Die casting high pressure

Hot-chamber HPDC machines comprise a molten metal reservoir, the die, and a metaltransferring device, which automatically withdraws molten metal from the reservoir and forces it under pressure into the die. A steel piston and a cylinder system with a gooseneck is used to create the necessary pressure within the die. A gooseneck machine utilises a cast iron channel to transfer the molten metal from the reservoir to the die. Pressures can range from a few bar to over 350 bar. Hot-chamber techniques are mainly used for zinc alloys and magnesium alloys. 

Two principal types of machine are used in the production of die-castings by high-pressure methods hot-chamber and cold-chamber machines. 

A section through a machine of this type is shown in Fig. 18.3. As shown, the furnace and the crucible containing the molten metal are contained within the machine. 

The casting cycle starts with the moving machine platen, to which one die half is attached, being pushed forward, usually by a pneumatic cylinder, until it locks against the other die half attached to the fixed machine platen. Only when the dies are completely locked does the safety system allow the plunger to be depressed. 

As the plunger is depressed, it covers up the filling port and so prevents molten metal escaping back into the crucible. The molten metal is forced through the goose-neck into the spme bush and fills the die cavity. To enable air to escape from the die cavity, small channels known as vents are machined from the cavity across the die face. These vents 

When the die is filled, the plunger is returned to the up position, the molten metal in the nozzle flows back into the goose-neck, and the injection cylinder refills through the fining port. 

Meanwhile the molten metal in the die has solidified, due to the lower temperature of the die. The die is maintained at the correct temperature by circulating cold water through it. 

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H.E. Kadir et al Fatigue crack growth mechanisms in high-pressure die-cast magnesium alloy. Metall. Mat. Trans. A 39, 190-205 (2008)... 

Figure 2.46 Cold-chamber and hot-chamber high-pressure die-casting devices [42, US EPA, 1998]...

ZL3 is a general-purpose alloy used in hot-chamber high-pressure die-casting for the engineering and automotive industry, household equipment and utensils, office equipment, locks and toys. It is easily machined, polished, lacquered and electroplated for decorative and functional purposes. 

Pure Mg is rarely used for structural applications due to its poor mechanical properties. Therefore, A1 and Zn have been introduced as major alloying elements for high-pressure die casting alloys. The main reason... 

BBZ buUc BriUouin zone HPDC high-pressure die casting... 

Lass AbsNii oCui 0 High-pressure die casting (9 mm0 rod) 460 527 67 0noue et al., 1993a)... 

In this section, we report our recent results on the synthesis of Mg-based amorphous alloys in ribbon, bulk and powder forms by various preparation techniques such as melt spinning, metallic mold casting, high-pressure die casting and high-pressure gas atomization, and on their thermal, mechanical and chemical properties. This review also deals with the microstructure and mechanical properties of Mg-based alloys produced by warm consolidation of the atomized powders. 

Fig. 85. Schematic illustration of a high-pressure die casting equipment used for the production of Mg-based bulk amorphous alloys.

Fig. 86. Surface qipearance of amorphous MgtjCujjYio alloys in cylindrical and sheet forms produced by high-pressure die casting.

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