US2156262A

US2156262A - Process of treating metal articles to alloy constituent metals

Info

Publication number: US2156262A
Application number: US648870A
Authority: US
Inventors: Colin G Fink; Deren Pincus
Original assignee: Individual
Current assignee: Individual
Priority date: 1932-12-27
Filing date: 1932-12-27
Publication date: 1939-05-02
Anticipated expiration: 1956-05-02

Description

May 2, 1939- c. G. FINK E1- Al. 2,155,262

PROCESS OF `TREATING METAL ARTCLES TO ALLOY CONSTITUENT 'NH'IJS4 Filed Dec. 27, 1932 WOM/ffyl C brom/m1 P/af/'fy C /e ani/7 y m m m Wo s/7 /ny Furnace Low emleraure M n DMENTORS Patented May 2, 1939 UNITED STATES liROCESS F TREATING METAL ARTICIS T0 ALLOY CONSTITUENT METALS Colin e. Fink ana Pincus Deren, New York, N. Y. Application December 27, 1932, Serial No. 648,870

y 16 Claims. This invention relates to a processA of treating metal articles, to alloy constituent metals, and

provides improvements therein.

Roberts-Austen (Philosophical ATransactions, Royal Society of London, 1897, Series A, 187 .p. 383) reviews the writings and work of scientists from the time of Pliny, 'on the subject of the diffusion of metals, (and also of matter) and states that previous investigators had reported that m alloys might be formed by placing carefullycleaned pieces of two constituent metals in juxtaposition and heating them to the melting point of the alloy to be formed, which was, in some cases 150 below the melting point of the more 16 fusible of the two metals. Looking backward,

this article of Roberts-Austen assumes the rank of a classic, and init may beperceived an adumi bration of the entire modern achievements base on the emissivity of matter. .In the experiments 20 reported by Robents-Austen, contrary to the present invention, the heats were maintained for 'long periods of time, thirty-one days, ten days, thirty days., twenty-nine days, forty-one days, four days, ten days, six days, as compared with minutes according to the present invention, and

the resulting alloys were non-uniform, the proportion ofthe two constituents varying progressively from the line of contact of the two metals.

Despite vthe scientific facts and data given by Roberts-Austen and many patents and publications which have since issued, we are unaware of any practical application thereof having been made in overcoming the -diflculties in the production of refractory and resistant alloy articles which have come into commercial use in the last of the article.v The alloying according to the.

present process may be effected in a very short time; minutes as compared with hours according to Vother processes heretofore yused (such as chromizing and so-called heat-treatment" processes) and may be carried on in air, or in a reducing or non-oxidizing atmosphere in an ordinary manner.

'According to our process, an article asa Wire, rod, sheet, strip, shell, etc., is electroformed, or is formed of a metal which is readily worked, iron, nickel, copper, molybdenum, etc., or a readily workable alloy, (or an article already. so formed), is coated with an electrodeposit of the metal to be alloyed therewith, and then heated to a temperature wherethe immediate faces of the metals in contact are molten or virtually so, which is at about the eutectic of the metals in contact, and above. The heating may be, and preferably is, carried out in two stages. In the first stage, the coated metal may be heated to a temperature at which a superficial -layer of oxide is formed on the outer metal, which oxide layer serves to protect the metal beneath the oxide against the much more rapid oxidation which would take place were the article heated initially to the higher temperature used in the second heating stage. Some diffusion of the coating metal into the metal beneath 1t may take place. In the second heating stage, the temperature is raised to about the eutectic melting-point, or above where rapid diffusion and alloying of the metals occurs. At this high temperature excessive consumption of the coating metal by oxidation is defeated by the rapid diffusion and alloying of said coating metal with the underlying metal.

Contrary to what might be expected, the formed article does not lose its form when heated at or above the melting point of the eutectic, the probable explanation being that at any one instant thecomposition of the eutectic only exists at a line within the body of the article, the composition maintaining its solid form 'on each side of said line. Therefore, if the component metals are greater or less than the proportions forming the eutectic, the article will not melt, even though it be heated to a temperature at or above the tem perature at which the eutectic melts.

'I'he use of a reducing or non-oxidizing atmosphere, such as generally understood, around the articles during heating, while it does not prevent oxidation at the high temperatures employed in our-process, reduces the consumption of the coatlng metal by oxidation, and its use is hence preferred. I

, While we have spoken of the temperature of the eutectic of the alloy as the ltemperature to which the constituent metals of thestarting articles is to be heated in'effecting a union thereof to form the alloy layer or band having a definite alloy or eutectic composition, nevertheless in practice temperaturesfwhich vary somewhat from' the temperatures of Vthe melting points of the eutectics given in scientic treatises and tables are employed. A precise rule for all. cases cannot be given. There is some empiricism in ascertaining-the operating temperature. Certain limitations in the means of makinghigh-temperature.

measurements inclusive of optical pyrometers must be recognized. Measurements obtained by the use of such instruments are not precise, a certain amount of variability bein'g inherent in the instruments themselves, and in the perceptions of different users. l(See Fink Patent No. 2,082,622 for a like instance). ,Moreoven metals are rarely obtainable in a pure state, and those used in' industry are known to contain small amounts of other metals and of so-called nonmetals. Commercial iron and steelcommonly contain carbon, manganese, sulphur, phosphorus, silicon, etc. Nickel (electrolytio as well as that produced in a crucible) contains cobalt, iron and copper. Copper contains some copper oxide. Electrolytic chromium is usually quite pure; but contains some chromium oxide. 'Ihe noble metals almost invariably contain. other of the noble metals along with -the principal constituent. The composition of the commercial forms of metals generally is similar.

Moreover, the temperature given in scientific tables for the melting point of a eutectic, varies. For example, in the case of iron and chromium, Adcock, Journal Iron and Steel Institute, London, Sept. 1931, gives the temperature of the meltingpoint of the eutectic as 1507 C. Von Vegesack, Zeitschrift fr Anorganische Chemie, 154, 30 (1926) gives a range of temperatures for the melting-point of the iron-chromium eutectic from 1150 C. when the iron used contains 4% carbon to 1490 C. when the iron used containspractically no carbon. These appear to be the most recent data available.

In practice we use a temperature at or about the melting point of the eutectic, at which a rapid alloying of the constituent metals occurs, whilel the article maintains its form, with the forma.- tion of an alloy layer or band having a denite alloy composition, which temperature is usually within about C.l of the temperature of the melting-point of the eutecticv given in scientific tables, for eutecticsv having high melting-points, for example those above 1000 C.

An example' of our process-is as follows:

An iron wire, or strip, etc., is coated with an electro-deposit of chromium to any desired thickness. 'Strips and the like may be coated on one `or both sides; The coated wire is then heated in the ordinary atmosphere of an electrically heatedv ofhydrogen (or in the ordinary atmosphere of a furnace) at a suitable temperature to form a supercial chromium-'oxide lm on the surface of' the chromium coating; for instance, at 1000 to 1200u C.-for one to two minutes. The coated article is then transferred to a furnace and heated in an atmosphere of hydrogen (or in the ordinary atmosphere of an electrically-heatediurnace) at a temperature of 100 to 1500" C. for 3 to 30 minutes, depending on the thickness of the chromium coating. Ordinary commercial hydrogen may be used.

`Another example is as follows: l

A strip of cobalt is electroformed, and then coated with an electrodeposit of chromium, so that the proportions will be as desired. Alternate layers may be formed. This is then heated to a temperature at or somewhat above lts eutectic melting-point, which was between 1400 to 1500 C. A preliminary heating at a lower temperature may' be practiced, if desired.

Other examples of our process are as. follows:

A nickel wire or strip is coated with an electro-deposit of chromium vto any desired thickness, 0r an iron wire or strip is coated with an electro-deposit of nickel, or of nickel and chromium, to any desired thickness. These coated wires or strips, etc. are then heated in the manner hereinbefore described. A preliminary heating, as desired or found most suitable, as heretofore described, may be practiced.

If the outermost metal-layer is relatively susceptible to oxidation, an electroplate of a metal which is relatively resistant to oxidation (nickel for example) may be applied before heating. This may be a thin deposit.

Further examples, of alloy sheets, rods, wires,

etc., for which the present process may be usedA 'advantageously are: Ni-Fe; Pt-l'r; Cr-Ni;

sheet, strip, rod wire, etc. (iron for example),

enters a. cleaning bath l0 at a;'from which it enters a washing bath H, as indicated at b. i The sheet, etc., is then electroplated, entering a chromium-plating bath l2 for example, as indicated at c. The article may then be given a protective coating (of nickel,- for example), and Afer this purpose may enter a washing bath- I3 at d, an acid-dip I8 at e, and a nickel-plating bath I5 at f. It may then enter a washing bath it at g. I1' it is desired to form a' preliminary supercial oxid film in the article, it may then go into a low temperature furnace iias indicated at h. The

article enters the furnace l 8 'at i where it is heated toa temperature at or about the eutectic melting point, or above, to form the alloy. 'I'he exit from the furnace it is indicated at lc. The article, as

points above 1000 C. and also above the melting point of the eutectic, an forming an alloy of .the

constituent metals by hea -the coated article at a temperature at or about ti@ melting point of the eutectic of the metals, which produce rapid diffusion while the article maintains its form.

2. 'A process of treating metal articles to alloy constituent metals, which comprises. coating a formed metal article with a solid adherent layer of another metal in intimate metallic contact with the ilrst metal, the metals having melting points above 1000 C. and also above the melting point of the eutectic, and forming an alloy of the constituent metals by heating the coated'article at a temperature at or about the melting point of the eutectic of the metals, which will produce rapid diffusion while the article maintains its form, in a reducing or non-oxidizing atmosphere.

3. A process oi' treating metal articles to alloy constituent metals, which comprises coating a formed metal article with a solid adherent layer of another metal in intimate metallic contact with the rst metal, the metals having melting points above 1000 C. and also above the melting point of the eutectic, heating the coated articleto form a supercial oxide iilm thereon, and thereafter forming an alloy of the constituent metals by heating the coated article at or about the melting point of the eutectic of the metals, which will produce rapid diffusion while the article maintains its form.

4. A process of treating metal articles to alloy constituent metals, which comprises coating a formed metal article with a solid adherent layer of another metal in intimate metallic contact with the rst metal, the metals having melting points above 1000 C. and also above the melting point yof the eutectic, heating the coated article in a reducing or non-oxidizing atmosphere to form a superficial oxide i'llm thereon, and thereafter forming an alloy of the constituent metals by heating the coated article at or about the melting point of the eutectic of the metals, which will produce rapid diffusion while the' article maintains its form.

5. A process'of treating metal articles to alloy constituent metals, which comprises coating a formed metal article with a solid adherent layer oi' another metal in intimate metallic contact with vthe rst metal, the metals having melting points above 1000 C. and also above the melting point of the eutectic, heating the coated article to form a supercial oxide lm thereon, and thereafter forming an alloy of the constituent metals by yheating the coated article in a reducing or non-oxidizing atmosphere at or about the melting point of the eutectic of the metals, which will produce rapid diffusion while the article maintains its form.

6. A process of treating metal articles to alloy constituent metals, which comprises coating a formed metal article with a solid adherent layer of another metal in intimate metallic contact with the ilrst metal, the metals having melting points above 1000 C. and also above the melting point of the eutectic, heating the coated article to form a superficial oxide lm thereon, and thereafter forming anI alloy oi.' the constituent metals by heating the coated article at or about the melting point of the eutectic oi' the metals, which will produce rapid diilfusion while the article maintains its form, both heatings being done in an ordinary reducing or non-oxidizing atmosphere which incidentally contains some oxygen.

7. A process according to claim 1, further-comprising coating the outermost coat with a coat of a metal less susceptible to oxidation at high tem- 8. A process according to claim 1 wherein the article which is coated is electroformed.

9. In a process of treating metal articles to alloy constituent metals, forming an alloy of the constituent metals by heating a metal article having thereon a solid adherent coating metal in intimate metallic contact with the ilrst metal, the metals having melting points above 1000 C. and also above the melting point of the eutectic, at a temperature at or about the melting point of the eutectic of the metals, which will produce lrapid diffusion while the article maintains its form.

10. In a process of treating metal articles to alloy constituent metals forming an alloy of the constituent metals by heating a metal article having thereon a solid adherent coating metal in intimate metallic contact with the rstmetal to form a superiicial oxide lm thereon, said metals having melting points above 1000 C. and also above the melting point of the eutectic, and thereafter heating at a temperature at or about the melting-point of the eutectic of the metals, which will produce rapid diffusion while the article maintains its form.

11. In a process of treating metal articles to alloy constituent metals, coating the outermost coat of a coated metal article with a coat of metal less susceptible to oxidation at high temperature than said outermost coat, said metal and coating having melting points above 1000 C. and also above the meltingpoint of the eutectic, and then forming an alloy of the constituent metals by heating at a temperature at or about vthe melting-point of the eutectic of the metals, which will produce rapid diffusion while the metal maintains its form.

12. In a process of forming ferro-chromium alloy articles, alloying the constituents by heatin g an article comprising layers of iron and v chromium in intimatemetallic contact at a temperature at or about the temperature of the melting point of the eutectic, between 1400 to 1500" C. for a relatively short time while the metals rapidly diiuse and the article maintains its form.

13. In a process of forming ferro-chromium alloy articles, according to claim 12, preliminarily heating said article at a lower temperature to develop a thin protective oxid lm thereon.

14. In a process of forming ferro-nickel-chromium alloy articles, alloying the constituents by heating an article comprising layers of iron, nickel and chromium in intimate metallic contact at a. temperature at or about the temperature of the melting point of the eutectic, above 1400 C. for a relatively short time while the metals rapidly diffuse and the article maintains its form.

15. In a process of forming ferro-nickel-chromium alloyarticles according to claim 14, preliminarily heating said article at a lower temperature to develop a thin protective oxid nlm there- 16. In a process of forming alloy articles, alloying the constituents by heating an article comprising layers of metals in -intimate metallic contact having melting points above 1400 C. at a temperature at or aboutthe melting point of the eutectic of the metals for a relative short time while the metals rapidly diffuse and the article -maintains its form.