Abstract: In the continuous casting process, the tundish is the last container with refractory lining before the molten steel is poured into the mold. The flow characteristics within the tundish has a strong influence on the tundish design, technology operation and the quality of strand. In this paper,the flow behaviour and liquid residence time within the tundish of HCC have been studied by water simulation.As well as some good results for decanting inclusions in the tundish was found during continuous casting.
Abstract: The work roll, with a 610mm diamter and 1700mm length, is a very important comsumptive section in cold rolling mill.High strength and toughness,high and homogeneous hardness are required for it.Ten ton 86CrMoV7 ingot forged into the work roll is producted on F850/10-Ⅱ electroslag fur nace. It has been proved that reasonable process of E.S.R.is a key to get excellent qualites.In order to improve the ingot qualities and practical electroslag remelting, the investigation are carried out on solidification parameters,such as secondary dendritic arm spacing,temperature gradient, local cooling solidification time,and width of mushy zone.In addition, the relationship between the solidification parameters and crystal structures is investigated as well.
Abstract: On the basis of simulating calculation with heat transfer model, and employing the principle of transition in electric circuit,a automatic control model of secondary, cooling in continuous casting is developed in this paper. The feedforward control pattern is applied, and the change curve of the water flowrate during the transitive proce adopts the exponentia form.This model has the advantages of simplicity and better precision. Moreover it has a characteristic of restraining the fluctuation of surface temperature quickly owing to not using any feedbaek informations from the system.Through offline simulation it is proved that the control effect of this dynamic control model is evidently superior to that of any static control.
Abstract: The strain distributions of four kinds of radial forging processes have been simulated by rigid-plastic FEM.Together with the experimental results, the effect of strain distribution to the structure and quality of the forging products has been discussed.And, the necessory condition to obtain high-quality forging product has been presented.
Abstract: The transitions between the forms of the graphite in the unidirectional solidifiction specimens were observed and analysed by means of the Optical microscopy and scanning electron microscopy(SEM).The results indicate that the graphite morphology could transform progressively from a nodular one to c/v one and then to a flake one as the retained Rare-Earth element decresing. This process is a continous one and need not renucleat-ing.The result of electron probe (WDS) analysis indicates that there is an enriched zone of Ce in the growth front of c/v graphite. Moreover, the mutual effection between RE concentration and cooling rate on the morphology was analysed.The result indicates that the raising of thecooling rate is similar to the increase of the RE concentration.
Abstract: The radiation-induced segregation at precipitate-matrix interface in Fe-Cr-Mn austenitic alloy containing W and V was investigated by electron irradiation. The results show that the precipitates are identified as M23C6 type chromium-carbides. Cr, W and V are enriched, but Mn and Ni tend to be depleted at precipitate-matrix interface within grain.The morphology of precipitates occurred to change at and near the grain bou-boundaries, while Cr is depleted at precipitate-matrix interface. The change of solute atom segregation behavior is directly related to segregation mechanisms.Two kinds of segregation phenomena of Cr concentration may be explained by the theory of radiation-induced segregation.
Abstract: The crack growth rates under the condition of fatigue-creep interaction at 650℃ were measured. The results of mesurement indicated that the crack growth rate was controlled by both Kmax and AK. In this case the effective stress indensity factor (Keq) is a suitable parametes describing the behaviour of crack propagation.Keq is equal to the sum of kmax and α'△k, Where α' was assumed as a parameter represented the effect of crack closure, and α' is a function of crack length.
Abstract: The rupture of the Al-Ni-Co magnet steels used aero-engine rotor is investigated with comprehensive analysis.Metallurgical quality analysis of Al-Ni-Co magnet steel shows that the quality of this steel under vacuum casting is better than that steel under atomosphere casting.The reliability n use for the former is secure. A lot of insclusion, such as Al2O3,TiN,i TiS, etc, ar.e formed resulting in the rupture of the alloy at work.
Abstract: In this paper, a new typical digital trigger for DC. motor speed control system with thyristors is introduced.Owing to the simple structure, great of phase-shift, smooth regulating and trigger accuracy, property of the digital trigger in AC-DC-DDC speed control system is very good. Here merely the princip of the basic work, the program scheme and experimental resulte are given briefly.
Abstract: This paper describes an problem of optimality for constraint nonlinear programming with mixed discrete variable. Some of concept and definition is formulated and optimable conditions and convergence is presented. Lastly, application for study of theory is introduced here.
Abstract: The role of rare earth in low carbon manganese (16Mn) steels with ordinary and low sulfur content obtained by ladle injection of SiCa powder has been investigated in industrial scale. It has been shown that elongated MnS inclusion is harmful to the transversal ductility and toughness of the steels. By means of ladle injection of Si-Ca powder or rare earths (RE) additions, its detrimental effect can be alleviated through desulfurization and shape control of sulfides. With the ladle injection of Si-Ca powder, the modification degree of MnS inclusions depends on the ratio of Ca/S in the steel. It has been found that a small amount of RE addition after ladle injection of Si-Ca powber is available to ensure the complete shape control of sulfide in production practice and the ratio of RE/S required in the steel is much less 3 because of the co-existance of Ca in the steel. It has been suggested that the combination of desulfurization and RE addition is one of the efficient approach to obtain great and stable improvement of ductility and toughness of the steel.
Abstract: The pirtial atom strain field of hydrogen in α-Fe was measured and the variation of the strain components with the hydrogen concentration was investigated. The strain components ε1 and ε2 under Boltzmann distri bution are calculated.Hydrogen permeation measurements under tensile and compressive stress were carried out using a special device designed by ourselves, which can easily apply a same tensile and compressive load to a cross specimens.The results show that ε1> 0, ε2<0, i.e. the partial strain field of hydrogen in α-Fe has an intensive tetragonal distortion. The experiment shows also that the apparent strain components decrease with increasing hydrogen concentration.
Abstract: The minute varying mthod which counts theoretical corrective coefficients in x-ay fluorescence analysis is successful. After computing fundamental theoretical corrective coefficients δij, may select proper eliminating terms according to the need, In this paper, the use of the program which is writen by author, computed fundamental theoretical corrective coefficients for glass bead samples, and eliminated two corrective terms of base element and analytical element. The interelement corrective coefficients αij and interoxide Aij were obtained. Finally the better analytical results for 6 kinds of ore samples were obtained by applying theoretical corrective coefficients and using JIS model in refference standard method.
Abstract: In the paper, the spinning parameters of pitches from petroleum residues for manufacturing carbon fiber is investigated. The effects of the spinning temperature, pressure, speed and the pitch's structures and properties to spinning quality are discussed. The method of choosing the best spinning temperature with controlling melt viscosity at about 10 Pa·s, and the ability of enhancing the pitch's spinnability with raising spinning pressure are suggested.
Abstract: Oxidation kinetics of siliconmonocrystal have been studied. The three steps rule of gas-solid reaction have been raised. The reaction rate of oxidation is divided into three stages:in the initial period the reaction rate is controlled by interface chemical reaction; in the second stage by both interface chemical reaction and slow diffusion due to stress; in the third stage by diffusion.And the microstructure of oxide film have been observed by SEM and TEM.
Abstract: A method based on least squares regression analysis has been proposed for the optimization of available thermodynamic properties and phase diagrams of binary systems.By using of this method, the excess entropy of binary system can be predicted from the phase diagram. Eight binary chloride systems were chosen for the study. LiCl-KCl, NaCl-SrCh, NaCl-CaCl2, NaCl-BaCl2, KCl-BaCl2, CaCl2-BaCl2, BaCl2-SrCl2. The thermodynamic properties, which were expressed in mathematical form by critical analysis of all available phase diagrams and thermodynamic data, of all phases in the above binary systems have been obtained.In the same time, the phase diagram and other thermodynamic data can be critically assessed in a thermodynam.ically self-consistent manner.
Abstract: The potential-pH diagram for Sb-H2O system at 100, 150, 200 C have been made using the available thermodynamic data, based on the criss & Cobble correspondence principle. The results obtained in the present study indicate that the stable region of antimony contracts and migrates towards more negative potential and lower pH especially within the alkali region when the temperature increases. As contrasted with the enlargment of the region referred to the ions of SbO2- and SbO2-, the region in which the antimony oxides of Sb2O3 and Sb2O5 are stable contracts as well with temperature because the stability of antimony ions increases with temperature. Eventually, the possibility for application of antimony coating to protecting steels from corrosion has been discussed with the diagram obtained in our study.
Abstract: A Bordoni-type system is used to measure internal friction and modulus of Fe-Ni based metallic glass during structural relaxation.Particularly,the changes in modulus have been studied in details at low temperature below 500K. The results show that the structural relaxation against temperature may be divided into two steps:the low or high temperature structural relaxation is governed by TSRO or by both CSRO and TSRO. The activation energy of low temperature structural relaxation is about 17kJ/mol.
Abstract: In this paper the geometrical parameters to icosahedron and orthopen-tagnal dodecahedron are obtained.Two kinds of 3-dimension quasicrystal lattices are discussed. A new kind of lattices with the characters of or-thopentaqnal dodecahedron is given.By the geometrical parameters,otherkinds of 3-dimension quasicrystal will be dealt with.
Abstract: The corrosion behavior and mechanism of 00Cr25Ni22Mo2N superpure austenitic stainless steel in urea processing environment was studied using metallography, SEM, TEM, SIMS and AES techniques. The results show that the gas extraction tube made of non-sensitized 00Cr25Ni-22Mo2N steel suffered intergranular corrosion. Corrosive media penetrated not only into the tube wall through grain boundaries but also expan ded from the boundary towards the inside of the grain. Therefore, funnel shape penetration paths were formed, which were wider but less deep than common intergranular corrosion of sensitized stainless steel. Neither depletion of chromium nor precipitates were found at the grain-boundary. However, phosphor (and silicon) was segregated at grain boundaries to a great extent. Semiquantitative calculation indicates that phosphor content at the grain boundary is about 25wt%, three orders of magnitude higher than the content whithin the grain. The authors suggest that the potential difference between the grain and its boundary due to the segregation resulted in the observed intergranular corrosion.
Monthly, started in 1955 Supervising institution：Ministry of Education Sponsoring Institution：University of Science and Technology Beijing Editorial office：Editorial Department of Chinese Journal of Engineering Publisher：Science Press Chairperson：Ren-shu Yang Editor-in-Chief：Ai-xiang Wu ISSN 2095-9389CN 2095-9389
