For the austempered ductile iron as required by tensile strength ≥1200MPa, elongation after fracture≥1% and energy absorption (sample without notch)≥35J, if its spheroidization rate is lower than level 3, the spheroidal graphite is thicker than level 6 and its amount per mm2 is less than 180, its mechanical performance after isothermal treatment will be difficult to suit the specification requirements.%对于要求抗拉强度≥1200MPa；断后伸长率逸1%；吸收能量（无缺口试样）≥35J的奥-贝球铁，如果其球化率差于3级，球墨粗于6级且每平方毫米球墨少于180个，等温处理后的力学性能不易达到规范要求。
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