Furnaces for magnesium: Medium-frequency coreless induction furnaces

In recent years, magnesium castings have virtually undergone a revival, particularly in the automotive industry with a view to weight saving.

Similar to aluminium, the primary energy consumption for the production of magnesium is several times that required for the remelting of scrap. Therefore, recycling is an important issue in both cases.

Apart from the so-called "in-house recycling" of clean, sorted returns, the coreless induction furnace is traditionally used for melting down the remaining scrap. Special melting salts are used for refining the melt.

This is where the advantages offered by the coreless induction furnace come to the fore:

• „ Due to the pronounced bath movement, there is intensive contact between the melt and the salt particles, the salt can be used econonomically and the treatment times are short.

• „ The thermal load on the steel crucibles normally used for this purpose can be considerably reduced by the OTTO JUNKER Power Focus technology which allows a close control of the energy applied onto the crucible over its height so that overheating in the upper crucible area with a partly filled crucible can be avoided.

• „ Compared with other furnace types, the overall power density of coreless induction furnaces is extremely high making them a powerful and compact melting tool.

The most frequently used casting process for magnesium alloys is pressure die casting. Currently, a combination of melting and dosing furnaces is normally used for this purpose. Usually, these are resistance-heated which, due to the lower power density, requires a high capacity relative to the melting rate. Apart from the potential risk of fire, this also means a relatively high demand for environmentally critical reactive protective gases.

OTTO JUNKER are cooperating with users on a so-called INLINE melting process where the amount of melt required by the pressure die casting machine is molten down "just in time" by induction with a high power density and then held available in a relatively small melt collector which also contains the dosing unit. Such a plant is compact with the ever present melt volume being as small as possible, thus drastically reducing the protective gas requirement.