Papers by Keyword: Degassing

Abstract: In the current advancing world, operability and ease in processability of a material define its selection criteria for the intended applications. Hence, the industrial applications requiring high temperature sustenance, strength and corrosion resistance desperately demand the materials which employ simple processing in an economical way. Contemplating last few decades, it has been discovered that industries like petrochemical, power generation, nuclear energy, etc. greatly relied on nickel-based alloys till Fe-Ni-Cr based alloys were not introduced. The usable components are obtained either in cast or wrought form as per requirements. Fully killed alloy, developed under controlled conditions with some precautions during the casting process can lead to sound casting. The current study adopts a novel preliminary approach to control the quality of cast UNS N08120 material and minimize the possibility of defect generation. The possible reasons behind cast defects and how they transform into intrinsic defects have also been discussed. Calcium-based fluxes are introduced to molten metal as a degassing agent for the elimination of lighter impurities and entrapped gases. By the addition of quicklime (CaO) as a flux material during the sand casting process, an attempt has been made to reduce the presence of gases and impurities by more than 80%.

Abstract: This research is aimed to get a better understanding on the effort of reducing the porosity level in aluminum alloys. The degassing process (2, 5 and 8 minutes) is done to reduce the hydrogen content in liquid aluminum and cooling rate modifications (13 °C / min, 20 °C / min and 26 °C / min) was performed to reduce the porosity by reducing the size of Dendrite Arm Spacing (DAS). The casting method used in this research is sand casting and raw materials were melted using an electric furnace at 720 °C. The microstructural images showed the DAS size are decreased by size from 137.3 μm to 87.58 μm obtained from cooling rates of 13 °C / min and 26 °C / min respectively. In the other hand, the level of porosity is also decreased from 3.58% at 2 min degassing and the cooling rate of 13 °C / min to 1.8% at 5 min degassing and 26 °C / min cooling rate. Furthermore, the tensile test results show that the value of tensile strength increases when the DAS size and porosity level are smaller. The highest ultimate tensile strength value is 105.9 and the lowest is 70,53 MPa.

Abstract: A system was developed to test the outgassing of materials intended to use in Extreme Ultraviolet Lithography (EUVL). Clean high vacuum was achieved on the background by proper cleaning, processing and assembling, as well as by combining the magnetic levitated molecular pump with the dry mechanical pump. Much more care should be taken to operate this system to avoid introducing any contamination. Once the vacuum chamber is polluted by high-risk items like water (H₂O) and hydrocarbons (C_xH_y), it should not be applied again. It is recognized experimentally that clean vacuum could be recovered by flushing with dry gases, baking and degassing, and baking is undoubtedly a more effective technique in efforts of controlling the pollution.

Abstract: Ultrasonic melt processing of light alloys has enjoyed a revival in the last 15 years. Although the scientific foundation and first examples of industrial application date back to the 1950s–1970s, the technological application of ultrasound in melt and solidification processing has not been fully accomplished. In recent years, the availability of advanced reliable equipment, new basic knowledge gained through modeling and dedicated experiments, and the industrial demand for clean, environment friendly technology sparked an interest in this technology and ensuing research. This paper reports on the currently achieved level of ultrasound application in light metal processing, i.e. degassing and grain refinement of light alloys and metal-matrix composite material manufacturing, and discusses challenges that still prevent large-scale implementation, both from fundamental and applied points of view. The main mechanisms underlying the effects of ultrasonic processing such as cavitation in melts, nucleation and fragmentation of solid phases, forced convection induced by cavitation zone and acoustic streaming, and mixing and distribution of solid inclusions are explained. The paper is illustrated by examples of research done under the supervision of the author.

Abstract: Hydrogen as the main cause of the gas porosity in aluminium alloys should be removed before casting. The degassing process with intensive melt shearing shows a high efficiency. In the present work, the water simulation was used to study the high shear degassing process and the effect of rotation speed on the size and distribution of inert gas bubbles. The results show that with the increase of rotation speed, the bubble size decreases and the affected region becomes larger. The proper rotation speed of the rotor for the rotor-stator high shear degassing process is 5000-6000 RPM.

Abstract: The mechanical and physical properties of epoxy-clay nanocomposites are known to be significantly affected by the dispersion and distribution of the clay particles in the epoxy matrix. The degree of dispersion of the clay particles in the epoxy matrix depends mainly on the processing parameters used to synthesize the nanocomposite.In this paper, the optimized high shear mixing parameters determined in an earlier work were used to disperse five different loadings of Nanomer I.30E nanoclay (1, 1.5, 2, 3 and 5 wt%) into DGEBA epoxy matrix. A systematic approach was adopted to optimize the degassing process of the mixture. X-Ray Diffraction (XRD) analyses showed that the optimum nanoclay dispersion was achieved for a degassing temperature of 120 °C. The flexural strength of the developed nanoclay/epoxy composite is found to increase by 15% for 1.5 wt% and due to the high stiffness of the clay, as compared with epoxy resin, the flexural modulus improved continuously with clay loading. The observed reduction in strength and fracture strain at high clay loadings is mainly attributable to the presence of clay agglomerations and voids formation. The diffusion of water molecules and maximum moisture uptake of epoxy are reduced considerably by the presence of nanoclay.

Abstract: Ultrasonic melt processing enjoys the revival of interest in the last 1015 years. Although the main fundamental works as well as lab-scale and pilot-scale demonstrations date back to the 1950-1980s, the ultrasonic melt processing of light metals has not become a major technology. Recently the deficiencies of current technological approaches brought back the interest to ultrasonic treatment for degassing, grain refinement and composite materials. The current attempts to repeat the earlier results, to gain more fundamental insight using advanced means available and to up-scale the positive effects to the industrial scale show frequent lack of understanding of the basic controlling mechanisms. This paper describes the main mechanisms of ultrasonic melt processing, shows frequent mistakes, and gives some guidelines for technology up-scaling. The paper is illustrated with the latest experimental results.

Abstract: This article discusses research on using power ultrasound for degassing of molten aluminum alloys. At least three types of technique have been developed for ultrasonic degassing. The type deals with degassing using power ultrasound alone. Degassing in a small melt can be achieved within a few minutes of ultrasonic vibration. The second type is ultrasound assisted vacuum degassing. A combination of vacuum and power ultrasound makes degassing much complete and fast. The third type is ultrasound assisted lance degassing. Ultrasonic vibration is used to break up the large argon or nitrogen bubbles into much smaller ones, resulting in an increased efficiency of degassing of aluminum melt. The benefits of ultrasonic degassing include: no moving/rotation part in the degassing system; less use of argon and no use of chlorine; and less amount of dross formation during degassing. Furthermore, trace elements such as Na and Li can be removed using ultrasonic degassing. Keywords: Aluminum alloys, degassing, porosity, and power ultrasound

Abstract: Silicone rubber mold is frequently used in the indirect tooling. Automatic vacuum casting system is widely used to degas in the manufacturing of silicone rubber mold, but the cost of hardware is very expensive. A low-cost automatic vacuum degassing system is designed, build and test in this study. Optimized parameters for degassing process are investigated. The saving in the degassing time is about 23.4%.This system offers many advantages such as reducing human error of operator, reducing noise and air pollutions derived from the vacuum pump of the vacuum casting system.

Abstract: The present research aims to study the effect of various combination of salt and metal modifiers (SrCl₂, KCl and NaCl salts with NaF including Sb & Sr ) on the locally developed A356 Al-Si alloy. A series of different heats with these modifiers were prepared using a pit type furnace. Casting of the molten metal was carried out using sand casting technique and fluxes at various stages followed by degassing. Sr modifier was used as Al-Sr master alloy, while Sb metal was used in high purity form. However salt modifiers were thoroughly dried before plunging at the bottom of the crucible containing the molten metal. It was observed that the samples containing Sr as modifier showed the best results in terms of microstructure & tensile properties as compared to Sb modifier. A combination of SrCl₂, KCl with NaF showed almost the similar and well modified microstructure with better tensile properties as compared to the samples containing NaCl with NaF salt modifier.