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2014年  第21卷  第7期

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Artificial neural network approach to assess selective flocculation on hematite and kaolinite
Lopamudra Panda, P. K. Banerjee, Surendra Kumar Biswal, R. Venugopal, N. R. Mandre
2014, 21(7): 637-646. doi: 10.1007/s12613-014-0952-3
摘要:
Because of the current depletion of high grade reserves, beneficiation of low grade ore, tailings produced and tailings stored in tailing ponds is needed to fulfill the market demand. Selective flocculation is one alternative process that could be used for the beneficiation of ultra-fine material. This process has not been extensively used commercially because of its complex dependency on process parameters. In this paper, a selective flocculation process, using synthetic mixtures of hematite and kaolinite in different ratios, was attempted, and the adsorption mechanism was investigated by Fourier transform infrared (FTIR) spectroscopy. A three-layer artificial neural network (ANN) model (4-4-3) was used to predict the separation performance of the process in terms of grade, Fe recovery, and separation efficiency. The model values were in good agreement with experimental values.
Thermodynamic analysis of the compositional control of inclusions in cutting-wire steel
Jing Zhang, Fu-ming Wang, Chang-rong Li
2014, 21(7): 647-653. doi: 10.1007/s12613-014-0953-2
摘要:
Data from a thermodynamic database and the calculation software FactSage were used to investigate the phase diagrams of the MnO-CaO-SiO2-Al2O3 system in cutting-wire steel and the effects of oxide components on the low-melting-point (LMP) zone in the corresponding phase diagrams. Furthermore, the activities of oxide components in the quaternary system at an Al2O3 content of 25wt% were calculated. The contents of dissolved [Al] and [O] in liquid steel in equilibrium with LMP inclusions in the MnO-CaO-SiO2-Al2O3 system were optimized. The results show that the MnO-CaO-SiO2-Al2O3 system possesses the largest LMP zone (below 1400°C) at an Al2O3 content of 25wt% and that the CaO content should be simultaneously controlled in the range of 40wt% to 45wt%. The activities of the oxide components CaO, MnO, and SiO2 should be restricted in the ranges of 0 to 0.05, 0.01 to 0.6, and 0.001 to 0.8, respectively. To obtain LMP inclusions, the [Al] and [O] contents in cutting-wire steel must be controlled within the ranges of 0.5×10-6 to 1.0×10-5 and 3.0×10-6 to 5.0×10-5, respectively.
Effect of manganese sulfide on the precipitation behavior of tin in steel
Gui-lin Sun, Bo Song, Ling-zhi Yang, Su-fen Tao, Yong Yang
2014, 21(7): 654-659. doi: 10.1007/s12613-014-0954-1
摘要:
Tramp elements such as tin are considered harmful to steel because of hot brittleness they induce at high temperatures. Because tramp elements retained in steel scrap will be enriched in new steel due to the difficultly of their removal, studies on the precipitation behavior of tin are essential. In this study, the effects of different inclusions on the precipitation behavior of tin in steel were studied. The results show that the tin-rich phase precipitates at austenite grain boundaries in an Fe-5%Sn alloy without MnS precipitates, whereas Sn precipitates at the boundaries of MnS inclusions in steel that contains MnS precipitates. MnS is more effective than silicon dioxide or aluminum oxide as a nucleation site for the precipitation of the tin phase, which is consistent with the disregistry between the lattice parameters of the tin phase and those of the inclusions.
Equilibrium between titanium ions and high-purity titanium electrorefining in a NaCl-KCl melt
Jian-xun Song, Qiu-yu Wang, Guo-jing Hu, Xiao-bo Zhu, Shu-qiang Jiao, Hong-min Zhu
2014, 21(7): 660-665. doi: 10.1007/s12613-014-0955-0
摘要:
TiClx (x = 2.17) was prepared by using titanium sponge to reduce the concentration of TiCl4 in a NaCl-KCl melt under negative pressure. The as-prepared NaCl-KCl-TiClx melt was employed as the electrolyte, and two parallel crude titanium plates and one high-purity titanium plate were used as the anode and cathode, respectively. A series of electrochemical tests were performed to investigate the influence of electrolytic parameters on the current efficiency and quality of cathodic products. The results indicated that the quality of cathodic products was related to the current efficiency, which is significantly dependent on the current density and the initial concentration of titanium ions. The significance of this study is the attainment of high-purity titanium with a low oxygen content of 30×10-6.
3D stress simulation and parameter design during twin-roll casting of 304 stainless steel based on the Anand model
Jing Guo, Yuan-yuan Liu, Li-gang Liu, Yue Zhang, Qing-xiang Yang
2014, 21(7): 666-673. doi: 10.1007/s12613-014-0956-z
摘要:
This study first investigated cracks on the surface of an actual steel strip. Formulating the Anand model in ANSYS software, we then simulated the stress field in the molten pool of type 304 stainless steel during the twin-roll casting process. Parameters affecting the stress distribution in the molten pool were analyzed in detail and optimized. After twin-roll casting, a large number of transgranular and intergranular cracks resided on the surface of the thin steel strip, and followed a tortuous path. In the molten pool, stress was enhanced at the exit and at the roller contact positions. The stress at the exit decreased with increasing casting speed and pouring temperature. To ensure high quality of the fabricated strips, the casting speed and pouring temperature should be controlled above 0.7 m/s and 1520°C, respectively.
Effect of hot rolling on the microstructure and impact absorbed energy of the strip steel by CSP
Jing-jing Yang, Run Wu, Wen Liang, Zhi-dong Xiang, Meng-xia Tang
2014, 21(7): 674-681. doi: 10.1007/s12613-014-0957-y
摘要:
The microstructures and impact absorbed energies at various temperatures were investigated for steel strips hot rolled to thickness reductions of 95.5%, 96.0%, 96.5%, 97.0%, and 97.5%. Results indicate that grain refinement can be realized with an increase in hot rolling reduction. Besides, finer precipitates can be achieved with an increase in hot rolling reduction from 95.5% to 97.0%. The impact absorbed energy decreases with a decrease in testing temperature for steel strips hot rolled to 95.5%, 96.0%, and 96.5% reductions in thickness. However, in the case of steel strips hot rolled to 97.0% and 97.5% reductions in thickness, the impact absorbed energy remained almost constant with a decrease in testing temperature.
Observation of etch pits in Fe-36wt%Ni Invar alloy
Dong-zhu Lu, Min-jie Wu
2014, 21(7): 682-686. doi: 10.1007/s12613-014-0958-x
摘要:
To indirectly investigate the dislocation behavior of Fe-36wt%Ni Invar alloy by the etch pit method, polished Invar specimens were etched by a solution containing 4 g copper sulfate, 20 mL hydrochloric acid, and 20 mL deionized water for 2 min. Etch pits in the etched surfaces were observed. All the etch pits in one specific grain exhibited similar shapes, which are closely related to the grain orientations. These etch pits were characterized as dislocation etch pits. It was observed that etch pits arranged along grain boundaries, gathered at grain tips and strip-like etch pit clusters passed through a number of grains in the pure Invar specimens. After the addition of a small amount of alloying elements, the identification of a single dislocation etch pit is challenging compared with the pure Invar alloy. Thus, the observation of etch pits facilitates the investigation on the dislocation behavior of the pure Invar alloy. In addition, alloying elements may affect the densities and sizes of etch pits.
Effect of strain rate on the compressive deformation behaviors of lotus-type porous copper
Xin-hua Liu, Hai-you Huang, Jian-xin Xie
2014, 21(7): 687-695. doi: 10.1007/s12613-014-0959-9
摘要:
Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3–2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar (SHPB) were used to investigate the effect of strain rate on the compressive deformation behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate (< 1.0 s-1), the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.
Structural and mechanical properties of 7075 alloy strips fabricated by roll-casting in a static magnetic field
Xin Su, Guang-ming Xu, Jiu-wen Jiang
2014, 21(7): 696-701. doi: 10.1007/s12613-014-0960-3
摘要:
The influences of a 0.2 T static magnetic field on the microstructure of 7075 aluminum alloys sheets produced with a twin-roll continuous caster at 675°C were investigated in this paper. Under a uniform magnetic field, the primary dendrites were refined and tended to be equiaxed. The microstructure consisted of an intermediate case between dendritic and equiaxed grains. Moreover, the use of an external static field in the twin-roll casting process can reduce heat discharge, resulting in a decrease in undercooling, and may also account for the abatement of segregation bands. In addition, the static magnetic field effectively improved the solute mixing capacity, and the added atoms more easily diffused from precipitates to the α-Al matrix, which resulted in an increase in the mechanical properties of the rolled sheets. Specimens prepared both in the presence of a static magnetic field and in the absence of a static magnetic field exhibited brittle-fracture characteristics.
Preparation of high-strength Al-Mg-Si-Cu-Fe alloy via heat treatment and rolling
Chong-yu Liu, Peng-fei Yu, Xiao-ying Wang, Ming-zhen Ma, Ri-ping Liu
2014, 21(7): 702-710. doi: 10.1007/s12613-014-0961-2
摘要:
An Al-Mg-Si-Cu-Fe alloy was solid-solution treated at 560°C for 3 h and then cooled by water quenching or furnace cooling. The alloy samples which underwent cooling by these two methods were rolled at different temperatures. The microstructure and mechanical properties of the rolled alloys were investigated by optical microscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis, and tensile testing. For the water-quenched alloys, the peak tensile strength and elongation occurred at a rolling temperature of 180°C. For the furnace-cooled alloys, the tensile strength decreased initially, until the rolling temperature of 420°C, and then increased; the elongation increased consistently with increasing rolling temperature. The effects of grain boundary hardening and dislocation hardening on the mechanical properties of these rolled alloys decreased with increases in rolling temperature. The mechanical properties of the 180°C rolling water-quenched alloy were also improved by the presence of β″ phase. Above 420°C, the effect of solid-solution hardening on the mechanical properties of the rolled alloys increased with increases in rolling temperature.
Fabrication and characterization of nanocrystalline Al/Al12(Fe,V)3Si alloys by consolidation of mechanically alloyed powders
Hamid Ashrafi, Rahmatollah Emadi, Mohammad Hosein Enayati
2014, 21(7): 711-719. doi: 10.1007/s12613-014-0962-1
摘要:
The aim of this study was to produce bulk nanocrystalline Al/Al12(Fe,V)3Si alloys by mechanical alloying (MA) and subsequent hot pressing (HP) of elemental powders. A nanostructured Al-based solid solution was formed by MA of elemental powders for 60 h. After HP of the as-milled powders at 550°C for 20 min, the Al12(Fe,V)3Si phase was precipitated in a nanocrystalline Al matrix. Scanning electron microscopy (SEM) images of the bulk samples represented a homogeneous and uniform microstructure that was superior to those previously obtained by rapid solidification-powder metallurgy (RS-PM). Nanostructured Al-8.5Fe-1.3V-1.7Si and Al-11.6Fe-1.3V-2.3Si alloys exhibited high HV hardness values of ∼205 and ∼254, respectively, which are significantly higher than those reported for the RS-PM counterparts.
Thermoelectric properties of Al substituted misfit cobaltite Ca3(Co1-xAlx)4O9 at low temperature
Yi Liu, Hong-mei Chen, Jin-lian Hu, Xu-bing Tang, Hai-jin Li, Wei Wang
2014, 21(7): 720-725. doi: 10.1007/s12613-014-0963-0
摘要:
Thermoelectric properties of Al substituted compounds Ca3(Co1-xAlx)4O9 (x = 0, 0.03, 0.05), prepared by a sol-gel process, have been investigated in the temperature range 305–20 K. The results indicate that after Al substitution for Co in Ca3(Co1-xAlx)4O9, the direct current electrical resistivity and thermopower increase due to the reduction of carrier concentration. Experiments show that Al substitution results in decreased lattice thermal conductivity. The figure of merit of temperature behavior suggests that Ca3(Co0.97Al0.03)4O9 would be a promising candidate thermoelectric material for high-temperature thermoelectric application.
Preparation of NiO nanoparticles from Ni(OH)2·NiCO3·4H2O precursor by mechanical activation
Kolsoom Ahmadisoltansaraei, Javad Moghaddam
2014, 21(7): 726-735. doi: 10.1007/s12613-014-0964-z
摘要:
A mechanical activation process was introduced as a facile method for producing nickel oxide nanopowders. The precursor compound Ni(OH)2·NiCO3·4H2O was synthesized by chemical precipitation. The precursor was milled with NaCl diluent. A high-energy ball milling process led to decomposition of the precursor and subsequent dispersal in NaCl media. Nickel oxide nanocrystalline powders were produced by subsequent heat treatment and water washing. Milling rotation speed, milling time, ball-to-powder ratio (BPR), and nickel chloride-to-precursor ratio were introduced as influential parameters on the wavelength of maximum absorption (λmax). The effects of these parameters were investigated by the Taguchi method. The optimum conditions for this study were a milling rotation speed of 150 r/min, a milling time of 20 h, a BPR of 15/1, and a NaCl-to-powder weight ratio (NPR) of 6/1. In these conditions, λmax was predicted to be 292 nm. The structural properties of the samples were determined by field emission scanning electron microscopy, X-ray diffraction, and energy dispersive spectrometry.
Optical properties of cobalt xanthate films on different substrates
İ. A. Kariper, T. Özpozan
2014, 21(7): 736-740. doi: 10.1007/s12613-014-0965-y
摘要:
Cobalt isopropyl xanthate thin films (CXTFs) were deposited via chemical bath deposition onto different substrates: commercial glass (CG), indium tin oxide (ITO), and poly(methyl methacrylate) (PMM). Isopropyl xanthate was synthesized according to a method described in the literature. The cobalt nitrate and isopropyl xanthate were mixed in a beaker, which allowed the thin films to be deposited via a simple ion-ion mechanism. The transmission, reflectivity, refractive index, dielectric constant, and optical conductivity were investigated for various thin films coated onto different substrates. An ultraviolet-visible spectrophotometer was used to measure the optical properties of the thin films. The lowest value of the transmission and the highest value of the refractive index were observed for the thin films deposited onto PMM. The structure of the cobalt xanthate was characterized by Fourier transform infrared (FTIR) spectroscopy, which was measured using a Perkin-Elmer Spectrum 400 spectrometer. The stretching vibration of the Co-S bonds was observed at 359 cm-1 in the FTIR spectrum of the CXTFs.