Brass is a binary copper-zinc alloy, also known as ordinary brass, and can be divided into single brass and two-phase brass according to the organization. Single brass is also called α brass, with a Cu content between 62.4%-100% (wt). Two-phase brass (α+β) brass, Cu content between 56.6%-62.4% (wt), the solid solubility of Zn in Cu increases with decreasing temperature. Except for aluminum-containing brass, brass generally has no heat treatment strengthening effect. Therefore, annealing is often used to improve its cold working (stamping, drawing, machining) performance. The mechanical properties and cold deformation properties of annealed brass semi-finished products mainly depend on the grain size. The general rule is that the grain size is small and the hardness is high. In addition, the amount of cold deformation is large and the hardness is high (cold work hardening); the annealing temperature is low and the hardness is high.
Annealing after cold deformation, at the same temperature, the hardness is low when the time is long; at the same time, the hardness is low when the temperature is high.
Brass with low zinc content has little cold work hardening effect, and its grains need to be refined to obtain higher hardness.
Brass containing Zn greater than 20% (wt) has residual stress after cold deformation. In humid atmosphere (especially atmosphere containing ammonia and ammonium salt), mercury and mercury salt solvents, it is easy to cause stress corrosion and cause cracking, which must be Perform stress relief annealing.
The intermediate annealing temperature (℃) during the cold working of brass generally needs to be appropriately reduced as the effective size (mm) decreases.