Function of Solidification Pressure on the Rising and Breakup of Nitrogen Bubbles in Molten Steel

In this study, the rising and breakup of nitrogen bubbles in high nitrogen molten steel considering different solidification pressure has been numerically simulated by the VOF model verified comparing velocity and deformation of bubbles in water. Rising process of nitrogen bubble in the molten steel is divided into three stages. In stage I, nitrogen bubble experiences an inward depression and splits into a main bubble and two daughter bubbles. In stage II, the main bubble deforms slightly, and a few discrete bubbles split from both sides of the main bubble. In stage III, the main bubble rises to the surface of molten steel, and a large number of discrete bubbles split from the main bubble. As the solidification pressure increases from 0.1 to 2 MPa, the area of main and daughter bubbles decreases. Moreover, the jet becomes stronger with the solidification pressure, which makes the daughter bubbles more prone to splitting out. The total rising time and the maximum rising velocity of the main nitrogen bubble decrease with increasing solidification pressure. This decrement weakens the disturbance of the bubbles rising on the high nitrogen molten steel in stage III, leading to a decrease in the number of discrete bubbles.