DIECASTING

 

Zinc has a low melting point (420 degrees C), is strong and, like cast iron, it takes up the detail of the mould extremely well. Diecasting zinc alloys are alloys of high purity zinc with small quantities of added aluminium, copper and magnesium. Traditionally diecastings were solid castings (i.e. not hollow) and were used for precision components, for example automobile carburettors, for decorative items such as automobile door handles and mascots, for children’s toys and for household appliances, precision fittings and tools. However the high weight relative to plastic has tended to result in the replacement of diecastings by plastics for decorative items. The competition of plastics for traditional diecasting applications in the 1970s caused a significant change in the industry, and solid diecastings are now used to a much smaller degree than in the past. Diecastings are now generally cast hollow, as so-called thin-walled diecastings. They are cast in automated machines which can achieve a high productivity, and they can be given a wide range of finishes. Diecastings, even when coated, for example with chromium plate, can be quite easily distinguished from plastic items which arguably feel “cheap and nasty”.

 

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