Advanced Materials Research Vols. 881-883

Abstract: Nondestructive inspection and evaluation of welds is very important to ensure the safety of industrial products. In this study, the metal magnetic memory (MMM) and alternating current field measurement (ACFM) methods are utilized to characterize welding defects of a butt welded tubular specimen respectively. The results show that the MMM method has potentials in evaluating both early stress concentration and macro-defects but only qualitatively, while the ACFM method can provide crack depth sizing information quantitatively, suggesting that the two methods should be combined for nondestructive evaluation welding defects to improve the detection efficiency and accuracy.

Abstract: The steady state extrusion process of a complex, multi-hole aluminum extrusion die was simulated using the Arbitrary Lagrangian Eulerian (ALE) algorithm. According to the numerical simulation results and the extrusion experiment, a combined method of modifying the portholes, double-step welding chamber and adjusting bearings were proposed for qualified profiles. In this study, the influence of the shape of portholes and double-step welding chamber on the material flow velocity distribution at the outlet were emphatically analysed, and some reference value for the designing and modifying of multi-hole die is existed basing on the method.

Abstract: In this paper the activity calculation model for SiO2-Al2O3-CaO-MgO-FeO-MnO slag system has been established according to the molecule-ion coexistence theory. From that the activity of each component in the converter slag at steelmaking temperature can be calculated and then provides the basis for analyzing the equilibrium distribution of element between slag and steel, as well as thermodynamics analysis related to the activity.With the increasing of FeO mass fraction, the activity of 3CaO.SiO2 shows a significant decreasing trend and the activity of MnO.SiO2 and 2MnO.SiO2 increases slowly. The activity of 3CaO.SiO2 increases at first then decreases, with the increasing of basicity. When the basicity w(CaO)/w(SiO2)=3, the activity of 3CaO.SiO2 reaches its maximum value. The activities of MnO.SiO2 and 2MnO.SiO2 decrease gradually.

Abstract: While using water cooled mold to produce steel ingot, an air gap is generated between the ingot and the mold, which has an important influence on the ingot quality. The air gap formation law and its influence on the solidification process were calculated by used FE software Procast. It is shown that, air gap occurs in a few minutes after the solidification begins. In 75-100s later the gap reaches 0.2-0.5 mm and starts to influent the heat transport significantly, the rate of the temperature decrease becomes slower. When the solidification is finished, there is a lager gap on the two narrow surfaces than it on the other wide surfaces; and the gap on the two narrow surfaces is different. The air gap on the narrow surface close to the sprue has a width of 12-20 mm; on the other narrow surface away from the sprue has a width of 4-13 mm. The biggest gap on the two wide surfaces has a size about 6.5mm. For the air gap is formatted between the ingot shell and the ingot mold, the solidification time is 50% longer than that of without air gap.

Abstract: s: Electron microprobe technology is widely used to component analysis of metals, minerals and geology. Elements of sedimentary rock including B, Ga, Ba, Sr, Co, V, Cr, Mn, Fe, Ni were analyzed by EPMA respectively. It was discussed that marine faces and continental facies, oxidation environment and reducing environment, the depth of water and salinity influence on sedimentary rock, respectively. Then the influence of marine faces, continental faces, oxidation environment, reducing environment and the depth of water and salinity on sedimentary rock was discussed respectively. The results show that EPMA is a useful instrument to analyze the components of sedimentary rock.

Abstract: Based on the condition of fully mechanized caving face in one mine, two methods of microseismic monitoring and numerical analysis were combined to study the evolution characteristics and development law of floor failure depth in extra-thick coal seam. Microseismic monitoring results show that the number of microseismic events partly reflects the influence of mining disturbance in the roof and floor rock mass. The distribution of microseismic events are intensive near the coal mining face, which show the floor rock mass is seriously damaged during the coal mining. The greatest floor failure depth estimated from mine microseismic monitoring is 31 meters. Numerical analysis indicate that the rock stress around the mine stope is redistributed during the coal mining, due to the effect of mining disturbance. The abutment pressure increases in front of the coal mining face and the stress reduces in the mined areas. The concentration and release of the stress makes contribution to the destroy of the floor rock. The maximum floor failure depth is up to 28 meters calculated from numerical simulation. The consistency of microseismic monitoring results and numerical analysis improve that it is effective and reliable to obtain floor failure depth and considerably possible to predict the water inrush using microseismic monitoring technology with its inherent ability to remotely monitor the progressive failure caused by mining. The research results have great popularization and application values for the similar mine.

Abstract: The modified Siemens process is the primary technology of polycrystalline production at present. The Siemens reactor, which is the main equipment in the modified Siemens process, consists of a chamber where several high purity silicon slim rods are heated by an electric current flowing through them. The temperature on the rod centre must be under melting temperature of silicon (1687K) in order to avoid its breaking-down because of an uneven temperature profile of the silicon rod. Therefore the temperature profile of the silicon rod heated by direct current (DC) has been investigated by molding. The current density profile of silicon rod has also been studied to investigate the interaction of current density and temperature. The results show that the temperature is not homogeneous in the rod and the temperature in the center of the polysilicon rod is 1750K which is much higher than the melting temperature (1687K) when the temperature is 1423K on the surface of polysilicon and the radius of rod is 5cm. Therefore, the maximum growth radius of the polysilicon rod in Siemens reactor should be less than 5cm when the joule heating generated by DC. The current density increases from the center to the surface of the polysilicon rod.

Abstract: The Euler-Euler two-fluid model incorporating the kinetic theory of granular flow was applied to simulate the gas-solid flow in fluidized beds. The pressure drop, particle distribution and motion characteristics were studied in this paper. In order to investigate the effect of structure of the fluidized bed on flow characteristics, fluidized beds with different diameters and structures were applied. User defined functions (UDF) were applied to study the flow characteristics when the particle size and mass changed over time. The results showed that with the increase of particle size, higher minimum fluidization velocity was required, but lower pressure drop was obtained. For a certain fluidizing medium, the bed critical fluidization velocity depended only on the size and nature of the particles. The structure of a fluidized bed had an influence on the particle distribution and motion characteristics.

Abstract: Based on multiphase flow theory and calculation method, the distribution of internal multiphase flow field in the vertical rise pipeline of natural gas hydrate is simulated with FLUENT as a tool and the mixture of natural gas hydrate solid particles and water as a medium. The change rules of velocity field and volume concentration field are described and the effect of solid particles diameter, density and volume concentration of the natural gas hydrate on the pressure loss and resistance loss of pipeline is also analyzed deeply. It provides theoretical basis on transporting of natural gas hydrate solid particles by pipeline. Keywords:natural gas hydrate. pipeline. solid-liquid two-phase flow. kinetic characteristic. numerical simulation.

Abstract: The numerical model of SCR denitrification system is established. Simulate the SCR system where installs mixer by the way of installing rectifier grille and three types of guide plates to analyze the changes of velocity, pressure and ammonia concentration before catalyst layer. The results indicate that setting rectifier grille and changing the guide plate size can make velocity and pressure of the whole flow are more stable. In plan 4, the deviation of ammonia concentration at the catalyst inlet section is 3.58%, avoid the phenomenon of ammonia escape and its satisfies the design requirements of SCR denitration system Keywords: SCR denitrification system; rectifier grille; guide plates; pressure drop