US3182982A - Infra-red wire annealing apparatus - Google Patents

Description

May 11, 1965 D. E. RUFF INFRA-RED WIRE ANNEALING APPARATUS Filed Aug. 15, 1962 mub am m u Q 539w A TTOR/VEYS United States Patent This application is a continuation-in-part of application Serial No. 83,966, filed January 23, 1961, now abandoned.

This invention relates to an improved apparatus for carrying out infra-red heating of metallic strips within a confined tube of quartz glass or other material capable of transmitting or passing infra-red heat energy. More particularly the improved apparatus is designed and arranged to effect the bright annealing of copper wire, or where desired the heat treating of other metals in strip form, in a continuous and efficient manner.

The bright annealing of continuous copper wire, or other strip metals, has generally been carried out in electric or gas fueled ovens and furnaces containing a controlled inert atmosphere, and such ovens have been of both the recirculating and non-recirculating type, utilizing relatively large quantities of the inert atmosphere. There are, however, various problems and disadvantages in connection with the various oven and furnace structures which are in general use. For example, an oven type of construction must be made gas-tight to preclude the infiltration of oxygen, and it must be constructed of high temperature resistant alloys or refractories so that as a result the cost of fabrication is high. Large ovens necessarily require relatively large volumes of an inert gas supply in order to fill the interior thereof. Also, by reason.of physical size, the oven type of annealing chamber requires considerable heating time and a large fuel consumption to maintain temperatures at suitable an-- nealing ranges.

Prior types of tubular annealing chambers have made use of electrical resistance wires wound around a tubular heating chamber, which may have been formed of fused quartz glass, containing a controlled atmosphere; however, electrical resistance heating requires a high power input and there is the problem of frequently burning out the heating elements.

In addition to the high operating cost factor, electrical resistance coils generally provide a relatively slow rate of heat transfer to the work passing through the controlled atmosphere in the tubular chamber.

The present improved apparatus is designed and constructed to utilize a substantially uniform inexpensive source of catalytically generated infra-red heat arranged in a manner surrounding a tubular treating chamber; however, it is not intended to limit the source of infrared energy to any one type or form. The apparatus incorporates an elongated tubular chamber formed of transparent or translucent silica or quartz glass, or of other infra-red transmitting material, such as fluorite. The chamber is of small cross-section, being merely large enough to accommodate the strip to be heat treated, so that as a result only a small volume of inert gas is required to carry out the annealing operation. Fused quartz glass or other infra-red heat transmitting materials have the ability to transmit infra-red waves therethrough without actually conducting heat to any extent. The low heat conductivity characteristic is an advantage in that it permits high -temperature infra-red heating throughout a heating zone while maintaining relatively cool temperatures at the ends of the confined heat treating section, a short distance from the infra-red heat source. Thus, there may be permitted metal to glass seals by the use of compounds or materials, which are 3,182,982 Patented May 11, 1965 necessarily high temperature resistant at the ends of the glass heat treating section.

The bright annealing of copper wire, or of other nonferrous and ferrous metals, is carried out in an atmosphere precluding the presence of oxygen such that there is no discoloring oxide formed on the metal strip during the annealing or heat treating operation. present tubular form of apparatus provides means for introducing the controlled annealing gas under a slight superatmospheric pressure in a manner precluding the infiltration of oxygen.

A preferred form of the improved annealing apparatus utilizes an externally encompassing tubular form of infrared heater that is gas fueled. Also, a preferred form of the unit utilizes a catalytically activated metallic surface, such as platinum and/or palladium coated on a stain less steel gauze, as a means for effecting the low temperature catalytic oxidation of the gaseous fuel supply, such that there is resulting. infra-red heat radiated from the catalytic surface and directed to and through the glass heating chamber of the annealing section. A symmetrical tubular form of infra-red transmitting glass permits a uniform radiation to the interior thereof and a uniform heat transfer to the metal strip or wire being annealed therein. By controlling the rate of supply of the gas fuel to the infra-red heat radiating surface, there may be effected a control of the infra-red energy and wave length and temperature being transmitted directly through the tube to the material undergoing the bright annealing or other heat treating operation.

It is a principal object of the present invention to provide a tubular infra-red heat transmitting chamber in combination with an encompassing form of infra-red heat source and controlled inert atmosphere retaining means within the tubular chamber such that there may be effectively carried out the annealing or heat treating of wire, rods, or fiat-strip forms of material.

. It is also an object of the present invention to provide an improved heat treating or annealing apparatus which utilizes a catalytically activated metallic screen-like surface as a means for catalytically oxidizing a gaseous fuel adjacent the annealing chamber and as a means for pro- I bodied in the annealing apparatus of this invention may I be more easily described, and the advantages thereof pointed out, by reference to then accompanying diagrammatic drawing and the following description thereof.

Referring now to the drawing, there is indicated an elongated tubular infra-red heat transmitting glass section 1, which in accordance with the present invention is non-metallic and is formed of fused quartz or silica glass,

or perhaps of a fluorite containing transparent or translucent material, capable of readily transmitting infrared heat waves. The tube 1 is positioned angularly, thus having an upper end and a lower end. The upper end of tubular chamber 1 connects with an inlet housing 2 while the lower end connects with an outlet housing section 3. The end sections may be formed of metal, glass or other heat resistant material that may be suitably bonded to the infra-red heat transmitting glass tube 1. As previously pointed out, quartz glass or other infra-red heat transmitting types of glass are generally poor heat conductors.

Thus, the

-apparatus for heat treating purposes.

such that the ends of the tube 1 extending beyond the heating section may be sutficiently cool to permit the use ing indicates diagrammatically that the end sections 2 and 3 are attached to the tube 1 by a suitable sealing material 4. The extremities of the end sections 2 and 3 are provided respectively with closure members 5 and 6 that are designed to'maintain in a relatively gas-tight manner a suitable inert atmosphere within the interior of the heating tube 1. The closures 5 and 6 necessarily have smallcentral openings 7 and 8, respectively, in order to accommodate the passage of a wire or bar 9 through the The overall size andshape of the openings 7 and 8 for each apparatus will, of course, be modified to conform with the size and shapeof the wire passing through the heat treating apparatus.

In order to maintain a controlled substantially oxygenfree atmosphere in the heat treating section, nitrogen,

carbon dioxide, or other controlled composition gas is continuously or periodically supplied to the tubular heating section by means of an inlet line 10 and control valve 11. Where a continuous introduction is desired, the annealing gas may be continuously discharged through outlet line 12, having control valve 13, which connects with the upper wire inlet section 2. This arrangement provides a countercurrent flow between the incoming gas stream and the downwardly moving wire 9 which is to be treated; however, where desired, the annealing gas may be introduced through line 12 and valve 13 and subsequently discharged through line 10, or through the wire openings 7 and 8.

Encompassing the tubular glass chamber 1, there is provided in this embodiment an infra-red heater means having a catalytically activated porous metallic surface 14 suitable to effect the oxidation of a gaseous fuel and thus provide in turn a glowing flameless infra-red heat radiating surface. A suitable catalytic coating for this purpose is that disclosed in the Suter and Ruff Patent No. 2,720,494, issued October 11, 1955, that is, an alloy metal screen having platinum or palladium deposited thereon. As an example, a chrome-nickel stainless steel (Chromel or Nichrome) screen of approximately 40- a mesh is precleaned by immersion in a hot surface active agent, thoroughly rinsed with steam or hot water, and then subjected to plating by immersion or by electroplating. Preferably a coating of platinum and/or palladium is deposited by electroplating to a suitable well bonded coating of less than about 0.5 millimeter in thickness. After plating, the catalyst coating is thoroughly rinsed free of soluble materials and is heated to a temperature above about 600 F. in an air stream containing volatile hydrocarbons, such as hexane, in concentrations below the lower limit of explosibility, permitting surface combustion to take place and effecting a conditioning and increased tenacity of the coating to the base metal. When in use, the catalytically activated metal screen will effect the flameless catalytic combustion of the fuel-air mixture passing therethrough and give a high energy infra-red heat source adjustable through a relatively wide temperature range.

There is indicated diagrammatically a housing or heating chamber 15 of tubular form surrounding and enclosing the inner catalytic surface 14. The chamber 15 is adapted to receive a gaseous fuel from line 16, having control valve 17, and distribute it circumferentially to the backside or surface of the catalyzed member 14. The fuel to the unit may be propane, butane, or mixtures thereof, natural gas, or other forms of light gaseous fuel, and is distributed within the chamber 15 throughout a substantially open annular-shaped fuel distributing section 18 and then passes uniformly at relatively low velocity through a gas distributing layer, such as screen 19 and a pervious wool-like material 20, which, as indicated, is

packed between the screen 19 and the catalytically activated member 14. The wool-like material 20 may comprise a heat resistant ceramic or mineral wool, or may be formed of a metal wool, such as steel wool. The wool-like layer 20 is maintained in a multi-fold thickness as compared to the catalytic screen or mesh 14 such that there is sufficient pressure drop to insure uniform distribution of the gas fuel stream to the catalytic surface 14, and such that there is suflicicnt thickness of insulation to preclude the radiation and transmission of heat from the radiant surface 14 to the gas distributing zone 18, whereby to in turn preclude, the chance of backflashing and any explosion taking placeat the fuel source. Also in a desired construction, at least one heat reflecting screen 21 may be incorporated into the infrared heating unit so that there is an additional membrane etfectingthe reflection of heat outwardly from the catalytic surface 14 and a diminishing of the chances of a backfire" to the fuel supply source. The screen member 21 may be positioned inwardly from'and directly adjacent the catalyzed mesh 14. Although not shown in the drawing, the pervious wool backing 20 may comprise one or more layers of different density Wool-like material, or layers of different materials, such as a combination of ceramic wool and steel wool. Still further, in lieu of the wool-like material 20, the distributing layer may comprise the use of two or more layers of fine and/ or medium mesh alloy screens. For example, a suitable heat reflecting and gas distributing media has been formed of a combination of one 16-mesh screen along with two 40-mesh screens placed in back of or upstream from the coated screens, in the position of the material 20.

Although not deemed as desirable, an electrical coil type of infra-red heat source may also be used to encompass the tube ll. Varying shapes may be used for the infra-red heat emitting surface 14 and the chamber 18. The present embodiment indicates diagrammatically a circular cross section catalyzed membrane 14 encompassing a round tubular glass member 1. However, other shapes may be utilized as, for example, a square or rectangular shaped infra-red surface, and the enclosing chamber providing for the gas distribution to the catalytic radiating surface may well be a similar shape, providing a substantially uniform heat transmission to the inner infra-red heating section. for moving or retracting the infra-red heat source from around the tubular unit 1, with control means for stopping the infra-red heating when the wire or strip material is stopped from its continuous passage through the heat treating section. A cylindrical heating unit hinged on one side and designed to open on an opposing side, may

be used to operate in a clam shell type of action, with means being provided to open and move back the heat radiating surfaces responsive to means sensing a slowdown or stoppage of wire undergoing heat treatment. In another type of arrangement, a U-shaped infra-red heater section may be retracted away from a substantially fixed wall section which serves as a closure for the U-shaped portion of the heating section and a resulting tubular unit when closed. In which case, automatic means may be used to effect the movement of the U-shaped section away from the fixed wall closure section and from the glass tube treating section.

Also, as previously indicated, the present improved a apparatus arrangement places the glass tubular memher 1 and the movement of the wire therethrough in a vertical or angular position, such that there is provided a lower outlet end for the wire passing therethrough. In

portion of the annealing gas inlet section 3. The cooling liquid which may be water or other inert liquid with respect to the metal being treated is introduced to the con- Means may also be provided tainer 23 by way of line 24 and valve 25 and is maintained at sufiicient depth and penetration into the lower end of the outlet section 3 such that a gas seal is maintained in the tubular heating section. The liquid seal may be used entirely in place of the closure member 6, or alternatively, in combination therewith.

Suitable pulley or roller means 26 may be positioned in the lower part of chamber 23 so as to suitably guide the wire 9 from the cooling liquid Has it is being continuously withdrawn from heat treating chamber 1 and cooling liquid 22. A liquid outlet line 27 and valve 28 provides means for maintaining a given liquid level within chamber 23, particularly when there is a continuous introduction of cooling liquid 22 into chamber 23. Various shaped liquid retaining chambers may be utilized in connection with the lower end of outlet section 3 and various types of pulley or guide arrangements may be used to pass the Wire 9 through the cooling liquid chamber, and it is not intended to limit the present invention to any one shape or design or arrangement in connection with providing the liquid at the outlet end and guiding the wire therefrom.

I claim as my invention:

1. An infra-red annealing apparatus comprising in com bination a confined tubular infra-red heat transmitting chamber having opposing inlet and-outlet ends adapted to accommodate the passage of a material to be heat treated, an infra-red heat source comprising a catalytically activated metallic member substantially encompassing said chamber, gas seal means at each end of said chamber, a gas inlet means at one end of said chamber and a gas outlet at the other end thereof providing an annealing gas atmosphere therein.

2. The apparatus of claim 1 further characterized inv that said tubular chamber is positioned to have an upper end and lower end, and the gas seal means at the lower end of said tubular chamber comprises means for maintaining a cooling liquid pool across such lower end whereby the material being heat treated in said chamber passes through said cooling liquid as it is discharged therefrom.

3. An infra-red annealing apparatus comprising in combination, a confined tubular infra-red heat transmitting chamber having opposing inlet and outlet ends adapted to accommodate the passage of a material to be heat treated, an infra-red heat source comprising a catalytically activated metallic screen which is adjacent to and sub stantially. encompasses said tubular chamber, a gaseous fuel supply and fuel distributing means encompassing said catalyticzilly activated screen and fuel inlet means to said distributing means whereby the oxidation of the fuel supplied to said screen by said distributing means provides 5 v infra-red heat energy for transmission through said tubular chamber to the material passing therethrough, gas seal means at each end of said tubular chamber, annealing gas inlet means at one end of said chamber and gas outlet means at the other end thereof providing for the maintenance of an annealing gas atmosphere therein.

4. An infra-red annealing apparatus adapted to effect the bright annealing of wire within a controlled atmosphere and comprising in combination, a confined tubular infra-red transmitting chamber positioned to have an upper end and a lower end, a wire inlet means at the upper end of said chamber adapted to pass a continuous strand of wire into said chamber and substantially retain a confined gaseous medium within said chamber, a container adapted to maintain a cooling liquid pool around and within the lower end of said tubular chamber providing thereby a gas seal means at the lower end of said chamber and a cooling medium for contacting the wire strand being discharged from the lower end of said chambcr following heat treatment therein, an annealing gas inlet at one end of said chamber, and a gas outlet from the other end thereof, an infra-red heat source comprising a catalytically activated metallic member encompassing substantially circumfcrentially said tubular chamber whereby infra-red heat may be transmitted through said chamber to said wire passing therethrough, and wire guide means in the lower portion of said cooling liquid container for withdrawing the heat treated wire from the lower end of said chamber and from said cooling liquid pool.

5. An infra-red annealing apparatus for effecting the bright annealing of wire within a controlled inert atmosphere, comprising in combination, a confined elongated quartz glass tube positioned angularly to have an upper end and a lower end, a closure member at the upper end of said quartz glass tube having an aperture therethrough to accommodate the introduction of-wire to be annealed in said tube, liquid retaining means positioned to maintain a cooling liquid around the lower end of said glass tube and providing thereby a resulting liquid gas seal covering the lower end of said tube, whereby an inert annealing gas may be maintained therein, and whereby said'cooling liquid contacts the wire being passed through said glass tube, an annealing gas inlet at one end of said glass tube and gas outlet from the opposing end thereof, a catalytically activated alloy metal screen positioned around and spaced providing an infra-red heat source encompassing substantially circumferentially said glass tube whereby infrared heat is transmitted through said quartz glass tube to said wire passing therethrough, a layer of pervious heat resistant and gas distributing material around said catalytically activated screen and encompassing the latter, said material of multifold thickness relative to said catalytic screen and providing simultaneously a fuel distributing layer and a heat reflective material adjacent said screen, a fuel receiving and distributing chamber encompassing both said catalytic screen and said pervious mate- :rial for distributing fuel to the latter, fuel inlet means to said fuel receiving and distributing chamber, and wire guiding means within said cooling liquid retaining means for discharging said wire as it is continuously withdrawn from the lower end of said glass and said cooling liquid.

References Cited by the Examiner UNITED STATES PATENTS MORRIS O. WOLK, Primary Examiner. RAY K. WINDHAM, Examiner.

a short distance from said glass tube-

Claims (1)

1. AN INFRA-RED ANNEALING APPARATUS COMPRISING IN COMBINATION A CONFINED TUBULAR INFRA-RED HEAT TRANSMITTING CHAMBER HAVING OPPOSING INLET AND OUTLET ENDS ADAPTED TO ACCOMMODATE THE PASSAGE OF A MATERIAL TO BE HEAT TREATED, AN INFRA-RED HEAT SOURCE COMPRISING A CATALYTICALLY ACTIVATED METALLIC MEMBER SUBSTANTIALLY ENCOMPASSING SAID CHAMBER, GAS SEAL MEANS AT EACH END OF SAID CHAMBER, A GAS INLET MEANS AT ONE END OF SAID CHAMBER AND A GAS OUTLET AT THE OTHER END THEREOF PROVIDING AN ANNEALING GAS ATMOSPHERE THEREIN.

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