CA1184967A - Alloy wire for lamp components and lamps incorporating same - Google Patents
Alloy wire for lamp components and lamps incorporating sameInfo
- Publication number
- CA1184967A CA1184967A CA000397847A CA397847A CA1184967A CA 1184967 A CA1184967 A CA 1184967A CA 000397847 A CA000397847 A CA 000397847A CA 397847 A CA397847 A CA 397847A CA 1184967 A CA1184967 A CA 1184967A
- Authority
- CA
- Canada
- Prior art keywords
- filament
- alloy wire
- incandescent lamp
- lamp
- tungsten
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K1/00—Details
- H01K1/02—Incandescent bodies
- H01K1/04—Incandescent bodies characterised by the material thereof
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J7/00—Details not provided for in the preceding groups and common to two or more basic types of discharge tubes or lamps
- H01J7/14—Means for obtaining or maintaining the desired pressure within the vessel
- H01J7/18—Means for absorbing or adsorbing gas, e.g. by gettering
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01K—ELECTRIC INCANDESCENT LAMPS
- H01K1/00—Details
- H01K1/18—Mountings or supports for the incandescent body
Landscapes
- Discharge Lamp (AREA)
- Powder Metallurgy (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An alloy wire consisting essentially of a single phase solid solution of tungsten and about 0.2 to about 6 percent by weight tantalum includes grain controlling additives. The alloy wire may be used in lamps as a filament or as a gettering component and the additives consist essentially of from about 30 to about 200 parts per million potassium and less than about 100 parts per million silicon.
An alloy wire consisting essentially of a single phase solid solution of tungsten and about 0.2 to about 6 percent by weight tantalum includes grain controlling additives. The alloy wire may be used in lamps as a filament or as a gettering component and the additives consist essentially of from about 30 to about 200 parts per million potassium and less than about 100 parts per million silicon.
Description
D-22, 850 ALLOY WIRE FOR LAMP COMPONENTS AND LAMPS
INCORPORATING SAM:E
BACXGROUND OF THE INVENTION
The present invention relates to alloy wire, lamp components made therefrom and lamps incorporating the components.
U.S. patent 1,602,526 to Gero describes the doping of tungsten oxide powders with potassium to promote a recrystallized structure having elongated interlocking crystals.
U.S. patent 3~236,699 to Pugh et al relates to a tungsten-rhenium alloy doped with potassium in the form of a filament having good ductile properties and sag resistznce in the recrystallized state.
U.S. patent 3,748,519 to Martin et al relates to supports for tungsten filaments and gettering. An alloy disclosed therein includes 92.5 percent tantalum and 0.5 tungsten.
U.S. patent 1,508,241 to Pace describes a non-sag filament which uses oxides of tantalum or niobium as dopants in place of sodium potassium silicates to produce a non-sag filament.
SUMMARY OF THE INVENTION
The alloy wire composition of the present invention 2S has metallurgical properties which permit its use as various components in various types oF lamps. The metal-lurgical properties vary depending on the method of manufacture and use. The alloy wire may be used as a ~r~
D-22,850 non-sag filament, a vibration resistant filament, a filament support or getterins means.
In accordance with the present invention, there is provided an alloy wire consisting essentially of a single phase solid solution of tungsten and about 0.2 to about 6 percent by weight tantalum, said alloy including grain controlling additives uniformly distributed therein, said additives consisting essentially of from about 30 to about 200 parts per million potassium and less than about 100 parts per million silicon.
There is also provided a filament for an incandescent lamp, an incandescent lamp and method for making the alloy wire. The stability of the fine grain structure at temperatures up to at least 2200 degrees centigrade make it suitable for use in incandescent lamps requiring a vibration resistance filament. The recrystallized structure having elongated grains, is suitable for use in high temperature lamps requiring a sag resistance filament. Due to the inclusion of tantalum, the alloy of the present invention has properties which make i~
suitable for use as a gettering component in lamps, such as tungsten-halogen lamps.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates an incandescent lamp.
Figure 2 shows cross section of grain characteristics conventional tungsten wire annealed at 2300C.
Eigure 3 shows cross section of the grain character-istics of an alloy wire of the present invention annealed at 2300C.
DETAILED DESCRIPTION
The alloy of the present invention consists essentially essential of tungsten and from about 0.2 to about 6 percent by weight tantalum. More preferably tantalum is present in an amount from about 1 to about 4 percent by weight based on total weight of the alloy. The 9~i7 D-22,850 alloy is intentionally doped with grain controlling additives to promote the formation of a favorable grain structure. The additives are preferably present in amounts less than about 300 parts per million and consist essentially of from about 20 to about 200 parts per million potassium and less than about 100 parts per million silicon. Silicon is present primarily to aid in the retention of potassium during processing. It has been found that potassium is particularly desirable and is more preferably present in an amount from about 30 to about 100 parts per million based on the weight of the final alloy composition.
Minor impurities may deleteriously affect the desired properties of the final alloy. It is desirable to ~~~ 15 maintain the impurities at amounts less than about 100 parts per million and preferably less than about 50 parts per million by weight based on the total weight of the alloy. Typical impurities include aluminum, calcium, copper, iron, chromium, magnesium, manganese, nickel, tin, sodium and molybdenum. Impurities may be present despite all efforts to achieve high purity alloy material. It is most preferred that each of the impurities be less than about 5 parts per million.
The amount of minor ingredieDts including additives and impurities is based on the total weight of the alloy and is dependant on the metal source used, the temperature and time of sintering and other process steps. To achieve the desired level of dopant or additive in the final alloy, the amount of dopant employed in the presintered powder is at least equal to the amount desired in the final product and possibly up to 10 times the amount.
The alloys of the present invention are prepared by powder metallurgical techniques wherein component powders are intimately mixed to an extent to assure the homogenity ' ,, D-22~850 of the final alloy. The powder mix is compacted to form an ingot and the ingot is sintered under conditions which result in the formation of a single phase solid solution of tungsten and tantalum.
The sintered ingots are mechanically worked and fur-ther reduced in size by rolling, swagging, drawing and annealing to obtain a wire alloy having the desired metallurgical struct~re. According to one aspect of the present invention the alloy wire has a fine grain structure stable at a temperature of about 2300 centigrade. ~ccording to another aspect of the present invention, the fine grain structure is recrystallized to a grain structure having large grains extending in the longitudinal direction of the wire. A temperature of lS greater-than about ~500 degrees centigrade is needed to promote the recrystallization to the desirable large grain structure.
As compared with conventional wires of the type comprising tungsten doped with potassium, the alloy wire of the present invention retains thP fine grain structure at higher temperatures. Figure 2 illustrates the grain structure when conventional doped tungsten wire is annealed at 2300C to form large elongated grains. In Figure 3, the same anneal at 2300C does not result in the formation of a large grain structure ~ut instead retains a fine grain structure. The number of grains across the cross section of the wire is very l~rge. Retention of the fine grain structure at high temperatures is useful for lamp filaments requiring a vibration resistant structure.
At higher anneal temperatures; on the order oE 2500 degrees centigrade or greater, the fine grain structure of the alloy wire of the present invention may be recrystal-lized to a large grain structure similar to the structure shown in Figure 2. The grain growth proceeds primarily in ~4~
~-22,850 the longitudinal direction of the wire and results în coarse, interlocked grains and irregular grain boundaries which form, on the average, very small angles with the surfaces of the wire. This grain structure is effective in preventing sag in lamp filaments which is primarily offsetting of grains due to slip in grain boundaries forming large angles with ~he wire surfaces. The alloy of ! the present invention is ideally suited for sag resistant filaments for electronic lamps and tubes which are operated at temperatures above which recrystallization occurs.
In addition to the benefical metallurgical proper-ties, the inclusion of tantalum in the alloy of the pre-sent invention permits its use as lamp components which are operated at a suitable temperature to enhance the gettering properties of tantalum. It is known that tantalum reacts with oxygen; hydrogen and halides at high temperatures. It is theorized that the resulting com-pounds formed by tantalum gettering may further stabilize the alloy wire grain structure due to the formation of dispersed tantalum compounds which inhibit changes in grain structure.
In addition to the above properties, the alloy of the present invention possesses suitable ductility, tensile strength and electrical resistivity that contri-bute to the suitability for use as a component in a lamp.
Figure 1 is illustrative of an incandescent lamp and lamp components utili2ed therewith. The lamp has a hermetically sealed light transmitting envelope 2.
coiled fi~ament 6 is supported within the envelope 2 by a pair of lead-in wire 10 extending through the envelope 2 a~d sealed into the flat pinch 4. The filament 6 which spans the inner ends of the lead-in wires 10 is clamped at positions 14 and 160 Lead-in wires 10 have terminal portions 22 which protrude endwise from the outer end of '7 D-22,850 the lamp. Outwardly of the flat pinch 4, the terminal portions 22 of the lead-in wires 10 are bent back to form double-legged contact members 24. For purposes of illustration a filament support is shown at 26.
For applications requiring a vibration resistant filament, such as in automobile tail lamps, the fine grain structure of the present invention which is stable at filament temperatures up to 2200 degrees centigrade is particularly desirable when used as the filament compo-nent 8~
In halogen lamps the envelope 2 is filled with an inert gas, such as argon, nitrogen, krypton or mixture thereof, and a halogen additive such as bromine, for example, in the form of hydrogen bromide. The total pressure of the admixea halogen and inert fill gas may range from 2 to about 7 atmospheres, at room tempera-tures, depending on the fill gas composition, voltage, lumen and life ratings for which the lamp is designed.
The filament may be a coiled filament or a coiled coil filament which is operated at relatively high tem-peratures and which is desirably sag resistant. The elongated large grain alloy structure of the present invention is suitable for use in lamps of the halogen type and in lamps of the arc discharge type. When used as a filament in a halogen lamp, the alloy wire of the pre-sent invention is operated at temperatures above the temperatures at which the gettering properties of the alloy are most favorably utilized~
The gettering properties of the alloy of the present invention are utilized most effectively when the alloy is used as a lower temperature component of the lamp such as the lead-in wires 10 or filament support 26.
The alloy of the present invention prior to coi]ing - into filament typically has a tensile strength of from about 200 to 300 kilograms per square millimeter. More D-22,850 preferably, the tensile strength is greater than about 210 kilograms per square millimeter and most preferably greater than about 250 kilograms per square millimeter.
The relatively high tensile strength contributes to the use of the alloy for applications relating to halogen lamps and contributes to the workability OL the alloy material permitting the formation of wire.
Typically, the coefficient of expansion of the alloy of the present invention as measured at about 20C is from about 4.3 to about 4.5 cm./cm./C x 10-6 and more pre-ferably the coefficient of expansion is from about 4.3 to about 4.4 cm./cm./C x 10-6.
The alloy typically has an electrical resistivity of about 5.5 to about 6.0 microhm -cm. at 0C. Preferably the electrical resistivity is less than about 5.7 mi~rohm -cm. and more preferably less than about 5.6 microhm -cm.
For use in inc~ndescent lamps, the lead wire pre-ferably has a circular cross section with a diameter of from about 0.25 millimeters to about 0.81 millimeters.
The wire size depends to some extent on the power rating of the lamp with larger diameters being preferred for higher wattage lamps.
According to the process for preparing the alloy of the present invention, substantially pure tungsten powder doped with grain controlling additives consisting essen-tially of potassium and silicon is mixed with substan-tially pure tantalum powder, the resulting powder mix is compacted to form an lngot which is sintered in a hydro-gen atmosphere for a sufficient period of time and at a sufficient temperature to form a solid phase solution of tungsten and tantalum. The resulting ingot is mechani-cally worked into an alloy wire.
The dopants are preferably added to tungsten oxide - prior to reduction to the tungsten powder. The dopants , 35 may be in any convenient form of potassium, aluminum and '7 D-22,850 silicon such as silicon dioxide, alumina and potassium chloride. Potassium silicate is a preferred dopant since it serves as a source for both potassium and silicon. The percent by weight of aluminum in the doping compounds as expressed in terms of equivalent aluminum trioxide is pre-ferably about 0.04% by weight of tungsten oxide. The per-cent by weight of potassium in the doping compounds, as expressed in terms of equivalent potassium oxide i5 pre-ferably about 0.3% by weight of tungsten oxide. The percent by weight of silicon in the doping compounds, as expressed in terms of equivalent silicon dioxide, is preferably about 0.4~ by weight of tungsten oxide. After doping the chemically treated oxide is reduced to metallic tungsten by heating in hydrogen.
Pure tantalum powder milled to obtain a fine particle size on the order of a Fisher Sub-Sieve Size of from about 5.0 microns to about 14.0 microns is mixed with the doped tun~sten powder to produce powder blends having from about 0.2 to about 6 percent by weight tantalum.
The blending operation is performed so as to yield a very uniformly blended doped tungsten-tantalum powder.
The resulting doped tungsten-tantalum is presintered in an inert atmosphere at about 1300C. The ingot is next; sintered in an inert gas or hydrogen atmosphere by direct electric current resistance heating. The sintering is performed by a stepwise increase in current until a final tempera~ure of about 2900C is achieved. The final temperature is held for a sufficient period of time, typically on the order of about 15 minutes to achieve a single phase solution of tungsien and tantalum and densi-fication of ingot. It has been found that alloys of the present invention which have been sintered to at least about 90 percent, and more preferably to at least about 95 percent of their theoretical density ~as calculated by the 3~t7 ~-22,850 _g_ rule of mixtures) are sufficiently sintered to yield the solid solution.
The resulting ingot is mechanically worked ~y known methods using multiple swagging steps which successively reduce the cross-sectional area and intermediate annealing steps which improve mechanical workability. Annealing steps are preferably performed in a hydrogen atmosphere.
The material is further reduced by drawing, through a series of successive reductions.
EXAMPLE
A commercially available doped tungsten powder having an average particle size of about 4.2 microns, Sylvania AW
290, which is doped with potassium, aluminum and silicon.
About 400 grams of commercially pure tantalum powder/-KBI, Lot WlllO, particle size of about 7.2 microns and about 19.6 kilograms of the doped tungsten powder are mixed in a blender for about one hour~ A portion of the resulting mixture was compacted at a pressure of about 30,000 psi to foxm an ingot. The compacted ingot was presin ered at a temperature of about 1300~C in a vacuum at a pressure of about 1.3 x 10-2 pascals in a furnace~ The ingot or xod was direct resistance sintered at 2700 to 2900C for 15 minutes. The resulting density is about 17.6 g/cm3. The ingot was swaged to a diameter of about 3 mm at temperature of 1600C to 1300C and annealed at about 2200C at various intermediate sizes. Wire drawing from 3.3 mm diameter resulted in a size reduction to lamp wire sizes varying between 0.5 mm to 0.01 mm and was carried out at temperatures ~rom 1000C to 500C in several drawing steps. The tensile strength of the wire at 0.5 mm was 237 kg/mm2. Wire drawn to substantial smallex sizes for use as filament material will have tensile strength ranging from 220 to 400 kg/mm~ depending on the size and D-22,850 the proximity of that size to an in-process anneal.
Filament wires as small as 0.01 mm are common.
INCORPORATING SAM:E
BACXGROUND OF THE INVENTION
The present invention relates to alloy wire, lamp components made therefrom and lamps incorporating the components.
U.S. patent 1,602,526 to Gero describes the doping of tungsten oxide powders with potassium to promote a recrystallized structure having elongated interlocking crystals.
U.S. patent 3~236,699 to Pugh et al relates to a tungsten-rhenium alloy doped with potassium in the form of a filament having good ductile properties and sag resistznce in the recrystallized state.
U.S. patent 3,748,519 to Martin et al relates to supports for tungsten filaments and gettering. An alloy disclosed therein includes 92.5 percent tantalum and 0.5 tungsten.
U.S. patent 1,508,241 to Pace describes a non-sag filament which uses oxides of tantalum or niobium as dopants in place of sodium potassium silicates to produce a non-sag filament.
SUMMARY OF THE INVENTION
The alloy wire composition of the present invention 2S has metallurgical properties which permit its use as various components in various types oF lamps. The metal-lurgical properties vary depending on the method of manufacture and use. The alloy wire may be used as a ~r~
D-22,850 non-sag filament, a vibration resistant filament, a filament support or getterins means.
In accordance with the present invention, there is provided an alloy wire consisting essentially of a single phase solid solution of tungsten and about 0.2 to about 6 percent by weight tantalum, said alloy including grain controlling additives uniformly distributed therein, said additives consisting essentially of from about 30 to about 200 parts per million potassium and less than about 100 parts per million silicon.
There is also provided a filament for an incandescent lamp, an incandescent lamp and method for making the alloy wire. The stability of the fine grain structure at temperatures up to at least 2200 degrees centigrade make it suitable for use in incandescent lamps requiring a vibration resistance filament. The recrystallized structure having elongated grains, is suitable for use in high temperature lamps requiring a sag resistance filament. Due to the inclusion of tantalum, the alloy of the present invention has properties which make i~
suitable for use as a gettering component in lamps, such as tungsten-halogen lamps.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 illustrates an incandescent lamp.
Figure 2 shows cross section of grain characteristics conventional tungsten wire annealed at 2300C.
Eigure 3 shows cross section of the grain character-istics of an alloy wire of the present invention annealed at 2300C.
DETAILED DESCRIPTION
The alloy of the present invention consists essentially essential of tungsten and from about 0.2 to about 6 percent by weight tantalum. More preferably tantalum is present in an amount from about 1 to about 4 percent by weight based on total weight of the alloy. The 9~i7 D-22,850 alloy is intentionally doped with grain controlling additives to promote the formation of a favorable grain structure. The additives are preferably present in amounts less than about 300 parts per million and consist essentially of from about 20 to about 200 parts per million potassium and less than about 100 parts per million silicon. Silicon is present primarily to aid in the retention of potassium during processing. It has been found that potassium is particularly desirable and is more preferably present in an amount from about 30 to about 100 parts per million based on the weight of the final alloy composition.
Minor impurities may deleteriously affect the desired properties of the final alloy. It is desirable to ~~~ 15 maintain the impurities at amounts less than about 100 parts per million and preferably less than about 50 parts per million by weight based on the total weight of the alloy. Typical impurities include aluminum, calcium, copper, iron, chromium, magnesium, manganese, nickel, tin, sodium and molybdenum. Impurities may be present despite all efforts to achieve high purity alloy material. It is most preferred that each of the impurities be less than about 5 parts per million.
The amount of minor ingredieDts including additives and impurities is based on the total weight of the alloy and is dependant on the metal source used, the temperature and time of sintering and other process steps. To achieve the desired level of dopant or additive in the final alloy, the amount of dopant employed in the presintered powder is at least equal to the amount desired in the final product and possibly up to 10 times the amount.
The alloys of the present invention are prepared by powder metallurgical techniques wherein component powders are intimately mixed to an extent to assure the homogenity ' ,, D-22~850 of the final alloy. The powder mix is compacted to form an ingot and the ingot is sintered under conditions which result in the formation of a single phase solid solution of tungsten and tantalum.
The sintered ingots are mechanically worked and fur-ther reduced in size by rolling, swagging, drawing and annealing to obtain a wire alloy having the desired metallurgical struct~re. According to one aspect of the present invention the alloy wire has a fine grain structure stable at a temperature of about 2300 centigrade. ~ccording to another aspect of the present invention, the fine grain structure is recrystallized to a grain structure having large grains extending in the longitudinal direction of the wire. A temperature of lS greater-than about ~500 degrees centigrade is needed to promote the recrystallization to the desirable large grain structure.
As compared with conventional wires of the type comprising tungsten doped with potassium, the alloy wire of the present invention retains thP fine grain structure at higher temperatures. Figure 2 illustrates the grain structure when conventional doped tungsten wire is annealed at 2300C to form large elongated grains. In Figure 3, the same anneal at 2300C does not result in the formation of a large grain structure ~ut instead retains a fine grain structure. The number of grains across the cross section of the wire is very l~rge. Retention of the fine grain structure at high temperatures is useful for lamp filaments requiring a vibration resistant structure.
At higher anneal temperatures; on the order oE 2500 degrees centigrade or greater, the fine grain structure of the alloy wire of the present invention may be recrystal-lized to a large grain structure similar to the structure shown in Figure 2. The grain growth proceeds primarily in ~4~
~-22,850 the longitudinal direction of the wire and results în coarse, interlocked grains and irregular grain boundaries which form, on the average, very small angles with the surfaces of the wire. This grain structure is effective in preventing sag in lamp filaments which is primarily offsetting of grains due to slip in grain boundaries forming large angles with ~he wire surfaces. The alloy of ! the present invention is ideally suited for sag resistant filaments for electronic lamps and tubes which are operated at temperatures above which recrystallization occurs.
In addition to the benefical metallurgical proper-ties, the inclusion of tantalum in the alloy of the pre-sent invention permits its use as lamp components which are operated at a suitable temperature to enhance the gettering properties of tantalum. It is known that tantalum reacts with oxygen; hydrogen and halides at high temperatures. It is theorized that the resulting com-pounds formed by tantalum gettering may further stabilize the alloy wire grain structure due to the formation of dispersed tantalum compounds which inhibit changes in grain structure.
In addition to the above properties, the alloy of the present invention possesses suitable ductility, tensile strength and electrical resistivity that contri-bute to the suitability for use as a component in a lamp.
Figure 1 is illustrative of an incandescent lamp and lamp components utili2ed therewith. The lamp has a hermetically sealed light transmitting envelope 2.
coiled fi~ament 6 is supported within the envelope 2 by a pair of lead-in wire 10 extending through the envelope 2 a~d sealed into the flat pinch 4. The filament 6 which spans the inner ends of the lead-in wires 10 is clamped at positions 14 and 160 Lead-in wires 10 have terminal portions 22 which protrude endwise from the outer end of '7 D-22,850 the lamp. Outwardly of the flat pinch 4, the terminal portions 22 of the lead-in wires 10 are bent back to form double-legged contact members 24. For purposes of illustration a filament support is shown at 26.
For applications requiring a vibration resistant filament, such as in automobile tail lamps, the fine grain structure of the present invention which is stable at filament temperatures up to 2200 degrees centigrade is particularly desirable when used as the filament compo-nent 8~
In halogen lamps the envelope 2 is filled with an inert gas, such as argon, nitrogen, krypton or mixture thereof, and a halogen additive such as bromine, for example, in the form of hydrogen bromide. The total pressure of the admixea halogen and inert fill gas may range from 2 to about 7 atmospheres, at room tempera-tures, depending on the fill gas composition, voltage, lumen and life ratings for which the lamp is designed.
The filament may be a coiled filament or a coiled coil filament which is operated at relatively high tem-peratures and which is desirably sag resistant. The elongated large grain alloy structure of the present invention is suitable for use in lamps of the halogen type and in lamps of the arc discharge type. When used as a filament in a halogen lamp, the alloy wire of the pre-sent invention is operated at temperatures above the temperatures at which the gettering properties of the alloy are most favorably utilized~
The gettering properties of the alloy of the present invention are utilized most effectively when the alloy is used as a lower temperature component of the lamp such as the lead-in wires 10 or filament support 26.
The alloy of the present invention prior to coi]ing - into filament typically has a tensile strength of from about 200 to 300 kilograms per square millimeter. More D-22,850 preferably, the tensile strength is greater than about 210 kilograms per square millimeter and most preferably greater than about 250 kilograms per square millimeter.
The relatively high tensile strength contributes to the use of the alloy for applications relating to halogen lamps and contributes to the workability OL the alloy material permitting the formation of wire.
Typically, the coefficient of expansion of the alloy of the present invention as measured at about 20C is from about 4.3 to about 4.5 cm./cm./C x 10-6 and more pre-ferably the coefficient of expansion is from about 4.3 to about 4.4 cm./cm./C x 10-6.
The alloy typically has an electrical resistivity of about 5.5 to about 6.0 microhm -cm. at 0C. Preferably the electrical resistivity is less than about 5.7 mi~rohm -cm. and more preferably less than about 5.6 microhm -cm.
For use in inc~ndescent lamps, the lead wire pre-ferably has a circular cross section with a diameter of from about 0.25 millimeters to about 0.81 millimeters.
The wire size depends to some extent on the power rating of the lamp with larger diameters being preferred for higher wattage lamps.
According to the process for preparing the alloy of the present invention, substantially pure tungsten powder doped with grain controlling additives consisting essen-tially of potassium and silicon is mixed with substan-tially pure tantalum powder, the resulting powder mix is compacted to form an lngot which is sintered in a hydro-gen atmosphere for a sufficient period of time and at a sufficient temperature to form a solid phase solution of tungsten and tantalum. The resulting ingot is mechani-cally worked into an alloy wire.
The dopants are preferably added to tungsten oxide - prior to reduction to the tungsten powder. The dopants , 35 may be in any convenient form of potassium, aluminum and '7 D-22,850 silicon such as silicon dioxide, alumina and potassium chloride. Potassium silicate is a preferred dopant since it serves as a source for both potassium and silicon. The percent by weight of aluminum in the doping compounds as expressed in terms of equivalent aluminum trioxide is pre-ferably about 0.04% by weight of tungsten oxide. The per-cent by weight of potassium in the doping compounds, as expressed in terms of equivalent potassium oxide i5 pre-ferably about 0.3% by weight of tungsten oxide. The percent by weight of silicon in the doping compounds, as expressed in terms of equivalent silicon dioxide, is preferably about 0.4~ by weight of tungsten oxide. After doping the chemically treated oxide is reduced to metallic tungsten by heating in hydrogen.
Pure tantalum powder milled to obtain a fine particle size on the order of a Fisher Sub-Sieve Size of from about 5.0 microns to about 14.0 microns is mixed with the doped tun~sten powder to produce powder blends having from about 0.2 to about 6 percent by weight tantalum.
The blending operation is performed so as to yield a very uniformly blended doped tungsten-tantalum powder.
The resulting doped tungsten-tantalum is presintered in an inert atmosphere at about 1300C. The ingot is next; sintered in an inert gas or hydrogen atmosphere by direct electric current resistance heating. The sintering is performed by a stepwise increase in current until a final tempera~ure of about 2900C is achieved. The final temperature is held for a sufficient period of time, typically on the order of about 15 minutes to achieve a single phase solution of tungsien and tantalum and densi-fication of ingot. It has been found that alloys of the present invention which have been sintered to at least about 90 percent, and more preferably to at least about 95 percent of their theoretical density ~as calculated by the 3~t7 ~-22,850 _g_ rule of mixtures) are sufficiently sintered to yield the solid solution.
The resulting ingot is mechanically worked ~y known methods using multiple swagging steps which successively reduce the cross-sectional area and intermediate annealing steps which improve mechanical workability. Annealing steps are preferably performed in a hydrogen atmosphere.
The material is further reduced by drawing, through a series of successive reductions.
EXAMPLE
A commercially available doped tungsten powder having an average particle size of about 4.2 microns, Sylvania AW
290, which is doped with potassium, aluminum and silicon.
About 400 grams of commercially pure tantalum powder/-KBI, Lot WlllO, particle size of about 7.2 microns and about 19.6 kilograms of the doped tungsten powder are mixed in a blender for about one hour~ A portion of the resulting mixture was compacted at a pressure of about 30,000 psi to foxm an ingot. The compacted ingot was presin ered at a temperature of about 1300~C in a vacuum at a pressure of about 1.3 x 10-2 pascals in a furnace~ The ingot or xod was direct resistance sintered at 2700 to 2900C for 15 minutes. The resulting density is about 17.6 g/cm3. The ingot was swaged to a diameter of about 3 mm at temperature of 1600C to 1300C and annealed at about 2200C at various intermediate sizes. Wire drawing from 3.3 mm diameter resulted in a size reduction to lamp wire sizes varying between 0.5 mm to 0.01 mm and was carried out at temperatures ~rom 1000C to 500C in several drawing steps. The tensile strength of the wire at 0.5 mm was 237 kg/mm2. Wire drawn to substantial smallex sizes for use as filament material will have tensile strength ranging from 220 to 400 kg/mm~ depending on the size and D-22,850 the proximity of that size to an in-process anneal.
Filament wires as small as 0.01 mm are common.
Claims (28)
1. An alloy wire consisting essentially of a single phase solid solution of tungsten and about 0.2 to about 6 percent by weight tantalum, said alloy including grain controlling additives uniformly distributed therein, said additives consisting essentially of from about 30 to about 200 parts per million potassium and less than about 100 parts per million silicon.
2. An alloy wire according to claim 1 having a fine grain structure stable at a temperature of about 2300 degrees centigrade.
3. An alloy wire according to claim 2 consisting of from about 2 to about 4 percent by weight tantalum.
4. An alloy wire according to claim 1 having grain structure comprising large grains extending in the longi-tudinal direction of the wire.
5. An alloy wire according to claim 4 wherein said grain structure is formed by recrystallization of a fine grain structure at a temperature greater than about 2500 degrees centigrade.
6. A filament for an incandescent lamp consisting essentially of a single phase solid solution of tungsten and about 0.5 to about 6 percent by weight tantalum, said filament including grain controlling additives uniformly distributed therein, said additives consisting essentially of from about 30 to about 200 parts per million by weight potassium and less than about 100 parts per million by weight silicon.
7. A filament according to claim 6 having a fine vibration resistant grain structure, said grain structure being stable at filament operation temperatures up to at least 2200 degrees centigrade.
8. A filament according to claim 7 having a sub-stantially circular cross section and a diameter of from about 0.01 millimeters to about 0.5 millimeters.
9. A filament according to claim 8 having a coiled structure.
10. A filament according to claim 6 having a sag re-sistant grain structure comprising large grains extending in the longitudinal direction of the wire.
11. A filament according to claim 10 wherein said sag resistant grained structure is formed by recrystal-lization of a fine grain structure at a temperature greater than about 2500 degrees centigrade.
12. A filament according to claim 11 having a sub-stantially circular cross section and a diameter of from about 0.01 millimeters to about 0.5 millimeters.
13. A filament according to claim 12 having a coiled structure.
14. A filament according to claim 12 having a coiled coil structure.
15. An incandescent lamp comprising a light-trans-mitting envelope, a filament within said envelope, and lead-in wires connected to said filament and in sealing relationship with said envelope, said incandescent lamp including a lamp component as an alloy wire consisting essentially of a single phase solid solution of tungsten and from about 0.2 to about 6 percent by weight tantulum, said alloy including grain controlling additives uniformly distributed therein, said additives consisting essentially of from about 30 to 200 parts per million potassium and less than about 100 parts per million silicon.
16. An incandescent lamp according to claim 15 wherein said lamp compound has a fine vibration resistant grain structure, said grain structure being stable at temperatures up to at least 2200 degrees centigrade.
17. An incandescent lamp according to claim 16 wherein said lamp component comprises said lead-in wires.
18. An incandescent lamp according to claim 17 wherein said lamp component comprises said filament.
19. An incandescent lamp according to claim 17 wherein said lamp is a halogen lamp.
20. An incandescent lamp according to claim 15 wherein said lamp is a halogen lamp.
21. An incandescent lamp according to claim 20 wherein said lamp component comprises said filament; said filament having a sag resistant grain structure com-prising large grains extending in the longitudinal direc-tion of the wire.
22. An incandescent lamp according to claim 21 wherein said sag resistant grained structure is formed by recrystallization of a fine grain structure at a tem-perature greater than about 2500 degrees centigrade.
23. An incandescent lamp according to claim 22 wherein said filament has a coiled coil structure.
24. An incandescent lamp according to claim 20 wherein said lamp includes a gettering means; said get-tering means comprising lamp component.
25. An incandescent lamp according to claim 24 wherein at least one of said lead-in wires comprise said gettering means.
26. An incandescent lamp according to claim 24 wherein said gettering means comprises a filament sup-port.
27. A method of producing a tungsten-tantalum alloy wire comprising the steps of:
mixing substantially pure tungsten powder doped with grain controlling additives consisting essentially potassium and silicon and substantially pure tantalum powder, compacting the powder to form an ingot, sin-tering the ingot in a hydrogen or vacuum atmosphere for a sufficient period of time to form a solid phase solution of tungsten and tantalum, and mechanically working the resulting ingot into an alloy wire.
mixing substantially pure tungsten powder doped with grain controlling additives consisting essentially potassium and silicon and substantially pure tantalum powder, compacting the powder to form an ingot, sin-tering the ingot in a hydrogen or vacuum atmosphere for a sufficient period of time to form a solid phase solution of tungsten and tantalum, and mechanically working the resulting ingot into an alloy wire.
28. A method of producing a tungsten-tantalum alloy wire according to claim 27 wherein sufficient tantalum powder is mixed to give a resulting alloy wire consisting essentially of tungsten and from about 0.2 to about 6 percent by weight tantalum.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US24195981A | 1981-03-09 | 1981-03-09 | |
| US241,959 | 1981-03-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1184967A true CA1184967A (en) | 1985-04-02 |
Family
ID=22912898
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000397847A Expired CA1184967A (en) | 1981-03-09 | 1982-03-08 | Alloy wire for lamp components and lamps incorporating same |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0073814B1 (en) |
| JP (1) | JPS58500328A (en) |
| CA (1) | CA1184967A (en) |
| DE (1) | DE3268352D1 (en) |
| WO (1) | WO1982003138A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5148080A (en) * | 1990-01-16 | 1992-09-15 | Hilux Development | Incandescent lamp filament incorporating hafnium |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1508241A (en) * | 1917-02-20 | 1924-09-09 | Gen Electric | Metal and its manufacture |
| US1602526A (en) * | 1922-09-15 | 1926-10-12 | Westinghouse Lamp Co | Control of crystal development in refractory metals |
| US1854970A (en) * | 1930-05-20 | 1932-04-19 | Gen Electric | Electric lamp and the illuminating body used therein |
| US2225239A (en) * | 1936-08-14 | 1940-12-17 | Spaeth Charles | Filament |
| US3069584A (en) * | 1959-07-29 | 1962-12-18 | Jack W Frazer | Method of making tungsten filaments |
| US3210589A (en) * | 1960-04-28 | 1965-10-05 | Westinghouse Electric Corp | Electric incandescent lamp having filament of partially recrystallized fibrous structure |
| US3236699A (en) * | 1963-05-09 | 1966-02-22 | Gen Electric | Tungsten-rhenium alloys |
| US3346761A (en) * | 1965-07-02 | 1967-10-10 | Gen Electric | Incandescent lamp with a tungsten filament with tantalum imbedded in the surface to act as a gettering agent |
| US3748519A (en) * | 1971-10-06 | 1973-07-24 | Westinghouse Electric Corp | Tubular heat lamp having integral gettering means |
| US4020383A (en) * | 1975-12-31 | 1977-04-26 | Gte Sylvania Incorporated | Method of pulsing incandescent lamp filaments |
| US4296352A (en) * | 1979-12-19 | 1981-10-20 | General Electric Company | Incandescent lamp |
-
1982
- 1982-03-01 DE DE8282901088T patent/DE3268352D1/en not_active Expired
- 1982-03-01 EP EP82901088A patent/EP0073814B1/en not_active Expired
- 1982-03-01 WO PCT/US1982/000249 patent/WO1982003138A1/en active IP Right Grant
- 1982-03-01 JP JP50108782A patent/JPS58500328A/en active Pending
- 1982-03-08 CA CA000397847A patent/CA1184967A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| EP0073814A4 (en) | 1983-07-04 |
| EP0073814A1 (en) | 1983-03-16 |
| JPS58500328A (en) | 1983-03-03 |
| WO1982003138A1 (en) | 1982-09-16 |
| EP0073814B1 (en) | 1986-01-08 |
| DE3268352D1 (en) | 1986-02-20 |
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