JPH03138080A - Manufacture of tube with plate fin - Google Patents

Abstract

PURPOSE:To manufacture a tube with a plate fin excellent in strength and heat transmission performance by applying flux on a gap between a fin collar and the tube. CONSTITUTION:The plate fin 2 is provided with the cylindrical fin collar 4 having an insertion hole 3 and its peripheral inclined tapered part 5. The tube having the outside diameter Dp smaller than the maximum inside diameter D1 of the fin collar 4 and larger than the minimum inside diameter D2 thereof is press-fitted into the fin collar 4. Afterward, the flux is applied on the gap between the fin collar 4 and the pipe at least and the pipe and the plate fin 2 are brazed by brazing filler metal 2b. By this method, assembly operation can be facilitated and workability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for manufacturing a pipe with plate fins, particularly a pipe with plate fins used as a component of a heat exchanger for a water heater, a heat exchanger for a heat absorption can of a bathtub, etc. Relating to a manufacturing method.

In this specification, the term aluminum is used to include its alloys.

BACKGROUND ART For example, the heat exchanger for a water heater described above has a plate fin structure in which a plurality of plate fins each having a pipe insertion hole are sheathed and joined in parallel in the length direction of a water pipe through the insertion hole. A pipe is used as the main component.

The heat applied to the surface of the fins by the combustion gas is then transferred to the circulating water in the pipe to heat it. Therefore, in order to increase the efficiency of the heat exchanger, it is essential that the heat transfer from the plate fins to the pipes be performed well, and for this purpose, the plate fins and the pipes should be placed as closely as possible and have a contact area. It must be joined with a larger size. Therefore, a cylindrical fin collar is provided upright on the periphery of the pipe insertion hole of the plate fin, and the plate fin and the pipe are joined via this fin collar (for example, in 1983- 7083
No., Utility Model Publication No. 58-7084).

Problem to be Solved by the Invention However, in the conventional pipe with plate fins as described above, the plate fins and the pipe are joined by a machine that passes the plate fins through the pipe and covers it, and then expands the pipe. Since the fins and the pipes were joined together by mechanical bonding, the joint between the fins and the pipes tended to loosen over time, which resulted in a reduction in heat conductivity. Various measures have been taken to improve the adhesion between the fins and the pipe, but these measures have not been sufficient.

This invention was made in view of the above circumstances, and
The purpose of the present invention is to manufacture and provide a pipe with plate fins that can ensure sufficient adhesion between the plate fins and the pipe over a long period of time.

Means for Solving the Problems To achieve the above object, the present invention has a pipe insertion hole and a cylindrical fin collar around the periphery of the insertion hole, and the fin collar is provided with a tapered portion that slopes in the length direction. After press-fitting a pipe having an outer diameter smaller than the maximum inner diameter and larger than the minimum inner diameter of the fin collar into the fin collar of the plate fin using a plate fin, at least the gap between the fin collar and the pipe is press-fitted. The gist of this invention is a method for manufacturing a pipe with plate fins, which is characterized by applying flux or at least pre-applying flux to the inner surface of the fin collar, press-fitting the pipe, and then brazing the pipe and plate fins. .

The pipe is inserted into the working fin collar from the maximum inner diameter side of the fin collar. The pipe is guided smoothly along the tapered part of the fin collar.

Furthermore, since the pipe and plate fin are joined by brazing, reliable and strong adhesion between the two is ensured over a long period of time.

Embodiment Next, the structure of the present invention will be explained by taking as an example a method of manufacturing a plate-finned pipe used in a heat exchanger for a water heater.

Figures 1 to 3 show heat exchangers for water heaters,
In this heat exchanger, the U-shaped plate fin pipe (A)
and an L-shaped plate-finned pipe (B) are used.

First, in order to manufacture the plate fin-equipped pipes (A) and (B), a U-shaped pipe (1a) and an L-shaped pipe (1b) with circular cross sections and a plate fin (2) are prepared. Each pipe (la) (lb) is made of stainless steel. As shown in FIGS. 4 and 5, the plate fin (2) is made of a single-sided aluminum plating sheet with a core material (2a) coated with an Al2-5t alloy brazing filler metal (2b) on one side, and its width Pipe (1
) are provided in parallel with three tube insertion holes (3) each having an inner diameter (Dl) larger than the outer diameter (Dp) of the tube, and a cylindrical fin collar (4) is installed on the periphery of each insertion hole. )
It is erected by burring, etc., with the inner surface facing the brazing metal layer side. In addition, the wall surface of the fin collar (4) is formed into a tapered part (5) whose inner diameter is continuously reduced toward the tip, and the inner diameter (D2) of the tip is formed into a pipe (la) (lb). It is set smaller than the outer diameter (Dp) of. Further, a flange portion (6) is formed at the tip of the fin collar (4).

Next, as shown in Fig. 5, insert the dowel-shaped pipe (1b) from the proximal end of the fin collar (4) into the central pipe insertion hole (3) of the plate fin (2), and The U-shaped pipe (l) is inserted from the base end side of the fin collar (4) into the pipe insertion holes (3) (3) on both sides of (2).
Insert both ends of a). Hole diameter of pipe insertion hole (3) (D
Since l) is set larger than the outer diameter (Dp) of pipes (la) and (lb), it may be necessary to reduce the diameter of the tips of pipes (la) and (1b) (even though the pipes are easily finned). Introduced into the collar (4) and the fin collar (4)
It is smoothly guided by the tapered part (5) of the fin collar (4) and is press-fitted beyond the inner diameter (D2) of the tip of the fin collar (4).

In this way, a plurality of plate fins (2) are connected to the pipe (1a).
(1b), and the pipe (la) is inserted in such a manner that the outer surface of the pipe is continuously covered with those fin collars (4).
(lb) is exteriorized parallel to the length direction to form a plate-finned pipe assembly.

Next, wax flux is applied to the inner surface of the fin collar (4) of the plate fin (2). In this example, since the pipes (la) (lb) are made of stainless steel and the plate fin (2) is made of aluminum, the flux is a flux suitable for brazing stainless steel and aluminum, such as tin fluoride 0605. A fluoride flux containing ~0.15 wt% may be used. Here, as a fluoride flux, KAfiF
4 and KF 80-99.8wt%: 20-0.2vt%
Examples include a mixture of AgF2 and KF, a mixture of fluoroaluminium complex salts (K3AgF2 and KAρF4), and a mixture of AgF2 and KF. During application, the above-mentioned flux containing tin fluoride is generally used by suspending it in the form of a slurry in a liquid such as water.

Spraying or brushing can be used as a coating method, and a dipping method can also be used as a uniform coating method suitable for mass production. When using this immersion method, it is sufficient to immerse the entire finned pipe assembly in the suspension, and the flux flows through the small gap between the adjacent plate fins into the gap between the fin collar (4) and the pipe (1a) (lb). flux adheres to the inner surface of the fin collar.

The assembly of the plate-finned pipe with flux applied to the inner surface of the fin collar (4) is then dried and heated in an atmosphere of inert gas or the like to a temperature lower than the melting point of the brazing filler metal and higher than the melting point of the flux. By heating to about 600 to 610°C, the brazing material on the inner surface of the fin collar (4) is melted and the pipe (la) (lb) and plate fin (2) are brazed and joined to form a pipe with plate fins. . By this brazing, as shown in FIG. 6, the gap between the inner surface of the fin collar (4) and the pipes (la) (lb) is filled with the brazing material (2b), and the two are tightly joined without any gaps.

In the above explanation, flux application is performed using plate fins (2
) After inserting the pipes (la) and (lb), the flux application does not necessarily have to be done in this order; flux must be applied to at least the inner surface of the fin collar (4) before the pipe is inserted. After drying, the pipe (la) (lb) may be inserted. By doing so, it is possible to more reliably apply flux to the inner surface of the fin collar (4), and to prevent flux from adhering to the pipe as much as possible. Incidentally, the flux may be applied to the inner surface of the fin collar (4) by immersing the entire fin collar (4) in the suspension.

After joining the pipe and the plate fin, as shown in FIGS. 1 to 3, a U-shaped connecting portion (7 ) are connected by brazing, and an L-shaped water supply part (8) is also connected to the other end opening of the U-shaped pipe (1a) by brazing to obtain the water heater heat exchanger shown in the figure.

In the water heater heat exchanger shown in the figure, water flowing from the water inlet (9) flows along the pipes (la) and (lb), but during this time, the combustion gas applied to the part where the plate fins (2) are present It is heated, becomes hot water, and enters the hot water inlet (1
0).

FIG. 7 shows another embodiment of the invention. In this example, the pipe (lc) is connected to the plate fin (2').
The tapered part (5') of the fin collar (4') is provided only over a part of the length in the protruding direction from the base end of the fin collar.

In addition, the inner diameter (D1') of the base end of the fin collar (4') is set larger than the outer diameter (Dp') of the pipe (1c), while the inner diameter (D2') of the cylindrical tip is set larger than the outer diameter (Dp') of the pipe (1c). 1c)
is set smaller than the outer diameter of the In this embodiment, the flux is applied in advance to at least 4 fin collars.
’) and let it dry, then apply the fin color (
The pipe (1c) is press-fitted into the pipe (1c) from the base end side of the pipe (4'), and the plate fin (2') is placed on the outside in parallel to the pipe. Thereafter, the plate fin (2') is heated to melt the brazing material on one side of the plate fin (2'), and the pipe (1c) and the plate fin (2') are brazed together. In this case, since both the pipe (lc) and the plate fin (2') are made of aluminum, it is sufficient to use a fluoride-based flux that does not contain tin fluoride. (KAflF4 and KF 80-9
9.8 wt%: Mixed at a ratio of 20 to 0.2 wt%, fluoroaluminum complex salt (K3 AgF2
and KAρF4), and mixtures of AgF2 and KF.

Effects of the Invention In accordance with the above, this invention first connects the plate fin and the pipe by brazing instead of mechanical joining, so they can be integrated firmly and without any gaps, and they can be easily integrated over time. There is no risk that the connection between the plate fin and the pipe will loosen. Therefore, it is possible to ensure good adhesion between the fins and the pipe over a long period of time, and it is possible to obtain a pipe with plate fins that not only has excellent strength but also extremely excellent heat transfer performance. Moreover, in the case of mechanical joining, dimensional accuracy is required for the outer diameter of the pipe, the inner diameter of the fin collar, etc., whereas in the present invention, even if there is an uneven gap between the fin collar and the pipe, the gap Dimensional accuracy can be reduced because the brazing filler metal is filled to ensure bonding. In addition, by providing a tapered part on the fin collar, the outer diameter of the pipe can be set smaller than the maximum inner diameter of the fin collar and larger than the minimum inner diameter.
Since the pipe is press-fitted into the fin collar, by inserting the pipe from the maximum inner diameter side, the pipe can be easily introduced into the fin collar without having to perform diameter reduction processing on the tip of the pipe. Movement can be prevented, and therefore the assembly work can be facilitated and work efficiency can be improved.

[Brief explanation of the drawing]

Fig. 1 is a front view of a water heater heat exchanger using a pipe with plate fins manufactured according to the present invention, Fig. 2 is a bottom view, Fig. 3 is a side view, and Fig. 4 is a front view of the plate fins. Fig. 5 is a sectional view taken along the line ■-V in Fig. 4, Fig. 6 is a sectional view showing the state of connection between the plate fin and the pipe, and Fig. 7
The figure is a sectional view of a plate fin showing another embodiment. (A) (B)... Pipe with plate fins, (l
a) (lb)...pipe, (2)...plate fin, (3)...insertion hole, (4)...fin collar (5)...tapered part. that's all

Claims (2)

[Claims] (1) A plate fin is used that has a pipe insertion hole and a cylindrical fin collar around the periphery of the insertion hole, and the fin collar is provided with a tapered portion that slopes in the length direction, and the fin of the plate fin is After press-fitting a pipe having an outer diameter smaller than the maximum inner diameter and larger than the minimum inner diameter of the fin collar into the collar, flux is applied at least to the gap between the fin collar and the pipe, and then the pipe and plate fin are soldered. A method for manufacturing a pipe with plate fins. (2) A plate fin is used that has a pipe insertion hole and a cylindrical fin collar around the periphery of the insertion hole, and the fin collar has a tapered portion that slopes in the length direction, and at least After applying flux to the inner surface of the fin collar, a pipe having an outer diameter smaller than the maximum inner diameter of the fin collar and larger than the minimum inner diameter is press-fitted into the fin collar, and then the pipe and the plate fin are brazed. A manufacturing method for pipes with plate fins.