抄録
The mechanism by which cracks are occurred in the immersion nozzle with silicaless inner porous refractory developed to stabilize the injection of argon gas into molten steel, and the prevention of nozzle cracking have been investigated. The results obtained are as follows.
(1) Models for estimating the crack formation pressure and hot argon gas pressure for the immersion nozzle were proposed. Using those models, a theory for preventing nozzle cracking according to casting conditions was worked out.
(2) With the immersion nozzle with silicaless inner porous refractory, the hot argon gas pressure did not drop. Therefore, when the initial argon gas pressure is substantially high, a longitudinal crack tends to occur easily in the powder line which deteriorates in strength due to corrosion in the latter half of casting operation.
(3) By increasing the immersion nozzle wall thickness to improve its strength and controlling the hot argon gas pressure below the crack formation pressure, it is possible to prevent cracks in the immersion nozzle with silicaless inner porous refractory.
