中文摘要：

采用高温实验和光学显微镜、扫描电子显微镜等研究Mg含量对1873 K下Ti-Mg复合脱氧后铸锭样品中夹杂物组成、大小分布以及实验钢中晶内铁素体形核的影响。结果表明：当Mg含量（质量分数）为0.0015%-0.0026%时，实验钢中夹杂物的分布最为细小弥散，晶内铁素体形核效果较好。当奥氏体化温度为1200℃时，钢中晶内铁素体的比例较高，有利于晶内铁素体形核的最佳奥氏体晶粒大小为120μm左右。

英文摘要：

The effects of Mg content on the composition, size distribution of inclusions and microstructure of ingot samples deoxided by Ti-Mg at 1 873 K were investigated by high temperature tests, SEM-EDS and optical microscopy （OM）. The results show that when the Mg content （mass fraction） varies from 0.001 5%to 0.002 6%, the inclusions in experimental steel are fine-distributed, and the effectiveness of intragranular ferrite nucleation is better. At austenitizing temperature of 1 200 ℃, the proportion of intragranular ferrite in steel is higher, and the optimized austenite grain size that is beneficial to intragranular ferrite nucleation is about 120μm.