US2008814A - Apparatus for annealing wire - Google Patents

Description

July 23, 1935. A. F. BRADLEY APPARATUS FOR ANNEALING WIRE Filed Oct. 8, 1934 fl/erf 6. Bradley.

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Patented July 23, 1935 UNITED STATES APPARATUS FOR ANNEALING WIRE Albert F. Bradley, Sterling, Ill., assignor to Northwestern Barb Wire Company, Sterling, Ill., a

corporation of Illinois Original application June 21, 1933, Serial No. 676,769. Divided and this application October 8, 1934, Serial No. 747,414

1 Claim.

This invention relates to an apparatus for annealing wire and other strip material, and more particularly to the annealing of a wire of a ferrous metal under such conditions as to produce a finished wire having a comparatively bright surface. The invention has particular application in the manufacture of bright wire bale ties.

Heretofore. in the annealing of steel or iron wire, the heat treatment to which the wire is subjected has resulted in the production of an oxide coating on the wire. This coating is dull in character and unpleasing in appearance, frequently leading the casual observer to think that the wire is an old or used wire when, in fact, it may be new and unused.

I have now found that if the annealing of steel or iron wire is carried out under such conditions as will prevent the formation of an oxide coating on the wire, a finished wire having a relatively bright and clean surface can be produced. According to the present invention, the heat treatment of the wire is carried out in a reducing atmosphere, or, at least, a non-oxidizing atmosphere, so that practically no oxide of iron will be formed on the wire during the heat treatment step.

It is therefore an object of this invention to provide an apparatus for producing an annealed steel or iron wire having clean, bright surface characteristics, substantially free from iron oxides.

Another object of this invention is to provide an apparatus for annealing ferrous metal wire in a continuous operation, wherein the wire is passed through a reducing atmosphere at a temperature above the critical temperature of the ferrous metal, to protect the wire from oxidizing influences while it is at an elevated temperature.

A further object of the present invention is to provide an apparatus for the manufacture of relatively bright, oxide-free wire of a ferrous metal, such as iron or steel.

Other and further important objects of this invention will be apparent from the disclosures in the specification and the accompanying drawing.

This invention (in a preferred form) is illustrated in the drawing and hereinafter more fully described.

On the drawing:

Figure 1 is an end elevational view of an annealing furnace embodying the principles of my invention.

Figure 2 is a sectional view taken substantially along the line 11-11; of Figure 1.

Figure 3 is an enlarged fragmentary sectional view of the structure shown in Figure 2.

As shown on the drawing:

The reference numeral l0 indicates as a whole an annealing furnace embodying the principles of my invention. Said furnace I0 comprises an elongated retort I I supported in horizontal position by means of legs or standards l2 and provided with a front plate or wall l3. The retort It may be suitably constructed of an outer sectional, metallic shell 14 internally divided by means of an arch plate I5 to provide a fire-box l6 and a chamber ll separated therefrom by said plate IS. The fire-box is lined along the bottom thereofwith refractory bricks I8 and is provided with a fuel opening l9 at the front end and with an opening 20 at the rear end for connection to a stack or other exhaust means.

Fuel is introduced into the fire-box l6 by means of a nozzle 2| having connected therewith a fuel line 23 and an air or steam line 22. Fuel, such as 20 oil, may be introduced through the feed line 23 into the nozzle 2| and suitably atomized or sprayed from said nozzle by means of compressed air or steam to produce a relatively long flame that extends along the fire-box l6. Obviously, in place of an oil fire furnace, gas or pulverized coal may be used, or electrical heating means may be employed.

A wall or arch 24 of refractory brick is positioned in the chamber l1 above the arch plate 30 IS. The individual bricks 25 of the wall or arch 24 are provided with longitudinally extending passages 26, which are properly aligned to receive a tube 21 that extends the full length of the furnace and through the end wall thereof. At the front end of each of the tubes 21, there is provided a fitting 28 having a passaged closure 29 for the introduction of a wire 30 into the tubes and having a branch connection 3| for the introduction of a reducing gas or the like. A tube or conduit 32 is connected to each of the branches 3| of the fittings 28.

At the other ends of each of the tubes 21 there is provided a coupling 33 for joining an extension pipe 34, through which the wire 30 also extends. The pipe 34 may be of considerable length, as much as 30 to 40 feet or more, in order to provide for slow cooling of the wire after it leaves the furnace.

The tubes 21 are preferably arranged in vertically staggered relation and in two or more tiers, as best illustrated in Figure 1, with the fittings 28 correspondingly arranged and connected by the pipes 32 to a header pipe 35. By this arbale tie machine.

rangement a large number of strands of wire 30 may be passed continuously through the annealing furnace.

In operation, the annealing furnace is brought to the desired temperature by means of a combustion of the fuel supplied through the nozzle 2|. Where oil or gas is used, the temperature can obviously be regulated to within narrow limits. After the refractory bricks 25 have been heated to the desired temperature, a suitable reducing gas, such as producer gas, is introduced from the header 35 into each of the tubes 21 through the fittings 28. In place of producer gas, it is obvious that other reducing or non-oxidizing gases may be used, such as water gas, hydrogen, carbon monoxide, nitrogen and the like. The gas need not be introduced under any pressure beyond that necessary to create a slight flow of the gas in the tubes 21.

The wires 30 are drawn through the annealing furnace by suitable means (not shown) at such rate, say 75 to 100 ft. per minute, that the desired degree of annealing can take place during a single pass of the wire through the furnace.- The wire may be drawn from the tubes 34 directly into a machine of some sort, such as a The temperature to which the wire is subjected as it passes through the tubes 21 will depend upon the character or analysis of the metal from which the wire is made and also upon the degree of annealing that is desired.-

In general, of course, the temperature will be such that the wire is heated above the critical.

point of the metal, preferably to between 1500 and 1700 F. Because of the presence of the reducing atmosphere while the wire is at an elevated temperature, substantially no oxides of iron will be formed on the surface of the wire. Preferably, also, the reducing atmosphere will extend through the pipes 34, so that the wire may be brought down to a lower temperature while still exposed to a reducing atmosphere. In this way, substantially no oxide formation will take place, since, by the time the wire has left the pipes ll, the wire will be cooled to approximately atmospheric temperature.

The cooling of the heat treated wire in the pipes 34 is very slow owing to the sensible heat remaining in the wire and the atmosphere surrounding the wire as it leaves the tubes 21. The annealing of the wire is thus completed by the "soaking process that takes place in the pipes 34. The temperature of soaking" is around 1400 F. with a maximum of about 1500 F. and a minimum of about 1300' F.

The direction of flow of the gases surrounding the wires may be reversed with respect to the direction of travel of the wire, if desired. -Also, the exit gases from the tubes may be drawn off and burned to create a natural draft suflicient to cause the flow of gases through the tube.

The'finished wire of my invention is substantially free from any surface coating of oxide and is therefore comparatively bright and shiny in appearance. Furthermore, owing to the occlusion of some of the reducing gases in the metal of the wire, the wire produced according to my method tends to resist oxidation or rusting for a I considerable period of time after manufacture. The bright, shiny appearance of the wire of my invention makes such wire much more desirable than the dull, almost black, annealed wire of the usual type heretofore produced. In particular, the annealed iron or steel wire of my invention is especially adapted for use as wire bale ties.

The present application is a division of applicants co-pending application Serial N0. 676,769, filed June 21, 1933.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon, otherwise than is necessitated by the prior art.

I claim as my invention:

An annealing furnace comprising an elongated housing providing a full length combustion chamber and a full length refractory ceiling therefor, said ceiling having tiers of passages extending therethrough, conduits aligned with said passages and extending from the exit ends thereof and entirely exposed to the atmosphere, means for introducing a reducing gas into the entrance ends of said passages, and sealing means at said entrance ends permitting the admission into said passages of strip material to be annealed.

ALBERT F. BRADLEY.

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