ABSTRACT

To accurately study the distribution characteristics of impurities and microstructures in the 2800 ppm Bi content 1215 MS steel, the horizontal solidification experiments were carried out by altering horizontal cooling processes. Results show that under moving rates (υ) = 0.3 mm/s and 0.5 mm/s the equivalent diameters of the impurities in steels at the interface between the chilled grain zone and columnar grain zone were higher at 1.6 ~ 1.8 μm, 2 ~ 3 times larger than those in the chilled boundary. Most small-sized inclusions were gathered in circular or linear distribution with the sizes of <1.0 μm. The morphologies of MnS/Bi-MnS inclusions were in rod-like, long strip, spindle, ellipsoidal, and spherical shape. The high υ value was beneficial for increasing the equivalent diameters of the impurities in the chilled grain zone and resulted in the reduction in the inclusions sizes in the columnar grain zone but it seldomly affected their sizes in the equiaxed grain zone. The morphologies of the equiaxed grains were in directional stacking, cross, anisotropy and coniferous pine types.

摘要

为了准确研究铋含量为 2800 ppm 的 1215 MS 钢中杂质和微观结构的分布特征，通过改变水平冷却工艺进行了水平凝固实验。结果表明，在移动速率（υ）=0.3 mm/s和0.5 mm/s下，钢中冷硬晶区与柱状晶区界面处的杂质当量直径较高，分别为1.6~1.8 μm、2~3 μm。比冷冻边界中的要大几倍。大多数小尺寸夹杂物呈圆形或线性分布，粒径<1.0 μm。MnS/Bi-MnS夹杂物的形貌呈棒状、长条状、纺锤状、椭球状和球状。高υ值有利于增加冷晶区杂质的当量直径，导致柱状晶区夹杂物尺寸减小，但很少影响等轴晶区夹杂物尺寸。等轴粒的形态呈定向堆积型、交叉型、各向异性型和针叶松型。