Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1996-09-16
1998-07-07
Hail, III, Joseph J.
Metal founding
Process
Shaping liquid metal against a forming surface
164479, 164481, 164489, B22D 1100
Patent
active
057754047
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
This application is a 371 of PCT/JP96/00281 filed Feb. 9 1996 published as WO96/24452 Aug. 15, 1996.
1. Technical Field
This invention relates to a method of continuously casting austenitic stainless steel, and more particularly to a continuously casting method simultaneously establishing prevention of surface defects and high-speed casting.
2. Background Art
In stainless steel sheets, it is strongly demanded to more beautify the sheet surface as compared with the other general-purpose steel sheets from a viewpoint of their applications, so that the reduction of surface defects should simultaneously be attained even in the continuous casting of stainless steel. As the conventional technique for reducing surface defects of austenitic stainless steel sheets, there are well-known a method of controlling a cooling rate over a region ranging from a solids temperature of a surface solidification layer portion up to at least 1200.degree. C. to attain the formation of fine austenite grains as disclosed in JP-A-63-192537, and a method of controlling molten steel components and super heating degree of molten steel to attain the formation of fine austenite grains as disclosed in JP-A-3-42150.
Recently, the demand for product quality becomes increasingly strict. For this end, there is proposed the individual control of cooling rate, superheating degree of molten steel and the like, but it can not be said that such a mere control is sufficient because the surface defects are still created.
On the other hand, it is recently demanded to increase the casting speed even in the continuous casting method from a viewpoint of the improvement of productivity. However, when the casting speed is increased, there is a tendency that the surface defects are apt to be superfluously created. Therefore, if it is intended to increase the casting speed until now, it can not be increased considering the surface quality, and hence it is attempted to select the casting speed to a low level within a sufficient range without making an adequate standard and the improvement of the productivity could not be attained.
DISCLOSURE OF INVENTION
It is, therefore, an object of the invention to favorably solve the aforementioned problems in the continuous casting of austenitic stainless steel and to provide a continuous casting method of austenitic stainless steel capable of simultaneously attaining high productivity and excellent surface quality of steel sheet.
The essential points and construction of the invention are as follows:
A method of continuously casting austenitic stainless steel by pouring melt of austenitic stainless steel from a tundish through an immersion nozzle into a continuously casting mold of a continuous slab caster, solidifying it in the mold and continually drawing the resulting slab of given size out from the mold, characterized in that a high-speed continuous casting is carried out so as to satisfy a relation of casting speed, superheating degree of molten steel in the tundish, sectional area of discharge port in the immersion nozzle and slab width represented by the following equation: .multidot..DELTA.T.multidot.d.sup.-0.96 .ltoreq.0.85
The invention is particularly adaptable when the casting speed V is not less than 1.2 m/min.
Furthermore, according to the invention, when the continuous slab caster is a vertical-type twin belt caster or a block caster for the continuous production of thin slab, the high-speed continuous casting is carried out so as to satisfy a relation represented by the following equation: .multidot.d.sup.-0.96 .ltoreq.1.40
Moreover, the casting speed V of not less than 3.0 m/min is particularly advantageous when the continuous slab caster is the vertical-type twin belt caster or block caster for the continuous production of thin slab.
As the immersion nozzle according to the invention, a multi-hole nozzle is particularly favorable. In case of the multi-hole nozzle, the sectional area of nozzle discharge port means a total sectional area of nozzle openings facing
REFERENCES:
patent: 4883544 (1989-11-01), Ueda et al.
Bessho Nagayasu
Itoyama Seiji
Miki Yuji
Nomura Hiroshi
Yamada Sumio
Hail III Joseph J.
Kawasaki Steel Corporation
Lin I.-H.
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