采用Linseie L78 RITA淬火/相变热膨胀仪测定了试验低碳钢的相转变温度,利用金相显微镜(OM)及扫描电镜(SEM)研究了等温处理对试验钢中铁素体形核及形态的影响。结果表明:试验低碳钢Ac3、Ar1和Ar3分别为880、530和750℃。730~600℃等温处理时,随着等温温度的降低,晶内铁素体形貌由多边形转变为针状,同时伴随着轴比的升高,各向异性的增加。随转变温度降低和等温时间延长在夹杂物上形成晶内铁素体,晶内铁素体的形成总是滞后于晶界铁素体的形成。 The phase transition temperature of low carbon steel was measured by Linseie L78 RITA quenching / phase change dilatometer. The effect of isothermal treatment on the nucleation and morphology of ferrite in the test steel was investigated by OM and SEM. The results show that the experimental low-carbon steel Ac3, Ar1 and Ar3 were 880,530 and 750 ℃. With isothermal treatment at 730-600 ℃, the morphology of intragranular ferrite transformed from polygonal to acicular with the decrease of isothermal temperature, accompanied by an increase of axial ratio and anisotropy. The formation of intragranular ferrite on inclusions with the decrease of the transformation temperature and the prolonged isothermal time, the formation of intragranular ferrite always lags behind the formation of grain boundary ferrite.