锻件晶粒度控制：终锻温度是关键变量｜Grain Size Control: Finishing Temperature Is the Key Variable

摘要：晶粒度超标退货，料和变形量都对，问题多半出在终锻温度。讲再结晶窗口、终锻温度与变形量的配合、以及现场怎么把温度握住。
Abstract: When a test report rejects grain size with correct material and deformation, finishing temperature is the usual culprit. The recrystallisation window, matching temperature with deformation, and holding it on the floor.

正文： 理化报告晶粒度不合格，追溯结论常让人意外：材料成分没问题，变形量也够，坏在最后一火的终锻温度高了二十度。晶粒是最后一秒定型的，不是前面几火攒的。
Main text: A grain-size rejection with clean chemistry and adequate deformation usually ends at the last fire: finishing temperature twenty degrees high. Grain size is set in the final seconds, not accumulated over earlier fires.

一、再结晶窗口
1. The recrystallisation window

终锻温度高于再结晶上限，晶粒打碎了又长大，细化收益清零；低于再结晶下限，晶粒碎着留住，残留加工硬化，后续热处理晶粒异常。要的窗口就是：变形足、温度落在再结晶区下沿。
Finish above the recrystallisation ceiling and broken grains regrow, erasing refinement; finish below the floor and grains stay fragmented with residual work hardening, causing anomalies in heat treatment. The target: enough deformation with temperature at the lower edge of the recrystallisation zone.

二、温度与变形量的配合
2. Matching temperature and deformation

• 终锻火次的变形量不低于百分之十五到二十，否则晶粒细化不充分。
  Keep final-fire deformation at 15 to 20 percent minimum, or refinement falls short.
• 大变形量火次放前面，小变形收尾，别把大变形留到最后。
  Big deformation early, small deformation to finish — never the reverse.
• 终锻前空冷降温到目标区间再打最后一锤，比等炉温准。
  Air-cool toward the target band before the last blow — more accurate than waiting on furnace control.

三、现场握温度的办法
3. Holding temperature on the floor

红外测温枪对坯料定点测，终锻前测一次、出模后测一次，数据记进批次卡。三班对比，偏差大的班次单独培训。晶粒度合格率提上来的厂，赢在把终锻温度当成跟尺寸一样的检验项来管。
Spot-check with an infrared gun before the final blow and after ejection; log both to the batch card. Compare across shifts and retrain the outliers. Shops that pass grain size consistently treat finishing temperature like a dimension — checked, not assumed.