International Journal of Minerals, Metallurgy and Materials

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Preparation of manganese sulfate from low-grade manganese carbonate ores by sulfuric acid leaching

Qing-quan Lin, Guo-hua Gu, Hui Wang, Ren-feng Zhu, You-cai Liu, Jian-gang Fu

2016, 23(5): 491-500. doi: 10.1007/s12613-016-1260-x

中文摘要(566) PDF(71) SpringerLink

摘要:
In this study, a method for preparing pure manganese sulfate from low-grade ores with a granule mean size of 0.47 mm by direct acid leaching was developed. The effects of the types of leaching agents, sulfuric acid concentration, reaction temperature, and agitation rate on the leaching efficiency of manganese were investigated. We observed that sulfuric acid used as a leaching agent provides a similar leaching efficiency of manganese and superior selectivity against calcium compared to hydrochloric acid. The optimal leaching conditions in sulfuric acid media were determined; under the optimal conditions, the leaching efficiencies of Mn and Ca were 92.42% and 9.61%, respectively. Moreover, the kinetics of manganese leaching indicated that the leaching follows the diffusion-controlled model with an apparent activation energy of 12.28 kJ·mol^-1. The purification conditions of the leaching solution were also discussed. The results show that manganese dioxide is a suitable oxidant of ferrous ions and sodium dimethyldithiocarbamate is an effective precipitant of heavy metals. Finally, through chemical analysis and X-ray diffraction analysis, the obtained product was determined to contain 98% of MnSO₄·H₂O.

Novel blast furnace operation process involving charging with low-titanium vanadium–titanium magnetite carbon composite hot briquette

Wei Zhao, Man-sheng Chu, Hong-tao Wang, Zheng-gen Liu, Ya-ting Tang

2016, 23(5): 501-510. doi: 10.1007/s12613-016-1261-9

中文摘要(226) PDF(10) SpringerLink

摘要:
An innovative process of blast furnace (BF) operation involving charging with low-titanium vanadium–titanium magnetite carbon composite hot briquette (LVTM-CCB) was proposed for utilizing LVTM and conserving energy. In this study, the effect of LVTM-CCB charging ratio on the softening, melting, and dripping behaviors of the mixed burden was explored systemically, and the migration of valuable elements V and Cr was extensively investigated. The results show that with increasing LVTM-CCB charging ratio, the softening interval T₄₀-T₄ increases from 146.1℃ to 266.1℃, and the melting interval T_D-T_S first decreases from 137.2℃ to 129.5℃ and then increases from 129.5℃ to 133.2℃. Moreover, the cohesive zone becomes narrower and then wider, and its location shifts slightly downward. In addition, the recovery ratios of V and Cr in dripped iron first increase and then decrease, reaching maximum values of 14.552% and 28.163%, respectively, when the charging ratio is 25%. A proper LVTM-CCB charging ratio would improve the softening–melting behavior of the mixed burden; however, Ti(C,N) would be generated rapidly in slag when the charging ratio exceeds 25%, which is not favorable for BF operation. When considering the comprehensive softening–melting behavior of the mixed burden and the recovery ratios of V and Cr, the recommended LVTM-CCB charging ratio is 20%.

Simulation study on factors influencing the entrainment behavior of liquid steel as bubbles pass through the steel/slag interface

Xiang Li, Yan-ping Bao, Min Wang, Lu Lin

2016, 23(5): 511-519. doi: 10.1007/s12613-016-1262-8

中文摘要(178) PDF(13) SpringerLink

摘要:
In this study, a water/silicone oil interface was used to simulate the steel/slag interface in a converter. A high-speed camera was used to record the entrainment process of droplets when air bubbles were passed through the water/silicone oil interface. Motion parameters of the bubbles and droplets were obtained using particle kinematic analysis software, and the entrainment rate of the droplets was calculated. It was found that the entrainment rate decreased from 29.5% to 0 when the viscosity of the silicone oil was increased from 60 mPa·s to 820 mPa·s in the case of bubbles with a 5 mm equivalent diameter passing through the water/silicone oil interface. The results indicate that increasing the viscosity of the silicone oil is conducive to reducing the entrainment rate. The entrainment rate increased from 0 to 136.3% in the case of silicone oil with a viscosity of 60 mPa·s when the equivalent diameter of the bubbles was increased from 3 mm to 7 mm. We therefore conclude that small bubbles are also conductive to reducing the entrainment rate. The force analysis results for the water column indicate that the entrainment rate of droplets is affected by the velocity of the bubble passing through the water/silicone oil interface and that the entrainment rate decreases with the bubble velocity.

Phosphate enrichment mechanism in CaO–SiO₂–FeO–Fe₂O₃–P₂O₅ steelmaking slags with lower binary basicity

Jin-yan Li, Mei Zhang, Min Guo, Xue-min Yang

2016, 23(5): 520-533. doi: 10.1007/s12613-016-1263-7

中文摘要(227) PDF(10) SpringerLink

摘要:
The addition of silica to steelmaking slags to decrease the binary basicity can promote phosphate enrichment in quenched slag samples. In this study, we experimentally investigated phosphate enrichment behavior in CaO–SiO₂–FeO–Fe₂O₃–P₂O₅ slags with a P₂O₅ content of 5.00% and the binary basicity B ranging from 1.0 to 2.0, where the (%Fe_tO)/(%CaO) mass percentage ratio was maintained at 0.955. The experimental results are explained by the defined enrichment degree R_C₂S-C₃P of solid solution 2CaO·SiO₂–3CaO·P₂O₅ (C₂S–C₃P), where R_C₂S-C₃P is a component of the developed ion and molecule coexistence theory (IMCT)–N_i model for calculating the mass action concentrations N_i of structural units in the slags on the basis of the IMCT. The asymmetrically inverse V-shaped relation between phosphate enrichment and binary basicity B was observed to be correlated in the slags under applied two-stage cooling conditions. The maximum content of P₂O₅ in the C₂S–C₃P solid solution reached approximately 30.0% when the binary basicity B was controlled at 1.3.

Analysis of cracking phenomena in continuous casting of 1Cr13 stainless steel billets with final electromagnetic stirring

Yu Xu, Rong-jun Xu, Zheng-jie Fan, Cheng-bin Li, An-yuan Deng, En-gang Wang

2016, 23(5): 534-541. doi: 10.1007/s12613-016-1264-6

中文摘要(324) PDF(17) SpringerLink

摘要:
Solidification cracking that occurs during continuous casting of 1Cr13 stainless steel was investigated with and without final electromagnetic stirring (F-EMS). The results show that cracks initiates and propagates along the grain boundaries where the elements of carbon and sulfur are enriched. The final stirrer should be appropriately placed at a location that is 7.5 m away from the meniscus, and the appropriate thickness of the liquid core in the stirring zone is 50 mm. As a stirring current of 250 A is imposed, it can promote columnar-equiaxed transition, decrease the secondary dendrite arm spacing, and reduce the segregation of both carbon and sulfur. F-EMS can effectively decrease the amount of cracks in 1Cr13 stainless steel.

Effects of process parameters on nonaqueous gelcasting for copper powder

Karima Bekouche, Zhao-li Wang, Cheng-Chang Jia, Bo-wen Liu, Yi Tang

2016, 23(5): 542-547. doi: 10.1007/s12613-016-1265-5

中文摘要(138) PDF(9) SpringerLink

摘要:
An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technology is presented in this study. The effects of various gelcasting processing parameters such as monomer content, monomer/crosslinker ratio, initiator content, dispersant dosage, and temperature on the flexural strength of dried green bodies and the relative density of sintered bodies were studied to obtain better microstructures and properties. The appropriate process parameters obtained for copper gelcasting are as follows: monomer content, 20vol%–30vol% (based on the total volume of reagents); monomer/crosslinker ratio, 10:1 to 20:1; initiator content, 3vol%–4vol% (based on the volume of the monomer); dispersant dosage, 1.5wt%–2.5wt% (based on the mass of the copper powder); and reaction temperature, 65–75℃.

Microstructural evolution and castability prediction in newly designed modern third-generation nickel-based superalloys

Homam Naffakh-Moosavy

2016, 23(5): 548-562. doi: 10.1007/s12613-016-1266-4

中文摘要(130) PDF(8) SpringerLink

摘要:
The present research aims to establish a quantitative relation between microstructure and chemical composition (i.e., Ti, Al, and Nb) of newly designed nickel-based superalloys. This research attempts to identify an optimum microstructure at which the minimum quantities of γ/γ' and γ/γ″ compounds are achieved and the best castability is predicted. The results demonstrate that the highest quantity of intermetallic eutectics (i.e., 41.5wt%) is formed at 9.8wt% (Ti + Al). A significant quantity of intermetallics formed in superalloy 1 (with a composition of γ-9.8wt% (Ti + Al)), which can deteriorate its castability. The type and morphology of the eutectics changed and the amount considerably decreased with decreasing Ti + Al content in superalloy 2 (with a composition of γ-7.6wt% (Ti + Al), 1.5wt% Nb). Thus, it is predicted that the castability would improve for superalloy 2. The same trend was observed for superalloy 4 (with a composition of γ-3.7wt% (Ti + Al), 4.4wt% Nb). This means that the amount of Laves increases with increasing Nb (to 4.4wt%) and decreasing Ti + Al (to 3.7wt%) in superalloy 4. The best castability was predicted for superalloy 3 (with a composition of γ-5.7wt% (Ti + Al), 2.8wt% Nb).

Peculiarities of the rheological behavior and structure formation of aluminum under deformation at near-solidus temperatures

A. S. Smirnov, A. V. Konovalov, G. A. Belozerov, V. P. Shveikin, E. O. Smirnova

2016, 23(5): 563-571. doi: 10.1007/s12613-016-1267-3

中文摘要(159) PDF(8) SpringerLink

摘要:
This paper deals with a peculiar rheological behavior of aluminum at near-solidus temperatures. It has been experimentally established that there is an inverse strain rate dependence of strain resistance at temperatures ranging between 560 and 640°С and strain rates ranging from 0.06 to 1.2 s^-1. Electron backscatter diffraction analysis has shown that at temperatures ranging between 540 and 640°С and strain rates ranging from 0.06 to 0.1 s^-1, the main process of softening is dynamic polygonization, resulting in in situ recrystallization. At higher strain rates, ranging between 0.8 and 1.2 s^-1, and temperatures ranging between 560 and 640°С, the recovery is dynamic. This unusual behavior of the mechanism of softening and the presence of the inverse strain rate dependence of strain resistance can be explained by blocking the motion of free dislocations by foreign atoms, which occurs at strain rates ranging between 0.06 and 0.1 s^-1. This process results in dislocation pile-up, thereby causing in situ recrystallization. At strain rates exceeding 0.16 s^-1, there is no intensive blocking of dislocations, leading to a direct strain rate dependence of strain resistance.

Refinement of primary Si grains in Al–20%Si alloy slurry through serpentine channel pouring process

Zhi-kai Zheng, Wei-min Mao, Zhi-yong Liu, Dong Wang, Rui Yue

2016, 23(5): 572-580. doi: 10.1007/s12613-016-1268-2

中文摘要(178) PDF(7) SpringerLink

摘要:
In this study, a serpentine channel pouring process was used to prepare the semi-solid Al–20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid Al–20%Si alloy slurry were investigated. The results showed that the pouring temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring temperature exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid Al–20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid Al–20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the refinement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.

Recrystallization behavior of Ti40 burn-resistant titanium alloy during hot working process

Yun-jin Lai, She-wei Xin, Ping-xiang Zhang, Yong-qing Zhao, Fan-jiao Ma, Xiang-hong Liu, Yong Feng

2016, 23(5): 581-587. doi: 10.1007/s12613-016-1269-1

中文摘要(221) PDF(8) SpringerLink

摘要:
The recrystallization behavior of deformed Ti40 alloy during a heat-treatment process was studied using electron backscatter diffraction and optical microscopy. The results show that the microstructural evolution of Ti40 alloy is controlled by the growth behavior of grain-boundary small grains during the heating process. These small grains at the grain boundaries mostly originate during the forging process because of the alloy’s inhomogeneous deformation. During forging, the deformation first occurs in the grain-boundary region. New small recrystallized grains are separated from the parent grains when the orientation between deformation zones and parent grains exceeds a certain threshold. During the heating process, the growth of these small recrystallized grains results in a uniform grain size and a decrease in the average grain size. The special recrystallization behavior of Ti40 alloy is mainly a consequence of the alloy’s high β-stabilized elemental content and high solution strength of the β-grains, which partially explains the poor hot working ability of Ti–V–Cr-type burn-resistant titanium alloys. Notably, this study on Ti40 burn-resistant titanium alloy yields important information related to the optimization of the microstructures and mechanical properties.

Characterization of mechanothermally processed nanostructured ZnO

Saeed Karimi, Abolghasem Ataie

2016, 23(5): 588-594. doi: 10.1007/s12613-016-1270-8

中文摘要(139) PDF(7) SpringerLink

摘要:
In this paper, the Taguchi method with an L₉(3⁴) orthogonal array was used as experimental design to determine the optimum conditions for preparing ZnO nanoparticles via a mechanothermal route. ZnSO₄·H₂O and Na₂CO₃ were used as starting materials. The effects of milling time, Na₂CO₃/ZnSO₄·H₂O molar ratio, and ball-to-powder mass ratio (BPR) on the bandgap (E_g) of ZnO nanoparticles were investigated. The ranges of the investigated experimental conditions were 5–15 h for the milling time (t), 1.0–1.2 for the Na₂CO₃/ZnSO₄·H₂O molar ratio (M), and 10–30 for BPR. The milling time and BPR exhibited significant effects; an increase in milling time reduced the bandgap. The optimum conditions from this study were t₃ = 15 h, M₁ = 1, and BPR₂ = 20. Only two significant factors (t₃, 15 h; BPR₂, 20) were used to estimate the performance at the optimum conditions. The calculated bandgap was 3.12 eV, in reasonable agreement with the experimental results obtained under the optimized conditions.

Influence of aluminium nitride as a foaming agent on the preparation of foam glass-ceramics from high-titanium blast furnace slag

Huan Shi, Ke-qin Feng, Hai-bo Wang, Chang-hong Chen, Hong-ling Zhou

2016, 23(5): 595-600. doi: 10.1007/s12613-016-1271-7

中文摘要(282) PDF(28) SpringerLink

摘要:
To effectively reuse high-titanium blast furnace slag (TS), foam glass-ceramics were successfully prepared by powder sintering at 1000℃. TS and waste glass were used as the main raw materials, aluminium nitride (AlN) as the foaming agent, and borax as the fluxing agent. The influence of the amount of AlN added (1wt%–5wt%) on the crystalline phases, microstructure, and properties of the produced foam glass-ceramics was studied. The results showed that the main crystal phases were perovskite, diopside, and augite. With increasing AlN content, a transformation from diopside to augite occurred and the crystallinity of the pyroxene phases slightly decreased. Initially, the average pore size and porosity of the foam glass-ceramics increased and subsequently decreased; similarly, their bulk density and compressive strength decreased and subsequently increased. The optimal properties were obtained when the foam glass-ceramics were prepared by adding 4wt% AlN.

Effect of graphite powder as a forming filler on the mechanical properties of SiCp/Al composites by pressure infiltration

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

2016, 23(5): 601-607. doi: 10.1007/s12613-016-1272-6

中文摘要(280) PDF(27) SpringerLink

摘要:
(38vol% SiCp + 2vol% Al₂O_3f)/2024 Al composites were fabricated by pressure infiltration. Graphite powder was introduced as a forming filler in preform preparation, and the effects of the powder size on the microstructures and mechanical properties of the final composites were investigated. The results showed that the composite with 15 μm graphite powder as a forming filler had the maximum tensile strength of 506 MPa, maximum yield strength of 489 MPa, and maximum elongation of 1.2%, which decreased to 490 MPa, 430 MPa, and 0.4%, respectively, on increasing the graphite powder size from 15 to 60 μm. The composite with 60 μm graphite powder showed the highest elastic modulus, and the value decreased from 129 to 113 GPa on decreasing the graphite powder size from 60 to 15 μm. The differences between these properties are related to the different microstructures of the corresponding composites, which determine their failure modes.

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2016年第23卷第5期