EP0049033B1 - Brazeable ferritic stainless steel, method of using same and article formed therefrom - Google Patents
Brazeable ferritic stainless steel, method of using same and article formed therefrom Download PDFInfo
- Publication number
- EP0049033B1 EP0049033B1 EP81303337A EP81303337A EP0049033B1 EP 0049033 B1 EP0049033 B1 EP 0049033B1 EP 81303337 A EP81303337 A EP 81303337A EP 81303337 A EP81303337 A EP 81303337A EP 0049033 B1 EP0049033 B1 EP 0049033B1
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- EP
- European Patent Office
- Prior art keywords
- brazeable
- ferritic stainless
- stainless steel
- titanium
- brazing
- 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.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
Definitions
- the present invention relates to brazeable ferritic stainless steels and is particularly useful for ferritic stainless steel articles which are joined by brazing.
- Ferritic stainless steels possess excellent mechanical properties and oxidation and general corrosion resistance at elevated temperatures. These steels are ideal for use as the structural members of heat exchangers, exhaust systems, chemical process vessels and the like which are exposed to high temperatures and stresses and corrosive environments. Fabrication of these articles frequently requires the joining of the ferritic stainless steel with either itself or with another dissimilar metal at sufficiently high temperatures for the joining method to be effective. Also, generally speaking, the steel must be joined in a temperature range exceeding the anticipated service temperature.
- Brazing is a widely practised method of joining metals involving temperatures of from 427°C (800°F) to the 1093°C-1149°C (2000°F-2100°F) range which are above the melting point of the brazing filler material but below the melting point of the base metal being joined.
- temperatures of from 427°C (800°F) to the 1093°C-1149°C (2000°F-2100°F) range which are above the melting point of the brazing filler material but below the melting point of the base metal being joined.
- the temperature of the brazing filler material is about the melting point, it becomes molten and wets the surface of the steel, and then flows by capillary action to fill a joint. Bonding results from the intimate contact produced by the dissolution of a small amount of the base metal in the molten filler metal.
- Ferritic stainless steels to be joined at high temperatures contain low levels of carbon and small amounts of stabilizing elements for combining with carbon and nitrogen to maintain the ferritic phase and to maintain the oxidation and corrosion resistance of the steel.
- Stabilizing elements such as titanium, niobium or tantalum react with the carbon and nitrogen to prevent the formation and precipitation of chromium carbides and nitrides at grain boundaries and the simultaneous depletion of chromium in the surrounding areas. Stabilizing elements must be added in amounts exceeding the theoretical requirement to assure complete stabilization of carbon and nitrogen. Titanium has been the preferred stabilizing element because of its very strong affinity for carbon and nitrogen, its low atomic weight and its availability. Other stabilizing agents including niobium and tantalum have not been favoured because they are more expensive and less effective on a weight basis than titanium and also because they are accompanied by a tendency toward weld cracking problems.
- Titanium stabilized ferritic steels known in the prior art cannot be readily brazed with filler materials such as oxygen-free copper and nickel base alloys. These steels form a non-wettable surface film which prevents proper bonding between the ferritic stainless steel base metal and the brazing filler material even when furance brazing under vacuum or in an inert atmosphere.
- the oxygen-free copper as a high temperature brazing filler metal does not penetrate this surface film.
- Nickel alloy high temperature brazing filler metals usually contain boron and silicon additions to penetrate the surface film. Although the steel wettability is improved, these nickel base materials will also penetrate the grain boundaries thereby causing intergranular attack of the base metal.
- brazing operations are not aided by increased temperatures or by increased brazing times because the high temperature range is beginning to affect the grain size of the steel and prolonged time tends to increase film resistance.
- brazing with copper is impossible and brazing with nickel base metals is not consistent enough to be of practical value from a quality assurance viewpoint.
- copper clad ferritic stainless steels are used in brazing applications when the brazing temperature is to reach 1093°C-1149°C (2000°F-2100°F). In this process, the copper cladding is brazed rather than the steel.
- the present invention relates to a stabilized ferritic stainless steel composition which is wettable by conventional brazing materials used at temperatures of from 1093°C-1149°C (2000°F-2100°F) in furnace brazing practices.
- the present invention provides a ferritic stainless steel containing, by weight, 10.5% to 13.5% chromium, up to 0.03% carbon, up to 0.05% nitrogen, up to 0.10% aluminium, up to 0.12% titanium and at least one other stabilizing element selected from niobium and tantalum in accordance with the relationship: the balance being iron optionally including up to 1.25% molybdenum, up to 1 % manganese and up to 1 % silicon and incidental impurities.
- Preferred nitrogen and aluminium levels are up to 0.03% and up to 0.020% respectively.
- niobium, tantalum and titanium in accordance with this stabilization relationship are sufficient to effectively stabilize the interstitial elements in the steel without forming a non-wettable surface film.
- the niobium and tantalum are present as additions to the melt. Where niobium is a stabilising element, it may preferably be present in an amount up to 1.0%. When tantalum is a stabilizing element, it may preferably be present in an amount up to 1.8%. Titanium may be present in the scrap feed or added to the melt. The titanium is responsible for the nature of the film which becomes non-wettable when titanium is present in amounts greater than about 0.12%.
- titanium compounds stable at brazing temperatures such as Ti0 2 , TiS and TiN are permitted to form.
- oxygen, sulphur and nitrogen have an undesirable effect on other steel qualties and generally they will be kept as low as possible.
- the titanium is preferably present in an amount up to 0.01 % by weight and, most preferably, up to 0.005%.
- the steel may also contain up to 0.1 % aluminium, up to 1.25% molybdenum, up to 1% manganese and up to 1% silicon to enhance its mechanical and corrosion properties. Articles of this composition are wettable by fillers such as copper, nickel and their alloys and can be successfully furnace brazed according to conventional practices.
- titanium is tolerated in controlled amounts, i.e. from at least 0.001 % up to 0.12%, to prevent weld cracking while maintaining reasonable wettability during brazing operations. Larger amounts of titanium render the steel unbrazeable for practical purposes.
- Laboratory heats Nos. 1-6 and 14-16 are alloys in accordance with the present invention; laboratory heats 7-13 and the commercial heats A and B are included for purposes of comparison.
- the test generally consisted of placing a brazing filler material on each specimen and heating the specimens and filler materials to the melting point of the filler material.
- the wettability of the specimens were evaluated according to the parameter "d 2 /h", where "d” is the average diameter of the drop in inches which formed on the surface of the specimen and "h” is the height of the drop in inches, wettability being proportional to the area covered by the drop and inversely proportional to the height of the drop.
- the furnace was evacuated cold, heated to 565°C (1050°F) held at a vacuum of one micron (133.3 Pa) or less while heating to 649°C (1200°F), pressurized with nitrogen to 1500 microns (2.10 5 Pa) and heated to the brazing temperature.
- the furnace was evacuated cold, heated to 565°C (1050°F), held at a vacuum of one micron (133.3 Pa) or less while heating to 649°C (1200°F), pressurized with dry hydrogen (having a dew point of less than -62°C 4-80°F) to a pressure of 300,000 microns (4.10' Pa) and heated to the brazing temperature.
- the wettability ratings (d 2 /h) of the specimens are shown in Table II. The letter "C" indicates that the specimen was completely wetted.
- the wettability of the laboratory melted compositions can be compared with each other and with the prior art compositions of Heats A and B to determine the adverse effects of titanium.
- the prior art compositions are clearly non-wettable.
- the stabilized compositions of Heats 1-4 and 14-16 contain up to 0.005 wt% of titanium and exhibit superior wettability under all atmospheres.
- the effect of increasing amounts of titanium is most clearly shown by the compositions of Heats 5-7.
- the composition of Heat 5 contains 0.008 wt% titanium and has superior wettability characteristics under all atmospheres.
- the composition of Heat 6 contains 0.11 wt% titanium and has improived wettability characteristics under inert gas and vacuum atmospheres, however the adverse effect of titanium is evident in a reducing atmosphere.
- Heats 7-13 contain large amounts of titanium and have no better wettability characteristics than do the prior art compositions.
- Figures 1 and 2 are the perspective and top views, respectively, of a brazing table supporting the specimens identified in Tables I and II.
- Specimens A and B are the commercial steels and illustrate the problem where the filler material does not wet the surface beyond the periphery of the molten drop.
- specimens 7, 8, 9 and 10 are also not wetted by the filler material.
- Specimens 1, 2, 3 and 4 are completely wetted by the oxygen-free copper.
- Specimens 5 and 6 although containing increasing titanium concentrations of 0.008% and 0.11 % respectively, are clearly wetted by the copper beyond the periphery of the molten drop.
- the prior art compositions were not tested but they would have a rating approximating those of Heats 7 and 9 respectively in view of their titanium contents.
- the compositions of Heats 3, 5 and 14-16 all contain less than .01 wt% titanium and have superior wettability characteristics.
- the composition of Heat 6 contains 0.11 wt% titanium and has superior wettability characteristics in comparison to the other compositions containing 0.18 wt% (Heat 12) or more titanium (Heats 7 and 9).
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Ceramic Products (AREA)
- Heat Treatment Of Sheet Steel (AREA)
- Laminated Bodies (AREA)
- Catalysts (AREA)
Description
- The present invention relates to brazeable ferritic stainless steels and is particularly useful for ferritic stainless steel articles which are joined by brazing.
- Ferritic stainless steels possess excellent mechanical properties and oxidation and general corrosion resistance at elevated temperatures. These steels are ideal for use as the structural members of heat exchangers, exhaust systems, chemical process vessels and the like which are exposed to high temperatures and stresses and corrosive environments. Fabrication of these articles frequently requires the joining of the ferritic stainless steel with either itself or with another dissimilar metal at sufficiently high temperatures for the joining method to be effective. Also, generally speaking, the steel must be joined in a temperature range exceeding the anticipated service temperature. Brazing is a widely practised method of joining metals involving temperatures of from 427°C (800°F) to the 1093°C-1149°C (2000°F-2100°F) range which are above the melting point of the brazing filler material but below the melting point of the base metal being joined. When the temperature of the brazing filler material is about the melting point, it becomes molten and wets the surface of the steel, and then flows by capillary action to fill a joint. Bonding results from the intimate contact produced by the dissolution of a small amount of the base metal in the molten filler metal.
- Ferritic stainless steels to be joined at high temperatures contain low levels of carbon and small amounts of stabilizing elements for combining with carbon and nitrogen to maintain the ferritic phase and to maintain the oxidation and corrosion resistance of the steel. Stabilizing elements such as titanium, niobium or tantalum react with the carbon and nitrogen to prevent the formation and precipitation of chromium carbides and nitrides at grain boundaries and the simultaneous depletion of chromium in the surrounding areas. Stabilizing elements must be added in amounts exceeding the theoretical requirement to assure complete stabilization of carbon and nitrogen. Titanium has been the preferred stabilizing element because of its very strong affinity for carbon and nitrogen, its low atomic weight and its availability. Other stabilizing agents including niobium and tantalum have not been favoured because they are more expensive and less effective on a weight basis than titanium and also because they are accompanied by a tendency toward weld cracking problems.
- Titanium stabilized ferritic steels known in the prior art (see e.g., Lula et al. United States Patent No. 3,250,611) cannot be readily brazed with filler materials such as oxygen-free copper and nickel base alloys. These steels form a non-wettable surface film which prevents proper bonding between the ferritic stainless steel base metal and the brazing filler material even when furance brazing under vacuum or in an inert atmosphere. The oxygen-free copper as a high temperature brazing filler metal does not penetrate this surface film. Nickel alloy high temperature brazing filler metals usually contain boron and silicon additions to penetrate the surface film. Although the steel wettability is improved, these nickel base materials will also penetrate the grain boundaries thereby causing intergranular attack of the base metal. In addition, brazing operations are not aided by increased temperatures or by increased brazing times because the high temperature range is beginning to affect the grain size of the steel and prolonged time tends to increase film resistance. For these reasons, brazing with copper is impossible and brazing with nickel base metals is not consistent enough to be of practical value from a quality assurance viewpoint. Thus copper clad ferritic stainless steels are used in brazing applications when the brazing temperature is to reach 1093°C-1149°C (2000°F-2100°F). In this process, the copper cladding is brazed rather than the steel.
- The present invention relates to a stabilized ferritic stainless steel composition which is wettable by conventional brazing materials used at temperatures of from 1093°C-1149°C (2000°F-2100°F) in furnace brazing practices.
- The present invention provides a ferritic stainless steel containing, by weight, 10.5% to 13.5% chromium, up to 0.03% carbon, up to 0.05% nitrogen, up to 0.10% aluminium, up to 0.12% titanium and at least one other stabilizing element selected from niobium and tantalum in accordance with the relationship:
- Preferred nitrogen and aluminium levels are up to 0.03% and up to 0.020% respectively.
- The presence of niobium, tantalum and titanium in accordance with this stabilization relationship are sufficient to effectively stabilize the interstitial elements in the steel without forming a non-wettable surface film. The niobium and tantalum are present as additions to the melt. Where niobium is a stabilising element, it may preferably be present in an amount up to 1.0%. When tantalum is a stabilizing element, it may preferably be present in an amount up to 1.8%. Titanium may be present in the scrap feed or added to the melt. The titanium is responsible for the nature of the film which becomes non-wettable when titanium is present in amounts greater than about 0.12%. Greater amounts of titanium could be tolerated and the effect of titanium on wettability could be neutralized if titanium compounds stable at brazing temperatures such as Ti02, TiS and TiN are permitted to form. However, oxygen, sulphur and nitrogen have an undesirable effect on other steel qualties and generally they will be kept as low as possible. From a brazing viewpoint it is preferable to have a composition free from titanium. For this reason the titanium is preferably present in an amount up to 0.01 % by weight and, most preferably, up to 0.005%. The steel may also contain up to 0.1 % aluminium, up to 1.25% molybdenum, up to 1% manganese and up to 1% silicon to enhance its mechanical and corrosion properties. Articles of this composition are wettable by fillers such as copper, nickel and their alloys and can be successfully furnace brazed according to conventional practices.
- In some cases, however, it may be desirable to both weld and braze the same article. Therefore, titanium is tolerated in controlled amounts, i.e. from at least 0.001 % up to 0.12%, to prevent weld cracking while maintaining reasonable wettability during brazing operations. Larger amounts of titanium render the steel unbrazeable for practical purposes.
- To illustrate the beneficial results of the invention specimens from sixteen laboratory heats and two commercial heats were tested for wettability. The composition of the laboratory heats and the commercial heats are identified in Table I as Nos. 1-16 and Nos. A and B respectively. Laboratory heats Nos. 1-6 and 14-16 are alloys in accordance with the present invention; laboratory heats 7-13 and the commercial heats A and B are included for purposes of comparison.
- Samples from the laboratory heats were hot rolled to about 2.54 mm (0.100 inch) and cold rolled to 0.508 mm (0.020 inch). The commercial samples were also cold rolled to 0.508 mm (0.020 inch). The cold rolled samples were then annealed and pickled in accordance with standard practices. Circular specimens of 38 mm (12 inch) diameter were stamped from the cold rolled strips and tested for brazing wettability in a resistance heated cold wall vacuum furnace.
- The test generally consisted of placing a brazing filler material on each specimen and heating the specimens and filler materials to the melting point of the filler material. The wettability of the specimens were evaluated according to the parameter "d2/h", where "d" is the average diameter of the drop in inches which formed on the surface of the specimen and "h" is the height of the drop in inches, wettability being proportional to the area covered by the drop and inversely proportional to the height of the drop.
- Specimens of the heats were tested at 1121°C (2050°F) in conventional furnace atmospheres with oxygen-free copper as a brazing filler material. No flux was applied because this would be an uncommon practice in furnace brazing operations. Short 3.175 mm (0.125 inch) lengths of 0.254 mm (0.010 inch) diameter wire with square ends were placed on and at the centre of each specimen heated. In vacuum tests, the furnace was evacuated cold, heated to 565°C (1050°F), held at a vacuum of one micron of mercury (133.3 Pa) or less while heating to the brazing temperature. In inert gas tests, the furnace was evacuated cold, heated to 565°C (1050°F) held at a vacuum of one micron (133.3 Pa) or less while heating to 649°C (1200°F), pressurized with nitrogen to 1500 microns (2.105Pa) and heated to the brazing temperature.
- In the reducing atmosphere tests, the furnace was evacuated cold, heated to 565°C (1050°F), held at a vacuum of one micron (133.3 Pa) or less while heating to 649°C (1200°F), pressurized with dry hydrogen (having a dew point of less than -62°C 4-80°F) to a pressure of 300,000 microns (4.10' Pa) and heated to the brazing temperature. The wettability ratings (d2/h) of the specimens are shown in Table II. The letter "C" indicates that the specimen was completely wetted.
- The wettability of the laboratory melted compositions can be compared with each other and with the prior art compositions of Heats A and B to determine the adverse effects of titanium. The prior art compositions are clearly non-wettable. The stabilized compositions of Heats 1-4 and 14-16 contain up to 0.005 wt% of titanium and exhibit superior wettability under all atmospheres. The effect of increasing amounts of titanium is most clearly shown by the compositions of Heats 5-7. The composition of
Heat 5 contains 0.008 wt% titanium and has superior wettability characteristics under all atmospheres. The composition ofHeat 6 contains 0.11 wt% titanium and has improived wettability characteristics under inert gas and vacuum atmospheres, however the adverse effect of titanium is evident in a reducing atmosphere. Heats 7-13 contain large amounts of titanium and have no better wettability characteristics than do the prior art compositions. - The difference in wettability between the specimens brazed with oxygen-free copper in a dry nitrogen atmosphere is seen from Figures 1 and 2. Figures 1 and 2 are the perspective and top views, respectively, of a brazing table supporting the specimens identified in Tables I and II. Specimens A and B are the commercial steels and illustrate the problem where the filler material does not wet the surface beyond the periphery of the molten drop. Similarly,
specimens Specimens Specimens - Specimens of the Heats were tested at 1093°C (2000°F) under vacuum conditions with a nickel alloy as a brazing filler material. In these tests nickel alloy powder (AWS BNi-2) was mixed with a plastic cement which vaporized completely before reaching 538°C (1000°F). The mixture was formed into pellets of approximately 4.7625 mm (0.1875 inch) diameter by 4.7625 mm (0.1875 inch) height and the pellets were placed on the specimens. The furnace was evacuated cold and heated to the brazing temperature. No flux was applied because this is uncommon practice in furnace brazing at high temperatures. The wettability ratings of the laboratory melted specimens are shown in Table III. The letter "C" indicates that the specimen was completely wetted.
- The prior art compositions were not tested but they would have a rating approximating those of
Heats Heats Heat 6 contains 0.11 wt% titanium and has superior wettability characteristics in comparison to the other compositions containing 0.18 wt% (Heat 12) or more titanium (Heats 7 and 9).
Claims (13)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US17632480A | 1980-08-08 | 1980-08-08 | |
US176324 | 1980-08-08 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0049033A1 EP0049033A1 (en) | 1982-04-07 |
EP0049033B1 true EP0049033B1 (en) | 1985-11-21 |
Family
ID=22643909
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81303337A Expired EP0049033B1 (en) | 1980-08-08 | 1981-07-21 | Brazeable ferritic stainless steel, method of using same and article formed therefrom |
Country Status (9)
Country | Link |
---|---|
EP (1) | EP0049033B1 (en) |
JP (1) | JPS5760056A (en) |
AT (1) | ATA345281A (en) |
AU (1) | AU7317081A (en) |
BR (1) | BR8105025A (en) |
CA (1) | CA1181267A (en) |
DE (1) | DE3172977D1 (en) |
ES (1) | ES504584A0 (en) |
ZA (1) | ZA814922B (en) |
Families Citing this family (12)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6029449A (en) * | 1983-07-27 | 1985-02-14 | Mitsubishi Heavy Ind Ltd | High-chromium heat-resisting cast and forged steel |
DE3480602D1 (en) * | 1983-12-12 | 1990-01-04 | Armco Advanced Materials | HEAT-RESISTANT FERRITIC STEEL. |
US4834808A (en) * | 1987-09-08 | 1989-05-30 | Allegheny Ludlum Corporation | Producing a weldable, ferritic stainless steel strip |
CN1049699C (en) * | 1994-04-21 | 2000-02-23 | 川崎制铁株式会社 | Hot rolled ferritic steel used for car exhausting material |
CA2650469C (en) | 2006-05-09 | 2014-02-11 | Nippon Steel & Sumikin Stainless Steel Corporation | Stainless steel excellent in corrosion resistance, ferritic stainless steel excellent in resistance to crevice corrosion and formability, and ferritic stainless steel excellent in resistance to crevice corrosion |
JP5390175B2 (en) * | 2007-12-28 | 2014-01-15 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel with excellent brazeability |
JP5788946B2 (en) * | 2007-12-28 | 2015-10-07 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel for parts assembled by brazing with excellent brazing |
JP5264199B2 (en) * | 2008-01-28 | 2013-08-14 | 日新製鋼株式会社 | EGR cooler using ferritic stainless steel |
JP5420292B2 (en) * | 2008-05-12 | 2014-02-19 | 日新製鋼株式会社 | Ferritic stainless steel |
JP5462583B2 (en) * | 2008-10-24 | 2014-04-02 | 新日鐵住金ステンレス株式会社 | Ferritic stainless steel sheet for EGR cooler |
MX348600B (en) * | 2011-08-18 | 2017-06-21 | Unitload Pty Ltd | Load bearing structure. |
EP2980274B8 (en) | 2013-03-29 | 2020-04-22 | NIPPON STEEL Stainless Steel Corporation | Ferritic stainless steel sheet having excellent brazeability, heat exchanger, ferritic stainless steel sheet for heat exchangers, ferritic stainless steel, ferritic stainless steel for members of fuel supply systems, and member of fuel supply system |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3000729A (en) * | 1959-12-03 | 1961-09-19 | Armco Steel Corp | Stainless steel |
US3389991A (en) * | 1964-12-23 | 1968-06-25 | Armco Steel Corp | Stainless steel and method |
DE1783136C2 (en) * | 1965-10-22 | 1975-10-02 | Stahlwerke Suedwestfalen Ag, 5930 Huettental-Geisweid | Use of an easily machinable, rustproof, magnetically soft chromium steel for solenoid valves |
JPS5432409B2 (en) * | 1973-11-21 | 1979-10-15 | ||
US3997373A (en) * | 1975-01-13 | 1976-12-14 | Allegheny Ludlum Industries, Inc. | Ferritic stainless steel having high anisotropy |
-
1981
- 1981-07-17 ZA ZA814922A patent/ZA814922B/en unknown
- 1981-07-21 EP EP81303337A patent/EP0049033B1/en not_active Expired
- 1981-07-21 DE DE8181303337T patent/DE3172977D1/en not_active Expired
- 1981-07-21 AU AU73170/81A patent/AU7317081A/en not_active Abandoned
- 1981-08-05 AT AT0345281A patent/ATA345281A/en not_active IP Right Cessation
- 1981-08-05 BR BR8105025A patent/BR8105025A/en unknown
- 1981-08-06 ES ES504584A patent/ES504584A0/en active Granted
- 1981-08-07 CA CA000383481A patent/CA1181267A/en not_active Expired
- 1981-08-08 JP JP56124638A patent/JPS5760056A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
ES8302116A1 (en) | 1983-01-01 |
ZA814922B (en) | 1982-07-28 |
EP0049033A1 (en) | 1982-04-07 |
JPH034617B2 (en) | 1991-01-23 |
ES504584A0 (en) | 1983-01-01 |
ATA345281A (en) | 1983-12-15 |
BR8105025A (en) | 1982-04-20 |
DE3172977D1 (en) | 1986-01-02 |
CA1181267A (en) | 1985-01-22 |
AU7317081A (en) | 1982-02-11 |
JPS5760056A (en) | 1982-04-10 |
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