US3622289A

US3622289A - Glass feeder made of pt-rh-mo high temperature-high strength alloy

Info

Publication number: US3622289A
Application number: US884689A
Authority: US
Inventors: James H Hansen; Ralph W Getz
Original assignee: Owens Corning Fiberglas Corp
Current assignee: Owens Corning
Priority date: 1969-12-12
Filing date: 1969-12-12
Publication date: 1971-11-23
Anticipated expiration: 1988-11-23

Abstract

This invention pertains to a glass feeder fabricated from an alloy containing 14-79 percent platinum, 20-85 percent rhodium and 0.01-10 percent molybdenum in which said molybdenum is present in an amount sufficient to increase the ductility of the alloy. This invention also pertains to a composite feeder comprising different platinum-rhodium and molybdenum alloys wherein the molybdenum content of these alloys are in an amount sufficient to maintain the resistivities of the alloys at the same magnitude when the feeder is in use at high temperatures.

Description

United States Patent James M. Hansen;

[72] inventors Ralph W. Getz, both of Newark, Ohio [54] GLASS FEEDER MADE OF PT -RH-MO HIGH TEMPERATURE-HIGH STRENGTH ALLOY 4 Claims, No Drawings [52] U.S.Cl 65/1, 65/374, 75/172 [51 Int. Cl C03b 37/02 [50] Fleld of Search 75/172; 65/1. 374

[56) References Cited UNITED STATES PATENTS 2,460,547 2/ 1 949 Stevens 65/374 X Primary ExaminerS. Leon Bashore Assistant Examiner- Robert L. Lindsay, .I r. Allorneys-Staelin and O'verman and Robert E. Witt ABSTRACT: This invention pertains to a glass feeder fabricated from an alloy containing 14-79 percent platinum, 20-85 percent rhodium and 0.01-10 percent molybdenum in which said molybdenum is present in an amount sufficient to increase the ductility of the alloy. This invention also pertains to a composite feeder comprising different platinum-rhodium and molybdenum alloys wherein the molybdenum content of these alloys are in an amount sufficient to maintain the resistivitics of the alloys at the same magnitude when the feeder is in use at high temperatures.

GLASS FEEDER MADE OF PT-RH-MO HIGH TEMPERATURE-HIGH STRENGTH ALLOY BACKGROUND OF THE INVENTION This invention relates to platinum-rhodium alloys and more specifically to a platinum-rhodium alloy having a third metal addition wherein its high temperature-high strength properties are greatly increased. A high rhodium alloy is very desirable because of its high melting properties thereby being capable of exposure to high operating temperatures during service operations.

High rhodium content alloys in the past have been demonstrated to be capable of being produced without difficulty by a normal vacuum melting process. Platinum-rhodium alloys comprising from 20-40 percent rhodium'are capable of being fabricated by a process of hot working followed by normal cold working. For example, in the case of sheet material, hot rolling is followed by cold rolling. Rhodium contents of more than 40 percent have been fabricated but they require more sophistication, e. g. powder techniques.

However, by increasing the rhodium content of these alloys their affinity for oxygen also increases, i.e. the oxygen solubility of the alloy increases thereby reducing the ductility of the alloy. Extreme care must be taken when using current production welding techniques (tungsten arc-inert gas shield) to prevent brittle welds. The chance of embrittlement due to oxygen absorption by these alloys is greatest during welding when the alloy is in the molten state.

During service operation at elevated temperatures. the ductility of a high rhodium alloy is reduced by increased oxygen solubility thereby creating a potential for premature failure of the alloy due to stress cracking. Weld failures have been noted on fabricated parts of a high rhodium alloy when exposed to high temperature.

To improve the high temperature ductility of a high rhodium content alloy and also assure weld integrity, the following high rhodium alloy system has been developed: platinum 14 to 79 percent, rhodium 20 to 85 percent and a third metal addition of from 0.0] to L percent, wherein good homogenization of the third metal addition is required.

The third metal additions are selected from the refractory or platinum group metals, such as for example, iridium, tungsten, rhenium and molybdenum and combinations thereof. Originally selected for use as solid solution strengtheners to yield a stronger alloy, these metals have been found to increase the high temperature ductility of high rhodium content alloys.

SUMMARY This high temperature-high strength alloy finds immediate use in the glass fiber industry in bushings and other standard high-temperature applications. The development of such an alloy has been prompted by the increased emphasis on higher melting glasses wherein high strength requirements forbushings are necessitated because of the higher operating temperatures, characteristic of these glasses.

Among the problems encountered when a bushing is in service are the volatilization losses of the alloy from the bushing and creep deformation of the bushing structure which decreases the efficiency and life of the bushing and which leads to lower quality glass fibers.

The advantage of using an alloy of the inventive concept includes a reduction in the precious metal volatilization losses from the bushing during service and improved strength characteristics of the alloy to reduce high temperature creep rates.

Molybdenum is the preferred third metal addition in the platinum-high rhodium content alloys of this invention because of their intended use in high-temperature resistant glass handling apparatus, although the other named third metal additions function in the same manner. Molybdenum is not known in the art to improve the ductility of a platinumrhodium alloy, so that the use herein of small percentages of molybdenum to improve the ductility of a platinum-rhodium alloy is totally unexpected and unobvious. Very small additions of molybdenum to a platinum-rhodium alloy make it possible to use rhodium in proportions as high as 20 to percent whereas in prior platinum-rhodium alloys, without molybdenum, the maximum practical rhodium content was limited to approximately 20 to 40 percent.

The percentage of molybdenum that is added to the platinum-rhodium alloy is based upon the rhodium content, i.e. as the latter is increased so is the former. However, the molybdenum content of the alloy should not exceed 1.0 percent by weight because of the potential of undesirable internal void formations developing during service applications which embrittles the alloy.

Some of the general characteristics of the alloy of this invention include improved tensile properties, slightly reduced oxidation losses of precious metal due to preferential oxidation of the third metal addition, improved high-temperature ductility, improved creep-rupture life, and improved weld integrity.

The ranges of proportions of the metals making up the alloys of this invention, expressed in weight percent, are:

platinum I 4-79 rhodium 20-85 third metal addition 0.0l l .0

The preferred ranges expressed in weight percent are:

platinum 29-59 rhodium 40-70 third metal addition 0.05-0.75

The preferred composition of the inventive alloy, expressed Alloys containing platinum and a high proportion of rhodium typically exhibit very brittle characteristics unless their purity is very high and their gas content very low. Even the highest purity alloys however, exhibit some brittleness especially after exposure to operating temperatures of l,800 F. to 2,750 F. Due to lattice changes with increasing rhodium content, high-rhodium alloys have a great affinity for gas, particularly oxygen. The addition of a third element, which forms a volatile oxide more readily than platinum or rhodium, tends to minimize the effects of impurities or dissolved gas on high rhodium content alloys. The effect of the third metal addition of high content rhodium alloys may be theorized by one of the following phenomena: l the third metal element ties up and carries away oxygen thereby preventing formation of a thin film of oxide on grain boundaries or (2) the third metal element ties up and carries away oxygen much faster than the diffusion of oxygen in the lattice network, thus preventing embrittlement or (3) the third metal element tends to further refine and degas the alloy during melting which results in improved properties, or (4) the third metal addition acts as an absorbing media for adsorbed and dissolved oxygen in the alloy. It is theorized that the third metal addition is converted to a volatile oxide which inhibits oxygen absorption into the alloy. Thus the ductility of the alloy is maintained and the high rhodium alloy may be welded and used in high temperature service applications.

It is therefore an object of this invention to provide a platinum-high rhodium content alloy capable of being fabricated into desired articles and capable of withstanding high operating temperatures.

It is another object to provide an alloy which is highly resistant to attack by molten glass and air, which has good creep'('reep is defined as deformation or elongation as a function of time at a uniform stress, usually at high temperatures.) resistance, good creep-rupture life"( Creep-rupture Life is defined as the time until fracture at a given temperature and stress), and which has high load carrying ability at elevated temperatures.

These and other objects will be readily apparent from the a homogeneous mix and uniform properties throughout the alloy, and especially to help distribute losses of the third metal addition by volatilization.

When a bushing structure is fabricated for use at high serfollowing detailed description which is intended only to illus- 5 vice temperatures, it is sometimes desirable to make a comtrate and disclose the invention. posite structure comprising different alloys having the same in a platinum-high rhodium content alloy, it is desirable to constituents but different proportions. For example, the body, have a minimum creep rate. good creep-rupture life and high tip section. and tips of a bushing structure may be fabricated strength at high operating temperatures. from platinum-high rhodium content alloys whose composi- Alloys comprising a very high rhodium content (at least 20 tions vary in order to meet specific operating temperatures. percent) find application where service temperatures are very More specifically a lower content of rhodium (20-25percent) high (2,700-2.800 F.) or in high stress applications at in a platinum-rhodium-X ternary system may be used in the moderate temperatures (2202.600 F.) to prevent excessive bushing body to help maintain proper bushing current disdeformation thereof. tribution and to maintain ductility whereas a higher content of It is known that rhodium is a good hardener for a platinum rhodium (up to 60 percent) in a platinum-rhodium-X ternary containing alloy, i.e. it is a good solid solution strengthener system may be used in the tip section to reduce the creep and forms a continuous solid solution. Rhodiums oxidation deformation of the composite structure. resistance approximates that of platinum and is therefore the Electrical resistivity plays an important role in the selection basis for selectingaplatinum-rhodium system. of alloys for fabrication into bushings and other apparatus The third metal addition to the platinum-rhodium y e where electrical current is passed therethrough. As the rhodiadds stability to the system in that it extends the operating life um content is altered in a platinum-rhodium system to obtain of articles fabricated therefrom. The third metal addition specific properties, the resistivity of the latter is altered. In forms an oxide more readily than platinum or rhodium and it order for these alloys having varying rhodium contents to be volatilizes during welding operations thereby maintaining the fabricated into composite bushings, Varying amounts of ductility of the alloy. Without the third metal addition, the molybdenum are added in Order to Obtain a certain resistivity. ll ld dil b b Oxygen d become b i l d That is, the composite structure requires the resistivities thereby be impossible to fabricate and would have a shorter thereof) approximately be of the Same magnitude- Therefore operating lif the resistivity of these alloys have been made to be a function Alloys comprising up to about 40 percent rhodium are comf R molybfienum content f h Importance ofthe mercially available but in order to increase alloy strength, the bemg of the S ame magmwd?S,bFcause,temperamre rhodium content must be increased. However, by increasing dllferenPals would anse as the f thereby the rhodium content, the ductility of the alloy is adversely afdecrefasmg the emcmncy of the fabricated amcle' such as a fected because of the oxygen absorption, hence the third bushmg' metal addition is employed in the inventive concept to remedy It has been observe? that the ,addmon f small of the Situation molybdenum to a platinum-rhodium alloy mcreasesthe con- The criteria for the third meta] addition) inc'ude a tact angle of the alloy. This charactenstic s critical in the a manufacture of glass fibers to prevent a condition known as Pi of formmg a d ox'de P L800 {hm flooding" from occurring. Contact angle is defined as 2 tan vfflauhzes faster than .pkmnum or ,rhodmm a modulus 40 h/x wherein It is the height of a molten bubble of glass on a higher than that plaunum or rhodlum Suitable particular substrate and x is the radius of the base of the bubstructure (4) a high valence state (7.8.9,), i.e. its free elec- Flooding is defined as the covering wetting of a avmlable for bondmg purpose-S to f h strate. such as the tip plate or sidewall of a feeder, housing hols rcs'sufnce and (5) mehmg low projections or tips, with molten glass which disrupts the wllhswnfj Semce temperatures formation of glass fibers. As the contact angle increases the A desired article or apparatus is usually made from our tendency toward fl di decreases, thereby di to a platinum-rhodium alloy be forging and rolling it into sheet more f i i operation, form. followed fabrication and However. thC alloy Fgllowing are some comparative properties for a platinumof this invention is capable of being cast into shapes i.e. slinger h di ll l) versus a l i h di l bcupsvspmnerenesietci denum alloy under various conditions. These examples are A double vacuum melting process is preferred when making shown by way of illustration and are not intended to be a articles for use in high temperature applications to help insure limitation of the inventive concepts.

Stress (load applied per Ru ture Percent Creep rate C I 0.02 111. life avg.) elongation (1n./in./hr.) omposition (p.s.i. (hrs. (avg.) (avg.) Control -{fifg f 1,000 3m 20. 0 4. 0x10- 1, 000 169. 5 10. 0 5.0X10" Example V weld properties Rh 1 1, 000 276. 9 20. 0 7.3)(10' Control i 1, 500 100.0 25. o 1.5x10- Example VI 1, 500 262. 8 12. 0 4.0)(10- Example VII 1, 500 421. 9 15. 6 2.8)(10 Stress (load applied per Ru ture Percent Creep rate 0.02 in life avg.) elongation (in./in./hr.) Composition (p.s.i. (hrs (avg.) (avg) Pt 40.00 Example VIII Rh 59.25 1, 500 398. 6 8. 2.1X10

Mo 0.75 Control g g,?,, 2,000 30.0 25.0 1.0 10-= Example IX 2, 000 58. 9 38. 0 6.8x 10- Example X 2, 000 45. 7 35. 0 1.2)(10- Example XI 2, 000 58. 0 19. 0 2.6)(10 Example XII 2, 000 37. 4 16. 0 2.0x 10- Example XIII 2, 000 136. 1 12. 0 9.6X10' Example XIV 2, 000 221. 0 10. 1 0.1 10- Example XV 2, 000 113. 3 12. 5 1 .12X-

Example XVI 2,000 154. 8 5. 6 4.9X10- Control 3, 000 10. 5 47. 0 2.5X10- Example XVI 3, 000 38. 4 20. 0 5.6)(10- Example XVIII 3, 000 51. 5 14. 6 2.46X10' The measurement of properties of the above examples was conducted at a temperature of 2,400 F.

A stress was applied to the alloys of each example in order to determine their rupture life, percent elongation and creep rate. The control was an alloy consisting of 75 percent platinum and percent rhodium. When the rhodium content was increased and the addition of various amounts of molybdenum made thereto, changes in the measured properties were observed.

Example I showed a large increase in rupture life, elongation and creep rate when compared to the control whereas example ll showed a slight increase in rupture life and a slight decrease in elongation and creep rate. What this shows, as well as the other examples is that a great degree of flexibility is provided in the various alloys, so that during fabrication of an apparatus. for example of a bushing used at high service temperatures, a single alloy or combinations thereof may be selected, depending upon the specific properties desired.

Composite bushing structures were fabricated from the platinum-rhodium-molybdenum ternary alloy systems of this invention, wherein the compositions for the sidewalls, tip plate, and tips were as follows, expressed in weight percents:

Platinum Rhodium Molybdenum Sidcwalls 75-85 [5-25 truce Tip plate 60-40 -60 up to L0 Tips 70-80 2040 truce sidewall, adapted for containing and controllably emitting a plurality of streams of molten glass for formation into glass filaments, fabricated from an alloy consisting essentially of platinum, rhodium and molybdenum, said molybdenum, being present in an amount sufiicient to increase the ductility of the alloy.

2. The feeder as claimed in claim 1 wherein the feeder is fabricated from an alloy comprising, by weight percent, platinum 29 59, rhodium 40 70, and molybdenum 0.05 0.75.

3. The feeder as claimed in claim 1 wherein the feeder is fabricated from an alloy comprising, by weight percent, platinum 40.0, rhodium 59.5, and molybdenum 0.5.

4. A composite glass feeder having a substantially uniform electrical resistivity, comprising sidewalls, and hollow projections located on a particular sidewall fabricated from different alloys having the same constituents, but in different proportions. consisting of:

l. a high temperature alloy for the sidewalls comprising platinum 75-85 percent by weight, rhodium l5-25 percent by weight, and a trace of molybdenum; a high temperature alloy for the particular sidewall comprising platinum 40-60 percent by weight, rhodium 40-60 percent by weight, and up to 1.0 percent by weight of molybdenum, said molybdenum being present in an amount sufficient to increase the ductility of the alloy; and 3. a high temperature alloy for the hollow projections comprising platinum -80 percent by weight, rhodium 20-30 percent by weight, and a trace of molybdenum; wherein the molybdenum content of said alloys are present in amounts sufficient to maintain the resistivities of the alloys at the same magnitude when the feeder is in use at high temperatures.

* i *0 I i

Claims

2. The feeder as claimed in claim 1 wherein the feeder is fabricated from an alloy comprising, by weight percent, platinum 29 - 59, rhodium 40 - 70, and molybdenum 0.05 - 0.75.
2. a high temperature alloy for the particular sidewall comprising platinum - 40-60 percent by weight, rhodium - 40-60 percent by weight, and up to 1.0 percent by weight of molybdenum, said molybdenum being present in an amount sufficient to increase the ductility of the alloy; and
3. a high temperature alloy for the hollow projections comprising platinum - 70-80 percent by weight, rhodium - 20-30 percent by weight, and a trace of molybdenum; wherein the molybdenum content of said alloys are present in amounts sufficient to maintain the resistivities of the alloys at the same magnitude when the feeder is in use at high temperatures.
3. The feeder as claimed in claim 1 wherein the feeder is fabricated from an alloy comprising, by weight percent, platinum 40.0, rhodium 59.5, and molybdenum 0.5.
4. A composite glass feeder having a substantially uniform electrical resistivity, comprising sidewalls, and hollow projections located on a particular sidewall fabricated from different alloys having the same constituents, but in different proportions, consisting of: