Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1992-01-30
1993-11-23
Rosenbaum, Mark
Metal founding
Process
Shaping liquid metal against a forming surface
164 551, 164 561, 75305, B22D 1110
Patent
active
052635341
DESCRIPTION:
BRIEF SUMMARY
FIELD OF TECHNOLOGY
The present invention relates to an exothermic type mold additive for continuous casting in which exothermic properties are imparted to the mold additive for continuous casting of steel. Further, the present invention relates to an exothermic type mold additive for continuous casting of steel, specifically to a mold additive which is able to reduce carburization in a product cast piece and further to reduce surface defects of the product such as inclusions, pinholes, etc.
BACKGROUND OF THE INVENTION
Mold additives for continuos casting of steel are added onto the surface of molten steel poured into a mold to form by receiving heat from the molten steel a layer structure above the molten steel surface, of a fused slag layer, a sintered layer and an unfused original mold additive layer, and then be consumed while gradually performing various duties. Its main role may be exemplified by the provision of:
(1) a lubricating action between the mold and a solidified shell;
(2) a melting and absorbing action of inclusions which float from inside of the molten steel; and
(3) a heat insulating action of the molten steel and the like are exemplified.
Recently, progress in continuous casting technology of steel has been remarkable and the demands on mold additives which have an influence on cast-piece qualities and operation stabilities have become even more strict, so that the quality of mold additives have been designed to accomodate various steel components and casting conditions.
Among the roles of mold additives (1) and (2) described above, are most important in controlling the characteristics of the mold additive such as softening point, viscosity, etc., so that selection of the chemical composition is important.
On the other hand, for heat insulation of the molten steel of (3), melting speed which is controlled by carbonaceous raw materials and powder characteristics such as bulk density, spreadability, etc. are important.
Even more recently, an exothermic type front mold additive in which molten steel temperatures at a meniscus portion in the mold are secured by improving (3) a step further and in order to improve the quality of castings, metal exothermic materials such as Ca-Si, Al, etc. are included in the mold additive to supply heat to the molten steel by generating exothermic reactions from oxidation in the mold, and then promptly fusing after the reaction to show the same behavior as a normal mold additive after fusing, has become desirable. Further, an exothermic type mold additive for the main has also been desired. Here, front mold additive means a mold additive which is used during irregular casting (at the beginning of casting, during tundish exchange) and main mold additive means a mold additive which is used during regular casting.
However, as it is necessary for an exothermic mold additive not only to obtain heat by exothermic reactions, but also to achieve the original duties of a mold additive after exothermic reactions as described above, various problems in quality design still remain.
When quality designing for a practical exothermic type mold additive for continuous casting, it is necessary to satisfy each of the following 3 items:
(i) that active additives not be contained in consideration of safety at the time of production, storage and use;
(ii) that exothermic reactions which can supply sufficient calorific value be obtained rapidly and uniformly without leaving unreacted substances, and that the calorific value, flame generating amounts, etc. can be controlled according to casting conditions when used; and
(iii) that exothermic reaction products rapidly form a fused glass layer, and be consumed by succesively flowing in between a mold and a solidified shell.
Up to now various exothermic mold additives have been proposed, however, there is no mold additive which satisfies the 3 items described above.
For instance, in Japanese Patent Laid Open No. 48-97735 a mold additive in which silicon, ferrosilicon and calcium-silicon are added as exothermic substances has been
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Fujiwara Hideaki
Hattori Shinji
Ichikawa Kenji
Morita Akihiro
Nomura Osamu
Puknys Erik R.
Rosenbaum Mark
Shinagawa Refractories Co. Ltd.
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