WORKSHOP METAL WORKING

摘要

The ductility of most metals and alloys is one of their most useful characteristics, enabling many operations to be performed that would otherwise be impossible. For without stretch and flow in metals there would be no simple operations like riveting and bending, nor manufacturing processes such as rolling, wiredrawing, forging or panel-beating. Equally, however, there are occasions when it is undesirable for metals to change their shape, if no more than because subsequent rectification will be necessary; and with recognition of such cases a considerable amount of trouble and wasted effort may be avoided. Common processes where pressure is (inadvertently) put on the metal are shearing and chiselling. Thus, in cutting a strip from a piece of sheet, as at A, using shears, there is always a tendency for the strip to bend, because of the wedging action of the blades B (left). This is in addition to the curling which occurs.