2000 Fiscal Year Final Research Report Summary
Removal of inclusion through fine bubble and bubble-curtain by imparting swirling flow in immersion nozzle
| Project/Area Number |
10650737
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | Nippon Institute of Technology |
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Principal Investigator |
YOKOYA Shinichiro Nippon Institute of Technology, Mech.Eng., Prof., 工学部, 教授 (80049692)
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| Co-Investigator(Kenkyū-buntansha) |
IGUCH Manabu Hokkaido University, Materials Science and Eng.Prof., 大学院・工学研究科, 教授 (00043993)
TAKAGI Shigeo Nippon Institute of Technology, Mech.Eng., Asso.Prof., 工学部, 助教授 (30265368)
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| Project Period (FY) |
1998 – 2000
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| Keywords | Swirling flow / Immersion nozzle / Fine bubble / Slab mold / Meniscus flow / Centrifugal force / bubble curtain / Inclusion |
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| Research Abstract |
Both with water model experiment and numerical analysis, following swirling effect in the immersion nozzle are cleared as follows :
Uniform velocity distribution can be obtained within a very short distance from the outlet of the nozzle and remarkable stable bulk mold flow can be easily obtained.
Therefore, a decrease in the meniscus flow velocity, remarkable decrease in the amplitude of oscillation, disappearance of vortex and suppression of disturbance, i.e., considerably stable meniscus flow could be observed. Those phenomena contribute to prevent powder from being involved into the mold flow. With an increase in the centrifugal force induced by imparting a swirling motion in the liquid, fine bubbles were accelerated to produce, and obtained bubble sizes were from 1.5 to 6 mm in diameter, i.e., critical diameters of the bubbles were in a range of 1.5 to 2.5 mm. The penetrated volume efficiency of the bubbles increases with increasing the tangential velocity and injected air flow rate. The diameter of bubbles decreases with increasing the tangential velocity. Injection pressure for penetration of bubbles in the metal bath is much lower than that of conventional injection process by tuyeres and lances.
A bubble curtain (namely, bubble accumulated zone) can be established from the wall to the central area of the submerged entry nozzle by imposing a swirling flow pattern in the nozzle and injecting gas bubbles from all around the wall of the submerged entry nozzle. The trajectory of an inclusion is spiral in shape, but its displacement in the radial direction is very little compared that of Ar bubble. Therefore, it may be sure for the inclusion to penetrate through the bubble curtain (namely, bubble accumulated zone) to be trapped by the bubbles and be removed together with the bubbles from the molten steel.
It has been developed a twist-tape-swirling-blade as a cheap, simple and safe swirling generator, from above-mentioned issues.
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