Abstract: The plastic criterion popularly used in slope stability analysis is the Mohr-Coulomb criterion.A formula based on the basic principles of the Hoek-Brown failure criterion and the Morgenstern-Price scheme was deduced.The disadvantage that data are empirically obtained in slope stability analysis is overcome by adopting this method and the computing results are more accurate and reasonable.An example was discussed to compare the slope stabilities with different failure criteria,and the stability analysis of Anjialing open-pit mine slope was carried out by using the Morgenstern-Price scheme based on the Hoek-Brown criterion.
Abstract: The effect of pre-oxidation on the reduction behavior of Panzhihua ilmenite was studied.The results show that pre-oxidation can speed up the reduction rate of ilmenite iron oxide and improve the iron metallization rate of reduction products.The action mechanism is that new phases of shame rutile,ferric oxide,rutile,and trivalent pseudobrookite formed in the pre-oxidation process of ilmenite,which destroyed the structure of original minerals and formed plenty of pores in the granule interior.It would be beneficial to enlarge the specific surface area of the granule and improve the gas diffusion in reduction process.Also after pretreatment of oxidation,new phases formed in pre-oxidation process would be re-reduced,neonatal ilmenite has high activity,and the microstructure of reduction products is improved.
Abstract: Industrial heap bioleaching tests of 300 t Cu and 1000 t Cu per year were done for low-grade copper sulfide ore bearing arsenic from Zijinshan Copper Mine in Fujian Province,China.The results of the industrial tests indicate that the copper leaching rate increases with the decrease of ore grain size and the leaching rate of 80.58% is obtained during the leaching cycle of 270 d at the particle size of -30 mm.The copper extraction rate and electrowinning current efficiency reduce with the decrease in pH values of the pregnant leaching solution and the increase in mass concentration of iron ions in the electrowinning solution.The copper extraction rate declines to 50% when the pH value of the pregnant leaching solution fells to 1.19.After the innovation process,such as raise of heap height,periodical neutralisation of raffinate solution,load increase of organic phase scrubbing,and removing organic matter from the electrowinning original solution with activated carbon,sand filtration and air flotation column,the consumptions of extractant,kerosene and electrical energy drop and the copper leaching rate is enhanced.The copper leaching rate of 81.31% and the cost of RMB 10500 per ton high-purity cathode copper were gained during the leaching cycle of 200 d with the power consumption of 2 679.98 kW·h·t-1.
Abstract: The effect of argon purging site and argon flow rate in a tundish,in particular argon purging in injection flow area,on steel cleanliness was investigated by field test.The results show that bubbling at injection flow area with suitable argon flow can improve steel cleanliness,while bubbling at the corner site in casting area and nearby the stopper has no obvious effect on steel cleanliness.The suitable argon flow rate is 6 L·min-1 when purging at injection flow area,and compared with no argon bubbling,the removal rate of total oxygen and inclusions in steel can be decreased about 10%.But large argon flow with 15 L·min-1 will obviously increase total oxygen and inclusions in steel.Inclusions removal in the argon purging tundish may be explained as that when argon purging at injection flow area,bubbles will be smashed into a smaller size by the strong turbulence intensity.A large number of diffusive bubbles in molten steel not only accelerate the collision between inclusions,but also increase the probability of bubbles to capture inclusions,which result in the increase of inclusion size and accelerating inclusions floating up and being removed.On the other hand,the distance from injection flow area to the tundish nozzle is the longest,and when argon purging at injection flow area,the grown-up inclusions have the longest time to be removed from steel.These two factors make purging at injection flow area have significant impact on inclusions removal.
Abstract: The reoxidation mechanisms of IF steel containing Al and Ti by reducible oxides in the slag were analyzed.A model of predicting total oxygen in the molten steel was established based on the reoxidation mechanisms.It was found that two different reaction mechanisms existed when(FeO) and(MnO) in the slag reoxidated the molten steel.Reoxidation occurred at the slag/steel interface when mass transfer of reducible oxides in the slag dominated the reaction,and the oxidability of the slag exponentially declined with prolonging time.When mass transfer of de-oxidative elements in the molten steel dominated the reaction,reoxidation carried out in the molt steel.A specific formula between the oxidability of the slag and time was obtained by regressing the data from a steelmaking plant.
Abstract: In order to investigate and control the precipitation behavior of titanium carbide in Ti-steels produced by thin slab casting and rolling(TSCR),the structure and orientation relationship of TiC and Ti2CS were studied by transmission electron microscopy(TEM).The results show that in the experimental steels Ti2CS precipitates at relatively higher temperature than TiC.Ti2CS precipitated previously can act as heterogeneous nucleation sites for TiC.Many tiny TiC particles grow from Ti2CS.The results of electron diffraction and X-ray energy dispersive spectroscopy show that the orientation relationship between TiC and Ti2CS is {001}Ti2CS∥{111}TiC,〈100〉Ti2CS∥〈011〉TiC.There are also some titanium carbide particles with twinned structure in the steels and the twinning plane is(111).Therefore,the previous precipitates,either Ti2CS or TiC,can provide preferential sites for latter TiC nucleation.Both of the twinning and epitaxial growth are important mechanisms for precipitation of titanium carbide in the TSCR steels.
Abstract: The static recrystallization behavior of deformed austenite in X80 pipeline steel with heavy thickness manufactured by the 2160 Hot Continuous Rolling Production Line in Shougang Qiangang was investigated by double hit compression experiment.According to the results,the production technology was improved and optimized.The mechanical properties of X80 pipeline steel obtained by the optimized production technology were tested using tensile,impacting and drop weight tearing tests(DWTT).The microstructure was observed and analyzed using optical microscope(OM),scanning electron microscope(SEM) and transmission electron microscope(TEM).It is shown that deformation temperature is the main factor that influences the static recrystallization behavior.Carbonitride precipitation inhibits recrystallization and causes a plateau in the softening ratio curve.The static recrystallization activation energy of X80 pipeline steel was regressed and calculated to be 380 kJ·mol-1,and its rationality was also discussed according to previous references and investigations.After the technology optimization,the microstructure of X80 pipeline steel is uniform and refined,and represents typical acicular characteristics.Precipitates in the steel mainly include the complex(Ti,Nb)(C,N) and single NbC particles.The tensile properties of X80 steel(tested with bar specimens) exceed relevant standards a lot;especially the toughness at low temperature such as impacting and DWTT properties is excellent.
Abstract: By investigating the change in yield ratio and microstructure of X65/X70 pipeline plates at different finish rolling temperatures and final cooling temperatures,it is found that the microstructure has band structure and the amplitude of high yield ratio is greater than that of tensile strength when the finish rolling temperature is below the Ar3 temperature and the plate is rolled in the two-phase zone.Overcooling at the head of the plate is not beneficial to low yield ratio.By optimizing the processing parameters,the yield ratio of X65/X70 pipeline steel reduces obviously and the qualified rate of products increases greatly.
Abstract: The relationships among textures,phase distribution and corrosion resistance of hot-dip galvanized coatings were investigated with X-ray diffraction and potentiodynamic techniques.Experimental results indicate the major texture component of pure zinc phase in the galvanized coatings is {0002} basal texture.As the thickness of the galvanized coatings increases,the {0002} basal texture component as well as the free corrosion potential increases,the corrosion current density decreases,and the corrosion resistance of the galvanized coatings increase.X-ray diffraction analysis results of an electrochemical stripping Fe-Zn phase coating show that the galvanized coatings are composed of alloy phases and pure zinc phase.Electrochemical experiments indicate the corrosion resistances of alloy phases and pure zinc phase are different,the corrosion resistance of alloy phases is higher than that of pure zinc phase,and the corrosion resistance of Fe-Zn alloy phase increases with the increase of iron content.
Abstract: Ni-Cr-Mo-Cu-Mx nickel-base corrosion-resistant alloys were prepared by adding Ti and Fe with a manual electro-arc furnace.Intergranular corrosion and pitting corrosion resistances of these alloys were investigated by chemical erosion and electrochemical corrosion techniques(polarization curve methods and cyclic voltammetry).The results showed that the intergranular corrosion resistance of the alloys added Ti increased and the pitting corrosion resistance decreased.Fe addition deteriorated the intergranular corrosion resistance of Ni-Cr-Mo-Cu alloys but improved the pitting corrosion resistance.The electrochemical behaviors and characteristics of intergranular corrosion and pitting corrosion coincided with the results of chemical erosion.
Abstract: The stability and semiconductive property of surface films formed on the β phase model alloy were investigated by means of electrochemical impendence spectroscopy(EIS) and Mott-Schottky approach in solutions containing Cl-.The results indicate that the increase of Cl-concentration may accelerate the formation and active dissolution of the films on the surface of β phase,leading to the deterioration of film stability.This phenomenon can be attributed to the fact that the semiconductive type of the films of β phase is P-type in case of solutions with low Cl-concentration.As P-type semiconducting films are cationic conductor films,it is difficult for Cl-to penetrate in a way of transportation and diffusion.When the Cl-concentration increases,the semiconductive type of the films may turn into N-type where Cl-migrates or diffuses in the films,penetrates through the bottom of the films,causes continuous corrosion of the substrate and finally the surface films break down.
Abstract: Ti-44Al-5V-1Cr-0.3Ni-0.1Hf-0.15Gd(atom fraction,%) alloy that forged by 86% was heat treated to be near fully lamellar microstructure(NFL).The microstructures of the deformed alloy and NFL were investigated.Tensile tests at room temperature,700 ℃ and 800 ℃ were carried out.The results show that NFL consists of lamellar microstructure,β phase that locates at lamellar boundaries,and elliptical Gd-compound that disperses in the matrix.The average grain size of the lamellar is 40 μm.The volume fraction of the lamellar,β phase and Gd compound is 93.73%,5.25% and 1.02%,respectively.The tensile tests indicate that the average tensile elongation at room temperature is up to 4.17% and the tensile strength is 865 MPa.At 700 ℃,the average tensile elongation is 22% and the tensile strength is 643 MPa.Compared Ti-44Al-5V-1Cr-0.3Ni-0.1Hf-0.15Gd alloy with TiAl alloys that contain more β phase,the hot deformability is maintained and the room tensile ductility of the studied alloy is much more elevated.It is due to the lower β phase and Gd-compound of the microstructure.
Abstract: The effects of pulse potential,discharging times,Ni2+ concentration,pH value and rare earth additives(LaCl3,NdCl3) on the conversion ratio of Ni2+ as well as the structure,shape and average diameter of Ni-P nanopowders prepared by pulse discharging in solution were investigated by X-ray diffraction(XRD),field emission scanning electron microscopy(FESEM),and focused beam reflectance measurement(FBRM).It is indicated that discharging energy is the key factor that influences the size of Ni-P nanopowders and the conversion ratio of Ni2+.With the increasing of pulse potential or discharging times,the average diameter of Ni-P nanopowders decreased while the conversion ratio of Ni2+ increased.The real-time monitoring results of FBRM showed that the velocities of nucleating and growing of Ni-P particles during the course of discharging were remarkably higher than those after discharging.The size of Ni-P nanopowders could be reduced by adding LaCl3 or NdCl3 to precursor solution.The average diameters of Ni-P nanopowders were 156 nm at the LaCl3 concentration of 0.1 g·L-1 and 72 nm at the NdCl3 concentration of 0.05 g·L-1,respectively.
Abstract: Ultrafine Mg powders were prepared by resistance heating evaporation and induction heating evaporation respectively.The effects of gas pressure on the productivity and granularity of the powders were systematically studied.The powder structure was analyzed by XRD,TEM and other analysis methods.The results show that the productivity of induction heating evaporation is larger than that of resistance heating evaporation.The productivity decreases and the mean particle size increases with increasing gas pressure.The ultrafine Mg powders are polymorphic,with a chain-ball structure and high purity,and the distribution of particle size is narrow.
Abstract: By using a hydrothermal method,well-aligned SnO2 nanowire arrays were prepared on ITO substrates,which were pretreated by a magnetron sputtering method(MST-substrates).The samples were characterized by X-ray diffraction(XRD),field-emission scanning electron microscopy(SEM),transmission electron microscopy(TEM) and high-resolution transmission electron microscopy(HRTEM).The effects of film-coated methods and annealing temperature on the morphology,size and orientation were studied.The results show that the pretreating methods for substrates have great influence on the morphology and size of the samples.The SnO2 nanowire,nanorod,nanoparticle arrays grow on different substrates,which were pretreated with magnetron sputtering,spin-casting methods and unmodified respectively.It is also found that annealing temperature for the pretreated substrates with magnetron sputtering plays a main role in controlling the orientation of SnO2 nanowire arrays.The orientation of SnO2 nanowire arrays is improved by increasing the annealing temperature.
Abstract: Polyaniline(PANI) nanowires on indium tin oxides(ITO) conducting glass substrates were synthesized by means of a galvanostatic method from an aqueous solution of 1.0 mol·L-1 HClO4 and different concentrations of aniline monomer.The effects of aniline concentration and synthesis time on their morphology and electrochemical performance were systematically investigated.Scanning electron microscopy(SEM) revealed that PANI synthesized in different conditions was a wire in shape with different diameters of 100 to 500 nm.Electrochemical characterization of the PANI electrode was performed in an aqueous solution of 3 mol·L-1 NH4Cl and 2 mol·L-1 ZnCl2 by galvanostatic charge-discharge,cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS).A high specific capacitance of 746.7 F·g^-1 was obtained within the potential range of -0.2 to 0.5 V.
Abstract: Porous cordierite ceramics were synthesized from coal gangue,wasted slide gates and wasted magnesia carbon bricks with graphite,starch and compound additives as pore-forming materials.The relationships between properties and synthesis conditions,such as the type and addition of pore-forming materials and heating temperature,were investigated.The result showed that high-purity porous cordierite was synthesized from coal gangue and used refractories at 1 350 to 1 400 ℃ while the compound additives was used as pore-forming materials and their addition is 15% to 25%.At the addition of the compound additives of 20%,1 350 ℃ and sintering for 3 h,porous cordierite ceramics with homogeneous pores distribution were obtained,their apparent porosity is 44.9%,thermal expansion coefficient is 2.14×10-6 K-1,and softening point load is 1 290 ℃.Because of these good comprehensive performances,all bricks can meet the demands of service at high temperature.
Abstract: Miyun iron ore tailings in Beijing were activated by a mechanochemical method.The influence of mechanochemical effect on the activation of the iron ore tailings was analyzed by means of grain size analysis,X-ray diffraction(XRD),scanning electron microscope(SEM) and infrared radiation(IR) technologies.The iron ore tailings as raw materials were used to produce high-strength construction materials.It is shown that the compressive strength of the produced construction materials in which the overall content of the iron ore tailings is 70% can reach up to 89 MPa.
Abstract: Through analyzing design features of the cooling system above the hearth in TISCO 4 350 m3 blast furnace(BF),the effect of gas flow distribution on the heat load of the blast furnace was studied in the case of high pulverized coal injection rate and high yield.The results of No.5 blast furnace were presented.The value of edge gas flow index W should be controlled at around 0.55,the value of center gas flow index Z should be controlled at around 8.8,and the heat load on the belly and the bosh of the blast furnace is relatively stable but in the upper part of the stack is bad.There is a potential to reduce the heat load of No.5 blast furnace.When the heat load is controlled in the range of 10 to 120 GJ·h-1,the 4 350 m3 blast furnace can still be stably operated.
Abstract: In order to meet the need of width control precision for a 1580 hot strip mill and to improve the applicability of width spread models,the process of edge rolling-horizontal rolling in the rough rolling area was simulated by the finite element software ANSYS/LS-DYNA.The effects of width,thickness,roll diameter,reduction in width and reduction in thickness on ‘dog-bone’ width spread,natural width spread and absolute width spread were studied.The FES models of ‘dog-bone’ width spread and natural width spread were established with simulating data and field data,and the PSO-BP neural network was founded.At last,the FES width spread models were combined with the PSO-BP neural network to predict the width spread of the first,third and fifth pass.The percentage of the case that the error between predicted data and the measured values is less than 1 mm was more than 99%,and the width control precision was satisfied.
Abstract: A rotation formula which indicates the big end radius of the spiral declined cone changing with the rotation angle of rolled pieces for an elliptical shaft was proposed according to the process characteristics of cross wedge rolling.The volume formula for each stage was obtained by analyzing the shaping process.The shaping curve of the right-angle step in cross wedge rolling was derived from the volume balance principle.Finally,the shaping process of the elliptical shaft was simulated with the rigid-plastic FEM software Deform-3D.Excellent simulation results verified the correctness of the shaping curve.
Abstract: The cross wedge rolling deformation process of hollow shafts with equal inner diameter was simulated with the three-dimension finite element software DEFORM-3D by using a thermomechanical coupled rigid-plastic finite element method.The distributions of stress,strain and temperature fields inside the rolled-piece during the rolling process were analyzed.The reasons for cross-section ovalization in the rolled piece,shaft shoulder apophysis on the outside surface and depression on the inside surface around the sidestep were revealed.The change in temperature of the rolled piece in the rolling process was illustrated and the reason for the change was explained.Simulation results indicate that it is feasible to produce hollow shaft parts with equal inner diameter by cross wedge rolling.
Abstract: A local feature based approach was proposed for ear recognition under partial occlusion.Firstly,the Gabor filter is applied for feature extraction.Because the Gabor feature vector is of high dimension,kernel Fisher discriminant analysis(KFDA) is used for dimension reduction as well as class separability enhancement.Based on investigations on the different discriminating ability of sub-regions in ear images,a sub-region and probability based model is proposed for recognition.Experimental results on the USTB ear image database show that ear recognition based on the features extracted from Gabor filtered images performs better than that based on the features extracted from the original images,and the local features based strategy gets a higher recognition rate than the whole image based strategy for recognition.
Abstract: Based on the theory of sandy soil liquefaction,the working principle of impact compaction on silty fine sand ground was analyzed and the mechanics was put forward.An industrial trial was carried out on silty fine sand ground in Caofeidian District of Shougang Group,and the results and effects indicate that it is absolutely feasible to use this technology in this kind of situation.
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
