A fundamental studies on wetting between molten metal and a chill block and crystal growth from the chill block

采用碳钢、Al-Cu二元合金、Al-Si共晶合金和Sn-Sb二元合金，通过浸渍技术形成薄壳。对铸坯的形状和冷侧表面进行了研究，得到了以下结果。(1)龟甲状花纹形成于坯壳激冷侧的表面，对应于坯壳的凹陷区域，在凹陷区域中凝固延迟。(2)在次周波碳钢中形成不均匀的壳。(3)在含碳量低的钢中形成了激冷区，而在含碳量高的钢中形成了细小的枝晶。枝晶由激冷晶和细小枝晶生长而成。在亚周晶碳钢中，基于激冷晶体和细枝晶的混合，延伸的枝晶随机生长，使得凝固不均匀地进行。(4)Al-Cu二元合金和Al-Si合金铸坯冷壳侧表面形成了涟漪痕迹，但与铸坯生长的不均匀性无关。(5)在Sn-Sb二元合金的壳的激冷侧的表面中观察到纽扣痕迹，其对应于Sn-Sb壳的凸起区域。(6)Al-Cu壳层在垂直和水平方向上周期性地发生不均匀生长，而Al-Si壳层只在水平方向上发生不均匀生长。(7)在计算机模拟过程中，应考虑热阻的影响，使凝固坯壳的生长不均匀，从以上结果来看，坯壳的形成有两种类型。一种是它直接取决于成核，例如Sn-Sb合金。另一种观点认为，这取决于形核、相变潜热和热应力引起的固体变形之间的相互关系。

Using carbon steels, Al-Cu binary alloys, an Al-Si eutectic alloy, and a Sn-Sb binary alloy, a thin shell was formed by a dipping technique. The shape of the shell and the surface in the chill side of the shell were investigated.Following results were obtained from experimental results.(1) The pattern like a tortoise shell was formed in the surface of the chill side of the shell and corresponds to the concave region of the shell, in which solidification retarded. (2) An uneven shell was formed in a hypoperitectic carbon steel. (3) A chill zone was formed in the steel containing low carbon content and fine dendrites were formed in the steel containing high carbon content. Extended dendrites grew from the chill crystals and the fine dendrites. In a hypoperitectic carbon steel, the extended dendrites grew randomly based on the mixing of the chill crystals and the fine dendrites, so that solidification proceeded unevenly. (4) Ripple marks was formed in the surface of the chill side of the shell in Al-Cu binary alloys and an Al-Si alloy, but it weren't depend on the uneven growth of the shell. (5) Button marks were observed in the surface of the chill side of the shell in a Sn-Sb binary alloy and it corresponded to the convex region of the Sn-Sb shell. (6) An uneven growth occurred periodically in vertical and horizontal directions of the Al-Cu shell, but it was occurred only a horizontal direction of the Al-Si shell. (7) Heat resistance should be introduced to computer simulation in order to cause the uneven growth of the solidifying shell.Considering from above results, there are two types of the shell fromation. One is that it depends directly on nucleation such as a Sn-Sb alloy. The other is that it depends on the correlation among nucleation, latent heat and solid deformation due to thermal stress.