Advanced Materials Research Vols. 154-155

Abstract: Submerged entry nozzle (SEN) bottom structure plays an important role in determining the flow pattern in continuous casting process. This work applies a water model to evaluate the pointed-bottom, flat-bottom and recessed-bottom nozzle performance in ultra-thick slab mold. The jet properties and surface flow are compared for the three kinds of nozzles quantitatively. The results show that flat-bottom and recessed-bottom nozzles are similar in flow pattern, but the pointed-bottom nozzle has smaller jet angle, thinner flow pattern, larger surface asymmetry rate, and higher surface flow intensity.

Abstract: The experimental investigation was carried out to compare resistance spot weldability of BIF340 and St14 steel in different weld processes.The spot weld microstructure and properties of two steels were analyzed.The results shown that : resistance spot weldability of BIF340 is better than St14.The optimum parameters of BIF340 were as follows: welding current was 6KA,welding time was 7 cycles, electrode force was 2800N. With the same welding process parameters, the microstructure of BIF340 spot weld was homogeneous and fine-grained, and the tensile shear strength was higher than St14.

Abstract: In this paper the influence of gypsum-water ratio, filler types and calcination temperature on gypsum bending strength were analyzed by the means of experiments. Spiral-shaped gypsum mold was made by gypsum molding material and mobility experiment was conducted on Pb-Sn alloys. Compared with pure gypsum, gypsum mixture had better mechanical properties. The fluidity of the alloy in the gypsum mold was prone to casting pressure, pouring temperature and alloy ratio. The research results have benefit to the development of gypsum casting technology.

Abstract: Experimental results indicate the previous theoretical model cannot predict well the surface roughness in single-point diamond turning on a precision lathe. In solving that, an improved model was presented in this paper. The difference between the previous model and the improved model is that the relative tool-workpiece vibration is measured before cutting operation using a capacitive displacement sensor in the previous model whilst the vibration is extracted from the measured surface profile in the improved model. The relative vibration was first studied under various cutting conditions to establish the vibration modes under corresponding cutting conditions. Then the surface roughness was predicted based on the vibration modes. The results prove that there is good agreement between the predicted values and measured values and the improved model is useful and reliable.

Abstract: This study demonstrates nano-scale lithography process on localized (100) silicon (p-type) surface using modified AFM apparatuses and controlling methods. AFM-based experimental apparatuses are connected the customized pulse generator that supplies electricity between conductive tip and silicon surface maintaining constant humidity during processes. Then pulse durations are controlled according to various experimental conditions. The pulsed electrochemical reaction within the gap between conductive tip and silicon surface induces the formation of oxide with nano-scale topographies. Various heights and widths of oxides can be created by AFM surface modification according to various pulse durations and applied electrical conditions under humidity environment. In addition, it can be known that oxides are completely removed after sample surface is etched in diluted HF solution, which shows micro/nano-scale grooves can be fabricated after predefined chemical treatment. They are wider than oxides widths and have several nanometer depths. Nano patterning technique from this experiment suggests that pulse electrochemical machining process has bright potential for advancing nano machining technologies.

Abstract: In the present study, an axis-symmetric electro-thermo-mechanical model has been developed to analyze a deformation process by continuous resistance heating. To obtain the transient temperature field prior to forming, a novel temperature-dependent model of the contact resistance was developed in the thermal-electrical analysis. The influences of the contact resistance, the current intensity and the die geometry on the temperature distribution were investigated. In the subsequent electro-thermo-mechanical analysis of the forming process by continuous resistance heating, the variations of the billet temperature distribution, forming force were obtained. The simulation results correspond well with experimental measured values. Furthermore, the influence of a current increasing during forming on the billet temperature and forming force was predicted in order to optimize the forming technology by continuous resistance heating.

Abstract: The purpose of this study is to evaluate the effect of filler metals in the gas metal arc welding (GMAW) process on the Aluminium alloy of AA 6061-T6 welded joints. 6 mm thickness plate with single V butt configuration was used and welded using two different fillers ER 4043 and ER 5356 and controlled welding parameters. The relationship between hardness and microstructure of the welded parts were studied and compared and the results showed that the post weld mechanical property has decreased especially for the filler ER 5356. The hardness at the heat affected zone (HAZ) of ER 5356 also has reduced almost 85% compared to the hardness of AA 6061 base metal. The microstructure of ER 4043 welding material shows the shape of columnar grains and dendrite structure. Microstructure morphology of ER 5356 welding material shows dendrites and intermetallic particles (Mg2Si) have partially dissolved and scattered in the welding material.

Abstract: The BaCo0.7Fe0.2Nb0.1O3-δ (BCFNO) membranes combined with Ce0.8Re0.2O2-δ (Re=La, Y) layer on the permeation side were used for hydrogen production by partial oxidation reforming of coke oven gas (COG). The Ce0.8Re0.2O2-δ improved the oxygen permeation flux of the membrane by 11–28% at 750 oC. The high oxygen permeation flux achieved using the Ce0.8Re0.2O2-δ surface-coating layer in this work are quite encouraging with a maximum value reaching 19.7 ml/cm2•min at 900 oC, which will be promising surface modification materials in the catalytic partial oxidation reforming of COG.

Abstract: For cold rolling process, the theoretical Bland-Ford-Hill model and Hitchcock model are used for the rolling force and roll flatten radius calculation. Friction coefficient and deformation resistance are calculated with empirical regression models. From rolling force model, the recalculation model for the friction coefficient and deformation resistance can be derived. After rolling, with actual measured data, friction coefficient and deformation resistance can be recalculated, and model parameter can be got by regression method. The practical application verifies that the accuracy of rolling force calculation model is good.

Abstract: With the development of mobile communications, gallium arsenide integrated circuits (GaAs IC) have been widely used. For example, satellite communication technology, satellite TV, wireless data transmission, fiber optic communications equipment, automatic test equipment etc. At the same time, it demands that the GaAs chips should have high quality surfaces. In this paper, it takes non-abrasive cryogenic polishing technique to polish GaAs chip surfaces. It has recorded the actual measurement results. The results show that the surface roughness of the ice disk polishing can achieve nanometer scale. Through the research of non-abrasive cryogenic polishing, it has analyzed different parameters on the impact of surface quality.