亚共析钢中的组织缺陷

Defective Structures in Hypoeutectoid Steel

不同状态的亚共析钢有不同的组织缺陷。例如,正火态亚共析钢中有带状组织、魏氏组织,前者可通过退火加以改善或消除,后者可通过细化晶粒正火、退火或锻造加以改善或消除。调质态亚共析钢中的不良组织有游离铁素体、上贝氏体或托氏体等。对于淬火加热未溶解的铁素体,可通过提高淬火温度或延长保温时间来消除;而对于在淬火过程中析出的铁素体,则可通过提高淬火烈度来消除。分析了共析钢中上述不良组织的形成机制,提出了预防其产生的措施。

Different defective structures are present in hypoeutectoid steel in different conditions. For example, as- normalized hypoeutectoid steel is likely to develop bended structure which may be improved or eliminated by annealing, or widmannstaetten structure which may be improved or eliminated by normalizing of refining grain, annealing or forging; hypoeutectoid steel subjected to quenching and high temperature tempering is likely to exhibit free ferrite, upper bainite or troostite. As far as the free is concerned, the ferrite not solved during heating for hardening may be eliminated by increase in austenitizing temperature or in holding time at temperature; whereas the ferrite precipitating during quenching may be eliminated by increase in quenching severity. Mechanism of producing above-mentioned undesired structures were analyzed, and the some precautions against them were put forward.