A Technique for Eliminating Crucibles in Heating and Melting of Metals

Abstract

An original method of heating and melting metals without a crucible, by suspension in space with an electromagnetic field, is described. The required field was generated by applying high frequency alternating current to two coaxial coils connected in series opposition. Stable levitation and heating of various metals in the solid state was obtained between the coils in the vicinity of the common axis, both in air and in a vacuum. Weights levitated ranged up to 550 grams. In air, some tens of grams of Al, Sn, and a brass were brought to melting and continued in levitation while in the liquid state. In a vacuum, 10 grams of Al was successfully levitated molten. On the other hand, several attempts to levitate molten Ag, Ti, and Zr in a vacuum failed.

Measurements of Heat Capacity of Pure Titanium and Zirconium by Electromagnetic Levitation

“…and x = R πµf σ (10) Here, µ is the magnetic permeability of the sample, R is the radius, and σ is the electrical conductivity of the sample. I peak is the current in the induction coil and f is the alternative current frequency.…”

“…By proper choice of the modulation frequency, the transient effects of external and internal thermal relaxations can be ignored with errors of only approximately 1 % [3], and then as discussed below, the unknown specific heat can be calculated if the sample's emissive properties are known. The electromagnetic levitation technique [10,11], combined with the modulation power method, is an excellent experimental technique that allows containerless heat capacity measurements on electrically conductive samples. This is very important in the case of reactive metals like titanium.…”

Electromagnetic levitation micromotor with stator embedded (ELMSE): levitation and lateral stability characteristics analysis

“…(Fukatsu et al 1999;Gindila and Kraft 2003;Murakoshi et al 2003) The electromagnetic levitation motor proposed in the paper is a kind of micro system, in which electromagnetic eddy current levitation is adopted to realize the stable levitation. The drawback of electromagnetic eddy current levitation is the heat loss due to resistance heat of eddy current (Bedford et al 1939), so in macro system it is usually used as melting system (Wroughton et al 1952), and is rarely used in levitation transportation system or suspension bear. However, for electromagnetic eddy current levitation in micro system, the heat loss of eddy current is proportional to the volume of levitated body.…”

Some Stability Considerations in Levitation Melting

“…Okress and Wroughton (4,5), in particular, have experimented with a number of coil designs. Figure 1 shows some of the possibilities.…”

“…Most experimenters (3)(4)(5)8) have noted such limitations in mass for their particular apparatuses, and both Polonis (2) and Weisberg (9) have recorded the suspicion that this limitation should be implicit in the system, and some function of mass density and surface tension.…”