Furnace And Method For Induction Heating Moving Quantities Of Material

Abstract

An induction furnace and method for heating moving quantities of material to elevated temperatures. The furnace utilizes a tubular susceptor member having a refractory medium positioned substantially thereabout. A means is also provided substantially about the refractory medium for cooling the tubular susceptor member and refractory medium.

Description

BACKGROUND OF THE INVENTION

This invention relates to induction furnaces and more particularly to induction furnaces for heating moving quantities of material. Even more particularly, this invention relates to induction furnaces able to heat moving material to high temperatures, i.e., in excess of 2,000.degree.C.

The utilization of refractory materials in induction furnaces has long been preferred. These materials primarily perform electrical and thermal insulating and similar functions within the furnace to protect such components as the coil and similar members from damage as a result of continued exposure to the relatively high temperatures present. As is well known, however, many of these refractory materials exhibit deleterious properties when subjected to elevated temperatures in the ranges described. For example, some tend to volatilize quite readily at such temperatures. Many also are too susceptable to thermal cracking and spalling.

With particular regard to induction furnaces capable of heating quantities of materials passing therethrough to temperatures exceeding 2,000.degree.C, the present invention involves the utilization of a tubular susceptor member positioned within the heating chamber of such a furnace and adapted for having the material to be heated pass therethrough. This susceptor is preferably of a high temperature refractory metal, such as tungsten. Utilization of such a susceptor member permits the incorporation of the previously mentioned refractory materials in a manner to be described.

OBJECTS AND SUMMARY OF THE INVENTION

It is therefore a primary object of this invention to provide a new and unique furnace for inductively heating quantities of material passing therethrough.

It is a further object of this invention to provide such a furnace which is capable of heating such moving materials to temperatures in excess of 2,000.degree.C.

An even further object of this invention is to provide a furnace as described above which permits the utilization of refractory material therein.

Still another object of this invention is to provide a furnace as described above which utilizes a susceptor in tubular form adapted for having the material to be heated pass therethrough.

In accordance with one aspect of this invention, there is provided an induction furnace for heating a quantity of material passing therethrough. This furnace comprises a housing member of a thermally conductive material and having an inlet port and exit port therein, a tubular susceptor member within the chamber of the housing member, a refractory medium positioned substantially about the tubular susceptor member, means within the chamber and substantially about the refractory medium for inducing electrical current within said tubular susceptor member, and for cooling the tubular susceptor member and the refractory medium.

In accordance with another aspect of this invention there is provided a method for heating to a preestablished temperature a quantity of material passing through an induction furnace which utilizes a tubular susceptor member and a refractory medium positioned substantially about the tubular susceptor member. The method comprises inducing electrical current within the tubular susceptor to cause the susceptor to become heated substantially to the required preestablished temperature whereupon the quantity of material to be heated is passed therethrough so that this material will be heated to said temperature.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is an isometric view of one embodiment of the present invention.

FIG. 2 is a side elevational view, partly in section, as taken along the line 2--2 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

With particular reference to the drawings, there is illustrated in FIG. 1 a preferred embodiment of an induction furnace in accordance with the present invention. Furnace 10 is shown to comprise a housing member 13 having an inlet port 15 and an exit port 17 (hidden) through which a predetermined quantity of material 19 may pass. In comparing FIGS. 1 and 2 of the drawings, it can readily be seen that material 19 may pass through furnace 10 in either direction and is thus not limited to that indicated. It should also be understood that material 19 may be in the form of several rod or wire type items which may pass through the furnace concurrently and be heated therein. For reasons of simplification, however, material 19 is illustrated as a single rod member. The means for driving material 19 through furnace 10 may be chosen from any of several well known in the art, i.e., a single push rod or similar member, and accordingly does not constitute an essential component of the present invention.

As shown in FIG. 1, furnace 10 is supported on stand means 21 which is further comprised of two separate leg sections 23 and 23'. As with the drive means for material 19, these members are illustrated simply as being representative of several members capable of performing such a function. Furnace 10 could even be suspended from a ceiling or similar structure. A temperature recording means, illustrated as a thermometer 25, may be utilized to provide the furnace operator with a ready indication of the operating temperature of furnace 10.

With particular reference to FIG. 2, furnace 10 is shown in section, thereby exposing the relative positions of the furnace components therein. More specifically, furnace 10 defines a chamber 27 in which is positioned tubular susceptor 29. Housing 13 of furnace 10 is of a good thermally conductive material such as copper to assist in the dissipation of heat built up within chamber 27. Inlet and exit ports 15 and 17, respectively, are also shown. Susceptor 29 aligns with the inlet and exit ports in the manner indicated to thereby permit the passage of material 19 therethrough. A preferred material for susceptor 29 is tungsten although this component could also be produced from practically any of the other high melting refractory metals such as tantalum or molybdenum. Tungsten is preferred because of its relatively higher temperature capabilities. A refractory medium 31 is positioned substantially about susceptor 29 to serve as an electrical and thermal insulator for the susceptor. More specifically, refractory medium 31 insulates susceptor 29 from the means 33 for inducing electrical current within the susceptor. As shown, means 33 comprises a coil 35 positioned substantially about refractory medium 31. A unique feature of means 33 is its ability to serve a dual function in that it also provides a means whereby susceptor 29 and medium 31 are cooled. This is achieved by the circulation of a cooling medium such as water through coil 35. Electrical potential is therefore readily supplied coil 15 by simply affixing electrical leads 37 to the protruding portions 39 and 39' of the coil. Leads 37 are in turn electrically connected to an established power source (not shown). Portions 39 and 39' are electrically insulated from housing 13 by a pair of insulation members 40 and 40', respectively. To maintain furnace 10 at the temperature described (above 2,000.degree.C) approximately 20-25 kilowatts/hr. are required from the power source. It is understood to the cooling medium circulated through coil 35 may be pumped or similarly provided by a pumping means (not shown) and further description of such a component is not considered necessary. When using water as the cooling medium, a typical pressure utilized in the present invention is approximately 55-65 pounds per square inch.

As can further be seen with reference to FIG. 2, there is positioned within chamber 27 a pair of opposing support refractories 41 and 41' which serve to hold susceptor 29 and the refractory medium 31 in position. It is preferred that the material for support refractories 41 and 41' be substantially the same as that of refractory medium 31, that being one of the more commonly available refractory oxides. Typical examples of such materials which can be utilized with the present invention include ZrO.sub.2, Al.sub.2 O.sub.3, and MgO. Of these, it is preferred to use either ZrO.sub.2 or Al.sub.2 O.sub.3 primarily because of their ready market availability. It can also be seen with regard to FIG. 2 that support refractories 41 and 41' and refractory medium 31 could be produced as a single unit. However, for improved assembly purposes, it is preferred to utilize these components in the manner indicated.

In the preferred embodiment of the present invention, a non-oxidizing medium is introduced into chamber 27. A primary function of this medium is to prohibit oxidation of the susceptor at the elevated temperatures described. The medium enters chamber 27 via pipe 43 and is further evenly distributed through a plurality of spaced apertures 45. The non-oxidizing medium described serves to sweep any vapors or similar toxic substances from chamber 27 and thus prevent their attacking susceptor 29. Such toxic substances are quite often the byproducts of the naterials typically heated in induction furnaces. When utilizing a susceptor comprised substantially of tungsten, it is preferred to use hydrogen as the non-oxidizing medium although several other mediums are acceptable, i.e., argon and nitrogen. Hydrogen is particularly preferred in that it may be ignited at ports 15 and 17 to provide a ready indication that this medium is sufficiently being provided within furnace 10. A typical flow rate for this medium is approximately 40-60 cubic feet per hour.

Furnace 10 may be utilized for any of several purposes. A particular useful purpose is the recrystallization of high-temperature metal wiring or rods such as tungsten. After completion of the recrystallization phase, this material is then subjected to subsequent engineering operations such as swaging, rolling or drawing. Recrystallization of a material such as tungsten in the form of a solid rod having a diameter of from about 0.200 to about 0.400 may be successfully achieved by utilizing the amounts of power, cooling medium, and non-oxidizing medium described and passing the material through chamber 27 at the rate of approximately 10 to 20 inches per minute.

Thus there has been shown and described a furnace and a method for induction heating a moving quantity of material to temperatures in excess of 2,000.degree.C. As also described, this furnace can be constructed from readily available and relatively inexpensive materials and is comparatively easy to operate.

While there has been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

What is claimed is:

1. A high temperature induction furnace for heating a quantity of material passing therethrough, said furnace comprising:

a housing member defining a chamber, said housing member comprised of a thermally conductive material and having an inlet port and exit port therein;

a tubular susception member within said chamber, said susceptor member positioned relative to said inlet and exit ports and adapted for having said quantity of material pass therethrough;

a refractory medium positioned substantially about said tubular susceptor member; and

means within said chamber and substantially about said refractory medium for inducing electrical current within said tubular susceptor member and for cooling said tubular susceptor member and said refractory medium.

2. The induction furnace according to claim 1 wherein said means for inducing electrical current within said tubular susceptor member and for cooling said tubular susceptor member and said refractory medium comprises an electrically conductive coil member positioned substantially about said refractory medium, said coil member adapted for having a cooling fluid pass therethrough.

3. The furnace according to claim 1 wherein said thermally conductive material for said housing member is copper.

4. The furnace according to claim 1 wherein said tubular susceptor member is comprised of tungsten.

5. The furnace according to claim 1 wherein said refractory medium positioned substantially about said tubular susceptor member is comprised of zirconium oxide.

6. The furnace according to claim 1 wherein said refractory medium positioned substantially about said tubular susceptor member is comprised of aluminum oxide.

7. The furnace according to claim 1 further including means for introducing a non-oxidizing medium within said chamber of said housing member.

8. The furnace according to claim 7 wherein said nonoxidizing medium is hydrogen.

9. The furnace according to claim 2 wherein said coil member is comprised of copper.

10. A method for heating to a preestablished temperature a quantity of material passing through an induction furnace utilizing a tubular susceptor member adapted for having said quantity of material pass therethrough, a refractory medium positioned substantially about said tubular susceptor member, and means positioned substantially about said refractory medium for inducing electrical current within said tubular susceptor member and for cooling said tubular susceptor member and said refractory medium, said method comprising:

applying electrical energy to said means positioned substantially about said refractory medium to induce electrical current within said tubular susceptor member to cause said susceptor member to become heated substantially to said preestablished temperature; and

passing said quantity of material through said tubular susceptor member within said furnace at a preestablished rate whereby said material will become heated to said preestablished temperature.

11. The method according to claim 10 wherein said preestablished temperature is greater than 2,000.degree.C.