US3830478A

US3830478A - Continuous metal wire annealing furnace

Info

Publication number: US3830478A
Application number: US00322355A
Authority: US
Inventors: P Pietroni
Original assignee: TECHNOFIL SpA
Current assignee: TECHNOFIL SpA
Priority date: 1973-01-10
Filing date: 1973-01-10
Publication date: 1974-08-20
Anticipated expiration: 1991-08-20

Abstract

An annealing furnace for a wire-drawing machine having a preheating chamber through which a metallic drawn wire is continuously advanced by sets of pulleys applying different electrical currents along different runs of the wire for preheating it in a non-oxidizing atmosphere and for heating it to an annealing temperature in a tubular annealing chamber in a nonoxidizing atmosphere. After annealing the wire a series of independent cooling chambers cool the wire as it advances through them consecutively. The cooling chambers are provided independently with cooling liquid.

Description

1 Aug. 20, 1974 United States Patent 1191 Pietroni CONTINUOUS METAL WIRE ANNEALING 3,608,344 9/1971 Schwan...................................72/38 FOREIGN PATENTS OR APPLICATIONS FURNACE [75] Inventor:

Piero PietrontAscoliPiceno,Italy 4,322,491 0/1968 Japan..................................219/155 [73] Assignee: TechnofilS.p. A., Ascoli Piceno,

Primary Examiner-Roy Lake Italy Assistant Examiner-Paul A. Bell 22 Filed: Jan. 10, 1973 211 Appl.No.:322,355

Attorney, Agent, or FirmRobert E. Burns; Emmanuel J. Lobato; Bruce L. Adams [57] ABSTRACT An annealing furnace for a wire'drawing machine hav- [52] US. 266/3 R [51] Int. C2ld 9/62 [58] Field of Search................. 266/3 R; 72/38, 321;

ing a preheating chamber through which a metallic 148/132, 111, 154; 219/155; 432/8, 59 drawn wire is continuously advanced by sets of pulleys applying different electrical currents along different [56] References Cited runs of the wire for preheating it in a non-oxidizing at- UNITED STATES PATENTS mosphere and for heating it to an annealing temperature in a tubular annealing chamber in a non-oxidizing atmosphere. After annealing the wire a series of independent cooling chambers cool the wire as it advances through 1 them consecutively. The cooling chambers are provided independently with cooling liquid.

7 Claims, 3 Drawing Figures 2,457,870 1/1949 Cook 2,589,283 3/1952 O'Grady 2,726,971 12/1955 OGrady 2,954,459 9/1960 Bruestle.....

2,976,397 3/1961 Ellis, Jr...... 3,011,928 12/1961 Kopec et al 3,518,405 6/1970 Herren et 211....

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PATENTEnwczmsn SEEN 2 BF 2 dig/Q 2 CONTINUOUS METAL WIRE ANNEALING FURNACE BACKGROUND OF THE INVENTION The present invention refers generally to heat treating and more particularly to an annealing furnace for metal-wire drawing machines.

It is well known that metal wires, particularly copper wire, when drawn, suffer a work-hardening effect and must, after drawing, be annealed at a temperature of about 550-600C, in a non-oxidizing atmosphere created by introducing super heated water vapor into an annealing furnace. In annealing furnaces at present in use, the non-oxidizing atmosphere treatment is limited to a single wire, annealing phase or zone as such. This treatment or atmosphere control is not applied to a preceding preheating phase or zone, generally kept at lower temperatures. However, preheating is effected at a temperature of about l50200C, the copper wire may be subjected to oxidizing in the preheating zone unless suitably protected. Moreover, if the wire is in contact with the external atmosphere, heat will be lost in an uncontrollable manner according to the temperature and moisture conditions of the environment and also according to the diameter and travelling speed of the wire. It is also known that, in the presently used annealing furnaces, after the proper annealing step, the wire being annealed is subjected to cooling in a cooling chamber containing water at room temperature.

The cooling chamber consists of a single unit. That is, it does not permit the efficacious cooling of the wire though operating in a counter-current mode, because the progressive heating of the water in the direction of the outlet of the chamber reduces the temperature gradient and therewith the efficiency of the cooling chamber as such. Another factor capable of reducing the efficiency of the cooling chamber is the possible formation of a vapor layer around the hot wire. The abovementioned inconvenienceis make it difficult to obtain a drawn wire which has good mechanical characteristics which are, in addition, rather difficult to control and regulate according to the materials the wire consists of.

SUMMARY OF THE INVENTION It is an object of the present process to obviate the above-mentioned inconveniences.

The technical problem here to be resolved consists in creating a possibility of efficaciously heating the wire to be annealed and to make sure that the wire, in the heating phase is not subjected to oxidation phenomena. It consists also in ensuring an efficacious cooling of the wire after the annealing step, so as to obtain a drawn wire possessing predetermined characteristics of a constant or uniform nature.

The above-mentioned technical problem has been resolved by means of the annealing furnace. according to the present invention in that one side thereof comprises means for preheating in a closed space and, on the other side, means for extending the cooling phase, increasing in this manner the overall efficiency of the furnace. The furnace is, therefore, an annealing furnace of the continuous type, for metal-wire drawing machines, comprising a plurality of pulleys for advancing the drawn wire. The furance has a unit for the supply of a non-oxidizing fluid, such as superheated steam, connected to an annealing chamber for the drawn wire,

and has a cooling unit for the drawn wire positioned at the outlet of the annealing chamber. The furnace is provided with means designed to introduce into the cooling unit a coolant. The preheating chamber for drawn wire is connected to the non-oxidizing fluid supply unit and communicates with the annealing chamber of the drawn wire. The cooling chamber or unit for the annealed wire is formed by a plurality of independent, cooling chambers, each connected directly and independently one of the other, with the means to introduce the coolant. Each cooling chamber is provided with an outlet opening for the coolant.

BRIEF DESCRIPTION OF THE DRAWINGS The characteristics of the present process will be still more evident from the following description, given by way of example, without being limited thereto, and the attached drawings, in which:

FIG. 1 is a schematic longitudinal cross-section view of an annealing furnace according to the present invention;

FIG. 2 is a cross-section view taken along section line 11- of FIG. 1 on an enlarged scale;

FIG. 3 is an enlarged longitudinal cross-section view of one of the drawing pulleys, showing the details of the cooling element of the said pulley described hereinafter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With particular reference to FIGS. 1 and 2, it is seen that the annealing furnace according to the present process comprises a frame 10 provided with an inside wall 11 constructed for carrying a plurality of driven pulleys, 13-19, to be described hereinafter, for the drawing of the wire to be annealed. FIG. 2 illustrates in detail the pulleys relative positions provided for drawing the wire 12. The pulleys are arranged in part in an upper part of the furnace, in particular the upper pulleys l3, 15, 17 and 19, and in part in a lower part of the furnace, and in particular the

lower pulleys

14, 16 and 18.

The annealing furnace comprises a preheating chamber 20 defined by the inner wall 11 and a front cover 21'of the annealing furnace as such. The

drawing pulleys

13, 14, 15, 16 and 17 are arranged inside of the preheating chamber 20, while two of the

pulleys

18 and 19 are outside of the chamber and are in a drying zone (these pulleys may also be omitted).

Referring to the FIG. 2, it can be seen that, inside of the preheating chamber 20, there is arranged an annealing chamber 22 connected, by means of ducts 23, to a non-oxidizing fluid supply unit which supplies, for example superheated steam. The steam supply unit, being known as such, is not shown. The annealing chamber 22 is provided with an inlet and an outlet opening for the wire 12 and an opening 24 connecting it to the preheating chamber 20, so that the nonoxidizing fluid will enter also into the preheating chamber 20. According to a variation of the present invention, the preheating chamber 20 may be independently connected to the non-oxidizing fluid supply unit. It is, however, a main object of the present process that the preheating chamber 20 receives the non-oxidizing fluid: in one case, through the annealing chamber 22 and in the other case by means of separate ducts directly from the relative supply unit.

The preheating chamber and the annealing chamber 22 are placed on top of a tank 25 for collecting the water from the condensed steam and also cooling water as described hereinafter. The tank 25, in turn, is in direct communication with a tank 26 thereunder. A pump 27 is connected to the tank 26, and draws the cooling water therefrom to return it into the cooling cycle by means of conduits or

pipes

28 and 29, to cool the wire 12 and the drawing pulley at the outlet of the annealing chamber 22, described hereinafter.

As shown in FIG. 2, between the outlet of the annealing chamber 22 and the pulley 16 drawing the wire 12, immediately positioned after the outlet of the chamber 22, is a first cooling chamber 30 for the annealed wire 12. Additional cooling chambers 31, separated one from the other and also from the chamber 30, are arranged after the pulley 16, downstream from the latter in the direction of travel of the wire 12 as indicated by an arrow F. The cooling chambers 30 and 31 are provided with inlet and outlet openings or wire guides 44, 45 for the wire 12 to be cooled and are connected to the conduit or pipe 28 supplying cooling water to the cooling chambers 30, 31 which flows from the chambers through the inlet and outlet openings or wire guides 44, 45 for the wire 12, and is then collected in the tank 25 and then flows into the tank 26 thereunder to be cooled and returned to the cooling cycle.

The cooling chambers 31 are disposed substantially vertically and arranged so that the wire guides 44,45 are disposed colinearly so that the direction of advance of the metallic wire 12 is substantially vertical. As the cooling water flows downwardly out of the wire guides 44 and upwardly out of wire guides 45 it flows over a surface of the advancing metallic wire 12 in the direction of advance of the wire 12 and in counter flow to the direction of advance of the wire. When the two opposed flows collide turbulence is induced in the water and the turbulent water impinges on a surface of the wire 12.

If, the wire 12 is sufficiently hot when it advances through one of the cooling chambers 31, a vapor layer will form in the water at the surface of the hot wire 12. Heat transfer through the vapor layer is less than through the water, so that the efficiency of the cooling chamber 31 will be reduced. The turbulent water, impinges on the surface of the wire 12, dispreses any vapor at the surface of the wire 12, so as the wire enters a next cooling chamber 31, its surface is in contact with water, and cooling of the wire by the cooling chamber is maximal.

The copper wire 12 is annealed as follows: The wire 12, enters the preheating chamber 20 (FIG. 2) from above and is first wound onto the first upper drawing pulley l3, kept at a negative potential V then around the first lower pulley 14 which is electrically insulated, and then moves upward to be wound around the second top pulley 15, which is kept at a first positive potential V passes through the annealing chamber 22, then through the first cooling chamber 30, is taken up by the second bottom pulley 16, kept at a negative potential V moves again to the top and passes through the cooling chamber 31 and is taken up by the electrically insulated pulley 17, it leaves the preheating chamber 20, to be taken up by the pulley 18 kept at a positive potential V, which is lower than that of the pulley 15 and, finally, is taken up by the end pulley 19, kept at a negative potential V, for reasons that will be explained hereinafter.

. The preheating and annealing of the wire are realized by means of Joule effect heating. In fact, in the preheating run between the

pulleys

13, 14, 15, the wire 12 is subjected to a first current raising its temperature to about l20-200C because of the electric resistance offered by the length of wire, through which the current passes, as well as due to a voltage difference existing between the

pulleys

13 and 15. correspondingly, in the annealing circuit of the wire in the chamber 22, that is, precisely, the run between the

pulleys

15 and 16, the wire 12 passes a second value or current higher than the first one. This run is shorter than the preceding one, and the temperature of the wire is brought up to, for example, between 550 and 600C for the annealing step.

At the outlet of the annealing chamber 22, the wire 12 is at once cooled to make sure that its temperature is not too high when in contact with the pulley 16, and is then still further cooled in the cooling chambers 31, where it is subjected to a most efficacious cooling system. in this cooling chamber system, all the cooling chambers are independent one from the other and are constantly supplied with water at the same temperature, that is, constantly filled with water and vapor, generated by the cooling of the wire.

Where the wire, after cooling, is to be dried, a third, relatively lower current is passed therethrough during a greater length of the last run, keeping the pulley 18 at a potential which is lower'than that of the preceding ones. As shown in FIG. 2, the drawing pulleys 13, 14, 15, 16, 17, 18, 19 are of the same diameter and are driven, as seen in FIG. 1, by a common electric motor vapor of steam therein. It will also be evident that the cooling step is much more efficient than in the single chamber cooling system until now in use, because in each cooling chamber 30 and 31, the wire 12'passes through a liquid, which is practically always at the same temperature with a noteworthy temperature gradient.

It is to be understood that the form and the arrangement of the preheating, annealing and cooling chamber as shown herein are set forth only by way of example, without the present invention being limited thereto. The form and arrangement shown may be varied without deviating from the above principle. As already mentioned hereinabove, the pulley 16, placed at the outlet of the annealing chamber 22, is the one most exposed to heat since it comes into contact with the wire 12, when the latter is still at a very high temperature. According to the present invention, this pulley 16 is cooled, because its cooling makes it possible to improve the cooling of the wire. it is evident that also the other pulleys may be cooled by using the same cooling system used for the pulley 16 and described hereinafter.

The cooling system is shown in FIG. 3 which is a diagrammatic crosssection view of the cooling pulley 16. The cooled pulley 16 comprises a disc 35 fixed, by means of screws 36, to a rotating shaft 37 rotatably mounted on the wall 11 of the frame 10. The disc 35 of the cooled pulley 16 carries on its outer periphery a ring 38, fixed thereto by means of screws 39, and is provided circumferentially with a peripheral V groove 40 for the wire 12 to be drawn.

The outer side of the disc 35 is provided, in addition, with a circumferential groove or recess 41 connected to an element or tongue 42 integrally fixed to the disc 35. The cone-shaped tongue 42 is surrounded by a tapered nozzle 43 suitably spaced from the said tongue 42 and connected to the pipe 29 supplying the cooling water. In this case the cooling water coming from the pipe 29 is deviated by the tongue 42 and distributed into the groove or recess 41 with the coolant being carried to the outside so that the pulley 16 is constantly cooled and kept at a temperature which is considerably lower than that of the wire 12 when leaving the annealing chamber, so that the structure of the pulley is not damaged thereby. It is evident that in an annealing surface according to the present process, the water vapor present in the chambers containing the pulleys is keeping the latter at a constant temperature, with the therefrom resulting constancy of the ohmic resistance thereof and constant coefficient of the heat exchange between the pulleys and the wire at anysoever speed condition. Variants and modifications can be applied to the annealing furnace without leaving the scope of the present pl'OCESS.

What I claim and desire to secure by letters patent is:

1. An annealing furnace for a wire-drawing machine comprising, means defining a preheating chamber for preheating a metallic wire in a non-oxidizing atmosphere, means defining an annealing chamber for annealing in a non-oxidizing atmosphere said wire immediately after preheating thereof, a cooling unit downstream of the annealing chamber to cool the annealed wire comprising a plurality of independent, series cooling chambers each having a pair of opposed wire guides through which the annealed wire advances serially therethrough, said series cooling guides being disposed substantially vertically and having said wire guides disposed colinearly for guiding said metallic wire in a sub stantially vertical direction of advance, said wire guides comprising outlet means for coolant flowing out of said series cooling chambers, said coolant flowing on a surface of said metalllic wire'in a direction of advance of said metallic wire and in counter flow to a direction of advance of said metallic wire thereby inducing turbulence in said coolant at a portion of a surface of said metallic wire between adjacent ones of said series cooling chambers, means for providing a coolant to each of the cooling chambers independently of each other, and means advancing the wire longitudinally through said preheating chamber, said annealing chamber and said cooling unit while simultaneously preheating the wire in said preheating chamber at a given temperature and heating it for annealing in said annealing chamber at a different temperature.

2, An annealing furnace for a wire-drawing machine according to claim 1, in which said annealing chamber is disposed in said preheating chamber.

3. An annealing furnace for a wire-drawing machine according to claim 1, in which said means advancing the wire longitudinally comprises a plurality of rotatably driven pulleys applying potentials to said wire at different lengths of a path of travel thereof to heat it at said given temperature for preheating it and at said different temperature for annealing it.

4. An annealing furnace for a wire-drawing machine according to claim 3, in which said driven pulleys comprise drawing pulleys disposed in said preheating chamber, and in which said annealing chamber is tubular and is disposed in said preheating chamber.

5. An annealing furnace for a wire-drawing machine according to claim 1, in which said means advancing the wire longitudinally comprises a plurality of rotatably driven pulleys, including pulleys for applying in operation potentials to said wire along different lengths of a path of travel thereof, one of said pulleys being disposed downstream of said annealing furnace and upstream of said cooling unit, and cooling means cooling said one pulley.

6. An annealing furnace for a wire-drawing machine according to claim 5, in which said cooling means comprises means for applying a cooling fluid to a side face of said one .pulley.

7. An annealing furnace for a wire drawing machine according to claim 5, wherein said one pulley has a generally conical tongue having a lateral surface centrally disposed on a face thereof and a circumferential recess disposed in said face of said one pulley about said tongue, and said cooling means cooling said one pulley comprises a conically diverging nozzle disposed adjacent to said conical tongue for delivering a flow of coolant to said lateral surface of said conical tongue.

Claims

1. An annealing furnace for a wire-drawing machine comprising, means defining a preheating chamber for preheating a metallic wire in a non-oxidizing atmosphere, means defining an annealing chamber for annealing in a non-oxidizing atmosphere said wire immediately after preheating thereof, a cooling unit downstream of the annealing chamber to cool the annealed wire comprising a plurality of independent, series cooling chambers each having a pair of opposed wire guides through which the annealed wire advances serially therethrough, said series cooling guides being disposed substantially vertically and having said wire guides disposed colinearly for guiding said metallic wire in a substantially vertical direction of advance, said wire guides comprising outlet means for coolant flowing out of said series cooling chambers, said coolant flowing on a surface of said metalllic wire in a direction of advance of said metallic wire and in counter flow to a direction of advance of said metallic wire thereby inducing turbulence in said coolant at a portion of a surface of said metallic wire between adjacent ones of said series cooling chambers, means for providing a coolant to each of the cooling chambers independently of each other, and means advancing the wire longitudinally through said preheating chamber, said annealing chamber and said cooling unit while simultaneously preheating the wire in said preheating chamber at a given temperature and heating it for annealing in said annealing chamber at a different temperature.

2. An annealing furnace for a wire-drawing machine according to claim 1, in which said annealing chamber is disposed in said preheating chamber.

6. An annealing furnace for a wire-drawing machine according to claim 5, in which said cooling means comprises means for applying a cooling fluid to a side face of said one pulley.