| 摘要 |
PROBLEM TO BE SOLVED: To execute a continuous casting at a desired value of molten steel pouring velocity by calculating a momentum index of rising stream of the molten steel with a specific equation, finding flowing velocity of the molten steel just below the molten steel surface in a mold with the momentum index and deciding the magnetic flux density impressed to the molten steel based on a specific equation. SOLUTION: The molten steel is poured into the mold 1 from an immersion nozzle 2. The momentum index F is obtd. by the equation (1). Wherein,ρis density of the molten steel, Q is flow quantity of the molten steel, V is velocity at which spouting stream of the molten steel collids to a short side of the mold,θis an angle at which the spouting stream collided to the short side 1a, and D is a distance from the collided position of the short side 1a to the molten steel surface. The flowing velocity of the molten steel is found from the pre-measured relational figure showing the relation between the flowing velocity of the molten steel just below the molten steel surface at the 1/4 width position and the F value. The magnetic flux density impressed to the molten steel in the mold 1 is decided based on the equation (2). Wherein, Rv is ratio of the flow quantities of the molten steel at the time of impressing the magnetic flux and at the time of impressing no magnetic flux,βis coefficient,βis magnetic flux density (tesla), and U0 is line velocity of the molten steel spouting from a spouting hole of the nozzle (m/sec). The magnetic flux density is controlled so that the flow velocity of the molten steel just below the molten steel surface becomes the desired value. A slab excellent in the quality can continuously be cast.
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