International Journal of Minerals, Metallurgy and Materials

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A pilot-scale study of selective desulfurization via urea addition in iron ore sintering

Hong-ming Long, Xue-jian Wu, Tie-jun Chun, Zhan-xia Di, Ping Wang, Qing-min Meng

2016, 23(11): 1239-1243. doi: 10.1007/s12613-016-1344-7

中文摘要(284) PDF(10) SpringerLink

摘要:
The iron ore sintering process is the main source of SO₂ emissions in the iron and steel industry. In our previous research, we proposed a novel technology for reducing SO₂ emissions in the flue gas in the iron ore sintering process by adding urea at a given distance from the sintering grate bar. In this paper, a pilot-scale experiment was carried out in a commercial sintering plant. The results showed that, compared to the SO₂ concentration in flue gas without urea addition, the SO₂ concentration decreased substantially from 694.2 to 108.0 mg/m³ when 0.10wt% urea was added. NH₃ decomposed by urea reacted with SO₂ to produce (NH₄)₂SO₄, decreasing the SO₂ concentration in the flue gas.

Reduction behavior of hematite in the presence of coke

Ze-hong Wang, Guo-feng Li, Yong-sheng Sun, Ming-zhao He

2016, 23(11): 1244-1251. doi: 10.1007/s12613-016-1345-6

中文摘要(274) PDF(8) SpringerLink

摘要:
The reduction kinetics of hematite in the presence of coke as a reductant was studied via isothermal and non-isothermal thermodynamic analyses. The isothermal reduction of hematite was conducted at a pre-determined temperature ranging from 1423 to 1573 K. The results indicated that a higher reduction temperature led to an increased reduction degree and an increased reduction rate. The non-isothermal reduction of hematite was carried out from room temperature to 1573 K at various heating rates from 5 to 15 K·min^-1. A greater heating rate gave a greater reduction rate but decreased reduction degree. With an increase in temperature, both the reduction rate and the reduction degree increased at a smaller rate when the temperature was less than 1150 K, and they increased at a higher rate when the temperature was greater than 1150 K before completion of the reduction reaction. Both the isothermal and the non-isothermal reduction behaviors of hematite were described by the Avrami–Erofeev model. For the isothermal reduction, the apparent activation energy and pre-exponential factor were 171.25 kJ·mol^-1 and 1.80×10⁵ min^-1, respectively. In the case of non-isothermal reduction, however, the apparent activation energy and pre-exponential factor were correlated with the heating rate.

Alkaline pretreatment for chlorine removal from high-chlorine rhodochrosite

Xing-ran Zhang, Zuo-hua Liu, Wen-sheng Li, Ya-ya Cheng, Jun Du, Chang-yuan Tao

2016, 23(11): 1252-1257. doi: 10.1007/s12613-016-1346-5

中文摘要(318) PDF(7) SpringerLink

摘要:
Chloride in manganese ore adversely affects mineral extraction. The mechanisms and the factors that influence an alkali pretreatment to removal chlorine from manganese ore were explored to eliminate hazards posed by chlorine during the electrolysis of manganese. The results showed that sodium carbonate, when used as an alkaline additive, promoted the dissolution of insoluble chloride, enhanced the migration of chloride ions, and effectively stabilized Mn²⁺. The optimal conditions were a sodium carbonate concentration of 0.45 mol·L^-1, a liquid-solid ratio of 5:1 mL·g^-1, a reaction time of 1 h, and a temperature of 25°C. The chlorine removal efficiency was greater than 95%, and the ore grade (Mn) was increased by 2.7%.

Enrichment of copper and recycling of cyanide from copper–cyanide waste by solvent extraction

Teng-yue Gao, Kui-ren Liu, Qing Han, Bin-shi Xu

2016, 23(11): 1258-1263. doi: 10.1007/s12613-016-1347-4

中文摘要(282) PDF(10) SpringerLink

摘要:
The enrichment of copper from copper–cyanide wastewater by solvent extraction was investigated using a quaternary ammonium salt as an extractant. The influences of important parameters, e.g., organic-phase components, aqueous pH values, temperature, inorganic anion impurities, CN/Cu molar ratio, and stripping reagents, were examined systematically, and the optimal conditions were determined. The results indicated that copper was effectively concentrated from low-concentration solutions using Aliquat 336 and that the extraction efficiency increased linearly with increasing temperature. The aqueous pH value and concentrations of inorganic anion impurities only weakly affected the extraction process when varied in appropriate ranges. The CN/Cu molar ratio affected the extraction efficiency by changing the distribution of copper–cyanide complexes. The difference in gold leaching efficiency between using raffinate and fresh water was negligible.

Mechanism of generation of large (Ti,Nb,V)(C,N)-type precipitates in H13 + Nb tool steel

You Xie, Guo-guang Cheng, Lie Chen, Yan-dong Zhang, Qing-zhong Yan

2016, 23(11): 1264-1274. doi: 10.1007/s12613-016-1348-3

中文摘要(282) PDF(12) SpringerLink

摘要:
The characteristics and generation mechanism of (Ti,Nb,V)(C,N) precipitates larger than 2 μm in Nb-containing H13 bar steel were studied. The results show that two types of (Ti,Nb,V)(C,N) phases exist—a Ti-V-rich one and an Nb-rich one—in the form of single or complex precipitates. The sizes of the single Ti-V-rich (Ti,Nb,V)(C,N) precipitates are mostly within 5 to 10 μm, whereas the sizes of the single Nb-rich precipitates are mostly 2–5 μm. The complex precipitates are larger and contain an inner Ti-V-rich layer and an outer Nb-rich layer. The compositional distribution of (Ti,Nb,V)(C,N) is concentrated. The average composition of the single Ti-V-rich phase is (Ti_0.511V_0.356Nb_0.133)(C_xN_y), whereas that for the single Nb-rich phase is (Ti_0.061V_0.263Nb_0.676)(C_xN_y). The calculation results based on the Scheil–Gulliver model in the Thermo-Calc software combining with the thermal stability experiments show that the large phases precipitate during the solidification process. With the development of solidification, the Ti-V-rich phase precipitates first and becomes homogeneous during the subsequent temperature reduction and heat treatment processes. The Nb-rich phase appears later.

Hot deformation characteristics of as-cast high-Cr ultra-super-critical rotor steel with columnar grains

Zong-ye Ding, Qiao-dan Hu, Long Zeng, Jian-guo Li

2016, 23(11): 1275-1285. doi: 10.1007/s12613-016-1349-2

中文摘要(223) PDF(9) SpringerLink

摘要:
Isothermal hot compression tests of as-cast high-Cr ultra-super-critical (USC) rotor steel with columnar grains perpendicular to the compression direction were carried out in the temperature range from 950 to 1250°C at strain rates ranging from 0.001 to 1 s^-1. The softening mechanism was dynamic recovery (DRV) at 950°C and the strain rate of 1 s^-1, whereas it was dynamic recrystallization (DRX) under the other conditions. A modified constitutive equation based on the Arrhenius model with strain compensation reasonably predicted the flow stress under various deformation conditions, and the activation energy was calculated to be 643.92 kJ·mol^-1. The critical stresses of dynamic recrystallization under different conditions were determined from the work-hardening rate (θ)–flow stress (σ) and -∂θ/∂σ–σ curves. The optimum processing parameters via analysis of the processing map and the softening mechanism were determined to be a deformation temperature range from 1100 to 1200°C and a strain-rate range from 0.001 to 0.08 s^-1, with a power dissipation efficiency η greater than 31%.

Effects of chloride ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel

Hui-yan Li, Chao-fang Dong, Kui Xiao, Xiao-gang Li, Ping Zhong

2016, 23(11): 1286-1293. doi: 10.1007/s12613-016-1350-9

中文摘要(334) PDF(14) SpringerLink

摘要:
The effects of Cl^- ion concentration and pH values on the corrosion behavior of Cr12Ni3Co12Mo4W ultra-high-strength martensitic stainless steel (UHSMSS) were investigated by a series of electrochemical tests combined with observations by stereology microscopy and scanning electron microscopy. A critical Cl^- ion concentration was found to exist (approximately 0.1wt%), above which pitting occurred. The pitting potential decreased with increasing Cl^- ion concentration. A UHSMSS specimen tempered at 600°C exhibited a better pitting corrosion resistance than the one tempered at 400°C. The corrosion current density and passive current density of the UHSMSS tempered at 600°C decreased with increasing pH values of the corrosion solution. The pits developed a shallower dish geometry with increasing polarization potential. A lacy cover on the pits of the UHSMSS tempered at 400°C accelerated pitting, whereas corrosion products deposited in the pits of the UHSMSS tempered at 600°C hindered pitting.

Fabrication of wear-resistant layers with lamellar eutectic structure by laser surface alloying using the in situ reaction between Cr and B₄C

You-zheng Sun, Jin-bao Li, Daniel Wellburn, Chang-sheng Liu

2016, 23(11): 1294-1301. doi: 10.1007/s12613-016-1351-8

中文摘要(287) PDF(8) SpringerLink

摘要:
To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying (LSA), which is dependent on the in situ reaction between Cr and B₄C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV_0.2 883.9, which was 1.8 times greater than that of the traditional quenched layer (approximately HV 480). After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm³, which was only 29.5% of the volume loss of the traditional quenched specimen.

Influence of process parameters on the microstructural evolution of a rear axle tube during cross wedge rolling

Jia-wei Ma, Cui-ping Yang, Zhen-hua Zheng, Kang-sheng Zhang, Wen-yu Ma

2016, 23(11): 1302-1314. doi: 10.1007/s12613-016-1352-7

中文摘要(241) PDF(7) SpringerLink

摘要:
In the shaping process of cross wedge rolling (CWR), metal undergoes a complex microstructural evolution, which affects the quality and mechanical properties of the product. Through secondary development of the DEFORM-3D software, we developed a rigid plastic finite element model for a CWR-processed rear axle tube, coupled with thermomechanical and microstructural aspects of workpieces. Using the developed model, we investigated the microstructural evolution of the CWR process. Also, the influence of numerous parameters, including the initial temperature of workpieces, the roll speed, the forming angle, and the spreading angle, on the grain size and the grain-size uniformity of the rolled workpieces was analyzed. The numerical simulation was verified through rolling and metallographic experiments. Good agreement was obtained between the calculated and experimental results, which demonstrated the reliability of the model constructed in this work.

Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

Gheorghe Gurau, Carmela Gurau, Vedamanickam Sampath, Leandru Gheorghe Bujoreanu

2016, 23(11): 1315-1322. doi: 10.1007/s12613-016-1353-6

中文摘要(363) PDF(12) SpringerLink

摘要:
Low-cost iron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion (HSHPT) process on the microstructural evolution of an Fe–Mn–Si–Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ε-martensite with an HCP crystal structure and γ-phase with an FCC structure.

Effect of microstructure on the breakage of tin bronze machining chips during pulverization via jet milling

Elham Afshari, Mohammad Ghambari, Hasan Farhangi

2016, 23(11): 1323-1332. doi: 10.1007/s12613-016-1354-5

中文摘要(273) PDF(12) SpringerLink

摘要:
In this study, jet milling was used to recycle tin bronze machining chips into powder. The main purpose of this study was to assess the effect of the microstructure of tin bronze machining chips on their breakage behavior. An experimental target jet mill was used to pulverize machining chips of three different tin bronze alloys containing 7wt%, 10wt%, and 12wt% of tin. Optical and electron microscopy, as well as sieve analysis, were used to follow the trend of pulverization. Each alloy exhibited a distinct rate of size reduction, particle size distribution, and fracture surface appearance. The results showed that the degree of pulverization substantially increased with increasing tin content. This behavior was attributed to the higher number of machining cracks as well as the increased volume fraction of brittle δ phase in the alloys with higher tin contents. The δ phase was observed to strongly influence the creation of machining cracks as well as the nucleation and propagation of cracks during jet milling. In addition, a direct relationship was observed between the mean δ-phase spacing and the mean size of the jet-milled product; i.e., a decrease in the δ-phase spacing resulted in smaller particles.

Fracture behavior and microstructure analysis of Al₂O₃–MgO–CaO castables for steel-ladle purging plugs

Bin Long, Gui-ying Xu, Yong Li, Andreas Buhr

2016, 23(11): 1333-1339. doi: 10.1007/s12613-016-1355-4

中文摘要(330) PDF(14) SpringerLink

摘要:
Three different castables based on the Al₂O₃–MgO–CaO system were prepared as steel-ladle purging plug refractories: corundum- based low-cement castable (C-LCC), corundum-spinel-based low-cement castable (C-S-LCC), and corundum-spinel no-cement castable (C-S-NCC) (hydratable alumina (ρ-Al₂O₃) bonded). The fracture behavior at room temperature was tested by the method of “wedge-splitting” on samples pre-fired at different temperatures; the specific fracture energy G′_f and notched tensile strength σ_NT were obtained from these tests. In addition, the Young’s modulus E was measured by the method of resonance frequency of damping analysis (RFDA). The thermal stress resistance parameter R′′′′ calculated using the values of G′_f, σ_NT, and E was used to evaluate the thermal shock resistance of the materials. According to the microstructure analysis results, the sintering effect and the bonding type of the matrix material were different among these three castables, which explains their different fracture behaviors.

Characterization and photoluminescence properties of ultrafine copper molybdate (α-CuMoO₄) powders prepared via a combustion-like process

Mohamed Benchikhi, Rachida El Ouatib, Sophie Guillemet-Fritsch, Lahcen Er-Rakho, Bernard Durand

2016, 23(11): 1340-1345. doi: 10.1007/s12613-016-1356-3

中文摘要(364) PDF(7) SpringerLink

摘要:
We report a simple method for preparing copper(II) molybdate (CuMoO₄) powders via a combustion-like process. A gel was first prepared by the polymerizable complex method, where citric acid was used as a complexing and polymerizing agent and nitric acid was used as an oxidizing agent. The thermal decomposition behavior of the (CuMo)-precursor gel was studied by thermogravimetry–differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). We observed that the crystallization of CuMoO₄ powder was completed at 450°C. The obtained homogeneous powder was composed of grains with sizes in the range from 150 to 500 nm and exhibited a specific surface area of approximately 5 m²/g. The average grain size increased with increasing annealing temperature. The as-prepared CuMoO₄ crystals showed a strong green photoluminescence emission at room temperature under excitation at 290 nm, which we mainly interpreted on the basis of the Jahn-Teller effect on [MoO₄^2- ] complex anions. We also observed that the photoluminescence intensity increased with increasing crystallite size.

Synthesis and optical properties of turquoise- and green-colored brownmillerite-type Ba₂In_2-x-yMn_xAl_yO_5+x codoped with manganese and aluminum

Peng Jiang, Wen-hui Yang, Yun-cheng Zhou, Jian-lei Kuang, Yong Li, Ting Xiao

2016, 23(11): 1346-1351. doi: 10.1007/s12613-016-1357-2

中文摘要(278) PDF(9) SpringerLink

摘要:
Brownmillerite-type oxides Ba₂In_2-x-yMn_xAl_yO_5+x (0 ≤ x ≤ 0.6, 0 ≤ y ≤ 0.5) were prepared at 1300°C through solid-state reaction. X-ray diffraction (XRD) analysis showed that the structure symmetry evolved from orthorhombic to cubic with increasing Mn and Al contents. When y was greater than 0.3, peaks associated with small amounts of BaAl₂O₄ and Ba₂InAlO₅ impurities were observed in the XRD patterns. When substituted with a small amount of Mn (x ≤ 0.3), the Ba₂In_2-x-yMn_xAl_yO_5+x samples exhibited an intense turquoise color. The color changed to green and dark-green with increasing Mn concentration. UV–vis absorbance spectra revealed that the color changed only slightly upon Al doping. The valence state of Mn ions in Ba₂In_2-x-yMn_xAl_yO_5+x was confirmed to be +5 on the basis of X-ray photoelectron spectroscopic analysis. According to this analysis, the intense turquoise color of the Ba₂In_2-x-yMn_xAl_yO_5+x samples is rooted in the existence of Mn⁵⁺; thus, the introduction of Al does not affect the optical properties of the compounds.

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2016年第23卷第11期

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2016年第23卷第11期