US2309745A - Method of processing wire - Google Patents

Description

Feb. 2, 1943.

T. G. BERGIN METHOD 0F PROCESSING w-IRE Filed Oct. 14, 1940 Patented Feb. 2, 1%3

2,309,745 ivm'rnon oF raocnssrNG wma Thomas G. Bergin, New Haven, Conn., assigner to The American Steel and Wire Company oi' New `liersev, a corporation or New .iersey Appiication October 14, 194%, Serial No. 361,157

3 Claims. (Cl. 14S-6.5)

This invention relates to the manufacture oi wire and particularly to an improved method of processing steel Wire by continuous operations thereon.

Heretofore, it was the general practice in processing wire to condition it for further cold working or coating, such as galvanizing, to clean and coat the wire after the heat treatment thereof as a separate operation due to the fact that a heavy iron oxide coat or scale formed on the surface of the wire during the patenting or heat treating step. Such cleaning of the wire was not only expensive and required extra cleaning` equipment, but was also laborious and increased the production costs of the wire materially.

Also, the wire would necessarily have to be transported from the heat treating furnaces to the cleaning and coating equipment which was inconvenient and required excessive handling thereof. Furthermore, the wire tended to corrode a short time after the processing thereof and during storage which not only necessitated the cleaning of the same if the wire was to be further worked upon, but such corrosion was oftentimes objected to by the customer which, of course, resulted in frequent rejections.

In the present invention, there is provided a method of processing the wire wherein the oxidation of the wire is retarded and any oxide formed on the wire in the heating and quenching of the wire is reduced to a minimum and ypractically entirely eliminated as it passes continuously through the improved heat treating ``ing and further cold working such as coating.

to be combined as a continuous process, so as to eliminate the necessity of cleaning after heat treatment.

produced having the desired microscopic structure for immediate further cold working, such provide an improved method of processing wire' continuously by which a perfectly clean wire vis produced having a smooth galvanized nish.

Various other objects and advantages of this invention will be more apparent in the course of the following specification and will be particularly pointed out in the appended claims.

In the accompanying drawing there is shown, for the purpose of illustration, several embodiments which my invention may assume in practice.

In the drawing:

Figure 1 is a plan view of the apparatus or equipment for practicing the improved method of processing wire of my invention, showing a plurality of wires passing through the successive steps whereby a black oxide coating is obtained thereon;

Figure 2 is a side elevation of the same;

Figure 3 is a plan view similar to Figure 1 of the apparatus or equipment for practicing the improved method of processing wire of my invention so as to obtain a galvanized finish on Accordingly, it is the general object of the present invention to provide an improved method of heat treating the wire whereby the oxidation thereof is practically eliminated during the 4heat treating thereof thereby eliminating the the wire; and

Figure 4 is a side elevation thereof.

Referring more particularly to the drawing, the improved method of my invention for processing wire as shown in Figures 1 and 2 of the drawing, consists of depositing the coils of wire to be processed on a plurality of suitable swifts or reels 2, positioned at the entry end of the processing line. The wire then passes into and through a furnace or heating chamber 3 wherein the wire is heated to a predetermined temperature as it passes therethrough. This heating chamber may be an open chamber type furnace or any other suitable furnace which will heat the Wire to the desired temperature, but it is preferable that this heating chamber bean elongated pan containing a high temperature molten salt bath, which may be any neutral salt and consists preferably of a mixture of approximately percent by weight of sodium chloride and 40 percent by weight of potassium chloride which is heated in any suitable manner to a temperature above the critical temperature of the wire, namely, to approximately a temperature of between 1350 degrees and 1750 degrees Fahrenheit. The wire is held under the surface of the bath therein preferably by means of sheaves 4 and as the wire leaves this molten salt bath, a lm `of salt remains on the surface of the wire and provides a protection against oxidation of the surface thereof.

The wire then passes from the heating chamber or pan 3 directly into and through a pan 5 containing a low temperature molten salt bath having a reducing agent therein. This molten salt bath may be any suitable quenching salt and preferably consists of a mixture of approximately 27 percent by weight of sodium carbonate, 27 percent by weight of sodium hydroxide, 26 percent by weight of potassium chloride, and 20 percent by weight of sodium cyanide which acts as the reducing agent, with the bath being heated in any suitable manner. It is important that the temperature of this bath be maintained below the lower critical temperature of the wire, namely, at a temperature of approximately between 500 degrees and 1100 degrees Fahrenheit so as to prevent carburization of the wire. This bath acts both as a quench to produce the deslred microscopic structure and as a deoxidizing or reducing agent. The small amount of oxide which is formed on the surface of the wire while passing from the heating chamber 3 to the pan 5 in the air is immediately reduced by the sodium cyanide in the bath. The wire is held under the surface of this bath preferably by means of sheaves 6.

The Wire then passes from the pan 5, preferably over a roller or sheave I into and through a water bath in tank 8 which is preferably cold and in under a sheave 9 therein, and over a roller or sheave IU into and through a tank I2 which contains an alkaline cleaner wherein the excess salts carried by the wire from the salt baths are cleaned therefrom. 'I'his cleaning step is only used when there is some of the salt remaining on the wire or when the surface of the Wire has become oily or greasy from contact with the rollers and sheaves. It is preferable that this alkaline cleaner be heated in any suitable manner to a temperature of approximately between 150 degrees and 210 degrees Fahrenheit and the solution may be from to 10 percent by weight of cleaner to water. The wire then passes under the sheave I3 arranged in tank I2 and over the roller or sheave -I4 preferably into and through tank I5 containing water which is preferably hot and which is adapted to remove any of the alkaline cleaner from the surface of the wire carried over from tank I2. l

The wire then passes in under the sheave I6 in tank I5 over the rollers or sheaves I1 and I8 into tank I9 which contains a bath consisting of a solution of coating and' coloring salts. This salt bath preferably consists of a mixture of approximately 60 percent by weight of sodium hydroxide, 20 percent by weight of sodium nitrite and 20 percent by weight of sodium nitrate, such mixture being commonly known as Black Magic. The salts are preferably dissolved in water in such amounts so that the boiling point of the bath is approximately 250 degrees to 350 degrees Fahrenheit or of such a temperature that the desired finish can be obtained. This bath is heated to the boiling point of the solution in any suitable manner and as the wire passes therethrough the bath impregn'ates the surface of the wire and there is deposited thereon a coating of black oxide. It will be understood that the coating is formed by an oxidizing process which produces a wire having a relatively thin but a very adherent and continuous oxidized surface. The wire preferably passes around and over sheaves 20 arranged in the tank I9 with the length of the tank and the number of sheaves provided depending on the amount and thickness of coating desired.

From the tank I9 the Wire passes preferably over rollers or sheaves 2| and 22 into and through tank 23 containing preferably a cold water bath which washes any salt carried over from the coating and coloring bath in tank I9, and is kept in under the surface of the bath by means of sheaves 24 therein. The wire then passes from tank 23 preferably over rollers or sheaves 25 into and through tank 26 containing a solution of soluble oil and water which has a concentration of oil preferably from approximately 5 to 20 percent by weight. The wire passes in under the sheave 21 in the solution and out of the tank and over the roller or sheave 28 onto the blocks 29 which reel or coil the wire. It will be understood that the take-up blocks 29 are power driven by any suitable means and that the blocks pull or draw the wire through the successive steps which have been heretofore described. 'I'he blocks are driven and the speed varied correspondingly to the size of the wire and the type of wire being processed.

In the event that it is desired that the material or wire being processed not be coated, the

wire is passed through the heating chamber 3 and the low temperature molten salt bath in the pan 5 and the water bath in the tank 8 as has been described for processing black coated wire, and the wire is then coiled directly on the take-up blocks 29. That is, the alkaline cleaner bath in tank I2, the coloring and coating tank I9, and the oil and water solution in tank 26 are dispensed with in such processing. Such processing with the elimination of these steps provides a wire having a suitable microscopic structure with the surface thereof being extremely clean so as to permit further cold working thereof.

However, if the wire has been processed to final size and a coating or coloring thereon is all that is desired, it is necessary to pass the wire only through the alkaline cleaner in tank I2l the water bath in tank I5, the coloring or coating solution in tank I9, and in some cases, the solution of soluble oil and water in tank 26, with the take-up blocks 29 pulling the wire successively therethrough as before.

It will be understood that the teachings of my 4invention are not only limited to applying a black oxide coating to the wire, but may be used in connection with a galvanizing process. In such a case, as shown in Figures 3 and 4 of the drawing, the wire to be heat treated and galvanized is placed on swifts or reels 2 on the entry side of the line and, as before, the wire is passed through the heating chamber 3 and the low temperature molten salt bath in pan 5. The wire then passes from pan 5 over the rollers or sheaves 30 and 3I into and through a water bath in tank 32. The wire is held in under the surface' of the bath by sheave 33 arranged therein and. passes therefrom over the rollers or sheaves 34 and 3 5 into tank 36. The tank 36 contains a bath consisting of a solution of muriatic acid and water. The concentration of the acid in this bath may be from 4 to 30 percent ascent by weight, and the bath is preferably heated by any suitable means to a temperature of approximately between 100 degrees to 200 degrees Fahrenheit. The wire is held under the surface of this bathby sheave 31 arranged therein and passes over the roller or sheave 38 into tank 39, containing a water bath which is also preferably heated by any suitable means to a temperature of approximately between 100 degrees and 200 degrees Fahrenheit. The wire is held under the surface in this bath by means of sheave 40 arranged therein and passes over the roller or sheave 4l preferably into the tank 42.

The tank 42 contains a ilux bath which preferably consists of a solution of either zinc ammonium chloride or muriatic acid. ,It is not absolutely necessary that the wire pass through such a bath, but it is preferable that such'be used for best results. The wire is held under the surface of this bath by means of sheave 43 arranged therein `and passes therefrom over the rollers or sheaves 44 and 45 into tank 46.

The tank 46 contains a molten zinc bath which is preferably heatedv by any suitable means to a temperature of approximately between 800 degrees and 1000 degrees Fahrenheit. The wire in passing through this bath is coated with zinc and the thickness of this coating may be controlled by varying the speed of take-up blocks 28. 'Ihe wire passes in under the rollers or sheaves 41 in this bath and therefrom over the roller or sheave 28 onto tle coiling rolls or take-up blocks 29 as before.

It will be understood that not only one wire or coil of wire, but any number of wires or coils of wires as desired, maybe processed at one time in the improvedmethod of my invention. That is, a plurality of wires may be arranged in sideby-side relation as they pass through the steps of the present method of processing.

As a result of my invention, it will be seen that there is produced a wire having a coating winch will protect the surface of the wire and prevent it from corroding and at the same time, there is provided a wire having a coating which will act as a lubricant in the further cold drawing thereof which is a decided advantage.

While I have, in this application, specifically shown and described several embodiments of my invention, it will be understood that these embodiments are merely for the purpose o f illustration and description, and that various other forms may be devised within the scope of the invention, asfdefineddn the appended claims.

I claim:

i. The method of processing and conditioning steel wire which includes the steps of successively heatingl the wire to a temperature above the critical temperature thereof in such a medium so that the surface of the wire is free from heavy oxide or scale, passing the wire while maintaining the same out of contact with oxidizing agen,- cies into a relatively low temperature molten salt bath containing a cyanide wherein the wire is quenched rapidly down through the lower critical temperature thereof, so as to provide a wire having a tough and ductile structure and uniform drafting qualities with the surface of the wire being deoxidized by said salt bath and with a coating of salt being deposited thereon therein so as to protect the wire after it leaves said bath and until the wire has cooled to a temperature below that at which rapid oxidation takes place. passing the wire into and through a cleaning medium wherein the salts are removed from the surface of the wire so as to provide a clean surface patented wire, and then passing the wire through a medium wherein the surface of the wire is coated with a rust-retarding coating which is adapted tov act as a lubricant for subsequent drawing operations.

2. The method of processing and conditioning steel wire as defined in claim 1 wherein the medium through which the wire passes and in which the surface of the wire is coated with a rustretarding coating consists of a coloring salt solution whereby the surface of the wire is coated with a film of black oxide so as to protect the surface of the wire from oxidation and to condition the same for subsequent drawing operations.

3. The method of processing and conditioning steel wire which includes the steps of passing the wire intov and through a high temperature molten salt bath wherein the wire is heated to a temperature above the upper critical temperature thereof with the wire having a thin coating of salt deposited on the surface thereof as it leaves the bath whereby the wire is protected against oxidation, immediately passing the wire into a low temperature molten salt bath containing a cyanide wherein the wire is rapidly quenched down through its lower critical temperature to a temperature therebelow so as to provide a tough and ductile wire having uniform qualities, said wire having a coating of salt deposited on the surface thereof by said last-mentioned bath whereby the wire is protected from oxidation immediately after it leaves the bath and before it has cooled to a temperature below that at which rapid oxidation takes place, pass'- ing the wire into and through a cleaning medium wherein the salts are removed from the wire so as to provide a clean surfaced wire, and

THOMAS G. BERGIN.

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