Metal founding – Means to shape metallic material – Pressure shaping means
Patent
1996-08-07
1998-09-01
Hail, III, Joseph J.
Metal founding
Means to shape metallic material
Pressure shaping means
164513, B22D 1706, B22D 2702
Patent
active
057997187
DESCRIPTION:
BRIEF SUMMARY
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a 371 of PCT/FR95/00112 filed Feb. 1 1995.
BACKGROUND OF THE INVENTION
The present invention concerns the preheating of a metal casting spout of the type comprising over its length an open hollow refractory element having a closed transverse section and enclosed by an insulating covering, which is in turn enclosed by an inductor enclosed in refractory concrete held in a casing.
Commonly assigned French Patent Application No. 93 01 497 describes a spout of the type mentioned above. Metal-transfer heating spouts prove especially advantageous for the transmission of a metal heated to high casting temperature, in particular for low-pressure bottom casting.
When casting operations are of a discontinuous nature, the liquid metal cannot remain for a relatively long period in the spout. Advantage is gained, in this case, by keeping the metal constantly preheated during this period.
In conventional systems such as that described in commonly assigned U.S. Pat. No. 4,475,721 to Pamart, preheating is accomplished using a graphite susceptor sleeve comprising a straight and a bent part, which causes a number of operating difficulties arising from the complexity of manufacture of the spout: i.e., problems linked to forming, cutting, and centering. These problems increase the cost of manufacture of the spout.
To solve these problems, a liquid metal-transmission heating device has been used. This device, which has a closed transverse section, extends upward and ends, on its upper face, in a casting orifice in order to feed at least one mold, and it incorporates, over its entire length, at least one heating element consisting of a coil-shaped inductor through whose cooled turns runs an alternating electric current.
Heating and maintenance of the liquid metal held in the refractory spout are effected by the inductor, through which runs a medium- or high-frequency alternating current. This heating method allows direct transfer to the liquid metal of electrical energy in the form of thermal energy. Because it does not make use of an intermediate element such as graphite, energy transfer is direct and efficiency is higher. The frequency running through the inductor typically falls within the range of 1,000-15,000 Hertz.
This device no longer ensures the internal preheating thereof, either before a casting run or between two successive casting operations.
The aforementioned Patent Application No. 93 01 497 proposes a method of preheating utilizing secondary means, e.g., an element using gas. However, this preheating device cannot be used for long, small-diameter spouts, such as those measuring one meter in length and having a diameter of less than ten centimeters. Furthermore, gas heating is not generally very precise.
SUMMARY OF THE INVENTION
This invention is intended to solve these problems. To this end, the preheating element according to the invention comprises the inductor of the casting spout and an element comprising a refractory material and an electrical conductor, in order to radiate energy uniformly over the inner surface of the spout.
In accordance with other features: is made of an austenitic metal, thereby yielding good energy output from the beginning to the end of the preheating operation; containing chrome; positioned lower than, and centered in relation to, the cavity of the refractory element; and, radius of curvature.
The invention also concerns a frame allowing the rapidly-detachable positioning, in a casting spout, of an element made of a refractory material belonging to a preheating device resembling that described above. This configuration is intended to minimize heat loss in the spout between the end of preheating and the filling of the spout with metal.
To achieve this goal, the frame comprises a stationary member and a movable member to which the element made of refractory material is attached. The stationary member comprises a system for guiding the mobile member, so as to hold the refractory element centered in the part during the en
REFERENCES:
patent: 4475721 (1984-10-01), Pamart
patent: 5183097 (1993-02-01), Boudot
Boudot Daniel
Comarteau Jean-Louis
Liebaut Christophe
Nykiel Patrice
Hail III Joseph J.
Lin I.-H.
SEVA
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