Experimental and numerical study of the cold crucible melting process

Abstract

The Cold Crucible, or Induction Skull Melting process as is otherwise known, has the potential to produce high purity melts of a range of difficult to melt materials, including Ti-Al alloys for Aerospace, Ti-Ta and other biocompatible materials for implants, Silicon for photovoltaic and electronic applications, etc. Induction currents melt the alloy in the crucible and partially suspend it away from water-cooled surfaces. Strong stirring takes place in the melt due to electromagnetic forces and very high temperatures are attainable under the right conditions. In a joint numerical and experimental research programme, various aspects of the design and operation of this process are investigated to increase our understanding of the physical mechanisms involved and to maximise efficiency. A combination of FV and Spectral CFD techniques are used at Greenwich to tackle this problem with the experimental work taking place at Birmingham University. Results of this study presented here, highlight the effects of turbulence and free surface behaviour on attained superheat and also discuss coil design variations and dual frequency options that may lead to winning designs.

A Combined Electromagnetic Levitation Melting, Counter‐Gravity Casting, and Mold Preheating Furnace for Producing TiAl Alloy

“…Meanwhile, to provide a high‐quality melt for TiAl casting, the melting process should be conducted in a high‐vacuum chamber with inert gas protection. Note that an excessive input power is not preferable, as the liquid meniscus is unstable and the evaporation of Al is severe under these circumstances…”

Purification of metallurgical silicon through directional solidification in a large cold crucible

“…Furthermore, the cold crucible can be reused and handled easily, while the quartz crucible is disposable which leads to cost increase. Small quantity silicon purification by cold crucible has been carried out in laboratory [17][18][19][20][21][22][23]. For the large scale cold crucible aimed at industrial production, it is necessary to study the melting technology since the process is more complicated, especially the induction heating on silicon.…”

Induction melting process using segmented graphite crucible for silicon melting

“…This skull prevents the contamination from the crucible and protects the crucible against the hot melt [1]. However, this process shows poor energy efficiency because large part of input energy is lost to water-cooled crucible [2]. Thus, metallic crucible is slitted and several segments are isolated electrically each other to improve the energy efficiency by providing sufficient electromagnetic transparency of crucible [8][9][10].…”

“…Induction melting process is well-known to be an effective method for melting high-purity metals such as titanium, tantalum, niobium and molybdenum [1][2][3][4][5][6][7]. The energy for melting is transferred via the electromagnetic field from the induction working coil.…”