JPH0957433A - Fin brazing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To facilitate the brazing of excellent quality of a heat transfer fin to a flat tube. SOLUTION: A sheet brazing filler metal 4 to which heat transfer fins 2a, 2b are temporarily fitted by a heat transfer fin temporary fitting claw 4a slit- formed at the prescribed position is lapped on a flat tube and heated. The sheet brazing filler metal 4 positions the heat transfer fins 2a, 2b until it is melted. When the brazing filler metal is melted, it is filled in the clearance between the heat transfer fins 2a, 2b and the flat tube to joint them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brazing method suitable for brazing a large joint area, and in particular, brazing suitable for joining heat transfer fins in high performance heat transfer tubes used in various heat exchangers. Regarding the method.

[0002]

2. Description of the Related Art For brazing, in general, the technical literature "Production Technology for Brazing", Production Technology Editing Committee for Brazing
Edition, published by Welding Newspaper, "82.5, Chapter 7, P223-P2
24 ", there are a brazing method and a placement brazing method depending on the method of supplying the brazing filler metal.

In the production of high-performance heat transfer tubes, the heat transfer fins are joined to the flat tubes by brazing so that the joints are uniformly heated to allow the brazing material to penetrate into the gaps. In order to guarantee the internal quality of the brazed joint, it is necessary to infiltrate the brazing filler metal, and it is necessary to keep the gap between the welded members within 0.05 mm as an ideal value for accuracy. In addition, in order to braze and join the members to be joined to a desired position, it is necessary that the joining members be closely fixed in advance by tack welding or the like. FIG. 6 shows an example in which the heat transfer fins 2 to be joined to the flat tube 1 are brazed by heating them in a furnace after fixing both ends of the sheet-shaped brazing material with temporary welding parts 7a and 7b. There is.

[0004]

In the brazing work of the heat transfer fins on the flat tube, it is difficult to maintain the above-mentioned joining surface combination accuracy because the brazing of a wide range of joining surfaces is difficult. Is significantly deteriorated (the gap in the actual brazing work is about 0.1 to 0.3 mm).

Further, as shown in FIG. 6, the brazing method for temporarily fixing the joining members by means of temporary welding for positioning is as shown in FIG. A difference in thermal expansion occurs due to mutual thermal imbalance between the heat fins 2), and both ends of the members to be joined are restrained by the tack welded portions 7a and 7b, so that a gap between the joined portions increases. The phenomenon of breakage of the brazing filler metal 3 occurs at the joint, resulting in defective brazing.

Accordingly, one object of the present invention is to propose a brazing method capable of reliably joining a wide range of joint surfaces by brazing without causing a brazing phenomenon.

Another object of the present invention is to propose a brazing method capable of surely brazing and joining while maintaining a relative positional relationship between joining members accurately.

Still another object of the present invention is to propose a brazing method capable of brazing a heat transfer fin to a flat tube with high quality.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a heat transfer fin is temporarily fixed to the surface of a sheet brazing material by a temporary fixing claw formed on the sheet brazing material, and the sheet brazing material is superposed on a pipe. The pipe and the heat transfer fin are positioned, and the sheet brazing material is melted and brazed and joined by heating in this state.

[0010]

In the sheet brazing material, the heat transfer fins are positioned relative to the pipe until they are melted, and when the melting temperature is reached, they melt and fill the space between the pipe and the heat transfer fins. Brazing and joining the spaces.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A brazing method for heat transfer fins on a flat tube, which is an embodiment of the present invention, will be described with reference to FIGS.

1 and 2 show a flat tube 1 and heat transfer fins 2.
2 shows two types of flat heat transfer tubes schematically showing a state in which they are joined by brazing 3. These flat heat transfer tubes are used in a combined state (not shown) in actual use.

In the flat heat transfer tube shown in FIG. 1, heat transfer fins 2 (2a, 2b) are provided on the outer surface of the flat tube 1 by brazing with a braze 3, and the heat transfer fins 2 are provided outside the flat tube 1. A high temperature gas 8 is caused to flow along the flow path to exchange heat with the liquid or gas 9 flowing inside the flat tube 1. The heat transfer fins 2a and 2b are fins arranged according to the amount of heat passing and having different pitch dimensions.

The flat heat transfer tube shown in FIG. 2 is provided by brazing the heat transfer fins 2 (2a, 2b) to the inner surface of the flat tube 1 with the braze 3, and the hot gas 8 passing inside the tube is used for the flat heat transfer tube. It exchanges heat with the liquid or gas 9 on the outside.

The manufacturing process of these flat heat transfer tubes is as follows.
As shown in FIG. 3, a flat sheet brazing material 4 having a thickness of 0.2 mm is used, and a predetermined position of the sheet brazing material 4 is cut and raised by press working to temporarily fix the heat transfer fin. 4a is formed. Then, as shown in FIG. 4, the heat transfer fins 2a,
2b is placed and the heat transfer fin temporary fixing claw 4a is folded by press working (hatched portion) to form the heat transfer fin 2
The a and 2b are temporarily fixed and fixed at predetermined positions on the sheet brazing material 4 and positioned.

Next, as shown in FIG. 5, the heat transfer fins 2
The sheet brazing material 4 to which a and 2b are temporarily fixed is installed on both outer surfaces of the flat tube 1 to which the heat transfer fins 2a and 2b are to be brazed (upper and lower surfaces in the figure and the lower surface side is not shown). The outer peripheral shape of the sheet brazing material 4 is made equal to the outer peripheral shape of the flat tube 1, and when the sheet brazing material 4 is installed so that the outer periphery thereof coincides with the outer periphery of the flat tube 1, the heat transfer fins 2a and 2b are The heat transfer fins 2a and 2b are temporarily fixed to the sheet brazing material 4 so that they are located at predetermined positions on the outer surface of the flat tube 1, so that the heat transfer fins 2a and 2b are fixed to the predetermined position of the flat tube 1. To position. And the heat transfer fin 2
Sheet brazing material 4 with a and 2b temporarily fixed is piled up in multiple stages in the heating furnace so as to be overlapped with both outer surfaces of the flat tube 1, and steps such as fall prevention are performed in the surroundings in the furnace. Pay. When the heat transfer fins 2a and 2b are to be brazed downward to the upper surface of the inner surface of the flat tube 1, a spacer (not shown) is inserted to support the heat transfer fins 2a and 2b so as to push them up and seat them. The material 4 may be closely attached to the upper side surface. After that, the inside of the furnace is heated to melt the sheet brazing material 4 to perform brazing in the furnace.

In the heating furnace, the sheet brazing material 4 is heated during the heating process.
The heat transfer fins 2a, 2b are positioned at predetermined positions of the flat tube 1 by the sheet brazing material 4 immediately before the melting of the sheet, and the sheet brazing material 4 is completely melted during the brazing temperature, that is, the melting and holding process. Melted into a flat tube 1 and heat transfer fins 2a, 2
It fills up between the joint surfaces of b. In this process, the heat transfer fin 2
Since a and 2b are not fixed to the flat tube 1 by tack welding or the like, they can be extended freely even if there is a difference in the amount of thermal expansion between them, thus increasing the gap between the joint surfaces. However, the close contact state with the melted brazing filler metal 3 interposed is maintained, and then the cooling process is started to complete the brazing joining.

Therefore, unlike the case where both ends of the heat transfer fin are tentatively welded to the flat tube, there is no occurrence of a joint failure such as a wax breakage phenomenon due to lifting, and a perfect brazing quality is always obtained. be able to.

The sheet brazing material 4 used for such brazing joining has thermal conductivity, spreadability and welding in joining the heat transfer fins 2a and 2b to the flat tube 1 in the flat heat transfer tube as in this embodiment. Considering the sex, 0.1
~ 0.3mm oxygen free copper (JIS C1020R
Although the sheet material of -H) is preferable, other brazing materials such as aluminum can be used depending on the application of the brazing member.

The brazing method as described above can be applied not only to brazing the heat transfer fins to the flat tube but also to joining any member that needs to be brazed uniformly over a wide area.

[0021]

As described above, according to the present invention, even when brazing between a wide range of joint surfaces, high quality brazing and joining can be performed without causing a brazing phenomenon at the time of joining. In addition, the relative positional relationship between the joining members can be easily performed by temporarily fixing the joining members to the sheet brazing material, and the assembly and setup work before the brazing work is extremely simplified, resulting in productivity and economic efficiency. It can be a brazing method rich in.

[Brief description of drawings]

FIG. 1 is a schematic view of a flat heat transfer tube in which heat transfer fins are brazed and joined to the outer surface of the flat tube according to an embodiment of the present invention.

FIG. 2 is a schematic view of a flat heat transfer tube in which heat transfer fins are brazed and joined to the inner surface of the flat tube according to another embodiment of the present invention.

3A and 3B are a plan view and a partially enlarged perspective view of a sheet brazing material on which heat transfer fin temporary fixing claws are formed.

FIG. 4 is a perspective view showing a state in which heat transfer fins are temporarily fixed on a sheet brazing material.

FIG. 5 is a perspective view showing a state in which a sheet brazing material to which heat transfer fins are temporarily fixed is installed on the outer surface of a flat tube.

FIG. 6 is a schematic view showing a defective example in which a brazing phenomenon occurs in a joint portion by conventional brazing.

[Explanation of symbols]

1 ... Flat tubes, 2, 2a, 2b ... Heat transfer fins, 3 ... Wax,
4 ... Sheet brazing material, 4a ... Heat transfer fin temporary fixing claw.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display area F28F 1/30 F28F 1/30 A

Claims (7)

[Claims] 1. A brazing method for joining fins to the surface of a pipe, wherein the fins are temporarily fixed and fixed to the surface of the sheet brazing material by means of temporary fixing claws formed on the sheet brazing material, and the sheet brazing material is superposed on the pipe. A fin brazing method, characterized in that the sheet brazing material is melted and joined by heating the tube and the heat transfer fin in a positioned state by combining them. 2. The fin brazing method according to claim 1, wherein the temporary fixing claw is formed by cutting and raising a predetermined position of a sheet brazing material. 3. The fin brazing method according to claim 1, wherein the outer peripheral shape of the sheet brazing material is equal to the outer peripheral shape of a pipe for joining fins. 4. The fin brazing method according to claim 1, wherein a member having a thickness of 0.1 mm to 0.3 mm is used as the sheet brazing material. 5. The fin brazing method according to any one of claims 1 to 4, wherein oxygen-free copper is used as the sheet brazing material. 6. A brazing method for joining fins to the surface of a flat tube, wherein the fins are temporarily fixed to the surface of the sheet brazing material by means of temporary fixing claws formed on the sheet brazing material, and the sheet brazing material is flattened. A fin brazing method, characterized in that the sheet brazing filler metal is melted by heating the flat tube and the heat transfer fin in a positioned state by superposing the flat tube and the fin on each other. 7. A brazing method, wherein the members to be joined are temporarily fixed and fixed by means of temporary fixing claws formed on a sheet brazing material for melting and brazing the members to be joined, and the members are heated and brazed. Brazing method.