Multi-pass Drawing & Inter-pass Annealing
多道次拉深与中间退火
标签：再结晶退火, 加工硬化, 减径, 道次规划
紫铜加工硬化快，单次拉深率一般≤40%（即直径缩减≤18%）。多次拉深间需 500–600℃ 保护气氛再结晶退火并酸洗去氧化皮，恢复塑性。黄铜可用连续拉深，但每道后测量壁厚，总断面减缩率累计控制在 70–80% 再退火，否则易在危险断面断裂。
Copper work-hardens rapidly, so a single draw reduction is usually ≤40% (diameter shrink ≤18%). Between passes apply 500–600℃ bright annealing in protective atmosphere and pickle off scale to restore ductility. Brass can be drawn continuously, but measure wall thickness after each pass; keep cumulative area reduction at 70–80% before annealing, or fracture occurs at the critical section. ---