Taken an open pit mine's slope as the engineering background, based on the unified strength theory, different strength criterions were approximated by adjusting the two constitutive parameters of b and α, and a userdefined constitutive model was constructed, which was suitable for actual working conditions. After drawing up the improved strength reduction rule, the slope safety factor was computed by reducing the related strength parameters. Compared with the traditional strength reduction method based on the Mohr-Coulomb strength criterion, which ignoring the effect of intermediate principal stress, this improved strength reduction method overcomes the defect of calculated results being too conservative.
Abstract: This paper reports the influence of different combinations of reductants and calcium salt desulfurizers on desulfurization of pyrite cinder in direct reduction roasting process. The roasted ore obtained at different conditions was analyzed by X-ray diffraction and scanning electron microscopy. It is found that pyrite and forsterite in pyrite cinder react with different kinds of calcium salt desulfurizers in the high-temperature and reducing atmosphere to form metallic iron and different sulfur-bearing minerals, calcium sulfide or jasmundite. The sulfur-bearing minerals can be removed from the roasted ore through grinding and magnetic separation, thereby reducing the sulfur content. Different intergrowths between sulfur minerals and metallic iron in the roasted ore formed by different combinations of reductants and calcium salt desulfurizers make the contents of iron and sulfur in direct reduction iron have different change laws. With different combinations of reductants and desulfurizers, the sulfur minerals and their intergrowth with metallic iron in the roasted ore are also different.
Abstract: This paper reports the phosphorus removal of high phosphorus oolitic iron ore by acid leaching and its influence factors. The experimental ore is Exi high phosphorus oolitic iron ore with 0.5% phosphorus, 51.7% iron and 0.34% sulphur. After acid leaching, the P content decreases to about 0.07%, the iron loss during acid leaching is about 0.18%, and the S content is 0.35%, which can meet the requirements of steel production. Through analyzing the ore surface before and after acid leaching by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), it is found that apatite is almost completely dissolved, but iron oxide phase hardly reacts, which is also proved through thermodynamic calculations. The optimal experimental parameters are determined to be the leaching time of 1 h, the liquid-solid ratio of 100 mL:8 g, the acid concentration of 0.2 mol·L-1, and the oscillation frequency of 150 Hz. Micro cracks appear in the ore by microwave preheating, the specific area of the ore is increased, but little improvement in dephosphorization is induced during acid leaching. The recycling of the waste acid solution is feasible. Through adding fresh acid to the waste acid solution, the acid solution after treatment can leach phosphorus to the satisfied extent again. The dephosphorization rate is controlled at 80%. The recycling can reduce the cost obviously and protect the environment.
Abstract: The viscosity of molten iron containing titanium was measured with a oscillating cup viscometer at elevated temperatures. The effects of titanium and silicon on the viscosity, viscous activation energy, solidification temperature, and solidification rate of molten iron were studied during the cooling process. It is found that there is little difference in viscosity among molten irons containing different contents of titanium above the solidification temperature, and their viscous activation energies change in the range of 37.07 kJ·mol-1 to 44.03 kJ·mol-1. There is great influence upon the solidification temperature and solidification rate by adding titanium into molten iron, and the higher the titanium content, the higher the solidification temperature and solidification rate. Low silicon content is the main reason for low solidification temperature of molten iron containing V and Ti.
Abstract: The effect of rare earths on the dynamic recrystallization behavior of T91 heat-resistant steel under different deformation conditions was investigated on a Gleeble-1500 thermo-mechanical simulator. The true stress-strain curves, recrystallization-temperature-time (RTT) map, dynamic recrystallization map and power dissipation map were drawn for the steels with and without rare earths. The recrystallization activation energies of these two kinds of steels at elevated temperatures were also calculated in this paper. It is found that under the deformation condition of the temperature of 850 to 1100℃ and the strain rate of 0.004 to 10 s-1, dynamic recrystallization happens at higher temperatures and lower strain rates. Rare earths dissolve in the matrix, resulting in solid solution strengthening. Rare earth elements interact with carbon and segregate at grain boundaries or around the matrix, leading to the increasing of peak stress and peak strain as well as the improvement of recrystallization activation energy from 354.6 kJ·mol-1 to 397.2 kJ·mol-1. In addition, rare earths delay the starting time of recrystallization greatly, extend the time interval of recrystallization, and postpone the recrystallization kinetic process.
Abstract: Based on solubility product calculation and thermal simulation experiments, precipitated phases in continuous casting slabs of non-oriented silicon steel were systematically studied at different hot charging and heating temperatures. When the hot charging temperature is below 950℃, the content and size of A1N remain unchanged, but the quantity and size of MnS and A1N-MnS increase when the hot charging temperature decreases, reach maximum and remain unchanged when the hot charging temperature is below 600℃. The total content of A1N and MnS solid solution in the slab heated at 1100℃ is less than that heated at 1200℃. Compared with the slab hot-charged at 850℃ and heated at 1100℃, the total content of A1N and MnS solid solution is less and the size of A1N and MnS is larger in the slab hot-charged at 600℃ and heated at 1100℃. The appropriate hot charging temperature and heating temperature are 600℃ and 1100℃, respectively.
Abstract: The effects of direct quenching-tempering (DQ-T) and reheat quenching-tempering (RQ-T) on the microstructure and mechanical properties of NM500 wear resistant steel were studied by scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy, and mechanical testing. The strengthening mecha-nisms of these heat treatment processes were also discussed in the paper. It is found that samples treated by DQ-T and RQ-T both have good ductility and high strength. The tensile strength and hardness of the DQ-T sample are superior to those of the RQ-T sample due to higher densities of dislocations and smaller sizes of martensite blocks, but the impact toughness and ductility of the DQ-T sample do not drop significantly. For the RQ-T sample, reheat quenching temperature has a remarkable effect on the strength, and fine blocks can be obtained when the quenching temperature is not high. This grain refinement strengthening can be an effective method to increase the strength of the RQ-T sample.
Abstract: The short-term corrosion behavior of Q235 and XT0 steel samples buried for one year in the test trench in a typical mountain sierozem area in Calgary, Canada was investigated by corrosion rate t, corrosion characteristic observation and analysis through scanning electrochemistry microscopy and X-ray diffraction, and soil physical and chemical properties analysis. It is found that Q235 steel has a close average corrosion rate and maximum pitting corrosion depth to X70 pipeline steel, but the former has an obviously higher pitting density than the latter. The corrosion products of these two metals are similar and mainly composed of FeOOH, Fe2O3 and Fe3O4, and the corrosion product layer is loose with cracks and not able to prevent these metals from corrosion. There are multiplex bacteria, such as sulphate reduction bacteria (SRB), sulphate oxidation bacteria (SOB) and heterotrophic bacteria in the soil attaching to the two steel samples, which are in cooperation to accelerate the occurrence of localized corrosion under the corrosion product layer due to the effects of their metabolic actions on corrosion processes.
Abstract: The microstructure, martensitic transformation behavior, mechanical properties and shape memory characteristics of Ni56Mn25-xFexGa19 (x=0-10) shape memory alloys were investigated by optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, differential scanning calorimetry, and compression testing. A single phase of martensite with tetragonal structure is observed in the alloys with x ≤ 4, but dual phases with martensite and face-centered cubic γ phase are present when x ≥ 6. Compared with martensite phase, γ phase is rich in Ni and Fe, and its volume fraction increases with increasing Fe content. The martensitic transformation peak temperature decreases from 356℃ for x=0 to 170℃ for x=10, which is attributed to the comprehensive effect of the tetragonality and electron concentration of martensite. The introduction of γ phase by substituting Fe for Mn can greatly improve the strength and plasticity of the alloys. However, the shape memory strain drops from 5.0% for x=0 to 2.0% for x=6.
Abstract: Reverse U type specimens of Alloy 690 were put in an autoclave to conduct the stress corrosion test for 4400 h. The stress corrosion behavior of the alloy in a high-temperature and high-pressure water solution containing Pb was studied by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results show that transgranular stress corrosion cracking occurs in the alloy. Corrosion products with Pb can be found to accumulate in the crack. EDS face scanning of the crack zone indicates that the corrosion film formed in the test solution is a double-layer structure, the outer layer is rich in Ni and the inner layer is rich in Cr. The difference of expansion coefficients between corrosion products in the crack and the matrix causes a faster crack propagation. Due to different surface treatments, the inner surface and outer surface of the specimens have different corrosion morphologies, the inner surface is lattice-like, but the outer surface shows a certain direction groove.
Abstract: AlMgSiCu alloys with different Zn contents were fabricated by conventional ingot metallurgy method. The effects of Zn content on the microstructures and mechanical properties of the alloys were investigated by optical microscopy, field emission scanning electron microscopy, tensile testing, and nanoindentation. It is found that Zn cun slightly refine the as-cast grain structure of the alloys. The grain boundaries become broader and more precipitates can form along the grain boundaries with the increase of Zn content; but the addition of Zn does not affect the phase components and morphology of the alloys. When the Zn content increases, the strength and elongation of the alloys increase firstly and then decrease. The alloy with the Zn mass fraction of 0.5% has the highest tensile strength, but the elongation of the alloy with the Zn mass fraction of 0.75% is the largest. Nanoindentation measurement shows that the elastic modulus decreases gradually with increasing Zn content.
Abstract: In order to avoid the generation of Al4C3 and AlN during heat treatment of carbon composite re-fractories with the addition of aluminum powder, this paper probes the effects of MnO2 on the phase composition and microstructure of C-Al materials. C-Al and C-Al-MnO2 specimens were prepared by using graphite flake, aluminium powder, and MnO2 fines as main starting materials, thermosetting phenolic resin as a binder, and being fired in a sag-ger filled with graphite powder at various temperatures. The phase composition and microstructure of the specimens were investigated by means of X-ray diffraction and scanning electron microscopy. Manganese dioxide was studied by thermogravimetric-differential thermal analysis. It is found that for C-Al materials without MnO2, Al powder first generates granular aluminium carbide, and then transforms to fibrous AlN and Al2O3. For C-Al materials with MnO2 addition, since MnO2 gradually decomposes with the evolution of oxygen, aluminum powder is directly oxidized to form Al2O3 followed by generating MnAl2O4 spinel. Thus, Al4C3 and AlN fail to form. The formed Al2O3 is present as granular at 800 to 1200℃, fibrous at 1400℃, and fully-developed prismatic at 1600℃.
Abstract: ZnO, La3+/ZnO, Ce3+/ZnO and La3+-Ce3+/ZnO photocatalysts were prepared by a sol-gel process and characterized by X-ray diffraction, transmission electron microscopy, ultraviolet and visible spectrophotometry, and BET specific surface area analysis. The photocatalytic activity of these photocatalysts was investigated by photodegradation of methylene blue (MB). The prepared La3+-Ce3+/ZnO photocatalyst is rectangular column shapes, with the average size of 57.3 nm. La-Ce codoping can increase the crystallinity of ZnO, promote the grain growth of ZnO, and improve the photocatalytic activity of ZnO greatly. In the photocatalytic degradation of 500 mL of 10 mg·L-1 MB, the photocatalytic degradation rate of MB with La3+-Ce3+/ZnO as a photocatalyst is 93.7%, which is 21.4%, 19.2%, 9.3% higher than those with pure ZnO, La3+-ZnO, Ce3+-ZnO as photocatalysts, respectively.
Abstract: Concrete specimens were coated with epoxy phenolic coatings and coal tar epoxy coatings, respectively. Hot water accelerated aging tests of the coated concrete specimens were carried out in circulating water and deionized water. In the aging process, the water absorbing capacity of these coatings was measured and the surface morphologies were observed. The dependence of water absorbing capacity on suction time and aging time was analyzed to find out a method for evaluating the service life of anticorrosion coatings on cooling towers with circulating water. It is indicated that the service life of the coatings at the test temperature can be predicted according to the inflection point on the curve of water absorbing capacity to aging time, and then the service life at the service temperature can also be calculated based on the Vant Hoff regulation.
Abstract: Aiming at the randomness and imperceptibility of chatter marks in a 2180 mm tandem cold rolling mill, two methods to identify the vibration of the rolling mill were systematically studied based on wavelet analysis and the fractal theory. Vibration signals from the rolling mill under typical conditions were analyzed by the two methods. The results show that both can effectively identify the vibration of the rolling mill. This paper provides an effective way to identify the chatter vibration in the complex vibration environment. The two methods have practical significance for real-timely monitoring the operation condition of rolling mills, avoiding the occurrence of hazardous production accidents, and then predicting the vibration of rolling mills.
Abstract: Aimed at the production flow of a steelmaking plant, a simulation model of steel ladle turnover process was constructed to analyze the affecting factors on the turnover rate of steel ladles~such as hot repair time, steel grade and repair age of steel ladles. Simulation results show that the turnover rate decreases with increasing hot repair time. When the daily productivity of typical steel is 45 heats, the turnover rate is 6.43 with the hot repair time of 0 to 20 min, but it is 5.0 with the hot repair time of 50 to 60 min. The turnover rates for different kinds of steel grades are different. When the daily productivity is from 41 to 50 heats, the maximum and the minimum turnover rate for producing SPHC steel are 6.28 and 5.63, respectively; however, the maximum and the minimum turnover rate for producing X70 steel are 5.00 and 4.55, respectively. The turnover rate increases with increasing repair age. When the daily productivity of typical steel is 48 heats, the turnover rate is 4.0 with the repair age of 40, and it reaches the maximum of 6.86 at the repair age of 45.
Abstract: Aiming at the steelmaking-continuous casting scheduling problem of a special steel plant, firstly, a multi-objective optimization scheduling model was developed, whose main evaluation indexes are furnace-caster matching degree, continuous casting heats, process waiting time, etc. Then the feasible range of product mix and production modes under different product mix conditions were analyzed by resolving the process flow structure and the operation cycle of steelmaking, refining, and continuous casting process. The scheduling problems under different production modes were solved by adjusting the operation cycle values of flexible processes on the basis of "furnace-caster matching" principle. Finally, the scheduling plans were calculated and compared with actual production data; the simulation results indicate the validity and superiority of the scheduling model and the solution strategy.
Abstract: Aimed at solving the problem that part of clustering algorithms are sensitive to the data input order, a non-interference sequence index was defined, and an approach applying the non-interference sequence was proposed to sort categorical data by weight. Based on this approach, a new clustering algorithm considering sorting by weight (CABOSFV_CSW) was presented to improve CABOSFV_C, which is an efficient clustering algorithm for categorical data but sensitive to the data input order. This approach eliminates sensitivity to the data input order. UCI benchmark data sets were used to compare the proposed CABOSFV_CSW algorithm with traditional CABOSFV_C algorithm and other algorithms sensitive to the data input order. Empirical tests show that the new CABOSFV_CSW clustering algorithm for categorical data improves the accuracy and increases the stability effectively.
Abstract: The intelligent control of a rotor flux oriented vector control system was studied. According to the characteristics of vector control systems, the control system was designed by making full use of the computer features of logical judgment and numerical calculation. It not only realizes the digitizing of the analog regulator but also overcomes the shortcoming of the control parameters being constant. The article emphatically introduced the adjustment of the digital controller in rules on the basis of the variables' variation tendency of the control system. Since different control strategies were adopt for different regulating laws, the control system has better static and dynamic performance and robustness. Simulation and experimental results show the correctness of the proposed method.
Abstract: Based on the pseudo-static method, an analytical solution of rock pressure for shallow-buried unsymme-trical loading tunnels under earthquake loading was derived by rotating the deflection angles of earthquake force and combining the limit equilibrium condition, with discussion on the influencing factors of rock pressure. It is found that the mechanical indexes of rock soil mass have an obvious influence on the lateral pressure coefficient. Under earthquake loading, the vertical earthquake acceleration coefficient always decreases the total vertical pressure on the vault and lowers the lateral pressure coefficient in most cases. The impact of horizontal earthquake acceleration coefficient on the total vertical pressure on the vault and the lateral pressure coefficient depends on the direction of horizontal earthquake force. The lateral pressure coefficient of the shallow-buried side always decreases with increasing ground inclination, but the lateral pressure coefficient of the deep-buried side increases.
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
