连续定向凝固技术研究

STUDY OF CONTINUOUS UNIDIRECTIONAL SOLIDIFICATION

在自行设计的竖直热型连铸机上,进行了连续定向凝固实验和温度测定,对其中传热和凝固过程进行了数值模拟,考察了主要工艺参数对锡铸锭表面质量和内部组织的影响,以及固液界面形状的变化规律.结果表明:型温、拉速、冷却水量等工艺参数主要是通过影响固液界面的位置、形状来影响铸锭表面和内部质量的,在本实验条件下,型温在244～248℃、拉速在1.25～2.20×10-4m/s、冷却水量在252～377L/m2·s之间时,才能获得表面光亮,内部为完整定向凝固组织的铸坯;当铸型温度高于242℃,拉速在1.25×10-4～3.4×10-4m/s之间时,形成较平的固液界面,得到定向凝固的铸锭组织;获得了固液界面形状与主要工艺参数间的关系式.

Experiments about the continuous unidirectional solidification of pure tin and temperature measures were completed in the self-made continuous casting equipment with upright heating mould, The heat transfer and solidification processes were mathematically modeled. The effect of various process parameters on the surface quality and microstructure were investigated, the variation rules about the shape of solid-liquid in terface were studied, Experiment results showed that various technology parameters affected the surface and inner quality of pure tin ingot through affecting the position and shape of solid-liquid interface in the mould. Only when the mould temperature was between 244-248℃ , the casting speed was between 1,25×10^-4-2.20×10^-4 m/s and cooling capability was between 252-377L/ m^2·s , could the ingot with mirror smooth surface and integrity unidirectional solidification microstructure be obtained. When the mould temperature was higher than 242℃ and the casting speed was between 1.25×10^-4-3.4×10^-4 m/s, it would form a level solid liquid interface and gain unidirectional solidification structure. A linear equation about the shape and position of the solid liquid interface with main technology parameters was gained.