锻件冷却及后续热处理工艺｜Post-Forging Cooling and Heat Treatment

摘要：锻后冷却制度决定残余应力大小，不合理冷却会带来变形与开裂。高合金钢、高碳锻件必须堆冷或坑冷缓冷；正火、退火、调质各自解决不同问题，升温保温冷却曲线要按材质执行并留记录。
Abstract: How a forging cools sets its residual stress, and careless cooling produces distortion and cracking. Alloy and high-carbon grades need slow cooling in a pile or pit. Normalising, annealing and quenching-and-tempering each solve a different problem.

正文： 锻件锻打完成之后的冷却不能随意堆放冷却，不合理冷却会产生残余应力，出现变形、开裂。
Main text: A forging cannot simply be left in a heap to cool. Uncontrolled cooling generates residual stress, and that shows up as distortion and cracking.

一、锻后冷却：按材质分档
1. Post-forging cooling, by material

普通碳钢锻件：可以空冷；高合金钢、高碳锻件：严禁快速吹风急冷，可以采用堆冷、坑冷，缓慢释放内应力，防止开裂。
Plain carbon steel can be left to air cool. High-alloy and high-carbon forgings must not be force-cooled with a fan: use pile cooling or pit cooling so internal stress is released slowly and the part does not crack.

管控要点：锻件不能堆叠太厚，堆叠内部散热慢，冷却不均；高风险材质执行缓冷制度。
Two points to control: do not build the pile too deep, because the centre cools far slower than the outside and the mismatch produces its own stress; and apply a written slow-cooling procedure for the high-risk grades.

二、后续热处理：三种制度，解决三个问题
2. Heat treatment: three schedules, three problems

• 正火：细化锻造粗大晶粒，改善组织；
  Normalising. Refines the coarse as-forged grain and improves structure.
• 退火：降低硬度，消除锻造应力，便于后续机加工；
  Annealing. Lowers hardness, relieves forging stress and makes the part machinable.
• 调质（淬火 + 高温回火）：获得高强度 + 韧性，用于承载重要零部件。
  Quenching and high-temperature tempering. Gives the strength-plus-toughness combination needed for load-carrying parts.

工艺关键点：热处理升温曲线、保温时间、冷却介质、冷却速度严格按照材质执行；装炉摆放保证工件受热均匀；做好热处理温度、时间记录。
The heating curve, soak time, quench medium and cooling rate all follow the material specification. Loading must allow uniform heating. Temperature and time are recorded for every load.

风险：淬火冷却过快容易开裂；保温不足组织转变不完全，力学性能达不到要求。
The two risks are symmetrical: quench too fast and the part cracks; soak too short and the transformation does not complete, so the mechanical properties miss the specification.

小结 锻后冷却不等于随便放凉，合金钢要执行缓冷；热处理严格执行升温保温冷却工艺，做好工艺记录。
In short. Post-forging cooling is a process step, not a pause. Alloy steel needs slow cooling, and heat treatment must follow the specified heat-up, soak and cooling with the records to prove it.