JPH0239470B2 - SERAMITSUKUSUKANTOARUMINIUMUKANNOSETSUGOHOHO - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of joining a ceramic tube and an aluminum tube.

Note that in this specification, the term aluminum is used to include aluminum alloys.

For example, in a cooling device for a rectifying element in a rectifier, there is an upper condensing part for heat dissipation, and an upper condensing part for mounting the rectifying element, which is connected to the upper condensing part and is filled with a liquid refrigerant such as Freon that evaporates at a temperature below the allowable upper limit temperature of the rectifying element. Generally, a ceramic tube as an electrical insulator is interposed in the communication pipe line between the lower evaporation section and the condensation section to prevent short circuits between the condensation sections during non-conducting periods of the element.
Care has been taken to avoid dangers due to insulation deterioration. In the case of a rectifier cooling device such as the one described above, in order to connect the ceramic tube to the upper condensing section and the lower evaporating section, it must be integrally joined to the ends of the metal connecting tubes. Must be. However, in cases where these connecting tubes are made of aluminum, it has not been possible to connect them directly to ceramic tubes in the past.
For example, by interposing a stainless steel pipe between them,
A method has been adopted in which the stainless steel tube is previously joined to an aluminum tube by a method such as friction welding, and then the stainless steel tube is joined to a ceramic tube using silver solder, solder glass, or the like. Of course, when such a joining method is used, a two-step joining operation of an aluminum pipe and a stainless steel pipe, and a stainless steel pipe and a ceramic pipe is required, and the work is extremely troublesome.

The present invention aims to provide a method for sufficiently firmly joining a ceramic tube to an aluminum tube in one step, in order to avoid the troublesome two-step joining operation described above. Based on this knowledge, we discovered that if we form a predetermined metal coating layer on the tube and then braze it with an aluminum brazing sheet, it is possible to achieve a sufficiently strong connection between the two tubes. It was completed based on the following.

That is, one of the methods for joining a ceramic tube and an aluminum tube according to the present invention is to apply Mo or Mo- to the end of the ceramic tube to be joined to the aluminum tube so as to cover the end with a substantially U-shaped cross section.
While forming a metal coating layer made of Mn alloy, an aluminum brazing sheet has an annular convex edge on its inner periphery that fits into the inner surface of the metal coating layer of the ceramic tube, and an aluminum brazing sheet on its outer periphery that fits into the inner surface of the metal coating layer of the aluminum tube. It is characterized in that it is formed into a ring shape with a crank-shaped cross section having an annular convex edge that fits on the outer surface of the end, and brazing is performed by arranging the ceramic tube and the aluminum tube abuttingly through the brazing sheet. Yet another invention is to further provide, on the metal coating layer of the ceramic tube,
The method is characterized in that after forming one or more plating layers made of a metal having good compatibility with both the coating layer and aluminum, brazing is performed using the brazing sheet.

A metal coating layer made of Mo or Mo-Mn alloy is generally formed by sintering the metal powder on ceramics, and its thickness is about 10 to 30μ, especially about 20μ. It is normal to do so. The coating has a substantially U-shaped cross section that continuously covers the end surface of the ceramic tube and both the inner and outer circumferential surfaces of the tube end, and the length of the inner coating portion is as described below. In relation to the length of the annular convex edge on the inner peripheral edge of the brazing sheet, the length is set to be slightly longer than that, while the length of the outer surface covering part is set to be extremely short, for example, about 3 mm. .

Aluminum brazing sheet is 2S,
It is possible to suitably use a known material such as 3S, which is made of an aluminum core material coated with Al-Si-Mg brazing filler metal on both sides, and by using this double-sided brazing sheet, the ceramic material on which the above-mentioned coating layer is formed can be used. On the other hand, it enables direct and strong brazing of aluminum materials. Here, the brazing sheet is applied to the inner surface of the end of the ceramic tube, in which a metal coating layer is formed on the inner and outer edges of the annular flat portion interposed between the butted end surfaces of the ceramic tube and the aluminum tube. A cross-sectional shape having a short cylindrical or annular convex edge that is fitted into the structure, and a similarly short cylindrical or annular convex edge that is opposite to this and is fitted into the structure on the outer surface of the end of the aluminum tube. It is formed in

Brazing through this brazing sheet is generally performed by a conventional vacuum brazing method, but is not limited to this method, and may also be performed by an inert gas brazing method, etc. Permissible.

The bonding strength of the bonded product is higher than that when only Mo or Mo-Mn coating layer is formed on the ceramic tube.
Further, by pre-plating both the coating layer and aluminum with a metal having good compatibility, it is possible to further increase the strength.
Metals suitable for forming such a plating layer include:
Specific examples include Al and Ni. Al
Comparing Ni and Ni plating layers, Al
Although a relatively better bonding strength can be obtained with a plated layer, it is more preferable to use a plated layer with Mo or Mo.
- After a first plating layer made of Ni is formed on the Mn alloy coating layer, a second plating layer made of Al is formed thereon.
Even stronger bonding strength can be obtained than in any case where a plating layer of Al alone is formed. The desired effect can be satisfactorily achieved by setting the thickness of these plating layers to be about 5 μm in a single layer.

According to this invention, it is possible to join a ceramic tube and an aluminum tube, and the joining process can be significantly simplified compared to the conventional method of joining in two steps with a stainless steel tube in the middle. It is possible to reduce the cost of the bonded product. Moreover, in the joint shape of the joint, the brazing sheet has a crank-shaped cross section, and the annular convex edges on both sides are fitted to the ends of the ceramic pipe and the aluminum pipe, so it is easy to The ceramic tube, the brazing sheet, and the aluminum tube can be easily and reliably set together, and since both tubes are joined not only on their end surfaces but also on their peripheral surfaces via the brazing sheet, the joint strength is high. Become. Furthermore, as a result of the annular convex edge of the brazing sheet being fitted inside the ceramic tube, the brazing sheet is pressed against the inner surface of the ceramic tube during brazing due to the difference in coefficient of linear expansion between the two, causing In addition to good bonding, fillets can be formed at the edges of the overlapping portions of the brazing sheet and the metal coating layer, and together with this, the bonding strength can be increased.

Next, embodiments of the invention will be described with reference to the drawings.

Embodiment 1 As shown in FIG. 1, aluminum tubes 2, 2 are to be joined to both ends of a short cylindrical ceramic tube 1 in a butt state,
To perform this joining, first, Mo powder is sintered on both ends of the ceramic tube 1 so as to cover the ends with a substantially U-shaped cross section, thereby forming a coating layer 3 having a thickness of 20 μm. The length of the inner surface coating portion 3a of this coating layer was 8 mm, and the length of the outer surface coating portion 3b was 3 mm.

On the other hand, Al-Si-Mg on both sides of the aluminum core material
A brazing sheet 4 with a thickness of 1.6 mm clad with brazing filler metal is used, and a diameter of 5 mm in length that fits inside the coating layer 3 on the inner peripheral edge is used.
It has an annular convex edge 4a with a diameter and a length of 5 to fit on the outer circumferential surface of the aluminum tube 2.
It was molded into a ring shape having an annular convex edge 4b of mm in cross section, that is, a cross section.

Then, the aluminum tubes 2, 2 were placed at both ends of the ceramic tube 1 so as to butt each other with the brazing sheet 4 interposed therebetween, and vacuum brazing treatment was performed. Here, the brazing conditions are a vacuum degree of 5
×10 ^-5 Torr, after preheating at 550℃ for 20 minutes, 610
Brazing was performed by heating at °C for 5 minutes, and then cooling in a furnace.

The resulting bonded product shown in FIG. 2 consists of the ceramic tube 1 and the aluminum tubes 2 and 2.
are sufficiently firmly bonded to each other, and the coating layer 3
Formation of a fillet 5 was observed at the edge of the overlapping portion of the brazing sheet 4 and the brazing sheet 4.

Example 2 As shown in FIG. 3, both ends of the ceramic tube 1 were coated in the same manner as in Example 1.
After sintering Mo--Mn powder to form a coating layer 13 with a thickness of 20 microns, a Ni plating layer 6 was further formed on the surface thereof, and brazing was performed in the same manner as in Example 1 except for the Ni plating layer 6. The bonded product thus obtained was slightly superior to that of Example 1 in terms of bonding strength.

Example 3 An Al plating layer was formed in place of the Ni plating layer 6 of Example 2, and brazing was performed in the same manner as in Example 2 except for the above. The bonded product thus obtained had even better bonding strength than the bonded product of Example 2.

Example 4 As shown in FIG. 4, a coating layer 13 made of Mo-Mn with a thickness of 20 μm was formed on both ends of the ceramic tube 1, and then Ni plating was applied to the surface to form a coating layer 13 with a thickness of 5 μm.
A first plating layer 16 is formed on the surface of the first plating layer 16.
A second plating layer 26 having a thickness of 5 μm was formed by plating. Thereafter, brazing was carried out in the same manner as in Example 1 above. The bonded products thus obtained had even better bonding strength than any of the above-mentioned Examples 1 to 3.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, and FIG. 1 is a longitudinal cross-sectional view of the first embodiment before joining;
Fig. 2 is a longitudinal sectional view of the state after joining, Fig. 3 is a longitudinal sectional view of the ceramic tube in the second and third embodiments, and Fig. 4 is a longitudinal sectional view of the ceramic tube in the fourth embodiment. be. 1... Ceramics tube, 2... Aluminum tube, 3, 13... Mo or Mo-Mn coating layer,
4... Blazing sheet, 6... Plating layer, 16
...first plating layer, 26...second plating layer.

Claims (1)

[Claims] 1. A metal coating layer made of Mo or Mo-Mn alloy is formed on the end of a ceramic tube to be joined to an aluminum tube so as to cover the end with a substantially U-shaped cross section. , an aluminum brazing sheet having an annular convex edge on the inner circumferential edge that fits into the inner surface of the metal coating layer of the ceramic tube, and an annular convex edge on the outer circumferential edge that fits on the outer surface of the tube end of the aluminum tube. 1. A method for joining a ceramic tube and an aluminum tube, characterized in that the ceramic tube and the aluminum tube are formed into a ring shape having a crank-shaped cross section, and the ceramic tube and the aluminum tube are arranged butt-like through the brazing sheet and brazed. 2. A metal coating layer made of Mo or Mo-Mn alloy is formed on the end of the ceramic tube to be joined to the aluminum tube so as to cover the peripheral wall of the end with a substantially U-shaped cross section, and then One or more plating layers made of a metal that is compatible with both the metal coating layer and aluminum are formed, while an aluminum brazing sheet is fitted on the inner peripheral edge of the metal coating layer of the ceramic tube. The ceramic tube and the aluminum tube are connected to each other through the brazing sheet. A method for joining ceramic tubes and aluminum tubes, which is characterized by arranging them in a butt shape and performing a brazing process. 3. The method for joining a ceramic tube and an aluminum tube according to claim 2, wherein the plating layer is made of aluminum. 4. The method for joining a ceramic tube and an aluminum tube according to claim 2, wherein the plating layer is made of nickel. 5. The method for joining a ceramic tube and an aluminum tube according to claim 2, wherein the plating layer comprises a first plating layer made of nickel and a second plating layer made of aluminum formed thereon.