US1125158A - Process of making clad metals. - Google Patents

Description

W. M. RAGE. PROCESS OF MAKING GLAD METALS.

APPLICATION FILED APR. 20, 1910.

Patented Jan. 19,1915.

PROCESS OF MAKING CLAD METALS.

Specification of Letters Patent.

Patented Jan. 19, 1915..

Application filed Ap1fi120, 1910. Serial No. 556,601.

To all whom it may concern:

Be it known that I, WILLIAM MARSHALL Paoaa citizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of ennsylvania, have invented certain new and useful Improvements in Processes of Making Clad Metals, of which the'following is a specification.

This invention relates to processes of making clad metals; and it comprises a method wherein a ferrous metal body is preliminarily covered with an oXid coating of a certain type and is thereafter contacted with molten copper or cupriferous metal; all as more fully hereinafter set forth and as claimed.

.Copper and steel joined with a firm and permanent union have long been desired in the art, since it is obviously advantageous 1f the two metals can be so joined in a comparatively large body, such as a compound billet, and afterward rolled or otherwise worked down to final dimensionsto form a finished article carrying the desired amount of copper united thereto. But practical difliculties have until lately prevented the attainment of this desirable type of union between the two metals and have forced reliance upon the production of finished articles of naked steel-or the like with a subsequent copper coating by galvanic means. Coating of the finished article in this manner is not only unduly expensive but the coatings are not of a desirable character, being very crystalline and porous while having but little adhesion to the base; an adhesion which is often not much greater than the internal strains tending to produce peeling. In use, corrosive gases and fluids penetratethrough the porosities and attack the underlying steel, setting up a galvanic couple with the aid of the copper which materially facilitates and quickens corrosion. Electroplated articles will not stand working down, partly because the coating has no real partly because of the quality of the coating itself.

In the prior art many attempts were-made to produce unionsby-direct casting of cop; per against steel, the steelusuallv having been first carefully cleansed. These attempts, however, produced no successful results for a number of reasons. If the steel were employed cold, as often was, the first layer of copper coming into contact cohesion to the base and with it solidified before there was time for a union. If thesteel were hot the surface was generally ox1dized and carried a coating of oxid which acted as a spacing means,

under the conditions obtaining, while as the exterior layers of copper in the mold solidifledthe gases which copper evolves in solidifying were forced toward the center and accumulated along the line between the two metals, thereby further tending to prevent any union.

It is inpractice difficult to present a clean surface of steel to the action of the copper. And even where such a clean surface is presented and other conditions are favorable the union is not readily attained, the molten copper displaying a disinclination to wet the steel. And in the absence of a wetting contact no such molecular union or contact can be secured between the two metals as is necessary for a cohesive union. Recently however methods have been presented which produce the described type of firm and permanent union; one such method (Patent 853,716), consisting in substance in superheating the copper to a high degree and presenting carefully cleansed steel to it under the protection of a neutral gas adapt-.

ed to prevent oxidation. Under these circumstances the -molten copper actually con- I tacts with or wets the steel and unites therewith to form a clinging coat, the two metals being more or less alloyed in the joining layers in producing this coat. The steel billet may be dipped into the copper and withdrawn carrying a clinging film of copper or cbpper-iron alloy. A ainst this filmed surface a substantial quantity of copper may be cast by any desired method and at any convenient temperature. per so cast will unite freely with the filmed surface. Articles so produced may be The coprolled, drawn, swaged, stamped, struck, and

ried. It is compound metal of this type in which the metals are united by a union which is, or is equivalent to, a weld union I obtain a firm and permanent union, yet, as

I have discovered, a preliminary coating of oxid on the ferrous metal is not so objectionable as'has been presumed and may even be useful where proper advantage is taken of its chemical and physical properties. In another application Serial No. 467,651 if have described and claimed a process wherein the steel object is initially treated in an atmosphere of superheated streaming steam in order to produce a closely cohering coating of the character of a magnetic oxid. 0n immersing this oxidized object in a layer'of molten copper of the proper temperature, the layer of cohering oxid reacts with underlying carbon in the steel to form pure iron, such pure iron coming both from the reduced oxid and from the underlying iron which has been robbed of carbon. While steel does not unite with copper with great readiness, iron containing less carbon displays a greater affinity, either chemically or physically, andprobably' both, for copper so that with a' steel object carrying a. layer of pure iron unions may be easily effected, even where the topper is at a comparatively low temperature.

streaming steam. If for instance aniron billet be rolled down hot in the usual manner, it is left covered with a thin, firmly cohering coating of oxid which is mostly magnetic oxid of iron; that is, is a combination of; the ferrous-and the ferric oxids in more or less varying proportions. .'ll1is coating under propenconditions isnot only adapted for reduction by underlying carbon in the steel object, but is in itself by reason of the contained ferrous oxid, a reducing agent wh ch has a desirable reaction uponvcertain impurities of the copper; As copper ordinarilv comes into the market it invariably contains a considerable amount of oxygen and oxids, partly in a dissolved state and partly in the form of discrete oxid particles. Co per in the usual practice is never poled sufficiently to free it of all oxygen and oxid's; .overpoled copper being presumed of lower quality than that which has not been poled to such a degree. This assumption that some oxygen and oxids are desirable in copper is not altogether true and a removal of these bodies I find to be desirable. And

l have now discovered that the coating of magnetic oxid, which is formed in thememes bon with the dissolved oxygen and oxids of the copper is apt to be relatively slow and to retard the progress of the union, the evolved gases continuing for a comparatively long period of time to come up between the two metals and tending to prevent a true contact between them at all the points between abutting surfaces. lhe surface of clean steel is very dense and is therefore not atgaclfied with extreme rapidity by the copper By covering the steel with a suitable layer I of a suitable oxid and then bringing it into contact with molten copper under proper conditions several actions go 4m at once. The outer layer of magnetic oxid frees the proximate copper of its dissolved oxygen and oxids while the layer of the oxid next the steel reacts with underlving carbon in the described manner until'the oxid disappears. vAt this point the steel billet is covered with a. layer of carbon-free iron while the proximate .layer of the copper is free of oxids and these two layers tend to unite at comparatively low temperatures; low-1' temperatures than are feasible in the direct union of clean steel and molten copper.

The manner in which the molten copper is brought into contact with the steel covered with the oxid layer maybe widely varied within the purview of the present invention; asmay the preliminary treatment such copper. The billet which is to form 1 the core or base of the compound metal ob- In such working down it is covered with the described coating oxid. After working down it is allowed to cool and cut to any suitable shape, this shape being of course such as is convenient in the subsequent union. It may then be pickled to free it of loose oxid, scale, sand or the like, or the pickling may be omitted. I Loose oxid'is not in actual contact with the steel and hence is not useful, but in coating it will be detached. rise and float. Where the billet is pickled, it is preferable to use a halogen cid,-such as hydrochloric acid or hydrofluoric acid. as theseacids give iron compounds which will volatilize in the subseouent heating to high temperatures. With this billet molten copper'is next contacted. The body of molten copper employed may of the ferrous metal which is to be united to worked down from a larger size while hot. I

mamas i a be secured in any manner desired, as by melting a shell placed around a round billet, or by casting a shell around the billet, or even by placing copper around such a billet in small pieces and heating it until it becomes molten.

The billet may be electroplated if desired prior to' bringing into contact with the molten copper, though this operation is not of great utility. The magnetic oxid formed I in the manner described being conductive of current, plating is feasible, but dipping in a solution of metallic salts is apt to disturb the oxid coating and to leave saline residues which may interfere with subsequent operations. As a rule, the use of fluxes and slags in the present operation is not necessary or desirable, though if it be desired to maintain the coating metal in any special condition or of any special composition a floating flux cover may be used. The halogen salts such as common salt, potassium chlorid, calcium chlorid, fiuorspar, cryolite, etc., or the common borate or silicate fluxes or slags, such as borax or waterglass may be used.

After bringing the copper into contact with the oxidized iron surface, the two metals are exposed to heat until the copper is in a freely molten condition and until the bubbling at the line of union between the two metals has ceased, showing the completion of the action of the oxid upon the carbon and the cessation of evolution of gaseous carbon oxids. At this point the two metals will be found united with the described type of union and the compound metal body may be removed from the apparatus in which it is formed, cooled and- Worked in any way desired. Or it may be taken directly from the coating apparatus and worked while still retaining the heat of the coating operation. The working may be in any of the usual ways as by passing.

through a rolling mill. Or it may be pushed through a die, squeezed into a mold, taken out and rolled, or in any other way subjected -to pressure. The pressure is not necessary in producing the described type of union, but is advantageous for other reasons as improving the character of the two metals.

In a typical embodiment of the present invention, for producing a conductor wire, I may take a bar, billet or ingot of steel of any desired composition and Work it down to the desired shape and size. In rolling down, the hot metal becomes covered with the familiar coat of. oxid or scale; a coat which is mainly a magnetic oxid, or anoxid that, empirically speaking, represents a combinationof ferrous oxid with ferric oxid in varying proportions. The scaled billet may next be pickled with hydrochloric or hydrofluoric acids, both of which -form volatile halogen compounds with any iron they may dissolve which will dissipate in the -may be washed in hot water and allowed to dry. The heat of the billet quickly dissipates the moisture. The billet is next contacted with molten copper in such manner as to preserve a layer of molten copper against the oxidized surface until bubbling ceases. This bubbling shows the evolution of oxids of carbon. The copper may now be allowed to solidify when it will be found firmlyunited to the steel by a union of the character of that described. In making billets for conductor wire, the contacting is best performed by plunging the billet beneath the surface of a body of molten copper, maintaining it there till bubbling ceases and then withdrawing, into a neutral or indifferent atmosphere, such as producer gas in a bell jar or casing. This body of copper may contain dissolved and alloying iron withoutdisadvantage; and, as a matter of fact, the presence of the iron in the copper tends to promote union since copperiron alloys unite more freely with steel and iron than does pure copper. On withdrawing the dipped billet from the dipping or alloying bath, if this bath be fairly hot and freely fluid, as it should be, the billet takes with it but a thin clinging film-like coating which is mainly a copper-iron alloy. If iron be not already contained in the bath, as it' ness is but slight, it does not materially interfere with the conductivity of the compound metal as a whole if proper subsequent methods of working down to wire be adopted while its presence appears to add a relatively considerable amount of strength, the copper iron alloys being strong metals.

After film coating or alloy coating ,the billet in the manner described, a further quantity of'copper is added by contacting the filmed surface with molten copper in any desired manner. and allowing this copper to set thereagainst. The copper readily unites with the filmed surface. In this operation the "contacting should be so performed as not to allow much agitation of the copper since the film coat of alloy may otherwise be partly difiused into and contaminate the main body of copper. One convenient way of operating is to place the filmed billet in a steel or iron mold casing, properly blackleaded or otherwise protected, and 'allow molten copper to flow down the side walls of the mold, filling up the space next the billet last. If the temperature of the copper and of the mold beproperly correlated, the first portions flowing down the mold walls may be solidified prior to molten copper contacting with the filmed surface, thereby absolutely preventing any substantial diffusion of iron thereinto. The filmed billet may be withdrawn from the alloying bath into a bottomless casing provided with inlet orifices near its top and maintained full of producer gas. A bottom may now be afiixed to the casing and casing and billet lowered together into a bath of pure molten copper until the latter enters the orifices and the mold fills.

The contact of the molten copper with the oxidized surface may be brought about in any manner, as by dipping the steel object or casting the molten copper thereagainst. Tn

the former case, the precautions now known in this art for shielding the dip-filmed hot copper surface, such as. the use of casings with inert atmospheres, etc., should be adopted to prevent oxidation of the film or alloy coat when once formed. When casting the molten copper into contact'with the steel object, the latter should be contained in a suitable mold and the usual precautions adopted for preventing the oxidation and contamination. Down or up pour may be used; and any of the known apparatus may be employed. Other metals than copper may be united to the dipped or filmed surface, as, for instance, brass, bronze, gold, silver, etc. Many metals will unite readily to the filmed surface which would not unite directly with steel or iron. The coating operation may be performed on articles brought to, or nearly to, finished size, in which case a dip coating may be sutlicient; but in general -it is better, as economizing labor and skill and producing a better product, to form a comparatively thick coat on acomparatively large billet, ingot, tube or the like and then reduce to finished dimensions. When so reduced, the coating metal is compacted between the core or base metal on the one hand and the working tool on the other 7 while held against lateral yielding by the existence of the basal weld union and so as texture of hard drawn wire.

sumes throughout its body a peculiar hard, close and dense texture like the surface The coating applied may be on of the steel object, as in producing rounds for clad wire, or on less than all sides, as in uniting a body of copper to one side of a. steel.sheet,'bar or billet for making clad sheets and plates. Or it may be on the interior of the object only, as in making copper lined tubing. But whatever the shape or nature of the article produced and are...

,molten copper can exist in contact with the oxidlayer for a time.

or otherwise contacted with the oxidized steel be allowed to set or solidify at the moment of contact no union can result. To produce a union it is necessary that molten copper be contacted with the oxid layer and the described actions be allowed to take place. There must be no opportunity for an accumulation of gas between the metals; nor is it desirable that any slag or flux which is not freely fluid at the temperature of the copper be present upon the steel surface since otherwise portions of it may remain and space away the two metals locally.

The whole body of the copper to form the by the coating bath; and even minimal traces of iron run down theconductivity of the coating inordinately.

After afiixing the coating of copper, either as a single step or as a double operation, the coating is allowed to'solidifv and the joined metals worked down by rolling or the like, either after reheating or while still retaining the heat of the operation, to produce wire, sheets, plates, etc.

A coating of oxid of the desired type may be formed by simply heating the ferrous metal in air without working; but in such event it is in general desirable to clean the ferrous metal first, as by sandblasting or pickling or both. But the coating formed by'heating and working is in general more desirable, both because of its chemical composition and because of its physical nature and of its state of coherence to the ferrous metal. In the described method where the oxid is used to oxidize underlying carbon, it is of course eminently desirable that the -oxid coat and the underlying carboniferous If the copper cast by hot working. A loose adherent coating of ferric oxid or hydrate such a is formed by ordinaryrusting is much less suitable.

In the accompanying illustration ll have shown, more or less diagrammatically,

furnace and apparatus for film-coating a similar view of appabillet; and Fig. 3 is a final thick coating of ratus for applying a copper.

In these illustrations, element 1 is a bar of steel shown as provided with aporter bar for convenience in handling. As shown in Fig.1, the billet carries a coating 3 of oxid of the described type. In 'Fig. 2, element 4 is a dipping furnace with end-firing means (not shown) waste gas vent 5 provided with door 6, and copper duct 7. This duct communicates with a dipping crucible 8. As shown the furnace is in dipping position. Above this dipping crucible is shown a protective mold casing 9 provided with pouring inlets or hoppers 10 communicating with the interior through ducts 11. Conduit 12 allows the introduction of a neutral gas. The casing as shown is above the dipping crucible and carries within itthe steel bar (1), now shown as carrying a film-coating of cppper or copper-iron alloy 13. As shown in Flg. 3, the'mold casing 15 transferred into position upon a bottom or base 14 with the filmed billet within it, ready for casting an additional thickness of I copper around such billet.

In the use of the described 'structure,a steel billet or char provided with. the oxid. coating 3 is dipped into molten copper in the dipping crucible 8, where the'described reactions take place. The steel billet now provided (as shown in Fig. 2) with copper-iron alloy film 13, is withdrawn into the protective mold as shown in Fig. 2. The protective mold and billet are now seated on base 14 and molten copper in the desired amount introduced through 10, such copper uniting with the metal of the film. After cooling to solidification of the coat ing, the mold and the coated billet are separated and the coated billet worked down.

1. The process of producing copper clad steel which comprises working a hot steelobject to produce a coherent coating of scale thereon and contacting the scale-coated surface with copper maintained in a .moltenceases and metallic union takes place.

face with copper maintained in a molten state thereagainst until bubbling ceases.

3. The process of producing copper clad steel which comprises working a hot steel object to producea coherent coating of scale thereon and dipping the scale-coated surface into molten copper until metallic union takes place.

4. The process of producing copper clad steel which comprises working a hot steel object to produce a coherent face into ,molten copper until bubbling ceases.

5. The process of producing copper clad steel which comprises covering the surface of steel with a coating of oxid of the magnetic type and contacting the oxid coated surface with molten copper until reaction 6. The process of producing copper clad. steel which comprises maintaining clean steel in a. heated condition in contact with air until it becomes covered with a coating of oxid of the magnetic type, plunging it into molten copper andimaintaining it beneath the surface of such'copper till reaction ceases.

7. The process of producing copper clad coating of scale thereon and dipping the scale-coated sursteel which comprises maintaining hot steel in contact with" until it becomes covered with a coating o f xid of the magnetic type and contacting t e oxid coated surface with molten copper until reaction ceases and metallic union takes place. y

8. The process of producing copper clad steel which comprises maintaining steel in contact with air until it becomes covered with a coating of oxid of the magnetic type, plunging it into molten copper and maintaining it per tillreaction ceases.

In testimony whereof,;I' affix my signa-' ture in the presence of witnesses. 4

- WILLIAM MARSHALL PAGE.

Witnesses:

P. M. WEIs, JoHN 13. PATTON.

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