Brass Manufacturing Processes
Good hot and cold formability
Notes:
Brass components can be produced by a wide variety of techniques. Besides the effects of composition, processing history will have a significant effect on properties.
Hot working is commonly carried out either by hot rolling of cakes or slabs or by extrusion or forging of billets. The basic effect of hot working on the brasses is to break up the original cast structure which improves physical properties and modifies directionality. The properties will then correspond to the annealed (O) state. If, however, the final working temperature is below that needed for full recrystallisation, then some cold working occurs. Material in the "as manufactured" (M) condition is therefore generally stronger than in the annealed (O) condition.
The strength of most of the commercially available brasses cannot be improved by heat treatment. Any improvement in properties over the soft, annealed condition is obtained by cold working. In the case of extruded products such as rods, bars, sections, tubes and wire, the cold reduction is applied by drawing through dies, while in the case of sheet and strip it is applied by cold rolling.
Progressive amounts of cold working increase the tensile strength, proof strength and hardness of the alloy, with a consequent reduction in ductility, as measured by elongation. Material available from manufacturers has been subjected to various amounts of cold reduction; temper grades covered by British Standards for sheet, strip and wire are 1/4 hard, 1/2 hard, hard, extra hard, spring hard and extra spring hard. Not all brasses or forms are available in all temper conditions. Hard rolled brasses have better ductility longitudinally in line with the rolling direction rather than in the transverse direction. Advantage of this can be taken when designing springs or other flexible parts.
The temper grade specified when ordering material must be based on the degree of forming necessary to produce the finished component. With experience, alpha brasses can be temper-annealed within a wide variety of combinations of properties such as hardness and grain-size suitable for differing end-uses.