Continuous Removal of Nonmetallic Inclusions from Aluminum Melts by Means of Stationary Electromagnetic Field and DC Cur
- PDF / 468,730 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 21 Downloads / 212 Views
INTRODUCTION
ALUMINUM is a reactive metal, readily oxidizing when exposed to the atmosphere. It forms stable oxides and nonmetallic inclusions during the melting and handling process. Inclusions once formed and if not removed prove detrimental to mechanical properties and reliability of the finished component. Inclusion removal from aluminum melts and their alloys is an important melt treatment process. The increasing demand for high integrity components used in automotive, aviation, construction, electrical, and other industries requires super clean metal. Increased attention is being given within the industry to find new or improved processes to efficiently refine and remove very small inclusions from aluminum alloys. Various methods are currently being used within the industry to remove inclusions from aluminum alloy melts. These include the use of holding furnaces,[1] rotary degassing systems using nitrogen,[2] argon,[2] chemical additives, emitting inert gases,[3] filtration,[4] etc. Typically only larger type inclusions can be removed by holding the melt in furnace. More recently rotary degassing has been adopted to reduce hydrogen gas in the melt and to assist with inclusion removal. Filtration is widely adopted and some new advances in filtration methods are being studied and used in the industry. Ceramic foam filter (CFF), for example, will effectively remove inclusions larger than 40 lm, and efficiencies as high as 90 pct can be obtained, while the ability of CFFs ZHENMING XU, Professor, TIANXIAO LI, Lecturer, and YAOHE ZHOU, Professor, are with the School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, People’s Republic of China. Contact e-mail: [email protected] Manuscript submitted March 6, 2006. Article published online May 25, 2007. 1104—VOLUME 38A, MAY 2007
to remove inclusions less than 10 lm is only 30 pct.[5] Rigid media tube filtration is effective in removing smaller inclusions, but productivity is low due to the low flow velocity (0.6 to 0.7 mm/s)[5] of melt through the filter. More positive methods for inclusion separation are currently needed. Electromagnetic separation is therefore considered to be a promising alternative method to remove all types of nonmetallic inclusions from aluminum alloy melts, because this method can remove even microsized inclusions, in principle, and has high efficiency and availability compared with other refining techniques. During recent years, several methods of imposing electromagnetic force (EMF) on aluminum alloy melts have been investigated and the results reported by various researchers.[6–9] Most having focused on the principles of electromagnetic separation and the moving law of inclusions, but few have focused on the continuous removal of inclusions. To date, the removal of inclusions of less than 20 lm by electromagnetic separation has not been successful.[9] This article focuses on the process to continuously remove small inclusions from aluminum melts and its alloys. II.
EXPERIMENTAL TECHNIQUE
Figure 1 shows a schematic ill
Data Loading...
