Abstract: Based on complex geological conditions in Huize Lead Zinc Mine,a digital 24-channel microseismic monitoring system was established to monitor microseismic events in deep mining.In the monitoring period,microseismic parameters were recorded such as b values,magnitude and the number of microseismic events.The relation of Df =2b was deduced between capacity dimension Df and b values.After analyzing the monitoring data,the changes of Df values with time and stope collapse were determined.The results show that rockmass failure is closely related with Df values.With the change of mining disturbance,the stress concentration of local rockmass induces crack compaction,initiation and propagation,meantime the Df values increase and then stay relatively quiet,meaning that the crack roughness of rockmass is increasing.Once dynamic disasters are caused by rock mass failure,the Df values abruptly decrease,which means that the crack roughness of rockmass reduces and it leads to the acceleration of rockmass instability.Combining with site examination,it is concluded that the probability of rock failure increases with decreasing Df values.
Abstract: In allusion to the fuzzy and uncertain information of sublevel openstope succedent filling method in practical engineering,some factors such as mining safety,economy and technology were taken into account and scenario optimization of the corresponding synthetic evaluation system was established by analytic hierarchy process(AHP).Then,the fuzzy mathematics method was also applied to optimize each scheme parameter and assess the weight of quantitative and qualitative indexes.Finally,optimal scheme parameters were obtained by the fuzzy matrix,thereby leading to mining safety and high efficiency mining.
Abstract: Reverse flotation was employed to separate quartz from a phosphate ore with fine particle size which contained siliceous and carbonates gangues.The P2O5 grade and recovery were higher than those by direct flotation,especially the P2O5 recovery increased by about 40%.Compared with ether amine salts and quaternary ammonium salts,alkyl amine salts exhibited better flotation results,the P2O5 grade of concentrates and the quartz removal ratio were higher than 30% and 60%,respectively.Acid reagents were more propitious to improve the grade of the siliceous-calcareous phosphate ore than alkaline reagents.Because of the existence of carbonate minerals,a strong acidity condition was more beneficial to separate quartz by reverse flotation.The application of phosphoric acid as a phosphate depressant and pH modifier gave a better usability in comparison with sulfuric acid,and the dosage of phosphoric acid was less than that of sulfuric acid.The optimum collector dosage was 0.5 to 1kg·t-1.The three cationic collectors adsorbed on ore surfaces in physical adsorption,and the adsorption of alkyl amine salts was the strongest,which is likely to explain their preferable flotation performance.
Abstract: GP193G75,a newly developed refined tall oil supplied by Georgia-Pacific Chemicals LLC,was investigated as a collector for the flotation of phosphate ore from CF Industries' phosphate rock mine in Florida.Its adsorption on the surface of hydroxyapatite was characterized using a quartz crystal microbalance with dissipation(QCM-D) in comparison with sodium oleate and the plant collector of CF Industries(PR1) which was the mixed crude tall oil fatty acid.The effect of the new collector GP193G75 on phosphate flotation was evaluated at different process parameters such as collector dosage,pH values,diesel dosage and flotation time.The results show that the highest recovery of 91.7% is achieved when the refined tall oil is used at the dosage of 0.45kg·t-1 at pH 10 with a 9∶8 mass ratio of fatty acid to diesel.The data of QCM-D show the similar adsorption process with GP193G75 and sodium oleate,and GP193G75 adsorbs on hydroxyapatite more readily and quickly than sodium oleate.In comparison with PR1,GP193G75 forms a higher adsorption density and a more rigid adsorption layer,which produce a stronger hydrophobicity and a better flotation performance.
Abstract: 10 strains,capable of degrading and decolorizing bromamine acid under high salt conditions,which is an intermediate of anthraquinone dye,were isolated from the biomembrane of a bio-contact oxidation tank.A strain named C-7 which has good decolorizing effect and stable decolorization ability was obtained by acclimating the 10 strains.It was identified as Citrobacter freundil.Salt tolerance test results show that the strain C-7 can grow with a decolorization rate of more than 80% when the mass fraction of NaCl is 1% to 3%,and NaCl has no effect on the growth and decolorization of the strain.When the mass fraction of NaCl is 7%,C-7 show high tolerance and the decolorization rate is more than 50%.NaCl can inhibit the growth of the strain C-7 and bromamine acid cannot be degraded when the mass fraction increases to 10%.Under the optional growth conditions of pH 7.0,the rotating rate of 160r·min-1,the liquid volume of 120mL in a 250mL flask,inocula of 10% and peptone of 7g·L-1 as the only nitrogen source,when the mass fraction of NaCl is 1%,the decolorization rate of bromamine acid(100mg·L-1) can reach to 85% or higher.
Abstract: The theoretical flame temperature before the tuyere in a blast furnace(BF) is one of the important parameters to measure the thermal state of the hearth.However,it is ignored that SiO2 reduction before the tuyere can impact the theoretical flame temperature.The coke temperature entered the raceway and the SiO2 content at different locations before the tuyere in the BF were obtained by studying tuyere-level samples from the BF.And then the reduction rate of SiO2 before the tuyere was determined and the theoretical flame temperature formula with regard to the effect of SiO2 reduction was established.Finally,under the condition of pulverized coal injection(PCI) and oxygen enrichment,the effect of changing the ash content in coal on the theoretical flame temperature was analyzed and discussed.
Abstract: The reduction degrees of ultra-fine hematite powder(the average particle size is 2μm) and conventional hematite powder(the range of particle size is 0.18 to 0.154mm) in non-molten process were studied.Taking the reduction degree of hematite powder as a target and according to the transformed L16(215) orthogonal table,a series of 4×23 times experiments were arranged to eliminate the interference of reduction atmosphere,reduction temperature and reduction time.The results show that ultra-fine hematite powder can be reduced from Fe2O3 to Fe at different degrees.Compared with conventional particle size hematite powder,ultra-fine hematite powder has a higher reduction degree,and the reduction temperature required to access the same reduction degree lowers about 365 ℃ under the condition of 650 to 850 ℃ and pure H2 or 100% CO atmosphere.There is no correlation among these factors,the quantitative impact of them can be separately estimated,and this provides a basis for establishing an equation of linear regression for each of them.After reduction at non-molten state,the particle size distribution of hematite powder indicates that inter-particle sintering does not occur and the reduction product is still powdery.
Abstract: The morphology and chemical composition of inclusions were analyzed with experiment in molten steel deoxidized by Al after Ti deoxidation;the structures and mechanical properties of this steel were also studied.It is shown that the type of inclusions in the steel is mainly titanium oxide when the mass fraction of aluminum is 0.015%.Titanium oxide could promote the formation of acicular ferrite which refines the microstructure of the steel.Compared with the steel without Al deoxidation,the impact toughness of the steel deoxidized by Al increases by 33%,proving the feasibility of final aluminum deoxidation.
Abstract: The melting point of titanium-containing steel slag was theoretically calculated using the Phase Diagram module and the Equilib module of thermodynamic calculation software FactSage,and the calculation result was verified by melting experiments.It is shown that,for a slag system with the basicity below 1.5,when the mass fraction of TiO2 is less than 13%,TiO2 has little effect on the melting point of the slag,and while the mass fraction of TiO2 is over 13%,TiO2 can increase the melting point.For a slag system whose basicity is over 1.5 and mass fraction of Al2O3 is between 25% and 35%,when the mass fraction of TiO2 is more than 1%,TiO2 can significantly increase the melting point of the slag.
Abstract: A surface Widmanstätten microstructure is the principal cause of cracking of 35K wire rods during cold heading.To control the surface Widmanstätten microstructure,heating time and soaking temperature in a heating furnace were simulated in the laboratory.And then plant trails of rolling process temperature were conducted according to the laboratory studies.The results showed that the microstructures of wire rods were uniform and the grade of surface Widmanstätten microstructures was less than 1 under the conditions of the soaking temperature from 1160 to 1230℃,the heating time from 80 to 90min,the finishing rolling temperature from 820 to 840℃ and the laying temperature from 800 to 820℃,which could effectively prevent the cracking in the process of cold heading.
Abstract: A relationship between internal friction(IF) and microstructures of high silicon martensitic hot working die steel(SDH3 steel) which contains 1.5% silicon was researched.The experimental steel was annealed at 1060℃ for 30min,quenched into oil and tempered at different temperatures.The temperature dependence of internal friction(TDIF) was measured with a vibrating-reed apparatus by free decay method within the temperature range from room temperature to 750℃.It is shown that two types of relaxation IF peaks,Snoek peak and SKK peak,have been observed at TDIF curves of the steel.The height of IF peaks drops and the peak position shifts as the tempering temperature rises.When the tempering temperature is above 650℃,the IF peaks disappear completely and only background IF can be observed.As the tempering time is prolonged,both the peak height and peak position change,and then these changes have been discussed on the basis of diffusion-controlled redistribution.
Abstract: In order to reduce the internal stress of a P110 oil casing during quenching,an optimized cooling process "water-quenching→air-cooling→water-quenching" was proposed.The change and distribution of temperature and stress field of the casing during cooling process were simulated by finite element method.The simulated results show that the maximum temperature difference is 104℃ after water-quenching for 7.5s,and the distribution of cross-section temperature is uniform at the end of air-cooling.When the casing is quenched by water again,the temperature difference is 80℃,which is 24℃ lower than that of 7.5s.For the stress,at the first water-quenching stage,the tangential stress increases from the beginning to 2.5s and then decreases form 2.5 to 5.5s.At 5.5s phase transformation occurs.After that there are both thermal stress and structural stress in the casing,hence the tangential stress increases sharply and peaks at 563MPa at 7.5s.At the air-cooling stage,as the thermal stress decreases and the structural stress disappears,the distribution of tangential stress becomes uniform and levels off at-11 to 27MPa at the end.When the casing is quenched in water again,the tangential stress increases and reaches the peak again at 451MPa at 13.6s,which is 112MPa lower than 563MPa at 7.5s,thereby optimizing the cooling process.
Abstract: Optical microscopy was used to analyze the microstructures of AF1410 steel welded joints after being electron beam welded.The corrosion resistant performance and the electrochemical behavior of the melting area and the base metal were also analyzed using the neutral salt spray corrosion weight loss and electrochemical testing methods.The results show that there are the thick tempered martensite and the precipitated carbides on the electron beam welding seam,and the corrosion weight of the base metal is less than that of the melting area.Electrochemical testing results indicate that the open circuit potential of the melting area is lower,the corrosion current is higher and the impedance is also lower than that of the base metal,and the melting area is more susceptible to corrosion.This is due to the electrochemical reaction driven by the potential difference between the tempered martensite and the carbide precipitation,which causes the corrosion failure of the material in the corrosion medium.
Abstract: A self-developed taper barrel rheomoulding(TBR) machine for preparing light alloy semi-solid slurries was introduced.Relative rotation of the internal and external taper barrel whose surface contains wales and grooves led to an intense shearing turbulence of alloy melts during solidification,and then the semi-solid slurries were prepared.A heat transmission model of TBR process was deduced.Taking A365 aluminum alloy as an experimental material,the related formula between slurry temperature(Tout) and pouring temperature(Tp) of the alloy was obtained.The cooling rules of the alloy melt and the semi-solid microstructure at different pouring temperatures were analyzed.The results show that properly decreasing the pouring temperature of A365 alloy melt can increase the shearing time and shearing frequency for the primary solid phase,thereby obtaining a fine and homogeneous semi-solid microstructure.When the pouring temperature is 640℃,the average grain size of primary particles is 68μm and the shape factor is 0.82.
Abstract: An investigation was conducted on the creep behavior and microstructure of a Ni base single crystal superalloy with [001] orientation during creep deformation.The results show that the test samples exhibited a lower steady creep rate and a longer creep life under the higher temperature and stress level.Under the condition of 700℃ and 720MPa TEM observations indicate that $\frac{1}{2}<110> dislocations move in the matrix and react to form the Shockley segments of $\frac{1}{3}<112> dislocations,which cut into the γ' phase and form stacking faults in the precipitates.Under the condition of 900 ℃ and 450MPa,the primary creep stage does not appear.The morphological evaluation of the γ' phase develops from original cubic to raft microstructure.Multiple slip operates and dislocations shearing the γ' phase is the main deformation mechanism during the creep acceleration stage.Under the condition of 1070 ℃ and 150MPa,it is found that the γ' phase gradually changes into raft microstructure,hexagonal dislocation networks appear on the γ/γ' interface,and the regular and dense dislocation networks can inhibit dislocations cutting into the γ' phase and enhance the creep resistance.In the later creep stage,the main deformation characteristic is that the γ' phase is sheared by dislocation pairs.
Abstract: Carbides in new type Hf-Ta-containing nickel-based superalloy FGH98 Ⅰ powders prepared by plasma rotating electrode processing(PREP) before and after pre-heat treatment at different temperatures were studied.The results show that MC' type carbides in the initial powders can be divided into two groups.One is rich in Ti,Ta,Nb and the other contains the elements of Ta,Hf and Zr.The two types of carbides both contain a certain amount of non-carbide forming elements(Co,Ni) and medium carbide forming elements(Cr,Mo),and these carbides locate between interdendrites or cells and in block and granule shapes.Ti-Ta-Nb riched MC' type carbides in the powders can be transformed into MC type carbides and the total amount of Ti-Ta-Nb increases with increasing pre-heat treatment temperature.The Ta-Hf-Zr contained MC' type carbides can be decomposed and transformed into M23C6,M6C and MC type carbides.It is also shown that the precipitate and dissolution temperatures of M23C6 type carbides are 950℃ and 1150℃ respectively,and the co-existing temperature of M23C6 and M6C type carbide is within the range from 1000℃ to 1100℃.In addition,trance elements Hf and Ta in the powders take part in the reactions of carbides mainly in the form of carbides and γ' phases.
Abstract: In order to develop a new heat-spreading material used as heat sink,diamond/Si composites were synthesized by a high-pressure high-temperature(HPHT) method.An investigation was conducted on the effects of diamond particle size,diamond content,siliconizing process,and coating Ti on diamond particles on the density and thermal conductivity of the composites.The results show that mixing large and small size diamond particles,coating Ti and siliconizing process are effective to improve the density and thermal conductivity of diamond/Si composites.The thermal conductivity rises with the content of diamond increasing.When the mass fraction of diamond blended by 75/63μm Ti-coated diamond particles and 40/7μm diamond particles is 95%,the thermal conductivity of the composite sintered at 4~5GPa and 1400℃ by the HPHT siliconizing method can reach to 468.3W·m-1·K-1.
Abstract: Considering the influence of mechanical factors and combustion reaction in a blast furnace on the tuyere raceway,two mathematical models,a static model and a dynamic model,were proposed in order to describe the penetration and variation rules of the raceway.Simulated results show that the static model is able to predict raceway penetration accurately,and the dynamic model can describe the dynamic process of raceway penetration with time when the blast velocity changes.Finally the formation and variation rules of the raceway are concluded as the following:the fast movements of the packed bed driven by blast pressure make the raceway size vary rapidly and then the raceway prototype is formed.In addition,combustion reaction repairs the size and shape of the raceway so as to maintain a stable raceway.In the entire change process of raceway size,frictional forces are proved to play an important role for raceway stability.Predictions of the mathematical models are in reasonable agreement with the measured data of blast furnaces and other researchers' experimental results.
Abstract: Based on the constitutive relationship of IN690 alloy obtained by isothermal compression,a finite element model of hot extrusion was established for IN690 alloy tubes.In the model the heat conduction between the billet and the die,the convection of heat transfer,and the thermal conversion of plastic work and friction work were taken into account.Simulation results show that the billet temperature starts to rise when the billet approaches toward the deformation zone and increases rapidly when coming into the deformation zone,and the temperature peaks at the die hole's outlet near the mandrel.Besides,the billet temperature around the mandrel is higher than that beside the container.The temperature rise reaches the peak at the end of the filling extrusion stage.The influence of process parameters on the outlet temperature was analyzed.It is indicated that the outlet temperature increases with extrusion speed and reduces seriously when the extrusion speed slows,but the rise of outlet temperature decreases when the preheating temperature of the billet increases.When the friction coefficient is less than 0.04,the friction coefficient has little effect on the outlet temperature,but if the friction coefficient becomes greater than 0.1 the exit temperature will significantly increase.
Abstract: Combined compliant structures were classified and the conditions of non-linear deflection of the flexible beam in a combined compliant structure were given on the basis of the effect of structural parameters on the deflection characteristic of combined compliant structures.In consideration of the variable cross-section and the non-linear deflection of a compliant structure,the deflection characteristic of the compliant structure was studied and a non-linear compliant-body model used for deflection analysis was established.Finally a combined compliant structure formed with flexible hinges and a flexible beam was designed and machined,and its deflection was analyzed by pseudo-body modelling,imitate-compliant body modelling and non-linear compliant-body modelling.Meantime,the deflection caused by electrostatic drive was tested.The results show that,the calculated data with the non-linear compliant-body model is most similar to the test results,proving the validity of this model and the analytical method.
Abstract: The effect of pressure equalizing processes in vacuum pressure-swing adsorption on concentrating the methane in coal mine gas was studied experimentally.The results show that pressure equalization can increase the pressure of the absorber rapidly,and raise the adsorption pressure and methane content.The optimal pressure equalizing process is equalizing the pressure at both the inlet and outlet ends of the absorber.After pressure equalization at the inlet end for 0.2s and the outlet end for 0.4s,the methane concentration of the desorbed gas reaches maximum.In the meantime there is still a pressure difference between two absorbers.The energy consumption of raising the pressure from different equalizing pressures to a certain adsorption pressure was analyzed.The energy consumption is decreased by 31% when the equalizing pressure increases from 93.8kPa to 120.4kPa.
Abstract: The thickness and tension system in tandem cold rolling has the features such as multivariation,strong coupling and uncertainty.To improve its control accuracy and quality,a new robust control scheme based on the invariance-decoupling theory and H∞ mixed sensitivity method was presented.First,a dynamic coupling model for the thickness and tension system was built,and the invariance-decoupling theory was applied to completely decouple the thickness and tension system.Then,for systematic uncertainty of modeling error,parameter perturbation and external disturbance,a robust controller was designed based on H∞ mixed sensitivity method to ensure the robust stability and robust performance of the system.Simulation results show that the thickness and tension system after decoupling is controled better,proving the validity of the algorithm.
Abstract: A differential evolution algorithm based on multi-swarm and sub-objective optimization is presented in order to solve the difficulty in selecting the weighting coefficients in processing the objective function of hot strip mills.Each sub-swarm optimizes a sub-objective and evolves independently.This not only solves the issue of weighting coefficients,but also increases the convergence speed and accuracy.Finally,the algorithm's effectiveness is verified by simulation.
Abstract: On the basis of the decomposition model of energy consumption index,the energy consumption per ton steel in main processes was forecasted and analyzed by using scenario analysis.In order to evaluate the energy consumption of a domestic steel plant in 2009 and 2012,scenarios which respectively considered feasible lowest process energy consumption(FLPEC),feasible and possible waste heat reusing technologies were built.In the feasible scenario,only the waste heat of high-temperature flue gas in sintering,hot and cool-rolling processes was recoverable,while the heat recovery of flue gas and solid in every process was considered in the possible scenario.Through comparing these scenarios,it is concluded that the energy saving effect of the FLPEC scenario is the best,and the feasible technologies have little effect while the possible technologies can reduce energy consumption significantly.Finally,some suggestions for further energy saving work are proposed,such as applying advanced preheating technologies in electric arc furnaces,developing high-temperature solid heat recovery technologies and improving the waste heat recovery in rolling process.
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
