US2656283A - Method of plating wire - Google Patents

Description

Oct. 20, 1953 A. o. PINK ETAL METHOD OF PLATING WIRE Filed-Aug; 51. 1949 mvgm'ons ALBERT O. FINK ALFRED E. BISHOP BY W 6 2.2%

ATTORNEYS Patented Oct. 20, 1953 UNITED STATES METHOD OF PLATING WIRE Albert 0. Fink and Alfred E. Bishop, Dayton, Ohio, assignors to The Commonwealth Engineering Company of Ohio, Dayton, Ohio, a corporation of Ohio Application August 31, 1949, Serial No. 113,438

' 6 Claims. l This invention relates to the art of the deposition of metals. More particularly, it relates to the plating of metals on continuously moving wire and the apparatus for carrying out the process.

Deposition of thin films of protective metal such ,asnickel, cobalt, tungsten and metal alloys upon stationary objects has beenaccomplished inthe past by enclosing an object to be plated in a chamber, charging the chamber f with, a decomposable metal-bearing gas and heating the object to the decomposition temperature for said gas.

In the only process of which applicants have knowledge wherein an object is moved in the plating zone, the material is thin metal sheet. This fiat material is brought to the gas decomposition temperature by resistance heaters placed adjacent the underside of the sheet.

The upper side of the sheet is exposed to the decomposable gases.

This metal sheet is brought into and out of the plating chamber by passing the sheet through a water bath which actsas a seal for the gas chamber.

' Thus, the plating of wire presents two major problems, heating the wire and sealing the chamber against leakage of poisonous gases while continuously passing the wire through the chamber, for which the earlier processes one no solution. 7 I v It is anobject of this invention to overcome the disadvantages and limitations of the processes known heretofore.

It is also an object of thisinvention to provide a continuous process for plating wire.

It is a further object of this invention to provide small compact apparatus of high wire plating capacity.

It is another object of this invention to provide a process wherein wire is preliminarily r:

coated, heat treated for increased adhesion, and given a finish plating in succeeding steps without a time lag therebetween.

It is also an object of the present invention to provide apparatus for rapid passage of the wire therethrough.

It is still a further object of this invention to provide apparatus having provision for conducting electricity to wire so that the wire will heat due to its own internal resistance.

-.:-;- ductiliy anneal. Neither of these systems is commercially It is also an object of the present invention to provide apparatus having a non-arcing seal for inlet and outlet from the equipment.

Another object of the present invention is to provide apparatus having a single chamber divided into segments by simple divider mechanism which in conjunction with control of gas pressures seals the apparatus against leakage of plating gas.

Other and more specific objects and advantages will be apparent to one skilled in the'art as the following description proceeds.

The wire plating in its simplest form as' carried out in accordance with this invention comprises running the wire through a tubular unit of relatively small diameter partitioned into segments or compartments.

Wire enters the tubular unit through a fluid, non-wetting, non-arcing seal. The tubular unit may be constructed of material which is a nonconductor of electricity or insulated from conducting portions.

In sequence, the wire is subjected to a cleaning anneal or heating, coating with metal and The plating operation may be divided into a preliminary flash coating with metal and a finish plating operation in which event an adhesion anneal or heating is interspersed between the two coating operations.

One of the factors important to the successful operation of the apparatus is control of gas pressure in each of the segments of the tubular unit. In order to insure against leakage of plating gases from the plating chamber or chambers and still have openings in the partition walls for continuous passage of wire, it is necessary to maintain a metal-vapor free gas atmosphere at a slightly higher gas pressure in the unit segments or compartments preceding and succeeding the plating chamber The leakage of inert gas into a plating chamber is limited to small quantities by having apertures in the partition wall of a diameter providing only a loose sliding fit with the wire passing therethrough and by keeping the pressure .differential small.

It will be recognized that the inert gas leaking into the plating chamber is not a harmful operation because the metal-bearing gases are usually diluted with an inert gaseous medium and the gas decomposing reaction in the plating chamber produces relatively inert decomposition products such as carbonmonoxide.

In the process a stream of gaseous material is brought into contact with hot wire. .The gaseous atmosphere may be formed by mixing an inert gas with the vapors of a volatile metal compound or by atomizing a liquid metal compound into a blast of hot inert gas or other equivalent method.

Carbon dioxide, helium, nitrogen, hydrogen, the gaseous product of controlled burning of hydrocarbon gases free of oxygen, and the like, have been utilized as a carrier medium or inert gas medium.

In some instances the use of hydrogen is preferred, as for example, in the cleaning anneal chamber where its ability meet as fa-reducin'g agent may be put to advantage to 'remove the oxide film or rust from iron wire.

Metals to be deposited may be introduced as gaseous metal carbonyls or waporizedsolutions of certain of the metal carbonyls in readily vaporizable solvents (for example, petroleum ether), also nitroxyl compounds, nitrosyl carbonyls, metal .hydrides, metal alkyls, metal halides, and the like.

Illustrative -compo.unds of the carbonyl type are nickel, .iron,rchromium, molybdenum, cobalt, and mixed carbonyls illustrative compounds of other'groups are the nitroxyls, such asxcopper nitroxyl; ,nitrosyl carbonyls, for example, cobalt nitrosyl carbonyl; hydrides, such as antimony hydride, tin hydride; metal alkyls, such as-chromyl chloride; and carbonyl halogens, for example. osmium carbonyl bromide, ruthenium carbonyl chloride, and the like.

Each material from which a .metal may be plated hasa temperature-at whch decomposition iscomplete. However decomposition may take place slowly at a lower temperature or while the vapors are being raised in temperature through some particular range. For example, nickel carbonyl completely decomposes at a temperature .initherange .-of 375 F. to 400 F. However, nickel carbonyl starts to decompose slowly at about 11 7 5" F. and therefore decompostion continues during the time of heating from 200",l to 380 F.

-"A large number of the metal carbonyls and hydrides may be effectively and efiiciently :decomposed at a temperature .in the range of 350 F. to 450. F. When working with most metal carbonyls weprefer ,to operatein a temperature range of from 375 F. to 425 F.

in order to deposit coatingsnon .the wire, it is necessary that the wire be .at a temperature in the general decomposition range of the volatilecompounds.

If the wire is, .for example, hot .drawn wire, I

the hot wire upon @cooling to the plating temperature range may be .led directly to plating chambers ..of the hereinafter described apparatus, with or without an annealing stage therebetween. If .an anneal is desired, the operation within .the apparatus may be carried out in a manner similar to that used when starting with coldwire,

Cold wire is raised to and maintained at desired temperatures by causing the wire to conduct electricity or by induction heating.

The voltage required will vary depending upon the type of wire. Iron wire, for example, heats to a plating temperature with a lower voltage or lower frequency than, for example, copper wire.

When annealing temperatures, which are considerably higher than plating temperatures, i. e., in the range of 800 F. to 1200 F., are to be used the operation generally consists of impressing upon terminals contacting the wire a voltagesufiicient to bring the wire to a red heat.

The lower temperature of the plating area is then accomplished by placing an electrical shunt in parallel with the plating zone. In this way the amount of current passing.- in'the wire in the plating zone is reduced and'as a result its temperature quickly reduces to a desirable range.

Preparatory to coating the wire the metallic material may be cleaned by employing conventional methods used in the art, comprising .electro-chemically cleaning by moving the same through :.a bath of alkali or acid electrolyte wherein the wire is made the cathode or anode.

Pickling of the'metal with hydrochloric, sulfuric or nitric-acid, or a combination of acids may also be made as a part of the cleaning process and the wire thoroughly rinsed or washed prior to introduction into the plating apparatus.

However, if the wire is in goodcondition a' cleaning "anneal may suflice, in 'which event the wire may be .heated just prior to entering the plating chamber.

vIn :a cleaning anneal any grease and the like will :be burned :away by bringing the wire to redheat.

The invention will be more clearly understood from the following description of one embodiment of the apparatus .andits mode of operation.

In the drawings:

Figure 1 is a diagrammatioillustration of a completeplating unit;

Figure 2 is an enlarged sectional "view 'dia grammatically showing the seal used at either the inlet or outlet end of :the tu'buiarztmit; and

Figure 3' is a sectional view diagrammatically illustrating the partition :unit separating .the tubular unit into segments.

Referring to Figure 1, thereis shown a base HI upon which is mounted :a .tubular 'unit ll composed offive sections 1.2 .to =lfisupported'by holderbrackets- I! which in the instant illustration are set to support partition units .1 8 dividing unit -H into sections or compartments.

Wire to be plated is mounted on :a spool :or reel 19 and enters unit. H through a seal 20, passes through the partition units ill and is drawn out through a seal 2| of construction similar to seal 20.

Plated wire is wound-on a spool 22 driven by suitable power means 23 such as electric motor.

Seal .20 is more fully illustrated in Figure 2. Seal20 consists of :a base cup :25 of material which is preferably a=non=electricalconductor. This cup is adapted to :be substantially filled with a fluid, such as mercury, low melting point eutectic fusible alloys, or equivalent fluid. Mounted on the base cup 25 is a support 26. Support 26 carries three small pulleys"21, 28 and 29 mounted on ball bearings "for free action.

Support '26 is composed of a vertical section 30 bored as at 3| and'ad'apted to extend into the mercury bath. .Head section '32 of support 25 is bored as at 33. Bore 33 is adapted at the lip 34 to receive a partition-element 18 to be described later in detail and has an enlarged portion 35 adapted as a chamber in which the pulley.21 is enclosed.

Partition element [-8 is preferably of conducting .metal and consists of a block 40 which is horizontally bored in a leftwardly direction as at 4| and parallel thereto in a :rightwardly direction .as at 42.

Bore 42 is tapered as at 43 and ends in a small diameter aperture 44 in the rightwardly wall of block 40. Below and. adjacent the aperture 44,

block 40 is provided with an extension 45 adapted to support a mercury contact 46 for use when the wire is to be a conductor.

Bore 42 is provided with a port 41 whose axis is disposed at 90 to the axis of the bore in the Wall block'40, which is of the same diameter as bore 42 and adapted to receive a tubular member.

Bore 4| is provided with a port 49 whose axis is disposed at 90 to the axis of the bore adapted to receive a tubular member.

An electrical conductor 50 is joined to the block 40 by suitable means 5|, such as welding, screws and the like.

When unit I8 is used as an end piece, a tubular member 48 is provided for bore 42 and port 41 is closed by suitable means. I

Tubular member 48 is adapted for gas tight engagement with seal 20 through suitable means 53 such as a gasket.

The unit I8 is joined to a tubular section, for example section [2, through flexible tube means 54.

When unit [8 is used as an intermediate connector, tubular member 48 is positioned in port 41 and flexible tube means 55 is provided forming a gas tight seal between unit [8 and, for example, tubular section l3.

In brief, the operation of the apparatus is as follows:

Wire on the reel I5 moves through seal 20 by passing over pulley 29 and down through the mercury. The wire turns upward after passing below pulley 28 and passes over pulley 21. The wire then traverses tubular member 48 and bore 42 and passes through aperture 44. The wire is energized by meeting the mercury contact 46. The wire passes through tubular unit H and its partition elements 18 until it emerges through the outlet seal 2|. The coated wire is then accumulated on reel 22.

Gas flow in this apparatus is counter-current to the direction of travel of the wire in each compartment.

Further, the gas in each compartment may be fed from separate systems, or, under certain circumstances, the plating compartments I3 and [5 may be connected in series and chambers l2, l4 and I6 connected in series.

Accordingly, each chamber receives gas through tubular member 49a depending from partition element I and is removed through tubular member 68 of the next succeeding partition element l8.

In this apparatus, copper wire and steel wire, such as No. 36 iron wire SAE 1010 have been successfully plated at rates of wire movement in the range of 10 to 30 feet per minute and generally at rates of 1 foot per minute per foot of plating chamber, with nickel, chromium and like metals deposited from decomposable volatile compounds" such as nickel carbonyls and hydrides.

When using a five segment or compartment apparatus described in connection with the drawing, plating gases were excluded from the non-plating sections or compartments by passing through these compartments inert gas at rates in the range of 10 to 20 cubic feet per hour.

In the plating chambers gas flow of mixedgas containing inert gas such as nitrogen mixed with volatile metal compounds is at a gas rate in the range of 2 to cubic feet per hour.

In the plating of nickel upon No. 36 iron wire 6 SAE 1010 the following conditions were maintained:

Wire rate 18 feet per minute,

Temperature of the wire in the anneal compartments 1,000 E,

Temperature of the wire in the plating compartments approximately 395 F.,

Rate of flow of carbon dioxide gas through the three annealing compartments in series approximately 14 cubic feet per hour,

Rate of flow of gas through the plating compartments approximately 3 cubic feet per hour, with nickel carbonyl vapors being present in the ratio of approximately 5%; ounces of carbonyl per cubic foot of carbon dioxide gas.

It will be understood that while the method and apparatus disclosed and described herein illustrate a preferred form of invention, modifications can be made without departing from the spirit of the invention, and that modifications that fall within the scope of the appended claims are intended to be included herein.

We claim:

1. The method of plating metal wire of continuous length which comprises continuously moving the wire therealong from a source of supply through a plurality of chambers including a gaseous metal plating chamber, heating said wire as the same is continuously moved along to a temperature suificient to decompose a heat-decomposable gaseous metal compound brought in contact therewith, said moving hot wire being maintained in a non-oxidizing atmosphere, moving said heated wire into said plat-'- ing chamber and subjecting the same to a continuously moving gaseous mass at least a portion of which comprises a heat-decomposable gaseous metal compound, said wire being heated to a temperature sufiicient to cause decomposition of said heat-decomposable gaseous metal compound which is circulated in contact therewith and deposition of the metal constituent thereof on the surface of the wire as the same is continuously moved therealong, and maintaining a differential in gaseous pressures between said plating chamber and preceding and succeeding chambers, said pressures within the chambers adjacent the plating chamber being slightly higher than that within said plating chamber to prevent leakage of said gaseous metal compound from said plating chamber.

2. The method of plating metal wire of continuous length which comprises continuously moving the wire therealong from a source of supply through a plurality of chambers including a gaseous metal plating chamber, heating said wire as the same is continuously moved along to a temperature sufficient to anneal said wire and in the range of about 800 F. to 1200 F., said moving wire being maintained in a nonoxidizing atmosphere. lowering the temperatureof the wire to a temperature sufficient to decornpose a heat-decomposable gaseous metal com-- accacss:

gaseous pressures between said. plating chamber and preceding and succeeding chambers, saidpressure within the chambers adjacent, the plating. chamber being. slightly higher than that within said plating chamberto prevent.- leakage 012 said gaseous.- metal compound; from said plating chamber.

3;. The method of plating. metal wire of continuous length which comprises continuously moving the wire; therealong from a source of supply through a plurality of chambers including a gaseous; metal plating chamber, heating said wire under non-oxidizing atmospheric conditions a the: same: is continuously moved along to a temperature sufficient to. anneal said wire and in the. range of. about 800 F. to 1200" F., said: annealing being: effected by passing electric current through said wire to; cause: said wire to be. heated. to the annealing temperature, lowering; the. temperature of the wire. by shunting a portion of the electric current passing; through said wherebysaid; wire is heated to a lower temperature, and moving said heated wire into said plating chamber subjecting said lower temperature wire to a continuously moving gaseous mass at least a portion of which comprises a heat. de-composable gaseous metal compound, said wire being heated to a temperature sufficient to cause decomposition of said heat-decomposable gaseous metal compound which is circulated in contact therewith and deposition of the metal constituent thereof on the surface of the. wire as the same is continuously moved therealong, and maintaining a differential in gaseous pressures between said plating chamher and preceding and succeeding chambers, said pressures within the chambers adjacent the plating chamber being slightly higher than that within said plating chamber to prevent leakage of said gaseous metal compound from saidplating chamber.

4-. The method of plating metal wire of continuous length which comprises continuously moving the wire therealong from a source of supply, heating said wire under non-oxidizing atmospheric conditions as the same is continuously moved along to a temperature sufiicient to anneal said wire, said annealing being efiected by passing electric current through said wire to cause said wire to be heatedto the annealing temperature and in the range of about 800 F. to 1200' F., lowering the temperature of the wire as the same is moved along to about 350 F. to 450 F; by shunting a portion of the electric current passing through said wire whereby said wire is heated to a lower temperature, moving saidheated wire through a plating-zone and sub-..

J'ccting said lower temperature heated wire while in said zone to a continuously moving gaseous mass at-least a portion of which. comprises a heat-decomposable gaseous metal compound, saidwire being heated to a temperature sufficient to cause decomposition of said heat-decomposable gaseous metal compound which is circulated in contact therewith and deposition of. the metal constituent thereof on the surface of the wire as the same is continuously moved therealong, and maintaining a, differential in gaseous pressure between said plating. zone and preceding and succeeding zones, said pressures.

within the zones adjacent the plating zone being slightly higher than that within said plating zonev to prevent: leakage of; said gaseous metal compound fromv said plating? zonei 5. The methcd. of plating: metal wire of con-- tinuouslength; which comprises. continuously moving the wire therealong from a. source of supply through a plurality of chambers including a. gaseous metal. plating chamber, heating said wire under non-oxidizing atmospheric con. ditions. as the same is continuously'moved. alon to. a temperature. snfiicient to decompose aheatdecomposable gaseous metal compound brought in contact therewith, moving said heated wire intov said plating chamberand. subjecting said. wire to a continuously moving gaseous mass comprising carbon. dioxide and nickel carbonyl, said wire being heated to a temperature: su-fficient to cause decomposition of said nickel earbonyl and deposition of the nickel onthe surface.- of the. wire as the same is continuously 'moved therealong, and maintaining a differential. in gaseous pressures between said plating chamber and preceding and succeeding chambers, said pressures within the chambers adjacent the. plating chamber being slightly a higher than that within said plating chamber to prevent leakage of. said gaseous metal compound from said plating chamber.

6. The method of plating metal wire of continuous length which comprises continuously :moving the wire therealong from a source of supply, heating said wire under non-oxidizing atmospheric conditions as the same is continuously moved along to a temperature sufficient to anneal said wire, said annealing temperature being effected by passing electricv current through said wire to cause the same to be heated by resistance to. the passage of electric current to the, annealing temperature and in the range of: about 800 F. to 1200 F., lowering the temperature of. thewire as the same is moved along; by shunting a portion of the electric: current passing through said wire whereby said wire is heated to a lower temperature, moving. said heated wire through a plating zone and subjecting said lower temperature heated wire while.- in said zone to, a continuously moving gaseous mass comprising nickelcarbonyl, said wire being heated to a; temperature suflicient to cause decomposition of said nickel carbonyl and deposition. of the nickel on the surface. of the wire as the same is continuously moved therealong, and maintaining. a difierential in gaseous pressure between. saidplating zone and preceding and succeeding zones, said pressures within the zones ad- .iacentthe; plating zone being slightly higher than thatwi-thi-n said plating zone to prevent leakage. of said gaseous metal compound from said plating zone.

ALBERT 0-. FINK. ALFRED E. BISHOP.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,987,576 Moers Jan. 8, 1935 2,203,241 Waldron June 4, 1940 2,344,138 Drummond Mar. 14, 1944 2,405,662 McMa-nus et a1. Aug. 13, 1946 2,442,485 Cook June 1, 1948 2,475,601 Fink July 12, 1949

Claims (1)

1. THE METHOD OF PLATING METAL WIRE OF CONTINUOUS LENGTH WHICH COMPRISES CONTINUOUSLY MOVING THE WIRE THEREALONG FROM A SOURCE OF SUPPLY THROUGH A PLURALITY OF CHAMBERS INCLUDING A GASEOUS METAL PLATING CHAMBER, HEATING SAID WIRE AS THE SAME IS CONTINUOUSLY MOVED ALONG TO A TEMPERATURE SUFFICIENT TO DECOMPOSE A HEAT-DECOMPOSABLE GASEOUS METAL COMPOUND BROUGHT IN CONTACT THEREWITH, SAID MOVING HOT WIRE BEING MAINTAINED IN A NON-OXIDIZING ATMOSPHERE, MOVING SAID HEATED WIRE INTO SAID PLATING CHAMBER AND SUBJECTING THE SAME TO A CONTINUOUSLY MOVING GASEOUS MASS OF AT LEAST A PORTION OF WHICH COMPRISES A HEAT-DECOMPOSABLE GASEOUS METAL COMPOUND, SAID WIRE BEING HEATED TO A TEMPERATURE SUFFICIENT TO CAUSE DECOMPOSITION OF SAID HEAT-DECOMPOSABLE GASEOUS METAL COMPOUND WHICH IS CIRCULATED IN CONTACT THEREWITH AND DEPOSITION OF THE METAL CONSTITUENT THEREOF ON THE SURFACE OF THE WIRE AS THE SAME IS CONTINUOUSLY MOVED THEREALONG, AND MAINTAINING A DIFFERENTIAL IN GASEOUS PRESSURES BETWEEN SAID PLATING CHAMBER AND PRECEDING AND SUCCEEDING CHAMBERS, SAID PRESSURES WITHIN THE CHAMBERS ADJACENT THE PLATING CHAMBER BEING SLIGHTLY HIGHER THAN THAT WITHIN SAID PLATING CHAMBER TO PREVENT LEAKAGE OF SAID GASEOUS METAL COMPOUND FROM SAID PLATING CHAMBER.

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