Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1996-10-24
1998-08-11
Ryan, Patrick
Metal founding
Process
Shaping liquid metal against a forming surface
164492, 164494, 164506, B22D 1110
Patent
active
057913994
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATION
This application is a 371 of PCT/DE95/00427 filed Mar. 30, 1995.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method and apparatus for heating molten metal and more particularly, to a method and apparatus for heating molten metal which has been introduced into an ingot mold of a continuous casting installation via an immersion nozzle, especially molten steel covered with a casting powder.
2. Description of the Prior Art
It is known from Japanese Patent Abstract JP-A-61-144 243 to remove solidified slag adhering to the mold wall, e.g., by means of a laser beam.
In the continuous casting of steel, adhesion forces occur between the strand and the ingot mold which can lead to high tensile stresses in the casting shell and accordingly to cracks in the surface of the billet or even to a tearing off of the strand. Therefore, in the continuous casting of steel an oscillating movement is provided between the ingot mold and the strand. In vertical continuous casting, this is generally produced by a sinusoidal up-and-down motion of the ingot mold. This mold movement prevents the newly formed casting shell from sticking to the wall of the ingot mold. Depending on the oscillating speed and casting speed, frictional forces occur between the ingot mold and the casting shell. These frictional forces depend further on the width, length, and conicity or amount of taper of the ingot mold, as well as on the lubrication. In this regard, it has been shown that a lifting platform system at a determined average casting speed causes lower frictional forces than at high or low casting speeds regardless of the dimensions of the ingot mold. It may be concluded from this that the mold lift and the casting lubrication must be optimally adjusted to the casting conditions.
The casting powder located on the melt has an effect on the flow of heat carried off along the ingot mold. The differences in the heat flux caused by the casting aids are most pronounced in the region of the meniscus and decrease toward the ingot mold outlet. It may be concluded from this that the thickness of the casting shell is influenced by the casting aids substantially only in the region of the meniscus.
It has been shown that the heat flux density in an ingot mold increases as the casting speed increases. The heat carried off is at its highest in the meniscus. This is because the liquid steel is in close contact with the wall of the ingot mold and has the highest temperature in this area. With the extensive heat extraction, the casting shell cools off and, in so doing, shrinks and pulls away from the wall of the ingot mold. The type of casting powder and its more heat is carried off from the liquid steel in the ingot mold when the casting powder has a low melting point than with higher-melting casting powder. An even greater increase in the heat carried off was determined when using rapeseed oil as a mold lubricant.
Insufficient dissipation of heat is one cause of breakout in continuous casting. In general, a weakening of the casting shell in the ingot mold precedes breakout; that is, a crack occurs in the casting shell or the slag has prevented the heat from being carried off through the casting shell. Cracks in the casting shell occur, for example, because of suspension during or after the overflow of the ingot mold or during bridging between the immersion nozzle and casting shell.
SUMMARY OF THE INVENTION
Therefore, the object of the present invention is to provide a method and apparatus which ensure a uniform dissipation of heat along the ingot mold and additionally ensure constant frictional forces between the casting shell and ingot mold.
In the present invention, heat energy is introduce d from a heat energy source onto the surface of a metal melt or metal bath in a punctiform or concentrated point-like manner. As used herein, punctiform means that the heat energy is provided as a concentrated or point-like source of energy, as is characteristic of laser energy s
REFERENCES:
patent: 4750947 (1988-06-01), Yoshiwara
patent: 5131941 (1992-07-01), Lemelson
patent: 5314003 (1994-05-01), Mackay
Lin I.-H.
Mannesmann Aktiegesellschaft
Ryan Patrick
LandOfFree
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