US2717776A - Apparatus for heat-treating wires - Google Patents

Description

Sept. 13, 1955 2 Sheets-Sheet 1 Filed Aug. 25 195] lld INVENTOR M A; RA VBURN ATTORNEY Sept. 13, 1955 v, A. RAYBURN 2,717,776

APPARATUS FOR HEAT-TREATING WIRES Filed Aug. 25, 1951 2 Sheets-Sheet 2 INVENT'OR l/ A. RA YBURN AT TURNS United States Patent 0 2,717,776 APPARATUS.EORHEAT-TREA'HNGsWIRES;

Vincent A. Rayburn, Ealtimore,.Md., assignor to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application August 25, 1951, Serial No.-243,701a

3 Claims. (Cl. 2663) This invention relates to apparatus for heat treating wires, and. moreparticularly toapparatus for heat .treating moving wires in a substantially oxygen-free atmos-- phere.

In: the manufacture ,of copper-clad. steel electrical con.-

doctors for eommunicationslines, asteel wirehaving.

high tensile strengtlrandlow elongation properties may be employed as a core,- and a relatively thick layer or" conductive copper may beformed upon this core. The.- copper layer may be formed uponthe steel coreby con-"- tinuously electrodepositing copperupon a steel wireh'aving th e desired characteristics. A suitable electroplating process may include analkaline bathinz-which a. flashcoat-ing oflcopper maybe deposited upon a, previously cleaned steel wire atlalow current density, and an. acid. bath inwhich a thick coating of copper may bedepositedr 3O oyrer the. flash coating at a high. current density. A heat treatment per-formed upon the coppenclad steel -Wire, afterthe, electr,od eposi tion of copper thereon: has been .cornpleted has been found toimprove. substantially ,the;de-.

siredcharacteristics ,of thecomposite product.

One desired elfect of a-heat treatment of the composite. wire-is to recrystalize the electrodeposited copper. A microscopicv examination of a .section 1 of the originally. deposited thick copper layer would reveal. a fine grained.

structureof metal built up in juxtaposedtradial columns. During the electrodeposition process, the atoms of. copper are depositedone on ,-top,-of another, chain fashion, to create this columnar structure; If a composite wire 'having such-an untreated columnar copper structure .swere flexed, the radial =columns-would separate readily, and cracks Wouldappear inthe structure. This would .greatly l decrease the electrical conductivity of ;the ,wire andperhapsallow-moisture to reach, the :steel corepto cause-corrosion. Before the heat treatment,strains may. existiin's the electrodeposited copper due to inter-molecularstresses ductility elongation, and electrical conductivity.

Another, desiredeifect of aheattreatmenbof the com: posite wire, is to temper the, steel core toincreaseits elasr ticity without appreciably afiectingtits tensile strength.

Itis'preferred to employ atype of steel wire knowninthetrade as improved plow steel wire. Such'wire possesses high carbon content, and is treatedat. the steel mill to develop high'tensile strength. The original ability of the wire to becoine elongated maybe increased by the tempering heat treatment from about 1.5% to about 5.5% to 3 6%. When embodied in an outside,-suspend-ed conductor, such as an overhead transmission line, such a conductor is capable of sagging under a load, such as ice, withoutpermanent deformatiomand returning to its normal length T when the load is removed.

In the tempgningoperation the wire. could be-heated;

in a variety of ways. For example, the wire could be adice vancedthroughamol'ten'salt bath, a heated oven or a flame, wiper. However, it is preferred to heat the wire by passingan;alternating.currenttthrough a short section of the wire at the completion of the copper plating step. Obviously," itflS necessary. to control the atmosphere about the wire. while it isbeingheated to prevent undesirable oxidation from occurring. At least, any degree of oxidation wliich might inevitably occur must be held to a practical'minimum.

Apparatusheretofore available for carrying out such preferred heat treatmentshas not been entirely satisfactory. The wire'under treatment has been relatively inaccessible for necessary insertion and adjustment, because kL.C1'OSd systemiprovidedwith mechanical seals has been used; Moreover, theiequipment has been bulky, costly, and not readily susceptible to disassembly. These disadvantages of the prior art apparatus-become magnified whenit is desired -to treat a multiplicity of wires simultaneousl-yinone unit of equipment.

An object of the invention is to provide new and improved apparatus for heat'treating wires.

Another object-of the invention is to provide new and improved. apparatus for heat treating moving Wires in a substantially oxygen-free atmosphere.

An apparatus illustrating certain features of the-invention: may include an elongated, hollow mufile for maintaining a substantially oxygen-free atmosphere envelopinga length' of wife, said mufile being open at both ends so that a length of wire may be advanced therethrough and'having a-coextensive longitudinal slot extending into the muflie from the outside atmosphere so that the wire may 'be readily inserted and removed transversely of the mufil.-

A complete understanding of the invention may be had fromwthe following detailed description of heat treating apparatus forming a 'specificembodiment thereof, when read in conjunction with the appended drawings, in

Figl'is a plan view-ofaheat treating apparatus embodying the invention;

Fig. 2 is*-an:.enla'rged section taken along line 2-2 of Fig.-l;-

Fig. 3 is an enlarged section taken along line 3-3 Fig. 4 is an enlarged planview of a portion of the apparatus-shown in- Fig. 1;

Fig. 5 is a corresponding side elevation of the apparatus shown in Fig. 4, and

Fig'.=6-is aperspective view of the apparatus shown in Figs=-4 and 5.

Referring now in detail to the drawings, a plurality of conductive wires -10 l0, each comprising a composite copper-clad steel core, are shown emerging from a water rinse bath 11 at the completion of a manufacturing operation in' which the copper has been electrodeposited upon steel wires being advanced through the apparatus. The wires 1010'are continuously advanced in side by side parallel relationship, and as many as twenty-five 0; more wires may be simultaneously treated in this manner. From the water rinse bath-lLthe wires 10-10 are advanced through a heat treating unit 12 to another ap. paratus unit 13 in which additional manufacturing operations' may "subsequently be performed. A tempering Operatiorrisperformed on the wires in the heat treating unit which includes heating the moving wires to a point below the criticaltemperature in a controlled atmosphere, and then immediately'cooling the wires without quenching th'em'.

In passing through the heat treating unit 12, the wires 1010 advance beneath an upper contact roll 14 having circumferential grooves 15-15 for receiving the wires. The wires then pass above a lower guide roll 16 having similar grooves 17-17, which are aligned with the grooves -15, and then beneath a second upper contact roll 18 having similar aligned grooves 19-19. At the opposite end of the heat treating unit 12, there is provided a similar set of rolls including an upper contact roll 21 having grooves 22-22, a lower roll 23 having grooves 24-24, and another upper contact roll 25 having grooves 26--26.

In travelling the length of the heat treating unit 12, the wires 10-10 lie in a generally horizontal plane. The axes of the upper rolls are positioned above this plane and the axes of the lower rolls are positioned below it, yet the peripheries of each of teh rolls protrude slightly over the plane, in the manner shown in Fig. 3. Thus, in alternately passing under one roll and over a subse quent roll, the path of the wires will be somewhat sinusoidal. Good contact between the rolls and the wires will be obtained in this manner, because the wires are under some tension in the water rinse bath 11 and in the subesquently entered apparatus unit 13.

The rolls 14, 18, 21 and 25 electrically contact the wires 10-10, and in cooperation with the lower rolls 16 and 23 positively drive these wires to advance them through the apparatus. The lower roll 16 is secured to a rotatable shaft 27 having a gear 28 and a sprocket 29 mounted on one end thereof, and the upper rolls 14 and 18 are attached to rotatable shafts 30 and 32, respectively. Secured at one end of the shafts 30 and 32 are gears 33 and 34, which mesh with and are driven in the same direction by the oppositely rotating gear 28. The size relationship of the gears 28, 33 and 34 is such that the rolls 14, 16 and 18 are rotated at equal peripheral speeds as they engage and advance the wires 10-10.

An endless chain 35 engages the sprocket 29 and drives a sprocket 36 secured to one end of a rotatableshaft 37 to which the roll 23 and a gear 38 are attached. Gears 39 and 40 mounted on rotatable shafts 41 and 42, respectively, upon which the rolls 21 and 25 are also secured, mesh with and are driven in the same direction by the oppositely rotating gear 38. Hence, the upper rolls 21 and 25 are rotated in one direction and the lower roll 23 is rotated in the opposite direction to advance the wires 10-10 toward the apparatus unit 13. The shafts 27, 30, 32, 37, 41 and 42 are journalled upon a frame 43 of the heat treating unit 12, and are powered by. a motor 44 driving through a speed reduction unit 45 connected to the shaft 27.

The sections of the wires 10-10 which extend between the sets of contact rolls at opposite ends of the heat treating unit 12 are heated by passing an alternating current therethrough. One side of a transformer 46 is connected to a pair of power lines 47 and 48, and current is transmitted from the other side of the transformer 46 to the contact rolls 14 and 18 by a connecting line 49 and a plurality of contact brushes 50-50. The circuit is completed through the wires 10-10 and the contact rolls 21 and 25 back to the transformer 46 by contact brushes 52-52 and a connecting line 53. s

A mufiie 54, located between the two sets of rolls in the heat treating unit 12, is provided with a plurality of longitudinal, central passageways 55-55 through which the wires 10-10 may travel from one set of rolls to the other during the heat treatment. The mufile 54 is assembled from a plurality of identical, elongated segments 5 6-56, each having an indentation 57 at the base of one side and end thereof and a matching foot 58 protruding from the opposite side and end so that the segments 56-56 may be keyed together. It may be observed from Figs. 4, 5 and 6 that the indentation 57 and the foot 58 of a segment 56 each run continuously along one half of the perimeter of the base of the segment. These segments are composed of a vitreous ceramic material, such as zirconium oxide or aluminum oxide, which is not readily affected by heat or moisture.

While the segments 56-56 could be made coextensive in length with the mufile 54, it is preferred to employ short segments joined together end to end. A long segment would be less convenient to manufacture, it would disrupt the alignment of the assembled apparatus to a greater degree if warping occurred, and it would be more expensive to replace in case of damage. A plurality of short segments may be interlocked in a regular pattern in the assembled muffle, as is illustrated in Fig. 1. The end to end joints in one longitudinal column of segments may be placed at the midpoints of segments in adjacent longitudinal columns, and half segments may be placed at the opposite ends of alternate columns to make the length of each of the columns equal. In this manner, any lack of uniformity in the segments may be compensated.

At about midway up the longitudinal sides of the segments 56-56 there are provided longitudinal recesses 59-59 designed to meet and form the central passageways 55-55 when the segments 56-56 are keyed together. In transverse section these passageways appear rectangular with rounded corners. The segments 56-56 are also cut away in vertical planes from the recesses 59-59 to the upper surfaces of the segments so that vertical coextensive slots 60-60 are formed when the segments are assembled. The width of each slot 60 is just sufficient to provide clearance for a wire 10 as the wire is dropped through a slot 60 parallel to the longi-- tudinal axis thereof and into a passageway 55 in the mufiie when the apparatus is being prepared for operation.

The assembled segments 56-56 rest upon a support 62 having a pair of vertical arms 63 and 64 on opposite sides thereof. The arm 63 is provided with a fixed horizontal projection 65 having a rounded flange 66 fixed on the end thereof and designed to fit into a recess 59 in an outermost segment 56 ofthe muifie 54, thereby functioning as a fixed clamping jaw. The arm 64 is provided with a plurality of horizontally adjustable screws 67-67 having caps, of which a cap 68 is shown, rotatably secured to the ends of the screws and designed to fit into a recess 59 of an outermost segment 56. Each screw 67 may rotate within its cap 68 as the screw is adjusted horizontally and thereby prevent damage to the segment 56 contacted thereby. These screws and caps, in conjunction with the vertical arm 64, function as adjustable clamping jaws to hold the assembled segments 56-56 together. The arm 63 is provided with a fixed horizontal projection 69 designed to fit into the indentation 57 of the outermost segment on one side of the assembled mufile, and the arm 64 is provided with a projection 70 designed to fit over the foot 58 of the outermost segment on the other side of the muffie.

The number of segments 56-56 held on the support 62 may be varied to correspond with the number of wires 10-10 being treated. For this purpose, the vertical arm 63 may be selectively secured to the support 62 in one of a plurality of positions equally spaced apart a distance corresponding with the width of a segment 56. A plurality of apertures 71-71 in the support 62 are properly spaced to demark these positions. The vertical arm 63 may be secured in one of these positions by a depending bolt 72 which may be extended through a selected aperture 71 and be engaged by a nut 73.

Since the set of rolls 14, 16 and 18 at the entrance end of the mufiie 54 are driven at the same speed as the set of rolls 21, 23 and 25 at the exit end of the muffie, the heated portions of the advancing wires 10-10 in the mufile will not be under tension. It is important to avoid tensioning the heated portions of the wires, in order to prevent stretching thereof. If these wires were stretched while being heated, permanent nonuniform deformation could result with attendant nonuniform conductivity. In the communications lines into which this product is intended to be ultimately incorporated, the conductivity of the wires must be of a constant predetermined value.

Operation The composite copper-clad steel wires -10, formed by previously advancing a plurality of high tensile strength steel wires through copper electroplating apparatus (not shown),"on emerging from the Water rinse bath 11, are.

advanced through the heat treating unit 12 to the apparatus unit 13, in which subsequent manufacturing steps maybe performed. The Wires 10-10 traverse a generally horizontal path through the heat treating unit 12, but in that' portion of the unit 12 in which the wires pass under the upper roll 14, over the lower roll 16, and then under the upper roll 18, the path of the wires will appear somewhat sinusoidal. Similarly, in that portion offthe' apparatus in which, the wires pass between the upper 'roll 21 the lower roll 23 and the upper roll 25, thepath of the wires 10-10 will also alternately deviate slightlyf'from horizontal. This staggered arrangement of the rolls, while'the wires 10-10 'are under some tension in the bath 11 and in'the apparatus unit 13, enables the driven rolls to grip the wires positively and advance them throughjhe apparatus. Yet, since the sets of rolls at opposit'e'endso'f thelmufile sql areidr iven at the same speed, the portionsof the wires which extend between the two sets of rolls will .not be under tension. Thus, objectibn'al stretching of thewires while they are heated will be prevented.

Eachwire 10 isheated in the portion of the wire which extends between the .two sets of rolls in the heat treating apparatus 12,. by passing an alternating current through this portion of the wire. Current is transmitted from the transformer 46 through the connecting line 49 and the contact brushes 50-50 to the driving rolls 14 and 18, and the circuit through the wires 10-10 is completed by the driving rolls 21 and 25, the contact brushes 52- 52, and the connecting line 53. Substantially the entire heated portions of the wires 10-10 are enclosed within the mufile 54, and travel through the longitudinal passageways 55-55 formed between each of the identical, ceramic segments 56-56 when these segments of the muffle are keyed together.

The primary purpose of the muifie 54 is to maintain the heated portions of the wires 10-10 enveloped in a substantially oxygen-free atmosphere, to prevent undesirable oxidation of the heated wires from occurring. Since at least a trace of oxygen may exist in any atmosphere of steam generated by conventional means, it is perhaps more accurate to state that the present invention is effective to limit the degree of oxidation of the heated wires to a practical minimum. For this purpose, the passageways 55-55 in the muifle 54 are kept filled with steam under low pressure, which is generated by vaporizing the water which clings to the Wires as they emerge from the water rinse bath 11. The Wet wires do not become sufficiently heated to vaporize this coating of residual water until the wires have traveled a short distance into the passageways 55-55 in the muflle 54. Since the wires are traveling at a high rate of speed, and since the process of treating the wires is continuous, the steam will permeate every portion of the passageways 55-55 to exclude oxygen laden air therefrom.

When this system is operating properly, the pressure of the steam can be adequately maintained merely by vaporizing the residual water clinging to the moving wires in the manner described. However, it may be found desirable at times to be able to utilize an auxiliary source of steam to supplement the supply being generated by vaporization of the residual water. A plurality of steam jets (not shown) connected to such auxiliary source of steam, could be properly positioned to feed steam into the passageways 55-55 in the muffie 54 on such occasions.

Some of the steam in the passageways 55-55 will escape to the outer atmosphere through the vertical slots 60-60. The rate at which such steam escapes is insufiicient to permit oxygen containing air to enter the slots' and reaching the heated wires without depleting-the supply of steam. necessary to fill the passageways 55-55. However, very little steam will escape in this mannerbe cause the slots 60-60 are relatively deep, and the width of each slot60 is small. These slots are provided to allow the wires 10-10 to be insertedand strung through the; apparatus easily, and the width of each slot'60 is limited to a size barely sufficient to provide clearance for a wire 10 during this preparatory stringing operation.

The tempering operation performed on the wires 10-10 in this apparatus includes thesteps of heating; the: wiresto a point below the critical'temperat ure of the, steel, and immediately cooling the wires without quench ing them. In the present instance, the wires are cooled: in air while they travel from the heat treating unit 12; to the apparatus unit 13. The speed of the moving wires; is so correlated to the rate at which it is possiblefor'th em to cool, that the wires reach the apparatus unit 13 at ambient room temperature. If the natural c ooling, rate, ofwires being treated were not adaptable to this purpose, by reason of a different chemical composition or a dif ferent thickness of the wires, it might bein ecessary to in corporate supplementary cooling devices into ,the ap;

paratus.

' The simplified structure embodied in the invention is a distinct improvement over the cumbersome prior art de-Q vices, which were generally closed systems requiring, me-, chanical seals for the wires. The muffle 54provides 'a substantially oxygen-free atmosphere in an open systemhaving vapor seals for the heated portions of the wires being treated. The insertion and stringing of wires through the apparatus is greatly facilitated, and ready access to the wires may be had at all times. Since each of the ceramic segments 56-56 is identical, these elements are interchangeable and manufacturing and replacement problems are thereby reduced. Obviously, such a mufile can be readily assembled and disassembled, and the number of segments employed in the mufile can be varied to correspond with the number of wires being heat treated.

Although the invention has been described with reference to the manufacture of copper-clad steel electrical conductors, it is manifest that the invention could be adopted advantageously for any other manufacturing program in which it may be desirable to heat treat moving wires in a substantially oxygen-free atmosphere.

What is claimed is:

l. A segmental mufiie for maintaining a substantially oxygen-free atmosphere through which a plurality of spaced parallel wires are advanced during a heat treatment thereof, which comprises a plurality of identical longitudinal ceramic segments positioned in a regular pattern in side by side and end to end relationship to form the muffle, each segment having at the base of one side and of one end a coextensive indentation and having at the base of the opposite side and end thereof a protruding foot matching the indentation so that the plurality of segments interlock in the assembled mufile, each segment also having on its longitudinal sides coextensive longitudinal recesses and vertically cutaway portions extending from the recesses to the top of the segment so that the recesses on adjacent segments meet and form a plurality of spaced passageways in which the wires travel through the mufiie and the vertically cutaway portions on the adjoining sides of the segments form narrow, spaced, parallel, vertical slots extending from the passageways to the outside atmosphere at the top of the muifle and through which the wires may be inserted transversely into the passageways, and a clamp for securing the assembled segments together, said clamp being adjustable so that the number of segments assembled may be varied to change the size of the muflle.

2. A segmental muffle for providing a substantially oxygen-free atmosphere of low pressure steam through which a plurality of spaced parallel wires are advanced during a heat treatment thereof, which comprises a plurality of identical ceramic segments assembled in a series of abutting endwise columns and sidewise rows having a uniform pattern, each of said segments being an elongated, generally rectangular block having at the base thereof an indentation extending continuously along the entire length of one side and of one end and having at the base of the opposite side and end a continuous protruding foot which matches the shape of said indentation, each foot being designed to key into the indentation on the side of an adjacent segment and the indentation on the end of another adjacent segment to interlock the assembled, segments in side by side and end to end relationship, each segment also having on its sides coextensive longitudinal recesses and having vertically cutaway portions extending from the recesses to the top of the segment, so that the adjacent recesses on the adjoining sides of the segments cooperate to form spaced passageways in which the wires travel through the muflle and the cutaway portions on the adjoining sides of the segments cooperate to form a plurality of vertical slots extending the entire length of the muflie and from the pasageways to the outside atmosphere at the top of tthe muifle, each of said slots having a width only slightly greater than the diameterof one of the wires treated so that the clearance is just suflicient to allow the wire to be moved through the'slot while substantially preventing the outside atmosphere from entering.

:3. A mufile segment, which comprises an elongated,

generally rectangular, ceramic block having at the base thereof an indentation extending continuously along the entire length of one side and of one end andhaving at the base of the opposite side and end a continuous protruding foot which matches the shape of said indentation, said block also having a coextensive longitudinal recess located at about the midpoint of each of its sides and having vertically cutaway portions extending from the recesses to the top of the block along its entire length, said segment being designed to interlock by means of its foot and its indentation with a plurality of other identical segments in abutting endwise and sidewise relationship to form a mutfie assembly having a plurality of spaced parallel passageways extending longitudinally therethrough and having a plurality of vertical slots extending from the passageways to the outside atmosphere at the top of the muffie, said passageways and said slots being formed by the meeting of pairs of the recesses and of the vertically cutaway portions on the adjoining sides of adjacent segments in the mufile assembly.

References Cited in the file of this patent UNITED STATES PATENTS 323,087 Thornton July 28, 1885 1,147,731 Ingraham July 27, 1915 1,362,367 Talley Dec. 14, 1920 1,533,491 Wright Apr. 14, 1925 2,187,785 Hoyt Jan. 23, 1940 2,300,329 Wood Oct. 27, 1942

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