International Journal of Minerals, Metallurgy and Materials

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Mass transfer coefficients in metallurgical reactors

Ying Qu

2003, 10(2): 1-9.

中文摘要(332) PDF(21) SpringerLink

摘要:
An overview on the application and achievements of physico-mathematical modeling of metallurgical processes in China is briefly declared. The important role of coefficients in model formulation is shown from our experience. The mass transfer coefficients of the slag-metal reactions and the gas-metal reactions are discussed referring to the flow conditions near the interface. The influence of the surface-active species on the mass transfer and the inteffacial reaction is also discussed briefly.

Mineral

Monitoring and analysis of nonlinear dynamic damage of transport roadway supported by composite hard rock materials in Linglong Gold Mine

Meifeng Cai, Xingping Lai

2003, 10(2): 10-15.

中文摘要(289) PDF(15) SpringerLink

摘要:
The study concentrates mainly on the development of failure process in composite rock mass. By use of acoustic emission (AE), convergence inspection, pressure monitoring, level measurement techniques and the modem signal analysis technology, as well as scan electron microscopy (SEM) experiment, various aspects of nonlinear dynamic damage of composite rock mass surrounding the transport roadway in Linglong gold mine are discussed. According to the monitoring results, the stability of the rock mass can be synthetically evaluated, and the intrinsic relation between the damage and the characteristic parameters of acoustic emission can be determined. The location of the damage of rock mass can also be detected based on the acoustic emission couple monitoring signals. Finally, the key factors which influence the stability of the transport roadway supported by composite hard rock materials are found out.

Mineral

A penetrative addictive for water infusion in coal seams

Longzhe Jin, Wen Ni, Qingsong Wang, Wei Wei

2003, 10(2): 16-20.

中文摘要(271) PDF(8) SpringerLink

摘要:
The manufacturing process, characteristics, and application results of a rod-like penetrative additive (the penetrative rod) were discussed. The components and functions of the penetrative rod were studied carefully. A large number of orthogonal combined tests were carried out and over 100 sample molds were made. Ultimately the components were decided after careful selection among these molds, mainly including hygroscopic major components and auxiliary material. The results of on-site practical application show that such an addictive can increase the water penetrative ability effectively and has a remarkable effect on preventing dust production during coal seam excavation. The penetrating radius, the infusing velocity and the dust-preventive effect were systematically studied.

Metallurgy

Design optimization of flow control device for multi-strand tundish

Yanping Bao, BomeiXu, Guolin Liu, Feng Yue, Xinxia Qi

2003, 10(2): 21-24.

中文摘要(277) PDF(12) SpringerLink

摘要:
The fluid flow phenomena in tundish have a strong influence not only on the uniform of composition and temperature of bath, but also on the separation of non-metallic inclusions, especially for the multi-strand tundish. A water model of a multi-strandtundish has been set up based on the Froude number and Reynold number similarity criteria. The effect of dam+weir and baffle on the uniform of composition and temperature of bath for different nozzles has been studied. The residence time distribution curves of the fluid flow were measured by SG800. Comparing the photos of the flow pattern in tundish, the optimum arrangement of baffle+dam was obtained. This new structure is benefit not only to uniform the temperature among different SENs (submerge entry nozzles) but also to separate the non-inclusions from the liquid steel, it can be widely used in multi-strand tundish.

Metallurgy

Assessment of the apparent activation energies for gas/solid reactions-carbonate decomposition

Jianhua Liu, Jiayun Zhang

2003, 10(2): 25-29.

中文摘要(312) PDF(8) SpringerLink

摘要:
The guidelines for assessing the apparent activation energies of gas/solid reactions have been proposed based on the experimental results from literatures. In CO₂ free inlet gas flow, CaCO₃ decomposition between 950 and 1250 K with thin sample layer could be controlled by the interracial chemical reaction with apparent activation energy E = (215±10) kJ/mol and E = (200±10)kJ/mol at T = 813 to 1020 K, respectively. With relatively thick sample layer between 793 and 1273 K, the CaCO₃ decomposition could be controlled by one or more steps involving self-cooling, nucleation, intrinsic diffusion and heat transfer of gases, and E could vary between 147 and l90 kJ/mol. In CO₂ containing inlet gas flow (5%-100% of CO₂), E was determined to be varied from 949 to 2897 kJ/mol. For SrCO₃ and BaCO₃ decompositions controlled by the interfacial chemical reaction, E was (213±15) kJ/mol (1000-1350 K) and (305+15) kJ/mol (1260-1400 K), respectively.

Metallurgy

Morphology, chemical compositions and size distribution of rare earth oxides in pure iron

Shengjun Zhang, Bo Song, Xihua Liu, Qing Lin, Biyan Wang

2003, 10(2): 30-33.

中文摘要(283) PDF(15) SpringerLink

摘要:
The pure iron was melted and deoxidized by metallic Al and rare earth elements La, Ce and Y respectively at 1600℃ in a vertical resistance furnace. The morphology, chemical composition and size distribution of the inclusions in deoxidized liquid iron have been investigated by using of SEM and image-analysis techniques. The investigated results show that the deoxidation products in molten iron are complex inclusions of rare earth oxide or Al₂O₃ combined with FeO finely distributed. The proper holding time and rapid cooling rate can make inclusions finer. La, Y and Al are more effective than Ce for obtaining finely distributed inclusions.

Materials

Application of CX-type modifiers in Al-Si alloys

Shufang Yao, Weimin Mao, Xueyou Zhong, Kaike Cai, Zidong Wang, Lei Mao, Juxiang Yang

2003, 10(2): 34-38.

中文摘要(220) PDF(9) SpringerLink

摘要:
The modification effect of CX-type (CX means the modifiers that have long effective term) modifiers applied in ZL108 and ZL104 Al-Si alloys has been studied in detail. The results show that the morphologies of the eutectic silicon and the primary silicon can be modified and refined simultaneously. The modification effect acts quickly and can maintain a period of 8 h by the CX-type modifiers. The CX-type modifiers increase the mechanical properties of Al-Si alloys and improve the service properties of machine parts made of Al-Si alloys (such as piston and cylinder etc.). In modifying processes, the amount of the addition of CX-type modifiers is smaller than that of any other modifiers, and the modifying procedures are simple. There are no smoke, no dust, and no irritant smell in modifying processes using CX-type modifiers. Therefore, the CX-type modifiers have advantages in economy and environment protection.

Materials

Development of grain boundary allotriomorphic ferrite/granular bainite duplex steel

Pingguang Xu, Bingzhe Bai, Hongsheng Fang, Zhenjia Wang, Jianping Wang, Yongkun Pan

2003, 10(2): 39-44.

中文摘要(280) PDF(14) SpringerLink

摘要:
A new hot-rolled low alloy high strength steel with grain boundary allotriomorphic ferrite/granular bainite duplex micro-structure has been developed through novel microstructure and alloying designs without any noble metal elements such as nickel and molybdenum. Its as-rolled microstructure and mechanical properties, fatigue crack propagation behavior compared with single granular bainitic steel as well as continuous cooling transformation, were investigated in detail. The measured result of CCT (continuous cooling transformation) curve shows that such duplex microstructure can be easily obtained within a wide air-cooling rate range. More importantly, this duplex microstructure has much better combination of toughness and strength than the single granular bainite microstructure. It is found that the grain boundary allotriomorphic ferrite in this duplex microstructure can blunt the mi-crocrack tip, cause fatigue crack propagation route branching and curving, and thus it increases the resistance to fatigue crack propa-gation, improves steel toughness. The mechanical properties of the above commercial duplex steel plates have achieved or exceeded 870 MPa ultimate tensile strength, 570 MPa yield strength, 18% elongation and 34 J Charpy V-notch impact energy at -40℃,showing good development potential.

Materials

Dynamic recrystallization during hot torsion of Al-4Mg alloy

Junpin Lin, Yanli Wang, Zhi Lin, Guoliang Chen

2003, 10(2): 45-48.

中文摘要(282) PDF(11) SpringerLink

摘要:
Binary Al-4Mg alloy have been deformed by hot torsion at 300-500℃ and strain rates of 0,006-1.587 s^-1 to a true strain of 5.5. The specimens were annealed in vacuum for 1.5 h at 500℃ and then water quenched. The study indicates that the dynamic recrystallization occurs during hot torsion of Al-4Mg alloy in a certain range of Z parameter (Zener-Hollmon Parameter), i.e. 19.3 ≤ lnZ ≤ 24.8. Increasing the strain rate at higher deformation temperature or reducing the strain rate at lower deformation temperature accelerates the occurrence of dynamic recrystallization in the alloy.

Materials

Superplastic deformation of commercial OOCr22Ni5Mo3N0.17 duplex stainless steel

Peixue Zhang, Xueping Ren, Jianxin Xie

2003, 10(2): 49-55.

中文摘要(219) PDF(10) SpringerLink

摘要:
The superplastic behavior of a commercial duplex stainless steel has been studied by means of isothermal hot tensile test at temperatures of 850-1050℃ for the initial strain rates ranging from 3×10^-4 s^-1 to 5×10^-2 s^-1. At 960℃, the best superplastic deformation that caused the maximum elongation greater than 840% was obtained for an initial strain rate of 1.2×10^-3 s^-1. At 850℃, the best elongation 500% was achieved for an initial strain rate of 2.5×10^-3 s^-1. During the deformation in higher temperature region,coarse γ grains formed during the prior treatments were broken into spherical particles, resulting in a homogeneous dispersion of γ particles within the δ-ferrite matrix. However, at lower temperatures between 800 and 950℃, the σ phase was formed through the eutectoid decomposition of δ→γ+σ, resulting finally in the stable equiaxed micro-duplex structures with δ/γ and γ/σ, respectively.The precipitation of the σ phase played an important role in improving the superplasticity at 850℃. The strain-rate sensitivity coefficient, m-values, were also determined by the strain rate change tests. The microstructure studies show that the superplastic process occurs mainly by the local work hardening and the subsequent dynamic recrystallization and a grain boundary sliding and grain switching mechanism.

Materials

Origin of the pre-peak in the structure factor of liquid Fe-4.30C-0.21Ce alloy

Xinying Teng, Yifu Ye, Huanrong Wang, Zhiqiang Shi, Guanghui Min, Haowei Wang

2003, 10(2): 56-59.

中文摘要(336) PDF(8) SpringerLink

摘要:
The liquid structure of Fe-4.30C and Fe-4.30C-0.21Ce alloys was studied by high temperature X-ray diffractometer. The results show that for Fe-C alloy the nearest neighbor distance of the eutectic alloy is 0.259-0.260 nm at the temperature range of 1200-1400℃, which increases to 0.269-0.271 nm with the addition of 0.21% (mass fraction) Ce in the Fe-C alloy at the same temperature range. There is a pre-peak at Q = 15.5 nm^-1 on the original intensity curve and structure factor S(Q) of the liquid Fe-4.30C-0.21Ce alloy, which was caused by the Ce atoms in the C-Ce clusters. Combined with the shared face, the tetragonal structure can meet the requirement for the distance of Ce-Ce atoms. It also shows that the cluster size in the liquid Fe-4.30C-0.21Ce alloy in-creases with the decreasing temperature.

Materials

Numerical calculation of temperature and phase change during the process of atomizing spray quenching on drilling pipe

Qitang Li, Guozeng Yang, Jianguo Zhang

2003, 10(2): 60-64.

中文摘要(239) PDF(8) SpringerLink

摘要:
A finite element method (FEM) procedure was developed in order to simulate the quenching process for drilling pipe (DP).The calculating model was based on time-temperature-transformation (TTT) diagrams, and incorporated with material properties dependent on temperature. The procedure was used to calculate the temperature-time histories, describe the phase transformations of atomizing spray quenching for DP in the welding zone, and predict the hardness distribution in radius direction after quenching in the zone. The calculated results met well with that of experiments. It was easy to determine the parameters such as volume and pressure of the cooling water and compressed gas by use of the numerical calculation and experiments, because the value of convection coefficient was decided greatly by the mixture of the cooling water and compressed gas. Moreover, the simulating results were helpful not only to design the quenching equipment, but also to optimize the quenching process for DP's welding zone.

Materials

Thermoelectric properties of BiSb_x (x=0.6-0.8) thermoelectric materials fabricated by different processing

Guiying Xu, Zhangjian Zhou, Sitong Niu, Jianqiang Liu

2003, 10(2): 65-67.

中文摘要(338) PDF(23) SpringerLink

摘要:
In order to improve the thermoelectric properties, hot-pressing sintering and ultra high pressure sintering methods were adopted to fabricate BiSb_x. The phase and crystal structures were determined by X-ray diffraction analysis (XRD). The thermoelectric properties were measured at 303 K along the direction parallel to the pressing direction. The electric conductivity of the samples was measured at 303 K by the four-probe technique. To measure the Seebeck coefficient, heat was applied to the samples placed between two Cu discs. The thermoelectric electromotive force (E) was measured upon applying small temperature differences ( △T<2℃) between the both ends of the samples. The Seebeck coefficient of the samples was determined from the value of E/△T. The results indicate that the thermoelectric properties of the samples fabricated by UHPS (ultra high pressure sintering) method are much higher than that by HPS (hot pressing sintering) method and have the highest values at x=0.7.

Automation

A chaos genetic algorithm for optimizing an artificial neural network of predicting silicon content in hot metal

Deling Zheng, Ruixin Liang, Ying Zhou, Ying Wang

2003, 10(2): 68-71.

中文摘要(316) PDF(17) SpringerLink

摘要:
A genetic algorithm based on the nested intervals chaos search (NICGA) has been given. Because the nested intervals chaos search is introduced into the NICGA to initialize the population and to lead the evolution of the population, the NICGA has the advantages of decreasing the population size, enhancing the local search ability, and improving the computational efficiency and optimization precision. In a multi-layer feed forward neural network model for predicting the silicon content in hot metal, the NICGA was used to optimize the connection weights and threshold values of the neural network to improve the prediction precision. The application results show that the precision of predicting the silicon content has been increased.

Automation

A new method for simulating human emotions

Weimin Xue, Zhiliang Wang, Wenhong Xia, Wenbo Meng

2003, 10(2): 72-74.

中文摘要(295) PDF(13) SpringerLink

摘要:
How to make machines express emotions would be instrumental in establishing a completely new paradigm for man machine interaction. A new method for simulating and assessing artificial psychology has been developed for the research of the emotion robot. The human psychology activity is regarded as a Markov process. An emotion space and psychology model is constructed based on Markov process. The conception of emotion entropy is presented to assess the artificial emotion complexity. The simulating results play up to human psychology activity. This model can also be applied to consumer-friendly human-computer interfaces, and interactive video etc.

Communication

Secure communication by generalized chaotic synchronization

Lequan Min, Xianhua Zhang, Miao Yang

2003, 10(2): 75-78.

中文摘要(218) PDF(10) SpringerLink

摘要:
Chaotic communication is a rather new and active field of research. Although it is expected to have promising advantages,some investigators provide evidences that chaotic communication is not safety. This letter provides a new chaotic secure communication scheme based on a generalized synchronization theory of coupled system. The secret message hidden in the chaotic source signal generated via the scheme is very difficult to be unmasked by so-called nonlinear dynamic forecasting technique. One example for Internet communications was presented to illustrate the security of our scheme.

Communication

Interaction of fatigue and creep of GH33 under multi-axial stress at high temperature

Lianqing Wang, Jianguo Wang, Hongying Wang, Shiping Xu, Deguang Shang

2003, 10(2): 79-80.

中文摘要(296) PDF(18) SpringerLink

摘要:
Low-cycle fatigue experiments of tension-compression, torsion and tension-torsion with holding time were performed.The interaction law of creep and fatigue under multiaxial stress at high temperature was investigated, and the micro-mechanism of equilibrium diagrams was analyzed. A united equation of fatigue life under multiaxial stress was proposed.

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2003年第10卷第2期