Analysis of processing performance of purple copper plate

1, the room temperature structure of copper plate: ordinary brass is a binary alloy of copper and zinc, the zinc content varies widely, so the room temperature structure is also very different. There are three kinds of microstructure of brass at room temperature: brass with zinc content below 35%, the microstructure at room temperature is composed of single-phase α solid solution, called α brass; The microstructure of brass with 36% ~ 46% zinc content is composed of (α+β) two-phase at room temperature, called (α+β) brass (two-phase brass). The microstructure of brass containing more than 46% ~ 50% zinc at room temperature consists only of β phase, called β brass.

2, pressure processing performance: α single-phase brass strip (from H96 to H65) has good plasticity, can withstand hot and cold processing, but α single-phase brass in forging and other hot processing is prone to brittle temperature, its specific temperature range varies with the amount of Zn, generally between 200 ~ 700℃. Therefore, the temperature of hot processing should be higher than 700℃. The main reason for the brittleness zone of single-phase α brass is the existence of ordered compounds in the α phase of Cu-Zn alloy system. The ordered transformation occurs when the alloy is heated at low temperature, which makes the alloy become brittle. In addition, there are trace harmful impurities of lead and bismuth in the alloy and copper to form eutectic films with low melting point, which distribute on the grain boundary and produce intergranular rupture during hot processing. Practice shows that adding trace amount of cerium can effectively eliminate the temperature brittleness of medium copper plate. The β brass containing more than 46% ~ 50% zinc cannot be processed by pressure because of its hard and brittle properties.

3, mechanical properties: due to the different zinc content of copper plate, mechanical properties are not the same. For α brass, the mechanical properties increase with the increase of zinc content. For (α+β) brass, the strength at room temperature increases when the zinc content is increased to about 45%. If the zinc content of the copper plate is further increased, the strength of the alloy decreases sharply due to the appearance of a more brittle R phase (solid solution based on Cu5Zn8 compound) in the alloy structure. The ductility of (α+β) brass decreases with increasing zinc content. Therefore, copper-zinc alloys containing more than 45% zinc have no practical value.