JPH0371973A - Method for brazing tubes - Google Patents

Abstract

PURPOSE:To stabilize joining accuracy of tubes by storing a low melting point alloy on the almost overall periphery of a void part and then, heating a fitting part of each tube to melt the alloy in the void part. CONSTITUTION:One tube 10 and the other tube 10 are fitted to each other with a fine gap held and the annular void part 14 is formed on an intermediate part in the axial direction of the fitting part of both pipes. Each bent tube end 13 of a bent tube 12 where ring brazing filler metal 15 is fitted is fitted to an end of the straight pipe 10, in other words, the inside of a straight tube end 11 and then, a part of the edge of the straight tube end 11 is calked in the axial direction and the bent pipe 12 is prevented from coming out by this calked part 11a and the void part 14 is blocked up and almost closed up tightly from the outside. As a result, the molten low melting point alloy 15 stays temporarily in the void part 14 and penetrates into the fitting part of both pipes 10 by a capillary phenomenon from this part. Accordingly, since the molten low melting point alloys 15 does not leak to the outside and incline to the peripheral direction, joining accuracy of the tubes is stabilized and reliability is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of brazing pipes together, which is applied, for example, when forming pipes for a heat exchanger.

(Prior Art) As a conventional method of brazing pipes of a heat exchanger, there is a method shown in FIGS. 6 to 9.

Fig. 6 shows a first conventional example, in which A is a pipe unit for a heat exchanger, in which a large number of copper alloy straight pipes 1 arranged in parallel are connected to a large number of copper alloy pipes 1 curved in a U-shape. bent pipe 2
A large number of fins 3 are connected in series and fitted around the outer periphery of the straight pipe 1.

The bent pipe 2 is constructed by fitting a ring solder 4 formed into a ring shape and made of phosphor copper solder to both ends of the bent pipe 2, that is, both ends 2a of the straight pipe 1. The ring solder 4 is brought into contact with the shaft end surface 1b of each straight pipe 1 by keeping a small gap between the ends, that is, the inner surface of each straight pipe end 1a.

Next, as shown in FIG. 7, the pipe unit A is placed in a heating furnace 5 and heated to 735 DEG C. to 840 DEG C. to melt the ring solder 4.

This melted ring solder 4 is applied to the straight pipe end 1a and the curved pipe end 2.
It penetrates into the fitting part with a and joins both.

FIG. 8 shows a second conventional example.

This product has a tapered portion 1c that expands outward in a tapered shape at the outer end of the straight pipe end 1a.
The curved tube end 2a is fitted to the inner surface with a small gap maintained, and the ring solder 4 fitted to the curved tube end 2a is fitted into the tapered portion 1C.

Next, the entire body is heated to a predetermined temperature in a heating furnace 5 to melt the ring solder 4, and the molten ring solder 4 is infiltrated into the fitting portion of each straight pipe end 1a and curved pipe end 2a to bond them together. Join.

FIG. 9 shows a third conventional example.

This has a large-diameter, annular flange 2b bulgingly formed at the base of the curved pipe end 2a, and the curved pipe end 2a is fitted onto the inner surface of the straight pipe end 1a with a small gap. , the ring solder 4 fitted to the bent pipe end 2a is held between the end face of the straight pipe 1 and the flange part 2b of the curved pipe 2.

Next, the entire body is heated to a predetermined temperature in a heating furnace 5 to melt the ring solder 4, and the molten ring solder 4 is infiltrated into the fitting portion of each straight pipe end 1a and curved pipe end 2a to bond them together. Join.

(Problems to be Solved by the Invention) The first and second conventional examples described above have a ring wax 4
The outer surface (right side) of the solder ring 4 is exposed to the outside, and in the case of the third conventional example, the outer circumferential surface of the solder ring 4 is exposed to the outside, so it may be biased to one side in the circumferential direction due to gravity when melting.
Some of the melted wax may leak outside.

This increases the variation in bonding accuracy.

This has the disadvantage that reliability is poor and the number of parts that need to be repaired after brazing increases.

The object of the present invention is to provide a novel method for brazing pipes together that eliminates the above-mentioned drawbacks.

(Means for Solving the Problems) In order to achieve the above object, the present invention fits one pipe and the other pipe while maintaining a small gap, and the axis of the fitting portion of both pipes. An annular cavity is formed in the middle part in the direction, and a low melting point alloy is accommodated around the entire circumference of this cavity, and then the fitting part of each pipe is heated to melt the alloy in the cavity. be.

(Function) Since the present invention has an upper V configuration, the void portion is
The fitting portions of each pipe are closed by the fitting portions on both sides in the axial direction, and are substantially sealed from the outside.

Therefore, the molten low-melting point alloy remains temporarily in the above-mentioned gap, and gradually penetrates from this part into the fitting part of both pipes by capillary action 1.

(Example) Embodiments of the present invention will be described below based on the drawings.

In the drawings, FIG. 1 is a cross-sectional view of the main parts of the first embodiment of the present invention in a pipe fitted state, FIG. 2 is a partially enlarged cross-sectional view showing the pipe in a locked state, and FIG. 3 is a brazing process. FIG. 4 is a sectional view of the main part of the second embodiment of the present invention in a pipe-fitted state, and FIG. S is a sectional view of the main part of the third embodiment of the present invention in the pipe-fitted state. It is.

In FIG. 1, B is a pipe unit for a heat exchanger, in which straight pipes 10 of many copper alloy layers arranged in parallel are connected in series by curved pipes 12 of many copper alloy layers curved in a U-shape. A large number of fins 16 are fitted around the outer periphery of the straight pipe 10.

The bent tube 12 has both ends, that is, both tube ends 13, bulged to a large diameter, and its outer diameter is slightly smaller than the inner diameter of the straight tube 10. A small-diameter constriction 13a is formed near the base, and this constriction 1
3a forms an annular gap 4 at the fitting portion with the straight pipe 10.

Further, a ring solder 15 made of a low melting point alloy material, such as phosphor copper solder, formed into a ring shape is fitted onto the outer periphery of each constricted portion 13a. The outer diameter of this ring solder lL5 is the curved pipe 12
It is formed to have approximately the same diameter as the outer diameter of the curved pipe end 13.

Then, after fitting each bent pipe end 13 of the bent pipe 12 into which the ring solder 15 has been fitted into the straight pipe end 11 of each straight pipe 10, as shown in FIG. A part of the edge of the straight pipe end portion 11 is caulked in the axial direction, and the bent pipe l2 is prevented from being pulled out by this caulking portion 11a.

Next, as shown in FIG. 3, the pipe unit B assembled as described in Section 2 is placed in a heating furnace (electric furnace) 17 and heated to 735°C to 840°C, and the ring solder 1
5 is melted, and the molten ring braze 5 is infiltrated into the minute gap of the fitting portion between each straight pipe end 11 and bent pipe end 13 to join them together. In addition, 1-7a in FIG. 3 is a mesh belt, which supports the pipe unit B and allows it to pass through the heating furnace 17 at a predetermined speed.

The mounting structure for the ring solder 15 described above may be as shown in FIGS. 4 and 5.

That is, as shown in FIG. 4, the straight pipe end 11 and the curved pipe end 1
3, the outer end of the straight pipe end]-1 is the large diameter part 1.
1b, the inner end of the curved pipe end 13 is formed into a large diameter flange 13b, and the fitting part of the inner end of the straight pipe end [1] and the outer end of the curved pipe end 13 is formed. An annular cavity 14 may be formed between the large diameter part 11b and the fitting part of the flange part 3b, and a ring solder 15 may be interposed in this cavity 14.

Further, as shown in FIG. 5, the end of the large-diameter curved pipe 12 is narrowed to a small diameter to form a small-diameter curved pipe end 13, and the straight pipe end 11 is narrowed to a small diameter.
The outer end of the large diameter part 11b is formed into a large diameter part 11b.
1b to the large-diameter outer end 12a of the curved pipe 12, the inner end of the straight pipe end 1 and the fitting part of the curved pipe end 13, and the large diameter of the straight pipe end 11 An annular gap 14 may be formed between the portion 11b and the large-diameter outer end 12a of the bent pipe 12, and the ring solder 5 may be interposed in the gap 14.

According to the above embodiment, the ring solder 15 is accommodated in the cavity 14 that is substantially sealed from the outside, so when it is melted in the heating furnace F, the melted ring solder 1
5 temporarily stays in the cavity 14, and then flows from this part toward the fitting parts on both sides in the axial direction by capillary action, joining the straight pipe end 11 and the curved pipe end 13 to each other. I will do it.

Note that the present invention can also be applied to pipes for radiators.

(Effects of the Invention) As is clear from the above description, according to the present invention, the molten low melting point alloy will not leak to the outside or be biased in the circumferential direction, so the joining accuracy between pipes will be stabilized. This has the effect of increasing reliability and eliminating the need for repairs after brazing.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main part of the first embodiment of the present invention in a pipe fitted state, Fig. 2 is a partial enlarged sectional view showing the pipe in a locked state, and Fig. 3 is a schematic diagram showing the brazing process. Figure, 4th
FIG. 5 is a sectional view of the main part of the pipe fitting state showing the second embodiment of the present invention, FIG. 5 is a sectional view of the main part of the pipe fitting state showing the third embodiment of the invention, and FIG. 6 is the conventional FIG. 7 is a schematic diagram showing the brazing process; FIG. 8 is a cross-sectional view of the main part in a pipe-fitted state showing the second conventional example; FIG. 9 is a sectional view of a main part of a third conventional example in a state where pipes are fitted. B: Pipe unit, 1-0: Straight pipe, 11: Straight pipe end,
11a: Caulked part, 12: Bent pipe, Work 3: Bent pipe end, 13
a: constriction, 14: void, 15 = ring solder (low melting point alloy), 16: fin, 17: heating furnace, 17a: mesh belt. Application agent Hisashi Matsumoto■ Figure Figure 5 Figure Figure 7 Figure 7

Claims (1)

[Claims] 1. One pipe and the other pipe are fitted to each other with a small gap maintained, and an annular gap is formed in the axially intermediate part of the fitting part of both pipes, and approximately the entire circumference of this gap is formed. A method for brazing pipes together, characterized in that a low melting point alloy is placed in the pipe, and then the fitting part of each pipe is heated to melt the alloy in the gap.