Anneal, Annealing. A heating and subsequent cooling of metal to soften it for further working. It requires the metal to be heated until is glows, then allowing it to slowly cool. The process recrystallizes the molecular structure. Such HEAT TREATMENT induces ductility, relieves internal stress, refines the internal metal structure, and improves its metalworking properties. It is often used prior to some cutting, forming or shaping process, and often used after the metal object has become WORK HARDENED

where some further work must be performed. Specifically:

∙ Die blanks are annealed prior to engraving (by hand or machine cutting).

∙ Dies blanks are annealed prior to hubbing, afterwards they are hardened by tempering.

∙ Strips of metal after being reduced in thickness in a ROLLING MILL are annealed, often after each pass through the rolling mill until the strips are proper thickness for BLANKING.

∙ Planchets for coining are annealed after blanking to ease the wear and stress on the dies during striking.

∙ Partially struck medals are often annealed for subsequent striking of high relief medals in a repeated process of striking and annealing.

The properties of iron and steel make them ideal to anneal and temper (soften and harden) to control the hardness of the metal as desired. This is the primary reason dies are made of ferrous metal. Coinage metals – copper and its alloys, silver and gold – can also be annealed but the need for annealing of precious metals is less than that for bronze as for striking high relief multiple-struck medals.

Tin, lead, white metal, pewter, Britannia metal and similar alloys cannot be annealed because they are so soft, but there is little need to because their design is so easy to strike up in a single blow, and die wear is minimal.

References:

C66 {1988} Cooper p 94, 106-7, 183-4.