Metal fusion bonding – Process – Preplacing solid filler
Reexamination Certificate
2002-11-25
2003-07-29
Zimmerman, John J. (Department: 1775)
Metal fusion bonding
Process
Preplacing solid filler
C228S181000, C228S225000, C228S246000, C228S250000, C428S555000, C428S593000, C428S594000
Reexamination Certificate
active
06598782
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a metal foil connection of a first and a second metal foil. The first and second metal foils each have a thickness of less than 0.05 mm, and are brazed to one another at a connecting point. The connecting point forms a wedge which is filled with brazing medium. The invention furthermore relates to a honeycomb body of sheet metal layers. The sheet metal layers are formed from metal foils which are at least partly structured and have a thickness of less than 0.05 mm. The sheet metal layers are at least partly brazed to one another. They have one or two respective wedges filled with brazing medium at the brazed connecting points. The invention also relates to a metal foil-brazing medium particle fraction for manufacturing a brazed connection, and a method for manufacturing a metal foil connection of the first and second metal foils through the use of a metal foil-brazing medium particle fraction.
Brazing methods and brazed connections, for example for a metallic honeycomb body, are state of the art for sheet metal layers. German Patent DE 42 19 145 C1, corresponding to U.S. Pat. No. 5,431,330, disclose immersing a honeycomb body in a fluidized bed of brazing powder. The pre-prepared honeycomb body forms brazing medium particles at desired points from a brazing medium particle fraction. The size of the brazing medium particles should be between 1 and 200 micrometers, preferably between 38 and 125 micrometers. Particle sizes in the lower half of that range are more frequently desired than in the upper half. Other methods for applying brazing medium are also disclosed in that document. The methods for applying brazing medium belonging to the prior art are used successfully in brazing honeycomb bodies having sheet metal layers which are made of metal sheets with a material thickness of at least 50 micrometers and more.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a metal foil connection, a honeycomb body, a metal foil brazing medium particle fraction for metal foils and a method for manufacturing a metal foil connection, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and which provide a durable metal foil connection for thin metal foils with a thickness of less than 50 micrometers, in particular less than 40 micrometers.
With the foregoing and other objects in view there is provided, in accordance with the invention, a metal foil connection, comprising a first and a second metal foil having a thickness of less than 0.04 mm. The first and the second metal foils are brazed to one another at a connecting point forming a wedge. Brazing medium substantially fills the wedge and has a mass ML. The first and the second metal foils have sections contacted by the brazing medium in the wedge. The sections having a mass MF. The mass ML of the brazing medium and the mass MF of the sections of the metal foils contacted by the brazing medium in the wedge are in a given ratio MF/ML of between substantially 4 and substantially 8.
With the objects of the invention in view, there is also provided a metal foil connection, comprising a first and a second metal foil having a thickness DF of less than 0.04 mm. The first and the second metal foils are brazed to one another at a connecting point forming one or two wedges. Brazing medium fills each wedge and has a mass ML in the wedge. The mass ML of the brazing medium in the wedge and the thickness DF of the metal foils are in a ratio ML/DF of substantially between 8 g/m and 16 g/m.
When attempting to braze thinner metal foils with a material thickness of less than 50 micrometers, in particular when manufacturing a honeycomb body, it was determined that cells simply melt away when the honeycomb body is brought to the brazing temperature. It was also determined that the cells of the honeycomb body were deformed. It is only when an amount of brazing medium applied per connecting point was used in accordance with the rule for adjustment described herein-above with respect to sheet metal thicknesses used heretofore, that the amount of brazing medium defined thereby, and introduced into the wedge, could result on one hand in the metal foil not becoming detached and formation of gaps at the edges being prevented, while on the other hand a durable connection of the brazing points was created.
If a metal foil which is used for a metal foil connection has a metal foil thickness DF of between 0.05 mm and 0.03 mm, the mass of brazing medium ML to be used for the metal foil connection is selected, in an unexpected manner, in an approximately linear dependency with respect to the metal foil thickness DF. The thinner the metal foil thickness DF, the less the mass of the brazing medium ML to be used. An upper limit as well as a lower limit for the mass of brazing medium ML which can still be used can consequently be determined for some metal foil thicknesses DF, and interpolated or extrapolated for other metal foil thicknesses. If a relationship is established between the mass of the brazing medium ML and the metal foil thickness DF, an upper limit in the extent of the ratio of ML/DF=14.6 g/m, with a variation of +5% and −5% has proved advantageous. A ratio of ML/DF=8.7 g/m, with a variation of +5% and −5%, has proved advantageous as a lower limit for the still useable ratio of the mass of brazing medium ML to the metal foil thickness DF. The range to be used for a metal foil thickness DF of less than 0.05 mm to approximately 0.03 mm, can be very accurately determined from these two relationships, given as the upper limit and lower limit. The best results with respect to the durability of the metal foil connection have been produced when a ratio of the mass of the brazing medium ML in the wedge compared to the metal foil thickness DF is approximately ML/DF=11 g/m, with a variation of +15% and −10%.
When using metal foil thicknesses DF of approximately 0.03 mm or less for the metal foil connection, the linear relationship described hereinabove can also be used in order to obtain satisfactory results. However, in an unexpected manner, it has been shown that with metal foil thicknesses DF of less than 0.03 mm, it is not only a linear relationship which exists between the amount of brazing medium that can be used and the metal foil thickness DF. Instead, the gradient of this linearity changes with respect to a range of the metal foil thickness DF of less than 0.05 mm to approximately 0.03 mm. It flattens out somewhat. Preferably, with metal foil thicknesses DF of approximately, or less than, 0.03 mm, an upper limit of the mass of brazing medium ML is selected in dependence upon the metal foil thickness DF along a curve which passes through the following points with coordinates (ML/DF; DF): (14.6 g/m; 0.03 mm), (14.8 g/m; 0.025 mm), (16 g/m; 0.02 mm), (27 g/m; 0.01 mm). A lower limit with a metal foil thickness DF of approximately, or less than, 0.03 mm for the mass of brazing medium ML to be used, in dependence on the metal foil thickness DF, is advantageously selected from a curve which passes along the following points with coordinates (ML/DF; DF): (8.6 g/m; 0.03 mm), (9 g/m; 0.025 mm), (9.2 g/m; 0.02 mm), 16 g/m; 0.01 mm). Extremely durable metal foil connections with a metal foil thickness DF of approximately, or less than, 0.03 mm have been produced when the mass of brazing medium ML in dependence on the metal foil thickness DF is selected from a curve which passes through the following points with coordinates (ML/DF; DF): (11 g/m; 0.03 mm), (11.2 g/m; 0.025 mm), (12 g/m; 0.02 mm), (20 g/m; 0.01 mm). A variation of +5% and −5% is also applicable for these curves.
A preferred area of application for the metal foil connections described hereinabove is honeycomb bodies of sheet metal layers.
With the objects of the invention in view, there is additionally provided a honeycomb body, comprising sheet metal layers formed
Kurth Ferdi
Schlotmann Helge
Wieres Ludwig
Emitec Gesellschaft fuer Emissions-technologie mbH
Greenberg Laurence A.
Locher Ralph E.
Savage Jason L
Stemer Werner H.
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