A specific shape formed by forcing metal through a die; also used as a means of coating electrodes. Extrusion is used extensively in the manufacture of various lead, aluminum, magnesium, and brass shapes.
The metal to be extruded is heated to a plastic temperature, then placed in a closed chamber fitted with a die of the desired shape at one end and a piston at the other. It is then forced by hydraulic pressure through the die to produce the specific shape. Perfectly round or intricately shaped forms can be extruded.
Lead can be satisfactorily extruded as pipe or cable sheaths at 204°C (400’F); brass must be heated to about 816°C (1500°F). In general, the lower the melting point of the metal, the easier it will extrude at a given temperature. It should be noted that extrusion is a process of solid flow and not of a plastic mass, such as molten solder. See ELECTRODE MANUFACTURE.