中文摘要：

制作直径10mm的试样以模拟铸坯表面组织,将试样分别在传统冷却模式下和控制冷却模式下进行冷却,通过对试样截面的微观组织形貌进行金相分析,从而研究冷却模式对铸坯表层组织结构的影响。试验得到如下结果：传统冷却条件下,试样边部为块状铁素体和珠光体,晶粒尺寸在10～200μm之间,中心位置为条状、针状铁素体和珠光体,晶粒粗大,组织不均。控制冷却条件下,试样均由块状铁素体和珠光体组成,晶粒尺寸在9.36～12.25μm之间,晶粒细小,组织均匀。控制冷却可以通过细化晶粒来提高铸坯表面的高温塑性从而对避免表面横裂纹的发生产生有利影响。

英文摘要：

The samples of diameter 10 mm were made to simulate slab surface.The experiment was made to control the samples cooling at traditional cooling pattern and controlled cooling pattern respectively.Furthermore,the microstructure of transverse section was observed under a metallographic microscope to study the influence on microstructure of slab surface of cooling pattern.The experiment results are as follows： Using traditional cooling pattern,the microstructure is massive ferrite and pearlite by the side of the sample.The grain sizes are between 10-200 μm.Moreover the microstructure is strip ferrite,acicular ferrite and pearlite at the center area,the grain sizes are bigger,and the microstructure is uneven.Under controlled cooling conditions,the microstructure is massive ferrite and pearlite.The grain sizes are between 9.36-12.25 μm and that the grains are small and the microstructure is even.The controlled cooling pattern can promote refinement grains to increase the hot ductility of slab surface,which will have positive effect on avoiding the occurrence of surface transverse cracks.