US2636819A

US2636819A - Grain stabilizing metals and alloys

Info

Publication number: US2636819A
Application number: US208837A
Authority: US
Inventors: Johann S Streicher
Original assignee: Baker and Co Inc
Current assignee: Baker and Co Inc
Priority date: 1951-01-31
Filing date: 1951-01-31
Publication date: 1953-04-28
Anticipated expiration: 1970-04-28

Description

.state.

Patented Apr. 28, 1953 UNITED STATES GRAIN STABILIZING METALS AND I ALLOYS tion of New Jersey ATENT OFFICE No Drawing. Application January 31, 1951, Serial No. 208,837

. 11 Claims.

This invention relates to grain-stabilized metals and alloys. More particularly the present invention relates to grain-stabilized platinum metals and alloys thereof, or, to the six metals of the platinum group, that is, platinum, iridium, osmium, palladium, rhodium and ruthenium, and to the alloys in which any on of these metals is used as the principal ingredient and one or several of the others as a minor alloy constituent, or, several of these metals are used as principal ingredients and one or more of the remaining metals as minor alloy constituents, etc.

The invention is particularly applicabl to the following metals and alloys: platinum, iridium, osmium, palladium, rhodium, ruthenium, alloys of platinum and rhodium containing up to 40% rhodium, alloys of platinum and iridium containing up to 30% iridium, alloys of platinum and ruthenium containing up to 11% of ruthenium, alloys of platinum and osmium containing up to 10% of osmium. alloys of platinum and ruthenium and osmium containing up to 7% of osmium and up to ofruthenium, alloys of platinum, palladium and ruthenium containing from about 10 to 77% platinum, 12 to 89% palladium, and 1 to 11% ruthenium, alloys of palladium and mu thenium containing up to about 10% ruthenium, alloys of palladium and rhodium containing up to about 40% rhodium, and all the alloys of the platinum-palladium system. Al o, the invention is applicable to alloys of t e platinum metals with gold as an additional principal or minor con stituent, or, Wolfram, chromium, molybdenum or beryllium, etc. from about 0.05 to 8.90%, or metals of the iron group (iron, nickel, cobalt) as minor constituents.

The invention also relates to articles made from the above metals and alloys, especially for high temperature use, for in tance, catalyst gauzes, furnace heatin elements, thermocouple wires, ignition wires, platinum ware. electric con tact points, spinnerets for glass s innin cautery points, points for poker work, and the like; also for use requiring great hardness and wearrasistance. such as fountain pen points. spinnerets for artificial silk spinning, and the like.

Platinum metals are usually refined to an extreme degree of purity while in the metal sponge Inherent in such high purit platinum metal sponges is the tendency that when these sponges or'mixtures thereof are changed into -compact metal, either by means of the older powder metal methods, or, by means of the newer ither constituted of large crystals from the very beginning, or the metal changes rather readily during process annealing, or during use under sustained high heat into coarse grain structures of various kinds (exaggerated grain growth). Such grain-growth is often followed by mechanical deterioration, cracks, etc. making the metal useless for further cold working and/or fabricating, or the finished articles turn out unsuitable for prolonged use.

It is generally known today that exaggerated grain growth with pure metals and alloys thereof under sustained high heat is due mainly to the fact that they are to a very high degree free from inclusions. This experience was gained about forty years ago in connection with the fabrication of pure Wolfram wire. With regard to Wolfram the problem of stabilizing grain size during high temperature use was solved by means of the intentional incorporation of thorium oxide using the powder metal method. The same technique to stabilize grain size by means of intentional incorporation of inclusions, especially oxide inclusions, has been in recent years also adopted in connection with the metals and alloys of the platinum group in order to overcome the above characterized difficulties arising with the high temperature use of these metals and alloys.

Such intentional incorporation of oxide inclusions for the purpose of ram-stabilization of the platinum metals and alloys thereof closely fol lows the procedures used in connection with making grain-stabilized Wolfram wires. The platinum metal sponge powders are provided with a certain amount of finely divided refractory oxide while these metal sponges are still in the finely divided condition; the mixture is packed into steel molds and compressed with definite pressure; the resulting compacts are sintered in a hydrogen atmosphere for one or more hours at temperatures a few hundred degrees centigrade below fusing temperatures; and by means of hot working followed by cold working the metal compacts are worked into sizes and shapes required for technical rse. The oxide inclusions utilized with this method are re uired to resist hydrogen up to highest temperatures: and only such types of oxides could be used which resist fusion to a much higher degree than the metals and alloys with which they are used. The amount of each oxide inclusion required for each metal and alloy type to effect adequate grain stabilization has been determined by test, since it was found that difierent oxides seem to have in this regard special properties and do not act alike with regard to grain-stabilization.

It has now been found that the platinum metals and alloys as specified above lend themselves to grain-stabilization by means of oxide inclusions in a substantially improved manner over powder metal methods by means of fusion provided such fusion is accomplished in the presence of a strictly oxidizing atmosphere and in the absence of any fiuxing agent.

Platinum metals and alloys thereof do not form oxides which are stable at the melting temperatures of these metals. Their behaviour towards oxygen during high temperature heating can be generally characterized about as follows: they form oxides in small amount and at rather slow rate when heated in the presence of oxygen at 1 about 600 to 1200 degrees Centigrade. The oxides thus formed are attached to the surfaces of these metals only, and in rather thin layers. However, when the temperature rises above about 1200 degrees centigrade these platinum metal oxides decompose again into metal and oxygen with oxygen being quantitatively dissociated off. Therefore, on fusion, the platinum metals and alloys thereof fuse as metals free from any platinum metal oxide. Also, such fused platinum metals sorb oxygen only in relatively minor amount.

It has now been found, that the incorporation into such platinum metal melts of an element (metal or non-metal) of the chemically highly active type (initially it may form an alloy, or, a chemical compound with these platinum metals) in the presence of oxygen and at the high temperature of these melts results in the conversion of the chemically active element at a high rate into the oxide. This change into the oxide is enhanced by the high catalytic properties of the fused platinum metals in the presence of oxygen.

Colloidal ox de dis ersions are formed, which dispersions remain in the nascent state entangled with the metals of these melts provided the melts are kept free from fluxing agents. When the melts are cast and solidified the oxides thus formed act as grain stabilizers for the platinum metals.

Platinum metals and their alloys preserve their plastic properties in the presence of the colloidal oxide dispersions only when these oxide dispersions are incorporated in a l mited amount; and they become well grain-stabilized only with oxide dispersions which are applied in a wellbalanced adequate amount. These adequate amounts must be determined for each oxide. The required amounts of oxides are ascertained with present-day powder metal methods by means of experiment of rather ambiguous type which, however, leave many problems in this regard unsolved, especially with regard to so-called specific actions of oxide types applied.

The method of producing oxide dispersions by means of the present invention have resulted in. a superior method of determining the abovefundamental requirements for grain-stabilization. It has been discovered that these require-- ments are met when the elements to be changed. into the oxide dispersions are added based on the amount of oxide produced per volume of metal to be grain-stabilized expressed by means of the well-known chemical gram-equivalents. Through this technique of tracing grain-stabilization effects by means of gram-equivalents of oxide dispersion used, it has been found that the same gram equivalents of any of the oxides useful in effecting grain-stabilization has an equal grain stabilizing effect when used with the same:

volume of metal. This applies to individual oxide dispersions and also to dispersion mixtures. For instance: a normal equivalent weight of beryllium oxide (BeO) that is, 12.6 grams 1390, produces with 1000 cc. platinum or with 1000 cc. palladium the same effect as 15.1 grams silica (S102), 20.1 grams titania (T102), 30.7 grams zirconia (ZrOz), 66.0 grams thoria (ThOz) or, 77.0 grams barium oxide (BaO). The equivalent weight of a compound is determined by dividing the molecular weight of the compound by the valency of its principal atom or radical.

The usual percent figures per weight of metal do not disclose this important relationship since 1000 cc. platinum weigh approximately 21,400 grams, whereas 1000 cc. palladium weigh approximately 12,100 grams. The per cent figures per weight of metal are not a safe guide with regard to the important practical problem of how much of an oxide dispersion must be used in order to effect the same grain-stabilization as with a different oxide, or, with different metals and alloys, especially since the metals of the platinum group vary so much in specific gravities, and since the oxide dispersions useful for effecting grain stabilization with these metals vary in gram-equivalent weights from about 12.6 to 77.0. There is practically no end of testing and determining best amounts for any particular purpose with the usual per cent figures per weight of metal.

By applying oxide dispersions in gram-equivalent weights for the purpose of grain-stabilization of platinum metals and alloys thereof, it has been found that metals and alloys which are mechanically workable are obtained when col loidal oxide dispersions are produced in concentrations varying from about 0.02 to 2.5 gram equivalents per liter of metal, and a preferred average useful grain-stabilization is obta ned with oxide concentrations varying from about 0.1 to 2.0 gram e uivalents per liter of metal.

The accomplishment of this invention, as outlined above, requiring that platinum metals and alloys thereof be fused with a small but limited amount of an element which is able to produce on oxidation, a colloidal oxide dispersion within the medium of the fused platinum metals, is best realized by means of the high-frequen y melting procedure. The procedure is as follows: the metals to be provided with an oxide dispersion for the purpose of grain-stabilization are mixed in sponge powder state with the proper amount of powder of the element (base metal) which is meant to produce the oxide dispersion. The resulting mixture is compacted into pellets (briquettes) and is transferred to the crucible. At first, a non-oxidizing atmosphere, such as hydrogen, helium, argon, nitrogen, mixtures thereof, or vacuum, is applied while the compact is slowly heated for reaction. In this manner the constituents are made to react chemically, such reaction taking place at temperatures varying from about 500 to 900 degrees centigrade. Substantial heat is evolved. As soon as the reaction of the constituents has been accomplished (chemical metal compounds are in most cases thus formed) the non-oxidizing atmosphere is changed to an oxidizing atmosphere, such as air or oxygen. The reacted constituents are now fused. Oxidation of the melt starts instantly. The chemical compounds init ally formed start to decompose on fusion in the presence of oxygen, due t th high temperatures and the catalytic properti of the platinum metals, so that the small amount of the chemically active constituent is converted to a colloidal oxide dispersion in the time range varying from a few seconds to about five minutes fusion time.

The above procedure is most useful in cases where the platinum metals to be grain-stabilized are available in the sponge state as produced through the standard refining procedures. How ever, in case the metals to be grain-stabilized have already been compacted by means of pow-' der metal methods, or, by means of fusion, these platinum metals may be grain-stabilized by the use of pre-alloys.

Such pre-alloys are made by reacting in a non-oxidizing atmosphere or vacuum sponge powder pellets or briquettes which carry in substantial amount the elements to be later converted into the oxide dispersion. For the purpose of pre-alloying these elements may be used in amounts of about 0.1 to 25% per weight of metal. Another way of making pre-alloys is 'b 'wrapping the chemically active element powders into platinum or palladium foil and by reacting these packages in the presence of a non-oxidizing at mosphere or a vacuum at specified temperatures. These pre-alloys may be manufactured in large lots, especially in cases when the reacted prealloy is finally fused in a non-oxidizing atmosphere or vacuum. The large lots can then be subdivided into the small lots required for producing oxide dispersions having a definite con-.v

centration. A simpler way is to manufacture pre-alloys in small individual lots suitable for direct use with platinum melts or platinum alloy melts of definite and standard size. Th preferred method of using these. pre-alloys is by fusing them into the platinum group metals or platinum group metal alloys of a non-oxidizing or reducing atmosphere, in order to accomplish the required initial thorough mixture of constituents preceding the oxidation of the melts. The oxidation of these melts is then effected by changing to the oxidizing atmosphere as soon as such mixing is completed. The pre-alloys may also be incorporated by fusing the platinum metals in the presence of an oxidizing atmosphere (for instance, air) and by adding the pre-alloys, or, by fusing together the platinum metals and the pre-alloys in an oxidizing atmosphere. However, such modifications rarely accomplish the degree of even distribution of the oxides as are required for good grain stabilization while the oxides arein a nascent state as accomplished by the above preferred method.

The above procedures using pro-alloys for the purpose of grain-stabilization can also be applied with platinum metal compacts which have al-" ready been grain-stabilized either by the powder metal methods or by the methods of this invention for the purpose of modifying such compacts, or for the purpose of re-working grain-stabilized scrap metal.

There is a large number of oxides which can be produced by means of this method in the highly dispersed state within the medium of fused platinum metals for the purpose of grain stabilization. This is especially true, since it has been found that this system works well not'only with colloidal oxides which are solid while forming within the medium of the fused platinum metals and alloys giving a solid liquid dispersion system, but also with oxides which form with the liquid platinum metals and alloys liquid-liquid dispersions. The latter liquid immiscible oxides when present in small amounts inaccordance in the presence withthis new'method, act asgrain-stabilizers on solidification, inthe same manner as the oxides which are dispersed in'the nascent state in the solid state within the-fused metals. For instance, by means of the present method, silica, nickel oxide, cobalt oxide, iron oxide, vanadium oxide, boron trioxide, etc., are produced in the liquid state; But in this liquid state they are immiscible with the liquid. platinum metals, and they were found to have the faculty'when pro-' duced in the special small amount as required by'the present method that, while in the nascent state, they stay strongly entangled with fused platinum metals, especially in the presence of a strongly oxidizing atmosphere.

The'following table summarizes generally the most important oxides suitable for producing grain stabilization with platinum metals and alloys by means of the methods outlined above. The table indicates the amount of element required to be added to a liter of metal for producing a 1.0-normality oxide dispersion. The columns at the right end of the table indicate for the first and last oxide only, for comparison, the oxide per cent figures per weight of metal with reference to platinum and palladium. Per cent figures per weight of metalare, asmen tioned above, today usually used; but, as shown in the table, they tend to confuse basic issues with regard to the grain stab1l1zat1on problem.

One Gram Equivalent of Oxide Dispersion within the Medium of l000-cc. Platetqent Oxlde per inum Metal or Alloy Weght of Metal Base Ele- Oxide ment, Platinum Palladium grams The table includes only the most important oxides that can be usedfor grain stabilization by means of th present system, wherein a limited amount of a chemically active element, while being alloyed with and thoroughly distributed within any of the platinum metals or alloys, is, during fusion of such platinum metal or alloy changed into finely divided oxide in the presence of an oxidizing atmosphere, and such oxide, while in the nascent state is colloidally dispersed either as a liquid, or, as a solid within the medium of the fused platinum metals or alloys consisting of metals of the platinum group solely or with gold.

Therefore, the invention is applicable to all the elements (metals and non-metals) which, when incorporated into any platinum metal or platinum metal alloy in the specified small amount, fused, and. exposed to an oxidizing atmosphere, produces a liquid or solid non-volatile and chemically' stable oxide, and, subsequently changes the entire system into a colloidaldispersion.pre-

7 c'e'dingsolidification, wherein-the liquid platinum metal (or platinum-'metalalloy) is the dispersion medium Iand-"the oxide is dispersed in the liquid-platinum metal either in the solid or liquid state.

The 'above table includes only a few repre sentative' metals' of the rare'earth groups. However,-all the metals'of' these groups can be applied, espe'ciallyalso' theirrmixtures. Iron, cobalt and nickel-may be likewise used in spite of the fact that thebxides of these metals do not resist reducing: atmospheres. However, these oxides and mixtures thereon were found able to function asgrain stabilizing agentson casting and solidificationiprovided' the resulting grain stabilized compacts are used in the presence of oxidizing atmospheres. The "same applies to systems'provided with similar oxides easy to reduce by hydrogen, etc. such as tungsten oxide, uranium oxide, etc. The possibilities of using a liquid-liquid dispersion system of producing oxides which withstand reducing atmospheres, forinstance with silica, vanadium oxide, etc. have been already outlined above. Furthermore, it should be pointed "out that a plurality of two and more of thosenon-metals and metals may be'used which; on oxidation, form dispersions of oxide'mixtures having'refractory properties, such as, aluminum oxide/silica, magnesium oxide/aluminum oxide, x-iron oxide/chromium oxide, or, beryllium oxide/aluminum oxide.

The method used for producing the oxide dispersions as outlined above is a chemical method. The oxides are dispersed Within the medium of liquid metal in the chemically nascent state. Thereforathese oxides are .in a supreme state of dispersion, and, uponsolidification oi the system, better'grain stabilization is accomplished.

However; as is inherent in all chemically formed dispersions, especially with dispersions which originate from the system liquid-solid, there is thetendency for the'clispersed oxides to aggregate and to condensate, that is, to decrease the degree of dispersion. Such tendencies result in the crystallization of the dispersed oxides. Asymptom of such crystallization is the formation of skins, etc. Changes of this type produce, on solidification, grain boundary difficulties.

It has been found that changes due to agglomeration or condensation of dispersed oxides are hardly in evidence with the oxides which form liquid-liquid dispersions, that is, with oxides such as silica, titania, etc. Further, it has been found that with the liquid-solid dispersions the condensationof oxides occurs less with those oxides which are listed at the top of the above table which vary in gram-equivalent weights from about 12 to 20 grams, that is, with beryllium oxide, alumina, and magnesia. However, as gram-equivalent weights increase (see the table above) the tendency to condensate becomes pronounced, especially with the oxides which are characterized by higher equivalent weights.

On the other hand, ithas been found that the tendency to condensate of those oxides which form liquid-solid dispersions decreases as the concentration of the solid oxide drops below 0.75 gram equivalents per liter of metal. It been further found that this tendency to condensate' and to agglomerate decreases rather consistently when the concentrations of the solid oxides are madeto decrease to a concentration level 'of approximately one fifth (0.2) to one tenth (0.1) gram equivalents per liter of metal about-in proportion as equivalent weights in-x:

8 crease to such high values as .with'thorium oxide, barium oxide, etc.

Those grain stabilized ingots characterize themselves'as'the preferable ingots of this invention which either have incorporatedv the oxides effecting'grain stabilization-by means of the liquid-liquid dispersion system with an oxide concentration varying from 1.0 to 0.75 gram equivalents per liter of metal, or, which have incorporated the oxides effecting grain stabilizationby means of the liquid-soliddispersion system with oxide concentrations starting from the level of 1.00 gram equivalent per liter ofmetal with oxides having smallest equivalent weights (beryllium oxide; aluminum oxide, etc.) andby decreasing oxide concentrations to the level'of about 0.2 to 0.1 gram equivalents approximately proportionally as equivalent weights increase to thosehighest values as with thorium oxide, barium oxide, etc.

The preferred concentrations of oxide, expressed in gram equivalents per liter of metal or alloy, is tabulated below for a few of the oxides and metals:

- Thedescribed system for producing the grain stabilizing agents (the oxides) within the medium of liquid platinum'metals and platinum metal alloys is based on fusion in the'presence of an oxidizing atmosphere and that the metals constituting such medium do not form oxides while fused in the presence of an oxidizing atmosphere. Due to this fact the method is limited to the direct manufacture of grain-stabilized metal and alloys from metals and alloys of the platinum groups and to-metals and alloys of the platinum metal groups modified by the addition of gold since gold is the only other metal not affected by fusion in presence of oxygen.

' However, such grain-stabilized platinum metals and platinum metal alloys (and also their modifications by addition of gold) lend themselves to a modification of another kind, namely, by means of the addition of alloy constituents such as Wolfram, molybdenum, uranium, chromium, manganese, iron, cobalt, nickel, beryllium, rhe nium, copper, etc.' It is essential however that the compacts used for such modification with these readily oxidizing metal constituents are provided,'preceding such modification, with oxide grain stabilizers of the type which are resistant to a reducing atmosphere, such as hydrogen. The alloy modification is best accomplished by fusing the grain-stabilized platinum metals together with therequired amount of such base metals in the presence of a strong hydrogen blanket or in vacuum. In this manner may be produced grainstabilized alloys of the types as follows: grainstabilized alloys of: platinum and nickel contain-- ing up to about 10% of nickeLgrain-stabilized alloys of platinum and Wolfram containing up to about 6% of wolfram, grain-stabilized platinum and chromium alloys containing up to about 6% chromium, grain-stabilized alloys of platinum and copper containing up to about of copper, grain-stabilized alloys of palladium and copper containing up to about 30% of copper, grain stabilized alloys of platinum and beryllium containing up to about of beryllium, etc.

The ingots as produced by the present invention can be hot or cold worked with between anneals, or both, that is, the initial hot working of the still rather thick ingots can be continued by cold Working as soon as the ingots have been reduced to relatively small size. However, it has been found, that best fabricating results are attained with any type of grain-stabilized platinum metal or alloys thereof when the cold or hot working of the ingots is preceded by a soaking anneal at those temperatures found most suitable for between anneals and hot work. This soaking anneal is then required to precede any cooling to room temperature, and, as has been further found, any type of hot work is best performed by letting the as-cast ingot cool from its high manufacturing temperatures to the temperature most suitable for hot forging, hot rolling, hot swaging, etc., that is, when the as-cast ingot is allowed to cool only to the temperature of the soaking anneal preceding hot working.

The temperatures most suitable for the soaking anneal preceding cold or hot working of the grain-stabilized ingots of the present invention, and also for between anneals, vary from about 500 to about 1l00 centigrade. These temperatures are merely the temperatures which are known and used for efiecting the normal recovery and relief of internal stress with metals and alloys of this invention after any type of cold or hot work and while they are free from oxide inclusions. The lowest and lower temperatures of the above range apply to the pure metals such as platinum, palladium, etc., the higher and highest temperatures apply to the alloys of the metals of the platinum group, especially to those platinum and/or palladium alloys which have been modified by additions such as rhodium, iridium, ruthenium, osmium, and/or Wolfram, chromium, molybdenum, copper, nickel, cobalt, iron, etc. In other words, the specified soaking anneals, and the between anneals for the grain-stabilized metals and alloys of this invention require temperatures for fabricating which are below the temperatures which promote the tendency to produce grain growth or any type of secondary recrystallization with those metals and alloys which are free from oxide inclusions.

Hot and cold working of the grain stabilized ingots as produced in accordance with the present invention into sheet, foil, wire, etc., can be accomplished in the usual manner with total area reductions from about 40 to 75%. However, in case the metals and alloys of this invention are required to be fabricated into catalysts, such as gauzes, or, into electrical contact points which are known to require that they produce also special catalytic properties to accomplish supreme electrical performance, etc., total area reductions substantially above the 75% total limit were found to produce these catalytic properties in a special high degree. And highest, catalytic prop-. erties were found with grain stabilized metals and alloys when final total area reductions of at least 99% wereapplied, or, when preceding this final 10" total-reduction of at least 99%, a' total area reduction of at least 98% was applied, that is, preceding the last between anneal.

The following specific examples serve to illustrate the present invention but they are not intended to limit the same:

Example I 25 02s., or, 777.5 grams pure platinum sponge powder was intimately mixed with 0.125 gram beryllium metal powder. The mixture was made into small briquettes or pellets. The resulting pellets or briquettes were placed into the crucible of a high-frequency furnace, were provided with a substantial hydrogen blanket and were slowly heated to medium cherry red (about 700 centigrade) The beryllium metal reacted chemically and rather suddenly with platinum sponge to form a beryllium-platinum compound. As soon as the reaction was accomplished, the temperature was increased still in the presence of the hydrogen blanket until fusion and the even distribution of the beryllium-platinum compound within the liquid excess platinum was effected. The hydrogen blanket was then removed and air was allowed to enter the crucible. Oxidation of the small amount of beryllium (about0.0l6% per weight of metal) started instantly and was completed in about one or two minutes, due to the catalytic properties of the melt and also due to the substantial heat of formation for beryllium oxide (about 144 kilocal. per gram atom oxygen). The metal was cast into a graphite mold. After solidification the ingot was transferred to a furnace which was kept at a temperature of about 600 to 750 centigrade for a 30-minute soaking anneal. After such soaking anneal the ingot was hot forged or hot rolled, etc., and finally cold rolled or drawn in accordance with fabricating requirements, and with between anneals preferably at about 600-750 centigrade. This ingot carried the beryllium oxide dispersion in a concentration of about 0.75 gram equivalents per liter of metal.

Example II 10 grams fine platinum sponge powder were carefully mixed with 0.193 gram purified silicon (Si) powder. This mixture was wrapped into 25 grams platinum foil, about .001 thick (about 70 sq. inches foil). Such Wrapping was best accomplished by cutting the foil into three evenly sized pieces, by shaping one of these pieces into a little pouch to serve as a receptacle for the above silicon-platinum powder mixture, and by using the remaining two foil pieces as receptacles for the little pouch holding the silicon-platinum powder.

The resulting pack was placed into the crucible of high-frequency furnace. The crucible was provided with a hydrogen blanket andwas slowly heated to reaction temperature, about 700 centigrade. The reacted pack was permitted tocool under the hydrogen blanket.

The pre-alloy thus produced carried silicon in such an amount that when fused in the presence of air and with 7 42.5 grams pure platinum it pro-, duced a silica (SlOz) dispersion of about 0.75

gram equivalents per liter ofmetal.

742.5 grams platinum (it may be pure platinum ering was applied to the melt. The above prealloy pack was then added to the melt and was fused-under. the hydrogen covering until completely fused. The hydrogen blanket was then removed and air was allowed to act upon the melt. One to two minutes were required to produce the silica dispersion. The melt was finally cast in the usual way into a graphite mold and the resulting ingot was treated like the ingot as produced by the procedure of Example I.

Example III 2502s., or, 777.5 grams palladium sponge and 0.341 gram finely ground purified silicon were intimately mixed. The mixture was made into briquettes or pellets in the usual way. The pellets or briquettes were placed into the crucible of a high-frequency furnace, and were heated to medium-cherry red (about 700centigrade) under a hydrogen blanket to effect the chemical reaction between silicon and palladium. Still in presence of the hydrogen blanket the temperature was increased until complete fusion was efiected and the silicon-palladium compound was well dissolved within the melt. The hydrogen blanket was then removed and, air was allowed to enter the crucible. and to react with the melt. It is known that liquid palladium sorbs oxygen from the air to a higher. degree than liquid platinum. Therefore, silicon is rather rapidly changed into silica. It take approximately one minute to effect this change. To remove any excess oxygen from such. a melt, the melt was covered with a small amount of charcoal powder preceding the cast. The melt was cast into the usual graphite mold. After. solidification. the ingot was transferred to a furnace which was kept at a temperature of about 600. tov 700 ccntigrade for a 30-minute soaking, anneal. After such soaking anneal the ingot was allowed-to cool slowly in air for cold working.

Thepalladium ingot issuing from the above procedure carried the silica grain stabilizer in a concentration of about 0.75 gram equivalentsper liter of metal.

Example IV A mixture of 45.0 ozs. pure platinum sponge powder and 5.0 ozs. pure rhodium sponge powder were provided with .412 gram finely ground purifiedsilicon (Si). The silicon powder was intimately mixed into the platinum-rhodium sponge powders. This final mixture was made into briquettes in the usual way. The briquettes were placed into the crucible of a high-frequency furnace. In the presence of a hydrogen blanket the briquettes were heated to red heat (about 700 Centigrade). Thus the chemical reaction of silicon with the platinum metals was effected. Heating under the hydrogen blanket was continued until complete fusion of the constituents was accomplished, After such fusion the hydrogen blanket was removed and air was allowed to enterthe crucible. Oxidation of the silicon started instantly. After about one to two minutes the melt was cast into the usual graphite crucible (preceding casting the metal may be allowed to cool slightly within the crucible). After solidification the ingot was transferred to a furnace which was kept at a temperature of about 650 to 800 centrigrade for a -minute soaking anneal. After such soaking anneal the ingot was hot forged and hot rolled into wire of about .300" diameter. The wire was once more submitted to a soaking anneal for about 2 to 3 hours at about 650 to 800 centigrade, preferably by means of an electric furnace and in the presence'of air. After such soaking anneal the wire was allowed to cool slowly in air.

For further fabricating into wire for making catalyst gauze, the. above procedure was continued as follows: the .300" wire had its surface cleaned by pickling with dilute aqua regia which had incorporated some ammonium chloride. After such pickling cleaning the wire was cold rolled to the size of .150, was annealed once more for about three hours at about 650 to 800 centigrade in an electric muffle furnace, was allowed to cool in air, and was once more cleaned by means of pickling. Wire drawing was con-- tinued to the .025" size. At this stage another 3-hour anneal at about 650 to 800 centigrade was applied. This was the last between anneal. From this .025" size the wire was in the usual way cold drawn to the finishing size of .0024.

The metal of this wire carried a silica dispersion concentration of about 0.75 gram equivalents per liter of metal.

Example V 2 czs. (62.2 grams) pure platinum sponge powder and 0.422 gram thorium metal powder were carefully mixed and made into a tablet. The tablet was wrapped into platinum foil about .001" thick; this required another ounce of platinum. The resulting pack was heated in vacuum to about 650-750 centigrade for reaction. Such heating may either be accomplished by means of an electrically heated tube furnace, or, by means of a high-frequency vacuum furnace equipment. The reacted pack was allowed to cool in vacuum. 42 ozs. pure platinum sponge powder and 5 ozs. pure rhodium sponge. powder were intimately mixed. The mixture, was made into small. pellets by means of a power-operated pelleting machine. The resulting pellets were fed into. the crucible of a high-frequency furnace together with the above reacted pack and in a manner that. the pack was well covered by the, small pellets.

Fusion of the pellets and the reacted pack was accomplished in the presence of a substantial hydrogen blanket. After complete fusion the.

hydrogen blanket was removed and fusion was.

continued in the presence of air. Thorium was rather rapidly changed into thorium oxide due, to

the substantial heat of formation of ThOz. It. took approximately one minute to effect this.

change. The melt was cast in the usual way into a graphite mold. After solidification the ingot was treated in the same manner as the ingot of Example IV.

The metal of this ingot carrieda thorium oxide. dispersion acting as grain stabilizing agent in the concentration about one tenth (0.1) gram equivalents per liter of the alloy.

Example VI I 31 ozs. platinum sponge, 14 ozs. palladium sponge, and 5 ozs. ruthenium powder were mixed together. This mixture was providedwith about 0.500 gram finely ground purified silicon (Si). The silicon was intimately worked into the above platinum metal sponge mixture. The resulting mixture was made into pellets or briquettes. The pellets or briquettes were placed into quartz boats, were passed through a conveyor type furnace which was operated with a hydrogen atmosphere at a temperature of about 650 to 750 centigrade to effect reaction between the metal powders and the silicon. The reacted pellets-were placed into the crucible of a high-frequency furnace, were provided with a hydrogen blanket and fused.

After fusion the melt was exposed to air for oxidation, for about one to three minutes. Preceding casting the melt was allowed to coolslightly and was provided with small amount of charcoal powder to remove excess oxygen from the melt.

The ingot thus produced carried a silica dispersion of about 0.75 gram equivalents per liter of alloy, after solidification.

The ingot while still white hot was transferred from its graphite mold to a furnace held at the temperature of about 600 to 750 centigrade, and was kept there to slowly cool to this temperature and to be submitted to an additional anneal of at least half an hour. The ingot was then hot forged and hot rolled to about .100, in'case a sheet metal bar was to be made, with intermediate annealings at the above temperatures. After a final soaking anneal of about half an hour the sheet was allowed to cool slowly to room temperature for further cold working. I

Cold working was accomplished with strong individual passes and in a manner that reductions per pass were increased per each individual pass. Between anneals, total reductions of at least 75% and more were applied in case the alloy was required to be used for electrical contact points. Between anneals were made at about 600 to 750 centigrade and the metal was allowed to cool slowly to room temperature after each between anneal.

The foregoing examples illustrate some of the modifications of my invention in regard to commercial pure platinum such as is generally used for ware fabricating, for alloying, etc., the com-- mercial pure palladium which is usedfor alloy manufacture, for compact metal catalysts, etc., the high grade platinum and rhodium metals as used in the manufacture of those important platinum-rhodium alloys now generally used for gauze catalyst fabricating, and the pure platinum, pailadium, ruthenium metals which are used in the manufacture of those well-known ternary alloys for use in electrical contact fabrication. However, the invention is equally applicable to all the grades of the platinum metals, to the C. P. (that is, chemically pure and spectroscopically pure) platinum metals as well as to all commercial shades of these metals and alloys thereof. The invention is especially applicable to those alloys mentioned above, which are known as the most used platinum metal alloys of the present-day. But, it is also applicable to such platinum alloys and platinum metals which are modified by means of base metal constituents, such as wolfram, molybdenum, chromium, nickel, cobalt, iron, copper, etc. In this special case the base metals are incorporated into the already grain stabilized platinum metals and alloys thereof by means of fusion in presence of a hydrogen blanket, or by applying a vacuum.

It has also been found that the principle, methods and procedures as outlined above with regard to the metals of the platinum group and their alloys can also be applied to produce grain stabilized fine gold and gold alloys with metals of the platinum group, gold being in this case the principal ingredient. Also, such grain stabilized fine gold and gold alloys having themet-. als of the platinum group as minor ingredients may also be modified in the presence of a reducing atmosphere or by means of fusion in vacuum with any suitable type of basemetal The method of bringing the constituentstogether may be varied in manyother ways than as shown in the examples especially.the

nor in which the constituents which produce the I oxide dispersions during fusion in the presence of the oxidizing atmospheres (such as air, air enriched with oxygen, pure oxygen, or oxygen diluted by means of other gases than nitrogen, etc.) are initially reacted with the platinum metals preceding the final fusion procedure. Instead of effectingthe chemical reaction directly within the high-frequency furnace crucible in the presence of a hydrogen blanket, or, by means of a heat treatment in a conveyer furnace operated with a hydrogen or cracked ammonia gas atmosphere, the reaction may also be accomplished by means of a torch operating with a reducing flame, in vacuum, or it may be effected in the presence of argon, helium, etc. The most effective oxide dispersions are produced by means of the described chemical procedures when, preceding oxidation the constituents which are expected to produce the oxide dispersions, are most evenly distributed within the melts serving as medium to hold the dispersion.

Due to the oxidizing melting procedure of this invention whichrequires time to produce the oxide dispersion, it may happen that melts are sometimes cast in. an unduly overheated state with the known ingot defects resulting from overheated metal. Such ingots can, however, be remelted and cast in the required normal way without interfering with the state of the oxide dispersions effecting grain stabilization provided such remelting is accomplished in the absence of any flux. Such remelting can be done either in the presence of a hydrogen blanket when such remelting is applied for the purpose of making grain stabilized alloys having as constituents platinum metals and base metals (such as Wolfram, nickel, etc.), or,-in the presence of air, or by means of vacuum.

The grain stabilized platinum metals and al lcys thereof, and their modifications by means of base metal constituents, etc., as manufactured in accordance with the present invention have the same characterisics as those metal compacts which are made to carry heterogeneous inclusions and have them incorporated by way of the well-known powder metal methods. They have mechanical stability under sustained high heat and are, therefore, a superior type of material for making articles which require stability when used under great heat. With this heat stability they combine also a superior type of mechanical workability. Since in accordance with the present method grain stabilization can be well regulated regardless of the type of oxide dispersion used, the metals and alloys produced in accordance with this invention lend themselves well to fabricating those intricately shaped articles like electrical contact points, gauze catalysts, spinnerets, ware, etc. which are expected to perform supremely while under heat.

In accordance with the invention as disclosed heretofore, concentrations of dispersed oxides acting as grain stabilizers with the solidified metals are recited in the claims in gram-equivalents per 1000 cc. of the metal or alloy.

with p the; .:present invention, grainstabilization 15 f rmctals; is in .nor Way-r; limited to F this-type of oxidesq lt carr'beefiected-also byxmeans of :oxep ides which; are presentdn the: liquid :phase when thermetals, are in ;thefused ,state.

The termbetween-annealetemperaturesyit as I used in the claims-,arethose temperatures which; are known and'generally used for effecting. the; normal, recovery and relief- 0f metalsa after many. type-0f cold. or ,hot;work;-wvhen; they are. free. from grain 7 stabilizing: ioxides. 1-,

It will be --obvi ouscto thoseeskilled in itherart. that various -,changes may rbe zmade without deg; parting fromcthe spiritrzof :the iinventionnandi. therefore .theinvention-js notzrlimited to lWhflJ s described in xthecspecification .but' only.as.: in+; dicated in the appended claims.

I claim:

1. Ina process; forrproducing, ;a grain stabilized: metal: chosen ;-;from 1: the .rgroup consistingv :of 1

ruthenium; and mixtures; of these metals; the steps comprising-rinsing the-metalin the'absenoe of a fluxinggagent, incorporating into said fused metalqinpa non-oxidizing;iatmosphere :an; ole-- ment capable; lof .forming on oxidation.- at the fusion temperature of said .metal a non-volatile chemicallyi stable ,oxideiin an amount which will result in ,theiformation of betweenapproximate- 37 1 -02 etc 2.53; gramwequivalentssof the oxide of said, element gperiliterv of :said metal, effectingan even distribution .of said element in said f-used metal in the :presence of the non-oxidizing -at- 2. In a. process-in accordance with claim 1, the" additional steps of casting said dispersed system" into. an ingot, cooling said =hotingot to the'betweenanneahtemperature- -of -saidmetal,- and soaking said ingot at said temperature preceding the working of the ingotw 3. Ina process for-producingagrainstabilized metal chosenfrom-the group consisting-of platinum, iridium, A osmiumw palladium; rhodium,v

ruthenium- 4 and mixturesof these -meta-ls, :the"

steps comprising'fusing the metal in thea-bsence. of a fluxing agent,:-incorporating into said fused metal in the presence'of non-oxidizing atmospherean element capable-of forming on oxidation at the fusion temperaturegof said metal a non:, volatilechemicallystable oxide in theliquid state,

immiscible With'said-metalysaid element being. added in an amount whichwill result in the for-v mationof approximately-0.02 to 2.5 gramequiyrj,

alents of the oxide of said element per. one liter; of said metal, effecting an even distrihutioncf said element in saidfusedmetal in .the, presenc.e.:

of the non-oxidizing atmosphere, replacing-the.

non-oxidizing atmosphere in contact. withtsaid.

fused metal, by, an. oxidizing. atmosphere .whileg said metal is maintained-in thefusedsta-te; thereby converting said element to the oxide ,and'producinga colloidal:liquid-liquiddispersion of the:

oxide. of :said. element .in said fused "metal: WhiOhr:

acts as the immiscibleflispersion medium. :1,

4. In a-process'forproducinggagrain stabilized metal chosen'zfromwtheigroup .consisting of platemum. iridium, osmium,r-.;.palladium,

rhodiumw rutheniumend .mixtunes-zof ithese metals, the 7 stepsicomprisingrfusing the metal'in the absence of a fluxing agent, incorporating; into said fused metal in .the presence of a non-oxidizing. atmosphere an.element capable of "forming on oxida. tion at the fusion temperature of said metal a non-volatile, chemically stable oxide in the solid state, :said element'being added in an amount which Will result in the formation of approximately 0.02 to 2.5 gram equivalents of the oxide of said element per. one liter of said metal, effectingan even distribution of said element in said fusedmetal in the presence of the non-oxidizing atmosphere, replacing the non-oxidizing atmosphere in contact with said fused metal by an oxidizing atmosphere while said mixture is maintained-in the-fused state, thereby convertin said element to the oxide and producing a colloidal liquid-soliddispersion of the'oxide of said element in said fused-metal which acts as the dis- '2 persion medium therefor.

5. In a process in'accordancewith claim 4 wherein the amount-of said element to be added varies within the range specified approximately inverselyas the equivalent weight of the element .to be added whereby a greater amount of the element is required for an element-having a lower equivalent weight and a smaller amount of the element is required for an element having a higher equivalent Weight.

6. A grain stabilized metal consisting predominantly of a metal chosen from the group consistingof platinum;iridium,-osmiurn, palladium, rhodium,-ruthenium and mixtures of these metals, and approximately 0.02 to 2.5 gram equiva- ;1ents of a non-volatile, chemically stable oxide per liter of said metal, the constituents being in the state of a liquidcolloidal disperse system prior to solidification of the system in which the metal acts, in the fused state asthe dispersion =medium and the non-volatile chemically stable oxide is the dispersed part uniformly distributed in the dispersion medium.

7. A grain stabilized metal consisting of a metal chosen from the group consisting of'p'latinum,

iridium, osmium, palladium, rhodium, ruthenium,

and mixtures of these metals, and approximately 0.02 to 2.5 gram equivalentsv of a non-volatile, chemically stable oxide in liquid phase per liter of said metal at the fusion temperature of said metal which is immiscible with said metal the constituents being in thestate of a liquid-liquid colloidal disperse system priorv to solidification in which the metal acts in the fused state as the dispersion medium and the non-volatile chemically stable oxide acts in the fused immiscible state as the dispersed part uniformly. distributed in the dispersing medium.

8. A grain stabilized metal consisting of a metal chosenfrom the group consisting of platinum, iridium, osmium, palladium, .rhodium, ruthenium,

and mixtures of these metals, and approximately 0.02to 2.5 gram equivalents of a non-volatile, chemically stable oxide in 'solid phase per liter of said metalythe constituents being in the state .of a liquid-solidpolloidal' disperse system prior to solidificationdnwhich the "metal acts in the fused state as dispersion medium and the nonvolatilechemically stable oxide acts in the solid statevas the dispersed'p-art uniformly distributed in theidispersing'medium.

17 the grain stabilized metal in a non-oxidizing atmosphere.

10. In a process in accordance with claim 1, re-fusing the grain stabilized metal produced thereby in a non-oxidizing atmosphere, and adding a base metal chosen from the group consistingof Wolfram, molybdenum, chromium, beryllium, iron, nickel, cobalt, copper, silver and gold While maintaining the non-oxidizing atmosphere.

11. In a process for producing a grain stabilized metal chosen from the group consisting of platinum, iridium, osmium, palladium, rhodium, ruthenium, and mixtures of these metals, the steps comprising fusing the metal to be grain stabilized, applying a non-oxidizing atmosphere in contact with the fused metal, adding a prealloyed metal to the fused mass, said pre-alloyed metal comprising a small amount of said metal to be grain stabilized reacted in a non-oxidizing atmosphere with an element capable of forming on oxidation at the fusion temperature of the metal a non-volatile chemically stable oxide, maintaining the non-oxidizing atmosphere in contact with the mass until the pre-alloyed metal References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,406,172 Smithells Aug. 20, 19 16 2,539,298 Doty et a1. Jan. 23, 1951 FOREIGN PATENTS Number I Country Date 594,837 Great Britain Nov. 20, 1947 611,813 Great Britain Nov. 4, 1948

Claims

1. IN A PROCESS FOR PRODUCING A GRAIN STABILIZED METAL CHOSEN FROM THE GROUP CONSISTING OF PLATINUM, IRIDIUM, OSMIUM, PALLADIUM, RHODIUM, RUTHENIUM, AND MIXTURES OF THESE METALS, THE STEPS COMPRISING FUSING THE METAL IN THE ABSENCE OF A FLUXING AGENT, INCORPORATING INTO SAID FUSED METAL IN A NON-OXIDIZING ATMOSPHERE AN ELEMENT CAPABLE OF FORMING ON OXIDATION AT THE FUSION TEMPERATURE OF SAID METAL A NON-VOLATILE CHEMICALLY STABLE OXIDE IN AN AMOUNT WHICH WILL RESULT IN THE FORMATION OF BETWEEN APPROXIMATELY 0.02 TO 2.5 GRAM EQUIVALENTS OF THE OXIDE OF SAID ELEMENT PER LITER OF SAID METAL, EFFECTING AN EVEN DISTRIBUTION OF SAID ELEMENT IN SAID FUSED METAL IN THE PRESENCE OF THE NON-OXIDIZING ATMOSMOSPHERE, REPLACING THE NON-OXIDIZING ATMOSPHERE IN CONTACT WITH SAID FUSED METAL BY AN OXIDIZING ATMOSPHERE WHILE SAID METAL IS MAINTAINED IN THE FUSED STATE, THEREBY CONVERTING SAID ELEMENT TO THE OXIDE AND PRODUCING A COLLOIDAL DISPERSION OF THE OXIDE OF SAID ELEMENT IN SAID FUSED METAL WHICH ACTS AS THE DISPERSION MEDIUM.