Dispensing – Molten metal dispensing – With heating or cooling
Patent
1997-08-08
1998-12-29
Kastler, Scott
Dispensing
Molten metal dispensing
With heating or cooling
266237, B22D 3506
Patent
active
058536051
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention concerns pouring liquid metal in order to manufacture objects from steels, superalloys and other ferrous or non-ferrous metal alloys.
The invention relates, in the first place, to a pouring duct incorporating a closed cross section opening, at one end, into a pouring orifice in order to feed at least one mold, and of the type comprising, along its length, at least one heating element composed of an induction through whose cooled turns an alternating electric current (.about., U,F) flows. The coil is embedded in concrete surrounding a heat-resistant tube (see, for example, U.S. Pat. No. 5,708,257 in the Applicant's name). This duct proves especially advantageous for pouring metals having high melting points.
This heating duct eliminates the danger of cooling and solidification of a metal alloy having a pouring temperature of at least 1,400.degree. C. between two successive pouring operations.
Furthermore, this duct configuration yields a number of advantages over the conventional state of the art, these advantages being described, for example, in U.S. Pat. No. 4,475,721 in the name of Pont-a-Mousson SA and relating to the simplicity of manufacture of the duct (see U.S. Pat. No. 5,708,257 in the Applicant's name).
However, a number of heterogeneous temperature phenomena can be observed in this type of duct, which become more pronounced when the duct is rounded. As a consequence, metal-filling and -solidification differences occur in the casting mold.
SUMMARY OF THE INVENTION
This invention is intended to solve these problems. In particular, the homogeneous temperature of the metal ensures the uniformity of the conditions for filling and solidification of complex or multiple impressions in a casting mold, thereby making it possible to strictly control the defect rates (shrink cavities, cracks, etc.) found on the objects. The duct according to the invention gives such results because of asymmetrical induction coil turns. To make uniform the longitudinal temperature variation of the metal, the turns in the inductor are shifted and the density thereof increases at the end of the pouring orifice designed for feeding the mold.
To make uniform the transverse variations of the metal temperature, the inductor turns form a spiral which is offset, in relation to the duct, toward the axis of rotation of the covering torus of this duct.
In accordance with other variants:
The invention also concerns a process intended to yield the same results. This process for achieving homogenization of the temperature of a metal circulating in a duct in the shape of a partial torus of the type described above is characterized by the fact that an electric current having a frequency of less than 15,000 Hz is fed to the inductor.
The invention also concerns a low-pressure metal pouring unit comprising a foundry ladle incorporating a pressurized gas source which opens into the upper part of the ladle and a metal-outlet orifice, this unit being characterized by the fact that the outlet orifice empties into a duct conforming to the duct described above.
BRIEF DESCRIPTION OF THE FIGURES
One embodiment of the invention will now be described with reference to the attached drawings, in which:
FIG. 1 is a vertical cross-section of a heated pouring duct according to the invention.
FIG. 2 is a vertical cross-section of a reduced-pressure metal pouring unit comprising a duct of the type described in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The apparatus shown in FIG. 1 is a duct 1 having a closed cross-section which opens at one end through an orifice 2 and comprises, over the length thereof, a heating element constituted by a coil-shaped inductor 3 through whose cooled turns 4 an alternating electric current (-, U,F) travels. This inductor 3 is embedded in concrete 5 surrounding a heat-resistant tube 6. The turns 4 are asymmetrical in relation to the axes of symmetry of the duct X--X' and Y--Y'. The duct is shaped like a partial torus, the axis of rotation of which passes t
REFERENCES:
patent: 4475721 (1984-10-01), Pamart
Comarteau Jean-Louis
Liebaut Christophe
Nykiel Patrice
Remy Alain
Kastler Scott
SEVA
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