Abstract: Based on load-unload experiment, the acoustic emission (AE) character of rock samples under load-unload disturbance was studied and tested under different stress levels. The results show that under a low stress level, there are several discrete AE signals when the rock sample is loaded, and almost no AE signals during unloading; under a high stress level, AE is active relatively under load disturbance, and there are obvious AE signals even during unloading. AE signals under different stress levels and stress states refleet different constitutive properties of rock materials. This characteristic must be considered in the stability testing and evaluation of underground engineering in-situ rock mass.
Abstract: Considering the high nonlinearity and uncertainty of influence factors in a slope system and making full use of the ad-vantages of the rough set theory and genetic programming (RS-GP model), a novel method based on the influencing factors of slope stability was brought up to calculate the safety factor of a slope. This method can reduce the structure scale of a genetic programming prediction model by analyzing the data characteristics of learning samples, calculating the significance of attributes and reducing rules. The results of an ANN model and the RS-GP model show that the proposed method has such merits as fast computing speed, high fault-tolerance capacity and high precision.
Abstract: The temperature of a steel ingot of 28.7 t was measured during solidification and the temperature field and solidification process of the steel ingot were simulated by a finite element method. It is shown that the simulated values of the temperature field agree well with the measured data, indicating that this simulation is accurate and reliable. At the initial stage of solidification, the bottom of the steel ingot and the connection zone between the ingot mold and the insulating riser solidify faster. At 52 min, an air gap forms between the steel ingot and the adiabatic plate. At the first 3 h, the steel ingot solidifies parallelly from the mold wall to the center. The later stage of solidification is faster than the early stage. The solidification time is 428 rain in the center of the insulating riser and the final solidification time is 365 min in the center of the ingot body. The former is 15% longer than the later, which is benefit to control shrinkage cavities in the insulating riser only. Based on the simulation, the pouring temperature reduces from 1543℃ to 1533℃, which does not affect steel feeding but also can reduce 6 mm of the depth of shrinkage. This method can improve the quality of steel ingots.
Abstract: In combination with the actual situation of the secondary cooling of a billet continuous caster, a heat-transfer mathematical model was established with finite element software ANSYS. Heat-transfer coefficients in different secondary cooling regions were modified on the basis of pin-shooting results to improve the accuracy of the mathematical model. The results show that the modified mathematical model can simulate the whole heat-transfer and solidification process of the continuous caster. The location of electromagnetic stirring was determined by referencing the results of numerical simulation and pin-shooting techniques. Central carbon segregation and porosities in billets were alleviated by adopting electromagnetic stirring.
Abstract: Low cycle fatigue characteristics of 10CrNiMo high-strength steel were investigated with smooth rotundity-section specimens through low cycle fatigue testing under axial loading controlled by different strain amplitudes, including cyclic stress-strain behavior, strain-life feature, cyclic stress response and mechanical hysteresis. The relevant fatigue parameters, cyclic softening/hardening property and strain hysteretic rule were given on the basis of experimental data. Observations of crack propagation orientation and frac-ture surfaces show that fatigue cracks initiate with multi-initiation sites from the specimen surface, distribute along the fracture border, and propagate along planes with different angles to axial force. Fatigue crack propagation is mainly in the blunting-resharpening mechanism.
Abstract: H13 steel was prepared by traditional processes and spray forming respectively, then it was subjected to forging processes. The miorostructure and hardness of H13 steel prepared by different processes were studied by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness tester. The results show that the spray formed and forged H13 steel possesses a finer grain size and a higher hardness than traditional H13 steel.
Abstract: Wet gas corrosion experiments of three low alloy steels containing different contents of elements Ni and Cu were conducted by homemade equipment simulating the oil tanker corrosion environment. The corrosion rate, corrosion morphologies and corrosion products of the three steels in a CO2-02-H2S-SO2 wet gas environment of crude oil tanks were compared and the corrosion mechanism was also analyzed and discussed. The results show that the corrosion morphologies of the three steels are all uniform corrosion; as the corrosion products forming and spalling, the corrosion rate of the steels fluctuates with the increase of testing time. Elements Ni and Cu can obviously improve the corrosion resistance of the steels to the wet gas environment. In the wet gas environment, hydrogen evolution corrosion and oxygen absorption corrosion caused by CO2-02-H2S-SO2 corrosion gases exist as well as wet sulfur corrosion from the oxidation of H2S by 02. The correlation between wet gas corrosion depth loss DLt and corrosion time t is properly accordant with the expo-nential relationship DLt=At8, and the values of coefficient A and exponent B of the three steels with different alloy elements were obtained.
Abstract: A uniform design experimental method was employed to discuss the interactive influence of Cl- concentration, pH values and temperature on the pitting susceptibility of X120 pipeline steel in HCO3- + Cl- solutions by a potentiodynamic scan technique. The experimental results indicate that Cl-- concentration, pH values and temperature have great effect on the corrosion and passive behavior of X120 pipeline steel in HCO3- + Cl- solutions, and the influence order is as follows:Cl- concentration has the greatest impact, then the combined action of Cl- concentration and temperature, the third one is pH values, and temperature has the smallest impact. X120 pipeline steel has the least pitting susceptibility in the HCO3- + Cl- solution whose C1 concentration is 0 mol·L-1, pH value is 8.5 and temperature is 0℃.
Abstract: The effect of speed ratio, rolling reduction ratio and annealing on the recrystallization grain size of AZ31 magnesium alloy sheets was studied under the condition of differential speed roiling process. It is shown that the grains can be significantly refined by increasing the speed ratio and reduction ratio. But when the speed ratio is too high, sliding occurs between the rolls and sheets, lower-ing grain refinement. A speed ratio of 1.3 provides the best grain refinement. The major reason that differential speed rolling leads to a better grain refinement is that shearing deformation in differential speed rolling can increase the number and uniformity of twins and cut up dislocation cells or walls, the distortion energy more evenly distributes in the magnesium alloy. In addition, a reasonable differential speed rolling process also reduces the middle and final annealing time.
Abstract: The pure nickel liner of shaped charge was prepared by using a direct current electroforming technique. The high speed deformation mechanism of the jet formed by explosive detonation in the electroformed nickel liner of shaped charge was discussed by comparing the microstructure and microtexture of the nickel liner of shaped charge before and after explosive detonation. Experimental results show that the original grains with a columnar shape change to equiaxed grains and fibber textures existed in the nickel liner of shaped charge disappear due to high speed explosive detonation. The jet and slug formed by explosive detonation undergo an adiabatic process. A melting phenomenon was observed due to the interaction between the jet and target, and a Fe-Ni alloy is formed. The melting Fe-Ni alloy forms a complex structure by solidification around the surface of the slug when it meets the following slug. It is indicated that dynamic recovery and recrystallization play an important role for high speed deformation in the electroformed nickel liner of shaped charge during the explosive detonation process.
Abstract: Ni-based alloy coatings were prepared by hot dipping on plain steel substrates successfully. The coated plain steel was heat treated to improve the bonding strength of interfaces between the coatings and the substrates. The microstructure and the mechanical properties of the interface were investigated before and after heat treatment. It is shown that after heat treatment, precipitates on the side of the coating are larger than those before heat treatment. Noncontinuous lump iron borides are found in the interface. The interdiffusion distance of Ni and Fe locating on both sides of the interface increases, and the transition zone evolves from 5-8 μm to 20 μm after heat treatment. There are γ-(Fe, Ni), CrB, Cr2B, Cr3C2, etc. in the coatings before and after heat treatment. The transition zone is composed of three phases which are major γ-(Fe, Ni) and minor CrB and Fe23(C, B)6. From the interface to the coating, the microhardness increases gradually after heat treatment. The bonding strengths before and after heat treatment are 140 MPa and 200 MPa, respectively.
Abstract: High frequency power NiZn ferrites with the composition of Ni0.5-xZn0.5CoxFe2O4 (x=0, 0. 01, 0. 02, 0.03) were prepared by the conventional oxidation process. The temperature dependence of magnetic properties of the samples was synthetically studied in a wide temperature range of -40 to 200℃. The effect of Co3+-doping on the power loss at high temperature was also analyzed. It is found that the grains are more homogeneous and refiner with the addition of Co3+. In addition, the temperature dependences of the initial permeability and power loss are also greatly improved, and the lowest power loss temperature shifts to a lower temperature with increasing Co3+-substitution. The ferrites with the composition of Ni0.49Zn0.5Co0.01Fe2O4 have not only rather low high-frequency power loss, but also a nicer temperature stability in the wide temperature range of -40 to 200℃. The relative temperature coefficient of permeability is 3×10-6℃-1, the variation range of power loss is from 130 to 140 kW·m-3 in the temperature range of 100 to 200℃, and the lowest power loss is 130 kW·m-3 (1 MHz, 10 mT).
Abstract: UV accelerated aging was performed on polyurea anti-corrosion coatings. The aging behavior of the coatings was analyzed by gloss meter, scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR) in combination with electrochemical impedance spectroscopy (EIS). Experiment results indicate that the coating accelerated aging is divided into early, middle and late stages. The color of the coating surface changes severely in the middle stage. SEM images of the coating surface and cross section show that the development of aging cracks to the substrate is terminated by tiny bubbles, and the anticorrosion performance of the coatings declines very slightly.
Abstract: Polystyrene/polypyrrole (PS/PPY) composite microspheres were prepared by seeded emulsion polymerization. When they were utilized as support and reacted with the Mo active center, PS/PPY composite microsphere supported Mo catalysts were obtained. The effect of the characterization of support on the catalytic activity of the polymer supported Mo catalysts was systematically studied. The results indicate that the supported catalyst with hydrophilie nature shows a higher catalytic activity when hydrogen peroxide was used as an oxygen source; the doped ions in the polymer also show effect on the catalytic activity of the supported catalyst, the supported catalyst prepared using ferric nitrate as an oxidant shows the highest catalytic activity, and the conversion in epoxidation of ciscyelooctene can be 90%.
Abstract: The characteristics of cheaper Qingxu coal were investigated in Taigang of China. It was discussed that Gaoping anthracite and Lu'an lean coal are replaced by cheaper Qingxu coal. Twelve performance tests of Qingxu coal were carried out. The results show that Qingxu coal has such virtues as a better combustion property and reactivity, a higher heat value and ash fusibility, good fluid-ly and non-explosiveness at the same time. Conversely the S content is higher in Qingxu coal, and the Zn content is lower in the washed Qingxu coal but higher in the unwashed Qingxu coal. The blast furnace injection standard can be achieved by mixing the coal. The analysis of FactSage software illustrates the reason that the tuyeres are jammed by slagging when Qingxu coal is used excessively. Laboratory studies and field results show that Qingxu coal can be injected into the blast furnace by coal blending, but the substitution rate of Qingxu coaI should be to less than 20%.
Abstract: Microwave electromagnetic characteristics in radar measurements of burden surfaces and media thickness of an ore and coke (O/C) layer were researched in the closed environment of a blast furnace (BF). With electromagnetic calculations and CST simulation software, a dielectric constant model of the media layer was developed to study the transmission, reflection and absorption characteristics of the burden surface and the O/C layer in BF. Also a reconstruction relational model of the number of distributing O/C layers in BF, microwave angle and frequency band concerned with the dielectric constant of the media layer was established. Using trans-mission and reflection electromagnetic characteristics of radar waves, combining with BF radar distributed radar sensor array installation and the different dielectric constants of the O/C layer in BF, the three-dimensional reconstruction imaging of burden surfaces and O/C layer thickness in BF was realized on-line.
Abstract: The expression of quantitative relationships between characteristic parameters of work roll wear and roll shifting strategy parameters was derived, the effect of various roll shifting strategy parameters on characteristic parameters of work roll wear was studied theoretically, and the effect of roll shifting on loading gap under different work roll wears was analyzed. On this basis, the principle of selecting roll shifting parameters was established, and a varying shifting stroke strategy of conventional work rolls in hot rolling was proposed. The strategy was applied in many production lines of hot strip mills in China.
Abstract: A phase-domain filtering pick-up method for roll eccentricity compensation control is proposed by analyzing the mechanism of action of roll eccentricity. This method utilizes the character that the effect intensity of roll eccentricity is closely related to the rotating phase of rollers. In the method the time-domain eccentricity data are transformed to the phase domain of the roller's rotating movement first, and then processed. In the linear phase domain, the eccentricity-related signal shows distinct periodicity, and the periodicity of the other periodic signals in time-domain is weakened during this transformation. The roller's rotating period is used as the target period for cyclic statistics in the linear phase domain. Theoretic analysis indicates that the effect of noise is eliminated and some unwanted periodic signals are choked by the statistics, so the roll eccentricity characteristic information can be picked up adequately. The essential of this proposed method is a kind of comb filter in linear phase-domain. The eccentricity characteristic information can give data support for eccentricity compensation.
Abstract: The adsorption behaviors of nitrogen and hydrogen towards nickel screens under various electric fields were studied. A self-made instrument with high voltage supply was used for gas adsorption tests. Signals detected from gas adsorption tests indicate the adsorb behavior during adsorption and desorption processes. Distinctive hydrogen sorption enhancement is obtained by applying an elec-tric field on the samples. The higher the applied electric field strength is, the higher the hydrogen adsorption capacity is achieved in the tests. The amounts of adsorption capacity increased with increasing gas pressure are not obviously when the applied electric field is consistent. This enhancement is ascribed to stronger interactions between hydrogen and the sorbent under electric fields. A stronger adsorption force is generated by the polarization of hydrogen molecules; furthermore the charged species have capabilities to cluster hydrogen molecules.
Abstract: A ladle thermal tracking model was established for the whole steel working process, from steelmaking to continue casting. The ladle thermal tracking model was modified by using the inverse heat transfer problem, which combined ladle thermal status testing and ladle heat transfer numerical simulation. With the ladle thermal tracking model some factors influencing molten steel temperature were analyzed such as new ladle preheating time, cooling time, off-line preheating time and the wear of the work wall and bottom linings of the ladle. It is shown that the molten steel temperature drop in the new ladle first thermal circulation reduces by 15.6℃ when the new ladle preheating time increases from 480 min to 780 min. When the ladle cooling time is 540 min, the molten steel temperature drops 14.6℃ more than that of a normal turnover ladle. The longer the ladle cooling time is, the stronger the effect of off-line preheating time on the molten steel temperature drop is. When the ladle cooling time is 540 min, 240 min off-line preheating could reduce the molten steel temperature drop by 11.0℃. The wearing of the ladle linings would increase the molten steel temperature drop no more than 9.3℃.
Abstract: The metallurgical nature of production flow was compared between aluminum and iron & steel under structural characteristics of current production flow and energy utilization states in the aluminum industry. The production flow was divided into process sections. The energy structure and energy dissipation disciplines of the aluminum industry were synthetically analyzed. Referred to the practice of energy-saving technology in the iron and steel industry, the systematic energy saving potential was pointed out in the aspects of process improvement, energy structure optimization, industrial waste utilization and excess energy recycling, etc. An ordered and high efficiency mode after electrolysis was proposed in the production flow structure.
Abstract: Based on a project of denitrification, a complex structure contained a flue, a reactor and a bracket was analyzed. The flue exit and the reactor were chose as research subjects, and the effect of bracket deformation on the mechanical properties of the flue exit and the reactor was studied. It is indicated that the deformation distributions of the flue exit and the reactor change from symmetric into asymmetric when the influence of bracket deformation is considered, and the average deformation of them increases too, but the stress values and distributions of the flue exit and the reactor change slightly. Consequently, designing the flue exit and the reactor separately is acceptable when strength is the control factor.
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
