US2986810A - Production of composite metal stock having internal channels - Google Patents

Description

June 6,1961 R. M. BRICK 2,986,310

PRODUCTION OF COMPOSITE METAL STOCK HAVING INTERNAL CHANNELS Filed Feb. 11, 1959 FIG. 2

Rober/ M Bria/r INVENTOR ATTORNEYS United tates Patent O 2,986,810 PRODUCTION OF COMPOSITE METAL STOCK HAVING INTERNAL CHANNELS Robert M. Brick, Hinsdale, Ill., assignor to Continental Can Company, Inc., New York, N.Y., a corporation of New York Filed Feb. 11, 1959, Ser. No. 792,588 7 Claims. (Cl. 29-423) This invention relates to the production of a composite stock having non-welded regions in its cross-section, and is more particularly concerned with anti-welding materials to be employed in making such stock.

It is known to prepare a body of metal having cores of anti-Welding or resist material therein, and to roll or otherwise reduce the thickness of such body, therewith decreasing both the metal thickness and also the thickness of the anti-welding layer or core within the same, while extending the surface area. Prior proposals have been to employ inert powdery or powderable materials, such as fine aluminum oxide, fine silica or silicate, etc.: but with them the reduction operation causes at least parts of the powder to become embedded in the internal surface, so that they cannot be removed except at uneconomic expense. The reduced body is opened out by mechanical or fluid pressure means, to provide a hollow body such as a tube. When such a tube is employed to conduct a fluid, the particles gradually are loosened and move with the fluid, becoming an abrasive in the pump, moving part walls, etc., if the conduit is part of the lubricating system of an automobile, mechanical refrigerator, etc. If such a material is made up into a container for engine oil, likewise, the pick-up of the particles is extremely undesirable because they form an oil-borne abrasive, and inherently are of extremely small size due to the necessities of reducing their layer thickness to a small fraction of an inch during the total thickness reduction. Some such particles are so fine that they pass through oil filters, while others can collect and bridge passages and stop fluid flow.

According to the present invention, such anti-weld or resist materials are constituted of powders which are soluble in a fluid not injurious to the body stock material. The selection of the anti-weld substance can be accomplished with consideration of the body stock material being used, the temperature and other conditions of preparation of the composite stock, the solvent which can be employed for removing it, and the feasibility of employing the substance and solvent for treatment of the body stock material.

As a first example, a tube is to be made from pure aluminum or a commercial aluminum alloy having the chemical characteristics of aluminum. An ingot is cast of such metal, with a longitudinal channel therein, which is filled with a Water-soluble alkali or alkaline earth metal halide, such as anhydrous sodium chloride. The ends of the ingot are sealed, to prevent easy access of air or water to the core. The ingot is then hot rolled at an appropriate temperature and cold rolled to the desired final thickness. Sodium chloride has a melting point of 804 C., well above the temperature used in hot rolling; and remains in place as a dry and easily powdered anti-weld mass which is without chemical effect upon the body metal. It has been noted that the salt appears to act as a deformable plastic under the conditions of hot pressure rolling. The core flattens regularly and in proportion as the rolling reduces the original ingot thickness: and the ingot is extended in length, with little change of width, to form a long strip of laminate or composite stock having an outer surface provided by the aluminum in the form of two layers which are connected integrally along the margins of the strip and at stripes between cores if more than one core is used: and with regions occupied by the flattened core material, at which no welding has occurred. The laminate strip can be cut to the desired length and opened out to form the tube. The interior of the tube is flushed with water to dissovle the salt, rinsed and dried.

The original particle size of the salt employed is immaterial, so long as the resist can be introduced as a mass of substantially uniform density per unit of volume when tubular articles of regular size and wall thickness are to be produced. The large particles fracture under roll or hammer pressures, and the small particles appear to spread or smear on aluminum, and act not only as a weld-preventing resist material, but also as a lubricant at the contacted metal surfaces. By comparison, graphite exhibits a similar behavior, but is not readily removable and has the bad property of establishing, in the presence of aqueous solutions for example, an electrical battery eifect with severe metal corrosion resulting therefrom.

As another example, in which an internal treatment of the tube wall is to be accomplished, is with the use of sodium or potassium dichromate, each of which is soluble in hot water. After reduction and opening-out, washing by a current of hot water removes most of the dichromate, While a minor portion then reacts with the metal at the internal wall surface to improve its corrosion resistance and ability to effect adhesion with enamels. Trisodium phosphate can be similarly employed.

(A) As a further example, when only cold reduction and extension, as by cold-rolling, is to be employed, lower-melting substances can be utilized, noting that therewith there is no heating to provoke charring and loss of solubility, and the evolution of gases. In each case, the maximum temperature for such operations as heat-soaking when used, rolling or hammering, etc. must be below the melting point of the resist particles: and inversely the resist must be selected to remain non-fluid at the needed operating temperatures.

(B) The melting point of pure aluminum is about 660 degrees C. or 1220 degrees F. Aluminum alloys have somewhat lower melting points. Desirable hot rolling temperatures are below 500 degrees C. or 930 degrees F. Such temperatures are well below the melting point of sodium chloride, sodium triphosphate, and other usable metal salts. The temperatures of heat-soaking and hotrolling may be selected below the melting point of the metal salt in many cases: for example, by employing temperatures below 400 degrees C., the alkali metal dichromates may be employed to fill channels without decomposition during such later heating.

The procedure can be employed for forming articles of various shapes, with discontinuities therein in the form of cavities or channels, with longitudinal and transverse passages. Thus the billet can be formed by two plates or slabs having at predetermined locations therebetween a pattern formed by the resist material and corresponding to the desired cavities or channels, but of smaller dimensions, and with the plates joined at the areas outside the resist localities. Such a billet can then be reduced and extended by rolling and cross-rolling, by pressing, or by hammering, until the selected thickness is attained and the surface dimensions have been extended to the desired size for producing the article. The article is then expanded, as by fluid pressure applied in the channels until the metal layers at these channels are separated to provide passages of the desired shape. Solvent is then introduced, in washing steps, to remove the resist material.

A billet for this purpose may be made by printing or painting the desired channel pattern on sheet aluminum,

for example, using a saturated brine solution with or without excess sodium chloride in fine crystals. Subsequent Warming expels the water, and leaves salt crystals in the desired pattern. The deposit may be repeated, if a greater thickness is desired. A second sheet is then superimposed and the assembly tack-Welded at the edges, heated and hot-rolled so that the non-coated areas are welded together. Thereafter the rolling can be continued, including cold-rolling for temper, until the desired dimensions are attained.

The procedure may be employed with many metals where it is desired to produce thin-walled tubes or like structures economically. The resist material is selected in thelight of the properties of the metal, and the temperatures of handling with the resist material present. For example, sugar can be employed in cold-rolling steel, as by edge-welding two strips or plates, with the resist material between them, partly opening the rolled assembly, removing the sugar by leaching, hot-annealing, forming to a desired shape by completing" the opening or separation of the laminations.

A notable point is that the resist material may be recovered for re-use, by collecting the leached liquors and evaporating ofi the leaching solvent.

The resist material need not be chemically pure. For example, rock salt and sea salt can be the form used for sodium chloride.

In practice, such resists have the advantage of spreading or extending regularly during the reduction operations, without a ripple effect or maldistribution sometimes observed when for example finely powdered silica, S is employed as a resist material with aluminum.

A soluble salt can also be applied as a localized coating over connected areas of a sheet of body stock, and a second sheet roll-welded to the coated sheet at the areas not coated. The laminate stock can then be rolled to the desired thickness, cut to expose one or more of the coated areas, opened out by fluid pressure, which may be by a solvent of the coating material and thereby assisting in the separation of the layers, and finally flushed to remove the anti-weld materials.

An illustrative practice is shown on the accompanying drawing, in which:

FIG. 1 is an upright section through an ingot with antiweld cores therein.

FIG. 2 is a perspective view of a strip prepared by rolling the ingot of FIG. 1.

FIG. 3 is a perspective view of a part of the strip, opened out to a tube, and showing the use of a jet of fluid for removing the anti-weld material.

FIG. 4 is a roll of the strip material of FIG. 2, prepared for storage or shipment.

In these drawings, the ingot of FIG. 1 has the cores 10, of anhydrous sodium chloride for example, surrounded by cast aluminum metal 11, and having its ends closed by welding. Upon rolling, the strip S of FIG. 2 is formed, with its outer surface provided by the integral jacket 12 of aluminum, surrounding the several flattened cores 18. In FIG. 2, one end of the strip has been out 011?, to show the internal arrangement. The strip S of FIG. 2 can then be slit along upright planes at lines 14, passing through the integral metal bridges between the cores 13, cut to length, and the individual parts opened out into tubes 15, FIG. 3. A nozzle 16 can project water into one end of the tube so that this water dissolves out and flushes away the core material. The tube can be rotated as shown by the arrow to facilitate the removal with a minimum amount of solvent.

The rolled strip S, FIG. 2, or the slit lengths thereof with ends still sealed, can be sold and shipped as such, with the core material present, to avoid dents or deformations which might occur with the opened tube 15 of FIG. 3; noting also that the strip can be wound into a roll R, FIG. 4, for'storage or shipment in a minimum space.

It is obvious that the illustrative practices are not restrictive, and that the invention can be practiced in many ways wtihin the scope of the appended claims.

I claim:

1. The method of making a composite stock having metal layers separate and non-welded to one another, which comprises preparing a metal billet having an internal channel containing a soluble weld-preventing resist material which remains solid at a hot-rolling temperature for the metal and with the metal of the billet enclosing the resist material, heating to said hot-rolling temperature for the metal and extending the surface area of the billet and thereby reducing its thickness wherewith the metal and resist material are conjointly extended to form a body having surface layers of metal connected at edges of the reduced billet with an intervening internal layer of the residue of the resist material, separating the metal layers, and washing the resist material from the metal layers.

2. The method as in claim 1, in which the resist material is a water-soluble salt and the billet is rolled while heated to a hot-rolling temperature below the melting point of the salt and at which it is plastic.

3. The method as in claim 2, in which the salt is sodium chloride.

4. The method as in claim 2, in which the salt is a water-soluble metal chromate.

5. The method as in claim 2, in which the billet is heated prior to the extension of its area, and the salt is an alkali metal dichromate.

6. The method as in claim 2, in which the salt is trisodium phosphate.

7. The method as in claim 2, in which the billet is heated prior to the extension of its area, and the salt is trisodium phosphate.

References Cited in the file of this patent UNITED STATES PATENTS 29,276 Holmes July 24, 1860 377,317 Marshall Jan. 31, 1888 1,966,453 Lyon July 17, 1934 1,977,448 Lyon Oct. 16, 1934 2,212,481 Sendzimir Aug. 20, 1940 2,663,928 Wheeler Dec. 29, 1953

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