions

Aref Sardari, Eskandar Keshavarz Alamdari, Mohammad Noaparast, Sied Ziaedin Shafaei

2017, 24(5): 486-492. doi: 10.1007/s12613-017-1429-y

中文摘要(473) PDF(42) SpringerLink

摘要:
Oxidation of magnetite concentrates, which occurs during the pellet induration process, must be deeply understood to enable the appropriate design of induration machines. In the present paper, the kinetics of the magnetite oxidation reaction was studied. Primary samples were obtained from the Gol-e-Gohar iron ore deposit. Magnetic separation and flotation decreased the sulfur content in the samples to be approximately 0.1wt%. Thermogravimetric analysis was used to measure mass changes during the oxidation of magnetite and, consequently, the conversion values. The aim of this study was to use isoconversional methods to calculate the kinetic parameters. The Coats-Redfern method was also used to obtain the activation energy. Thermogravimetric analyses were run at three different heating rates. The Coats-Redfern results were too ambiguous for a meaningful interpretation. In the case of the isoconversional method, however, the mean activation energy and pre-exponential factor of the oxidation reaction were obtained as 67.55 kJ and 15.32×10⁸ min^-1, respectively. Such a large activation energy implies that temperature strongly affects the reaction rate. The oxidation reaction exhibits a true multi-step nature that is predominantly controlled by chemical reaction and diffusion mechanisms.

研究论文Open Access

Reduction behavior and kinetics of vanadium-titanium sinters under high potential oxygen enriched pulverized coal injection

Jin-fang Ma, Guang-wei Wang, Jian-liang Zhang, Xin-yu Li, Zheng-jian Liu, Ke-xin Jiao, Jian Guo

2017, 24(5): 493-503. doi: 10.1007/s12613-017-1430-5

中文摘要(479) PDF(11) SpringerLink

摘要:
In this work, the reduction behavior of vanadium-titanium sinters was studied under five different sets of conditions of pulverized coal injection with oxygen enrichment. The modified random pore model was established to analyze the reduction kinetics. The results show that the reduction rate of sinters was accelerated by an increase of CO and H₂ contents. Meanwhile, with the increase in CO and H₂ contents, the increasing range of the medium reduction index (MRE) of sinters decreased. The increasing oxygen enrichment ratio played a diminishing role in improving the reduction behavior of the sinters. The reducing process kinetic parameters were solved using the modified random role model. The results indicated that, with increasing oxygen enrichment, the contents of CO and H₂ in the reducing gas increased. The reduction activation energy of the sinters decreased to between 20.4 and 23.2 kJ/mol.

研究论文

A novel process for the recovery of iron, titanium, and vanadium from vanadium-bearing titanomagnetite:sodium modification-direct reduction coupled process

Yi-min Zhang, Ling-yun Yi, Li-na Wang, De-sheng Chen, Wei-jing Wang, Ya-hui Liu, Hong-xin Zhao, Tao Qi

2017, 24(5): 504-511. doi: 10.1007/s12613-017-1431-4

中文摘要(715) PDF(46) SpringerLink

摘要:
A sodium modification-direct reduction coupled process was proposed for the simultaneous extraction of V and Fe from vanadium-bearing titanomagnetite. The sodium oxidation of vanadium oxides to water-soluble sodium vanadate and the transformation of iron oxides to metallic iron were accomplished in a single-step high-temperature process. The increase in roasting temperature favors the reduction of iron oxides but disfavors the oxidation of vanadium oxides. The recoveries of vanadium, iron, and titanium reached 84.52%, 89.37%, and 95.59%, respectively. Moreover, the acid decomposition efficiency of titanium slag reached 96.45%. Compared with traditional processes, the novel process provides several advantages, including a shorter flow, a lower energy consumption, and a higher utilization efficiency of vanadium-bearing titanomagnetite resources.

研究论文Open Access

Two-stage reduction for the preparation of ferronickel alloy from nickel laterite ore with low Co and high MgO contents

Yong-qiang Chen, Hong-liang Zhao, Cheng-yan Wang

2017, 24(5): 512-522. doi: 10.1007/s12613-017-1432-3

中文摘要(384) PDF(17) SpringerLink

摘要:
The preparation of ferronickel alloy from the nickel laterite ore with low Co and high MgO contents was studied by using a pre-reduction-smelting method. The effects of reduction time, calcination temperature, quantity of reductant and calcium oxide (CaO), and pellet diameter on the reduction ratio of Fe and on the pellet strength were investigated. The results show that, for a roasting temperature >800℃, a roasting time >30 min, 1.5wt% added anthracite coal, 5wt% added CaO, and a pellet size of~10 mm, the reduction ratio of Fe exceeds 70% and the compressive strength of the pellets exceeds 10 kg per pellet. Reduction smelting experiments were performed by varying the smelting time, temperature, quantity of reductant and CaO, and reduction ratio of Fe in the pellets. Optimal conditions for the reduction smelting process are as follows:smelting time, 30-45 min; smelting temperature, 1550℃; quantity of reductant, 4wt%-5wt%; and quantity of CaO, 5wt%; leading to an Fe reduction ratio of 75% in the pellets. In addition, the mineral composition of the raw ore and that during the reduction process were investigated by process mineralogy.

研究论文

Fine structure and phase composition of Fe-14Mn-1.2C steel:influence of a modified mixture based on refractory metals

Anna Zykova, Natalya Popova, Mark Kalashnikov, Irina Kurzina

2017, 24(5): 523-529. doi: 10.1007/s12613-017-1433-2

中文摘要(514) PDF(11) SpringerLink

摘要:
The effect of TiO₂, ZrO₂ and Na₃AlF₆ ultrafine powders on the fine structure and the phase composition of Fe-14Mn-1.2C steel was investigated. The introduction of the ultrafine powders into the melt influenced the grain size, the quantity, and the character of distribution of nonmetallic inclusions in the railroad frogs. The microstructure of castings was improved significantly because of the refinement of the grain structure and an increase of the grain-boundary area. After the modifying mixture was introduced into the melt, either the microtwins of one or two intersecting systems or the precipitations of ε-martensite of different types, or simultaneously the microtwins and wafers of ε-martensite, were present in each grain.

研究论文Open Access

Reverse-transformation austenite structure control with micro/nanometer size

Hui-bin Wu, Gang Niu, Feng-juan Wu, Di Tang

2017, 24(5): 530-537. doi: 10.1007/s12613-017-1434-1

中文摘要(431) PDF(9) SpringerLink

摘要:
To control the reverse-transformation austenite structure through manipulation of the micro/nanometer grain structure, the influences of cold deformation and annealing parameters on the microstructure evolution and mechanical properties of 316L austenitic stainless steel were investigated. The samples were first cold-rolled, and then samples deformed to different extents were annealed at different temperatures. The microstructure evolutions were analyzed by optical microscopy, scanning electron microscopy (SEM), magnetic measurements, and X-ray diffraction (XRD); the mechanical properties are also determined by tensile tests. The results showed that the fraction of stain-induced martensite was approximately 72% in the 90% cold-rolled steel. The micro/nanometric microstructure was obtained after reversion annealing at 820-870℃ for 60 s. Nearly 100% reversed austenite was obtained in samples annealed at 850℃, where grains with a diameter ≤ 500 nm accounted for 30% and those with a diameter >0.5 μm accounted for 70%. The micro/nanometer-grain steel exhibited not only a high strength level (approximately 959 MPa) but also a desirable elongation of approximately 45%.

研究论文

Microstructures and mechanical properties of dissimilar Nd:YAG laser weldments of AISI4340 and AISI316L steels

A. R. Sufizadeh, S. A. A. Akbari Mousavi

2017, 24(5): 538-549. doi: 10.1007/s12613-017-1435-0

中文摘要(532) PDF(14) SpringerLink

摘要:
This paper presents studies on the microstructure and mechanical properties of AISI 316L stainless steel and AISI 4340 low-alloy steel joints formed by the Nd:YAG laser welding process. The weld microstructures and heat affected zones (HAZs) were investigated. Austenitic microstructures were observed in all of the samples. The sizes of the HAZs changed when the heat input was varied, and the 316L sides exhibited a larger HAZ. The cooling rates were calculated by measuring the solidification dendrite arm spacing. It is shown that high cooling rates lead to an austenitic microstructure. Tensile tests were carried out, and the results revealed the tensile properties of both the base metals and the weldments. The hardness test results agreed well with the tensile test results.

研究论文

Effect of coaxial laser cladding parameters on bead formation

A. I. Noskov, A. Kh. Gilmutdinov, R. M. Yanbaev

2017, 24(5): 550-556. doi: 10.1007/s12613-017-1436-z

中文摘要(423) PDF(10) SpringerLink

摘要:
We investigated the shape and morphology of nickel-based powder particles (Sulzer Metco) and coatings produced by laser gas-powder deposition onto steel substrates. Laser deposition was performed using an LC-10 IPG-Photonics laser complex equipped with a 10-kW fiber laser. The shape and microstructure of the samples were studied using optical and electronic microscopy and X-ray diffraction analysis. The results showed that the deposition speed and laser power significantly influenced the shape and size of the beads. The depth of diffusion of nickel into the steel substrate after deposition was less than 20 μm; the microstructure of the resulting coating was fcc Fe₃Ni. As a result, detailed information about the form and shape of the filler powder, modes of its deposition, and the resulting coating structure was obtained; this information is important for the production of high-quality products by additive technologies.

研究论文

Microstructure and properties of an Al-Ti-Cu-Si brazing alloy for SiC-metal joining

Chun-duo Dai, Rui-na Ma, Wei Wang, Xiao-ming Cao, Yan Yu

2017, 24(5): 557-565. doi: 10.1007/s12613-017-1437-y

中文摘要(370) PDF(12) SpringerLink

摘要:
An Al-Ti-Cu-Si solid-liquid dual-phase alloy that exhibits good wettability and appropriate interfacial reaction with SiC at 500-600℃ was designed for SiC-metal joining. The microstructure, phases, differential thermal curves, and high-temperature wetting behavior of the alloy were analyzed using scanning electron microscopy, X-ray diffraction analysis, differential scanning calorimetry, and the sessile drop method. The experimental results show that the 76.5Al-8.5Ti-5Cu-10Si alloy is mainly composed of Al-Al₂Cu and Al-Si hypoeutectic low-melting-point microstructures (493-586℃) and the high-melting-point intermetallic compound AlTiSi (840℃). The contact angle, determined by high-temperature wetting experiments, is approximately 54°. Furthermore, the wetting interface is smooth and contains no obvious defects. Metallurgical bonding at the interface is attributable to the reaction between Al and Si in the alloy and ceramic, respectively. The formation of the brittle Al₄C₃ phase at the interface is suppressed by the addition of 10wt% Si to the alloy.

研究论文

Improving the corrosion properties of magnesium AZ31 alloy GTA weld metal using microarc oxidation process

M. Siva Prasad, M. Ashfaq, N. Kishore Babu, A. Sreekanth, K. Sivaprasad, V. Muthupandi

2017, 24(5): 566-573. doi: 10.1007/s12613-017-1438-x

中文摘要(429) PDF(10) SpringerLink

摘要:
In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

研究论文

Topography, structure, and formation kinetic mechanism of carbon deposited onto nickel in the temperature range from 400 to 850℃

Zhi-yuan Chen, Liu-zhen Bian, Li-jun Wang, Zi-you Yu, Hai-lei Zhao, Fu-shen Li, Kuo-chih Chou

2017, 24(5): 574-583. doi: 10.1007/s12613-017-1439-9

中文摘要(646) PDF(15) SpringerLink

摘要:
The carbon deposition behavior on nickel particles was observed within the temperature range from 400 to 800℃ in a pure methane atmosphere. The topography, properties, and molecular structure of the deposited carbon were investigated using field-emission scanning electron microscopy (FESEM), temperature-programmed oxidation (TPO) technology, X-ray diffraction (XRD), and Raman spectroscopy. The deposited carbon is present in the form of a film at 400-450℃, as fibers at 500-600℃, and as particles at 650-800℃. In addition, the structure of the deposited carbon becomes more ordered at higher temperatures because both the TPO peak temperature of deposited carbon and the Raman shift of the G band increase with the increase in experimental temperature, whereas the intensity ratio between the D bands and the G band decreases. An interesting observation is that the carbon deposition rate is suppressed in the medium-temperature range (M-T range) and the corresponding kinetic mechanism changes. Correspondingly, the FWHM of the G and D1 bands in the Raman spectrum reaches a maximum and the intensities of the D2, D3, and D4 bands decrease to low limits in the M-T range. These results indicate that carbon structure parameters exhibit two different tendencies with respect to varying temperature. Both of the two group parameters change dramatically as a peak function with increasing reaction temperature within the M-T range.

研究论文

Mechanical properties and friction behaviors of CNT/AlSi₁₀Mg composites produced by spark plasma sintering

Lin-zhi Wang, Ying Liu, Jiao-jiao Wu, Xi Zhang

2017, 24(5): 584-593. doi: 10.1007/s12613-017-1440-3

中文摘要(515) PDF(11) SpringerLink

摘要:
The mechanical properties and friction behaviors of CNT/AlSi₁₀Mg composites produced by spark plasma sintering (SPS) were investigated. The results showed that the densities of the sintered composites gradually increased with increasing sintering temperature and that the highest microhardness and compressive strength were achieved in the specimen sintered at 450℃. CNTs dispersed uniformly in the AlSi₁₀Mg matrix when the addition of CNTs was less than 1.5wt%. However, when the addition of CNTs exceeded 1.5wt%, the aggregation of CNTs was clearly observed. Moreover, the mechanical properties (including the densities, compressive strength, and microhardness) of the composites changed with CNT content and reached a maximum value when the CNT content was 1.5wt%. Meanwhile, the minimum average friction coefficient and wear rate of the CNT/AlSi₁₀Mg composites were obtained with 1.0wt% CNTs.

研究论文

Synthesis and analysis of new humidity-controlling composite materials

Jian-li Shang, Zhi-fang Zong, Hao Zhang

2017, 24(5): 594-602. doi: 10.1007/s12613-017-1441-2

中文摘要(471) PDF(14) SpringerLink

摘要:
Gypsum is a traditional building material. To improve the humidity-controlling properties of gypsum, we prepared a new type of humidity-controlling composite using the sol-gel method. Methods to determine the maximum equilibrium moisture content and speed of adsorption/desorption were subsequently applied to analyze the performance of the samples. The appearance and structural properties of the samples were characterized by scanning electronic microscopy (SEM). The experimental results show that the humidity-controlling gel with added LiCl exhibits high moisture storage and that the equilibrium maximum moisture content is 5.652 g/g at a 75.29% relative humidity (RH). A mass ratio of LiCl/sol=0.15 is demonstrated to be appropriate for the preparation of the new humidity-controlling composites. A coarse network with tiny pores is observed on the surface of the new humidity-controlling composites, and this pore network provides sufficient space for moisture adsorption.

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2017年第24卷第5期