US1555578A

US1555578A - Treatment of metals

Info

Publication number: US1555578A
Authority: US
Inventors: Goodwin H Howe
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1923-11-06
Filing date: 1923-11-06
Publication date: 1925-09-29
Anticipated expiration: 1942-09-29

Description

Sept. 29, 1925.

G. H. HOWE TREATMENT OF METALS Filed NOV. 1923 Inventor: Goodwin H. Howe,

His Attornqg w Patented Sept. 29, 1925.

UNITED STATES PATENT OFFICE.

GOODWIN H. HOWE, O'F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMTANY, A CORPORATION OF NEW YORK. I

TREATMENT or Marl ns.

To all whom it may aoncem:

Be it known that I, Gooowm H. Howe, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in the Treatment of Metals, of which the following is a specification. L

My invention relates to the art of protecting metallic articles against the effects of oxidation suchas will ordinarily occur at high temperatures. It is now well-known that metallic articles made of various metals, such as iron and copper, may be protected against oxidation at high temperatures by causing to be formed upon th surface of the article an alloy of the metal itself with another metal, such as aluminum. In a patent-isued to Tycho Van Aller, No. 1,155,974,

dated October 5, 1915, there is described and claimed a process of protecting metals in this way and an article of manufacture so protected. In this patent one of the methods described consists in employing powdered aluminum which is caused to alloy with the foundation metal at the surface. Subsequent patents such, for instance, as patents to Dantsizen, No. 1,381,085, dated June 7, 1921, Ruder, No. 1,346,062, dated July 6, 1920, and Ortiz, No. 1,409,017, dated March 7, 1922, describe and claim improvements upon the Van Aller patent, having for their objects the rendering of the treatment more effective and the simplification of the process.

It is now well known that the aluminum or other alloying metal on the surface gradually penetrates the article under the action of hi h temperatures. This diffusion of the alloying metal throughout the article in time reduces the roportion of the alloying metal at the sur ace, resulting in reduced protection against oxidation. I have found that by locating a mass of the alloying metal within the article to be protected and then forming an alloy on the surface, high temperatures will have the effect of causing the metal of the mass to penetrate the article and thus afford protection against oxidation. I have found, for instance, that an iron or steel tube having an aluminum core between the inner and outer surfaces will withstand high temperatures for a consid-' erably longer period than would be the case with a tube treated on the surface by the ordinary methods.

My invention is particularly well adapted for application to tubes although it is by no means limited thereto. I shall therefore describe my invention as applied to tubes and then point'out the scope of my inventionin the appended claims. Also, my invention is obviously not limited to the use of aluminum as a heat protecting metal. It has broad application to the use of various other alloying metals, such as chromium or zirconium.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is an end elevation view of a tube constructed in, accordance with my invention; Fig. 2 is a View similar to Fig. 1 illustrating the diffusion of the alloying metal when the tube is subjected to high temperatures; Fig. 3 is a longitudinal section view of a tube showing methods of sealing and closing the ends; while Fig. 4 is a longitudinal section view similar to Fig. 3 showing the diffusion of the aluminum.

In. the accompanying drawing I have shown for purposes of illustration one embodiment of my invention. In this case I have shown a composite or fabricated tube to which my invention is applied. This tube is made up of inner and outer tubes 10 and 11 made of oxidizable metal, such as steel or iron. Between these two tubes is an aluminum tube or core 12, the three tubes fitting tightly together and being assembled so as to constitute in effect one tube.

As shown in Fig. 3 the ends of the inner and outer tubes 10 and ll'may be united by making the aluminum tube 12 somewhat shorter so as to leave a space at the ends between the tubes 10 and 11 into which a ring 13 "is driven. The ring may be made of the same material as the tubes 10 and 11. A welded joint 14 is formed at the ends between the ring 13 and the tubes. A tube is thus formed which to all appearances'is a homogeneous steel or iron tube. In some cases, for example in pyrometer tubes, it may be desirable to close one or both ends of the composite-tube. .This may be done by providing a composite cap on the end to be closed. As shown in F1g;- 3, an inner cap 15 has its rim driven in place between one of the methods described in the patents,

the tubes in the manner of the ring 13. Over cap 15 is placed an outer cap 16 with a sheet of aluminum 17 between them. The cap 16 is suitably secured on the end of the outer tube 11 for example by means of screw threads 18.

The composite tube thus formed is now treated so as to cause aluminum or other suitable metal to alloy with the surface of the tube by some method as, for instance,

above referred to. Both the inner and outer surfaces of the tube may be thus treated 'to form thin surface layers of aluminum alloy although the treatment need not necessarily be applied to both surfaces unless required by the nature of the service to which the tube is to be subjected. One of the common uses for tubes is in oil stills, these tubes some times being three or four inches in diameter and 20 feet or more in length. It is usual to treat these tubeson both the inner and outer surfaces.

When the composite tub'eabove described is placed in service and sub'ected to'high temperatures the aluminum 0 the

aluminum cores

12 and 17 will gradually penetrate the metal of the tubes by diffusing both inward and outward as indicated in Figs. 2 and 4. The cores provide an excess of aluminum in the interior of the article. At the same time the aluminum of the inner and

outer surface alloys

19 and 20 will gradually penetrate and diffuse through the metal. As this diffusion of aluminum proceeds during continued use at high temperatures, the diffusion outward from the masses of

aluminum

12 and 17 will meet the diffusion of aluminum inward from the surface alloy and have a tendency to retard or check the diffusion of aluminum from the surface alloy. The aluminum content of the surface alloy is thus maintained suiiiciently high to assure protection against oxidation when the tube is subjected to high temperatures.

It will be observed that the diffusion of the metal of the cores forms'an internal layer of heat resisting alloy. In case of failure therefore of the inner or outer surface layers of alloy, a complete failure of the article cannot result due to the relatively strong internal layer of alloy. Such a failure at the surface may result from improper treatment during the formation of the surface layers of alloy, or it may result from subse uent mechanical injury puncturing the sur ace layer. The improper treatment may be due to the fact that some parts of the article are more in-accessible than others. For example, in a tube having one end closed, as shown in Fig. 3, the inner surface at the closed end may not be thoroughly treated. Complete failure of the tube however, will be preventedby the internal layer I of alloy. I have found also that the alumiand form a num of the

cores

12 and 17 tends to etrate the joints between the cap 15 an the inner and outer tubes 10 and 11, as shown in Fig. 4, thus preventing failure from oxidation at these places and also securelywelding the cap in place.

While I have described my invention as embodied in concrete-form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do notlimit my invention thereto, since various modificationsthereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope .of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. In a metallic article provided with a surface alloy with another metal to protect it against the effects of high temperatures, the method of checkin diffusion of the alloying metal from to surface inward which consists in causing diffusion of a simi- I lar metal outward from the interior of the article.

2. In a metallic article provided with a surface alloy with another metal to protect it against the effects of high temperatures, the method of checking diffusion of the alloying metal from the surface inward which consists'in providing an excess of said metal in the interior of said article.

3. In a metallic article provided with a surface alloy with another metal to protect it against the effects of high temperatures, the method of checkin diffusion of the alloying metal from t e surface inward which consists in providing a core of the alloying metal in t e interior of the article whereby the metal of. the core is diffused outward upon the application of high temperatures.-

4. The method of protecting metallic articles against the efiects of high temperatures which consists in providing in the interior of the article a mass of a metal adapted to penetrate the metal of the article upon the application of high temperature eat resisting alloy therewith, and then forming an alloy of said metal and the article upon the surface of the article.

5. The method of protecting metallic articles against the effects of high temperatures which consists in inserting an aluminum core in thearticle, and then forming on the surface of'the article an alloy of aluminum and the metal of the article.

6. The method of protecting metallic tubes against the oxidizing effects of high temperatures which consists in first forming a composite tube having aluminum between the inner and outer surfaces of the tube, and then forming on' the surface of the tube an .alloy of aluminum and the metal of the tube.

7. The method of protecting metallic tubes against the effects of high temperatures which consists in first forming a composite tube, comprising inner and outer tubes of the metal with an aluminum tube between them, and then forming on the surface of the composite tube an alloy of aluminum with the surface metal.

8. The method of closing a composite tube comprising inner and outer tubes made of an oxidizable metal separated by a layer of an alloying metal adapted to penetrate the tubes upon the application ofhigh temperatures and form therewith a heat resisting alloy, which consists in securing an end member to said composite tube made of inner and outer layers of an oxidizable metal separated by a layer of said alloying metal.

9. The method of closing a composite tube comprising inner and outer tubes made of an oxidizable metal sepa ated by a layer of aluminum, which consists in securing a ca to said composite tube made of inner an outer layers of an oxidizable metal separated by a layer of aluminum.

10. As an article of manufacture a metallie article made of an oxidizable metal provided with an internal mass of an alloying metal adapted to penetrate the oxidizable metal upon the application of high temperatures and form a heat resisting alloy there with, and a surface layer of an alloy of said alloying metal and the oxidizable metal.

11. As an article of manufacture a metallic article made of an oxidizable metal such as iron or steel having an aluminum core, the surface metal of the article being alloyed with aluminum.

12. As an article of manufacture a composite tube having aluminum between the inner and outer surfaces, the surface metal of the composite tube being alloyed with aluminum.

l3..As an article of manufacture a com posite metallic tube comprising inner and outer tubes of oxidizable metals such as iron or steel and an aluminum tube between them,

.the surface metalfof the composite tube being alloyed with aluminum.

In. Witness whereof, I have hereunto set my hand this 5th day of November, 1923.

GOODWIN H. HOWE.