Papers by Keyword: Melting

Abstract: In this study, PP/clay nanocomposites have been fabricated at different nanoclay loadings, i.e. 0, 5, 10, and 5 wt% for the 1^st cycle and 2^nd cycle (re-processing). The prepared nanocomposites were then characterized by a Differential Scanning Calorimetry (DSC) to investigate the effects of nanoclay loadings and re-processing on the melting and crystallization of the nanocomposites. The DSC results showed that the melting temperature, T_m was not significantly affected by the nanoclay loadings and re-processing. In the other hand, the degree of crystallinity, X_c of the nanocomposites was higher than that of neat PP, but only reached a maximum at nanoclay loading of 5 wt% (i.e. 51.2% for NC-5-I and 48.3% for NC-5-II). Thereafter, the X_c decreased at higher nanoclay loadings. There was no significant difference in X_c between 1^st cycle and 2^nd cycle. Additionally, in all nanocomposites samples for both cycles, there were two crystallization temperatures, i.e. Tc₁ and Tc₂. In the overall crystallization process, the T_c of nanocomposites increased by 11-12°C compared to that of neat PP. Whereas, the onset crystallization temperature, T_oc also increased by approx. 13°C. Apparently, there was no significant effect of nanoclay loadings and re-processing on the T_c nd T_oc of the nanocomposites.

Abstract: The fuel-fired crucible furnace is very popular for melting of aluminium alloys. This melting technique provides good control of hydrogen gas in aluminium casting. The fuel type is LPG for convenience and low cost of production in small and medium foundry. However, the quality of the melt such as homogeneity of chemical composition is not good and stirring is normally required. In this paper, the rotary degassing system was used to improve the quality of the molten aluminium alloy. By control the homogeneity of chemical composition and reduces other impurities such as Iron (Fe). Two different inert gases, argon and nitrogen, were used to treat the melt. The combination of blade design, type of gas and rotation speed is the key success to improve the quality of molten aluminium alloy in this study. Moreover, this rotary degassing system can be used to control pouring temperature which is one of the most important parameters for the consistency of casting quality. Therefore, the rotary degassing system will be of benefit to control the homogeneity of chemical composition, control the pouring temperature, save production time and increase productivity of aluminium melting and casting.

Abstract: A method is described to determine geometrical dimensions of electrode metal droplets depending on short circuit duration. It provides a quantitative evaluation of the electrode metal transfer and the energy impact on metal parts being welded. It is proved that using inverter power source decreases the size of droplets transferred to the welding pool by 24% in average if compared with a diode power source. It also reduces overheating of the droplets which improves efficiency of transferring chemical elements from the electrode to the weld metal.

Abstract: The paper introduces plasma technologies developed at the Department of Applied Mechanics and Materials Science (TSUAB, Tomsk, Russia). These technologies include the processing techniques for silica glass, microspheres, and protective-decorative coatings for silicate materials using the low-temperature plasma. The plasma effect on silicate materials is described in this paper.

Abstract: Turning chips of zirconium alloys are produced in large quantities during the machining of alloy rods for the fabrication of the end plugs for the Pressurized Water Reactor (PWR) fuel elements parts of Angra II nuclear reactor (Brazil – Rio de Janeiro). This paper presents a study on the search for an efficient way for the cleaning, quality control and Vacuum Arc Remelting (VAR) of pressed zirconium alloys chips to produce a material viable to be used in the production of the fuel rod end plugs. The process starts with cutting oil clean out. The first step in this process consists in soaking a bunch of chips in clean water, to remove soluble cutting oils, followed by an alkaline degreasing bath and a wash with a high-pressure flow of water. Drying is performed by a flux of warm air. The oil free chips are then subjected to a magnet in order to detect and collect any magnetic material, essentially ferrous, that may be present in the original chips. Samples of the material are collected and then melted in a small non consumable electrode vacuum arc furnace for evaluation by Energy Dispersive X-ray Fluorescence Spectrometry (EDXRFS) in order to define the quality of the chips. The next step consists in the 15 ton hydraulic pressing the chips in a die with 40 mm square section and 500 mm long, producing an electrode with 20% of the Zircaloy bulk density. The electrode was finally melted in a laboratory scale modified VAR furnace located at the CCTM–IPEN, producing 0.8 kg ingots. The authors conclude that the samples obtained from the fuel element industry can be melting in a VAR furnace, modified to accommodate low density electrodes, allowing a reduction up to 40 times the original storage volume, however, it is necessary to remelt the ingots to correct their composition in order to recycle the original zirconium alloys chips. in a process to reduce volume and allow the reutilization of valuable Zircaloy scraps.

Abstract: This paper discusses the mathematical model of powder material particles heating in the gas flow when applying plasma gas and thermal coatings. It has been assumed that while moving in the plasma, the particle is heated by convective heat transfer and radiative heat transfer. To ensure accuracy and validity of calculation, two characteristic regions have been outlined: Core, where the temperature, density, and viscosity of plasma, as well as the other parameters are assumed as constant; and the region from the core to the coated surface (substrate), where these parameters are the functions of the plasma flow coordinates. One of the assumptions is that the shape of the particles is near-spherical, and the thermal flow’s action to the particles’ surface is uniform. Special attention has been paid to correct selection of criteria , which allowed to simplify the solution and reduce it to the ordinary first-order differential equation derived from the particle heat balance equation.

Abstract: The research and description of modern methods and procedure of welding flux manufacture are presented. The technology of welding fused flux production by influencing on the composition of mineral raw materials furnace burden (from 0,5 mic up to 0,20 mm) with electric arc (diameter graphite electrodes 6-18 mm, current from 200 up to 600 A) is proposed to be significantly reducing the labor input as well as dustiness during the operation and transport and improves mechanical properties (granules strength of 16-19 N/mm²) and surface condition of flux granules. The equipment for the granulation does not require large melting furnace and powerful transformers, fuel gas, coke or oil, i.e. welding flux is easy to manufacture.

Abstract: The physical models of the induction crucible furnaces with nonconducting crucible and conducting crucible were developed. Experimental study of the parameters of an induction crucible furnace for melting of ferromagnetic lumpy charge in ferromagnetic nonconducting crucible was made. Experimental study of the parameters of the furnace for melting copper and magnesium in conducting crucible was made. Three-position control system of active power of induction crucible furnace for melting of ferromagnetic lumpy charge and two-position control system for temperature regime of induction crucible furnaces with conductive crucible were developed.

Abstract: The results of the studies presented here are devoted to understanding of microstructure effect on the processes and properties driven by diffusion. The role of various interfaces (intergranular, phase, free surface), as the high-energy defects, is underlined and investigated with special attention. The methodology relevant to analyses of the microstructural processes is first briefly presented. The capability and limitations of classical molecular dynamics, mesoscale Monte Carlo and cellular automaton techniques are described. Two examples of the diffusion driven processes analyzed at various length and time scale are shown: namely, grain growth in nanometallic materials and melting of thin embedded films. The modeling results are also accompanied with experimental studies. Thanks to application of numerical methods, models of relevant processes were proposed, which enabled to provide quantitative relationships between microstructure and the process kinetics. Such relationships can be later used for design of optimized materials for wide range of applications.

Abstract: In this article, the problem of a non-Newtonian fluid (micropolar) flow over a horizontal melting surface in the presence of internal heat source and dual stretching (i.e. at the wall and at the free stream) is presented. Since the magnetic-Reynold of the flow is substantial, the influence of induced magnetic field is properly accounted in the governing equation. The viscosity and thermal conductivity of the micropolar fluid are considered to vary linearly with temperature. Classical models of these thermophysical properties were modified to suit the case of melting heat transfer. A similarity transformation is applied to reduce the governing partial differential equation to coupled ordinary differential equation corresponding to dimensionless momentum, angular momentum, energy and induced magnetic field equation. These equations along with the boundary conditions are solved numerically using shooting method along with Runge-Kutta-Gill method together with quadratic interpolation. The results of the present study indicate that due to the formation of boundary layer on melting surface (region of low heat energy) in the presence of induced magnetic field, space and temperature dependent internal heat generation enhances the heat transfer rate.