由于恰好高于低临界温度通常使过共析钢奥氏体化而硬化，所以对外层采用较低的热处理温度。

The lower heat-treating temperature of the case results from the fact that hypereutectoid steels are normally austenitized for hardening just above the lower critical point.

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因此，选育不育临界温度低、育性相对稳定的实用光温敏核不育系，探讨不育系育性转换规律、育性遗传规律及生理生化特性，在理论和实践上都具有重要意义。

So it is very important for the theory and practice to research and insight the fertility alteration, fertility inheritance and physiological and biochemical characters of PTGMS lines.

youdao

因此，选育不育临界温度低、育性相对稳定的实用光温敏核不育系，探讨不育系育性转换规律、育性遗传规律及生理生化特性，在理论和实践上都具有重要意义。

So it is very important for the theory and practice to research and insight the fertility alteration, fertility inheritance and physiological and biochemical characters of PTGMS lines.

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