Abstract: Taking the deep processing properties of 430 ferritic stainless steel as the background， the influence mechanism of rare earth Ce on the equiaxed crystal ratio of 430 ferritic stainless steel was studied. By studying the relationship between the number density， size of rare earth inclusions and equiaxed crystal ratio， the mechanism of the increase of the equiaxed crystal ratio by the rare earth Ce is obtained. The results show that with the increase of Ce content from 0% to 0.039%， the number density of Ce-containing inclusions increases from 0 per/mm2 to 194.37 per/mm2， the equiaxed crystal ratio increased from 28.3% to 84.4%， and the corresponding equiaxed grain size decreased from 1 910 μm to 310 μm. Based on thermodynamic calculations， with the increase of Ce content， SiO2 inclusions are gradually modified to Ce-O， and the heterogeneous nucleation of Ce inclusions on ferrite is the main reason for the increase in equiaxed grain rate of 430 ferritic stainless steel. The CAFE calculation model of PROCAST also indicates that as the number density of nucleating agent particles increases， the equiaxed grain rate gradually increases， and the theoretical calculation results are basically consistent with the actual observation results.

Key words: Elemental Ce, 430 Ferrite Stainless Steel, Equiaxed Crystal Ratio, Heterogeneous Nucleation

摘要： 以430铁素体不锈钢的深加工性能为背景，研究了稀土Ce对430铁素体不锈钢等轴晶率的影响机理。通过研究稀土夹杂物的位置、数量密度、尺寸与等轴晶率之间的关系，得出了稀土Ce对于430铁素体不锈钢等轴晶率的影响机理。结果表明：随着Ce含量从0%增加到0.039%，含Ce夹杂物的数量密度0个/mm2增加到194.37个/mm2，各试样中含Ce夹杂物的尺寸85%以上在1~2 μm之间，等轴晶率从28.3%增加到84.4%，相应的等轴晶尺寸从1 910 μm降低到310 μm。结合热力学计算结果，随着Ce含量的增加，SiO2夹杂物逐渐被改质为Ce-O，含Ce夹杂物对于铁素体的异质形核作用是导致430铁素体不锈钢等轴晶率提高的主要原因。PROCAST的CAFE计算模型也表明，随着形核剂粒子数量密度的增加，等轴晶率逐渐增加，理论计算结果和实际观察结果基本相吻合。

关键词: 稀土Ce, 430铁素体不锈钢, 等轴晶率, 异质形核