Pinholes under the slab surface lead to surface defects in steel plate. The pinholes are caused by Ar gas bubbles injected into the submerged entry nozzle to prevent the nozzle clogging. The Ar gas bubbles are likely to be trapped at the solidification front of the meniscus in the mold. It is important for prevention of trapping Ar gas bubbles at the solidification front to control the molten steel flow and to control the heat supply to the meniscus in the mold. In this study, the molten steel flow was controlled by the submerged entry nozzle with an H-type well, without the use of electromagnetic force. The nozzle could prevent the biased flow in the mold, and as a result, the molten steel flow of the meniscus was equalized. To control the heat supply to the meniscus in^the mold, the super heat of molten steel and the casting speed were optimized. Pinholes under the slab surface were decreased by these improvements in the No.4CC-2STRmachine at Kakogawa Works.
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