International Journal of Minerals, Metallurgy and Materials

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Effects of electrical resistance on the spontaneous combustion tendency of coal and the interaction matrix concept

O. S. Yildirim, C. Sensogut, M. K. Gokay

2006, 13(1): 1-6. doi: 10.1016/S1005-8850(06)60003-0

中文摘要(206) PDF(13) SpringerLink

摘要:
There have been several developments in determining the spontaneous combustion liability of coal. Most of the methods of concern have purely been based on the internal properties of the coal itself. The relation between the crossing-point method and the electrical resistance of coal was examined here to outline the spontaneous combustion tendency of coal. The electrical resistance property of coal was looked into as a decision-making parameter of the interaction matrix concept for the final decision on the spontaneous combustion tendency.

Mineral

Efficacy of chalcopyrite bioleaching using a pure and a mixed bacterium

Muqing Qiu, Shuiying Xiong, Weimin Zhang

2006, 13(1): 7-10. doi: 10.1016/S1005-8850(06)60004-2

中文摘要(234) PDF(14) SpringerLink

摘要:
To determine the efficacy of chalcopyrite bioleaching using pure cultures of Thiobacillus ferrooxidans or Thiobacillus thiooxidans and a mixed culture composed of Thiobacillus ferrooxidans and Thiobacillus thiooxidans, experiments were carried out in shake flasks with [Fe²⁺] 4 g·L^-1 and S 1 g·L^-1 at pH=1.80, 130 r/min and 30℃. The tests showed that the copper extraction in a mixed culture composed of Thiobacillus ferrooxidans and Thiobacillus thiooxidans is higher than that in a pure culture. On the other hand, an important potential of Thiobacillus thiooxidans to leaching chalcopyrite was indicated. Thiobacillus thiooxidans can prevent jarosites accumulating on the substrate and allow further copper to dissolute through the action of ferric ion. The selection of the suitable pH in a leaching solution would be significant. Thiobacillus thiooxidans and Thiobacillus ferrooxidans play an important role in the bioleaching process. Finally, the mechanism and the reason for iron precipitation were also discussed in detail.

Mineral

Seepage effects of groundwater and its make-up water on triggering ground subsidence

Zhenhua Ouyang, Meifeng Cai, Changhong Li, Mowen Xie

2006, 13(1): 11-15. doi: 10.1016/S1005-8850(06)60005-4

中文摘要(234) PDF(13) SpringerLink

摘要:
The functioning mechanism of groundwater and its make-up water in the process of ground subsidence was studied from such three aspects as osmotic corrasion, osmotic pressure effect and concretion effect. As to osmotic corrasion, its forming conditions, mechanical mechanism and process were analyzed. As to osmotic pressure effect, it was mainly studied from hydrostatic pressurizing effect, sop softening effect and negative pressure sealing effect. Through concretion and saturation of soil, the factors of concretion settlement were analyzed. The results showed that both groundwater and its make-up water are important triggering factors to ground subsidence.

Metallurgy

Formation of CaO-TiO₂-MgO-Al₂O₃ dual phase inclusion in Ti stabilized stainless steel

Hongguang Zheng, Weiqing Chen

2006, 13(1): 16-20. doi: 10.1016/S1005-8850(06)60006-6

中文摘要(326) PDF(17) SpringerLink

摘要:
The formation of CaO-TiO₂-MgO-Al₂O₃ dual phase inclusion in 321 stainless steel was investigated in the laboratory. The result indicated that the condition for the formation of CaOTiO₂-MgOAl₂O₃ in 321 steel is [Ca]>0.001wt%, [Ti]>0.1wt%, and [Al]>0.01wt%. The mechanism is the following: Al₂O₃ inclusion turns into CaO-Al₂O₃ after Ca-Si wire is fed into the molten steel; [Mg] is then obtained by reducing MgO in slag or crucible wall by [Al] and [Ti]; finally CaO-Al₂O₃ inclusion is changed into CaO-TiO₂-MgO-Al₂O₃ by the reaction with [Mg], [Ti], and [O] in the molten steel simultaneously.

Metallurgy

Online forecasting model of tundish nozzle clogging

Fangming Yuan, Xinghua Wang, Jiongming Zhang, Li Zhang

2006, 13(1): 21-24. doi: 10.1016/S1005-8850(06)60007-8

中文摘要(200) PDF(24) SpringerLink

摘要:
A nozzle clogging online forecasting model based on hydrodynamics engineering was developed, in which the actual flow rate was calculated from the mold width, thickness, and casting speed. There is a linear relationship between the theoretical flow rate and the slide gate opening ratio as the molten steel level, argon flow rate, and the top slag weight are kept constant, and the relationship can be obtained by regression of the data collected at the beginning of the first heat in each casting sequence when the nozzle clogging does not occur. Then, during the casting, the theoretical flow rate can be calculated at intervals of one second. Comparing the theoretical flow rate with the actual flow rate, the online nozzle clogging ratio can be obtained at intervals of one second. The computer model based on the conception of the nozzle clogging ratio can display the degree of the nozzle clogging intuitively.

Metallurgy

A new hybrid method—combined heat flux method with Monte-Carlo method to analyze thermal radiation

Zengwu Zhao, Daqiang Cang, Wenfei Wu, Yike Li, Baowei Li

2006, 13(1): 25-28. doi: 10.1016/S1005-8850(06)60008-X

中文摘要(198) PDF(13) SpringerLink

摘要:
A new hybrid method, Monte-Carlo-Heat-Flux (MCHF) method, was presented to analyze the radiative heat transfer of participating medium in a three-dimensional rectangular enclosure using combined the Monte-Carlo method with the heat flux method. Its accuracy and reliability was proved by comparing the computational results with exact results from classical "Zone Method".

Materials

Application of the gel casting process in iron powder metallurgy

Chengchang Jia, Weihua Liu, Zhimeng Guo

2006, 13(1): 29-33. doi: 10.1016/S1005-8850(06)60009-1

中文摘要(278) PDF(15) SpringerLink

摘要:
The effects of various gel casting process parameters such as the dispersant and solid loading on the rheology of Fe slurries, molding, and sintering behaviors were studied. The relationship between solid loading and viscidity in the process of iron base powder metallurgy was researched to obtain better microstructure and properties. The results showed that the viscosity of Fe slurries is obviously reduced with the increase of the dispersant. The suitable parameters are as follows: the solid loading is 61% and sintering temperature is 1180℃. Iron parts with relatively high density and better properties were obtained by the gel casting process.

Materials

Research on flow stress in ferrite deformation of a Ti-IF steel

Guang Xu, Chushao Xu, Jiarong Zhao, Xianjun Liu

2006, 13(1): 34-36. doi: 10.1016/S1005-8850(06)60010-8

中文摘要(161) PDF(10) SpringerLink

摘要:
The experiments of the ferrite warm deformation of ultra-low carbon (ULC) Ti-IF steel were carried out on a hot simulator and the influences of deformation temperature, strain, and strain rate on the flow stress were analyzed. New flow stress models suitable to ferrite warm forming of Ti-IF steel were given on the basis of analyzing the influence of deformation technology parameters on the flow stress.

Materials

Electrochemical corrosion behavior of carbon steel with bulk coating holidays

Yiquan Song, Cuiwei Du, Xiaogang Li

2006, 13(1): 37-43. doi: 10.1016/S1005-8850(06)60011-X

中文摘要(270) PDF(8) SpringerLink

摘要:
With epoxy coal tar as the coating material, the electrochemical corrosion behavior of Q235 with different kinds of bulk coating holidays has been investigated with EIS (Electrochemical Impedance Spectroscopy) in a 3.5vol% NaCl aqueous solution. The area ratio of bulk coating holiday to total coating area of steel is 4.91%. The experimental results showed that at free corrosion potential, the corrosion of carbon steel with disbonded coating holiday is heavier than that with broken holiday and disbonded & broken holiday with time; Moreover, the effectiveness of Cathodic Protection (CP) of carbon steel with broken holiday is better than that with disbonded holiday and disbonded & broken holiday on CP potential -850 mV (vs CSE). Further analysis indicated that the two main reasons for corrosion are electrolyte solution slowly penetrating the coating, and crevice corrosion at steel/coating interface near holidays. The ratio of impedance amplitude (Z) of different frequency to minimum frequency is defined as K value. The change rate of K with frequency is related to the type of coating holiday.

Materials

Effect of HCO₃^- concentration on CO₂ corrosion in oil and gas fields

Guoan Zhang, Minxu Lu, Chengwen Chai, Yinshun Wu

2006, 13(1): 44-49. doi: 10.1016/S1005-8850(06)60012-1

中文摘要(243) PDF(11) SpringerLink

摘要:
The effect of HCO₃^- concentration on CO₂ corrosion was investigated by polarization measurement of potentiodynamic scans and weight-loss method. Under the conditions of high pressure and high temperature, the corrosion rate of steel X65 decreased with the increase of HCO₃^- concentration, while pH of solution increased. SEM, EDS, and XRD results of the corrosion scales indicated that the typical FeCO₃ crystallite was found at low HCO₃^- concentration but Ca(Fe,Mg)(CO₃)₂ was found at high HCO₃^- concentration. Ca²⁺ and Mg²⁺ are precipitated preferential to Fe²⁺ at high pH value. Potentiodynamic polarization curves showed that the cathodic current density decreases with the increase of HCO₃^- concentration at low HCO₃^- concentration. When the HCO₃^- concentration reaches 0.126 mol/L, increasing HCO₃^- concentration promotes cathodic reactions. Anodic behavior is an active process at low HCO₃^- concentration and the anodic current density decreases with the increase of HCO₃^- concentration. An evident active-passive behavior is exhibited in anodic process at 0.126 mol/L HCO₃^-

Materials

A creep technique for monitoring the aging precipitation in Cu-Nb bainitic steels

Xuemin Wang, Bing Cao, Guifeng Zhou, Chuang Li, Xinlai He

2006, 13(1): 50-53. doi: 10.1016/S1005-8850(06)60013-3

中文摘要(206) PDF(14) SpringerLink

摘要:
A creep technique was applied on a Gleeble-1500 thermal simulator for monitoring the aging precipitation in ultra-low carbon steels containing various coppers. The aging hardening curve was obtained by the hardness testing. With the aid of an optical microscope and TEM, the microstructure and the aging precipitates were detected. The results indicate that when the precipitation occurs during the creep a plateau will appear on the creep curve; the left-hand and right-hand endings of the plateau correspond to the precipitation start (P_s) and finish (P_f) times, respectively. The P_f obtained from the creep curve coincides with the peak hardness time (t_p) at the aging hardening curve. A precipitation-time-temperature (PTT) diagram of the steel can be obtained.

Materials

Analysis of bending on the front end of sheet during hot rolling

Jiquan Sun, Haibin Zhang, Quancheng Yu

2006, 13(1): 54-59. doi: 10.1016/S1005-8850(06)60014-5

中文摘要(177) PDF(8) SpringerLink

摘要:
The analysis of bending in finishing rolling was performed. An asymmetrical rolling force model was established, and the upper and lower neutral points were determined. The bending which resulted from the asymmetrical rolling force at the roll gap was studied and related flexibility equations were proposed according to elastic mechanics. Moreover, material mechanics was used to analyze the effects of temperature difference and self-weight on the bending out of the roll gap, and the flexibility equations were constructed. The main factors on bending were summed up, and the bending rule in the rolling could be obtained. In addition practical calculation was made with the production data of ribbon steel from Laiwu Iron & Steel Group Co. Ltd.

Materials

Evaluation of the mold-filling ability of alloy melt in squeeze casting

Haiying Zhang, Shaming Xing, Qinghua Zhang, Jianbo Tan, Wen Liu

2006, 13(1): 60-66. doi: 10.1016/S1005-8850(06)60015-7

中文摘要(183) PDF(7) SpringerLink

摘要:
The mold-filling ability of alloy melt in squeeze casting process was evaluated by means of the maximum length of Archimedes spiral line. A theoretical evaluating model to predict the maximum filling length was built based on the flowing theory of the incompressible viscous fluid. It was proved by experiments and calculations that the mold-filling pressure and velocity are prominent influencing factors on the mold-filling ability of alloy melt. The mold-filling ability increases with the increase of the mold-filling pressure and the decrease of the proper mold-filling velocity. Moreover, the pouring temperature relatively has less effect on the mold-filling ability under the experimental conditions. The maximum deviation of theoretical calculating values with experimental results is less than 15%. The model can quantitatively estimate the effect of every factor on the mold-filling ability.

Materials

Grain growth of Al-4Cu-Mg alloy during isothermal heat treatment

Haitao Jiang, Miaoquan Li

2006, 13(1): 67-72. doi: 10.1016/S1005-8850(06)60016-9

中文摘要(184) PDF(8) SpringerLink

摘要:
The microstructure of an Al-4Cu-Mg alloy during isothermal heat treatment in the Strain Induced Melt Activation (SIMA) process was investigated and the kinetics of grain growth was analyzed. The grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy coincided with the Ostwald ripening theory. During isothermal heat treatment, both grain shape and the high volume fraction of solid phase have significant effects on grain growth. Therefore, a new grain growth model based on the Ostwald ripening theory was proposed taking into consideration the grain shape and the volume fraction of solid phase. By comparing the calculated results with the experimental results, it was confirmed that the present model could be applied to grain growth during isothermal heat treatment of the Al-4Cu-Mg alloy in the SIMA process.

Materials

Microstructure and penetration behavior of electroformed copper liners of shaped charges during explosive detonation deformation

Ailing Fan, Wenhuai Tian, Qi Sun, Baoshen Wang

2006, 13(1): 73-77. doi: 10.1016/S1005-8850(06)60017-0

中文摘要(266) PDF(9) SpringerLink

摘要:
The microstructure in the electroformed copper liners of shaped charges prepared with different electrolytes was studied by Scanning Electron Microscopy (SEM) and Electron Backscattering Kikuchi Pattern (EBSP) methods. SEM observations revealed the existence of columnar grains in electroformed copper liners of shaped charges formed by electrolyte without any additive and the average grain size is about 3 μm. When an additive is introduced to the electrolyte, the grains formed in the copper liners become equiaxed and finer. EBSP results show that the columnar grain grown during electroformation has the most preferential growth direction, whereas a micro-texture does not exit in the specimen prepared by electrolyte with the additive. Further, explosive detonation deformation experiments show that penetration depth is dramatically improved when the electroformed copper liners of shaped charges exhibit equiaxed grains.

Materials

Research on the Fe-silicon nitride material self-producing N₂ at high temperature

Junhong Chen, Xueda Wang, Jialin Sun, Huasheng Zhan, Wen Song

2006, 13(1): 78-81. doi: 10.1016/S1005-8850(06)60018-2

中文摘要(192) PDF(21) SpringerLink

摘要:
The Fe-silicon nitride synthesized by flashing combustion process was studied to determine the reaction temperature between Fe and silicon nitride, the account of N₂ given out in the course of the reaction, and the change of the microstructure during calcination. The results showed that at 1127.2℃ the Fe-silicon nitride self-reacts and releases N₂ and under 101.3 kPa the volume of N₂ given out in the course of the reaction is 20 times more than that of the starting material. N₂ is produced quickly, and completes in several decade seconds. With the producing of N₂, the structure of Silicon Nitride around Fe becomes loose and porous, or cracks are formed by the reaction between Fe and silicon nitride. So if it is made use of that Fe-silicon nitride self-producing N₂ at the high temperature, the performance of the material on a base of Fe-silicon nitride could be greatly improved.

Materials

Preparation and characterization of calcium aluminate by chemical synthesis

Feng Chen, Yanruo Hong, Jialin Sun, Jinglong Bu

2006, 13(1): 82-86. doi: 10.1016/S1005-8850(06)60019-4

中文摘要(386) PDF(13) SpringerLink

摘要:
Saturated Ca(OH)₂ and AlCl₃ solutions were used to synthesize calcium aluminate hydrate precipitates at room temperature; high purity calcium aluminate powders with stable phases were made by calcination of the precursors at a temperature as low as 1100℃. PSD and BET analysis revealed the particles with sizes ranging from submicrometer to several micrometers and with a specific area of 13 nr/g. The measurement of hydraulic exotherm revealed that the exothermal rate is in peak for about 2 h. The exothermal quantities are 449.24 J/g at 12 h and 488.38 J/g at 24 h. Its strength development is quick and the 1 day curing strength is almost equal to 100% of the 3 days curing strength in the mortar test.

Materials

Pressureless reactive sintering mechanism of nanocrystalline Bi₂O₃-Y₂O₃ solid electrolyte

Qiang Zhen, Liangyan Dong, Gang Shi, Rong Li, Weiming He, Jianqiang Liu

2006, 13(1): 87-91. doi: 10.1016/S1005-8850(06)60020-0

中文摘要(213) PDF(11) SpringerLink

摘要:
The nanocrystalline Bi₂O₃-Y₂O₃ solid electrolyte material was synthesized by pressureless reactive sintering process with Bi₂O₃ and Y₂O₃ nano mixed powder as raw materials, which was prepared by a chemical coprecipitation process. The study on the behavior of nano δ-Bi₂O₃ formation and its grain growth showed that the solid solution reaction of Y₂O₃ and β-Bi₂O₃ to form δ-Bi₂O₃ occurs mainly in the initial stage of sintering process, and nano δ-Bi₂O₃ crystal grains grow approximately following the rule of paracurve ((D-D₀)²=K·t) during sintering process. After sintered at 600℃ for 2 h, the samples could reach above 96% in relative density and have dense microstructure with few remaining pores, the δ-Bi₂O₃ grains are less than 100 nm in size.

Materials

Effect of hydration film on scanning images of atomic force microscope

Changsheng Peng, Qingbao Gu, Hong Meng, Shaoxian Song

2006, 13(1): 92-96. doi: 10.1016/S1005-8850(06)60021-2

中文摘要(240) PDF(6) SpringerLink

摘要:
A standard calibration grating was used for image scanning to investigate the effect of hydration films on imaging resolution by Atomic Force Microscope (AFM). The results showed that the hydration films greatly affect the imaging resolution for the tapping mode, but no evident effect on the contact mode. The possible reasons for the effect of hydration films on scanning images of AFM are also brought forward here.

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2006年第13卷第1期