中文摘要：

采用光学显微镜、带能谱的扫描电子显微镜等分析技术观察了不同冷速下La脱氧钢的显微组织，并绘制了静态连续冷却转变图．实验结果发现，在4～10℃-s-1的冷速范围内，钢中会有大量晶内铁素体形成，其中在8℃·s-1冷却时可以获得大量细小且弥散分布的晶内针状铁素体．La脱氧钢中含La夹杂物与α-Fe相有较低错配度，其中La2O2S夹杂物与α—Fe相的品格错配度最小为0．2％，钢中含La夹杂物均可诱导晶内针状铁素体形核并可促进感生形核．进而细化组织．

英文摘要：

The microstructures of La deoxidized steels obtained at different cooling rates were investigaled by optical microscopy and scanning electron microscopy coupled to an energy dispersive X-ray spectrometer. The continuous cooling transformation diagram of the tested steel was also drawn in this paper. It is found that in the cooling rate range of 4 to 10 ℃·s -1 , intragranular ferrite can form in the steel. While at the cooling rate of 8 ℃ · s -1, the microstructure mainly consists of fine and dispersed intragranular acicular ferrite （IAF）. The lattice disregistry between lanthanum-containing inclusions and α-Fe is small; especially, this value of La2O2 S is 0. 2%. These kinds of inclusions can induce IAF nucleation and sympathetic nucleation, and also make grains refined.