常见锻件裂纹、折叠缺陷原因分析｜Cracks and Laps in Forgings: Tracing the Cause
摘要：裂纹、折叠、充型不足、表面凹坑是锻造高频缺陷。折叠来自预锻流线与端面毛刺，裂纹按过热、锻造应力、冷却残余应力分类，排查要按冷却→成型→加热→下料反向追溯。
Abstract: Laps, cracks, short fills and surface pits make up most forging defects. Laps come from preform flow and burrs; cracks divide into overheating, forging stress and cooling stress. Trace backwards: cooling, forming, heating, cutting.
正文： 锻件缺陷很少是单一原因造成的。下面按缺陷类型拆成因，再给一条反向追溯的排查路径。
Main text: A forging defect is rarely down to one cause. What follows breaks each defect type into its origins, then gives a trace-back route through the process.
一、折叠缺陷
1. Laps
表现：锻件表面出现夹缝，属于危害性缺陷，受力会扩展开裂。成因：①预锻型腔不合理，金属流动回流汇合形成折叠；②下料端面毛刺没有清理，锻打压入工件；③润滑积碳，金属流动紊乱。改进：优化预锻型腔引导金属流动；下料清理端面毛刺；定期清理模具型腔积碳。
A lap shows as a seam folded over on the surface. It is a genuine defect: under load the seam opens and becomes a crack. Causes: a preform cavity that lets metal back-flow and rejoin; burrs left on the cut face and pressed into the part; carbon build-up from lubricant disturbing flow. The fixes follow directly: redesign the preform to guide flow, deburr after cutting, and clean carbon out of the cavity on schedule.
二、裂纹缺陷
2. Cracks
分类：加热过热过烧裂纹、锻造应力裂纹、冷却残余应力裂纹。过热过烧裂纹：加热温度太高，晶界损坏，锻打即开裂；控制最高加热温度。锻造裂纹：坯料温度过低变形抗力大；模具圆角太小应力集中。冷却裂纹：合金钢锻件锻后冷却太快，内应力超过材料强度；执行缓冷工艺。
Cracks fall into three groups. Overheat and burning cracks: the grain boundaries are already damaged by excessive temperature, and the part splits on the first blow, so cap the maximum temperature. Forging cracks: the billet is too cold and flow stress too high, or die fillets are too small and concentrate stress. Cooling cracks: the alloy forging cools faster than its strength can bear, so a slow-cooling procedure is required.
三、充型不足与表面凹坑
3. Short fill and surface pits
充型不足（缺料）成因：坯料重量不足；锻造温度低流动性差；打击能量不够；模具排气不良。
Short fill has four causes: underweight billet, low forging temperature giving poor flow, insufficient blow energy, and poor die venting.
表面凹坑：氧化皮压入模具型腔锻打而成；优化去氧化皮工艺，及时清理模腔氧化皮。
Surface pits are scale pressed into the part by the die. Improve the descaling operation and clear scale out of the cavity.
四、排查路径：反向追溯
4. The trace-back route
工艺思路：出现缺陷之后，按照工序反向追溯：冷却→锻打成型→加热→下料，定位根源，调整工艺参数，同时隔离不良批次锻件。
When a defect appears, work backwards through the operations: cooling, forming, heating, cutting. That locates the origin, which tells you which parameter to change. Quarantine the affected batch at the same time.
小结 大部分锻造缺陷不是单一原因，要全流程排查，区分下料、加热、成型、冷却哪一道工序带来缺陷，针对性修改工艺参数。
In short. Most forging defects have more than one contributor. Check the whole chain, identify which operation introduced the defect, and change the parameter that belongs to that operation.
