Process for forming an improved metal alloy stent
First Claim
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1. A method for forming a medical device comprising the steps of:
- a) forming a rod or tube having a surface and an outer cross-sectional area, said rod or tube is formed of a metal alloy that is at least about 99 weight percent of a solid solution of molybdenum and rhenium;
b) drawing down said outer cross-sectional area of said rod or tube to a first drawn down cross-sectional area by a reducing mechanism, said rod or tube being drawn down at least once to obtain said first drawn down cross-sectional area, said outer cross-sectional area being reduced by no more than about 25% during each drawing down process;
c) annealing said rod or tube prior to said rod or tube having said outer cross-sectional area drawn down by more than about 50% at a first annealing temperature in a low oxygen environment after said rod or tube has been drawn down to said first drawn down cross-sectional area;
d) drawing down said cross-sectional area of said rod or tube to a second drawn down cross-sectional area by the reducing mechanism after said rod or tube has been annealed, said second drawn down cross-sectional area smaller than said first drawn down cross-sectional area, said rod or tube being drawn down at least once to obtain said second drawn down cross-sectional area, said outer cross-sectional area reduced by no more than about 25% during each drawing down process;
e) annealing said rod or tube that is at said second drawn down cross-sectional area at least one additional time at a second annealing temperature prior to said rod or tube having said outer cross-sectional area drawn down by more than about 50%, said second anneal temperature lower temperature than said first annealing; and
,f) controlling an atmosphere about said rod or tube during said steps of drawing and annealing so that said metal alloy of said rod or tube after final drawing and annealing steps includes less than about 20 ppm nitrogen, less than about 150 ppm carbon, and less than about 50 ppm oxygen and a carbon to oxygen atomic ratio of at least about 2;
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Abstract
A method and process for at least partially forming a medical device that is at least partially formed of a novel metal alloy which improves the physical properties of the medical device.
79 Citations
36 Claims
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1. A method for forming a medical device comprising the steps of:
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a) forming a rod or tube having a surface and an outer cross-sectional area, said rod or tube is formed of a metal alloy that is at least about 99 weight percent of a solid solution of molybdenum and rhenium; b) drawing down said outer cross-sectional area of said rod or tube to a first drawn down cross-sectional area by a reducing mechanism, said rod or tube being drawn down at least once to obtain said first drawn down cross-sectional area, said outer cross-sectional area being reduced by no more than about 25% during each drawing down process; c) annealing said rod or tube prior to said rod or tube having said outer cross-sectional area drawn down by more than about 50% at a first annealing temperature in a low oxygen environment after said rod or tube has been drawn down to said first drawn down cross-sectional area; d) drawing down said cross-sectional area of said rod or tube to a second drawn down cross-sectional area by the reducing mechanism after said rod or tube has been annealed, said second drawn down cross-sectional area smaller than said first drawn down cross-sectional area, said rod or tube being drawn down at least once to obtain said second drawn down cross-sectional area, said outer cross-sectional area reduced by no more than about 25% during each drawing down process; e) annealing said rod or tube that is at said second drawn down cross-sectional area at least one additional time at a second annealing temperature prior to said rod or tube having said outer cross-sectional area drawn down by more than about 50%, said second anneal temperature lower temperature than said first annealing; and
,f) controlling an atmosphere about said rod or tube during said steps of drawing and annealing so that said metal alloy of said rod or tube after final drawing and annealing steps includes less than about 20 ppm nitrogen, less than about 150 ppm carbon, and less than about 50 ppm oxygen and a carbon to oxygen atomic ratio of at least about 2;
1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. A method for forming a stent comprising the steps of:
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a) forming a tube having a surface and an outer cross-sectional area, said tube is formed of a metal alloy that is at least about 99 weight percent of a solid solution of molybdenum and rhenium, said metal alloy including about 46-49 weight percent rhenium and about 51-54 weight percent molybdenum; b) drawing down said outer cross-sectional area of said tube to a first drawn down cross-sectional area by a reducing mechanism, said tube being drawn down at least once to obtain said first drawn down cross-sectional area, said outer cross-sectional area being reduced by no more than about 25% during each drawing down process, said tube heated to about 400-800°
C. at least partially during said drawing down of said tube, said step of drawing down including the inserting of a close-fitting rod in a passageway of said tube prior to drawing down said tube, said close-fitting rod formed of tantalum and niobium, said tube having a grain size after said drawing down of up to 5 ASTM;c) annealing said tube prior to said rod or tube having said outer cross-sectional area drawn down by more than about 50% at a first annealing temperature in a low oxygen environment after said tube has been drawn down to said first drawn down cross-sectional area, said step of annealing said tube includes the steps of a) annealing said tube at an annealing temperature ofat least about 1480°
C. for a time period of at least about 5 minutes for a time period of at least about 5 minutes when said tube has wall thickness of greater than about 0.015 inch, b) annealing said tube at an annealing temperature of about 1450-1480°
C. for a time period of at least about 5 minutes when said tube has wall thickness of about 0.008-0.015 inch, and c) annealing said tube at an annealing temperature of less than about 1450°
C. for a time period of at least about 5 minutes when said tube has wall thickness of less than about 0.008 inch;d) drawing down said cross-sectional area of said tube to a second drawn down cross-sectional area by the reducing mechanism after said tube has been annealed, said tube heated to about 400-800°
C. at least partially during said drawing down of said tube, said step of drawing down including the insertion a close-fitting rod in said passageway of said tube prior to said second drawing down of said tube, said close-fitting rod formed of tantalum and niobium, said second drawn down cross-sectional area smaller than said first drawn down cross-sectional area, said tube having a grain size after said drawing down of up to 5 ASTM, said tube being drawn down at least once to obtain said second drawn down cross-sectional area, said outer cross-sectional area reduced by no more than about 25% during each drawing down process;e) annealing said tube that is at said second drawn down cross-sectional area at least one additional time at a second annealing temperature, said annealing occurring prior to said tube having said outer cross-sectional area drawn down by more than about 50%, said second anneal temperature lower temperature than said first annealing temperature, said step of annealing said tube includes the steps of a) annealing said tube at an annealing temperature of at least about 1480°
C. for a time period of at least about 5 minutes for a time period of at least about 5 minutes when said tube has wall thickness of greater than about 0.015 inch, b) annealing said tube at an annealing temperature of about 1450-1480°
C. for a time period of at least about 5 minutes when said tube has wall thickness of about 0.008-0.015 inch, and c) annealing said tube at an annealing temperature of less than about 1450°
C. for a time period of at least about 5 minutes when said tube has wall thickness of less than about 0.008 inch;f) repeating steps d and e until said tube is at a desired thickness and a grain size of 5-14 ASTM, an atmosphere about said rod or tube is controlled during said steps of drawing and annealing so that said metal alloy of said rod or tube after final drawing and annealing steps includes less than about 20 ppm nitrogen. less than about 150 ppm carbon, and less than about 50 ppm oxygen and a carbon to oxygen atomic ratio of at least about 2;
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,g) cutting said tube to at least partially for said stent. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36)
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Specification