Abstract: Mining design generally needs to establish a block model or a three-dimensional solid model for calculating the irregular geometrical volume. It is found that in practical applications the two models have their own disadvantages. The block model has the problem of computation error, i. e. discretization accuracy, and the three-dimensional model has the disadvantages of long time consuming and instability. In order to solve these problems existing in the two models, this paper proposed a new semi-continuous and semidiscrete model and subsequently provided the model algorithm and practical cases. Research results illustrate that the proposed semicontinuous and semi-discrete model has the advantages of high computing speed, low error, and calculation stability, so it is a high efficiency method for mining design.
Abstract: A tunnel kiln was used to process stainless steel dust from the Stainless Steel Branch of Baosteel. The technical process is that coke, 35% of the dust mass in dosage, was placed outside around the dust, and different proportions of iron scales were reduced in the silicon carbide tank for 42 h at 1 200℃. It is shown that the sintering of the dust can be realized in the tunnel kiln process and the strength of the sinter is improved economically and effectively by adding the iron scale (20% of the dust mass in dosage). The iron grade increases by adding the iron scale, but the nickel and chromium grades decrease. A method of estimating the reduction rate was proposed since the metallization rates of nickel and chromium were difficult to be measured. This method was applied to this test, and it is found that under the condition of the tunnel kiln process, the metallization rates of iron and nickel are 92.55% and 97.83%, respectively, and the metallization rate of chromium can reach at least 35.5%.
Abstract: The effects of Yunnan coal as a reducing agent and the desulfurizer SH on the improvement in iron grade and the desulfurization of a sulfuric acid residue were investigated in direct reduction and roasting processes. The mechanisms of action of Yunnan coal and the desulfurizer SH were analyzed by X-ray diffraction and scanning electron microscopy. It is shown that in the high-temperature reducing atmosphere, volatile elemental sulfur and carbonyl sulfur, metallic iron and nonmagnetic troilite are produced from pyrite in the residue. Magnetite and hematite in the residue are reduced into iron. In the roasting process of the residue, Yunnan coal has obvious desulfurization effect; however it cannot meet the requirement. The addition of the desulfurizer SH can reduce sulfur further more. Its mechanism of action is that in the direct reduction and roasting processes, the desulfurizer and pyrite generate iron and calcium sulfide without magnetic, which can be separated by a grinding and magnetic method, so the aim of desulfurization is reached.
Abstract: In consideration of the equilibrium of C and O elements, a mathematical model was established for decarburization in RH refining. The principle and process of establishing the model were illustrated according to 210 t RH refining for ultra-low carbon steel. A comparison between the modeling results and measuring data shows that the prediction of the mathematical model agrees well with industrial practice. There exists the nonuniform characteristic of carbon in liquid steel. The position with the minimum mass fraction of carbon is at the free surface in the vacuum chamber above the descending snorkel, while the position with the maximum mass fraction of carbon is at the interface between slag and liquid steel on the right side of the ascending snorkel. The difference between the maximum and minimum values is 0.002 5% after 20 min circulating.
Abstract: The effect of refining slag on inclusions was studied from two aspects, the activity of Al2O3 and the composition of inclusions. The activity of Al2O3 in a CaO-Al2O3-SiO2-MgO(8%)-CaF2 (8%) slag was calculated by the thermodynamic software Factsage, and the influence of slag basicity and (MgO) content on the activity of Al2O3 were analyzed. When the slag basicity increases from 1.0 to 2.0, the activity of Al2O3 in the slag decreases rapidly, and when the slag basicity increases from 2.0 to 3.8, the activity of Al2O3 has little change. There is little difference in the activity of Al2O3 between the slags with (MgO) mass fractions of 5% and 8%, and[Al]s can be easily reduced into molten steel from the slag with high basicity. Many brittle inclusions containing MgO were found in wire rods with the high basicity refining slag, and by analysis the most appropriate basicity is 2.5 to 3.0.
Abstract: Based on the similarity principle, a water model was established for the problem that a large number of bubbles overflow from the submerged tube in the CAS process. The effects of the flow rate of bottom gas, the submerging depth of the submerged tube and the nozzle position on the mixing behavior of liquid steel were studied. It is found that the problem of bubble escaping can be resolved when the hood center and the bottom nozzle center are coaxial. For a 300 t ladle, the optimal bottom blowing process was obtained. The optimal position of bubbling is 0.3r to 0.4r (r is the ladle bottom radius) away from the ladle bottom center, the flow rate of bottom blowing is approximately 600 L·min-1 in the refining process and 500 L·min-1 in the deslagging process, and the immersion depth of the submerged tube is 180 to 225 mm. Industrial tests show that the improved bottom blowing process can effectively prevent bubbles from overflowing, and improve the cleanness and castability of the LCAK steel.
Abstract: Macro- and micro-characteristics at the center of a continuous casting bloom of non-quenched and tempered steel 49MnVS3 were investigated by optical microscopy, scanning electron microscopy and energy dispersive spectrometry. It is found that serious segregation induces a central crack. The crack occurs at the end of columnar grains and the zone of coarse equiaxed grains, and propagates along the boundaries of primary dendrites. The clacking mode is intergranular cracking, which happens in the liquid phase. There are two kinds of grain boundary segregations, one is the precipitation of MnS inclusions, and the other is the concentration of liquid steel. The precipitated inclusions at the central position do not meet the requirements of the non-quenched and tempered steel.
Abstract: Molecular dynamics simulation was performed to study the nanoindentation process of a hard diamond tip into an Fe substrate. The atomic configuration of the substrate, the load-displacement curve, and the emission and variation of dislocations during loading and unloading processes were investigated. The plastic deformation mechanism of the substrate was discussed. It is found that during the loading process, the dislocation occurs when the indentation depth is about 0.69 nm; with the indentation depth increasing, the dislocation grows up into a dislocation loop and the plastic deformation of the substrate becomes more severe. During the unloading process, with the decrease of indentation depth, the number of dislocation loops decreases continuously; when the indenter returns to its starting position, there are still a small amount of dislocation loops in the center of the substrate, and this is the main reason for the permanent plastic deformation of the substrate.
Abstract: The low cycle fatigue (LCF) behaviors of Z3CN20- 09M austenitic stainless steel were tested by the method of radial strain control at room temperature and 350℃. The steel presents cyclic hardening followed by cyclic softening, and the degree of cyclic hardening depends on temperature and strain amplitude. With the increase of strain amplitude, the LCF life of the steel decreases, but the stress amplitude for the same cycles increases. Temperature has great effect on the LCF behaviors of the steel, the degree of cyclic hardening at 350℃ is higher than that at room temperature, and the LCF life at 350℃ is also higher than that at room temperature for the same strain amplitude. Through in-situ observations in fatigue testing, slip planes within austenite, inclusions, and austenite/ferrite phase boundaries are considered to be the possible nucleation sites of fatigue cracks. The incongruous deformation abilities of austenite and ferrite cause stress concentration in the phase boundaries and become the preferential propagating paths of fatigue cracks.
Abstract: The effects of element contents and heat treatment regimes on the precipitation morphology of α-Cr phase and the mechanical properties of K648 superalloy were systematically investigated by room-temperature tension and impact tests. The precipitation law of equilibrium phases in K648 superalloy was calculated by Thermo-Calc software. The calculated results show that the main equilibrium precipitation phases are α-Cr phase, γ' phase and M23C6 carbide. Microstructure observations indicate that the precipitation morphology of α-Cr phase is sensitive to the Cr content and heat treatment regime, demonstrating its morphological variety. Mechanical property tests further testify that the room-temperature tensile properties and impact properties are significantly dependent on the morphology and distribution of α-Cr phase, meaning that the mechanical properties of the alloy have microstructure sensitivity.
Abstract: Fe100-x-yCrxBy(x=11-20, y=9-20) amorphous ribbons with low Curie point and high saturation magnetization, which could be applied in anti-icing in transmission lines, were prepared by rapid-quenching with various technological parameters. Experimental results show that the Curie temperatures of Fe65Cr15B20 and Fe64Cr16B20 amorphous ribbons are 28.6 and 11.6℃, while the saturation magnetizations of Fe65Cr15B20 and Fe64Cr16B20 amorphous ribbons are 0.69 and 0.62 T at 0℃, respectively. Magnetocaloric effects of Fe65Cr15B20 and Fe64Cr16B20 amorphous ribbons were approximately measured and analyzed by using a self-designed apparatus on the basis of the near heat-insulation method.
Abstract: Glass ceramics were prepared by fly ash and quartz sand, and subsequently heat treated with different processes. The glass ceramic specimens with different ingredients after heat treatment were investigated. When the mass fraction of ash fly is 30%, transitional phase Ca2SiO4 precipitates at first in the specimens without TiO2 during heating at 780℃, then it dissolves and disappears during crystallization at elevated temperatures, and finally the stable equilibrium phase of anorthite precipitates. When the mass fraction of TiO2 increases from 0 to 15%, the precipitates change from fusiform Ca2SiO4 microcrystals to granular anorthite microcrystals. When the mass fraction of fly ash increases to 40% and that of TiO2 is 3.5%, a reticular structure appears, and then it will vanish when the nucleation agent of TiO2 is added to 5%. It can be concluded that the precipitation of the reticular structure is restrained by TiO2.
Abstract: High-performance coatings on diamond/Cu composite materials were obtained by nickel plating. Three different coatings prepared by two different electroless plating processes and one electroplating process were investigated and compared after welding heat treatment using a vacuum furnace. The adhesion and corrosion resistance of the coatings after welding heat treatment were tested. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to observe the surface appearance of the coatings and the phase structure before and after welding heat treatment, respectively. It is shown that after welding heat treatment, for the electroless plating coatings using sodium citrate as a complexing agent, the high temperature resistance, bonding strength and corrosion resistance are better than those of the electroplating or electroless plating coatings using butanedioic acid as a complexing agent.
Abstract: Nanoflake structured titanium dioxide was successfully prepared from electric furnace molten slag by using a hydrothermal method under the condition of alkaline solution. The effects of hydrothermal temperature, reaction time and sodium hydroxide solution concentration on the titanium extraction and morphology were investigated. Relatively pure and better crystallized nanoflake structured titanium dioxide can be obtained with increasing reaction temperature, time and alkaline solution concentration. The optimum preparing conditions are that the hydrothermal temperature is above 180℃, the reaction time is above 24 h and the concentration of NaOH solution is 12 mol·L-1. Using the as-prepared TiO2 as a photocatalyst, the degradation rate of methyl blue is above 81.1% under a xenon lamp for 90 min.
Abstract: The mercury evaporation rate, specific surface area, catalyst composition, and mercury form of high-, low-, and waste high-mercury catalysts in the acetylene PVC industry were tested by the dynamic flux chamber, specific surface area analyzer, scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. It is shown that the mercury evaporation rates of the high-, low-, and waste high-mercury catalysts are 1.04 × 10-7, 5.90 × 10-8, and 2.47 × 10-4 mg·g-1·min-1, respectively. Mercury chloride is reduced to elemental mercury after the high-mercury catalyst is used, and mercury is adsorbed on the surface of the waste mercury catalyst, causing the mercury evaporation rate of the waste high-mercury chloride catalyst much higher than that of the new.
Abstract: Based on the heat transfer model, optimization strategies were proposed for the steady and transition operating modes during steel strip continuous heat treatment processes. Feasible sets for every steel group (classed by steel grade and size) can be obtained by a heuristic optimization strategy in the steady operating mode. Based on the relations of feasible sets of different steel groups, an optimization strategy for the transition operating mode was developed, which minimized the differences between the steel strip temperature and target temperature of heat treatment by the adjustment of operating parameters. A comparison between the control strategy used in steelmaking plants and the new developed shows that the optimization strategy based on feasible sets can fulfill the transition operating mode more rapidly and control the temperature of steel strips more accurately.
Abstract: Based on the analysis of balancing in an automotive final assembly line, this paper proposed an enhanced genetic algorithm which includes a simulated annealing factor. A specific accelerated-convergence factor was designed for the algorithm to ensure fast convergence within a limited space. In the algorithm more engineering constraints were taken into consideration. The algorithm was applied to a mix-model production line, and the result shows a fast convergence and good agreement with practical engineering.
Abstract: There is no uniform algorithm for fuzzy membership, and the definitions differ. According to the characteristic of the fuzzy concept"the meaning is clear and the extension is ambiguous", the membership is defined as the subordinate degree of different extensions to the connotation. In information systems, the extension of the theory of knowledge discovery is expressed by the object, and the meaning is expressed by its attributes. Based on the research results, a new algorithm for calculating the membership was proposed:the initial information systems are composed of original statistical data, and the set-valued information system is constructed by the quotient set which uses the rough set theory; in the set-valued information system, the conditional probability in the corresponding conditional probability space is the membership. In general, the information systems are divided into information systems without decision attributes and target information systems with decision-making attributes. The membership is also divided into two categories:firstly, the content of the extension object is the value of the property itself, such as young people to the age (information system); secondly, the extension object is different from the content attribute value of another property, such as engineering safety factor to stability (target information system). These two instances were calculated, the former is compared with the existing research results and the latter is verified by the function selection, classical statistical method and Bayesian formula; it is shown that the algorithm is feasible and the results are reliable.
Abstract: The root's growing condition can reflect the climatic characteristics and soil status. Existing methods such as excavation, monolith and bisection will destroy the sample and have too much work to do. To track the root's growing addition in real time, this paper introduced a method based on adaptive thresholds and multiscale wavelet transforms, by which we can detect the edge of a root's image that obtained by endoscopy and then mosaic the images extracted from the edge. The method analyses the growing condition of the root automatically without any destroying. Through this system, we can acquire real-time collection and accurately measure the root's physical parameters.
Abstract: A performance-based fire-resistant design method was proposed for analyzing the fire safety of a large span and large space building. First, the temperatures of components are determined through fire scene analysis and simulation, then the stresses of components at different temperatures are calculated by software, thus which component needs fire protection can be determined. The main station building in Qingdao North Station is a complicated structure system, a large space layout, and beyond the specifications of fire safety design codes. According to the current standards it is difficult to satisfy the safety and economic requirements. The performance-based method was used to evaluate the fire safety of the main station building in Qingdao North Station, and some fire protection measures were given on the basis of the evaluation results.
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
