b"Engineer Innovation | Heavy EquipmentThe Pure Perfection of Electromagnetic Suspension in Induction FurnacesDr. Vitaly Peysakhovich, President, Elmag CorporationAn induction furnace is an electrical4 4furnace in which the heat is applied by6induction heating of metal. This a clean,6energy-efficient and well-controllable melting process compared to most other5means of metal melting. 5Induction furnaces with cold crucibles (CCIF) are broadly used for the melting of super-pure metals and alloys as they2reduce load contamination compared to7traditional furnaces with the ceramic crucible. This is due to the water cooling7system employed. 11However in some application, the verya) 3 b)small contamination that happens at3contact of the molten metal with coldFigure 1: 3D models of furnaces with cold crucible. a) solid load,12- sections crucible, 1/4 of copper is unacceptable. A higher level furnace; b) partially molten load, 24- sections crucible, 1/8 of furnace; -solid load, 2-molten load, of purity requires full elimination of3-crucible bottom plate, 4-crucible sections, 5-gaps between sections, 6-flux ring, 7-induction molten metal contact with cold cruciblecoil. Note: water cooling system of cold crucibles is not shownwalls in the process of melting. The goal can be reached by holding molten metalThe description of this developedexample of magnetic field distribution in in suspensive condition in the process ofmethod is done on a concrete example: an induction furnace with cold crucible.melting. Practically, the electromagnetic (EM) field of the coils in this furnace Load: material is titanium, solid loadMagnetic flux created by an induction have to not only create the heat fordiameter is 76 mm, initial load heightcoil can be conditionally divided into induction melting, they also need tois 100 mm, temperatures (degreesthree parts: provide EM suspension of melted metal.Celsius) (initial is 20, melting is minus 1660, overheating is minus 1800), Coil flux leakage; Each induction melting furnace createslatent heat fusion is 419 kJ/kg.Flux along the crucible's sections ; andsome meniscus of molten metal in the Cold crucible: material is copper, Flux that passes to the load through process of melting. minimum initial diameters are fromcrucible sections.80 to 140 mm, height is 273 mm, As a rule, the meniscus volume is verynumber of sections are 12 and 24,The ratios between the three parts of small and does not have any influencegaps between sections are 0.5 mm. magnetic flow determine the efficiency on the melting process. In the full Induction coil (combination ofof the furnace. The more that is part of suspension case, the molten meniscuscylindrical and conical groups ofload magnetic flow, the higher the volume has to be commensurable withturns): material is copper, minimumefficiency.the full load volume of furnace, ideally,inner diameter is 166 mm, height is 100 percent of it. Creation of such160 mm The number of sections has a very strong furnaces is an independent problem that Electrical parameters: frequency isinfluence on the cold crucible as well as requires the development of a10,000 Hz, nominal inverter power ison all the furnace parameters. Comparing calculation method that has to take into100 kW, upper limitof coil voltage issimulation results between crucibles with consideration a combination of closely1000 Volts, upper limit of coil current12 and 24 sections shows that useful bound electromagnetic, thermal,Amps. magnetic flux and the electrical efficiency hydrostatic and electro-dynamicof the furnace with the 24-section processes. The objective of the article isLets recall how the cold cruciblecrucible is significantly higher than in the to show such a calculation method. furnaces works. Figure 2 shows anfurnace with the 12-section crucible. The 34"