International Journal of Minerals, Metallurgy and Materials

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Mechanical properties and supporting effect of CRLD bolts under static pull test conditions

Xiao-ming Sun, Yong Zhang, Dong Wang, Jun Yang, Hui-chen Xu, Man-chao He

2017, 24(1): 1-9. doi: 10.1007/s12613-017-1372-y

中文摘要(667) PDF(14) SpringerLink

摘要:
A device for supporting soft rock masses combined with a constant resistance structure characterized by constant resistance and large deformation at the end of a steel bar, known as the constant resistance and large deformation (CRLD) bolt, has recently been developed to counteract soft rock swelling that often occurs during deep mining. In order to further study the mechanical properties of the CRLD bolt, we investigated its mechanical properties by comparison with the conventional strength bolt (rebar) using static pull tests on many aspects, including supporting capacity, elongation, radial deformation, and energy absorption. The tests verified that the mechanical defects of the rebar, which include the decrease of bolt diameter, reduction of supporting capacity, and emergence and evolution of fracture until failure during the whole pull process, were caused by the Poisson's ratio effect. Due to the special structure set on the CRLD bolt, the bolt presents a seemingly unusual phenomenon of the negative Poisson's ratio effect, i.e., the diameter of the constant resistance structure increases while under-pulling. It is the very effect that ensures the extraordinary mechanical properties, including high resistance, large elongation, and strong energy absorption. According to the comparison and analysis of numerical simulation and field test, we can conclude that the CRLD bolt works better than the rebar bolt.

研究论文

Gas-based reduction of vanadium titano-magnetite concentrate:behavior and mechanisms

Yu-lei Sui, Yu-feng Guo, Tao Jiang, Xiao-lin Xie, Shuai Wang, Fu-qiang Zheng

2017, 24(1): 10-17. doi: 10.1007/s12613-017-1373-x

中文摘要(643) PDF(24) SpringerLink

摘要:
The reduction of vanadium titano-magnetite pellets by H₂-CO at temperatures from 850 to 1050℃ was investigated in this paper. The influences of pre-oxidation treatment, reduction temperature, and V_H₂/(V_H₂ + V_CO) on the metallization degree were studied. The results showed that pre-oxidation played a substantial role in the reduction of vanadium titano-magnetite pellets. During the reduction process, the metallization degree increased with increasing temperature and increasing V_H₂/(V_H₂ + V_CO). The phase transformation of pre-oxidized vanadium titano-magnetite pellets during the reduction process under an H₂ atmosphere and a CO atmosphere was discussed, and the reduced samples were analyzed by scanning electron microscopy (SEM) in conjunction with back scatter electron (BSE) imaging. The results show that the difference in thermodynamic reducing ability between H₂ and CO is not the only factor that leads to differences in the reduction results obtained using different atmospheres. Some of Fe_3-xTi_xO₄ cannot be reduced under a CO atmosphere because of the densification of particles' structure and because of the enrichment of Mg in unreacted cores. By contrast, a loose structure of particles was obtained when the pellets were reduced under an H₂ atmosphere and this structure decreased the resistance to gas diffusion. Moreover, the phenomenon of Mg enrichment in unreacted cores disappeared during H₂ reduction. Both the lower resistance to gas diffusion and the lack of Mg enrichment facilitated the reduction of vanadium titano-magnetite.

研究论文

Effect of TiO₂ on the viscosity and structure of low-fluoride slag used for electroslag remelting of Ti-containing steels

Cheng-bin Shi, Ding-li Zheng, Seung-ho Shin, Jing Li, Jung-wook Cho

2017, 24(1): 18-24. doi: 10.1007/s12613-017-1374-9

中文摘要(653) PDF(22) SpringerLink

摘要:
The viscosity of CaF₂-CaO-Al₂O₃-MgO-(TiO₂) slag was measured using a rotating crucible viscometer. Raman spectroscopy analysis was performed to correlate the viscosity to slag structure. The viscosity of the slag was found to decrease with increasing TiO₂ content in the slag from 0 to 9.73wt%. The activation energy decreased from 95.16 kJ/mol to 79.40 kJ/mol with increasing TiO₂ content in the slag. The introduction of TiO₂ into the slag played a destructive role in Al-O-Al structural units and Q⁴ units by forming simpler structural units of Q² and Ti₂O₆^4- chain. The amount of Al-O-Al significantly decreased with increasing TiO₂ content. The relative fraction of Q⁴ units in the[AlO₄]^5--tetrahedral units shows a decreasing trend, whereas the relative fraction of Q² units and Ti₂O₆^4- chain increases with increasing TiO₂ content accordingly. Consequently, the polymerization degree of the slag decreases with increasing TiO₂ content. The variation in slag structure is consistent with the change in measured viscosity.

研究论文

Activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag and their application to the recycling of Ni-Co-Fe-based end-of-life superalloys via remelting

Xin Lu, Takahiro Miki, Tetsuya Nagasaka

2017, 24(1): 25-36. doi: 10.1007/s12613-017-1375-8

中文摘要(760) PDF(18) SpringerLink

摘要:
To design optimal pyrometallurgical processes for nickel and cobalt recycling, and more particularly for the end-of-life process of Ni-Co-Fe-based end-of-life (EoL) superalloys, knowledge of their activity coefficients in slags is essential. In this study, the activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag, a candidate slag used for the EoL superalloy remelting process, were measured using gas/slag/metal equilibrium experiments. These activity coefficients were then used to consider the recycling efficiency of nickel and cobalt by remelting EoL superalloys using CaO-Al₂O₃-SiO₂ slag. The activity coefficients of NiO and CoO in CaO-Al₂O₃-SiO₂ slag both show a positive deviation from Raoult's law, with values that vary from 1 to 5 depending on the change in basicity. The activity coefficients of NiO and CoO peak in the slag with a composition near B=(%CaO)/(%SiO₂)=1, where B is the basicity. We observed that controlling the slag composition at approximately B=1 effectively reduces the cobalt and nickel oxidation losses and promotes the oxidation removal of iron during the remelting process of EoL superalloys.

研究论文

Process development for the direct solvent extraction of nickel and cobalt from nitrate solution:aluminum, cobalt, and nickel separation using Cyanex 272

Zela T. Ichlas, Don C. Ibana

2017, 24(1): 37-46. doi: 10.1007/s12613-017-1376-7

中文摘要(903) PDF(54) SpringerLink

摘要:
A direct solvent extraction (DSX) process for purifying nickel and cobalt from the nitric acid leach solution of nickel laterite ores was conceived and experimentally probed. The proposed process consists of two solvent extraction (SX) steps but with only one extractant-bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex® 272)-used in both steps. The first extraction step involved the removal of aluminum and zinc, whereas the second extraction step involved the separation of cobalt along with manganese from nickel. The experimental results showed essentially quantitative removal of aluminum (>97%) and zinc (>99%) in a single extraction stage using 20vol% Cyanex 272 at pH 2.1. Some cobalt (32%) and manganese (55%) were co-extracted but were easily scrubbed out completely from the loaded organic phase using dilute sulfuric acid at pH ≤ 1.38. Cobalt and manganese in the first extraction raffinate were extracted completely in four extraction stages at staggered pH values of 4.0, 4.4, 4.5, and 4.0 in the first, second, third, and fourth stages, respectively, using also 20vol% Cyanex 272. A small amount of nickel (up to 6.6%) was co-extracted but was easily scrubbed out completely with dilute sulfuric acid at pH 2.0. A flow diagram showing the input and output conditions and the metals separated under the deduced optimum conditions is presented.

研究论文

Teeming stream protection using an argon shroud during casting of steel ingots

Chao-jie Zhang, Yan-ping Bao, Min Wang, Le-chen Zhang

2017, 24(1): 47-54. doi: 10.1007/s12613-017-1377-6

中文摘要(584) PDF(30) SpringerLink

摘要:
Two kinds of argon shroud protection devices with two different basic structures were designed and investigated. Industrial experiments and numerical simulations were used to examine the protection effect, and the mechanism of air entrapment during the casting of steel ingots was analyzed. The influence of the structure of the argon shroud protection device on the protection effect was investigated. An argon shroud protection device mounted to the nozzle holder on the bottom of the ladle does not provide a good protection effect because air can easily flow into the teeming system and cause reoxidation of molten steel during teeming. By contrast, an argon shroud protection device seated on the top of the central trumpet provides an excellent protection effect, where air has little chance of flowing into the teeming system during casting. The feasibilities of the argon shroud protection devices are discussed.

研究论文

Relationship between the specific surface area of rust and the electrochemical behavior of rusted steel in a wet-dry acid corrosion environment

Wei Liu, Qing-he Zhao, Shuan-zhu Li

2017, 24(1): 55-63. doi: 10.1007/s12613-017-1378-5

中文摘要(506) PDF(13) SpringerLink

摘要:
The relationship between the specific surface area (SSA) of rust and the electrochemical behavior of rusted steel under wet-dry acid corrosion conditions was investigated. The results showed that the corrosion current density first increased and then decreased with increasing SSA of the rust during the corrosion process. The structure of the rust changed from single-layer to double-layer, and the γ-FeOOH content decreased in the inner layer of the rust with increasing corrosion time; by contrast, the γ-FeOOH content in the outer layer was constant. When the SSA of the rust was lower than the critical SSA corresponding to the relative humidity during the drying period, condensed water in the micropores of the rust could evaporate, which prompted the diffusion of O₂ into the rust and the following formation process of γ-FeOOH, leading to an increase of corrosion current density with increasing corrosion time. However, when the SSA of the rust reached or exceeded the critical SSA, condensate water in the micro-pores of the inner layer of the rust could not evaporate which inhibited the diffusion of O₂ and decreased the γ-FeOOH content in the inner rust, leading to a decrease of corrosion current density with increasing corrosion time.

研究论文

Influence of mill scale and rust layer on the corrosion resistance of low-alloy steel in simulated concrete pore solution

Jin-jie Shi, Jing Ming

2017, 24(1): 64-74. doi: 10.1007/s12613-017-1379-4

中文摘要(587) PDF(23) SpringerLink

摘要:
Electrochemical impedance spectroscopy, cyclic potentiodynamic polarization measurements, and scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy were used to investigate the influence of mill scale and rust layer on the passivation capability and chloride-induced corrosion behaviors of conventional low-carbon (LC) steel and low-alloy (LA) steel in simulated concrete pore solution. The results show that mill scale exerts different influences on the corrosion resistance of both steels at various electrochemical stages. We propose that the high long-term corrosion resistance of LA steel is mainly achieved through the synergistic effect of a gradually formed compact, adherent and well-distributed Cr-enriched inner rust layer and the physical barrier protection effect of mill scale.

研究论文

Corrosion-wear behavior of nanocrystalline Fe₈₈Si₁₂ alloy in acid and alkaline solutions

Li-cai Fu, Wen Qin, Jun Yang, Wei-min Liu, Ling-ping Zhou

2017, 24(1): 75-82. doi: 10.1007/s12613-017-1380-y

中文摘要(507) PDF(8) SpringerLink

摘要:
The corrosion-wear behavior of a nanocrystalline Fe₈₈Si₁₂ alloy disc coupled with a Si₃N₄ ball was investigated in acid (pH 3) and alkaline (pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe₈₈Si₁₂ alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe₈₈Si₁₂ alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe₈₈Si₁₂ alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si₃N₄ ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe₈₈Si₁₂ alloy in the pH 9 aqueous solution.

研究论文

Characterization of Cu-Ti powder metallurgical materials

Erdem Karakulak

2017, 24(1): 83-90. doi: 10.1007/s12613-017-1381-x

中文摘要(569) PDF(18) SpringerLink

摘要:
Powder metallurgical Cu-Ti alloys with different titanium additions produced by hot pressing were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and hardness, wear and bending tests. The addition of titanium to copper caused the formation of different intermetallic layers around titanium particles. The titanium content of the intermetallics decreased from the center of the particle to the copper matrix. The hardness, wear resistance, and bending strength of the materials increased with increasing Ti content, whereas strain in the bending test decreased. Worn surface analyses showed that different wear mechanisms were active during the wear test of specimens with different chemical compositions. Changes in the properties of the materials with titanium addition were explained by the high hardness of different Cu-Ti intermetallic phases.

研究论文

Reduction in secondary dendrite arm spacing in cast eutectic Al-Si piston alloys by cerium addition

R. Ahmad, M. B. A. Asmael, N. R. Shahizan, S. Gandouz

2017, 24(1): 91-101. doi: 10.1007/s12613-017-1382-9

中文摘要(631) PDF(21) SpringerLink

摘要:
The effects of Ce on the secondary dendrite arm spacing (SDAS) and mechanical behavior of Al-Si-Cu-Mg alloys were investigated. The reduction of SDAS at different Ce concentrations was evaluated in a directional solidification experiment via computer-aided cooling curve thermal analysis (CA CCTA). -The results showed that 0.1wt%-1.0wt% Ce addition resulted in a rapid solidification time, △T_S, and low solidification temperature, △T_S, whereas 0.1wt% Ce resulted in a fast solidification time, △t^a-Al, of the α-Al phase. Furthermore, Ce addition refined the SDAS, which was reduced to approximately 36%. The mechanical properties of the alloys with and without Ce were investigated using tensile and hardness tests. The quality index (Q) and ultimate tensile strength of (UTS) Al-Si-Cu-Mg alloys significantly improved with the addition of 0.1wt% Ce. Moreover, the base alloy hardness was improved with increasing Ce concentration.

研究论文

Characteristics of AZ31 Mg alloy joint using automatic TIG welding

Hong-tao Liu, Ji-xue Zhou, Dong-qing Zhao, Yun-teng Liu, Jian-hua Wu, Yuan-sheng Yang, Bai-chang Ma, Hai-hua Zhuang

2017, 24(1): 102-108. doi: 10.1007/s12613-017-1383-8

中文摘要(547) PDF(15) SpringerLink

摘要:
The automatic tungsten-inert gas welding (ATIGW) of AZ31 Mg alloys was performed using a six-axis robot. The evolution of the microstructure and texture of the AZ31 auto-welded joints was studied by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction. The ATIGW process resulted in coarse recrystallized grains in the heat affected zone (HAZ) and epitaxial growth of columnar grains in the fusion zone (FZ). Substantial changes of texture between the base material (BM) and the FZ were detected. The {0002} basal plane in the BM was largely parallel to the sheet rolling plane, whereas the c-axis of the crystal lattice in the FZ inclined approximately 25° with respect to the welding direction. The maximum pole density increased from 9.45 in the BM to 12.9 in the FZ. The microhardness distribution, tensile properties, and fracture features of the AZ31 auto-welded joints were also investigated.

研究论文

Study on the preparation of Pt nanocapsules

Yi-fan Zhang, Zhen Ji, Ke Chen, Bo-wen Liu, Cheng-chang Jia, Shan-wu Yang

2017, 24(1): 109-114. doi: 10.1007/s12613-017-1384-7

中文摘要(465) PDF(146) SpringerLink

摘要:
Ag@Pt core-shell nanoparticles (Ag@Pt NPs) were prepared by a co-reduction method. Pt nanocapsules with diameters of less than 10 nm were obtained by an electrochemical method. Cyclic voltammetry (CV) scanning was used to cavitate the Ag@Pt NPs, and the morphology, structure, and cavitation conditions were studied. The results indicate that the effective cavitation conditions to obtain Pt nanoparticles from Ag@Pt NPs are a scanning voltage of 0 to 0.8 V and continuous CV scanning over 2 h. This cavitation method is also applicable for the syntheses of Ir, Ru, and Ru-Pt nanocapsules.

研究论文

Low-cost solid FeS lubricant as a possible alternative to MoS₂ for producing Fe-based friction materials

Tao Peng, Qing-zhi Yan, Yan Zhang, Xiao-jiao Shi, Ming-yang Ba

2017, 24(1): 115-121. doi: 10.1007/s12613-017-1385-6

中文摘要(670) PDF(10) SpringerLink

摘要:
Three reaction systems of MoS₂-Fe, FeS-Fe, and FeS-Fe-Mo were designed to investigate the use of FeS as an alternative to MoS₂ for producing Fe-based friction materials. Samples were prepared by powder metallurgy, and their phase compositions, microstructures, mechanical properties, and friction performance were characterized. The results showed that MoS₂ reacts with the matrix to produce iron-sulfides and Mo when sintered at 1050℃. Iron-sulfides produced in the MoS₂-Fe system were distributed uniformly and continuously in the matrix, leading to optimal mechanical properties and the lowest coefficient of friction among the systems studied. The lubricity observed was hypothesized to originate from the iron-sulfides produced. The FeS-Fe-Mo system showed a phase composition, porosity, and density similar to those of the MoS₂-Fe system, but an uneven distribution of iron-sulfides and Mo in this system resulted in less-optimal mechanical properties. Finally, the FeS-Fe system showed the poorest mechanical properties among the systems studied because of the lack of Mo reinforcement. In friction tests, the formation of a sulfide layer contributed to a decrease in coefficient of friction (COF) in all of the samples.

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2017年第24卷第1期