Electric heating – Inductive heating – Specific inductor configuration
Patent
1995-09-26
1998-01-13
Echols, P. W.
Electric heating
Inductive heating
Specific inductor configuration
29611, 29DIG46, 373160, 392479, H05B 636
Patent
active
057082570
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention under consideration relates to a heating device designed for the transfer of liquid metal, said device having a closed transverse section. The invention concerns, first, a process for manufacture of a device of the aforementioned type terminating at one end in a pouring orifice serving to feed at least one mold, and of the type comprising over its entire length at least one heating apparatus formed by a coil-shaped inductor, through whose turns an alternating electric current circulates.
The metal-transfer heating devices (cf. the tapping spout described in French Patent No. 2 532 866) are especially advantageous for transferring a metal heated to high casting temperature. Said heating devices remove the risk of cooling and solidification of a metal alloy at a casting temperature of at least 1,400.degree. C. in a spout between two successive casting operations.
According to a conventional technique, the spout comprises a graphite susceptor sleeve tube incorporating a right-hand portion and a bent portion.
This configuration is especially advantageous when the casting is carried out discontinuously. Indeed, in this case the liquid metal may not be present in the spout for a relatively long period. It is then helpful to keep the spout preheated for this period of time, a function performed by the graphite. However, when working continuously, as is the case in stabilized production processes involving large or medium-size quantities, this advantage diminishes. In this case, the continuous presence of the liquid metal in the spout, combined with induction heating, keeps the system at the proper temperature. Thus, the graphite is no longer necessary, especially because the initial preheating of the spout, before filling it with liquid metal, can be carried out using an accessory, more flexible and less costly heating system, such as one using gas.
Moreover, the conventional configuration exhibits a number of disadvantages in use associated with the complexity of the manufacture of the spout: i.e., problems related to forming, cutting, and centering. These difficulties increase the spout-manufacturing cost.
SUMMARY OF THE INVENTION
The invention is intended to solve these problems. To this end, the process according to the invention includes the following steps: refractory ceramic tube, the insulation-covering assembly comprising a layer of refractory insulation concrete and/or at least one layer of a fibrous material, refractory concrete while generating vibrations thereon,
According to certain characteristics the process includes one or several steps involving cutting and/or assembly of the refractory tube.
The layer of insulating material (refractory concrete and/or fibrous material) has the advantage of supplying good thermal insulation of the tube and the metal during use.
The fibrous layers provide a higher level of insulation than do refractory concretes and strengthen the insulation.
Furthermore, the insulating layer gives additional protection in the event of wear and/or cracking of the ceramic tube in contact with the liquid metal, thereby lessening the risks of infiltration of liquid metal into the winding and increasing safety.
Heating and temperature-maintenance of the liquid metal contained in the refractory spout are provided by the inductor, through which an alternating current circulates at medium or high frequency. This heating method allows direct transfer of electrical energy, in the form of thermal energy, to the liquid metal. Since no intermediate element, such as graphite, is used, the energy transfer is direct and yield is enhanced. The frequency passing through the inductor falls, typically, within the range 1,000-15,000 hertz.
The invention also concerns a heating device for transfer of liquid metal. This device, which has a closed transverse cross-section, extends upward and ends, on its upper face, in a pouring or outlet orifice used to feed at least one mold, and is of the type comprising over its entire length at least one heating mechan
REFERENCES:
patent: 3604598 (1971-09-01), Kappmeyer et al.
patent: 4161647 (1979-07-01), Carbonnel
Boudot Daniel
Comarteau Jean-Louis
Nykiel Patrice
Remy Alain
Echols P. W.
SEVA
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