International Journal of Minerals, Metallurgy and Materials

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Kinetics of leaching refractory gold ores by ultrasonic-assisted electro-chlorination

Ping Zhu, Xin-jiong Zhang, Kun-fang Li, Guang-ren Qian, Ming Zhou

2012, 19(6): 473-477. doi: 10.1007/s12613-012-0582-6

中文摘要(372) PDF(42) SpringerLink

摘要:
The resources of refractory gold ores are abundant, and their effective treatment can bring good economic benefits. This paper investigated the kinetics of leaching gold from refractory gold ores by ultrasonic-assisted electro-chlorination. The effects of ultrasound time ratio, initial hydrochloric acid concentration and leaching temperature on the kinetic parameters were discussed. It is found that the leaching ratio goes up with all the factors increasing. The reaction kinetics is controlled by diffusion. When ultrasound improves the diffusion by reducing the diffusion resistance, the activation energy increases to 37.1 kJ/mol.

Fe-Si droplets associated with graphite on blast furnace coke

Stanislav S. Gornostayev, Timo M. J. Fabritius, Olavi Kerkkonen, Jouko J. Härkki

2012, 19(6): 478-482. doi: 10.1007/s12613-012-0583-5

中文摘要(463) PDF(8) SpringerLink

摘要:
Fe-Si droplets on the surface of blast furnace (BF) coke from 25 to 50 cm at the tuyere level are mostly composed of Fe3Si, which has various shapes (round, elongated, and irregular) and penetration degrees into the BF coke matrix. The shapes and penetration degrees may depend on the saturation of molten iron by silicon during interaction with the coke matrix. The droplets are covered by a tiny shell of carbon. Graphite observed inside the droplets can be divided into two categories:well-formed tabular crystals with relatively large size and flakes with structures similar as those in cast iron. The textures of the droplets reflect composition, interaction with the coke matrix, and cooling conditions.

Physical model of fluid flow characteristics in RH-TOP vacuum refining process

Lu Lin, Yan-ping Bao, Feng Yue, Li-qiang Zhang, Hong-lin Ou

2012, 19(6): 483-489. doi: 10.1007/s12613-012-0584-4

中文摘要(285) PDF(10) SpringerLink

摘要:
To understand the characteristic of circulation flow rate in 250-t RH-TOP vacuum refining process, the l:4 water model test was established through the bubble behavior and gas holdup in the up-leg to investigate the effects of different processes and equipment parameters on the RH circulation flow rate. With the increases of lifting gas flow rate, lifting bubble travel, and the internal diameter of the up-leg, and the decrease of nozzle diameter, the work done by bubble floatage and the circulation flow rate increase. The expression of circulation flow rate was derived from the regression analysis of experiment data. Meanwhile, the influences of vacuum chamber pressure and nozzle blockage situation on the circulation flow rate were discussed in detail by the bubble behavior and gas holdup in the up-leg. It is necessary to maintain a certain vacuum chamber liquid level in the molten steel circulation flow. Compared with a nozzle with symmetrical blockage in the up-leg, when a nozzle with non-symmetrical blockage is applied, the lifting gas distribution is non-uniform, causing a great effect on the molten steel circulation flow and making the circulation flow drop largely.

Top slag refining for inclusion composition transform control in tire cord steel

Shu-hao Chen, Min Jiang, Xiao-fei He, Xin-hua Wang

2012, 19(6): 490-498. doi: 10.1007/s12613-012-0585-3

中文摘要(368) PDF(26) SpringerLink

摘要:
Controlling conditions for inclusion plasticization were calculated by FactSage, and the steel/slag reaction equilibration time was determined by pre-equilibrium experiments. Laboratory experiments with different top slags were carried out in 90 min, and industrial tests were performed based on the results of calculation and laboratory experiments. Scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to determine the morphology and composition of inclusions in tire cord steel. It is found that the shape of inclusions can be controlled well, and the composition of inclusions varies in the industrial test as the following transformation route:MnO-Al₂O₃-SiO₂→CaO-Al₂O₃-SiO₂→MnO-Al₂O₃-SiO₂. Inclusion plasticization can be achieved by controlling the binary basicity of top slag (CaO/SiO₂ by mass) around 1.0 and the (Al₂O₃) content in top slag below 10wt%. Under these controlling conditions in the industrial test, almost all of inclusions in the wire rods achieve plastic deformation.

Direct electrochemical reduction of solid vanadium oxide to metal vanadium at low temperature in molten CaCl₂-NaCl

Zhuo-fei Cai, Zhi-mei Zhang, Zhan-cheng Guo, Hui-qing Tang

2012, 19(6): 499-505. doi: 10.1007/s12613-012-0586-2

中文摘要(326) PDF(16) SpringerLink

摘要:
V₂O₅ sintered pellets and graphite rods were employed as the cathode and the anode, respectively; a molten CaCl₂-NaCl salt was used as the electrolyte. Then, V₂O₅ was directly reduced to metal vanadium by the Fray-Farthing-Chen (FFC) method at 873 K to realize low-temperature electrolysis. Two typical experimental conditions, electrolysis time and voltage, were taken into account to investigate the current efficiency and remaining oxygen content in electrolyzed products. The composition and microstructure of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). SEM observations show that a higher voltage (1.8-3.4 V) and a longer electrolysis time (2-5 h) can improve the product quality separately, that is, a lower remaining oxygen content and a more uniform microstructure. The products with an oxygen content of 0.205wt% are successfully obtained below 3.4 V for 10 h. However, the current efficiency is low, and further work is required.

Formation kinetics of austenite in pearlitic ductile iron

Payam Abdollahi, Alborz Amirsadeghi, Shahram Kheirandish, Shamsoddin Mirdamadi

2012, 19(6): 506-510. doi: 10.1007/s12613-012-0587-1

中文摘要(325) PDF(14) SpringerLink

摘要:
This work evaluated the isothermal transformation of austenite in unalloyed pearlitic ductile iron and drew the isothermal phase diagram of austenitization in the ductile iron. Austenite forms at grain boundaries and then grows up to graphite regions during austenitization. The formation kinetics of austenite complies with the Avrami equation, in which the parameter (n) ranges from 4.71 to 4.99. The start time and finish time of transformation can be calculated at each temperature using the Avrami equation.

Effects of heat treatment on the microstructures and mechanical properties of a new type of nitrogen-containing die steel

Jing-yuan Li, Peng Zhao, Jun Yanagimoto, Sumio Sugiyama, Yu-lai Chen

2012, 19(6): 511-517. doi: 10.1007/s12613-012-0588-0

中文摘要(485) PDF(30) SpringerLink

摘要:
Nitrogen can increase the strength of steels without weakening the toughness and improve the corrosion resistance at the same time. Compared with conventional nitrogen-free die steels, a new type of nitrogen-containing die steel was developed with many superior properties, such as high strength, high hardness, and good toughness. This paper focused on the effects of heat treatment on the microstructures and mechanical properties of the new type of nitrogen-containing die steel, which were investigated by the optimized deformation process and heat treatment. Isothermal spheroidal annealing and high-temperature quenching as well as high-temperature tempering were applied in the experiment by means of an orthogonal method after the steel was multiply forged. The mechanical properties of nitrogen-containing die steel forgings are better than the standard of NADCA #207-2003.

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

Jing Wang, Min-xu Lu, Lei Zhang, Wei Chang, Li-ning Xu, Li-hua Hu

2012, 19(6): 518-524. doi: 10.1007/s12613-012-0589-z

中文摘要(474) PDF(43) SpringerLink

摘要:
To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by energy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corrosion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG welding. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints produced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.

Hot ductility behavior of V-N and V-Nb microalloyed steels

Bing-hua Chen, Hao Yu

2012, 19(6): 525-529. doi: 10.1007/s12613-012-0590-6

中文摘要(354) PDF(8) SpringerLink

摘要:
The hot ductility of V-N and V-Nb microalloyed steels was investigated on a Gleeble-1500 thermomechanical simulator, and the results were compared with those of V and Nb microalloyed steels. A ductility trough is found in both the steels in the temperature range of 700 to 1050℃. Compared to the V steel, the V-N steel has a wider and deeper ductility trough with the increase of N content, due to the increased precipitation of V(C, N) in the steel. Above 930℃, when 0.047wt% V is added to the 0.028wt% Nb-containing steel, the ductility becomes worse, owing to the rise of the onset dynamic recrystallization temperature. However, the ductility gets better at 800 to 930℃ because of the coarsening of precipitates in austenite. With the improvement in ductility, the fracture mechanism is changed from intergranular to high ductile fracture in the temperature range of 800 to 1050℃.

Texture evolution of commercial pure Ti during cold rolling and recrystallization annealing

Hai-tao Jiang, Ji-xiong Liu, Zhen-li Mi, Ai-min Zhao, Yan-jun Bi

2012, 19(6): 530-535. doi: 10.1007/s12613-012-0591-5

中文摘要(256) PDF(14) SpringerLink

摘要:
X-ray diffraction (XRD) was employed to analyze the texture evolution of commercial pure (CP) Ti during cold rolling and recrystallization annealing. The texture components were measured by electron backscattered diffraction (EBSD) after recrystallization annealing. The CP Ti tends to form a texture with the basal pole tilted 30°-40° away from the normal direction toward the transverse direction. The texture of the initial hot-rolled plate can be classified into three kinds, i.e., the pyramid texture (1013)[5230] and (2021)[1015], the basal plane texture (0001)[2110], and the stronger prism texture (1120)[0001]. After cold rolling and annealing (700℃, 60 min), the main texture components are the cold-rolled texture (1125)[1123] and the recrystallized texture (1013)[5230]. The texture (2021)[1015] is inherited from the texture of the initial hot-rolled plate with the decrease of orientation density gradually. The volume contents of the cold-rolled texture {2115} <0110> and the recrystallized texture {1013} <1210> are calculated by EBSD. After recrystallization annealing, the specimen is rich in the recrystallized texture and inherits some of texture components from the cold-rolled texture. When the annealing time is prolonged, the anisotropic value decreases.

Effect of quarry dust addition on the performance of controlled low-strength material made from industrial waste incineration bottom ash

Naganathan Sivakumar, Abdul Razak Hashim, Abdul Hamid Siti Nadzriah

2012, 19(6): 536-541. doi: 10.1007/s12613-012-0592-4

中文摘要(312) PDF(9) SpringerLink

摘要:
The performance of industrial waste incineration bottom ash in controlled low-strength material (CLSM) was investigated in this paper, as the quarry dust was added. CLSM mixtures were made from the industrial waste incineration bottom ash, quarry dust, and cement. Tests for fresh density, bleeding, compressive strength, shear strength, hydraulic conductivity, and excavatability were carried out. The compressive strength ranges from 60 kPa to 6790 kPa, the friction angle varies from 5° to 19°, and the cohesion is from 4 to 604 kPa. Most of the mixtures are found to be non-excavatable. It is indicated that the quarry dust addition increases the compressive strength and shear parameters, decreases bleeding, and increases the removability modulus.

One-pot synthesis of Sb-Fe-carbon-fiber composites with in situ catalytic growth of carbon fibers

Jian Xie, Wen-tao Song, Gao-shao Cao, Xin-bing Zhao

2012, 19(6): 542-548. doi: 10.1007/s12613-012-0593-3

中文摘要(291) PDF(8) SpringerLink

摘要:
A Sb-Fe-carbon-fiber (CF) composite was prepared by a chemical vapor deposition (CVD) method with in situ growth of CFs using Sb₂O₃/Fe₂O₃ as the precursor and acetylene (C₂H₂) as the carbon source. The Sb-Fe-CF composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), and its electrochemical performance was investigated by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The Sb-Fe-CF composite shows a better cycling stability than the Sb-amorphous-carbon composite prepared by the same CVD method but using Sb₂O₃ as the precursor. Improvements in cycling stability of the Sb-Fe-CF composite can be attributed to the formation of three-dimensional network structure by CFs, which can connect Sb particles firmly. In addition, the CF layer can buffer the volume change effectively.

Influence of cross correlation step length on the surface stress of thin laser cladding Fe314 alloy coatings

Bin Liu, Shi-yun Dong, Bin-shi Xu, Peng He

2012, 19(6): 549-554. doi: 10.1007/s12613-012-0594-2

中文摘要(273) PDF(8) SpringerLink

摘要:
To measure the surface stress of thin laser cladding coatings with Rayleigh waves based on the cross correlation function, this paper introduced the influence of cross correlation step length on the stress measurement. Flat-shaped specimens made of laser cladding Fe314 alloy coatings were performed by static tensile tests, and Rayleigh wave signals were collected during the test process with an ultrasonic pulser and receiver instrument combined with two Rayleigh wave transducers. The difference in time of flight between two signals was determined based on the cross correlation function. The microstructure was observed by scanning electronic microscopy. The influence of the stress on the propagation velocity of Rayleigh waves and the relationship between the difference in time of flight and tensile stress under different cross correlation step lengths were analyzed. The inhomogeneous deformation of the coatings affects the relationship between the difference in time of flight and tensile stress; the stress measurement of the coatings is nearly constant with the increase of cross correlation step length when it attains one cycle.

Effect of Sm-doping on the morphology and magnetic properties of radio frequency magnetron sputtered Ni-Mn-Ga films

Feng-hua Chen, Min-gang Zhang, Yue-sheng Chai, Chang-wei Gong

2012, 19(6): 555-560. doi: 10.1007/s12613-012-0595-1

中文摘要(284) PDF(7) SpringerLink

摘要:
Ni_55.5Mn₂₁Ga_23.5 and Ni₅₄Mn₂₂Ga₂₃Sm₁ films were prepared by radio frequency (RF) magnetron sputtering. The effect of Sm dopant on the morphologic and magnetic properties of Ni_55.5Mn₂₁Ga_23.5 films was investigated. Sm doping can refine the particle size of the films from 100 to 60 nm, and further grain growth is not occurs even after annealing at 1073 K for 3.6 ks. Compared to Ni_55.5Mn₂₁Ga_23.5 films, Sm-doped Ni₅₄Mn₂₂Ga₂₃Sm₁ films are easier to be magnetized and have a lower martensitic transformation temperature. In addition, the Curie temperature can also be adjusted, decreasing from 350 to 325 K after Sm doping. Martensitic transformation is not observed in the Sm-free films, which is close to the Curie temperature in the Sm-doped films, giving rise to the overlap of the structural and magnetic transition temperatures.

Generation of sodium hypochlorite (NaOCl) from sodium chloride solution using C/PbO₂ and Pb/PbO₂ electrodes

Nasser Abu Ghalwa, Hassan Tamos, Mohamed ElAskalni, Abed Rhman El Agha

2012, 19(6): 561-566. doi: 10.1007/s12613-012-0596-0

中文摘要(436) PDF(13) SpringerLink

摘要:
Two modified electrodes (Pb/PbO₂ and C/PbO₂) were prepared by electrodepositing a lead oxide layer on lead and carbon substrates. These modified electrodes were used as anodes for the generation of sodium hypochlorite (NaOCl) from sodium chloride solution. Different operating conditions and factors affecting the treatment process of NaOCl generation, including current density, pH values, conductive electrolytes, and electrolysis time, were studied and optimized. By comparison the C/PbO₂ electrode shows a higher efficiency than the Pb/PbO₂ electrode for the generation of NaOCl.

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2012年第19卷第6期