JPS5950934A - Manufacture of heat exchanging tube - Google Patents

Abstract

PURPOSE:To reduce the pressing force of a fin, and to prevent poor welding, by forming the welding edge of a fin into an arc-shape havin a radius of curvature which is approximate but not coincident to and with the outer peripheral radius of a tube material, and welding the fin edge to the tube while bringing the fin edge into press contact with the tube. CONSTITUTION:A shape of each fin 1, 1 is rectangular equilateral triangle having an arc-shaped welding edge 2 at the central part of its oblique side, and the arc-shaped welding edge 2 has a radius R' of curvature slightly larger than the outer peripheral radius R of a tube material 3. Further, cut off parts 4 are formed in the fin 1 by cutting off both of the end corner parts of the edge 2, respectively. The edges 2, 2 and a part of the tube 3 which is in contact with the edges 2, 2 are melted while bringing the edges 2, 2 into press contact with the tube 3 in state of sandwiching the tube 3 between both of the fins 1, 1, to deform the edges 2, 2 along the outer peripery of the tube 3, thereby welding the fins 1, 1 to the tube 3 by leaving a space between both of the oblique sides of the fins 1, 1.

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a heat exchange tube.

Conventionally, this type of method involves manufacturing a large number of fins with arcuate weld edges having a radius of curvature that matches the outer radius of the pipe material.
Take out a set of fins from among these, sandwich the pipe material with these fins, and press the welding edge tightly against the pipe material.
There is a method for manufacturing heat exchange tubes by melting the welded edge and the part of the pipe material that it presses with a resistance welder, etc., welding the fins to the pipe material, and repeating the above steps to attach the fins in the longitudinal direction of the pipe material. Are known. However, the conventional method has the following drawbacks. First, since the entire surface of the welded edge of the fin is shaped to be in close contact with the pipe material before welding, in other words, the contact area between the welded edge and the pipe material is large, so it is necessary to increase the pressure to press the fin against the pipe material. There was a drawback that the pressure per unit area was small, resulting in areas with poor welding. Second, when welding using a resistance welding machine, the contact area between the weld edge and the pipe material is large, so a large current is required to weld them together, which is uneconomical and generates a large current. The drawback is that it requires an expensive welding machine. Third
In addition, since the contact area between the weld edge and pipework remains constant from the start of welding to the completion of welding, excessive welding often occurs in some areas, resulting in welding distortion. The disadvantage is that it often occurs.

In this invention, the welded edge of the fin is made into an arc shape with a radius of curvature that approximates but does not match the outer radius of the pipe material,
To provide a method for manufacturing a heat exchange tube that eliminates the above drawbacks by melting the welded edge while pressurizing it to the tube material, deforming the welded edge into a shape that follows the outer peripheral surface of the tube material, and welding the fins to the tube material. It is something to do.

A first embodiment of the present invention will now be described with reference to FIGS. 1 to 3.

A large number of fins 1 are manufactured by punching or other means from a plate material that can be resistance welded, such as general steel or special steel such as stainless steel or corrosion-resistant steel. The shape of each fin 1 is a right-angled isosceles triangle having an arcuate welded edge 2 at the center of the hypotenuse,
The welding edge 2 has an arcuate shape with a radius of curvature R' that is slightly larger than the outer radius R of the tube material 3. Further, a cutout portion 4 is formed in the fin 1 by cutting off both end corner portions of the welding rib 2.

Note that the shape of the fin 1 is not limited to a right-angled isosceles triangle.

A set of fins 1.1 are taken out of the fins 1 manufactured in this manner, and the welded edges 2.2 of the fins 1.1 are pressed against the pipe material 3, with the pipe material 3 being sandwiched between these fins 1.1. At the same time, using a resistance welding machine or the like, the welded edge 2.2 and the portion of the pipe material 3 that they contact are melted, and the welded edge 2.2 is melted.
2 is deformed into a shape that follows the outer peripheral surface of the tube material 3, and the fin 1 is
．． Fins 1.
1 to the pipe material 3. Incidentally, it goes without saying that the means for melting the welding edge 2.2 and the portion of the tube material 3 with which they abut may be a swamp welding machine or the like.

By forming the cutout portion 4, the corner formed by the welding edge 2 and the oblique side of the fin 1, that is, the portion where excessive welding is likely to occur, is removed in advance, so that excessive welding and the resulting welding distortion are less likely to occur. You can.

By repeating the above operations, the fins 1.1 are attached at predetermined intervals along the length of the tube 3.

Note that the fins 1 are arranged at predetermined intervals along the longitudinal direction of the pipe material 3.
Of course, a plurality of fins 1 may be welded to the tube material 3 at the same time.

The heat exchange tube 6 manufactured in this manner is used in a state where high temperature fluid such as exhaust gas flows at an angle of 45° to the oblique side of the fin. By doing so, the flow of thermal fluid such as exhaust gas can be disturbed in the interval 5 between the oblique sides of the fins 1.1, and the heat exchange efficiency can be increased.

A second embodiment will be described based on FIG. At the center of the oblique side of the fin 1, a welded edge 2 having a radius of curvature R// which is slightly smaller than the outer circumferential radius R of the tube material 3 is formed.

The rest is the same as the first embodiment, so the explanation thereof will be omitted.

As is clear from the first and second embodiments, the welding edge 2 only needs to have a circular arc shape with a radius of curvature that approximates but does not match the outer radius R of the tube material 3. Welded edge 2
The radius of curvature can be freely set based on the material, amount of penetration, etc.

As described above, according to the method of the present invention, the welded edge of the fin is formed into an arc shape with a radius of curvature that approximates but does not match the outer radius of the pipe material, and the welded edge is melted while being pressed against the pipe material. The fins are welded to the tube material by deforming the fins into a shape that follows the outer peripheral surface of the tube material, that is,
The force that presses the fin is made by reducing the contact area between the welding edge and the pipe material at the start of welding, and while welding progresses, the parts of the welding edge that have not been melted and have not been undone come into contact with the pipe material one after another. Even if the welding area is small, the pressure per unit area that acts on the part to be welded can be increased, so welding defects can be prevented. Also,
When welding using a resistance welder, at the start of welding, the contact area between the weld edge and the pipe material is reduced and a large current can be passed through that area, making it easier to weld the initial contact area. During this process, the following part is preheated, and the preheated part is welded following the already welded part, so unlike the conventional method, it does not require a large current, and the resistance welding machine used in the conventional method An inexpensive resistance welding machine that can generate only a small current can be used. Furthermore, since welding is not performed all at once, but is performed sequentially while deforming the welding edge, excessive welding and welding distortion caused by it can be reduced.

[Brief explanation of the drawing]

The drawings are for explaining the present invention in detail. Fig. 1 is a longitudinal cross-sectional view showing the state before the fan 1' is welded to the pipe material in the first embodiment, and Fig. 2 is a longitudinal sectional view showing the finished product. FIG. 3 is a longitudinal cross-sectional view of the exchange tube, FIG. 3 is a side view of the main part of the heat exchange tube partially crushed, and FIG. 4 is a longitudinal cross-sectional view showing the state before the fins are welded to the tube material in the second embodiment. 1...Fin, 2...Welded edge, 3...Pipe material, 6...
Heat exchange tube, patent applicant Nishida Tekko Co., Ltd., patent attorney

Claims (1)

[Claims] 1. The welded edge (2) of the fin (1) is made into an arc with a radius of curvature that approximates but does not match the outer circumferential radius of the tube (3), and this welded edge (2) is attached to the tube (3). A heat exchange method characterized by welding the fin (1) to the tube material (2) by melting the fin (1) while pressurizing the tube material (3) and deforming the weld edge (2) into a shape that follows the outer peripheral surface of the tube material (3). Method of manufacturing tubes. 2. Claim 1, wherein the cutout portion (4) is formed by cutting off both terminal corner portions of the welded edge (2) of the fin (+), respectively.
2. Method for manufacturing heat exchange tubes as described in Section 1. 3. The fin (1) has a right-angled isosceles triangular shape, and the welded edge (2) is formed on the hypotenuse of the fin (1).
2. Method for manufacturing heat exchange tubes as described in Section 1.