2007 Volume 93 Issue 9 Pages 575-582
We have proposed a technology of swirling flow formation in submerged entry nozzles as a fundamental and effective measure for controlling flow pattern in continuous casting molds. A joint study started in 1997 between Nippon Institute of Technology, Osaka University, Kyushu Refractories and Sumitomo Metal Industries to develop swirling flow submerged entry nozzles with a swirling blade for steel casting. As a first step, we have developed a swirling flow submerged entry nozzle for round billet casting in Wakayama works.
Generally, single port submerged entry nozzles are applied for round billet casting with small section molds. Outlet flow from the single port intrudes deeply in strands, which causes lack of equiaxed crystals at the center part of billets and low temperature of molten steel surface in the mold. Low temperature of molten steel surface in the mold induces solidified deckle and retard melting of mold fluxes. As a countermeasure of these problems, M-EMS (Electromagnetic stirring in mold) is widely applied for round billet casters.
The basic effect of the swirling flow in the single port submerged entry nozzle for the round billet casting was evaluated by a wood metal experiment, then we applied the swirling flow submerged entry nozzle for the round billet casting. As a result of steel casting in Wakayama, we confirmed same phenomena as the wood metal experiment as follows;
(1) The surface temperature of molten steel in the mold rose in the case that the swirling flow in the nozzle and the M-EMS were combined in the opposite direction of rotations by appropriate balance of intensity.
(2) The surface temperature of molten steel in the mold also rose in the case without the M-EMS.
(3) The surface temperature of molten steel in the mold was thought to rise as a result of the upward flow formation along the mold wall.