US2048648A - Alloy and process for making same - Google Patents

Description

y o. FEUSSNER ET AL 2,048,648

ALLOY AND PROCESS FOR MAKING SAME Filed June 19, 1954 11v VENTORS 07 TO FEUSSNEE AL F/PED JEDELE ATTORNEYS Patented July '21, 1936 k H ALLOYAND rnocnss Foa G SAME Otto Feussner and Alfred Jedele,

Hanau-on-the-Maln, Germany I Application June 19, 1934, Serial No. 731,258. In fislglnm, France, and the Netherlands July 13,

- 15 Claims. for. 148-13) Our present application is a continuation in temperatures, they are tarnish-resisting and expart of our application Serial No. 622,568 filed hibit the surprising property of being improved inthe United States Patent Ofllce' July 14, 1932. by heat treatment to such a degree that an in- Our invention relates to alloys which are increase in hardness of 100% and even more is tended as substitutes for platinum, for instance easily attained. If, in the alloy, the gold is 5 in connection with dental work or for making v mostly or all substituted by copper, the alloys contacts of electrical apparatus etc. The inwhen heated in air to high temperatures will disvention consists oi? novel alloys of the above incolor in a degree increasing with'the increase in dicated class having special desirable properties copper content, but such alloys (containing a and also consists in a novel method of heatrelatively large proportion of copper) respond treating such alloys and thereby improving cermost easily to the process of heat treatment;

tain of their properties. they show a small initial hardness (natural hard- For the purposes indicated above, binary alloys ness, soft state) and very. great final hardness consisting of palladium and silverhave been used after the heat treatment, the increase in hard 1 to som extent, These binary alloys have a ness being quite considerable, exceeding 100% in greater resistance to corrosion and to tarnish many cases. 7 than silver and are also harder than silver. The tin which we incorporate in the above a1- However. even the hardest binary paliadiumloys as a special hardener should be used in prosilver alloy (with equal parts of silver and palportions not less than .5%' and not more than ladium) has a hardness only about twice the 5%. In some cases the metals used as the basis hardness of these two metals, which are very of the alloy may contain small proportions of soft. The Brinell hardness of either palladium metals of the plat num 811311903181 a P or silver alone is about 40 kilograms per square ladium, for instance ruthenium, rhodium, or millimeter and an alloy made of equal parts of platinum, up to 8%. or up to 3% of these other UNITED STATES PATENT OFFICE silver and palladium has a Brinell hardness of metals of the platinum group may be added inabout 80 kilograms per square millimeter. These tentionally; wi ou defeating the advantages of binary palladium-silver alloys can not be imthe present invention. The presence oi" these proved by heat treatment. If a ternary alloy other metals of the P g oup i increase is made by adding gold to the palladium and the natural or initial hardness of these alloys 3 silver, the resistance to corrosion, to mechanical and will also increase the final hardness which 3 action and to tarnish becomes very high but is obtained by the subsequent heat treatment. heat treatment does not improve these ternary In some cases it is desirable to lower the meltalloys any more than the binary alloys first ing point oi! the resulting alloys and to increase mentioned. If a ternary alloy is produced by their liquidity. We have found that when this adding copper to palladium and silver, such allowering of the m t po a d increase in loy, which is tarnish-resisting, will indeed show liquidity are desired, the addition of phosphorus some improvement in hardness when heat in proportions not less than 5% and not more treated. but such improvement is only very slight. than 4% will accomplish this result in connec- 40 If instead of copper alone, copper and gold are tion with the above alloys containing tin as a added to palladium and silver, the resulting alhardener. We have found that the addition of loys are of the same characteristics as the terphosphorus (preferably in the form of red phosnary palladium-silver-copper alloys; that is to phorus powder or phosphorus copper) generally say, heat treatment. or aging", will improve decreasesthe melting point of the alloys by about their hardness but slightly. 150 C. These alloys containing phosphorus 45 By systematic investigations we. have found have a very low viscosity and flow easily and freely that considerable improvement is obtained when into any cavity. They are especially suitable tin is added in making alloys containing palfor casting purposes, for instance in dental work. ladium, silver, and another'(fourth) constituent These phosphorus-containing alloys would be which consists either of copper or of gold or cast in the shape required for the dental work of both of these metals. In other words, the new in each particular case. These castings can be 5 alloys contain at least four metals, three of which adjusted or altered within slight limits, for inare palladium, silver and tin. These new alloys stance by filing, but can not be hammered or (if their fourth constituent consists of gold alone rolled. These phosphorus-containing castings u or of goldwith a small proportion of copper) can be improved by heat treatment in the same when heated in air do not discolor even at high I way as the tin-containing alloys of our invention containing no phosphorus, and with the same I 7 degree of increase in hardness.

hour at temperatures from 700 to 1000 C. and

are then quenched in water. The alloys are then in a soft condition, that is to say, they have only their natural hardness. .In this condition (if 7 they contain no phosphorus) the alloys can be easily worked and shaped into sheets, wires or any other form that may be desired for the particular use for which they are intended. From this soft, condition, the alloys are improved, and

particularly increased in hardness, by a heating or aging treatment conducted at temperatures ranging from iOO to 700 C. We have found that the structure of'the new alloys is altered considerably during the progress of, such heat treatment. When the alloys are in the soft state resulting ifrom annealing at 1000' C. and subsequent quenching, :their structure is one with large crystals having very distinct boundaries. If the alloys are then re-annealed or aged for a certain length of time. depending on the temperature employed for such ag'in'g, deposits or segregations will appear between the crystal boundaries, and itis these deposits or segregations which cause the increase in hardness. The lower this temperature is, the greater will be the length of time required to bring about these segregations: with a temperature of 600 C. about one hour will be sumcient, while with a temperatureof 500 0., about three hours will be required to produce these segregations. If the re-annealing or aging is then continued, especially at the relatively high temperature of 650 C., the boundaries of the crystals .disappear gradually and have vanished completely after a sufficient lapse of time, say about fourteenhours. The alloys are then of a very homogeneous structure and will exhibit a very minute-and uniform grain when pickled. The higher the temperature that is employed, (the more closely it approaches 700 C.) the shorter will be the 'time required to effect the homogenization of the alloy. It is well known that the size of the grain boundaries determines to a large extent the mechanical properties of any alloy; alloys with large grains are mechanically weaker than alloys with very minute grains. A heat treatment of an alloy which diminishes the size of the grains to the extent indicated above therefore transforms the alloy into a very valuable condition. We desire it to be understood, however, that evena relativelyshort aging treatment (say of one hour) will increase thehardness of the alloys considerably, but ductility of the alloys (as measured by resistance to repeated bending) is not fully developed by such short treatment. In all cases where a very even and smooth grain is required, the longer heat treatment as referred to above will be employed to produce a very homogeneoushard product ofincreased ductility.

The preferred proportions employed by us are as follows:

- Per cent Copper and/or gold to Palladium -to50 Silver 72 to Tin .5 to 5 When greater liquidity and the lowering of the melting point are desired as explained above,we

'ployed in ,these cases:

add to the above from no its: phosphorus. It will be understood that in addition to the ingredients Just mentioned. the alloys may contain small proportions of metals of the platinum group other than palladium, for instance ruthenium, rhodium," or platinum.

- The following examples indicate deflnit'e proportions which we have found to be particularly suitable in some cases and also set forth the particular heat treatment which we have em- Ezomple 1 An alloy consisting of of palladium, 50% of silver, 6% of gold, 4% of tin was produced by melting these ingredients .and cast to sheet bar. The bar was then annealed for one hour at 1000" C. and quenched in water thereby bringing it into the soft state. The bar was then rolled into a sheet of a thickness of 0.3 millimeters. The rolling operationwas generally conducted in a number of successive passes, and between each two passes the metal was subjected to an intermediate annealing at 1000 C. and quenched in water before the next rolling pass. After completion of the rolling operation the 'sheet was again annealed at 1000 C. and then quenched in water. The metal was then in a relatively soft state, as indicated by the fact that a strip of such sheet would breah after being bent 5000 times. Thereupon this soft sheet was aged for fourteen hours at 650 6., and its ductility and other propertieswere so much improved by'this aging treatment that it sustained 15000 bendings before breaking. 7

Example 2 A series of alloys were prepared each containing 2% 01' gold and 3% of tin, with the percentage of copper varying from 4 to 7%, that of palladium from 20 to 40% and that of silver from 71 to 48%.

kilograms per square millimeter as indicated in i Table I below. Then followed a re-annealing or aging for'one hour at 800 '0. followed by slow cooling whereby. the hardness of the alloy in the aged condition was increased considerably, ranging from 180 to 2'15 kilograms per square millimeter as likewise indicated in the following table;

Table! Soft v a d on Pd a; v

v .Kllognmpc 4 20 'n m is) s an '10 no an s so no. 145 as s .40 so, no an o 40 40 120 an 1 so as m m The increase .in by the palladium content is more than 40%. but is relatively small in such cases. For instance, when the alloy (with 2% gold and 8% tin) contains 5% 7 treatment of our invention is observed even when of copper, 50% of palladium and 40% of silver, it"

has a Brinell hardness of kilograms per square millimeter after the annealing treatment at 1000 C. for one-half hour followed by quenching in water (soft state), which hardness is increased to 135 kilograms per square millimeter by the aging treatment described above (annealing for one hour at 600 C. and slow cooling).

. We may decrease the copper content to 3% in the case of alloys containing 2% of gold and 3% tin. In such cases, however, the increase in hardness obtained by the aging treatment is considerable only when the palladium content of the alloy ranges from 30 to at palladium percentages below 30 and above 40, the increase in hardness obtained by the aging treatment is relatively slight as will be seen by the following table? It will be understood ment and the subsequent aging treatment in connection with alloys of Table II may be the same as described in connection with the alloys of Table 1, that is to say; annealing at 1000 C. for one'hali hour followed by quenching in water and reannealing or aging for one hour at 600 C. followed by slow cooling.

The addition of phosphorus in the proportion indicated (from .5 to 4%) is made to any one oi the alloys specified above whenever it is desired to reduce the melting point and the viscosity of the alloy while increasing its hardness beyond its natural hardness. The annealing, quenching and aging treatment may be exactly the same for a particular alloy whether or not phosphorus is added thereto. That is to say, if the alloy set forth in Example 1 is changed by simply adding phosphorus thereto within the range indicated, the treatment of such alloy would be exactly the same as described in connection with Example 1. The same remark will apply to the other examples. The addition of phosphorus lowers the melting point of the alloy very considerably and brings it down to the level of the melting point of gold or of gold alloys; this is a considerable advantage in certain cases, particularly for dentists.

The considerable and advantageous alterations in the structure of the material which the heat treatment according to our invention produces, are shown very clearly in the accompanying drawings which are reproductions of microphotographs taken from an alloy of the composition of Example treated according to our invention. These microphotographs were taken with an enlargement of 135 diameters. Fig. 1 shows the structure after annealing for one hour at 1000" C. and quenching; Fig. 2 shows the same alloy after re-annealing or aging at 600 C. for one hour; Fig. 3 shows the condition of the alloy after an aging treatment of seven hours at the temperature of 650 C., (instead of one hour at 600 C.) and Fig. 4 shows the same alloy after an aging treatment of fourteen hours at 650 C.

Where in the appended claims we use the expression "substantially consisting of about", we desire this to be interpreted as meaning that the alloys may'also contain other metals of the platthat the annealing treatinum group in minor amounts, and such substances, as for instance phosphorus, which do not materially change the properties of the alloys to be hardened by heat treatment, but do improve the alloys as to their natural hardness, melting point, liquidity, etc. Again, where in the ap? pended claims we use the expression from 5 to 10% of a constituent selected from the group consisting of gold and copper", we desire this to be interpreted in accordance with our specification, where we have stated that the preferred proportions employed by us include 5 to 10% of copper and/or gold; in other words, this 5 to 10% constituent may consist either of copper alone, or of gold alone, or of copper and gold together.

Various modifications may be made without departing from the nature 01' our invention defined in the appended claims.

We claim:

1. An age hardening alloy substantially consisting of about 20 to 50% of palladium, 72 to 30% of silver, from 5 to 10% of a constituent selected from the group consisting of gold and copper, and 0.5 to 5% of tin.

2. An age hardening alloy substantially consisting of about 20 to 40% of palladium, '71 to 48% of silver, 2% of gold, 4 to 7% of copper, and 3% of tin.

3. An age hardening alloy substantially consisting of about 40% of palladium, 48% of silver, 2% of gold, 7% of copper, and 3% of tin.

4. An age hardening alloy substantially consisting of about 20 to 50% of palladium, 72 to 42% of silver, 2% of gold, 3% of.copper, and 3% of tin.

5. A dental element in the form of a member cast in the shape required for the dental work in the particular case, said cast member having the character of an alloy set forth in claim 1.

6. A dental element in the form of a member cast in the shape required for the dental work in the particular case, said cast member having the character oi an alloy set forth in claim 1, in which the melting point of the liquid alloy is lowered and the liquidity increased by the addition of not less than 0.5% and not more than 4% phosphorus.

7. An alloy hardened by heat treatment and consisting substantially of about 20 to 50% of palladium, 72 to 30% of silver, from 5 to 10% of a constituent selected from the group consisting of gold and copper, and 0.5 to 5% of tin.

8. A dental element in the form of a member cast in the shape required for the dental work in the particular case, said cast member having the character of an alloy set'iorth in claim 1 and being hardened by heat treatment.

9. A dental element in the form of a member cast in the shape required for the dental work in the particular case, said cast member having the character of an alloy set forth in claim 1, in which the melting point of the liquid alloy is loweredand the liquidity increased by the addition of not less than 0.5% and not more than 4% of phosphorus, said dental element being hardened by heat treatment.

10. The process which consists in subjecting an alloy substantially consisting of about 20 to 50% of palladium, 72 to 30% of silver, from 5 to 10% of a constituent selected from the group consisting of gold and copper, and 0.5 to 5% of tin, to an annealing treatment at a temperature of from 700 to about 1000 C. and then quickly cooling the alloy thus heated, and thereupon aging it by heating to a temperature ranging from about 400 to 700 C.

alloy substantially consisting of about 40% of palladium, 48% of silver,'2% of gold, 7% of copper, 3% of tin, to an annealing treatment at a alloy substantially consisting or about 20 to 50% of palladium, 72 to 30% of silver, from 5 to of a" constituent selected from the group consisting ofgold and copper, and .5 to 5% of tin, casting I such alloy in the shape required for the dental work in the particular case, then heating such casting to a temperature within the range of about 700 to 1000 C., quickly cooling the casting, and thereupon aging it by heating to a temperature ranging from about 400 to 700 '3.

15. The process of producing a dental element which consists in producing'in the soft state, an i alloy substantially consisting of about to 50%; v of palladium, 72 to of silver, from 5 to 10% or a constituent selected from the group consistl5 ing of gold and copper, .5 to 5% of tin, and not temperature oi. from 700 to about 1000 C/and then quickly cooling the alloy thus heated, and thereupon aging it by heating to a temperature ranging from about 400 to 700 C.

13; The process which consists inv subjecting an alloy substantially consisting of about 20 to of palladium, '72 to 42% of silver, 2% of gold, 3% of copper, and 3% of tin, to an annealing treatment at a temperature or from 700 to about 1000 C. and then quickly cooling the alloy thus heated, and thereupon aging it by heating to a temperature ranging from about 400 to 700 C.

14. The process of producing a dental element which consists in producing in the soit'state, an

less than .5 and not more than 4% of phosphorus, casting such alloy in the shape required for the dental work in the particular case, then heating such casting to a temperature within 20 the range of about 700 to 1000 C., quickly cooling the casting, and thereupon aging it by heating to a temperature ranging from about 400 to 700 C.

ALFRED JEDELE.

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