MXPA00011487A - Tantalum-silicon alloys and products containing the same and processes of making the same - Google Patents

Abstract

An alloy comprising tantalum and silicon is described. The tantalum is the predominant metal present. The alloy also has a uniformity of tensile strength when formed into a wire, such that the maximum population standard deviation of tensile strength for the wire is about 3 KSI for an unannealed wire at finish diameter and about 2 KSI for an annealed wire at finish diameter. Also described is a process of making a Ta-Si alloy which includes reducing a silicon-containing solid and a tantalum-containing solid into a liquid state and mixing the liquids to form a liquid blend and forming a solid alloy from the liquid blend. Another process of making a Ta-Si alloy is described which involves blending powders containing tantalum or an oxide thereof with powders containing silicon or a silicon-containing compound to form a blend and then reducing the blend to a liquid state and forming a solid alloy from the liquid state. Also, a method of increasing the uniformity of tensile strength in tantalum metal, a method of reducing embrittlement of tantalum metal, and a method of imparting a controlled mechanical tensile strength in tantalum metal are described which involve adding silicon to tantalum metal so as to form a Ta-Si alloy.

Description

TANTALIO-SILICONE ALLOYS, PRODUCTS THAT CONTAIN THEM AND PROCESS TO PREPARE Field of the Invention The present invention relates to metal alloys, process for making them, and products made from and containing the alloy. More particularly, the present invention relates to alloys containing at least tantalum.

BACKGROUND OF INVENTION Tantalum has many uses in the industry, such as use in capacitor grade cables, deep drawing quality strips for making crucibles and the like, thin gauge strips, and other conventional uses. In the formation of the products that are going to be used in the industry, the mineral that it contains is obtained and converted into a salt which is then reduced to the form of a powder. The powder can be processed into an ingot, by melting it or the powder can be pressed and sintered to form the desired product. While the grades of tantalum currently available in the market have been acceptable to the industry, there has been a desire to improve the properties of tantalum, a tantalum rod has powder for metallurgy, it can have a wide range of tensile strengths Different in the product and / or metallurgical tantalum ingot can have large grain sizes which cause unwanted tantalum brittleness, especially when formed in small diameters as in the case of wire gauges. Accordingly, there is a desire to improve the consistency of the tantalum properties to overcome the disadvantages described above.

SUMMARY OF THE INVENTION, According to one aspect of the present invention, the present invention relates to a metal alloy containing at least tantalum and silicone, wherein the tantalum is the methyclic present with a higher percentage of weight in an alloy of metal. The alloy preferably has a uniformity of tensile strength when formed in a cable, so that the maximum standard deviation of tensile strength for the cable is about 3 KSI in an un-annealed cable in the final diameter and approximately 2 KSI for an annealed cable in the final diameter. The present invention further relates to various products made of the alloy such as bars, tubes, sheets, cables, capacitors and the like. The present invention also relates to a process for making a metal alloy containing at least tantalum / silicone, wherein tantalum is the metal with the highest percentage of weight in the metal alloy. The method includes the steps of mixing a first powder containing the tantalum, and an oxide thereof with a second powder containing at least silicone, an oxide thereof, or a silicone-containing compound to form the mixture. The mixture is then reduced to a physical condition such as by melting the mixture, and then a solid alloy is formed from the liquid condition. The present invention also relates to another process for making the alloy which includes the reduction in a liquid condition, either separately or together of a solid containing the silicone, and a solid containing the tantalum to form a liquid that It contains silicone, and liquid that contains tantalum. The two liquids are mixed together to form a liquid mixture and then the liquid mixture is formed into a solid alloy. The present invention further relates to a method for increasing the uniformity of tensile strength of the tantalum metal by softening it with silicone, or by introducing silicone into the tantalum metal in an amount sufficient to increase the uniformity of tensile strength in the tantalum metal. The present invention further relates to a method for reducing the brittleness of the tantalum metal which includes the steps of softening the tantalum metal with silicone or introducing silicone to the tantalum metal in an amount sufficient to reduce the brittleness of the tantalum metal. Finally, the present invention relates to a method for imparting a level of mechanically controlled tensile strength in the tantalum metal, softening the tantalum metal with silicone or introducing silicone to the tantalum metal and then annealing the tantalum metal to impart a resistance to controlled or desired mechanical stress in the tantalum metal. It should be understood that both of the above two descriptions, and the following detailed description are examples and only explain and are intended to provide a further explanation of the present invention, as it has been or claimed.

Detailed Description of the Invention. The present invention relates in part to a metal alloy ingot comprising at least tantalum and silicone. Tantalum, which is part of the metal alloy, is the main metal present. Therefore, among any other metals that may optionally be present, the highest percentage of weight of any of the metals present will be tantalum. Preferably, the weight percentage of the tantalum present in the alloy is at least about 50%, more preferably at least about 75% and even more preferably at least about 85% or at least about 95% , and even more preferably at least about 97% or from about 97% to about 99.5% or greater of tantalum. In the preferred embodiment, the alloy can also be considered as a microalloy tantalum with silicone. Silicone is present in low quantities. Preferably, the tantalum-silica alloy (or Ta-Si alloy) comprises from about 50 ppm by weight to about 5% by weight of elemental silicone, more preferably from about 50 ppm to about 1000 ppm of elemental silicone and even more preferably from about 50 ppm to about 300 ppm of elemental silicone based on the weight of the alloy. The alloy preferably has less than 1% by weight of elemental silicone present. The amount of silicone present in the alloy is generally an amount sufficient to increase the uniformity of the tensile strength of the resulting alloy compared to a tantalum metal that does not contain silicone. The alloy of the present invention may contain other additional ingredients such as other metals or ingredients generally added to the tantalum metal, such as ytterbium, zirconium, titanium and mixtures thereof. The types and amounts of these additional ingredients may be the same as those used with conventional tantalum and would be known to those skilled in the art. In one embodiment, the ytterbium present in the alloy is less than 400 ppm or less than 100 ppm or less than 50 ppm. Metals other than tantalum may be present and preferably comprise less than 10% by weight of the alloy; more preferably less than 4% by weight in alloy and still more preferably less than 3%, or less than 2% by weight of the alloy. Also and preferably, tungsten and molybdenum are not present in the alloy or substantially not present. Also, the alloy preferably has low levels of nitrogen present, such as less than 200 ppm and preferably less than 50 ppm and even more preferably less than 25 ppm and still more preferably less than 10 ppm. The alloy may also have low levels of oxygen present therein, such as less than 150 ppm, and preferably less than 100 ppm, and more preferably less than 75 ppm and even more preferably less than about 50 ppm. The alloys of the present invention can generally have any grain size including the grain size generally found in the pure or substantially pure tantalum metal. Preferably, the alloy has a grain size of from about 75μm to about 210μm and more preferably from about 75μm to about 125μm when heated to a temperature of 1800 ° C for 30 minutes. Also preferably, the alloy can have a grain size of from about 19μm to about 27μm when heated to a temperature of 1500 ° C for 2 hours. The alloy preferably has a uniformity of resistance to the alloy when it is formed into cables, so that the maximum standard deviation of population of tensile strength for the cable is about 3 KSI, more preferably about 2.5 KSI and even more preferably approximately 2.0 KSI, and more preferably still about 1.5 KSI or 1.0 KSI for the un-annealed cable in the finished diameter. The alloy also preferably has a standard deviation of maximum population of tensile strength for the cable of about 2 KSII, more preferably about 1.5 KSI, and still more preferably about 1.0 KSI, and even more preferably about 0.5 KSI for the recoded cable in the finished diameter. The alloys of the present invention can be made in different ways. In a preferred method, a first powder comprising the tantalum and an oxide thereof (eg, tantalum-containing solid) is mixed with a second silicone-containing powder or a silicone-containing compound. For purposes of the present invention, the silicone-containing solid is any solid which can be subsequently reduced to a liquid condition for imparting silicone to elemental in the tantalum metal. Examples of the silicone-containing compounds include, but are not limited to, elemental silicone powder, SIO2, glass beads and the like. In addition, the tantalum-containing solid is any solid material that contains at least tantalum which can be reduced to a liquid condition to form a tantalum metal. An example of a solid that ste * X 7 -'- * contains tantalum would be tantalum powder, or tantalum waste or the like. After the powders are mixed to form a mixture, the mixture is then reduced to a liquid condition by 5 methods such as casting. The manner in which the mixture is reduced to a liquid condition, such as by means of melting, can be carried out by any means. For example, casting can be performed by casting an electron beam, a recasting process vacuum arc, or plasma casting. Once the mixture has been reduced to liquid condition, then the liquid mixture can be allowed to form in or return to a solid state condition and form a solid alloy by any means including cooling in a crucible, such as a copper crucible cooled by water, or atomization (for example, gas or liquid atomization) and rapid and similar solidification processes. In this process, generally any amount of the compound containing silicone or elemental silicone can be used or introduced to the tantalum metal as the amount still results in the formation of an alloy based on the tantalum. Preferably, the powder mixture once formed, contains from about 0.01% by weight up to about 25% by weight, more preferably from about 0.5% by weight to about 2.0% by weight, and more preferably from about 0.80% by weight to about 1.2% by weight of elemental silicone, based on the weight of the total mixture. As stated above, this mixture may additionally contain other ingredients, additives or softeners such as those generally used in tantali or conventional metals, such as ytterbium, zirconium, titanium or mixtures thereof. In the preferred embodiment of the present invention, the mixture is reduced to a solid condition by means of electron beam casting (in a vacuum) wherein the mixture can be melted in any range, including a range of from about 90.72 kgs. . per hour, up to approximately 287.52 kgs. per hour using for example a Leybold EB furnace of 1200 KW which can melt into 25.4cm ingots. to 3.48cm. , any ingot size can be made depending on the furnace type EB and S J cooling capacity. Preferably, the subsequently formed alloy is reduced to the liquid or molten condition more than once, and preferably at least two or more times. When melted at least twice, the first casting is preferably in a casting range of approximately 181.44 kgs. per hour, and the second smelter is preferably in a casting range of approximately 287.52 kgs. per hour. Therefore, the alloy once formed, can be reduced to a liquid condition any number of times to subsequently result in a more purified alloy, and to help in the reduction of silicone levels in the desired ranges of the final product, since that the silicone or silicone-containing component can be added excessively. The alloy resulting from the above-described process may contain the amounts of elemental silica described above and preferably contain from about 50 ppm to about 5% by weight and more preferably less than 1% by weight of elemental silicone based on the weight of the alloy. Another process for the manufacture of the alloy of the present invention comprises the reduction to a liquid condition of a solid containing silicone, and a solid containing tantalum. In this process, the solid containing silicone can be reduced to the liquid condition separately and the solid containing tantalum can be reduced to the liquid condition separately. Then, the two liquid conditions can be combined together. Alternatively, the solid containing silicone and the tantalum-containing solid can be added together as solids and subsequently reduced to a liquid condition. Once the solid containing silicone and the tantalum-containing solid are reduced to a liquid condition by methods such as casting, the two liquids are mixed together to form a liquid mixture which is subsequently formed into a solid alloy. As in the process described above, additional ingredients, additives and / or softeners can be added during the process. The silicone or the silicone-containing compound may alternatively be introduced in the form of a gas, and "dripped" into the melting chamber or crucible. The present invention also relates to a method for increasing the uniformity of the tensile strength in the material comprising the tantalum metal. As stated above, the tantalum metal especially when formed in bars or similar forms can have a large variation in mechanical properties such as tensile strength, in the entire length and / or width of the bar. With the alloys of the present invention, the uniformity of the tensile strength in the tantalum metal is improved compared to the tantalum metal which does not contain silicone. In other words, the variation or standard deviation of the tensile strength can be reduced in the alloys of the present invention. Accordingly, the uniformity of the tensile strength in the tantalum metal can be increased, softened and added to the tantalum metal in a manner such as to form a Ta-Si alloy which has an increased or improved strength uniformity. to the voltage compared to the tantalum metal that does not have silicone present, especially when the tantalum is formed in cables or strips. The amount of silicone present in the tantalum metal would be the same as explained above. The standard deviation of the tensile strength can be decreased by a number of times using tantalum metal containing silicone. For example, the standard deviation of the tensile strength can be reduced by about 10 times or more compared to a tantalum metal that does not contain silicone. Preferably the standard deviation is reduced by at least 10% or more, preferably at least 25%, and more preferably by at least 50% compared to a tantalum metal which does not have the silicone present. In a similar way, the brittleness of the tantalum metal can be reduced by forming a Ta-Si alloy compared to the melted tantalum without silicone present, or the metallurgical powder tantalum if no silicone is present. In addition to these advantages, the present invention is further related to a method for imparting a level of controlled mechanical stress resistance to the tantalum metal. In greater detail, based on the amount of silicone present in the Ta-Si alloy, and the annealing temperature used in the alloy, controlled specific stress resistance ranges can be imparted to the alloy. For example, a higher annealing temperature will lead to a lower tensile strength in the alloy. In addition, a greater amount of silicone present in the alloy will lead to a higher tensile strength in the alloy. Therefore, the present invention allows a desired particular tensile strength in a tantalum metal to be controlled, or "programmed" based on these variables. The annealing temperatures that help in the determination of the level of resistance of the controlled mechanical tension in the tantalum metal is preferably the last annealing performed in the Ta-Si alloy. This last annealing of the Ta-Si alloy is annealed which controls more in determining the level of strength of the particular mechanical stress in the tantalum metal. Generally, the Ta-Si alloy can be annealed at any temperature which does not result in the casting of the alloy. Preferred annealing temperature ranges (eg, intermediate or final annealing) are from about 900 ° C to about 1600 ° C, and more preferably from about 1000 ° C to about 1400 ° C, and even more preferably from about 1050 ° C. C hast at approximately 1300 ° C. These annealing temperatures are based on annealing for a time from about 1 to about 3 hours, preferably about 2 hours. Therefore, if it is desired to obtain a lower tensile strength (eg, 144.3 KSI), intermediate annealing should be done at a temperature of about 1200 ° C. If a higher tensile strength (eg, 162.2 KSI) is desired, in the tantalum metal, intermediate annealing would be performed at a temperature of about 100 ° C.

Once the alloy is formed, the Ta-Si alloy can be subjected to any additional process such as any conventional tantalum metal. For example, the alloy can be subjected to forging, stretching, rolling, swaging, extruding, tube reduction, or more than one of these or other steps of the process. As indicated above, the alloy can be subjected to one or more annealing steps, especially depending on the particulate form and final use of the tantalum metal. The annealing temperatures, and the times of the Ta-Si metal processing, are those described above. Therefore, the alloy can be formed into any shape such as a tube, a bar, a sheet, a cable, a rod, and a deep drawing component, using techniques known to those skilled in the art. The alloy can be used, in capacitor and furnace applications and other applications for metals where fragility is a consideration. The present invention will be further elucidated by means of the following examples, which are intended to be purely examples of the present invention.

EXAMPLES A tantalum powder reduced to sodium was used, which had the following characteristics: The ingot had the following impurities (ppm): Manganese Coal < 5 Oxygen 80 Tin < 5 Nitrogen < 10 Nickel < 5 Hydrogen < 5 Chrome < 5 Niobium < 25 Sodium < 5 Titanium < 5 Aluminum < 5 Iron 15 Molybdenum < 5 Copper < 5 Zirconium < 5 Cobalt < 5 Magnesium 5 Boron < 5 Tungsten < 5 To this tantalum powder was added 1% by weight of Si (in the form of a reactive grade elemental silicone powder) based on the weight of the mixture. The mixed powder was then subjected to an electron beam casting in a Leybold EB 1200 KW furnace using a melting range of 100,926 kgs. / hrs. Once the powders were mixed, the alloy was allowed to form into a solid, and was remelted back into the electron beam using a melt range of 268.5312 kgs / hrs. The formed alloy had silicone present in a range of from approximately 120 ppm Si to approximately 150 ppm Si. The formed alloy was machined, and subjected to rotary forging to form a 10.16cm bar. and cleaned by machining. Then this bar was annealed at a temperature of 1530 ° C for two hours. Subsequently the bar was subjected to 5 additional intermediate anneals at a temperature of 1300 ° C for two hours, while this bar was being rolled and stretched to a diameter of 0.2 mm. and to a cable with a diameter of 0.25 mm, where a part of each cable was braided to a temperature of approximately 1500 ° C to 1600 ° C in three different speeds (10,668 m / min., 9,144 m / min. 7.62 m / min.), While the remaining sample of the cable was not recossed. The sample was compared, with an un-annealed metallurgical powder Ta metal formed in the same manner but without the addition of silicone. The tested cable samples had the following resistance to the final stress measured by ASTM E-8.

TABLE 1 Resistance to Final Tension (RSI) Ta Non-annealed Alloy Ta-Si Average Diameter Range ZSD 0.2 mm 132 122/142 130.0 124.3 133.8 0. 25 mm 133 123/143 120.6 134.6 130.4 Bending tests were also applied to the samples and to the wire of the alloy of the present invention, which successfully withstood the cracks through sintering at a temperature of 1950 ° C for 30 minutes. Example 2 A tantalum and a powder with a silicone content are prepared and formed in an ingot following the process of Example 1. The tantalum ingot was melted by electrons (as in Example 1, except that the melting range illustrated in Table 2 was used) in five sections. The amounts of silicone indicated in Table 2 below are the amounts of silicone present in the alloy. TABLE 2 The amount of silicone present in the tantalum metal was subsequently determined by means of emission spectrography.

It was discovered, that the metal having 0.5% by weight of added silicone results in Si levels reduced significantly from about 30 to about 60 ppm and a reduction in the Briner hardness number (BHN) of 1 2 points. compared with the sample with 1.0% by weight of silicone.

Samples (section 3) that have 1.0% silicon added gave as a result, if uniformly retained at both surface levels (138 to 160 ppm) and internally (125 to 200 ppm). Samples with decreased casting range resulted in a slight increase in Si retention at the surface (135 to 188 ppm) and internally (125 to 275 ppm). In each case, the hardness of the alloy was very uniform, presenting a BHN average of 14 with a range of 103 to 127.

Example 3. The wire sample was prepared following the procedure of Example 1, except that the intermediate and final annealing temperatures were adjusted as illustrated in Table 3 below. The final intermediate annealing temperature was also for two hours. TABLE 3 As can be seen from the results in Table 3, the Ta-Si alloy has a much lower standard deviation in tensile strength. Also, the variation in l at annealing temperature shows the ability to control the range of tensile strength. Other embodiments of the present invention may be appreciated by those skilled in the art from the consideration of this description and the practice of the present invention. It is intended that the description and examples be considered only as examples, and the scope and spirit of the present invention being indicated by the appended claims. , ^

Claims (2)

1. R E I V I N D I C A C I O N S Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property: 1 . An alloy based on tantalum which comprises tantalum and silicone, where the tantalum is the highest percentage of weight of metal present, and said alloy has a uniformity of tensile strength when formed in a cable, so that the standard deviation Maximum population tensile strength for the cable is approximately 3 KSI, for an un-annealed cable in its final diameter, and approximately 2 KSI for an annealed cable in its final diameter.
2. 2. The alloy as described in Claim 1, further characterized in that said alloy comprises from about 50 ppm by weight to about 5% by weight of elemental silicone, based on the weight of said alloy. . The alloy as described in Claim 2, further characterized in that said alloy comprises from about 50 ppm to about 1000 ppm elemental silicone based on the weight of said alloy. The alloy as described in Claim 2, further characterized in that said alloy comprises from about 50 ppm to about 300 ppm of elemental silicone based on the weight of said alloy. The alloy as described in Claim 2, further characterized in that said alloy comprises less than 1% by weight of elemental silicone, based on the weight of said alloy. The alloy as described in Claim 1, further characterized in that it additionally comprises ytterbium, zirconium, titanium and mixtures thereof. The alloy as described in Claim 1, further characterized in that said alloy has a grain size from about 75μm to about 210μm when heated to a temperature of 1800 ° C for 30 minutes. The alloy as described in Claim 1, further characterized in that said alloy has a grain size from about 19 to about 27μm when heated at a temperature of 1530 ° C for 2 hours. The alloy as described in Claim 1, further characterized in that said maximum standard deviation is about 2 KSI for an un-annealed cable. . The alloy as described in Claim 1, further characterized in that said maximum standard deviation is about 1 KSI for an un-annealed cable. . The alloy as described in Claim 1, further characterized in that said maximum standard deviation is about 1 KSI for an annealed cable. A tube comprising the alloy as described in Claim 1. A sheet or bar comprising the alloy as described in Claim 1. A cable comprising the alloy as described in Claim 1. . A capacitor component comprising the alloy as described in Claim 1. . The alloy as described in Claim 1 further characterized in that said alloy has less than 10% by weight of metals present other than tantalum. . A process for making an alloy comprising tantalum and silicone, said process comprising: Mixing a first powder comprising tantalum, and an oxide thereof with a second powder comprising silicone or a compound containing silicone to form a mixture . The reduction of said mixture to a solid condition by means of casting; The formation of a solid alloy from said liquid condition. The process as described in Claim 17, further characterized in that said mixture comprises from about 0.01% by weight to about 25% by weight of elemental silicone. The process as described in Claim 17, further characterized in that said mixture comprises from i * 'about 0.5% by weight to about 2.0% by weight of elemental silicone. 20. The process as described in Claim 17, further characterized in that said mixture comprises from about 0.80% by weight to about 1.2% by weight of elemental silicone. twenty-one . The process as described in Claim 17, 10 further characterized in that said mixture additionally comprises ytterbium, zirconium, titanium or mixtures thereof. 22. The process as described in Claim 17, further characterized in that said reduction of the mixture to a The liquid phase comprises the melting of said mixture. 23. The process as described in Claim 17, further characterized in that said casting is an electron beam casting. 24. The process as described in Claim 17, further characterized in that said casting is by plasma. 25. The process as described in Claim 17, further characterized in that the casting is by remelting of vacuum arc. 26. The process as described in Claim 17, further characterized in that it additionally comprises reducing said solid alloy to a liquid condition, and re-forming said solid alloy. 27. The process as described in Claim 17, further characterized by comprising subjecting said solid alloy to forging, drawing, rolling, welding, extrusion, tube reduction or combinations thereof. 28. The process as described in Claim 17, further characterized in that it additionally comprises annealing said solid alloy. 29. The process as described in Claim 17, further characterized in that said solid alloy comprises from about 50 ppm to about 5% by weight of elemental silicone. 30. A process for making an alloy comprising tantalum and silicone comprising said process the steps of: reducing to a liquid phase, together separately, a solid comprising silicone and a solid comprising tantalum to form a liquid containing silicone and containing tantalum; the mixture of the silicone-containing liquid and the tantalum-containing liquid to form a liquid mixture; the formation of a solid alloy from said liquid mixture. 31 The process as described in Claim 30, further characterized in that said mixture comprises from about 0.01% by weight to about 25% by weight of elemental silicone. 32. The process as described in Claim 30, further characterized in that said blend comprises from about 0.5% by weight to about 2.0% by weight of elemental silicone. 33. The process as described in Claim 30, further characterized in that said mixture comprises from about 0.80% by weight to about 1.2% by weight of elemental silicone. 34. The process as described in Claim 30, further characterized in that said mixture comprises ytterbium, zirconium, titanium or mixtures thereof. 35. The process as described in Claim 30, further characterized in that said reduction of the mixture to a liquid phase comprises the melting of said mixture. 36. The process as described in claim 35, further characterized in that said casting is electron beam casting. 37. The process as described in Claim 35, further characterized in that said casting is by plasma. 38. The process as described in claim 35, further characterized in that the casting is by remelting of vacuum arc. 39. The process as described in Claim 30, further characterized in that it additionally comprises reducing said solid alloy in a liquid condition and re-forming said solid alloy. 40. The process as described in Claim 30, further characterized by comprising subjecting said solid alloy to forging, drawing, rolling, swaging, extruding, tube reduction or combinations thereof. 41 The process as described in Claim 30, further characterized by additionally further comprising annealing said solid alloy. . The process as described in Claim 30, further characterized in that said solid alloy comprises I from approximately 50 ppm to approximately 5% for I weight of elemental silicone. ! 43. A method to increase uniformity of resistance to ! 1 tension in the tantalum metal comprising the introduction of ! * 1 silicone to said tantalum in an amount to increase dich to I I uniformity of resistance to tension. 44. A method for reducing the brittleness of the tantalum metal comprising the introduction of silicone to said tantalum metal in an amount to reduce said brittleness. 'Four. Five. A method for imparting a controlled level of mechanical stress resistance in a tantalum metal comprising the introduction of silicone to said tantalum metal and annealing at a temperature to impart said controlled mechanical stress resistance.