Root-cause Tree: Folds, Burning & Contamination Cracks
锻件开裂根因树：折叠、过烧与污染脆裂
标签：开裂, 折叠, 过烧, 根因分析
铜锻件开裂按形貌分四支：折叠——线状、底部圆滑、两侧带氧化皮，源自上道锤击重叠，磨除后可继续；热裂——断口呈亮晶状，多因终锻温度以下仍继续锻打；过烧——黄铜超过约 950℃ 晶界熔化，断口粗糙无光泽，整件报废；污染脆裂——含硫润滑油或铅混入使紫铜沿晶界热锻开裂。诊断流程：低倍浸蚀看流线→断口宏观判读→必要时金相验证。预防靠温度铭牌上墙、炉料分区管理与工具专用，含硫油品严禁用于铜件润滑。
Sort copper forging cracks by appearance into four branches: folds — linear with rounded roots and oxide on both faces from the previous blow overlapping; grind out and continue. Hot cracks — bright crystalline faces when hammering continues below finishing temperature. Burning — brass past about 950°C melts grain boundaries, leaving dull rough fractures and a write-off. Contamination cracking — sulfurized lubricant or lead pick-up splits pure copper along grain boundaries during hot work. Diagnose by macroetch for flow lines, fracture reading, metallography if needed; prevention is posted temperature cards, segregated stock and sulfur-free lubricants.