In hot-chamber die casting machines for magnesium, the machine furnace is part of the pressure die casting unit and is directly fitted to the machine, which is exemplified in Fig. 1.
Magnesium machine furnaces can be used to hold magnesium alloys at hot-chamber die casting machines under controlled and safe conditions. Upon inserting the goose neck, dosing of the magnesium melt into the hot-chamber die casting machine can take place fully automatically.
Magnesium machine furnaces are designed as single- or double-chamber crucible furnaces, with the latter being equipped with separate melting and goose neck chambers. The double-chamber design makes it possible to keep the melt level in the goose neck chamber constant, ensuring stable pouring conditions at the die casting machine.
Magnesium machine furnaces are usually equipped with electric heaters. A schematic representation of an electrically heated machine furnace with an inserted goose neck is shown in Fig. 2. In the dual-chamber design, there is a separate shielding gas supply (see Shielding gas or Shielding gas mixing machine) for the melting chamber and the goose neck chamber. If no liquid metal feed is provided, special magnesium machine furnaces can also be designed and used as melting furnaces.
In this case, the machine furnace is designed with a higher connected load and preferably includes a pre-heating and loading unit for drying and feeding ingots (see Magnesium pig heat-up device).
An overview of the technical data of ovens from a leading manufacturer of magnesium machine furnaces is given in Table 1.
Figs. 3 and 4 show single-chamber crucible furnaces of different melting rates which are used in connection with hot-chamber die casting machines. The goose neck is integrated into the crucible cover plate and sealed air-tight with a ceramic sealing strip, enabling oxide-free casting. The furnace is heated by means of electric heating coils.The melt surface is covered by a shielding gas atmosphere.
The machine furnace can either be loaded manually or fully automatically by means of a magnesium pre-heating and feeding unit (see Magnesium pig heat-up device).
Fig. 5 shows a double-chamber crucible furnace which is used in conjunction with hot-chamber die casting machines. Due to the increased melting rate, long-life bayonet heaters which can be serviced without taking the crucible out are used in these furnaces.
The heating elements are regulated in two separate zones so that the temperature levels in the melting chamber and the goose neck chamber can be set independently of each other. The double-chamber construction also means that, during loading, no swirling takes place in the goose-neck chamber. The melt surfaces are covered with shielding gas in two separate atmospheres which can be adjusted individually. The goose neck is integrated into the crucible cover plate and sealed air-tight with a ceramic sealing strip, enabling dosing free of impurities.
Like the single-chamber furnace, the double-chamber machine furnace is either loaded manually or fully automatically using a magnesium heat-up and loading device.
Magnesium melting and dosing furnace
Magnesium alloying system
Magnesium hot-chamber furnace