The source of longitudinal mid-face cracks was investigated and found to be the local retardation o solidification at the early stages.
The crack occurrence tendency was very sensitive to the size of surface groove at the meniscus of mould, the property of mould flux and steel composition. This local retardation of solidification did not diminish during travelling in the mould.
It was possible to evaluate casting conditions by estimating the uniformity of solidified shell thickness and surface temperature by the temperature measurement of copper mould.
