Abstract: With an emergency response system for mines as the object, the effectiveness and efficiency of sudden accident disposal were analyzed from six aspects including routine work, emergency response organizations, emergency plans and training, emergency rescue actions, emergency resources and equipment, and on-site removal and recovery, based on which evaluation indexes in the emergency response system were built up. A multi-attribute Shepard evaluation method was put forward by qualitative and quantitative methods on the base of the complex characteristics of evaluation index attributes in the emergency response system. The construction of an emergency response system for Chengchao Iron Ore of WISCO as an example verified the rationality and practicality of the method.
Abstract: A mathematical model of flow characterization in multi-strand continuous casting tundishes was attempted to put forward, the standard of plotting residual time distribution (RTD) curves was definitely presented and a relative calculation method was proposed. The feature of dead region was carefully studied and. a method to calculate its volume fraction was given in the model. What' s more, the model considers bypass flow and proposes a method to calculate its volume fraction. Experimental results show that this new model can better capture the difference between the reality flow pattern and the ideal plug flow pattern and reflects the feature of plug flow.
Abstract: A mathematical simulation of flow field in the vacuum chamber and ladle during RH degassing was carried out in combination with the RH refining equipment of a steel company. Based on the simulation results some phenomenon during degassing operation can be explained. Proved by the formula and data obtained from the practice the simulation result is reliable. Finally, the model was used to calculate the turbulent dissipation rate field and the relation of circulation flow rate in the RH device with the quantity of Ar blowing, and the optimum quantity of gas blowing for the RH refining process was suggested.
Abstract: The motion behavior of Al2O3 nano-particles with a size of 20 to 40 nm in high temperature liquid iron was studied. The results showed that after the nano-particles were kept on for 60 min in liquid iron, their size was still 20 to 60 nm; moreover, they did not become micro-particles and disperse better in liquid iron. The motion behavior of the nano-particles in liquid iron was described by the Brown theory. It is indicated that the phenomena of collision, reuniting and agglomeration of the nano-particles do not occur in liquid iron, and the motion behavior of the nano-particles described by the Brown theory is consistent with experiment results. The motion behavior of Al2O3 nano-particles is in contrast with usual Al2O3 non-metallic inclusions in liquid steel.
Abstract: Based on the coexistence theory of steel slag structure and the programming theory, a mathematical model revealing the relationship between inclusions and molten steel composition in a continuous casting mold was developed with the aim to minimize the free energy change of the reaction between inclusions and liquid steel. It is verified by the experiment that results calculated with the model are agreement with the experimental ones well when the inclusions are in liquid state. The effects of[Ca] and[Al] contents in liquid steel oh the inclusion components were discussed and the results show that[Al] content should be changed with[Ca] content in liquid steel in order to acquire deformable inclusions in tire cord steel. When the mass fraction of[Ca] in liquid steel is 5 ×1010-6, the mass fraction of[Al] should be controlled around 12 ×10-6.
Abstract: The effects of mechanical alloying parameters, including milling rate and milling time, on the microstructural properties of the as-milled powders were investigated. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the best milling efficiency could be obtained at a milling speed of 380 r·min-1 while the grain size of the powder decreased remarkably without obvious particle agglomeration. Peak broadening in the XRD patterns occurred due to the decrease in grain size and mean particle size during mechanical alloying. The particle size decreased with increased milling time and after 30 h milling, the particles were nearly spherical shape with a uniform mean size of 13.4μm. SEM-EDS analysis of the particle cross section surface showed that all alloying elements distributed homogeneously.
Abstract: To research the resistance of China low activation martensitic (CLAM) steel to irradiation swelling, the microstructure of CLAM steel irradiated by high energy elections at 450℃ was in-situ observed on a high voltage electron microscope. The results indicate that a lot of voids and dislocation loops form by irradiation. The dependence of the amount and size of these damages on the irradiation dose are evaluated and discussed. The irradiation swelling is about 0.26% and thus CLAM steel is considered as a material with high resistance to swelling.
Abstract: Initial corrosion behaviors of three low alloy steels in simulative marine atmosphere were analyzed by optical microscopy along with electrochemical impedance spectra. It is found that the microstructures of the steels not only affect the initial corrosion behaviors directly, but also influence the long term corrosion behavior indirectly. In the early stages of corrosion, large-angle boundaries in ferrite are easy to be corroded, on the contrary, low-angle boundaries in bainite are difficult to be corroded, while preferential etching in ferrite + pearlite steel always concentrates on pearlite phase and its boundaries. The corrosion resistance of bare samples of ferritic steel is fairly good, whereas the resistance increment of rust layer formed on the steel is little when prolong the test. However, the resistance increment of rust layers formed on bainitic steel and ferrite + pearlite steel is large when prolong the test, which means the steels will have good corrosion resistance in a long term, despite of their lower resistances of bare steel. The results indicate that, by proper alloying, bainitic steel can become a potential candidate for a new type of low cost and high strength weathering steel.
Abstract: Macrotextures of a semi-processed non-oriented silicon steel were measured in the production process from hot rolling (with the finish rolling temperature below Ar1) to final stress relief annealing, and the texture evolution were analyzed in the form of orientation distribution function. It was found that the main component in the surface layer of a hot rolled strip was {111}plane texture resulting from ferritic recrystallization; while shear texture and rolling texture were dominant at the center and at the 1/4 thickness of the strip. After cold rolling, the texture components at the center and in the surface were similar. The fractions of {111}, {112} and {00} plane textures all increased, particularly {111} component was intensified most significantly. After softening annealing, the fractions of {001}〈110〉 and {112} 〈110〉 components both decreased rapidly and T fiber emerged as the dominant component. When the primarily annealed strip was subjected to temper rolling and subsequent stress relief annealing, the unfavorable { 111} plane texture diminished while the GOSS component increased distinctly. Such experimental results could be explained by the calculated Taylor factor distribution since Taylor factors quantitatively linked deformation stored energy in grains to orientations of the grains.
Abstract: In order to meet energy conservation, consumption reduction and high quality, the full-processed non-oriented electrical steel 50W800 was successfully developed and produced in batch by a production flow of BOF steel-making, RH degassing, ladle furnace (LF) refining, compact strip production (CSP) line, cold rolling and continuous annealing. By testing, the magnetic properties of 50W800 are excellent:the iron-loss (P1.5/50 is less than 4.6 W·kg-1, the magnetic induction (B50) is more than 1.71 T, the flatness and surface quality of products are fine, and the coating has the satisfied properties of insulation and corrosion resistance. The products are suitable for the motor manufacture industry.
Abstract: An investigation on the effect of Ce on the solidification structure of an Fe-Ni base Invar expansion alloy shows that great amount of high-melting compounds (Ce2O3) with a size of 2.0 μm form in the alloy after Ce addition. Based on the theory of lattice misfit, the lattice misfit of low-index surfaces between Ce2O3 and the alloy is 7.1%, which is relatively low; with Ce2O3 as heterogeneous nucleation, therefore, the solidification structure of the alloy changes from complete dendrite grains to complete equiaxed grains. There are Ce2O3, Ce2O2S and CeS in the interface of equiaxed grains, which prevent from the growth of crystal grains.
Abstract: On the basis of the rapid growth model for dendrite and eutectic and the criterion of the highest temperature for interface growth, an interface response function (IRF) of eutectic alloys during rapid equiaxed solidification was established. With the IRF, competitive growth between the primary and eutectic phases of Al-Si alloys was investigated and a microstructure selection map of Al-Si alloys during non-equilibrium solidification was constructed. The calculation results show a good agreement with those of atomization experiments, indicating that the IRF model can be used to predict satisfactorily the microstructure selection and evolution of Al-Si alloys.
Abstract: Scanning Kelvin probe (SKP) and localized electrochemical impedance spectroscopy (LEIS) were employed to investigate the corrosion process and electrochemical behavior of 2A12 aluminium alloy during the initial corrosion period. It is shown that Cl- accelerates the atmospheric corrosion of 2A12 aluminum alloy and pitting expands with exposure time during the initial stage. SKP results indicated that anodic and cathodic areas on the surface changed constantly with distinct characters of localized corrosion in the initial corrosion period. When the corrosion process continued, the surface potential of 2A12 aluminium alloy moved positively, while the anodic and cathodic fields distinguished evidently from each other. LEIS results showed that the surface localized electrochemical impedance in the initial stage increased with time, but distributed dispersively. During the initial stage of the corrosion process, corrosion products formed on the surface of 2A12 aluminium alloy constantly, which could restrict the corrosion process.
Abstract: An experimental study was presented to evaluate the microstructures and reliability of solder joints between Sn-2.5Ag2.0Ni solder and various Ni plating layers. Ni(P)/Ni(B) and Ni(P)/Ni double layers were used to deposit on SiCp/Al composites. The high reaction rate between Ni(B) layer and SnAgNi solder leaded to the highest growth rate of intermetallic compound (IMC) Ni3Sn4. The shear strength of solder joints with Ni(P)/Ni layer is higher than that of solder joints with Ni(P)/Ni(B) layer at the initial stage of aging, but lower than that after 250 h aging.Intermetallic layer growth and crack formation are the major reasons of failure for a SnAgNi/Ni/Ni(P) solder joint. While the failure of a SnAgNi/Ni(B)/Ni(P) solder joint is caused by the formation of holes between Ni(P) and SiCp/Al composites, which result from directional diffusion of Ni toward solder.
Abstract: A (Bi0.5Na0.5)TiO3-based lead-free piezoelectric ceramic, (1-x-y)Bi0.5Na0.5TiO3-xBi0.5K0.5TiO3-yBiCrO3(BNT-BKT-BC-x/y), was prepared by a conventional ceramic sintering technique. Its crystal structure, and piezoelectric properties and depolarization temperature were investigated. The morphotropic phase boundary (MPB) of the system between rhombohedral and tetragonal locates in the range of x=0.18 to 0.21 and y=0 to 0.02. Moreover, an obvious second phase was observed in the samples with y=0. 025 and x=0.18. The optimum piezoelectric properties were obtained near the MPB composition, and the piezoelectric constant d33 and the electromechanical coupling factor kp of the ceramics attain the maximum values of 168 pC·N-1 and 0. 326 at x=0.18, y=0.015 and at x=0.18, y=0.01, respectively. The depolarization temperatures confirmed by kp and θmax are almost identical. The depolarization temperature keeps decreasing with an increase content of BC and first increases and then decreases with an increase content of BKT.
Abstract: A simplified geometrical model of high porosity open-cell metal foams was constructed. A related expression of effective thermal conductivity of the metal foams was derived on the base of the analogy between thermal and electrical resistance at the scale of unit pore. The correlation was further modified by existing experimental data. In addition, convective heat transfer was numerically simulated for air flow in a metal-foam filled three-dimensional rectangular duct. The simulation results were analyzed and compared with experimental data. It is shown that the calibrated effective thermal conductivity model is applicable for aluminium metal foams. Under the condition of the same porosity, the convective heat transfer of forced flow in the duct is enhanced by using higher porosity (i. e. smaller pore size) metal foams, but at the expense of a higher pressure drop. To some extent, metal foams with a lower pore density have a better overall performance on convective heat transfer.
Abstract: A improved equipment was designed to test the apparent viscosity of semisolid alloy slurry since many shortcomings appeared in previous devices. Measurements based on the theoretic calculation formula were taken, all components were reasonably assembled, and accurate and stable testing was conducted. The semisolid alloy is prevented to be oxidized, high solid fraction alloy is able to deal with, and semisolid alloy samples can be obtained conveniently. Apparent viscosity testing and metallurgical structure analysis for the samples indicate that the rheological behavior and morphology evolution of semisolid alloy can be effectively investigated by this equipment.
Abstract: A model to analyze forces on deadman in a hearth under a special condition was constructed and a method to calculate the minimum depth of salamander was put forward. Proved by data from a dissected blast furnace (BF), the calculation method was perfect. On the base of the former model, a new model for deadman force analysis on the general condition was built, a reliable formula to estimate the height of deadman floating was deduced, and the relationship between deadman floating height and liquid slag surface was discussed.
Abstract: A numerical calculation method of finite element coupling field was used to simulate the cooling process of big bars. The influential rule of cooling water flow on the cooling effect was obtained by analyzing the numerical result. Moreover, the influence degrees of two factors, the sectional area of the cooler's inlet port and the velocity of cooling water, were compared. The results show that when the cooling water flow is relative small, its change has significantly influence on cooling effect; but when the cooling water flow is relative large, the difference in cooling effect is inappreciable. In addition, the cooling water velocity has a larger influence on cooling effect than the sectional area of the cooler's inlet port.
Abstract: This paper proposed a flatness feed-forward control method based on the on-line measured data of strip profiles at the entrance and constructed a flatness predictive control model for tandem cold rolling mills, the correctness of which was verified by comparing with actual values. On the base of studies on the flatness feed-forward control strategy and the flatness feed-forward control model, a complete set of flatness feed-forward control models and the corresponding off-line simulation system were established for a 1550UCMW tandem cold rolling mill equipped with a profile instrument at the entrance. Simulation results showed that when the flatness feed-forward control model was used, finishing strip flatness fluctuation caused by the variation of incoming strip profiles weakened obviously, leading to further improvement in the quality of finishing strip flatness.
Abstract: A planetary wheel running mechanism was designed to adapt to the store environment of complex terrain and changeable geology of the cobalt and hydrothermal sulfide investigation area in the deep-sea bed. A dynamic model of obstacles for the planetary wheel running mechanism was established based on the virtual work principle. The structural characteristics of the planetary wheel running mechanism were derived by analyzing obstacle height effect factors with a transmission ratio of 1:2.25. The obstacle (the altitude of 900 mm) process for both sides of a planetary gear train was analyzed in ADAMAS. It is proved that the physical dimension of the planetary gear train, bodywork center position and attachment coefficient are the key effect factors. The driven moment, velocity and normal pressure sharply increased as each wheel surmounting obstacles, but they were moderate after the front wheel came over the obstacles. Another weaker pulse occurred when the rear wheel began climbing, and then the parameters reached a plateau. This mechanism transforms between an ordinary gear train and a planetary gear train, and it has good autonomous obstacle performance.
Abstract: An integrated operation planning optimization model for special furnace charge mode, which is a puzzle of integrated planning in iron and steel enterprises, was introduced. The model was solved by a multistep optimization method based on combining optimization and simple simulation. With given process parameters for simulation, an optimized and integrated operation planning and the operating time for hot and cold slabs can be presented rapidly by the optimization method. The result optimized by the model meets the actual demand, and the operation planning is feasible and operable.
Abstract: According to the fact that a common method for product quality modeling has not very high modeling accuracy and its prediction intervals can not be given, a model of product quality based on wavelet relevance vector machine was proposed. The simulation data and the real field data of zinc coating mass from strip hot-dip galvanizing were used for validation. The results show that the model based on wavelet relevance vector machine has a higher prediction precision than those based support vector machine and relevance vector machine, and its prediction intervals can he given. The zinc coating mass forecasting model based on wavelet relevance vector machine for multi-group data has an average of the relative prediction error of 4.52%; thus for the quality control, it provides the necessary decision supports and analysis tools.
Abstract: An approach of high-power super high-speed doubly-fed variable frequency drive and its application system were presented. Based on a discrete mathematical model of doubly-fed induction machines, high capacity convertors, and engineering vector space computation, an algorithm simulation platform was constructed in SIMCAD of PSIM6.0. The application system of a 6500 MW shock generator was set up on the basis of the simulation results. Its experiment results showed that the current's overshooting was small, the exciting component and torque component were independent, and the dynamic flux was smooth. The simulation and experiment results are in agreement demonstrating the validity of the model. It is also found that the static and dynamic performances of the application system are similar to those of DC drives.
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
