International Journal of Minerals, Metallurgy and Materials

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Feasibility Study on Continuous Mining Method in Deep Position of Jinchuan Nickel Mine, China

Meifeng Cai, Lan Qiao, Changhong Li, Shuanghong Wang

2001, 8(2): 81-85.

中文摘要(291) PDF(16) SpringerLink

摘要:
Jinchuan nickel mine is the largest nickel mine in China. Cut-and-fill mining method with high density cementing materials is used in the mine. The original mining design divided the mining operation into two steps. The first step stopped the mining rooms and the second step stopped the pillars. Because the two-step method made big trouble for finally mining pillars and strongly limited the mining speed and production, it was successfully changed to a continuous cut-and-fill method without pillars. However, the mining operation in the mine has been down to 800 m and the mining condition is getting worse and more complicated. Through systematical field investigations and 3-D FEM analysis, it is proved that the mining method without pillars is feasible for mining deeper orebodies in Jinchuan nickel mine.

Mineral

Simulation of Vertical Planetary Mill Based on Virtual Prototyping

Ruitao Li, Mei Fang, Wenming Zhang, Yue Ma

2001, 8(2): 86-90.

中文摘要(294) PDF(9) SpringerLink

摘要:
The mechanical model of vertical planetary mill is set up, whose dynamic and kinetic characteristics are described as well. Based on the analysis of system dynamics of vertical planetary mill, virtual prototyping technology is applied in the simulation of this mill. The development of virtual prototype of equipment, virtual test and optimization of virtual prototype are stated in detail. Some useful conclusions which have theoretical meaning for the manufacturing of vertical planetary mill have been obtained. Furthermore, it is pointed out that virtual prototyping technology shows great advantage and is bound to become a main method of developing product in the future.

Metallurgy

Behavior of Non-metallic Inclusions in Centrifugal Induction Electroslag Castings

Xichun Chen, Jie Fu, Deguang Zhou, Weiguo Xu

2001, 8(2): 91-94.

中文摘要(226) PDF(10) SpringerLink

摘要:
In order to know the behavior of non-metallic inclusions in centrifugal induction electroslag castings (CIESC), non-metallic inclusions in 5CrMnMo and 4Cr5MoSiV1 were qualitatively and quantitatively analyzed. The largest size of inclusions in the casting and the thermodynamic possibility of TiN precipitation in steel were also calculated. The results show that sulfide inclusions are evenly distributed and the content is low. The amount of oxide inclusions in CIESC: 4Cr5MoSiV1 steel is close to the ESR steel and lower than that in the EAF steel, and there are some differences along radial direction. Nitride inclusions are fine and the diameter of the largest one is 3-4 μm. With the increase of the centrifugal machine's rotational speed, the ratio of round inclusions increases and the ratio of sharp inclusions decreases. According to the experiment and the calculation results, it is pointed out that the largest diameter of non-metallic inclusions in the CIESC 4Cr5MoSiV1 casting is only 6.6 mum, and [N%][Ti%] in 4Cr5MoSiV1 steel should be controlled less than 4.4×10^-5 in order to further reduce the amount and size of TiN inclusions.

Metallurgy

Experimental Research for Refractories Used in High-Turbulent-Mixer (HTM)-Reactor

Yanping Bao, H. W Gudenau, O. S. Kweon

2001, 8(2): 95-97.

中文摘要(263) PDF(7) SpringerLink

摘要:
The high turbulent mixer (HTM) process is benefit for improving the quality of iron and steel, but the refractory of the reactor is easy to be eroded by slag and liquid metal at high temperature. Especially for the violent mixing in HTM, refractory can also be impacted by molten metal (iron or steel), so it is very important to study and find out new refractory to meet the demand of HTM. Suitable refractory not only can stand the eroding of slag and liquid metal, but also can reduce the loss of electromagnetic energy. According to the experimental results, the influence of different refractory on electromagnetic force is unconspicuous, the refractory with Al₂O₃-base is better than that with MgO-base for standing the erosion by slag and iron. Al₂O₃-base refractory is more suitable for HTM process.

Metallurgy

Direct Current Electric Arc-Electroslag Ladle Furnace

Ping Wang, Jie Fu, Minsheng Sun, Xiangmao Kong, Zhimin Ma, Meilun Shi, Xingjiang Wang

2001, 8(2): 98-100.

中文摘要(266) PDF(11) SpringerLink

摘要:
In order to solve the high consumption problem of small capacity ladle furnace (LF), the operation principle and control method of the DC are and electroslag heating ladle furnace are introduced. With only one arcing electrode, the distance between the are and the wall of ladle is enlarged, and consequently the consumption of the ladle refractory is decreased. In the invention, a signal electrode is embedded in the refractory lining of the ladle, which contacts directly with the liquid steel and the ladle shell. Two graphite anode ends are submerged in the slag layer. The signal electrode is used as voltage reference during refining process. The electroslag voltage between anode end and liquid steel is applied to control the depth of anode end in the slag layer during the refining process with this ladle furnace.

Metallurgy

Leakage in Mold Slit during Inverse Solidification

Jiongming Zhang, Xinhua Wang, Wanjun Wang

2001, 8(2): 101-104.

中文摘要(218) PDF(7) SpringerLink

摘要:
The liquid steel will be leaked from the slit between the bottom of solidification mold and mother sheet during inversion casting process. By substitution of the actual liquid steel, the Pb-Sn alloy and the numerical simulation can be used to study the fluid flow in the inversion solidification mold, the mother sheet critical speed is determined for preventing the leakage from the slit of bottom. When the mother sheet speed is more than 0.06 m/s, Pb-Sn liquid alloy will not leak from the slit of the mold. Otherwise, the Pb-Sn liquid alloy can leak from the slit of the mold.

Materials

Microstructural Features During Strain Induced Ferrite Transformation in 08 and 20Mn Steels

Ping Yang, Feng-e Cui, Fuming Wang

2001, 8(2): 105-110.

中文摘要(201) PDF(10) SpringerLink

摘要:
The microstructure evolution during strain induced ferrite transformation was followed in thermal-simulation tests of clean 08 and 20Mn steels. The influences of carbon equivalence and initial austenite grain size on ferrite grain refinement and the volume fraction of ferrite during straining were inspected. The results revealed that the accelerating effect of ferrite transformation by strain was increased as the carbon equivalence decreased. However, finer ferrite grains were obtained at higher carbon content. At strain of similar to 1.5 ferrite grains less than 3 μm and 2 μm can be obtained in 08 and 20Mn steels respectively. Whereas the ferrite grain refinement in 08 steel was due to both effects of strain induced transformation and ferrite dynamic recrystallization, that in 20Mn was mainly due to strain induced transformation. Heavy strain can produce fine ferrite grains in coarse austenite grained 08 steel, but it would lead to band microstructure in coarse austenite grained 20Mn.

Materials

Modified HDDR Process for Producing Anisotropic NdFeB Powders

Xubo Liu, Yue Ming, Yaofu Xiao, Qi Zeng, Zhengyi Zhang, Run Wang

2001, 8(2): 111-114.

中文摘要(278) PDF(20) SpringerLink

摘要:
The effect of HDDR (hydrogenation-decomposition-desorption-recombination process) treating conditions on magnetic anisotropy of Nd₁₃Fe_balCo₁₇B₇Ga₁Zr_0.1 powders has been studied. It is found that increasing recombination temperature is effective for magnetic anisotropy formation, but at the cost of reducing the coercive force. The microstructure analysis (TEM) indicates that the NdFeB recombination nucleation takes place markedly during the transition range from decomposition stage to recombination stage, in which both temperature and H₂ pressure change sharply. In order to create a more stable treatment condition for recombination nucleation, a modified HDDR process is established in which the conventional continuous transition range is divided into several stages. The experimental results have proved that such a process can effectively enhance the remanence of the magnet powders with high certainty, while only cause a little reduction in coercivity.

Materials

Microstructure Study on Semi-solid 60Si2Mn during Compressing

Yonglin Kang, Xiongfei Yang, Renbo Song, Weimin Mao, Maosheng Yang

2001, 8(2): 115-118.

中文摘要(252) PDF(12) SpringerLink

摘要:
The microstructure behavior and deformation mechanism of semi-solid 60Si2Mn fabricated by electromagnetic stirring under different deformation conditions during thixoforming are studied by means of Gleeble-1500 thermal-strain-stress simulator. The micro-structure of deformed 60Si2Mn and that of the non-deformed are compared. The results show that the grain size within deformation zone decreases as the amount of deformation increases or deformation temperature decreases, but deformation fate has small effect on grain size when the rate is very low. Besides, there is a critical amount of deformation to reduce grain size. These results offer theoretical and experimental basis for further producing semi-solid material with high melting temperature and direct forming of semi-solid slurry.

Materials

Stability of Ultra-fine Microstructures during Tempering

Shanwu Yang, Chengjia Shang, Xinlai He, Xuemin Wang, Yi Yuan

2001, 8(2): 119-122.

中文摘要(168) PDF(11) SpringerLink

摘要:
The stability of ultra-fine microstructure during tempering at 650 ℃ was investigated on a Nb-containing steel. The steel had undergone 5 passes controlled rolling, then was relaxed (air cooled) to 730 ℃ and cooled in water. The evolution of microstructure was that, in early stage of tempering, no obvious change was detected by means of optical microscopy while dislocation cells were formed inside bainitic laths. With further tempering, bainitic laths started to coalesce in some regions. Finally, polygonal ferrite was formed while hardness decreased dramatically. Some samples taken from the same primary plate were reheated at 930 ℃ for 0.5 h followed by quenching into water before tempering. Despite their lower original hardness, the reheated samples softened Faster during tempering. Ferrite was quickly formed in the reheated samples. These results indicate that the evolution of microstructures towards equilibrium during tempering of the steel is mainly determined by whether dislocations are pinned rather than the dislocation density.

Materials

Effect of Heat Treatment on High Temperature Stress Rupture Strength of Brazing Seam for Nickel-base Superalloy

Junying Zhang, Zhongtai Zhang, Jisheng Sun, Xiaofang Liu, Wei Tian

2001, 8(2): 123-125.

中文摘要(237) PDF(11) SpringerLink

摘要:
In order to enhance the high-temperature stress rupture strength of brazing seam by heat treatment, it was diffusion treated, then solution heat treated, and finally aging treated. The microstructure of brazing seam especially morphology of γ' phase and boride was observed and the strength of brazing seam was measured in this process. The results show that heat treatment can enhance high-temperature stress rupture strength by improving the microstructure of brazing seam. The strength of brazing seam after solution heat treatment decreases in comparison with that only after diffusion treatment while aging treatment after solution heat treatment increases the strength of brazing seam.

Materials

Microstructure Characteristics and Apparent Viscosity of Hypereutectic Al-24%Si Alloy Melt During Semi-solid State Stirring

Yanjun Li, Weimin Mao, Zisheng Zhen, Xueyou Zhong

2001, 8(2): 126-128.

中文摘要(220) PDF(11) SpringerLink

摘要:
The microstructural evolution and apparent viscosity of hypereutectic Al-24%Si alloy during semi-solid state shearing were studied with a Searte type viscometer. When the alloy melt was continuously stirred from 720 ℃ to eutectic temperature, the primary Si crystals were gradually changed from elongated platelets to near-spherical shapes. It was found that some nondendritic α-phase formed when the melt was stirred below 585 ℃. The experiment showed that the semi-solid stirring had strong effect on inhibiting the anisotropic growth of Si crystals during solidification. The apparent viscosity of the alloy melt increased slowly with the decreasing of temperature before the formation of nondendritic α-phase, which caused the dramatic increase of apparent viscosity.

Materials

Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

Chengchang Jia, Xiuhu Guan, Xuekuan Su, Changheng Hou, Shimin Fan, Jun Zhao, Zizhang Xie

2001, 8(2): 129-132.

中文摘要(309) PDF(7) SpringerLink

摘要:
W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.

Materials

Corrosion Fatigue Behavior of Duplex Stainless Steel in 3.5% Sodium Chloride Solution

S. H Abubakir, Yinshun Wu, Baofeng Ding, Jiuqing Li, Bei Cao

2001, 8(2): 133-136.

中文摘要(259) PDF(12) SpringerLink

摘要:
The corrosion fatigue behavior of duplex stainless steel (DSS) was studied at different cyclic stress levels in 3.5%NaCl (mass fraction, so as the follows) solution (pH=7) at 50 ℃. The results showed that DSS was susceptible to pitting corrosion and corrosion fatigue. Both intergranluar corrosion cracking and transgranlular corrosion cracking initiated at the bottom of pitting holes. Furthermore, the corrosion fatigue properties of DSS in 3.5%NaCl solution may be relatived to complex electrochemical and mechanical coupling effects between the three phases (austenite, ferrite and martensite), where martensite and ferrite were anodic in the corrosion cell and could be prone to cracking under certain condition.

Materials

A Novel Electrochemical Oxygen Sensor for Determination of Ultra-low Oxygen Contents in Molten Metal

Jialin Sun, Congjin Jin, Liansheng Li, Yanruo Hong

2001, 8(2): 137-140.

中文摘要(302) PDF(11) SpringerLink

摘要:
A novel electrochemical oxygen sensor has been developed by using Laβ-Al₂O₃ as solid electrolyte and Cr+Cr₂O₃ as reference electrode. The sensor not only can be used as normal oxygen sensor but also as an ultra-low oxygen sensor. Especially, it is very sensitive to measure ultra-low oxygen in molten metal. For estimating the accuracy of Laβ-Al₂O₃ oxygen sensor, two series of oxygen activities in molten iron at different oxygen contents and different temperature were measured by both Laβ-Al₂O₃ oxygen sensor and ZrO₂ oxygen sensor. The theoretical values of oxygen activities in molten iron (3.30%C, in mass fraction) at 1723K and 1745K were also evaluated for comparing the measuring results of two sensors. At last, the error of measurement for Laβ-Al₂O₃ oxygen sensor was discussed too.

Materials

Experimental Investigation on Flow and Drying Characteristics of Impinging Stream Drying

Xiulan Huai, Dengying Liu, Xiaoming Cui, Qun Meng

2001, 8(2): 141-144.

中文摘要(286) PDF(6) SpringerLink

摘要:
Based on the experimental investigation of one-stage semi-circular impinging stream drying, the experiments with the two-stage semi-circular, as well as the vertical and semi-circular combined impinging stream drying were conducted. The variations of system pressure drop, the mean residence time of particles with the mass flow-rate ratio and air velocity etc, were determined. The influences of inlet air temperature, mass flow-rate ratio, initial moisture content of particles and air velocity etc. on drying characteristics were also studied. The results indicate that the vertical and semi-circular combined impinging stream drying can make full use of the advantages of both the vertical and semi-circular impinging stream drying. Reasonable mass flow-rate ratio, air velocity, and higher inlet air temperature should be used for less energy consumption and cost during drying process.

Information

Performance Modeling and Approximate Analysis of Multiserver Multiqueue Systems with Poisson and Self-similar Arrivals

Zhiguang Shan, Chuang Lin, Yang Yang, Yan Wang

2001, 8(2): 145-151.

中文摘要(194) PDF(7) SpringerLink

摘要:
The problem of state space explosion is still ran outstanding challenge in Markovian performance analysis for multiserver multiqueue (MSMQ) systems. The system behavior of a MSMQ system is described using stochastic high-level Petri net (SHLPN) models, and an approximate performance analysis technique is proposed based on decomposition and refinement methods as well as iteration technique. A real MSMQ system, Web-server cluster, is investigated. The performance of an integrated scheme of request dispatching and scheduling is analyzed with both Poisson and self-similar request arrivals. The study shows that the approximate analysis technique significantly reduces the complexity of the model solution and is also efficient for accuracy of numerical results.

Information

Optimization of Fractal Iterated Function System(IFS) with Probability and Fractal Image Generation

Berthe Kya, Yang Yang

2001, 8(2): 152-156.

中文摘要(289) PDF(20) SpringerLink

摘要:
There are several methods for rendering fractal images based on IFS (Iterated Function System) in computer graphic; but one concern of the computer graphic community has been the efficiency rendering algorithms. The invariant measures arising from IFSP (Iterate Function System with Probability) using the probabilistic algorithm are also known as chaos games. The role of these probabilities to generate the image of the attractor has been investigated using a multi-fractal analysis. The conventional choice of probability associated with each set |S| to generate the attractor in least time possible is introduced, then a new method based on the self similarity and multi-fractal analysis is presented. The efficiency of the new method has been proved over the conventional method.

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