Abstract: According to the principle of deriving mine dust distribution from the Rosen-Rammler distribution function,dust particle size distribution data at four places on the 4339 working face in Wangzhuang Coal Mine were regression-analyzed so as to get the dust particle size distribution law.The results show that in the area of 5 m away from the working face in the intake airway,the percentages of mine dust of less than 5 μm,5 to 10 μm and larger than 10 μm in particle size are 14.8%,32.5% and 52.7%,respectively,with a concentrated distribution of 5 to 20 μm.The size of mine dust concentrates in the range of 5 to 10 μm for the transfer point,in the range of 5 to 10 μm for the 50# support of the working face,and in the range of 5 to 20 μm for the area of 20 m away from the working face in the outlet lane.Some corresponding dust-proof suggestions were finally put forward on the basis of the characteristic of mine dust distribution in different places.
Abstract: In order to realize efficient development to scarce geological resources,an economic evaluation model for mineral deposits is established by taking net present values (NPV) as the objective function.The method of profit element is introduced to calculate the equivalent grades.Then,based on the three-dimensional digital deposit model,an optimization algorithm for calculating both of the optimum comprehensive cut-off grade and the break-even cut-off grade is developed when respectively directing to the objectives of a maximized NPV and the zero NPV.A practical application of the model to calculating the optimized cut-off grades has been done through a copper-molybdenum deposit case.It is approved that it can not only provide accurate economic analysis for the mine investment and production planning,but also ensure the optimal utilization of resources.
Abstract: Enhancing the bioleaching of low-grade phosphorite ore by mixed strains composed of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans was studied.The results showed that it was not suitable to bioleach this phosphorite ore due to its low content of S,adding pyrite as enhancement to the leaching solution was recommended and the effects of process parameters such as bacteria variety,mass ratio of phosphorite ore to pyrite and initial mass fraction of Fe2+ on the bioleaching rate of phosphorus were investigated.A higher leaching recovery was achieved with the acclimated mixed strains.The optimal leaching parameters were determined as follows:the initial Fe2+ mass fraction of 9 g·L-1 and the mass ratio of phosphorite to pyrite by 1:2.5.Under the optimal condition,the phosphorus recovery rate reached up to 95% within 20 d.
Abstract: Silicon carbide as a assistant wave-absorbing material was used to study the microwave-drying process of a low-grade laterite ore.The effects of SiC mass fraction on the weight-loss rate and phase composition of the laterite ore were analyzed by thermogravimetric analysis (DTG),X-ray diffraction analysis (XRD) and Fourier transform infrared spectroscopy (FT-IR).It is shown that when the SiC-to-ore mass ratio is 2.2:1,most of surface-absorbed water and part of crystal water in the laterite ore can be rapidly removed by microwave drying for 30 min.Overheating phenomena can be avoided by controlling the addition amount of SiC,too.Microwave treatment changes the microstructure and promotes the decomposition of the laterite ore.Hydrogen reduction experiment results indicate that the microwave-drying process benefits to the reduction of nickel and iron oxides in the laterite ore.The reduction rates of iron and nickel in samples through microwave drying are higher than those through conventional drying.
Abstract: Metallurgical characteristics in the electric arc furnace steelmaking process were analyzed.The result showed that energy supply played a decisive role on material transformation.On the basis of the realization of space-time multi-scale structures which contained microscale,mesoscale,unit operation and working operation scale,trans-scale integration on two units of oxygen supplying and power supplying was realized according to energy in working operation scale and a general method of energy integration was formed.Its mathematical and physical expressions could be described.Industrial test and industrial production indicated that great production efficiency was made in combination with the idea and method of trans-scale integration.The smelting electricity consumption was 271.1 kW·h·t-1,the oxygen consumption 40.4 m3·t-1,and the smelting period 52.9 min on average.
Abstract: Based on an idea that the flow pattern of molten steel in a mold can be controlled by changing the direction of jet from the outlets of a submerged entry nozzle (SEN),a new type of quad-furcated SEN with outlets in tangential direction was designed for bloom casting.The flow patterns and temperature distributions of molten steel in the mold were computed by hydrodynamic models under the conditions of single straight SENs,quad-furcated SENs with outlets in radial direction,and quad-furcated SENs with outlets in tangential direction.For the latter,a strong horizontal swirling flow has been observed along with the upper and lower back flows in the mold.The horizontal swirling flow pattern in the mold can not only reduce the impingement depth of molten steel,inhibit liquid level fluctuation and accelerate inclusion floatation,but also be beneficial to dissipation of steel superheat.Compared to quad-furcated SENs with outlets in radial direction,the jet impingement on the initial shell can be obviously reduced and the cross-section solidified shell distributes uniformly in the mold.Additionally,the horizontal swirling flow pattern moves the hot spot upward in the mold and leads to a 2 to 6 ℃ temperature rise of molten steel around the free surface,which is beneficial to quick melting of mould powder.
Abstract: The liquidus and solidus temperatures and the Ti and N activities of high speed wheel steel at 1 873 K were obtained by thermomechanically analyzing the precipitation of TiN inclusions.The formation reaction of TiN and the solubility product of Ti and N in the steel were calculated,and the results show that TiN inclusions only form in solid phase,but under the chemical composition of this wheel steel,TiN inclusions can not be produced in solid phase.Only in a solidification front,the formation reaction of TiN can take place owing to the enrichment of Ti and N in the two-phase region.During an engineering process,properly increasing the cooling rate of the secondary cooling zone in a continuous caster to make the rapid solidification of molten steel and shorten the enrichment time of Ti and N in a solidification front can decrease the precipitation of pure TiN inclusions.The calculations and analysis on detection results of TiN inclusions in the experimental wheel steel show that the best way of removing the precipitation of pure TiN inclusions in theory and improving the fatigue properties and service life of the wheel steel is controlling the content of Ti below 3.5×10-5 and the content of N below 3.1×10-5 in the steel under the condition of normal cooling rate.
Abstract: The Bauschinger effect of X80/X100 pipeline steels produced with a Steckel mill was investigated using uniaxial compression-tensile experiments under different deformation conditions.The results show that the absolute value of Bauschinger effect increases with the increment of pre-compressed deformation,and reaches saturation for X100 pipeline steel when the pre-compression is 1.5%.As the strength of the pipeline steels increases,the Bauschinger effect becomes more obvious.Under the experimental conditions,X80 and X100 pipeline steels represent transient softening and permanent softening,respectively.In combination with the chemical composition and the microstructural characteristics of X80/X100 pipeline steels,it is revealed that for the pipeline steels,the strength difference between soft and hard phases (M/A islands for instance),the volume fraction of hard phases,and the dislocation density in original microstructure are the key factors of Bauschinger effect.
Abstract: A novel type of 1 500 MPa grade Si-Mn-Cr-Ni-Mo multi-component ultrahigh-strength low-alloy structural steel was designed.The effects of tempering temperature on the microstructure and mechanical properties of the directly-quenched steel were investigated.The results showed that with increasing tempering temperature the tensile strength continuously reduced while the yield strength gradually increased and then decreased.The elongation and impact energy firstly increased,then decreased and increased again with increasing tempering temperature.The physical mechanism of microstructural evolution during tempering includes two aspects:(1) recovery and recrystallization softening processes of lath martensite and dislocation substructure;(2) strengthening mechanism due to decomposition of retained austenite,dissolution of supersaturated carbon and precipitation of the second phase in martensite.ε-carbide precipitation was found in lath martensite after tempering at 250 ℃,and coarsened after tempering at 400 ℃,leading to temper embrittlement.After tempering at 600 ℃,part of the precipitate phase nucleated in austenite,grew up and coarsened in martensite,eventually showed quasi-spherical shape,the other part of the precipitate nucleated and grew up in martensite,and appeared ellipsoidal or rectangular.
Abstract: Experiments were performed by interrupting secondary recrystallization processes in a CGO silicon steel.The results show that the average size of Goss grains is obviously larger than that of other grains just before abnormal growth in the temperature-rising process of secondary recrystallization.The amount of different orientation grains at this stage is almost the same as that in a decarburizing-annealed sample.Goss grains can first grow abnormally due to preferred coarsening of such inhibitors as MnS in Goss grains.It is noted that only Goss grains with seriously curved grain boundaries or several grains merged by slight growth can be the nuclei of secondary grains.During abnormal growth of Goss grains,their grain boundaries have zigzag shapes.It is believed that this unique growth pattern is the reason that secondary recrystallization can finish quickly.
Abstract: Phosphide precipitates in weathering steels with Ti addition produced by CSP processing were studied by using TEM and X-ray energy dispersive spectroscopy (EDX).The specimens were hot strips and a continuous casting slab.The slab was reheated and compressed by 20% at 900 ℃,followed by isothermal holding for 30 min.The results show that phosphides MxP in nanometer scale exist in the weathering steels.The value x is 2 to 3,and metallic elements M are Fe,Ti and Cr or Ni.The crystalline structure of the phosphides is hexagonal,the lattice parameters a=0.609 nm and c= 0.351 nm.In the hot strips,the size of most phosphide particles is smaller than 20 nm.But in the slab,the phosphides are with varied dimension and shape.The larger phosphide particles are rod-like,about 50 nm in width and 300 nm in length,but the others are smaller than 50 nm and in square shape.The phosphides may precipitate during the processing of the last pass of hot rolling and cooling until 400 to 500 ℃.Phosphide precipitation can result in strengthening the steels,but the phosphor content in solid solution of the steels decreases.
Abstract: The corrosion behavior under coatings with a point defect was investigated in situ by means of scanning Kelvin probe in both salt spray test and cyclic wet-dry immersion test.The results showed that the Kelvin potential distribution was identical in both the tests due to the same division of coating surfaces:defect area with the highest potential,delaminated area,and intact area with the lowest potential.Through monitoring the augment of diameter of Kelvin potential peaks with time,the expansion of the delaminated area was revealed.In cyclic wet-dry immersion test,the highest Kelvin potential Vmax did not change obviously with time while the lowest potential Vmin increased after reaching at the valley.On the other hand,in salt spray test,different from the rule in cyclic wet-dry test,Vmin was minimized at the first stage of the test resulted from the continued diffusion of the electrolyte and the corrosive ability of slat spray particles.Based on the changing pattern of Vmax-Vmin,it was concluded that in cyclic wet-dry immersion test,the tendentiousness of corrosion got the highest level when the test kept going for 5 h.However,in salt spray test,it achieved the highest level just at the beginning of the test and was more intensive than that in cyclic wet-dry immersion test.
Abstract: A357 aluminum alloy billets were continuously rheocast by annular electromagnetic stirring (A-EMS),and the effects of stirring current,stirring frequency and annular gap width on billet microstructures were analyzed.It is shown that more uniform microstructures of A357 aluminum alloy billets from the edge to center can be produced by A-EMS,and the primary α(Al) phase is spherical or rosette-like.With the stirring current or the stirring frequency increasing,the rosette-like primary α(Al) phase decreases significantly on the billet microstructures,and the nondendritic primary α(Al) is finer and more spherical.Narrow annular gap is advantageous to obtain uniformly fine spherical solidification structures.
Abstract: The high temperature mechanical properties and deformation behavior of powder metallurgy Ti-47.5Al-2.5V-1.0Cr alloy were investigated in a temperature range of 600 to 1 050 ℃ and a strain rate range of 0.002 to 0.2 s-1.The results show that during the hot deformation the yield strength of the TiAl based alloy decreases,whereas the ductility tends to rise with increasing deformation temperature and decreasing strain rate.The interrelations of peak flow stress,strain rate and deformation temperature can be described by Arrhenius' equation modified by a hyperbolic sine function,which indicates that the hot compression deformation is controlled by thermal activation.Under the deformation condition of 800 to 1 050 ℃/0.002 to 0.2 s-1,the strain sensitivity of the alloy is 0.152,whereas the deformation activation energy of high temperature deformation is 376 kJ·mol-1.
Abstract: An aluminum matrix composite with high volume fraction of SiCp was prepared by pressureless infiltration.Cup-shaped parts were made of the SiCp/Al composite by using high temperature backward extrusion.The flow stress behavior of the SiCp/Al composite during hot backward extrusion was investigated.The effects of hot backward extrusion parameters on the microstructure of the SiCp/Al composite were observed and analyzed by SEM.The results show that at temperatures above the melting point of aluminum matrix the SiCp/Al composite is a viscous fluid,SiC particles and aluminum matrix form into a solid-liquid mixture.When the SiCp/Al composite is backward extruded at high temperature,aluminum matrix remains continuous,but SiC particles roll over and rearrange under pressure,some particles break,and the particle distribution uniformity is good.As the deformation temperature is lower and the extrusion speed is rapider,SiC particles are easy to break,the internal particle size distribution of SiCp/Al composite cup-shaped parts is nonuniform,and the particle size is smaller in the internal angle position of cup-shaped parts.The particle size uniformly distributes at a higher temperature and a smaller extrusion speed.
The effect of aging microstructure on the fracture behavior of Mg-10Gd-3Y-0.6Zr alloy was investigated.The results show that precipitates in the alloy after low temperature aging at 473 K are finer and denser.Microcracks nucleate at grain boundaries due to grain boundary precipitations (GBPs),and then propagate transgranularly along the preferred orientation.When the aging temperature increases to 523 K,the size of GBPs enlarges.Microvoids nucleate by interface debonding between GBPs and the matrix which is caused by stress concentration at large GBPs;subsequently,their coalescence and growth result in final fracture.Otherwise,smoothing facets on the fracture surface form by microcracks propagating along the interfaces between twins and the matrix,and this tendency is intensified due to the existence of GBPs.When the aging temperature increases,the smoothing facets reduce as the twins and GBPs decrease and the slip deformation intensifies.
Abstract: Ni-P alloy particles were synthesized by means of pulse discharge in nickel salt solution.The microstructure characterization and crystallization behavior of the particles were investigated using field emission scanning electron microscopy (FESEM),transmission electron microscopy (TEM),X-ray diffraction analysis (XRD) and differential thermal analysis (DTA).The results show that the particles exhibit the morphology of a dendrite-like and chain-like combination,with the diameter of up to about 500 nm and the length of several microns.Their structure is amorphous and maintains at temperatures lower than 280 ℃,but begins to crystallize into metastable phases Ni5P2 and Ni12P5 at 300 ℃.Ni and Ni3P stable phases appear at 320 ℃,and the metastable phases disappear above 400 ℃.The crystallization activation energy is 291.76 kJ·mol-1 determined by the Kissinger equation.
Abstract: High-purity iridium matrixes used in spectral analysis were developed to meet the request of the new national standards to iridium standard samples.The technological flow of high-purity Ir matrixes for spectral analysis was determined through experimental study.The process was comprised of removing base metal cations by P204 solvent extraction,removing precious metal impurities in the form of complex anions by N235 solvent extraction,removing Rh and other metal impurities by H2 reducing in solution,removing trace base metal cations by 732# exchange resin,precipitating Ir by NH4Cl,reducing Ir by H2,and removing Si by HF.The grade of high-purity Ir matrixes is up to 99.999%.In the course of experimental study,the direct recovery rate and the total recovery rate of Ir are 61.99% and 95.26%,respectively.
Abstract: Based on a modified Archard wear model,the effects of process variables,such as ram speed,initial billet temperature,friction factor and die angle,on the die wear during hot extrusion of corrosion-resistant nickel alloy (Hastelloy G3) tubes were investigated by using DEFORM-2D software.The results show that the wear concentrates on the die exit.The maximum wear depth of dies decreases with increasing ram velocity and billet temperature,but it increases with increasing friction factor.The wear depth on the die surface increases with increasing die angle.Under the optimal extrusion process variables of the ram velocity of 200 mm·s-1,the initial billet temperature of 1 180 ℃,the friction factor of 0.05 and the heat transfer coefficient of 5 N·mm-1·s-1·℃-1,the maximum wear depth of dies was 0.051 5 mm and the die can be reused 20 times.
Abstract: The finite element method is applied to quantitatively analyze the effect of double taper roller shape on the waved surface of strips in continuous annealing proeess. According to the simulation results, the waved surface initially oecurs in the strip area on the taper shoulders, at which the tensile stress and transverse stress experience a dramatie ehange, and the transverse compressive stress and equivalent stress have the largest values in the area. This finding is consistent with the real case. The occurrence probability of waved surfaces enlarges with the total taper-to-taper ratio increasing as well as with the length and diameter of the roller's flat section decreasing. Among the faetors, the length of the flat section has the most significant influence on the waved surfaee of strips, then the total taper and the taper ratio, and finally the diameter of the flat section.
Abstract: In order to meet the requirements of high-speed elevators, a mathematic model of straightening process for elevator guide rails was built on the basis of elastoplastie mechanics. The relationship between deflection and bending moment and the relationship between curvature and the neutral layer were presented and can be used to calculate the deflection of straightening process. With the theoretical support, finite element software ANSYS was used to verify the rationality of the solutions and satisfactory results were obtained.
Abstract: With samples acquired from different temperature zones in a blast furnace (BF),the erosion mechanism of linings was investigated in thermodynamics and micro-mechanism by thermodynamic calculations,SEM and EDS.The results indicate that bricks are penetrable for the steam of K,but Na penetrates in bricks by airflow mixed with Na compounds.Zn has a larger effect on lining erosion in middle and low temperature zones but much less in a high temperature zone.
Abstract: The manufacturing flow of steelmaking and continuous casting is a complex multiple-phase and multiple-product production process.The production scheduling problem in this manufacturing flow can be seen as a job shop scheduling problem.An improved genetic algorithm for solving this problem was proposed and the improved aspects were as follows:rank-based fitness assignment,job filter order-based crossover operator,and mutation rate according to an exponential function relation.Twenty-four benchmarks were comparatively investigated and the result shows that the improved genetic algorithm has a better capacity of seeking optimum than a traditional genetic algorithm.The production scheduling problem of steelmaking and continuous casting with sixteen plans and six procedures was computed using the improved genetic algorithm.It is shown that the algorithm is effective.
Abstract: A three-layer emotion model structure based on brain science was proposed firstly.Then a bottom-level emotion model of the intelligent system was presented in detail.It was constructed by using fuzzy mathematics and matrix description of finite state machines.A fuzzy relation between stimulus and emotion was produced to determine the active emotion in consideration of mood and desire at that time.The output behavior was calculated by a matrix style of finite state machines while the active emotion was given.The model constructed in this way could reduce memory spaces used only for storing the corresponding relations among stimulus,emotion and behavior.The simulation result and conclusion are presented in the end.
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
