JPH10296433A - High frequency brazing method for aluminum tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high frequency brazing method for an aluminum tube capable of surely and satisfactorily joining both tubes without generating a crack in a socket part in inserting a tip part of one of an aluminum tube into an expanded socket of the other aluminum tube and subjecting to high frequency brazing. SOLUTION: An end part of one of an aluminum tube 1 is inserted into an expanded socket part 21 of the other aluminum tube 2, both tubes are subjected to high frequency brazing. At a state a clearance for a brazing filler metal exists between an inner peripheral face of the socket part 21 and an outer peripheral face of a tube end part to be inserted therein, further at a state a clearance 5 for crack prevention exists between an inner bottom face 21a of the socket part and a tube end face 1a, by inserting an end part of one of the tube 1 into the other tube socket part 21 and subjecting to high frequency brazing to melt/fill a brazing filler metal 3 into the clearance for brazing filler metal filling, both tubes 1, 2 are joined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency brazing method for aluminum pipes.

[0002] In this specification, the term aluminum is used to mean its alloy.

[0003]

2. Description of the Related Art Aluminum has advantages such as excellent corrosion resistance and light weight, and is widely used as a general industrial material in addition to household appliances, automobile industry, aerospace industry and the like. .

Conventionally, when joining such aluminum pipes, TIG welding or gas brazing has been exclusively used.

However, in the TIG welding as described above,
Pinholes are easy to appear because the base material is melted and overlaid,
For this reason, there is a possibility that skill is required for the operation, or burrs may be formed on the inner surface of the joint to hinder smooth circulation of the refrigerant or the like. For this purpose, as shown in FIG. 5, a short cylindrical joint pipe (30) having a flange (31) made of SUS or the like is provided inside the joint between the aluminum pipes, and the two aluminum pipes (41) and (42) are connected to each other. It was necessary to insert until the end face came into contact with the flange portion (31) and perform welding with the joint pipe (30) interposed. For this reason, the joint pipe (30) is required, which increases the cost, and furthermore, the joint pipe (30) remains inside the pipe of the joined product, so that when a fluid passes through the pipe, it becomes a passage obstruction. There were drawbacks.

On the other hand, the gas brazing method has the following disadvantages. That is, when brazing aluminum material,
It is necessary to heat to a temperature higher than the melting point of the brazing material and lower than the melting point of the base material. However, since the melting point of the brazing material and the melting point of the base material are close to each other, the allowable range of the additional heat temperature of the brazing material is about 40. ° C
Extremely narrow with degree. However, the gas brazing method has a drawback that it is not easy to keep the brazing temperature within the above temperature range due to the influence of gas radiant heat, and it is difficult to uniformly heat the brazing temperature. Therefore, skill is required to perform good brazing. there were.

Accordingly, the present applicant has proposed a method of brazing an aluminum pipe by high-frequency induction heating (Japanese Patent Application Laid-Open No. 5-261526).

According to such a high-frequency induction heating system,
Since the brazing portion can be uniformly heated to a predetermined temperature without unevenness, problems such as those encountered in TIG welding and gas brazing can be eliminated.

[0009]

However, when aluminum pipes are brazed by such high-frequency brazing, particularly, the leading end of one aluminum pipe is connected to the enlarged-diameter socket formed on the other aluminum pipe. In the case of inserting and brazing the socket portion or its vicinity by high-frequency heating, and filling the gap between the outer peripheral surface of one pipe tip and the inner peripheral surface of the other pipe socket portion with a brazing filler metal, the cooling step after heating This causes a new problem that a crack may occur in the socket portion.

The present invention has been made in view of such a technical background, and when a tip of one aluminum pipe is inserted into a large-diameter socket of the other aluminum pipe and high-frequency brazing is performed, An object of the present invention is to provide a high-frequency brazing method for an aluminum pipe capable of reliably and satisfactorily joining both pipes without generating a crack in a socket portion.

[0011]

SUMMARY OF THE INVENTION The above object is achieved by inserting the tip of one aluminum pipe into the enlarged diameter socket of the other aluminum pipe and brazing the two pipes with high frequency. In a mode in which there is a gap for filling the brazing filler metal between the peripheral surface and the outer peripheral surface of the tip end of the pipe inserted into the socket portion, and a gap for preventing cracks between the inner bottom surface of the socket portion and the pipe end surface In the aspect where there is, by inserting the tip of one pipe into the other pipe socket part, in this state, high-frequency heating of the socket part or the vicinity thereof, by melting and filling the brazing material into the gap for filling the brazing material. This is achieved by a high-frequency brazing method for aluminum pipes, which comprises joining a pipe end and a socket.

In such a method, the presence of the crack preventing gap prevents the occurrence of cracks in the socket portion. Further, the brazing material sufficiently flows into the gap for filling the brazing material, so that the brazing of the two pipes is achieved.

[0013] In this case, the size of the gap for preventing cracking is 10 times the outer diameter of the tip of the pipe inserted into the socket.
% Is desirable in that the effect of preventing cracks can be more reliably exerted.

Further, a ring-shaped brazing material is fitted into the outer peripheral surface of the pipe end portion in a press-contact state, and the insertion-side end of the pipe is inserted into the socket portion until the ring-shaped brazing material contacts the opening of the socket portion. In the case where a gap for crack prevention is ensured by insertion, the brazing material functions as a positioning member, and the gap for crack prevention is automatically and accurately secured.

[0015]

Next, an embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, reference numerals (1) and (2) denote aluminum pipes having a circular cross section and the same diameter to be joined, the end of one aluminum pipe (1) and the end of the other aluminum pipe (2). The socket part (21) is joined.

The socket portion (21) holds the end of one of the aluminum pipes (1) in an inserted state, and has a diameter larger than that of the main body of the aluminum pipe (2) to be inserted. It has an inner diameter larger than the outer diameter of the end of the pipe (1). Therefore, when the end of the aluminum pipe (1) is inserted into the socket (21), as shown in FIG. 2, the outer peripheral surface of the inner pipe (1) and the inside of the socket (21) of the outer pipe (2). A gap (4) for infiltration and filling of the brazing material (3) is formed between the gap and the peripheral surface, and the size L1 of the gap (4) is 0.1 to 0.3.
It is preferably set to mm. If the gap L1 is less than 0.1 mm, the joint will be overheated, and if it exceeds 0.3 mm, there will be insufficient heating, and no good brazing can be obtained.

The front end opening of the socket portion (21) is further expanded in a trumpet shape to form a flare portion (22). As will be described later, the flare portion (22) is a portion where the ring-shaped brazing material (3) is arranged in contact with the brazing material, and the brazing material filling gap (4) of the brazing material (3) melted by high-frequency induction heating. In order to promote penetration into
The opening angle 2) (the angle θ with respect to the length direction of the socket) is preferably set to 45 to 60 degrees.

The high-frequency brazing of the two aluminum pipes (1) and (2) as described above is performed as follows. That is, the ring-shaped brazing material (3) is fitted into the end portion of the aluminum pipe (1) on the insertion side in a pressed state so as not to easily move. The brazing material (3) may be made of an Al-Si alloy.

Next, after the flux is applied, the end of the aluminum pipe (1) into which the brazing material has been fitted is inserted into the socket (21) of the other aluminum pipe (2). Insertion is performed until the ring-shaped brazing material (3) comes into contact with the flare portion (22) of the socket portion (21) as shown in FIG. Thus, in this inserted state, the end surface (1a) of the aluminum pipe (1) on the insertion side and the inner bottom surface (21a) of the socket portion (21), that is, the insertion side end surface (1a) as shown by a broken line in FIG. A gap (5) must be present between the contact portion (21a) when the connector is inserted until it contacts the socket portion (21). The gap (5) functions to prevent cracking of the socket (21). If the gap (5) does not exist, a crack occurs in the socket (21). The reason is presumed as follows.

That is, when the two pipes (1) and (2) are subjected to high-frequency induction heating in the socket part (21) and the vicinity thereof, the temperature rise is caused by the part of the pipe (1) not inserted into the socket part and the pipe (2). In the socket portion (21), the temperature rise of the portion fitted into the socket portion (21) is small. Therefore, the socket (21)
Is thermally expanded in the diameter increasing direction, the gap (4) for filling the brazing filler metal between the pipes (1) and (2) is widened, and a large amount of the molten ring-shaped brazing filler metal (3) penetrates into the gap (4). . After heating,
The socket (21) is cooled to gradually narrow the brazing filler gap (4) and the brazing filler metal (3) filled in the gap (4) gradually solidifies.
The end face (1) of the aluminum pipe (1) inserted in 1)
When a) is in contact with the inner bottom surface (21a) of the socket portion (21), the brazing filler gap (4) is closed at this portion, and therefore the brazing filler gap (4) is closed. As the space becomes narrower, there is no escape for the brazing material (3), and as a result, a pressure in the radial direction is applied to the inner peripheral surface of the socket (21). Then, it is presumed that the pressure increases with the progress of the cooling, and eventually cannot withstand this and cracks occur in the socket portion (21).
On the other hand, as in the present invention, the end surface (1a) of the aluminum pipe (1) inserted into the socket portion (21) does not contact the inner bottom surface (21a) of the socket portion (21), and the end surface (1a) does not come into contact. ) And the inner bottom surface (21a), the gap (4) is filled even if the gap (4) for filling the brazing material gradually narrows as the cooling progresses. The material (3) escapes through the gap (5) between the end surface (1a) and the inner bottom surface (21a). Therefore, the socket portion (2
It is presumed that no large pressure in the diameter-expanding direction acts on the inner peripheral surface of 1), and no cracks occur in the socket portion (21) even after complete cooling.

As described above, the end face (1a) of the pipe (1) inserted into the socket (21) and the socket (21)
The gap (5) between the inner surface and the inner bottom surface (21a) functions to prevent cracks. However, if the gap (5) is too small, the crack preventing effect is inferior. It is desirable that the size L2 of (5) be at least 10% of the outer diameter of the insertion end of the aluminum pipe (1) inserted into the socket (21). Such cracks in the socket portion (21) are caused by the pipe (1)
This is likely to occur when the thickness of (2) is as thin as less than 1 mm, especially as 0.6 mm or less. Therefore, the present invention is particularly suitable for brazing such a thin aluminum pipe.

As can be seen from the above description, the position of the ring-shaped brazing material (3) in the length direction of the aluminum pipe (1) is such that the end of one aluminum pipe (1) is connected to the other aluminum pipe (2). Socket part (21)
And the ring-shaped brazing material (3) is flared (22).
Is set so that a predetermined crack preventing gap (5) is secured when the contact is made. Further, since the ring-shaped brazing material (3) is tightly fitted to the pipe (1) in a press-contact state, the ring-shaped brazing material (3) has a flare portion (2).
Even if it is inserted into the socket (21) until it comes into contact with 2),
Further insertion of the pipe (1) is prevented, and the crack preventing gap (5) is reliably ensured.

Next, in the state of being inserted into the socket portion (21), the size of the brazing filler gap (4) is changed to the size of the pipe (1).
(2) Securely fix with a fixing jig so as to be uniform in the circumferential direction. If the size of the brazing filler gap (4) is not uniform in the circumferential direction, the brazing material cannot be uniformly heated and a good brazing state cannot be obtained.

Next, as shown in FIG. 3, a high-frequency induction coil (10) is arranged at the socket portion (21) to be joined or in the vicinity thereof, and both pipes (1) and (2) are subjected to high-frequency induction heating. . In the high-frequency induction heating method, the joint is placed in a coil that passes high-frequency current, and an aluminum pipe (1)
This is a method of heating by eddy current generated in (2). Here, the used coil (10) may be an annular coil, of course, but it is necessary to pass an aluminum pipe through the coil. Further, in the case where a part of the annular coil is formed in a left-right split type which can be closed and opened, the structure becomes complicated. Therefore, preferably, a horseshoe-shaped coil (1) as shown in FIG. 3 is used as a coil having a simple structure and capable of easily brazing a long pipe and having good heating efficiency.
0) should be adopted.

That is, in FIG. 3, reference numeral (10) denotes an output coil. This coil is formed by bending a copper circular pipe having a surface insulated by a ceramic coating into an inverted U shape in a front view and a U shape in a side view over two turns. It is.
In the illustrated embodiment, the coil (10) is constituted by a pipe having a circular cross section, but may be a pipe having a rectangular cross section.
In addition, although a two-turn configuration having two reciprocations is shown, a one-return configuration or a three-return configuration may be used.

After setting the coil (10) so that the socket (21) and the brazing material (3) are located in the work holding space (11), a high-frequency current is passed through the coil (10), (21) and its vicinity are heated. The heating temperature (brazing temperature) is generally 600 to 6
It is set to about 20 ° C. A radiation thermometer (not shown) is used to measure the temperature of the joint so that the heating temperature is as described above.
The heating by the high-frequency induction heating method is performed while performing temperature control by monitoring with the use of the like. The ring-shaped brazing material (3) is melted by heating, and as shown in FIG. 4, the gap for filling the brazing material (4) between the inner pipe (2) and the outer socket portion (21) is penetrated by capillary action. I do.

After the heating, the socket (2)
1) is gradually cooled, and the molten brazing material filled in the brazing filler gap (4) is also cooled and solidified, but the end surface (1a) of the insertion pipe (1) and the inner bottom surface (21a) of the socket portion (21). The cracks in the socket (21) are prevented by the presence of the crack preventing gap (5) between the two pipes (1).
(2) is satisfactorily joined.

Incidentally, of two pipes made of JIS6061Al having a thickness of 0.6 mm and an outer diameter of 8 mm, the end of one pipe (2) is expanded to an inner diameter of 8.4 mm to form a socket part (21). And the socket (2
The tip of (1) is further expanded in a trumpet shape to form a flare (2).
2) was formed. The opening angle θ of the flare portion (22) is 55
Set to degree.

On the other hand, a ring-shaped brazing material (3) having a diameter of 1.6 mm and made of an Al-Si brazing material is pressed against the peripheral surface of the pipe (1) at a predetermined position at the insertion end of the pipe (1). It was tightly fitted. Then, after applying a fluoride-based flux to the joint portion, the brazing material (3) is attached to the socket portion (2).
Until it comes into contact with the flare section (22) of 1), the socket section (2)
Inserted in 1). In this insertion state, a 2.0 mm crack preventing gap (5) was left between the end face (1a) of the pipe on the insertion side and the inner bottom surface (21a) of the socket (21).

The brazing filler gap (4) (size: 0.2 mm) between the outer peripheral surface of the inner pipe (1) and the inner peripheral surface of the socket (21) is made uniform. Pipes (1) and (2) were firmly positioned.

Next, in the work holding space (11) of the output coil (10), the socket (21) and the brazing material (3) are provided.
The output coil was set so that is positioned.

Then, while monitoring the temperature of the joint using a radiation thermometer, the joint was subjected to high-frequency induction heating. Heating is
620 ℃ for brazing temperature range (610 ℃ ± 10 ℃)
The temperature was set at

Observation of the brazed portion after brazing revealed that no cracks occurred in the socket portion (21), and that the brazing material spread over the filling gap (4), and extremely good brazing was performed. Had been

On the other hand, except that the end surface (1a) of the insertion side pipe (1) is brought into contact with the inner bottom surface (21a) of the socket portion (21) to form no crack preventing gap (5). When brazing was performed in the same manner as above, cracks occurred in the socket portion (21).

[0036]

According to the high-frequency brazing method according to the present invention, as described above, the gap for filling the brazing filler material is provided between the inner peripheral surface of the socket and the outer peripheral surface of the end of the pipe inserted into the socket. Is inserted, and the insertion-side end of one pipe is inserted into the other pipe socket in a state where a gap for preventing cracks exists between the inner bottom surface of the socket and the pipe end. Then, the socket part or its vicinity is heated by high-frequency wave and the gap for filling the filler material is melt-filled with the brazing material, thereby joining the insertion end of the pipe and the socket part. Therefore, the presence of the crack preventing gap can prevent the socket portion from cracking and can sufficiently pour the brazing material into the brazing filler filling gap, thereby obtaining a strong joint state. .

In particular, the size of the gap for preventing cracks is
When the outer diameter of the pipe is set to 10% or more of the outer diameter of the tip of the pipe inserted into the socket, there is an effect that the crack can be more effectively prevented from being generated in the socket.

Further, a ring-shaped brazing material is fitted into the outer peripheral surface of the pipe end in a press-contact state, and the insertion end of the pipe is inserted into the socket until the ring-shaped brazing material contacts the opening of the socket. In the case where a gap for crack prevention is secured by insertion, the brazing filler metal can be used for positioning, so that the gap for crack prevention can be secured automatically and accurately, and the pipe Brazing work can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a state before one pipe is inserted into a socket of another pipe.

FIG. 2 is an enlarged sectional view of the socket after insertion.

FIG. 3A is a front view showing a state in which a pipe is set on a high-frequency induction coil, and FIG.
It is sectional drawing in the state cut | disconnected by the III line.

FIG. 4 is an enlarged cross-sectional view of a brazing portion after brazing.

FIG. 5 is a perspective view showing a conventional brazing method, in which (a) is a perspective view before the two pipes are combined, and (b) is a cross-sectional view after the combination.

[Explanation of symbols]

 1, 2 ... Aluminum pipe 21 ... Socket part 22 ... Flare part 3 ... Brazing material 4 ... Gap for filling with brazing material 5 ... Gap for preventing cracks 10 ... Coil

Claims (3)

[Claims] 1. An end portion of one aluminum pipe (1) is inserted into an enlarged-diameter socket portion (21) of the other aluminum pipe (2). 21) and the socket portion (2).
In a mode in which there is a gap (4) for filling the brazing filler metal between the outer peripheral surface of the pipe end inserted into 1), and the inner bottom surface (21a) of the socket portion (21) and the pipe end surface (1a). The end of one pipe (1) is connected to the other pipe socket (2) in such a manner that a gap (5) for preventing cracks exists between them.
1), and in this state, the socket part (21) or the vicinity thereof is subjected to high-frequency heating, and the gap (4) for filling with the brazing filler metal is melt-filled with the brazing filler metal (3). (2) A method for high-frequency brazing aluminum pipes, which comprises joining (2). 2. A crack according to claim 1, wherein the size of the gap for preventing cracks is set to be at least 10% of the outer diameter of the end of the pipe inserted into the socket. The high-frequency brazing method of the aluminum pipe described in the above. 3. A ring-shaped brazing material (3) is fitted into an outer peripheral surface of an end of the pipe (1) in a press-contact state, and the ring-shaped brazing material (3) is brought into contact with an opening of a socket (21). Until the pipe (1) is in contact with the socket (2)
3. A gap (5) for preventing cracks by being inserted in (1).
The high-frequency brazing method for an aluminum pipe according to the above item.