Metal fusion bonding – Process – Diffusion type
Reexamination Certificate
1998-10-01
2001-01-23
Ryan, Patrick (Department: 1725)
Metal fusion bonding
Process
Diffusion type
C228S195000, C228S221000, C228S223000
Reexamination Certificate
active
06176418
ABSTRACT:
TECHNICAL FIELD
This invention relates to composite bonding technology for different kind of materials, which can be used to effectively bond metal beryllium, copper alloy and stainless steel.
BACKGROUND ART
Recently, the industry became interested in developing composite bonding technology for bonding various materials having different properties to each other to form a composite body.
Such bonding materials include metal beryllium, which is used for various purposes, such as transmission windows for X-ray, equipment due to excellent X-ray transmissibility and various applications related to nuclear equipment.
For applying to X-ray windows, it has been conventional practice to bond metal beryllium to a flange or like structural body made of stainless steel by brazing or diffusion bonding. However, stainless steel to which metal beryllium has been directly bonded suffers from a general problem of insufficient thermal conductivity.
Therefore, in order to improve thermal conductivity, a bonding process has been developed in which the copper alloy is bonded to a structural body of stainless steel in advance, and the metal beryllium is then bonded to the bonded body of copper alloy and stainless steel.
However, the above-mentioned bonding process requires that, after the stainless steel and copper alloy have been bonded to each other, an additional step is required to bond the metal beryllium to the bonded body of copper alloy and stainless steel by brazing or diffusion bonding, so that there remain problems that not only the bonding treatment is complicated, but also it is costly to perform.
Also, it has been a general practice that the brazing or diffusion bonding of metal beryllium be performed at a temperature within a range of 650 to 800° C. This temperature range overlaps with the sensitizing temperature of the stainless steel. However, when brazing or diffusion bonding is performed in such a temperature range the corrosion resistance of the stainless steel is significantly diminished.
SUMMARY OF THE INVENTION
The invention serves to solve the above-mentioned problems. It is an object of the invention to provide a composite bonded body in which metal beryllium, copper alloy and stainless steel are effectively bonded to each other without the problem relating to the sensitizing of the stainless steel, as well as an advantageous bonding method therefor.
The details of the development which resulted in the invention will be described below.
As mentioned above, the conventional method for bonding metal beryllium, copper alloy and stainless steel to each other is to bond a copper alloy to a structural body made of stainless steel in advance, and then further bond the metal beryllium to the bonded body of copper alloy and stainless steel.
The reason for this procedure is that is because a satisfactory bonded body can not be obtained when metal beryllium, copper alloy and stainless steel are to be bonded to each other simultaneously. More specifically, the preferable bonding temperature of copper alloy and stainless steel is a relatively high temperature of 850 to 1050° C., while the preferable bonding temperature of metal beryllium and copper alloy is a relatively low temperature of not higher than 800° C. Therefore, when the bonding is performed in the former case at relatively high temperatures beryllium and copper alloy react with each other to form a eutectic alloy having a low melting point causing the bonding surface to melt. On the other hand, when the bonding is performed in the latter case at low temperatures a sufficient bond between the copper alloy and the stainless steel is not achieved.
The inventors conducted thorough investigations for the purpose of solving the above-mentioned ambivalent problems, and arrived at the novel recognition that the above mentioned object of the invention can be advantageously achieved by interposing an insert material between the metal beryllium and copper alloy, which presents the formation of an eutectic alloy of a low melting temperature even when reacted with metal beryllium or stainless steel.
The invention is based on the above-mentioned recognition, and featured by the following constitutions.
1 A composite bonded body of metal beryllium, copper alloy and stainless steel, all of which are joined by a single diffusion bonding process with the stainless steel as a substrate, the copper alloy bonded to the surface of stainless steel, substrate and the metal beryllium bonded to the outer surface of said copper alloy.
2. A composite bonding method for bonding metal beryllium, copper alloy and stainless steel, all of which are sequentially depoisted on the outer surface and bonded to each other in this order, wherein an insert material is interposed between the metal beryllium and copper alloy, layers said insert material having the minimum solidus temperature of not lower than 870° C. relative to the metal beryllium and copper alloy, respectively, and a single diffusion bonding process is performed at a temperature not lower than 850° C. and less than the minimum solidus temperature, and at a pressure at 20 to 300 MPa, so that the metal beryllium, copper alloy and stainless steel are simultaneously bonded to each other.
3. A composite bonding method for bonding metal beryllium, copper alloy and stainless steel according to paragraph 2 above, wherein said insert material interposed between the metal beryllium and copper alloy is niobium metal.
4. A composite bonding method for bonding metal beryllium, copper alloy and stainless steel according to paragraph 2 above, wherein said insert material interposed between the metal beryllium and copper alloy is molybdenum metal.
5. A composite bonding method of metal beryllium, copper alloy and stainless steel according to paragraph 2 above, wherein said insert material interposed between the metal beryllium and copper alloy is titanium metal.
6. A composite bonding method of metal beryllium, copper alloy and stainless steel according to paragraph 2, 3, 4 or 5 above, wherein a nickel intermediate layer is formed between the stainless steel and copper alloy.
REFERENCES:
patent: 4830933 (1989-05-01), Hodes et al.
patent: 5820721 (1998-10-01), Beane et al.
patent: 5901336 (1999-05-01), Dombrowski
patent: 5972521 (1999-10-01), Huskamp et al.
patent: 0001173 (1978-05-01), None
patent: 3-251800 (1991-11-01), None
Burr & Brown
NGK Insulators Ltd.
Pittman Zidia T.
Ryan Patrick
LandOfFree
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