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利用光学显微镜检测了抗拉强度超过标准上限的低碳钢的金相组织,试样中伪珠光体体积分数达到50%以上,明显高于正常组织中的珠光体体积分数,因此具有显著的珠光体强化效果;并且伪珠光体存在明显的退化现象。对比分析生产工艺后认为,层流冷却过程中对先共析铁素体析出的抑制以及终冷温度低于空冷的Ar1是产生这种退化显著的伪珠光体组织的必要条件。结合生产实践分析了影响先共析铁素体析出的因素。
The microstructure of low-carbon steel with the tensile strength exceeding the upper limit of the standard was examined by optical microscope. The volume fraction of the pseudo-pearlite in the sample was above 50%, which was significantly higher than the volume fraction of the pearlite in the normal tissue. Therefore, Body strengthening effect; and pearlite obvious degeneration phenomenon. After comparing the production process, it is considered that the inhibition of pro-eutectoid ferrite precipitation and Ar1 with the final cooling temperature lower than air-cooling in the laminar cooling process are the necessary conditions for producing this degenerated pearlite microstructure. According to the production practice, the factors affecting the precipitation of proeutectoid ferrite are analyzed.