Die casting process selection: In a cold-chamber die casting machine, which category of alloys is typically cast and why?

Introduction / Context:
Die casting machines are categorised as hot-chamber and cold-chamber, and the choice depends on alloy melting temperature and chemical reactivity with the machine’s submerged components. Understanding this selection prevents damage to equipment and ensures consistent casting quality.

Given Data / Assumptions:

• Cold-chamber process ladles molten metal into an unheated shot sleeve.
• Hot-chamber process uses a submerged gooseneck/shot system.
• We consider common non-ferrous alloys used industrially.

Concept / Approach:
Hot-chamber die casting is ideal for low-melting, non-reactive alloys such as zinc and some magnesium grades. Cold-chamber die casting is used for higher-melting or more reactive alloys (e.g., aluminium, brass, some magnesium) because the molten metal is not held within the machine’s immersed components, reducing corrosion and thermal damage risks. Therefore, alloys with relatively high melting temperature are typically cast in cold-chamber machines.

Step-by-Step Solution:
Identify limiting factor: submerged metal exposure in hot-chamber designs.Note material compatibility: aluminium/brass can attack iron components and operate at higher temperatures.Select cold-chamber for higher-temperature melts to protect hardware.Choose “high melting temperature”.

Verification / Alternative check:
Process manuals specify aluminium and brass for cold-chamber die casting; zinc predominantly uses hot-chamber.

Why Other Options Are Wrong:
Low-melting alloys are better suited to hot-chamber equipment.

Ferrous alloys are not die cast by these methods due to extremely high temperatures.

Ceramic slurries and polymers are not metallic die casting feedstocks.

Common Pitfalls:
Assuming “cold” refers to the metal being cold; it refers to the injection system being separate from the melting furnace.

Final Answer:
high melting temperature