正火Normalizing 钢材或钢件加热到Ac3（对于亚共析钢）和Accm（对于过共析钢）以上30℃～ It is a processing that heat the steel or parts to Ac3（for hypoeutectoid steel）or Accm (for hypereutectoid steel)+ 正火与xx退火的主要差别在于冷却速度快些。 Higher cooling speed is the main difference between annealing and normalizing.
一般应用于以下方面：Common applications as follow: （1）作为最终热处理，正火可以细化晶粒，使组织均匀化，减少亚共析钢中铁素体含量，使珠光体含量增多并细化，从而提高钢的强度、硬度和韧性。对于普通结构钢零件，机械性能要求不很高时，可以正火作为最终热处理。 (1) As final heat-treatment, normalizing can fine the grains, uniform the organization, reduce the ferrite in hypoeutectoid steel, increase pearlite and also fine the grains, so the strength, hardness and also toughness to be increased. For common structural steel parts with not very high mechanical properties， normalizing can be used as final heat-treatment.
（2）作为预先热处理，对于部分中碳结构钢件，在淬火或调质处理（淬火加高温回火）前常进行正火，以xx魏氏组织和带状组织，并获得细小而均匀的组织。对于过共析钢可减少二次渗碳体量，并使其不形成连续网状，为球化退火作组织准备。 (2)As preheating treatment, for some medium carbon structural steel parts, normalizing is usually be done before quenching or quenching and tempering treatment to remove widmanstaten and lamellar structure and get fine and uniform structure. For hypereutectoid steel, it can reduce the secondary cementite, and to avoid continuous mesh, do organization preparation for diffusion annealing.
（3）改善切削加工性能，低碳钢或低碳合金钢退火后硬度太低，不便于切削加工。正火可提高其硬度，改善其切削加工性能。 (3)Improve the cutting performance, the hardness of low-carbon steel or low carbon alloy steel after annealing is too low and not is good for cutting. Normalizing can increase its hardness and improve the cutting performance.
退火和正火通过作为预先热处理应用，那么在什么情况下选用何种热处理工艺呢？对于低碳和低碳合金钢一定要选用正火，中碳钢在选用正火与退火都可以时，优先选用正火。 Normally annealing and normalizing are used as preheating treatment, so how to choose heat-treatment process and in what case? Low-carbon and low-carbon alloy must use normalizing and both normalizing and annealing are available for medium carbon steel, but normalizing is preferred.
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