Abstract: Taking the mining of the 2# hanging wall ore in Daye Iron Mine by a filling method as an engineering background, the change of high-steep slope stability in the mining process was analyzed first in this paper. Then through using on-site monitoring together with similar material simulate experiments, the stress and displacement changing rules of rock pillars and surrounding rock were studied to discuss the effect of mining the hanging wall ore using the filling method on the surrounding rock stability. The results show that the average value of slope safety coefficient decreases from 1.274 to 1.005 after slope expansion and mining. This indicates that the slope stability is poor. Although the rock pillars and surrounding rock are stable currently, the existing mined-out areas must be filled to change the stress concentration state before the mining of pillar ore and the roof & floor ore.
Abstract: The hydration products and microstructure of slag cementing materials were characterized and the influence of slag cementing materials on the consolidation of tailings was investigated by using X-ray diffraction analysis, scanning electron microscopy and thermogravimetry-differential scanning calorimetry analysis. Microscopic experimental results indicate that the main hydration products of slag cementing materials are calcium silicate hydrate gel (C-S-H), ettringite (AFt), a small amount of partheite (Ca2Al4Si4O15(OH)2·4H2O) and zeolite minerals. It is found that the crystal structure recombines and rearranges in the hydration process with the increase of curing time. Cristobalite, mica and carbonate minerals (calcite, dolomite, etc.) are active components in the tailing consolidation process, which can generate new crystal and gelatinous minerals. This is the main reason for the difference of consolidation microstructure.
Abstract: In terms of holistic digital modeling and three-dimensional (3D) visualization, an underground mine was treated as a dynamic field, named as the underground mine complex field, which includes various geometries, attributes, parameters, and states. By analyzing the geometric, distributive, directional, temporal and spatial characteristics of these field variables, this paper proposed a characterization method of these variables and their relations, and then built a holistic digital model of the complex field based voxelization. Specific techniques for building the holistic digital model were developed by voxelizing, quantifying, regionalizing, and integrating these field variables. A case study was used to implement the model and techniques. It is demonstrated that the holistic approach in the paper is effective for digital modeling and 3D visualization of the complex field, including geometric variables such as topography, faults and opennings, distributive variables such as ore grade, and directional variables such as air flows and mine fires.
Abstract: In consideration of the matrix-crack-wellbore coupling flow and matrix-wellbore coupling flow in an open-hole fractured horizontal well in low/ultra-low permeability reservoirs, mathematical models were derived on the basis of the equivalent flowing resistance method and the superposition principle. For an open-hole fractured horizontal well, the flow field was divided into three regions according to the different flow mechanism:Darcy flow in artificial fractures, low-velocity non-Darcy elliptical flow in the matrix around artificial fractures, and low-velocity non-Darcy plane radial flow in the peripheral matrix. A non-Darcy analytical productivity equation for an open-hole fractured horizontal well was obtained considering mutual interference between multi-transverse fractures. The influences of hydraulic fracture parameters on oil production were analyzed, which reveals the variation in development of an open-hole fractured horizontal well. Numerical results show that the more the artificial fractures, the stronger the interference of artificial fractures, and consequently there exists an optimal quantity of artificial fractures. It is suggested that the artificial-fracture distribution should be dense at two ends of the wellbore and sparse in the middle of the wellbore; in addition, the length of artificial fractures at the two ends should be larger than that in the middle.
Abstract: In order to research the transformation process and transformation path of siderite during heating process in strong reduction atmosphere, the thermal behaviors of siderite from Jiayuguan Mine in Gansu Province of China under coal-based direct reduction conditions were studied by thermogravimetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The existence form of iron minerals in roasting products in different roasting conditions was observed. It is shown that the path of transforming siderite into iron is FeCO3→Fe3O4→FeO→Fe. The transformation process includes two stages:siderite decomposition and iron oxide reduction. The thermal decomposition stage of siderite finishes at 556.6℃, and the product is Fe3O4; the reduction of iron oxides comes out after 556.6℃ and finishes completely at 1 200℃, and the final product is metallic iron.
Abstract: Chalcopyrite-pyrite bioleaching tests were performed with shaking flasks by Acidithiobacillus ferrooxidans. The research focused on the effects of basic salt mediums, pyrite-to-chalcopyrite mass ratio and mineral size distribution. It is found that chalcopyrite bioleaching can be promoted by pyrite. The leaching rate of copper in the iron-free 9K medium in pyrite-chalcopyrite bioleaching is 1.68 times as large as that in the 9K medium. The leaching of copper is better using a wide size range of minerals and the leaching rate of copper is related to the mass ratio of pyrite to chalcopyrite. When the mass ratio is 2:2, the highest leaching rate of copper is obtained to be 45.58%. The content of pyrite is of the essence in affecting the leaching rate level of copper. At a mass ratio of pyrite to chalcopyrite no more than 5:2 the oxidation of Acidithiobacillus ferrooxidans plays an important role in the bioleaching, but when the mass ratio is 10:2 the galvanic effect between the two sulphide minerals mainly influences the bioleaching. X-ray diffraction analyses of leaching residues indicate that the generation of jarosite in the iron-free 9K medium is less than that in the 9K medium, FeSO4 in the 9K medium can be replaced by pyrite, the galvanic effect forms with chalcopyrite, and therefore the bioleaching efficiency of copper is increased.
Abstract: Inclusion distribution in 16.8 t ingots of high pressure boiler tube steel P12 was studied by dissection, total oxygen analysis, original position statistic distribution analysis (OPA), metallographic microscope static analysis and small sample electrolysis. It was found that a negative inclusion segregation area existed in the central part of the ingot head where the inclusion quantity is lower; while a positive inclusion segregation area existed in the center and lower part of the ingot where the inclusion quantity is higher. A new concept of inclusion segregation index was put forward to describe the segregation degree of inclusions. Total oxygen analysis and OPA results demonstrated that the segregation indexes of oxide inclusions were 1.4 to 1.6 in the central and lower part of the ingot and 0.5 to 0.7 in the central part of the ingot head. As both oxide and sulphide inclusions were tested by metallographic microscope static analysis and slime small sample electrolysis, the inclusion segregation indexes were about 0.7 to 0.8 in the central part of the ingot head and 1.15 to 1.35 in the center and lower part of the ingot. The average size of oxide inclusions in the central and lower part of the ingot was bigger than that in other places, showing that the main mechanism for inclusion segregation in the central and lower part of the ingot is the picking of large inclusions by showering crystallites during floatation.
Abstract: A thermodynamic model of binary low-carbon microalloyed steel with 0.023% Nb and 0.012% Ti additions was established to calculate the equilibrium molar fraction and chemical driving force of carbonitride precipitation as well as the molar fraction of each element in austenite at temperatures from 1 073 to 1 523 K. The evolution of precipitation in the microalloyed steel was studied, and the precipitation pattern was verified by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The calculating results show that the chemical formula of precipitation particles is (Nb0.15Ti0.85) (C0.16N0.84) at 1523 K, Ti-rich precipitates gradually transit to Nb-Ti uniform precipitates. The evolution order of precipitation particles is (Nb0.15Ti0.85) (C0.16N0.84), (NbxTi1-x) (CyN1-y) and (Nb0.5 Ti0.5) (C0.56 N0.44), which accord with the experimental results. The Ti/Nb mass ratio decreases gradually with decreasing temperature, and TiC is more insoluble than NbC. The critical core size and the relative nucleation rate were computed under two nucleation conditions, and the temperatures at which the size of the second phase is the smallest, i. e. the nucleation rate is maximum are 1 198 K and 1 123 K for homogeneous nucleation and dislocation nucleation, respectively.
Abstract: The influence of electro-pulse modification on the growth kinetics of hot-dip galvanizing coatings was studied through an orthogonal test method. The time exponent of growth rate was taken as an evaluation index to optimize the treatment effect of electropulse modification. Orthogonal experiment results show that pulse capacitance has the most significant influence on the growth of the alloy layer, but the influence of treating time is little. The effect of electro-pulse modification would be better in the condition of the capacitance of 200 μF, the voltage of 700 V, the pulse frequency of 2 Hz, and the treating time of 30 s. Hot-dip galvanizing experimental results at these optimum parameters show that the growth of the alloy layer is inhibited, the coating thickness is decreased, and the structure is more dense and uniform. The time exponent of growth rate decreases from 0.717 to 0.428. The growth pattern of the alloy layer transforms from integrated control by interface reaction and diffusion to independent control by diffusion.
Abstract: The effects of welding thermal cycle parameters on the microstructure and properties in the heat affected zone (HAZ) of hull structure steel for high heat input welding were studied by thermal simulation technique, optical microscopy and transmission electron microscopy (TEM). It is found that the microstructure of the simulated HAZ is mainly composed of granular bainite, ferrite and pearlite, but it varies markedly with the change of peak temperature and cooling time. The overall level of impact toughness of the simulated HAZ is higher than 200 J, and the impact toughness does not monotonously change with the peak temperature and the cooling time increasing. The amount, size, distribution and shape of M-A constituents in the simulated HAZ are the main influencing factors on the impact toughness.
Abstract: As-cast and as-spray formed billets of M3 high speed steel were produced through traditional casting and spray forming, respectively. The effect of cooling rate on the microstructures of the cast and spray-formed steels, the relation of heating temperature to the decomposition of M2C eutectic carbide, and the microstructural evolution of the cast and spray-formed steels after hot working were studied using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXA), and X-ray diffraction analysis (XRD). The as-cast structure contains coarse primary dendrites and M2C eutectic carbide, but the spray-formed one consists of equiaxed grains and fine carbides. High cooling rate can suppress the carbide precipitation and grain growth. Elevated temperatures are favorable to the decomposition of M2C eutectic carbide, but an exorbitant temperature results in the growth of M6C carbide, which will cause the properties of the steel to deteriorate. A desired deformation microstructure of the spray-formed steel can be obtained by appropriate preheating and hot deformation.
Abstract: Thermodynamic equilibrium phase diagrams of three candidate materials, Inconel740, Inconel617, and GH2984, for 700℃ advanced ultra-supercritical boiler tubes were calculated by Thermo-Calc software and nickel-base alloy databases. Precipitation behaviors of phases in the three alloys were investigated by comparison. There are similar equilibrium phases in the three alloys, including γ, γ', carbides, σ, η, δ, μ, and α-Cr. Serious segregations of Mo, Ti and Nb may occur during solidification based on the calculation, which would decrease the initial melting points of the three alloys; therefore the consequent homogenization treatment is quite important. On the other hand, the amount of γ' precipitated in Inconel740 is higher than that in the other two alloys at 750℃. Al and Ti contents can strongly effect the precipitation of γ' and η phases. The calculation of carbides indicates that primary carbides in Inconel617 are different from those in the other two alloys, and the precipitation temperature range of secondary carbides in Inconel617 is larger. The presence of σ in GH2984 alloy is harmful to the mechanical properties due to a higher Fe content.
Abstract: To determine the deformation parameters of AZ31 magnesium alloy, the hot deformation behavior of the alloy was investigated by hot compression testing on a Gleeble-3500 stimulator. The principle of dynamic material modeling was used to develop the hot processing map. There is a dynamic recrystallization peak zone in the processing map at temperatures from 380 to 400℃ and strain rates from 3 to 12 s-1, and the efficiency of power dissipation is more than 30%. A fine equiaxed grain size of 2.3 μm could be achieved when differential speed rolling is processed in this region. The tensile strength is 322.7 MPa and the elongation is 19.6%. At strain rates of 15 to 50 s-1, there are two flow instability zones:at temperatures of 250 to 300℃ the ductility of the alloy decreases obviously, but at temperatures of 350 to 400℃ the alloy has a mischcrystal structure.
Abstract: Ta(NiFeCr)/NiFe/Ta films with Ta and NiFeCr buffer layers were prepared by magnetic sputtering. In comparison with Ta buffer layers the anisotropic magnetoresistance (AMR) values of the films with NiFeCr buffer layers increase dramatically for the same NiFe thickness. X-ray diffraction results show that the NiFeCr buffer layer promotes the formation of a stronger (111) texture in the NiFe films. High resolution transmission electron microscopy results show that the lattices of the NiFeCr buffer layer and the NiFe layer match well and the NiFe layer grows epitaxially along the direction of NiFeCr crystallites, so the films with NiFeCr buffer layers have a good crystal structure. After the films were annealed, the AMR values of the films with NiFeCr buffer layers keep constant when the temperature is below 350℃ and then decreases dramatically with a further increase of temperature. The films also have a good thermal stability after heat treatment at a temperature below 350℃.
Abstract: Using RTO metal embeds cutting film micron-nano token method, the lattice fringe images of γ-AlOOH film slices were observed by high-resolution transmission electron microscopy, and the microstructure of heterotypic nano AlOOH with additive package was analyzed. It is revealed that the isomorphous replacement of iron ions and the intercalating of sulfate ions result in the lattice distortion. During crystal whisker growth, a composite polymer firstly forms, and then directionally grows; also the apolar surfactant has the functions of surface-restoring and beautifying the crystal morphology. X-ray diffraction analysis and infrared spectra are used to validate the existence of the composite polymer.
Abstract: Multi-walled carbon nanotubes (CNTs) were coated with tungsten layers using a carbonyl thermal decomposition process. The tungsten-coated carbon nanotubes (W-CNTs) and electrolytic copper powders were used as starting materials to fabricated W-CNT/Cu composites by mechanical milling and spark plasma sintering (SPS). The morphologies and microstructures of the mixed powders and the sintered composite bulks were characterized by field-emission scanning electron microscopy (SEM), and the phase analysis of the sintered composite bulks was carried out by X-ray diffraction (XRD). The influences of W-CNT content and sintering temperature on the relative density, tensile strength, elongation and electrical conductivity of the W-CNT/Cu composites were investigated. The experimental results show that the 1% W-CNT added composites sintered at 850℃ have the maximum relative density, tensile strength and electrical conductivity. In comparison with the sintered pure Cu bulk, the tensile strength increases by 103.6% but the electrical conductivity decreases only by 15.9% for the W-CNT/Cu composites.
Abstract: By analyzing the temperature distribution of traditional briquetting in a magnesium reduction retort, it is necessary to improve the briquetting's shape to shorten the reduction cycle of the magnesium silicon thermal reduction method. The heat transfer process of a new-type briquetting for magnesium reduction was simulated by FLUENT software, with focus on the influence of the briquetting'height, edge height, inner diameter, bottom diameter, notch diameter and notch number on the heat transfer process and the magnesium output. It is found that the maximum magnesium output is 318 kg·h-1 when the briquetting's height is 100 mm, the edge height is 50 mm, the inner diameter is 100 mm, the bottom diameter is 200 mm, the notch diameter is 50 mm, and the notch number is 8. Compared with the traditional briquetting, the magnesium output increases by 43.9% and the gas consumption for per ton magnesium decreases by 30.5%. The internal temperature distribution of the briquetting in the experiment is consistent with the simulation results, indicating that the model of numerical simulation is reliable.
Abstract: A method was proposed for fault feature extraction based on the gray-scale hit-or-miss transform. Several target waveforms are chosen from the analyzed signal, and then hit-or-miss structure element pairs could be thereby calculated. Pattern matching is carried out at every sample point, and higher output is obtained when fault features occur. As the method was used to analyze the rubimpact signal of a driving motor and the impulse signal of a rotator test-bed in an oxygen manufactory, fault features were successfully extracted. The method is close to artificial thinking and easy to understand, so it is an effective method to extract fault features from a time domain waveform straightly.
Abstract: A reheating furnace area scheduling problem in steel production has the NP-hard feature of a combinatorial optimization problem. A mathematical model of the scheduling problem was established according to the production features of the furnace area. Of the scheduling model, the first aim is to minimize the energy consumption cost and the second to optimize the heating quality, so the scheduling problem can be summed up as a Boolean satisfiability problem. A binary encoding method and a hybrid genetic-tabu search algorithm were proposed to solve the mathematical model. Simulation results based on practical data show that the mathematical model and the solution method fully satisfy the demand of furnace area production scheduling. Under the condition of meeting process constraints, the production time is reduced, the charging temperature is increased and the heating quality is improved. The mathematical model and the solution method have a better performance of high production and energy efficiency than the traditional manual scheduling method.
Abstract: The state estimation problem was studied for neural networks with mixed discrete and distributed time-varying delays as well as general activation functions. The discrete time-varying delay varies in an interval, where the lower bound is not fixed to be zero. Defining a novel Lyapunov functional and using the Jensen integral inequality, a delay-interval-dependent criterion is provided to design a state estimator through available output measurements in terms of a linear matrix inequality (LMI), such that the error-state system is globally asymptotically stable. A numerical example was given to illustrate that this result is more effective and less conservative than some existing ones.
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
