Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1996-03-07
1997-05-27
Lin, Kuang Y.
Metal founding
Process
Shaping liquid metal against a forming surface
164502, B22D 1702, B22D 1100
Patent
active
056323247
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
In the continuous casting of steel, molten steel received in a tundish is fed to a continuously casting mold through an immersion nozzle formed in a bottom of the tundish. In this case, the flow rate of molten steel jetted out from a discharge port of the immersion nozzle is considerably large as compared with the casting rate of steel, so that inclusions or bubbles in molten steel are apt to be deeply penetrated into a crater and hence it is not avoided to cause internal defects. Further, there is a problem of remelting solidification shell, while the jet of molten steel in an upstream flowing direction (contrarotating flow or the like) among the jets of molten steel upheaves a meniscus portion in the mold to promote variation of molten steel surface to thereby entrap mold powder thereinto, which has a remarkably bad influence upon the quality of the resulting cast slab and the casting operation.
This invention stably provides cast slabs having improved surface and internal qualities by mitigating variations in the molten steel surface in a mold for continuous casting, entrapment of powder, entrapment of inclusions and the like to improve the internal quality and sounding surface properties when molten steel is cast at a higher throughput exceeding two times of the conventional throughput for molten steel and a higher speed.
BACKGROUND ART
In order to control the flow of molten steel jetted out from the immersion nozzle, it was usual to contrive the shape of the discharge port in the immersion nozzle, or to decrease the pouring rate of molten steel.
However, it was difficult to completely prevent quality defects resulting from inclusion or the like in molten steel by simply changing the shape of the discharge port or decreasing the pouring rate of molten steel.
As a prior art relating to this point, JP-A-57-17356 discloses a method of applying a braking force to the flow of molten steel jetted out from the immersion nozzle by arranging a device for generating a static field in the mold for the continuous casting, and JP-A-2-284750 discloses a technique of applying a braking force to the flow of molten steel jetted out from the immersion nozzle by Lorenz force produced through an interaction between current and magnetic field induced by applying a static field to the entire mold for the continuous casting.
In the technique disclosed in JP-A-57-17356, when the braking force is applied to the jet of molten steel, the flowing direction is changed to disperse the energy inherent to the jet of molten steel as if the jet of molten steel collides with a wall and hence the uniform flow can not be obtained. Further, the jet of molten steel escapes in a direction having no static field, so that the satisfactory result can not be obtained.
In the technique disclosed in JP-A-2-284750, it is possible to attain the uniformization of molten steel jetted out from the immersion nozzle and the variation of molten steel surface on the meniscus portion can be made small, so that the surface and internal qualities of the cast slab can be improved to a certain extent, respectively. However, when the high-speed casting is carried out under a condition that the throughput of molten steel exceeds 2 times of the conventional throughput, there still remaining the following problems. deflected flow in a mold accompanied with the flow of molten steel jetted out from the immersion nozzle can not be avoided. nozzle is caused with the increase of the flow rate of molten steel jetted, the deflected flow in the mold becomes large and hence the continuous casting can not stably be attained. at a short side of the mold becomes high speed accompanied with the increase of the flow rate of molten steel jetted, so that the variation of molten steel surface becomes large and the entrapment of powder can not be avoided. Moreover, the use of single-hole type immersion nozzle can be considered. In the latter case, when the static field is applied to a lower zone of molten steel jetted, the contrarotating upstream of molten steel
REFERENCES:
patent: 3911997 (1975-10-01), Sugazawa et al.
patent: 5265665 (1993-11-01), Fujii et al.
Bessho Nagayasu
Fujii Tetsuya
Idogawa Akira
Nara Seiko
Kawasaki Steel Corporation
Lin Kuang Y.
Miller Austin R.
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