US2325041A - Beryllium cementation - Google Patents

Description

Patented July 27,1943

UNITED STATESL'PIATENT' orrlcs j mun s. 2:", Forest 13am]. Hg:

assignor to Cooper-Will Philadelphia, Pa., a corporation of Delaware No Drawing.

Jieryllillm.

5 Clam. (CI. 148 133) v This invention relates to new and useful improvements in products and methods involving the cementation of beryllium into other metals and more particularly the cementation of beryllium into copper.

Prior to the present invention practical cementation of beryllium into other metals has virtually been imposible due to the fact that the intense heat required therefor causes rapid oxidation of the beryllium. According y, it has herewmre been necessary to make numerous metal articles,

and particularly those of copper, entirely of a copper beryllium alloy even though the characteristic hardness, strength and capability for heat-treatment of such an alloy may be required at the surface only of such articles. This is an expensive and often a diiiicult task.

In processes of cementation generally two metals capable of alloying are heated in close contact with each other to the end that there is an inner penetration of each into the other and the formation of surface alloys on both. The depth of these surface alloys increases with time and temperature and for practical purposes the temperature chosen is usually not far below the melting point of the lower melting point of the two metals involved. Also in order to promote intimate contact one of the metals is usually usedin powder form while the other, which is to form the desired finished article, is used in solid form.

In most instances the intense heat required to effect cementation causes rapid oxidation of effecting the cementation of beryllium into cop per which is convenient, effective and entirely economical.

These and other objects of the invention as well as the features and details incident thereto are hereinafter fully set forth and described,

iii

the metallic powders used with the result that the cementation desired or sought is substantially hindered and sometimes wholly prevented. This oxidation sometimesis sought to be alleviated by carrying out the work in protective atmospher of, for example, hydrogen, but such procedure is expensive, not always practical and not always wholly effective. Thus the practical principal object ofthe present invention is to provide a cementation product of copper having a surface alloy of copper beryllium characterized by the hardness, strength and heat-treatability of the copper beryllium alloy series.

Another but equally important object of the invention is to provide a method or process for The present invention comprises, among other things, the discovery that if a copper article is embedded in a powdered beryllium copper alloy within a container and heated at a predetermined temperature for a proper time and then subsequently cooled, the copper, article when removed from its matrix of powdered alloy will have 'a surface alloy of copper beryllium there,- on. The surface alloyed article may then be subjected to standard conventional heat treatments for th precipitation hardening of alloys such as the beryllium'copper here involved. v

In practicing the invention, I prefer to use a beryllium rich copper alloy (containing from 10% to beryllium) as the source of beryllium and as such alloys are quite brittle they can readily be reduced to a powder of the desired mesh fineness. For good results the copper beryllium alloy should be reduced to a powder of at least approximately 50. mesh and preferably approximately mesh. The container in which the powdered alloy and embedded'copper article are heated should, of course, be capable of withstanding high temperatures and I have found a ferro-chrome or ceramic box or graphite crucible to be entirely satisfactory. The

container should be closed orfsealed as tightly as possible and if a metal container is used themerit are, of course, dependent upon the depth of the surface alloy to be formed on the article. As previously stated, the temperature employed to effect cementation is usually Just below the melting point of the lower melting of the two metals involved and according to the present process the temperatures of heat treatment may range from approximately 600 C. to approximately 800' 0., the latter temperature being slightly below the melting point of the copper beryllium eutectic.

The duration of time required for the heat treatment at these temperatures varies widely depending "D n the depth of the surface alloy time and temperature can be employed to give essentially the same surface alloy depth and the only definite statement that may be made on this point is that for a particular surface alloy depth the time or duration of the heat-treatment maybe said to be inversely proportional to the temperature of that treatment.

The following examples are illustrative of the present invention:

' Example I A copper beryllium alloy containing those elements in the proportion of 90% and re- As illustrative of this particular phase of the invention a specimen of copper was embedded in a powder of about 100 mesh of an alloy con-- taining approximately 10% beryllium and 90% copper. This was then heated in an atmosphere of hydrogen for about two hours at a temperature of approximately 800 C.', and upon cooling the copper was reheated for three hours in hydrogen in the absence of the alloy powder to cause the beryllium to migrate and thus dilute the rich surface alloy. The article was then heat-treated in the conventional manner and the hardness thereof was found to be about 350 Brinell.

By the present invention many useful and novel copper articles can be produced which require at their surface only the hardness, strength and capacity for heat treatment that characterizes spectively, was powdered to 100 mesh. This powder was then placed in a suitable container and a copper plate one inch thick was embedded in said powder. The container and its contents were then heated in a furnace for about eight hours at a temperature of approximately 800 C.

In order to check the depth of surface alloy the plate was then sawed so as'to expose a cross- .section thereof and examination of the section showed that the beryllium had penetrated almost the complete section of the plate leaving only a very small portion of unalloyed copper at themterior thereof. The thus surface-alloyed plate was then given theconventional standard heat treatment for precipitation hardening thereof, and the hardness of various portions or the surface and cross-section (except the unalloyed copper at the center) was found to be from 450 to 500 Brinell.

, Example II The same alloy copper plate employed in Example I was heated at a temperature of approximately 800 C. for a period of about one hour in the manner above described and a check of the depth of the surface alloy showed that the beryllium had penetrated the copper plate to a depth I of about .050 inch.

In employing the process of the present invention to produce surface alloys of considerable depth, I. have found that the extreme outer surface or skin of the articles being treated may in some cases contain a higher percentage of beryllium than is required for the best economy. Now, it is known that from approximately 2% to about 6% of beryllium produces the best rethe copper beryllium alloys. As an example, in certain very severe applications bearings of copper beryllium have been used, and by the process of this invention such bearings can be made with only the wearing surface of copper beryllium thus affording greater economy and ease of manufacture.

In other instances, it is desirable that certain articles in addition to having strength and hardness shall also havehigh electrical and heat conductivity. In respect of the latter, pure copper is of course superior to copper beryllium alloy. In such cases it is an advantage, quite irrespective of economy, to limit the hardness and strength to the surface and retain in the interior the desired high conductivity of electricity and heat possessed by pure copper. Such articles can readily be produced by beryllium cementation. Representative of this class of articles are welding electrodes and all manner of structural members carrying electric currents, especially those exposed to heat. In these the alloy surface furnishes the strength and hardness that persist even at relatively high temperature, while the unalloyed interior furnishes the electrical and heat conductivity.

By the process of this invention, bars, billets, and other copper shapes can be given a deep surface of beryllium alloy. These shapes can then be worked into rods, sheets and wires, which still have a beryllium alloy surface, proportionately reduced in thickness of course. These can then be heat-treated to develop the hardness cause the beryllium already on the surface of I the article to migrate or penetrate farther into the interior of said article and thereby produce the desired depth of penetration. This beryllium at the surface is furnished at the expense and strength of the alloy surfaces. In this way wires can be made which combine high tensile strength and great resistance to abrasion, with high conductivity Similarly sheets can be made with superior resistance to wear and to certain .types of chemical corrosion.

While certain embodiments of the invention have been herein set forth and described, it is not intended to limit the invention to such disclosures but that changes and variations may be made withinthe scope of the annexed claims.

I claim:

1. In the method of producing surface alloys of copper beryllium on a copper body, the steps comprising heating said copper body in the presence of a powdered copper beryllium alloy, and

then subsequently heating the body in the absence of said powdered alloy to reduce the surface concentration and increase the depth of penetration of the beryllium in said body.

2. In the method of producing surface alloys of copper beryllium on a copper body, the steps comprising heating said copper body in the presence of a powdered copper beryllium alloy con centration and increase aaauamntaining from 10% to 90% beryllium, and then subsequently heating the--body-inthe absence of said powdered'elloy to reduce the surface conthe depth of penetration of the beryllium in said body.

ence. of a powdered temperatures from approximately 600 C. to 800 0., and then subsequently heating the body in the absence of said powdered alloy to reduce the surface concentration and increase the depth or 3 In the method of producing surface al1oys\penetration of the beryllium in said body.

of copper beryllium on a copper body, the steps comprising heating said copper body in the presence ofa powdered copper beryllium alloy containing approximately 90% copper, the balance being beryllium, and then subsequently heating the body in the absence of said powdered alloy to reduce the surface concentration and increase the depth of penetration of the beryllium in said body.

4. in the method-oi producing surface alloys of copper beryllium on a copper body, the steps comprising heating said copper body in the prea- 5. In the method of producing surface alloys of copper beryllium on a copper y, the steps comprising heating said copper body in the presence of a powdered copper beryllium alloy containing from 19% to 90% beryllium at temperatures from approximately 600 C. to 800 0., and then subsequently heating the body in the absence of said powdered alloy to reduce the sur- .face concentration and increase the depth of y penetration of the beryllium in said body.

HUGH S. COOPER.

copper beryllium alloy at