Abstract: An empirical formula to describe the relation of particle vibration velocity to explosive's quantity and distance from the explosion center is used in the blasting engineering field. Based on this formula, a new empirical equation to characterize the relation of particle vibration velocity to hypocenter energy and distance to the hypocenter is presented in this article, which is considered as the attenuation formula of seismic wave energy. In the new equation, the coefficient of seismic wave energy, K1, is introduced to describe the relationship between hypocenter energy and particle vibration velocity. It is thought that K1 has strong relationship with the locale medium characteristic of the hypocenter, nothing to do with the blasting parameters. According to the energy data of check points, K1 is calculated by regression analysis. By using the energy attenuation model, taking particle vibration velocity, distance to the hypocenter and K1 of each mieroseismic incident as the known parameters, hypocenter energy and attenuation coefficient as the regression parameters, the hypocenter energy can be obtained by inverse calculation. This method provides a new idea to calculate the hypocenter energy.
Shak-flask test was conducted by adding surfactants to solve problems about the low leaching speed and leaching rate of copper ores. The influences of three different kinds of surfactants on the leaching of copper ores were investigated by measuring the surface tension of solution before and after leaching and the Cu leaching rate. It is found that the surface tension of solution has great influence on the Cu leaching rate; moreover, the anionic surfactant has the greatest effect on accelerating leaching with the Cu leaching rate of 62.5%. In column leaching test, the Cu leaching rate increases by nearly 10% by using the anionic surfactant. The mechanism of accelerating leaching is analyzed based on physical chemistry and permeation fluid mechanics. It can be concluded that the surface tension of solution and the adsorption of surfactants on the ore surface have great effect on the wettability of copper ores. In addition, the persistence of surfactants should be taken into consideration in leaching.
Abstract: To counter the condition that quality deterioration of raw materials causes the pressure drop in a blast furnace increasing, new burden charging methods are sought to improve the permeability. Study results show that mixing different size particles can decrease the voidage and thus worsen the permeability, but decreasing the particle mixing can increase the permeability. In order to improve the permeability, the grading patterns, the sequence and period for charging different sizes of raw materials were studied in turn. And also the burden charging characteristics of cascade hoppers, two parallel hoppers, and three parallel hoppers were researched. The study result is very important in decreasing the pressure drop and keeping the BF stability and smooth.
Abstract: An expression was regressed to describe the relation of phosphate capacity in slag to slag's optical basicity and temperature. An iso-phosphate capacity graph of the CaO-SiO2-FeO (10% MgO) slag system was depicted by the regression expression. The effect of converter end-point slag, end-point composition and temperature on the phosphorus content in steel was analyzed. When the phosphate capacity in slag is constant, the distribution ratio of phosphorus between slag and steel increases with the converter final carbon content decreasing; but at a constant final carbon content, with the increase of phosphate capacity in slag, the distribution ratio of phosphorus between slag and steel increases. It is suggested that the final carbon content is controlled between 0.03% and 0.04%, the slag basicity is more than 3.5, the FeO content in slag is less than 18%, and the P2O5 content in slag is less than 2%, which are favorable for producing liquid steel with the final phosphorus content less than 0.008%.
Abstract: The main factors were studied which influence the titanium yield during a ferro-titanium alloying process. The inclusion phases and removal effect were comparatively analyzed before and after ferro-titanium alloying. When controlling the activity of oxygen (a[o]) before deoxidation below 350×10-6, the interval time between Al and Ti addition above 3 min can guarantee the titanium yield above 85%. With a[o] above 350×10-6, the interval time between Al and Ti addition should be extended more than 5 min. Extending the interval time between Al and Ti addition can improve the titanium yield at the same a[o] and [Al]s. During RH refining, Al2O3 inclusions with the equivalent diameter above 200 μm can float and be removed within 5 min, but the removal time of AI-Ti-O inclusions with the same size is 1 to 2 min more than pure Al2O3. Al-Ti-O complex inclusions form around Al2O3 after the titanium alloy being added into the melt, and the titanium yield decreases due to the formation of these inclusions.
Abstract: The solidification of metallic droplets based on homogeneous nucleation is studied by a mathematical model of nucleus growth in metallic droplets. An asymptotic solution to the model is obtained by the asymptotic analysis method. The effects of surface tension, interface kinetic parameter, initial nucleus size, and undercooling on the growth rate, radius, and solidification time of the nucleus are analyzed on the basis of the asymptotic solution. It is found that surface tension and interface kinetics parameter significantly decrease the growth rate of the nucleus under a certain undercooling condition. The growth rate of the nucleus rapidly rises in the initial short period of solidification. After the growth rate of the nucleus reaches its maximum~ it gradually descends with the increase of nucleus radius. In the meantime, the effects of surface tension and interface kinetic parameter on the growth rate of the nucleus decline gradually. With the increase of undercooling, the solidification time of the droplet decreases. After transient solidification within the initial short period, the temperature distribution in the droplet is rapidly modified from some initial distribution to a certain temperature distribution determined by undercooling, surface tension, interface kinetic parameter, etc.
Abstract: Cold-rolled low-carbon medium-manganese steel (0.2C-5Mn) was cooled by different methods after annealing. Its microstructure and tensile properties were investigated by means of tensile testing, scanning electron microscopy (SEM), electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction. Intercritical annealing after cold rolling results in a duplex structure of ultrafine ferrite and reverted austenite. Reverted austenite in the steel experienced annealing and air cooling is more stable and its volume fraction is significantly higher than that in the steel treated by annealing and furnace cooling. In addition, reverted austenite in the steel experienced annealing and air cooling can produce sustained TRIP effect during deformation, leading to improvements in strength and plasticity. The product of tensile strength and total elongation exceeds 26.5 GPa.%.
Abstract: The corrosion electrochemical impedance spectroscopy characteristics of AF1410 steel electron beam welding joints at different positions and for different exposure time were investigated in a simulated marine environment by neutral salt spray testing. The corrosion resistance and the electrochemical behaviors of the weld fusion zone and the base metal were evaluated according to the microstructure analysis of the welded joints. The investigation of open circuit potential and impedance spectroscopy indicates that thick tempered martensite and carbide precipitates at the weld fusion zone are easy to form a corrosion cell, and the corrosion reaction resistance is less than that of the base metal, which easily leads to electrochemical corrosion. Equivalent circuits of impedance spectroscopy were established and fitted for the different corrosion stages.
Abstract: The corrosion behavior of 300M steel, Aermetl00 steel, and ultra high strength stainless steel was investigated in the mold environment, including Aspergillus flavus, Aspergillus niger, Chaetomium globosum, Penicillium funiculosum, and Aspergillus versicolor, by scanning Kelvin probe (SKP) measurements. The growth of the mold was observed by scanning electron microscopy (SEM) and was analyzed by energy dispersive X-ray spectroscopy (EDS). The mold presents individual and cumulate growth on the specimen surface of 300M steel and the amount increases gradually, it grow individually and dispersively on the specimen surface of Aermetl00 steel and the amount increases gradually, but it shows radial and netty growth on the specimen surface of ultra high strength stainless steel and the amount increases greatly, which results in a microbial film. Some corrosion appears on the surface of all the three steel specimens after mold test. 300M steel presents the severest corrosion with wide and shallow pits, Aermetl00 steel is the next with narrow and deep pits, and corrosion resistance for ultra high strength stainless steel is the best. SKP measurements show that the mold can facilitate the corrosion process for 300M steel and Aermetl00 steel but inhibit it for ultra high strength stainless steel in some degree.
Abstract: The microstructurM evolution of γ′ phase was investigated in difficult-to-deform nickel-base superalloy GH720Li subjected to subsolvus solution heat treatment, 650℃ for 24 h → air cooling or 650 ℃ for 24 h→ air cooling + 760 ℃ for 16 h → air cooling after subsolvus solution treatment, and long time aging at 870 ℃ for 3000 h. It is found that the primary γ′ phase is affected most significantly by subsolvus solution treatment, the degree of partial dissolution increases with increasing solution temperature, and aging treatment makes the primary γ′ phase turn to sphere or near sphere. However, the secondary and the tertiary γ′ phase fully dissolve into the matrix during subsolvus solution treatment, re-precipitation during the aging is obvious, and the amount and zone increase with increasing solution temperature. When long time aging at 870 ℃ the microstructure uniformity gradually improves, and the secondary and tertiary γ′ phase dissolve. The primary γ′ phase at grain boundaries coarsens a little after 500 h. Besides, the hardness decreases with the aging time prolonging at 870℃ before keeping unchanged.
Abstract: This article studies carbides and their reactions in nickel-base superalloy powders prepared by rapid solidification and the hot isostatic pressed (HIPed) alloy. With the pre-treated temperature rising, the segregation of alloy elements in the powders reduces, but MC carbides in the interdendritic region still exist at elevated temperatures. As a result, there are more Ti and Zr at this area. Blocky and petal-like MC carbides distribute in the interdendritic region of the initial powders. During the pre-heat treatment the blocky carbides decompose, and M23C6 and M6C precipitate in the interdendritic region; however, the petal-like carbides can remain stable at higher temperatures. Carbides in the interdendritic region of the HIPed alloy are composed of blocky M6C and MC and petal-like MC carbides, but deformation and recrystallization can induce the MC carbides to decompose.
Abstract: To develop low-cost sintered Nd-Fe-B magnets, 30% Ce was used to substitute for Nd and Pr in magnets with the nominal compositional (Nd0.75Pr0.25)32.69Fe66.25B1.06. The microstructure and magnetic properties of the magnets were studied during the processes of sintering and tempering. It is found that the magnetic properties of the orientated compacts decrease with the sintering temperature increasing from 1030 to 1080 ℃, and the magnets sintered at 1030 ℃ for 2 h exhibit the best magnetic properties. Compared with the non-substituted magnets, the Ce-substituted magnets show higher magnetic properties. The phase composition and grain size do not show obvious change along boundary structure by one-order tempering, and the magnetic properties of the magnets keep the same, or decrease slightly. By two-order tempering, the eoercivity of the magnets is greatly improved by optimization of boundary microstructure, with more clear and straight boundaries. The remanence, coercivity, and maximum energy product of the Ce-substituted magnets are slightly lower than those of the non-substituted magnets.
Abstract: In order to study the nitridation kinetics of silicon powder under atmospheric pressure, a set of nitrida- tion experiments were performed at 1350 and 1400 ℃ for 10 to 30 rain. Silicon powder of 2.2 ~m in average diameter and 99.99% in purity was adopted as the experimental materials, and nitrogen of 99.993% in purity was used as the reaction gas. At different temperatures, the conversion rate of silicon is obtained as a function of reaction time. Based on the noncatalytic gas-solid reaction model, a dynamic model of silicon nitridation under atmospheric pressure is introduced, which includes two key model parameters: reaction rate constant of silicon nitridation and diffusion coefficient of nitro- gen in silicon nitride, These model parameters are obtained by fitting the experimental data under different conditions. Assuming that reaction rate constant and the diffusion coefficient can both be expressed as the Arrhenius style, the activation energy and pre-exponential factor of the reaction are calculated as 2.71× 104 J·mol-1 and 3.07× 10-5 m·s-1, and the activation energy and pre-exponential factor of diffusion are calculated as 1.06×105 J·mol-1 and 1.12×10-9 m2·s-1, respectively. Then a series of conversion curves are predicted at different temperatures and powder sizes. On the trend, the predicted curves are in good agreement with experimental data in literatures.
Abstract: Aluminum foams were prepared by accumulative roll-bonding (ARB). Their porosity and pore mor- phology were studied by weighing and optical microscopy, respectively. It is found that aluminum foams prepared by ARB with TiH2 powder as the blister have optimum performance within the foaming temperature of 660 to 680 ℃ and the foaming time of 6 to 10 min. The optimum values of foaming temperature and foaming time are relevant to blister content. With 1.5% TiH2 at 670 ℃ for 8 min, the porosity and pore size of aluminum foams can reach 42% and 0.43 mm, respectively. Taking the aluminum foam by accumulative roll-bonding as the core, TC4 titanium alloy/aluminum foam and 1Crl8Ni9Ti stainless steel/aluminum foam sandwiches were produced by roll cladding. The interface morphology of these sandwiches was investigated by optical microscopy and energy spectrum analysis. A conversion zone forms by combination reaction between the face plate and the core plate, leading to metallurgical bonding at the interface.
Abstract: Testing methods including X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform-infrared spectroscopy (FT-IR), and thermogravimetric/differential scanning calorimetry (TG-DSC) were used to study the reaction mechanism of aerated concrete prepared by iron ore tailings (IOTs) under the condition of autoclaved curing. Without autoclaved curing, major hydration products in the green body are ettringite (AFt), calcium silicate hydrate (CSH) gels with low degree of crystallinity, and Ca(OH)2. The XRD peaks of some minerals in the iron tailings reduce. After autoclaved curing, the XRD peak of ettringite disappears, but the XRD peak of tobermorite increases. It is revealed that, mineral components in the iron railings are decomposed, and reactions between the active components of SiO2, Al203, and Ca(OH)2 cause the formation of tobermorite under the conditions of high temperature, high pressure and hot alkaline activation.
Abstract: Based on macro plastic deformation, the differential method and integral method were presented in analyzing hot-strip-rolling. Theoretic formulas for calculating the rolling force and rolling torque were concisely educed according to those methods. The theoretic formulas have got rid of excessively experimental parameters adopted in the traditional formulas, rationally expounded the physical meanings of such variables as bite angle and neutral angle, and disclosed the relationship among the rolling variables such as rolling force, rolling torque, yield strength of metal and friction factor. Finally, a detail comparison between the calculated and measured data is made by experimental rolling, which has basically verified the correctness of the proposed formulas for hot-strip-rolling.
Abstract: To calculate the bending fatigue life of gears, the fatigue process was divided into crack initiation and crack propagation periods. The real working condition of gears was imitated with ADAMS software and a loading spectrum during the work process was gained. According to the loading spectrum the maximum stress in the dangerous cross-section of the gear root was analyzed by the finite element method based on ANSYS software. Fracture mechanics, the rain flow counting method, and the Miner fatigue cumulative damage model were used to predict the bending fatigue life of gears under the dynamic load, and two calculation models of bending fatigue life were proposed for crack initiation and crack propagation, respectively. To verify the calculation models, bending fatigue testing was performed on a high- frequency fatigue testing machine. The experimental data comply with the numerical simulation results, indicating the correctness of the theoretical analysis.
Abstract: The combustion process of raw coal with different additives was characterized by thermogravimetry and statistical analysis. It is found that the activation energy of raw coal can be reduced from 98.07 k J-tool-1 to 73.73, 78.50, and 76.45 kJ·mol-1 by adding MnO2, CaO, and CeO2 with the mass fraction of 2%, respectively. The exothermic peak temperatures of combustion are separately lowered from 534.2 to 482.7, 489.4, and 484.9 ℃, but the additives have little effect on the exothermic peak temperature of oxidation, leading to a 30 ℃ reduction of distance between the oxidation peak and the combustion peak. The effects of additives on the activation energy and the combustion peak accord well with the Boltzmann equation fitted through experimental data. The lower the exothermic peak temperature of combustion, the smaller the activation energy is. Thus the activation energy can be approximately evaluated from the exothermic peak temperature of combustion in the differential thermal analysis curve.
Abstract: A switching strategy based on (CPSO-SGA) was presented by combining their chaos particle swarm optimization own advantages. In the switching and specialized genetic algorithm strategy, CPSO is applied in the former step and SGA is executed in the later step. The best switching conditions under three switching indices of iteration steps, population standard deviation, and optimal individual fitness values were determined by large amounts of simulation experiments. In comparison with single SGA and single CPSO, the proposed switching strategy CPSO-SGA has a better performance when path length, smoothness, and running time are taken into consideration.
Abstract: Several reinforced concrete frame structures with different stories were designed according to the current Chinese seismic code, in which several schemes of reinforcement mergence were taken into account. The overstrength factor of each structure was calculated by static elastoplastic method. Analysis on the relation of the overstrength factor to the number of stories and the mergence factor show that the overstrength factor decreases with the number of stories increasing but increases with the mergence factor enlarging. The effect of mergence on overstrength is more obvious in low structures than that in high structures. The current Chinese seismic code needs to be revised to consider every factor influencing the overstrength of structures.
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
