박임원
2005-08-03 14:36:39
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탄탈륨 박판이라 SUS 플렌지랑 용접하려 하는데 일반적인 알곤용접으로는
LEAK가 생기는 문제가 있는듯 합니다.
아무래도 탄탈륨은 녹는점이 3000도 이상이고 SUS는 1400도 근처라서 용접시에 SUS만 녹고 탄탈륨은 녹지 않아서 이런문제가 생기는듯 하는데.
이런 용접은 어떻게 하는지요.
그리고 이런용접 가능한 업체라도 아시는분 있으시면 소개해주시면 감사하겠습니다.
LEAK가 생기는 문제가 있는듯 합니다.
아무래도 탄탈륨은 녹는점이 3000도 이상이고 SUS는 1400도 근처라서 용접시에 SUS만 녹고 탄탈륨은 녹지 않아서 이런문제가 생기는듯 하는데.
이런 용접은 어떻게 하는지요.
그리고 이런용접 가능한 업체라도 아시는분 있으시면 소개해주시면 감사하겠습니다.
용접을 반드시 아크용접과 같은 용융용접으로 해야하나요?
용접부에 대한 요구강도는 어느 정도이지요?
박판이라면 적용가능한 다른 용접도 여러가지가 있을 듯한데, 용접해야할 제품의 형상과 요구강도에 따라서 적용가능한 용접법들의 후보가 정해지겠네요.
물론 그 후보중에서 일부 우선 순위를 결정하여 차례로 실제로 용접하면서 검토해가는 순서가 필요할듯합니다.
그 우선 순위 결정에서 고려되는 것 :
1) 제품 형상과 기능
2) 외부 하중(사용수명)과 요구 강도
3) 제품의 용접수량과 주어지는 공간
4) 가격
5) 기타 등등
솔직히 저도 잘 모르겠다는 이야기입니다.
그렇지만 전자부품에 대하여 다양한 용접법을 적용해서 용접공정 개발을 수십번이상 해보았기 때문에 그 접근방법은 대략...
그럼.
부경대학교 신소재공학부 소재프로세스공학전공
교수 조 상 명
용접부에 대한 요구강도는 어느 정도이지요?
박판이라면 적용가능한 다른 용접도 여러가지가 있을 듯한데, 용접해야할 제품의 형상과 요구강도에 따라서 적용가능한 용접법들의 후보가 정해지겠네요.
물론 그 후보중에서 일부 우선 순위를 결정하여 차례로 실제로 용접하면서 검토해가는 순서가 필요할듯합니다.
그 우선 순위 결정에서 고려되는 것 :
1) 제품 형상과 기능
2) 외부 하중(사용수명)과 요구 강도
3) 제품의 용접수량과 주어지는 공간
4) 가격
5) 기타 등등
솔직히 저도 잘 모르겠다는 이야기입니다.
그렇지만 전자부품에 대하여 다양한 용접법을 적용해서 용접공정 개발을 수십번이상 해보았기 때문에 그 접근방법은 대략...
그럼.
부경대학교 신소재공학부 소재프로세스공학전공
교수 조 상 명
답변주신 두분께 감사드립니다.
적용사항은 다이어 프레임 압력계인데 요철이져 있는 원형 탄탈막을 플랜지에 밑면에 용접시켜야 합니다.
외부 압력에 따라 탄탈막이 이동하면서 플랜지내의 압력이 변하게 되죠.
현재는 테스트중에 있는데 일반 알곤 용접시 탄탈막과 플랜지 사이에 헬륨리크테스트를 해보면 지시값이 뜹니다.(리크되고 있다는 이야기)
폭압용접등의 용접은 제가 생소해서...인터넷에 뒤져보니 한국에서는 하는곳이 없는듯 해서 지금현재 좀 난해하네요.
지금현재 레이져 용접등을 적용해 보려하는데.. 이런 용융용접은 아예 안되는건지요
적용사항은 다이어 프레임 압력계인데 요철이져 있는 원형 탄탈막을 플랜지에 밑면에 용접시켜야 합니다.
외부 압력에 따라 탄탈막이 이동하면서 플랜지내의 압력이 변하게 되죠.
현재는 테스트중에 있는데 일반 알곤 용접시 탄탈막과 플랜지 사이에 헬륨리크테스트를 해보면 지시값이 뜹니다.(리크되고 있다는 이야기)
폭압용접등의 용접은 제가 생소해서...인터넷에 뒤져보니 한국에서는 하는곳이 없는듯 해서 지금현재 좀 난해하네요.
지금현재 레이져 용접등을 적용해 보려하는데.. 이런 용융용접은 아예 안되는건지요
Welding of Tantalum (one of the refractory metals)
1. Welding general
The weldability of tantalum is limited only by the ingenuity of the welder in reducing the time and temperature at which the metal may be exposed to moisture, carbon, oxygen, hydrogen, and nitrogen. Hydrogen embrittlement is the single most important cause of failure of tantalum. Even though it does not react with molecular hydrogen below 650°F (343°C), tantalum as equipment component can absorb atomic hydrogen under persistently aggressive condition, causing embrittlement and failure on the operation.
Because of tantalum’s affinity for GETTERING, any fusion weld must be performed in an atmosphere free of contamination. This means not only the weld puddle, but also all hot metal must be protected.
2. Welding time
The weld duration should be kept as short as possible, i.e., in the range of one to ten cycles at 60 cycles per second. This is to prevent excessive external heating. Where possible, the work should be flooded with water for cooling and reduction of oxidation.
Strong, ductile welds can be made by the tungsten inert gas (TIG) method. Extreme care must be taken to cover all surfaces that are raised above 600°F (316°C) by the welding heat with an inert gas.
Helium, argon or a mixture of the two gases creates an atmosphere that prevents embrittlement by absorption of oxygen, nitrogen or hydrogen into the heated metal. Where a pure, inert atmosphere is provided, the fusion and adjacent area will be ductile. Extreme high ductility can be obtained in a welding chamber that can be evacuated and purged with inert gas.
3. Gas-backed fixturing (or Dry box or Vacuum purge chamber)
When the use of a welding chamber is not practical, the heated surfaces can be protected by proper gas-backed fixturing.
This usually serves two purposes:
(a) to hold the work in alignment
(b) to chill the work in order to limit the heat area
Weld ductilities in the order of a 180° bend over one metal thickness can be consistently accomplished when backup gas fixtures and gas-filled trailing cups are used.
4. Dissimilar welding
Tantalum may be welded to several other metals (i.e., Mo, Nb, Cu, etc.). This can be accomplished by resistance welding(2), tungsten-inert gas, plasma laser welding(1), explosion welding(1), brazing(1), and electron beam welding(2). However Extreme care must be required due to the following reasons;
(a) Formation of brittle intermetallic phases is likely with many metals and must be avoided. Surfaces to be heated above 600°F (316°C) should be protected by an inert gas such as argon or helium to prevent embrittlement.
(b) The different melting temperature between Refractory Metals (i.e., m.p. of Ta = 5430°F, 3000°C) and alloy steels (i.e., m.p. of 316 SS: 2552°F, 1400°C) also makes a difficult welding condition.
(1) : recommended for Ta to 316 SS. But the WPS & PQR with joint integrity/strength shall be approved by the certified agency.
; Recommended filler metals for brazing : BAg, BCu, or BNi
(2) : Resistance welding
The resistance welding of most refractory metals and their alloys is not normally done for several reasons :
(a) The resulting cast, coarse grained microstructure has essentially no ductility or toughness.
(b) The coefficients of thermal expansion are much lower than most common metals, that results in cracking upon cooling if dissimilar metals are joined.
(3) The refractory metals are also chemically reactive and will oxidize unless heated in inert gas or vacuum. e.g., Ta oxidizes readily at above 650°F (343°C) – 600°F (316°C) in a margin and the intermetallic compounds lead to weld embrittlement.
Some Electron Beam Welding is performed to join these metals for low stress applications.
5. Similar welding
Tantalum may also be welded to itself by inert gas arc welding (most common practice). Acetylene torch welding is destructive to tantalum.
6. Cleaning and Workmanship before/during welding
Absolute cleanliness is essential for good tantalum welding using any of the above techniques. A generally accepted procedure is to abrade slightly the surfaces to be joined with emery cloth to remove the naturally occurring oxide film. Then etch with a nitric-hydrofluoric acid solution. Finally, rinse before welding with a solvent such as acetone to be sure all grease is removed. Only handle the work with clean, lint-free nylon gloves.
7. General Cleaning/ Degreasing and Grit Blasting for base metal or welded metal
(1) Cleaning/ Degreasing
Tantalum parts must not be cleaned by hydrogen firing. Cleaning and degreasing present no special problems and conventional methods and materials may be used. However, note that hot caustics must be avoided. Electronic tube parts that must be chemically cleaned require more careful treatment.
The first step for tantalum parts that have been blasted with steel grit is to immerse the parts in hot hydrochloric acid to remove particles of iron. The hydrochloric acid may be used as hot and as strong a solution as desired; it will not attack the tantalum. The parts should then be thoroughly rinsed with distilled water. Tap water often contains calcium salts that may be converted to insoluble sulfates in the subsequent cleaning process. If the tantalum parts have not been grit-blasted, the hydrochloric acid cleaning may begin with the second step below.
The second step is a chemical cleaning process. A hot chromic acid cleaning solution, commonly used for cleaning glass, may be applied. A saturated solution of potassium dichromate in hot concentrated sulfuric acid may be used for this purpose. However, chromium trioxide is preferred to potassium dichromate because its use eliminates the possibility of potassium residues in crevices or elsewhere on the tantalum parts. The cleaning solution should be applied at approximately 110`C and should maintain its red color at all times. When the liquid becomes muddy or turns green, it should be discarded.
After the chromic acid wash, a third step is applied to rinse the parts. The preferred rinse is hot distilled water. If running distilled water is not available, three lip washes will suffice, but it is important that all cleaning solution be removed. The parts should be dried in clean, warm air, free from dust. The parts should not be wiped with paper or cloth and they should not be handled with fingers.
(2) Grit Blasting
Tantalum parts for electronic tubes are often blasted with steel grit to provide a greater radiation surface. The recommended procedure is a blast of a few seconds with No. 90 steel grit, at a pressure of 20 to 40 pounds. Sand, alumina, silicon carbide or other abrasives should not be used because they become embedded in the tantalum and cannot be removed with any chemical treatment that would not also damage the tantalum. This is followed by a thorough cleaning in hot hydrochloric acid as previously described.
The purpose of grit blasting is to increase the amount of surface per unit of area. Therefore, the blasting should be performed in a manner that will produce fine "whiskers" rather than mere indentations on the surface. Sharp particles of grit will do this, while dull ones merely indent the surface. To achieve best results, the blasting nozzle should be held at an angle nearly tangential to the work, rather than perpendicular to the work.
Please consult PLANSEE or NRC Inc. for more detail.
1. Welding general
The weldability of tantalum is limited only by the ingenuity of the welder in reducing the time and temperature at which the metal may be exposed to moisture, carbon, oxygen, hydrogen, and nitrogen. Hydrogen embrittlement is the single most important cause of failure of tantalum. Even though it does not react with molecular hydrogen below 650°F (343°C), tantalum as equipment component can absorb atomic hydrogen under persistently aggressive condition, causing embrittlement and failure on the operation.
Because of tantalum’s affinity for GETTERING, any fusion weld must be performed in an atmosphere free of contamination. This means not only the weld puddle, but also all hot metal must be protected.
2. Welding time
The weld duration should be kept as short as possible, i.e., in the range of one to ten cycles at 60 cycles per second. This is to prevent excessive external heating. Where possible, the work should be flooded with water for cooling and reduction of oxidation.
Strong, ductile welds can be made by the tungsten inert gas (TIG) method. Extreme care must be taken to cover all surfaces that are raised above 600°F (316°C) by the welding heat with an inert gas.
Helium, argon or a mixture of the two gases creates an atmosphere that prevents embrittlement by absorption of oxygen, nitrogen or hydrogen into the heated metal. Where a pure, inert atmosphere is provided, the fusion and adjacent area will be ductile. Extreme high ductility can be obtained in a welding chamber that can be evacuated and purged with inert gas.
3. Gas-backed fixturing (or Dry box or Vacuum purge chamber)
When the use of a welding chamber is not practical, the heated surfaces can be protected by proper gas-backed fixturing.
This usually serves two purposes:
(a) to hold the work in alignment
(b) to chill the work in order to limit the heat area
Weld ductilities in the order of a 180° bend over one metal thickness can be consistently accomplished when backup gas fixtures and gas-filled trailing cups are used.
4. Dissimilar welding
Tantalum may be welded to several other metals (i.e., Mo, Nb, Cu, etc.). This can be accomplished by resistance welding(2), tungsten-inert gas, plasma laser welding(1), explosion welding(1), brazing(1), and electron beam welding(2). However Extreme care must be required due to the following reasons;
(a) Formation of brittle intermetallic phases is likely with many metals and must be avoided. Surfaces to be heated above 600°F (316°C) should be protected by an inert gas such as argon or helium to prevent embrittlement.
(b) The different melting temperature between Refractory Metals (i.e., m.p. of Ta = 5430°F, 3000°C) and alloy steels (i.e., m.p. of 316 SS: 2552°F, 1400°C) also makes a difficult welding condition.
(1) : recommended for Ta to 316 SS. But the WPS & PQR with joint integrity/strength shall be approved by the certified agency.
; Recommended filler metals for brazing : BAg, BCu, or BNi
(2) : Resistance welding
The resistance welding of most refractory metals and their alloys is not normally done for several reasons :
(a) The resulting cast, coarse grained microstructure has essentially no ductility or toughness.
(b) The coefficients of thermal expansion are much lower than most common metals, that results in cracking upon cooling if dissimilar metals are joined.
(3) The refractory metals are also chemically reactive and will oxidize unless heated in inert gas or vacuum. e.g., Ta oxidizes readily at above 650°F (343°C) – 600°F (316°C) in a margin and the intermetallic compounds lead to weld embrittlement.
Some Electron Beam Welding is performed to join these metals for low stress applications.
5. Similar welding
Tantalum may also be welded to itself by inert gas arc welding (most common practice). Acetylene torch welding is destructive to tantalum.
6. Cleaning and Workmanship before/during welding
Absolute cleanliness is essential for good tantalum welding using any of the above techniques. A generally accepted procedure is to abrade slightly the surfaces to be joined with emery cloth to remove the naturally occurring oxide film. Then etch with a nitric-hydrofluoric acid solution. Finally, rinse before welding with a solvent such as acetone to be sure all grease is removed. Only handle the work with clean, lint-free nylon gloves.
7. General Cleaning/ Degreasing and Grit Blasting for base metal or welded metal
(1) Cleaning/ Degreasing
Tantalum parts must not be cleaned by hydrogen firing. Cleaning and degreasing present no special problems and conventional methods and materials may be used. However, note that hot caustics must be avoided. Electronic tube parts that must be chemically cleaned require more careful treatment.
The first step for tantalum parts that have been blasted with steel grit is to immerse the parts in hot hydrochloric acid to remove particles of iron. The hydrochloric acid may be used as hot and as strong a solution as desired; it will not attack the tantalum. The parts should then be thoroughly rinsed with distilled water. Tap water often contains calcium salts that may be converted to insoluble sulfates in the subsequent cleaning process. If the tantalum parts have not been grit-blasted, the hydrochloric acid cleaning may begin with the second step below.
The second step is a chemical cleaning process. A hot chromic acid cleaning solution, commonly used for cleaning glass, may be applied. A saturated solution of potassium dichromate in hot concentrated sulfuric acid may be used for this purpose. However, chromium trioxide is preferred to potassium dichromate because its use eliminates the possibility of potassium residues in crevices or elsewhere on the tantalum parts. The cleaning solution should be applied at approximately 110`C and should maintain its red color at all times. When the liquid becomes muddy or turns green, it should be discarded.
After the chromic acid wash, a third step is applied to rinse the parts. The preferred rinse is hot distilled water. If running distilled water is not available, three lip washes will suffice, but it is important that all cleaning solution be removed. The parts should be dried in clean, warm air, free from dust. The parts should not be wiped with paper or cloth and they should not be handled with fingers.
(2) Grit Blasting
Tantalum parts for electronic tubes are often blasted with steel grit to provide a greater radiation surface. The recommended procedure is a blast of a few seconds with No. 90 steel grit, at a pressure of 20 to 40 pounds. Sand, alumina, silicon carbide or other abrasives should not be used because they become embedded in the tantalum and cannot be removed with any chemical treatment that would not also damage the tantalum. This is followed by a thorough cleaning in hot hydrochloric acid as previously described.
The purpose of grit blasting is to increase the amount of surface per unit of area. Therefore, the blasting should be performed in a manner that will produce fine "whiskers" rather than mere indentations on the surface. Sharp particles of grit will do this, while dull ones merely indent the surface. To achieve best results, the blasting nozzle should be held at an angle nearly tangential to the work, rather than perpendicular to the work.
Please consult PLANSEE or NRC Inc. for more detail.
공지사항
Zr, Ti, Ta의 세 금속은 자기들끼리는 용접이 가능하지만, 다른 금속과는 용융접합이 불가능합니다.
지금의 경우에 추천할 수 있는 방법은 확산 접합이나, 두께가 좀 여유가 있다면 폭발접합을 추천할 수 있습니다.
너무 박판이라면 폭발접합은 곤란하겠지요