JPH09182979A - Method for joining aluminum tube with copper tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To join two tubes firmly by thinning the thickness of tubes to be joined and preventing burrs from generating at the weld zone. SOLUTION: A tapered part 11 is formed at the end of a copper tube 10. A part of this tapered part 11 is inserted into the end of an aluminum tube 1. Then, while a part to be joined of both tubes 1, 10 is heated so as not to form an oxidized film on their surface, both tubes 1, 10, are pressed against each other. Then, both tubes 1, 10 are metallurgically joined in a state where the outer circumferential surface of the tapered part 11 of the copper tube 10 is at least partially superposed with the end of the other aluminum tube 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining an aluminum tube used in a heat exchanger and a copper tube for piping to a copper tube for piping.

[0002] In this specification, the term "aluminum" shall include aluminum alloys in addition to pure aluminum. The term "copper" includes copper alloy in addition to pure copper.

[0003]

2. Description of the Related Art As a method for joining an aluminum tube and a copper tube without using a brazing material or a brazing flux,
Conventionally, a flash butt welding method is known. In this flash butt welding method, the end faces of the aluminum pipe and the copper pipe are opposed to each other at a predetermined interval, the two pipes are slowly brought close to each other while a voltage is applied, and a flash is blown between the end faces. This is a method of metallurgically joining the two pipes by heating and pressurizing the ends.

[0004]

However, in the conventional flash butt welding method, it is necessary to make the wall thicknesses of both pipes to be joined at least about 1.25 mm, and for joining pipes thinner than that, it is necessary. There is a problem that it cannot be applied and the material cost becomes high. Further, according to the conventional flash butt welding method, burrs are generated at the joint portion of both pipes, and in particular, burrs protruding inward cannot be removed, so that the aluminum pipe of the heat exchanger and the copper pipe for piping are not able to be removed. When applied to joining with, the burrs could fall off due to the flow of fluid and flow into the compressor, causing a failure of the compressor.

An object of the present invention is to provide a method for joining an aluminum pipe and a copper pipe, which solves the above problems.

[0006]

A method for joining an aluminum pipe and a copper pipe according to the present invention is characterized in that a tapered taper portion is formed at an end of one of the aluminum pipe and the copper pipe, and Insert a part of the taper into the end of the other tube, and then heat at least one of the two tubes to be joined while heating them so that no oxide film is formed on the surfaces of both tubes. Are pressed against each other, and both pipes are metallurgically joined in a state in which at least a part of the outer peripheral surface of the tapered portion of the one pipe is overlapped with the end portion of the other pipe.

According to the above method, the aluminum pipe and the copper pipe can be joined to each other even if the wall thicknesses thereof are smaller than 1.25 mm. For example, it can be applied to joining pipes having a wall thickness of about 0.6 mm. Moreover, no burr is generated at the joint between the two pipes. Further, at least one of the two pipes to be joined is pressed against each other while heating the two pipes while heating so that an oxide film is not formed on the surfaces of both pipes, and at least a part of the tapered portion of one pipe is Since both pipes are metallurgically joined with the end of the other pipe superposed on the outer peripheral surface, an alloy layer of Al and Cu is generated at the joint interface of both pipes, and both pipes are firmly joined. To be done.

In the method of joining the aluminum pipe and the copper pipe, the heating may be performed by a neutral flame to prevent the formation of an oxide film on the pipe surface. By the way, there are three kinds of flames, which are usually carbonized flame, neutral flame and oxidative flame. Among them, carbonized flame is propane excess and produces a large amount of soot, which is not preferable. Further, the oxidizing flame is an oxygen excess flame, and the temperature of the flame is the highest, but it is not preferable because the flame vibrates violently and has an oxidizing property.
In addition, since the neutral flame has a thicker flame, the predetermined range can be efficiently heated.

In the method of joining the aluminum pipe and the copper pipe, the heating may be performed in an inert gas atmosphere to prevent the formation of an oxide film on the pipe surface. In this case, nitrogen gas or A
It is performed by filling it with an inert gas such as a rare gas such as r. The heating at this time is preferably performed by induction heating using an induction heating coil. This is because it is easy to control the heating.

In the method of joining the aluminum pipe and the copper pipe, the heating may be performed by a reducing flame to prevent the formation of an oxide film on the pipe surface.
In this case, as the reducing flame having a reducing property, for example, a flame of excess propane-air, a flame of excess propane-oxygen, or the like is used.

In the method of joining the aluminum pipe and the copper pipe, the heating is applied to at least one of the pipes in the atmosphere while vibrating, or both pipes are relatively rotated about the axis. However, this may prevent the formation of an oxide film on the tube surface. The heating in this case is also preferably performed by induction heating using an induction heating coil. This is because it is easy to control the heating.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.
This will be described with reference to the drawings.

In joining the aluminum pipe (1) and the copper pipe (10), first, the tapered taper portion (1
Form 1). For example, the aluminum tube (1) has an inner diameter of 7.2 mm and a wall thickness of about 0.6 mm, and the copper tube has an inner diameter of 7.0 mm and a wall thickness of 0.6 mm. Also, each tube
When the dimensions (1) and (10) are as described above, the length L of the taper portion (11) is 10 to 14 mm, and the taper angle is 1 to 30 degrees, preferably 1.5 to 3 degrees.

Then, a part of the tapered portion (11) of the copper pipe (10) on the tip side is inserted into the end of the aluminum pipe (1) (see FIG. 1).
reference). The length L1 of the portion of the tapered portion (11) of the copper pipe (10) existing outside the aluminum pipe (1) is about 7 to 8 mm.

Then, propane-air or propane-
A neutral flame (F) such as oxygen is used to heat the entire area in the range indicated by W in FIG. 1 at the ends of both tubes (1) and (10). The heating temperature is, for example, about 450 ° C. At this time, since a neutral flame (F) is used, no oxide film is formed on the surfaces of both tubes (1) and (10). Then, as described above, both tubes (1)
While heating the end of (10), press both pipes (1) and (10) against each other, and make all parts of taper (11) aluminum pipe.
(1) Push it in. At this time, the end portion of the aluminum pipe (1) becomes a divergent shape and the expanded portion (2) is formed.
(2) closely adheres to the base end side portion of the outer peripheral surface of the taper portion (11), and at this portion both pipes (1) and (10) are metallurgically joined in an overlapping manner (see FIG. 2). In this way, both pipes (1) and (10) are joined. Expanding part (2) and taper part (11) of both pipes (1) (10)
As shown in FIG.
An alloy layer (20) of Cu and Cu (eutectic composition of 33 wt% Cu-67 wt% Al) is formed, and the two pipes (1) and (10) are firmly joined.

In the above embodiment, heating may be performed by using a reducing flame such as a flame of excess propane-air or a flame of excess propane-oxygen, instead of the neutral flame (F). Also in this case, as in the case of the above embodiment, both pipes (1) and (10) are joined, and the expanded portion (2) and the tapered portion (11) of both pipes (1) and (10) are superposed. In the part, an alloy layer of Al and Cu (20) (3
3 wt% Cu-67 wt% Al eutectic composition)
(1) and (10) are firmly joined.

FIG. 4 shows another embodiment of the present invention.

In FIG. 4, the dimensions of the aluminum tube (1) and the copper tube (10) are the same as those in the embodiment shown in FIG. Then, a part of the tapered portion (11) of the copper pipe (10) on the tip side is inserted into the end of the aluminum pipe (1). The length of the taper portion (11) of the copper pipe (10) existing outside the aluminum pipe (1) is about 7 to 8 mm.

Then, an induction heating coil (30) is arranged around both the tubes (1) (10) so that the area shown by W in FIG. 4 can be heated.

Next, both tubes (1) (10) and the induction heating coil (30) are placed in a closed chamber (not shown), and a rare gas such as Ar or N ₂ gas is supplied into the closed chamber to supply an inert gas. In an atmosphere, the induction heating coil (30) heats the end portions of both tubes (1) and (10) in the range indicated by W in FIG. 4 over the entire circumference. The heating temperature is, for example, about 450 ° C. At this time, since heating is performed in an inert gas atmosphere, no oxide film is formed on the surfaces of both tubes (1) and (10). Then, while heating the ends of both pipes (1) and (10) as described above, both pipes (1) and (10) are pressed against each other, and all parts of the tapered portion (11) are placed inside the aluminum pipe (1). Push into. At this time, the end portion of the aluminum pipe (1) becomes a divergent shape to form a widened portion (2), and the widened portion (2) is located on the base end side portion of the outer peripheral surface of the tapered portion (11). Adhere closely, and in this part both tubes (1)
(10) is metallurgically bonded in a superposed manner. In this way, both pipes (1) and (10) are joined. Expansion of both pipes (1) (10)
In the overlapping part of (2) and taper part (11), Al
An alloy layer (20) of Cu and Cu (eutectic composition of 33 wt% Cu-67 wt% Al) is formed, and the two pipes (1) and (10) are firmly joined.

In the above other embodiment, the heating by the induction heating coil (30) may be performed in the atmosphere. That is, both tubes (1) (10) and the induction heating coil (30) are placed in the atmosphere, and heating is performed by the induction heating coil (30). This heating is performed by applying vibration to at least one of the tubes (1) and (10), or by rotating the tubes (1) and (10) relatively around the axis. Also in this case, as in the case of the other embodiments described above, the two pipes (1) and (10) are joined, and the expanded portion (2) and the tapered portion (11) of both pipes (1) and (10) are connected. In the overlapping portion, an alloy layer (20) of Al and Cu (33 wt% C
u-67 wt% Al eutectic composition) is produced, and both tubes (1) (10)
Are firmly joined.

In the above, the tapered portion (11) is formed in the copper pipe (10), and a part of the tapered portion (11) on the tip side is inserted into the end portion of the aluminum pipe (1). Conversely, a tapered portion may be formed on the aluminum tube (1), and a part of the tapered portion on the tip side may be inserted into the end of the copper tube (10). In this case, the other conditions may be the same as those described above.

[0023]

According to the method for joining an aluminum pipe and a copper pipe of the present invention, as described above, the both pipes can be joined even if the aluminum pipe and the copper pipe are thinner than 1.25 mm each. You can Therefore, the material cost can be reduced. Moreover, since burrs do not occur at the joint portion of both pipes, it is possible to prevent burrs protruding inward from being mixed in the fluid flowing through both pipes. Therefore, for example, when applied to the joining of the aluminum pipe of the heat exchanger and the copper pipe for piping, the burr protruding inward is dropped by the fluid,
It will not enter the compressor and cause a failure of it. In addition, there is no oxide film on the joint interface of both pipes.
Since an alloy layer of 1 and Cu is formed, both tubes are firmly joined.

[Brief description of the drawings]

FIG. 1 is a partially enlarged vertical sectional view showing an embodiment of the present invention, in which a part of a tapered portion of a copper pipe is inserted into an end portion of an aluminum pipe.

FIG. 2 is a partially enlarged vertical sectional view showing a state in which an aluminum pipe and a copper pipe are joined together.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is a partially enlarged vertical cross-sectional view showing another embodiment of the present invention, in which a part of the tapered portion of the copper tube is inserted into the end portion of the aluminum tube.

[Explanation of symbols]

 (1) Aluminum tube (10) Copper tube (11) Taper section

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical indication location // B23K 101: 06 103: 18 (72) Inventor Shigeru Oyama 6-224 Kaiyama-cho, Sakai City Showa Within Arminium Co., Ltd.

Claims (5)

[Claims] 1. A tapered taper portion is formed at an end of one of an aluminum pipe and a copper pipe,
Insert a part of this taper into the end of the other tube, and then heat at least one of the two tubes to be joined while heating them so that no oxide film is formed on the surfaces of both tubes. The aluminum pipe and the copper pipe are characterized in that the pipes are pressed against each other, and both pipes are metallurgically joined in a state in which at least part of the outer peripheral surface of the tapered portion of one pipe is overlapped with the end portion of the other pipe. How to join. 2. The method for joining an aluminum pipe and a copper pipe according to claim 1, wherein the heating is performed by a neutral flame to prevent the formation of an oxide film on the pipe surface. 3. The method for joining an aluminum pipe and a copper pipe according to claim 1, wherein the heating is performed in an inert gas atmosphere to prevent the formation of an oxide film on the pipe surface. 4. The method for joining an aluminum tube and a copper tube according to claim 1, wherein the heating is performed by a reducing flame to prevent the formation of an oxide film on the tube surface. 5. The heating is performed in the atmosphere while applying vibration to at least one of the tubes, or while rotating both tubes relatively around an axis, whereby the oxide film on the tube surface is formed. The method for joining an aluminum pipe and a copper pipe according to claim 1, which prevents generation.