Abstract: In order to determine the suitable concentration of paste for industrial application, a further development of paste definition was proposed from the viewpoint of yield stress. The slurry saturation concentration is defined at the yield stress of (200 ±25) Pa. The suitable concentration of paste for industrial application is the slurry concentration range at the saturation ratio of 101.5% to 105.3% by back-stepping. Two tailings samples (named as Tailings 1 and 2) from different mines were used to testify the paste definition. Tailing 1 was used in laboratory experiment and Tailing 2 for engineering verification. The results show that the maximum concentration of Tailing 1 is 73.71% by indoor dynamic consolidation experiment, and the maximum concentration of theoretic prediction by the paste definition is 73.89%, which has the difference of 0.18% compared with the laboratory experiment. The maximum underflow concentration of Tailing 2 can reach 68% by a deep cone thickener of some mine, and the maximum concentration is 68.97% by prediction of the paste definition, a 0.97% discrepancy in comparison with the underflow of the actual thickener. Hence, the paste definition proposed in the paper has high reliability for predicting the concentration of paste.
Abstract: To solve the problem of Fe(CN)64- causing "iron poisoning" when cyanide-bearing waster water was treated with an ion exchange method, the adsorption properties of Fe(CN)64- onto 201×7 resin were studied by using the Freundlich adsorption equation, the Langmuir adsorption equation, the pseudo-second order equation and the Fan Shan Yang model from thermodynamics and dynamics. The related thermodynamic constant and the apparent activation energy were calculated. The results show that Fe(CN)64- adsorption onto the resin can occur spontaneously. The process conforms to the Langmuir equation and the pseudo-second order equation. It is controlled by film diffusion at the initial stage, but by gap diffusion at the later stage. Fe(CN)64- exchanging to the stern layer is fixed by resin functional groups strongly leading to "iron poisoning" of the resin for generating Zn2Fe(CN)6 and Cu2Fe(CN)6 which adhere on the resin during the process of cyanides removed from the loaded resin with H2SO4. Fe(CN)64- in cyanide-bearing waster water can be removed by selective precipitation.
Abstract: A method of phosphorus removal was proposed to process oolitic high-phosphorus iron ore. It is an integration of direct reduction and melting separation with carbon-containing pellets prepared with high-reactivity biomass char. Direct reduction experiments were performed in a tubular furnace, and three parameters were investigated, i. e., reduction temperature, biomass char adding ratio (carbon-to-oxygen molar ratio) and atmospheres. The optimum condition was determined to be the reduction temperature of 1373 K, the biomass adding ratio of 0.9, the PCO2/PCO value of 1:1, and the reduction time of 15 to 25 min. Under this condition, the metallization rate and the residual carbon content of reduced samples are 75% to 80% and 0.69% to 0.11%, respectively. SEM-EDS and XRD examination of reduced samples obtained under the optimum condition shows that the major phases are metallic iron, calcium silicate and calcium phosphate, but phosphorus still remains in gangue. Subsequent melting separation experiments were conducted in a Si-Mo high-temperature furnace. Metal with the phosphorus content of some 0.4% was obtained from the reduced samples;and furthermore, metal with the phosphorus content of less than 0.3% could be obtained after introducing 2% to 4% Na2CO3 into the melting system. Based on the above analysis, the feasibility of applying biomass char for phosphorus removal is demonstrated.
Abstract: Multi-component metal powders were prepared by imitating the crushed metal enrichment originated from waste printed circuit boards. The effects of smelting temperature, smelting time and NaNO3-NaOH/powder mass ratio on the extracting ratios of amphoteric metals during low-temperature alkaline smelting were investigated through single-factor experiments and orthogonal tests. It is found that the mass ratio of NaNO3-NaOH to crushed metal enrichment has the most significant effect on the extracting ratios of amphoteric metals. The optimum conditions were obtained as the smelting temperature of 400℃, the smelting time of 1.5 h and the mass ratio of NaNO3-NaOH to crushed metal enrichment of 3.5. Under the optimum conditions, the extracting ratios of amphoteric metals are as the following:Sn 83.6%, Al 92.7%, Zn 80.9%, and Sb 34.5%. Amphoteric metals are converted to sodium salts, dissolving in the leaching process, while other components, such as copper and precious metals, are enriched in the residue. In this novel process, amphoteric metals are separated with other metals efficiently.
Abstract: The effect of ladle change process (the 4th heat to the 5th heat) on the surface cleanliness of IF steel continuous casting slabs was investigated by total oxygen measurement and automatic feature analysis equipped on ASPEX. A comparison of surface cleanliness was performed between transition slabs (cast during ladle change process) and normal slabs (cast under normal condition). It is found that inclusions larger than 20μm are classified into three types:(1) cluster alumina (including bubble + cluster alumina inclusions);(2) cluster TiOx-Al2O3 inclusions; and (3) mold powder inclusions. In terms of surface inclusions in normal slabs, most of the inclusions detected in the scanning area are cluster alumina, and no mold powder inclusions are found. While for transition slabs, the total oxygen content increases from 14×10-6 to 17×10-6, and the number density of Type 2 inclusions goes up since the cast start of the 5th heat, indicating re-oxidation of the steel melt during ladle change process. Furthermore, level fluctuation in the mold is also severe since the cast start of the 5th heat, leading to mold powder entrapments. The affected length of cast slabs during ladle change process is about 11 m under the present casting condition.
Abstract: To reduce shrinkage cavity defects in Fe-Ni alloy ingots,a numerical simulation model was established by using the finite element software ProCAST. The simulation parameters were verified by anatomical experiment. The effect of molding parameters on porosity distribution in Fe-Ni alloy ingots was investigated and an optimized ingot was obtained. It is found that the parameter setting of heat transfer under vacuum circumstance is relatively reasonable,and the simulation results produce a good fit...
Abstract: The characteristics of precipitates in H13 steel under three different states, i. e., annealed electroslag remelting (ESR), annealing and tempering, were studied by means of carbon extraction replica technique, transmission electron microscopy, electron diffraction and energy dispersive spectroscopy. It is observed that these precipitates is composed of square-shaped ones, roundshaped ones and irregular ones below 200 nm in size, which are defined as V8C7, Cr23C6 and Cr3C2 (Cr2VC2), respectively. The evolution of these precipitates was analyzed, and thermodynamic calculations of precipitation were performed in the liquid phase region, the liquid-solid phase region and the solid phase region. Thermodynamic calculation and transmission electron microscopy results show that Cr23C6 and V8C7 cannot precipitate in both the liquid phase region and the liquid-solid phase region, but they start to precipitate only when cooling to the solid phase.
Abstract: Inclusions in free cutting steel such as BN, MnS, Al2O3 and TiN were characterized by nanoindentation. The improvement of BN inclusions on the machinability of the steel was discussed. The error between nanoindentation and macrohardness measurement was analyzed. The hardness of BN inclusions in as-cast samples is lower than that of MnS inclusions, but BN inclusions after forging become harder than MnS, even though these three kinds of inclusions are far softer than the based metal. BN inclusions in as-cast samples and forged samples are stress concentration sources, lubricants and enclose hard particles, therefore improve the machinability of the steel. Nanoindentation characterization and macrohardness measurement have certain error.
Abstract: The precipitated phase behavior, microstructure characteristics and static recrystallization mechanisms of FGH98 alloy in extruding and annealing states were systematically investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A portion of recrystallized grains were observed in as-extruded samples during the cooling process, and the dislocation density decreases with the increasing of deformation temperature. The recrystallization mechanism of FGH98 alloy during the annealing process is mainly dominated by residual primary γ' phase. In the region with a more content of residual primary γ' phase, static recrystallization is controlled by the coalescence and growth of subgrains;when residual primary γ' phase in the alloy decreases, many nucleation mechanisms of static recrystallization may occur, such as strain-induced boundary migration (SIBM), nucleation in the juncture of several grains, and twins superposition nucleation. It must be pointed out that residual primary γ' phase in the alloy can also be softened to somewhat extent by recovery and recrystallization during the annealing process.
Abstract: Tension and cyclic deformation tests of a nearly lamellar Ti-45Al-8Nb-0.2W-0.2B-0.1Y alloy were carried out at 750℃, and the corresponding microstructures were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It is found that the cyclic stress-strain curve of the alloy at 750℃ is above the static tensile curve, indicating an obvious cyclic hardening characteristic of the alloy at 750℃;the cyclic stress-strain behavior of the alloy is characterized by first hardening and then stabilization. TEM observations show that there are lots of dislocation pile-ups, pinnings and tanglings in cyclic deformation and tensile specimens, but large amounts of mechanical twinnings only occur in the former, implying that twinnings play a considerable role in the cyclic deformation process of the alloy at 750℃.
Abstract: Globularization of lamellar α phase was stated by the grain boundary separating model. It was elucidated that globularization of secondary (lamellar) αphase in the transformed microstructure is the main flow softening mechanism of TA15 titanium alloy. A unified viscoplastic constitutive equation of TA15 titanium alloy was developed based on the globularization mechanism. Some physical variables including globularization of secondary (lamellar) αphase, normalized dislocation density, isotropic hardening, plastic deformation induced temperature rise, and phase transformation during deformation were comprehensively considered in the constitutive model. Material constants in the constitutive model were determined and optimized by a genetic algorithm. The constitutive model can accurately predict the flow stress of TA15 titanium alloy in hot deformation.
Abstract: High quality graphene material was prepared from flake graphite by chemical oxidation-reduction process. Its microstructure, morphology, surface properties and supercapacitive performance were characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brumauer-Emmett-Teller (BET) analysis, galvanostatic charge/discharge test, cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). XRD results show that the crystal structure of the graphene is amorphous. SEM and TEM images show that the graphene plays flake-like shapes with wrinkles and ripples. Moreover, the graphene has porous structure with a BET specific surface area of 14.2 m2·g-1, total pore volume of 0.06 cm3·g-1, and average pore diameter of 17.3 nm. EIS results show that the graphene electrode has a smaller impedance, the equivalent series resistance is 0.16 Ω, and the charge transfer resistance is 0.55 Ω. Galvanostatic charge/discharge test and CV analysis indicate that the graphene exhibits enhanced capacitance, high current charge/discharge characteristics, and stable cycle life as a supercapacitor electrode. It delivers the discharge specific capacities of 123, 113, 101 and 89 F·g-1 at the scan rates of 2, 5, 10, and 20 mV·s-1, respectively. Even though the scan rate is 50 mV·s-1, the discharge specific capacity retains 69 F·g-1.
Abstract: Binary colloidal crystals were fabricated by a vertical deposition method with two sub-micrometer size polystyrene (PS) microspheres. The self-assembled patterns of binary colloidal crystals (bCCs) were investigated by varying the size ratio, the mass ratio of PS microspheres, the temperature and content of ethylene glycol in water. It is found that PS binary colloidal crystals with face-centered cube (fcc) arrangement can be obtained while the size ratio is more than 4.45 and the mass ratio is not less that 74:26. High-quality PS binary colloidal crystals are easily generated at the temperature of 60℃ and the mass fraction of ethylene glycol in dispersing medium of 6%. The study also shows that self-assembly of two PS microspheres on the substrate surface is operated at the same time, and in this regard the vertical deposition method has a great deal of difference from other methods. In addition, PS binary colloidal crystals have a higher quality with the increase of matching between Brownian motion, sedimentation rate of PS colloidal microspheres in water, and self-assembly rate on the substrate surface.
Abstract: It is emergent to develop new ceramic (glass) matrix composites for modern electronic packaging. Based on copper plating and controlled oxidation of Ti-coated diamond particles, diamond-reinforced glass matrix composites were successfully synthesized by spark plasma sintering (SPS). Their micro-morphology, interface bonding condition, thermal conductivity, and coefficient of thermal expansion (CTE) were investigated. The results show that the composites have uniform microstructure, and the Ti/diamond interface is the weakest in the composites. The thermal conductivity of the composites increases with increasing diamond particle size and content, but the CTE of the composites decreases with increasing diamond content. When the diamond particle size is 100μm and the diamond volume content is 70%, the composite has the highest thermal conductivity about 40.2 W·m-1·K-1 and CTE about 3.3×10 -6 K-1,which can meet the requirement of electronic packaging.
Abstract: To realize the visualization of mould processes and to assist the breakout prediction technology, a contour region filling method was proposed to plot an intuitive on-line thermal map of a mould quickly and efficiently. This method uses discrete data gridding, contour line generating and contour polygon filling to plot the nephogram. A combination of the grid sequence method with the cell subdivision method is adopted for contour line generating, which is more efficient, accurate and simple because of avoiding the contour line tracking and ambiguity. The method was compared with the scan parent element method. The results indicate that the former can plot the nephogram rapidly, ensure its precision and quality, so is better than the latter. Algorithm complexity analysis also proves that the time efficiency of the former is higher. Practical application results show that the on-line thermal map based on the method can reflect the temperature field characteristics of the mould in normal and abnormal conditions well, and is satisfactory for the process of practical production.
Abstract: The forming process of no-step-end workpieces was simulated with the software DEFORM-3D. The influence of processing parameters on the end scrap of no-step-end workpieces was analyzed by means of quadratic quadrature rotate combination design method to get a regression equation. According to the obtained research results, the end scrap is in direct proportion to the length of blanks, but in inverse proportion to the spreading angle. A smaller spreading angle is beneficial under the selected range. Finally the reliability of the regression equation and the correctness of the influence rules were verified by rolling experiment.
Abstract: Based on platforms including VC#. net, SQL Server 2008 and geographic information systems (GIS), the mine map was developed with geographical attributes. A rescue system based on refuge chambers during the mine fire period was constructed after the graphics library, database, method library and knowledge base were established. Due to real time simulation of mine fire, analysis and prediction of its dynamic trend, the rescue system achieved a dynamic visual display of fire plume spreading and the optimal escape route based on refuge chambers in an underground coal mine. At the same time, roadway safety and traffic efficiency were introduced to amend the traffic capacity of post-disaster roadways. The principles for selecting the optimal rescue route based on refuge chambers were determined, and the "ideal-viable-escape" level of escape routes was divided. Since the optimal escape route was calculated using Dijkstra algorithm which was improved by the stack data structure, the computing speed of the rescue system online increased. The rescue system has been applied to Changcun Coal Mine owed to Lu'an Group.
Abstract: Aiming at the problem of fuzziness and randomness in the process of emergency disasters and accidents decision-making, this article introduces a method of emergency decision-making based on the cloud model. Firstly, decision indexes are selected according to the target and characteristics of rescue in emergency disasters and accidents, and the set of decision indexes is established. Secondly, the weight values and evaluation values of decision indexes are determined according to decision-makers' linguistic values and the relevant range, and the digital characters of the cloud model are produced by backward cloud generator. Thirdly, the evaluation cloud of each alternative is calculated through the arithmetic rules of cloud. Finally, the similarity between each alternative's evaluation cloud and standard evaluation cloud is compared to obtain the comment grade of each alternative, and the best alternative is selected. Case studies show that the method could take full advantage of expert group information, and make the conversion between qualitative description and quantitative indication more effective. The result is objective and feasible, which could improve decision-making objectivity and emergency management effectiveness.
Abstract: The optimal bandwidth scheduling problem was studied for a two-layer networked learning control system (NLCS). A dynamic bandwidth scheduling methodology based on the network pricing mechanism was proposed to allocate the bandwidth for each subsystem, so the network resource allocation problem was transformed into the solution of the Nash equilibrium with a non-cooperation game model. Under this framework, particle swarm optimization (PSO) was used to obtain the Nash equilibrium for NLCS, and the time slice scheduling method was also provided. Simulation results were given to demonstrate the effectiveness of the proposed approach.
Abstract: The three-dimensional arch structure is a new style of large-span structure, which synthesizes the advantages of the arch and dragline. As a light and highly active structure, the three-dimensional arch structure has been used widely. In order to make further research on the mechanical behavior of the structure, a 1:20 scale model test was carried. The test data show that the stress of the springing is the greatest and those of the other structure parts are less. The dragline is important to improve the bearing capacity and the ability of resisting deformation.
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
