Abstract: Because of the complexity of the residual orebody space form,the traditional cutting drawing method is difficult to show the orebody form intuitively and comprehensively,leading to difficulties in cutting engineering design,while SURPAC uses a 3D modeling method to solve this problem. An induced caving method of residual orebodies was investigated with Xishimen Iron Mine as the background. The trench's ore quantity,metal quantity and grade were calculated by SURPAC. The horizontal and vertical positions of a trench tunnel were taken as the optimization objects,and the trench tunnel in both directions was laid out by analyzing the critical caving span and the field engineering and technical conditions. According to the scope,a scheme of orthogonal test was designed.Taking extraction metal quantity and average grade as the assessment indexes,the range analysis and variance analysis of orthogonal test were conducted to obtain the position of a trench tunnel: double trench tunnels have a separation distance of 24 m,with a horizontal level of 118 m. Along with the scene implement,ideal test results have been achieved for refinement caving.
Abstract: In order to realize the dynamic and scientific optimization of production plans for multi-metal underground mines,we convert underground mining processes into a mathematic model constrained by several conditions to meet technical and economic requirements as well as spatial sequence relation,which aims to maximum profits. Operating units including cutting,blasting,mining and filling are treated as a whole process in the model. The underground mining condition of equilibrium and continuity is transformed into a space constraint. Considering the mining state of ore blocks as the decision variable,a model of production planning optimization is constructed by binary integer programming and calculated by an algorithm based on the artificial bee colony model. The optimization model was applied in a multi-metal underground mine in Tibet in southwestern China to optimize the production plan in the next three years which was illustrated by three-dimensional visualization display. The optimal solution indicated that the dynamic adjustment of the mining area could guarantee continuous production and increase the economic benefit of mine exploitation.
Abstract: The adsorption and activation mechanisms of Cu2+ and Ni2+ ions on serpentine were investigated through adsorption measurements,pure mineral flotation tests and IR spectra analyses. It is found that the adsorption of Cu2+ and Ni2+ ions on serpentine agrees with the second order kinetics model,and the isothermal adsorption process correlates well with the Langmuir isotherm model.The adsorption is a spontaneous process,which is caused jointly by physical and chemical functions. The adsorption amount of Cu2+ and Ni2+ ions on serpentine increases with increasing p H values. Under a weak alkaline condition,serpentine can be activated by Cu2+ and Ni2+ ions. The active sites can be formed on the surface of serpentine after being reacted with hydroxide and hydroxy complexes of copper and nickel,on which xanthates can be adsorbed to generate copper and nickel xanthates. These hydrophobic products improve the surface hydrophobicity of serpentine and thus activate its flotation.
Abstract: The size distribution,microstructure and high temperature properties of titanium sands after grinding were studied in the paper. The influence and mechanism of titanium sands on the sinter quality were identified by sinter pot test and scanning electron microscopy and energy dispersive spectrometry(SEM-EDS) test. It is found that the micromorphology of titanium sands becomes more irregular after grinding,and the granulation gets strengthened. Meanwhile,the high temperature characteristics of sintering are different with the common iron ore fines: when titanium sands become finer,the assimilation temperature improves by 21 ℃,and the liquid phase fluidity index decreases by 0.35 at 1280 ℃. The reason for these differences is that titanium sands after grinding react with Ca O to produce more perovskite,which can hinder the assimilation reaction and get the liquid phase stickier. In comparison with unground titanium sands,the reduction index(RI) of sinters produced with 8% of ground titanium sands in blends improves by 3.8%. The reasons are that titanium sands are distributed more uniformly in blends after grinding,resulting in the increase of phase particles containing titanium in sintered ores,and many microcracks emerge in the reduction reaction,which is in favor of reducing gas diffusion.
Abstract: A silicon sensor auxiliary electrode was successfully synthesized by evenly coating CaF2+SiO2 powder on the surface of ZrO2(MgO) solid electrolyte and roasting at 1400 ℃ for 30 min in high purity Ar atmosphere. The effects of preparing conditions on the composition,crystal phase and morphology of the formed auxiliary electrode membrane after calcination were systematically investigated by X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry. It is shown that SiO2 solid particles,CaO·MgO·2SiO2 solid solution and ZrSiO4 are the main components of the formed auxiliary electrode layer and no CaF2 exists in the layer. In addition,the influences of phase transformation on the film adhesive property and silicon sensor performance were also discussed. The as-prepared silicon sensor which is used to detect silicon content in molten iron at 1450 ℃ shows a better performance.When the silicon content ranges from 0.5% to 1.5% in liquid iron,the testing result based on this silicon sensor with a response time of 10 s and a steady time more than 20 s agrees well with the value based on the chemical analysis method.
Abstract: To make full use of Chinese symplesite resources,refining slags and different Ca alloys were added to molten steel as dearsenization agents in the experiment. The Si-Ca-Ba alloy showed the most obvious dearsenization effect. Under the same operation conditions,the change of arsenic content in molten steel was investigated by changing experimental conditions,and the influences of experimental conditions on the dearsenization effect were discussed. Simultaneously,the utilization ratio of Ca after adding different Ca alloys to molten steel at high arsenic content was discussed in detail.
Abstract: A three-dimensional mathematical model is developed based on the Navier-Stokes momentum equation and the low Reynolds number turbulence k-ε equation. This model comprehensively considers energy conservation,molten steel solidification and the influence of the mushy zone on the flow process. Heat flux obtained through an inverse heat transfer model combined with measured temperature is set as the boundary condition to the coupling model,to investigate fluid flow,heat transfer and solidification in the continuous casting mold. It is found that liquid steel flow has important influence on the distributions of temperature and heat flux,and the solidification process is governed by a synthetic action of fluid flow and heat flux. The proposed model and the non-uniform characteristic of solidification can provide reference for further investigation on longitudinal cracks and other surface defects during continuous casting.
Abstract: Due to high Cr and C contents,there are a mass of network eutectic carbides precipitating at grain boundaries in the as-cast Cr12Mo1V1 cold working die steel. After forging,most of them are long strip-shaped and have a zonal distribution,leading to a decrease in thermoplasticity,easy formation of cracks,and thus the limit of application. The effects of Mg addition on the carbides and thermoplasticity of the Cr12Mo1V1 steel were investigated in the present study. It is found that with increasing Mg content in the steel,network eutectic carbides in the as-cast steel are interrupted and refined,and can be shattered more easily during the later forging procedure. Meanwhile,the average size of carbides in the forged steel decreases with increasing Mg content,and these carbides present a uniform diffuse distribution. The improvement in size and distribution of carbides enhances the thermoplasticity of the steel.
Abstract: The electromagnetic properties of high-carbon ferrochrome powders(HCFCP) obtained at different cooling rates were investigated by means of the vector network method in the frequency range of 1 to 18 GHz. It is found that both the real part and the imaginary part of the relative complex permittivity of HCFCP show an increasing order with a rising in cooling rate at most frequencies,of which prominent peaks occur in the imaginary part of the air-cooled and water-cooled powders on account of polarization relaxation.For comparison,both the relative complex permeability and magnetic loss factor present complex change histories,where the real part of the relative complex permeability decreases as the cooling rate rises,and the imaginary part of the water-cooled powders occupies the dominant except for the frequency range from 3 to 5 GHz. While peaks in the imaginary part of each cooling sample principally result from the effect of nature resonance and magnetic hysteresis respectively corresponding to low frequency and high frequency. The reflection losses of furnace-cooled,air-cooled and water-cooled HCFCP with the values of -2.30,-2.15 and -2.07 d B severally at 2.45 GHz,could meet the need of microwave heating in principle. By overall consideration,the water-cooled powders are determined as the optimal materials for solid-phase decarburization of HCFCP in a microwave field,attributed to a higher dielectric loss factor as well as a higher magnetic loss factor.
Abstract: The effects of cold rolling and annealing texture on the drawability of SAF 2205 duplex stainless steel were investigated. It is found that the deep drawability of SAF 2205 duplex stainless steel is poor with an average r value of 0.7 and the earing appears at 45° with a Δr value of -0.27,which is related with the texture formed during cold rolling and annealing. ODF results show that no γ fiber recrystallization texture forms in ferritic phase and the scattered α fiber texture still remains after annealing. Moreover,the ferritic texture exhibits a higher intensity than the austenitic one,thus it has more significant effect on the formability of the tested steel. It means that various components of the 〈110〉texture cause low average r values and make Δr<0. Furthermore,the {110}〈001〉texture of austenite exerts some effect on the formability of the sheet.
Abstract: The microstructures with different grain sizes and pearlite interlamellar spacings of high-speed railway wheel steel with a carbon mass fraction of 0.54% were achieved by heat treatment at different austenitizing temperatures and cooling rates. Notched 3-point bending(3PB) bars and tensile specimens with different microstructures were tested at temperatures from -120 ℃ to 20 ℃. The stress distribution ahead of the notch tip was calculated by a two-dimensional plane strain finite element method. The fracture surfaces of the 3PB specimens were observed by scanning electron microscopy and the cleavage initiation site was located. The cleavage fracture stress of specimens with different microstructures was measured. It is shown that the cleavage fracture stress depends on the microstructure when the cleavage critical event is propagation-controlled. The characteristic size of un-propagated microcracks decreases by grain refinement,the decrease of pearlite interlameller spacing is be propitious to increase the effective surface energy of the pearlite microstructure,so the cleavage fracture stress increases with decreasing grain size and pearlite interlameller spacing.
Abstract: The isothermal forging process of blades of a β-γ high niobium containing Ti Al based alloy was simulated by using a Deform-3D software,with focus on the analysis of the effective strain,effective stress and temperature distributions. The results demonstrate that the effective strains of the blade body and rabbet uniformly distribute during the isothermal forging process. With the increase of top die speed and preheating temperature,the effective stress decreases and the dynamic recrystallization is easy to take place. The preheating temperature of 1250-1300 ℃ and the top die speed of 1.0-1.5 mm·s-1 help to improve the quality of the forged blades.
Abstract: Carbon anodes for aluminum electrolysis were made of different calcination levels of coke as an aggregate and coal pitch as a binder. The porous structure parameters of carbon anode materials were characterized by using laser confocal scanning microscopy and the image analysis method. The anodic reaction and electrolysis consumption were also investigated in a lab scale aluminum electrolysis cell. The results demonstrate that the micropores gradually extend to crack-like macropores along the aggregate-binder interface with increasing coke calcination levels. The porosity,aspect ratio and connectivity first decrease and then increase,while the specific surface area decreases. It is appropriate to reduce the crystallite height of calcined cokes to 1.9 nm,so that the corresponding anodes can have the air reactivity of 9.6%,the CO2 reactivity of 3.0%,and the anode consumption of 355.4 kg per ton aluminum. The excessive consumption mechanism for the low calcined anode cokes may change from selective consumption of the binder to co-consumption of both the aggregate and the binder,which can reduce the carbon dust and the total carbon consumption in aluminum electrolysis.
Abstract: A model for calculating the adherent dross capability of copper cooling staves was founded by ANSYS birth-death element technology based on the finite element theory. The influences of gas temperature,cooling methods,slag properties,and cast-inbrick material on the adherent dross capability were evaluated and the corresponding influence rules were acquired. The calculation results showed that the adherent dross capability of copper staves exponentially decreased with increasing gas temperature. The adjustment of cooling methods could hardly change the adherent dross capability. The promotion of slag's adherent temperature enhanced the adherent dross capability while weakened the stability of slag layer thickness. The improvement of slag's heat conductivity increased the slag layer thickness linearly. The increase of heat conductivity of cast-in-bricks could significantly thicken the slag layer of the dovetail groove area on the copper stave. According to these calculation results,several principles were proposed to ensure the copper stave working steadily.
Abstract: Intensive cooling technology is widely used to produce high strength strip steel,but high cooling rate leads to some defects,such as shape waves caused by high residual stress. A numerical model was established to achieve a coupling calculation of temperature,phase transformation and stress for high strength steel(700 MPa) during intensive cooling. Commercial FEM software ABAQUS was used to build coupled models that verified by a series of experiments. The effects of edge masking and initial temperature difference on the residual stress were studied by modifying initial and boundary conditions. It is concluded that reducing the initial temperature difference is more effective to release the residual stress of strip steel during cooling. Proven by industrial experiments,these research results would be used to lower the residual stress and improve the quality of hot-rolled strips.
Abstract: Compared with traditional machining processes,the plastic forming of big spiral teeth shafts has obvious advantage of high production efficiency and material utilization,but the forming of proper tooth graduation is difficult. The parametric equation of die profile curves,closely related to transmission ratio,was established in this article. The law of transmission ratio between die and workpiece was studied by finite element simulation,and the reliable transmission ratio variation and die profiles were obtained. Taking the driven rotor as an object of study,the proper tooth graduation of big spiral teeth of the driven rotor was realized by fixed cross rolling experiment to solve the problem of proper tooth graduation.
Abstract: A wind tunnel of high temperature and long operation time requires the use of cooling techniques,so we need design cooling channels on the nozzle. In this paper,rectangular cooling channels of high cooling efficiency were used to study the factors affecting nozzle cooling. First of all,a three-dimensional model of nozzle cooling structure was established. Secondly,the type of heat transfer of the nozzle was detailedly analyzed and at the same time radiation heat transfer was taken into account. Then based on the principle of simplicity and accuracy,a series of assumptions were made for the calculation model. Finally CFD techniques were used to carry out the numerical simulation. By analyzing the results of study,we obtained the rules how the aspect ratio of cooling channels influenced nozzle cooling,the difference whether or not considering radiation heat transfer,and the impact of gas flow total temperature on nozzle cooling.
Abstract: The internal flow characteristics of axial flow absorbers were numerically studied by the computational fluid dynamics(CFD) method. The influences of three absorber models on the internal flow uniformity were compared: absorber without a flow distributor,absorber with a single flow distributor,and absorber with the combination of a flow distributor and a baffle. The results show that the flow is severely uneven without a flow distributor,is slightly meliorated with a single flow distributor,and is significantly improved with the combination of a flow distributor and a baffle. For the combined configuration,the best flow uniformities are obtained with the pore diameter of 0.003 m as the pore opening ratio remains unchanged and with the pore opening ratio of 0.388 as the pore diameter does not change.
Abstract: A novel discontinuous space-vector pulse width modulation(DSVPWM) strategy is proposed for a three-level neutralpoint-clamped(NPC) voltage source inverter. Compared with traditional space-vector pulse width modulation(SVPWM),the proposed strategy can largely reduce the switching losses of the inverter at the same switching frequency. Then,solutions to the imbalance of neutral-point voltage and the PN voltage jumps during application are proposed in this paper. At last,the three-level DSVPWM strategy is verified by simulation and experiment.
Abstract: Once a driver loses control of an operating vehicle on the highway,the guard rail installed as a protection will be important to eliminate the risk of fatal accidents during offroad crashes and collisions with hazardous roadside objects. The W-beam guard rail is one of the widely used passive safety devices designed to absorb loads applied by impacting vehicles. It can absorb the impact energy from large vehicles through the deformation of beams,blockouts and posts according to the traditional design method. However,contributions from the soils which the posts are rammed into are neglected. To this purpose,two computing models with and without soil bodies were considered,respectively. The trajectory of the truck,the deformation of the guard rail and the soil were observed during crash simulations. Moreover,the energy-absorbed ratios of different components in the guard rail system were also analyzed. A comparison between the two models indicates that the soil bodies adjacent to the post beneath the ground may become instable under shock loading,and more than 10% of the total impact energy is dissipated by the soil bodies. Consequently,the general fixed-base model cannot describe the real situation accurately enough.
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
