JPS5915742B2 - Method for manufacturing laminate for heat exchanger - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new method of manufacturing a heat exchanger part by brazing, which is made by laminating a large number of perforated plates made of thin metal plates such as aluminum.

The perforated plate has a shape as shown in FIGS. 1 and 2, for example. That is, FIG. 1 is a plan view, and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 5 It is made of thin plate. This perforated plate 1 has a large number of pores 2 that serve as fluid passages, and is also provided with press-formed annular and radial recesses 3. A stacked body 6' is produced by stacking ten such perforated plates as shown in FIG. 3 and joining each perforated plate at the recessed portion.

This is incorporated into a heat exchanger to perform heat exchange between the fluid flowing through the pipe inserted into the central opening 5 and the fluid flowing through the pores of the perforated plate. 15 Conventionally, such a laminate has been manufactured by bonding the recessed portions of perforated plates with an adhesive 4' such as epoxy resin (see, for example, Japanese Patent Publication No. 49-8355).

However, the above adhesive does not have sufficient heat resistance at the joint, and also has the problem of flatness, which will be described later, and does not necessarily have good heat exchange performance. Instead of using the above adhesive, a method of joining the perforated plates by brazing has been considered, but in the normal brazing method using flux, the holes are clogged by the flux and the heat exchange degrade performance.

Furthermore, since the perforated plate itself is extremely thin and has undergone various processing, it is not necessarily a perfectly flat body.

Therefore, when a large number of these are stacked 30 on top of each other, there are parts that do not adhere tightly to the joints, and the fluid that is to be flowed is disturbed by being separated by the recessed parts, which impedes heat exchange. This invention utilizes a vacuum brazing method to eliminate the drawbacks of conventional manufacturing methods, and in particular, flattens the perforated plate 35 and improves the adhesion of the joint (hereinafter collectively referred to as flatness). The purpose is to

The method for producing a laminate of the present invention is to fasten a laminate in which a large number of perforated plates are stacked together with a fixture having a thermal expansion smaller than the total thermal expansion of the laminate, and to properly secure the laminate prior to vacuum brazing. It is characterized in that it is heated and a compressive force is applied to the laminate by the stress generated by the difference in thermal expansion.

The above heating is performed at a temperature that is higher than the recrystallization temperature of the perforated metal plate and lower than the liquid phase formation temperature of the brazing material.

FIG. 4 is an example showing the state in which the laminate is tightened by the fixture when carrying out the method of the present invention described above. That is, the fixture, generally indicated by 7, in this case consists of upper and lower presser plates 8, through bolts 9, and nuts 10. The through hole of the holding plate is a so-called blind hole with a diameter larger than the outer diameter of the bolt so that the bolt 9 can pass through it loosely. Between the holding plates of this fixture 7, there is a laminated body 6 consisting of a brazing material coated thin plate 4 having approximately the same shape as the recessed part fitted into the recessed part 3 of the perforated plate 1 as shown in FIG. scissors,
Tighten the nut to secure.

If the whole is heated in this state, both the laminate 6 and the fixture 7 will thermally expand, but the material and structure are selected so that the amount of expansion of the fixture is smaller than that of the laminate. Therefore, when the laminate 6 is heated to the above-mentioned temperature range, compressive force is applied to the laminate 6 in the vertical direction due to the difference in the amount of expansion. Since each perforated plate of the laminate is heated to a temperature higher than its recrystallization temperature and softened, each perforated plate is flattened by this compressive force, and the brazed portion (the brazing material coated thin plate 4 is removed). The adhesion of the sandwich (concavity) becomes complete. That is, the flatness is improved. In this case, if the heating temperature is lower than the recrystallization temperature, the amount of softening and expansion of the perforated plate will be small, and the improvement in flatness will not be sufficient.

On the other hand, if the temperature is high enough to generate the liquid phase of the brazing filler metal,
The concave portion sandwiching the brazing filler metal coating thin plate will shrink, and the adhesion of that portion will deteriorate. Figure 5 shows an aluminum rod (10wmφ x 80mt) and a stainless steel (SUS2)
7) Rod (10wrLφ×80wmt) and ordinary steel (1
0Tmφ×80wmt) is a graph showing the difference in thermal expansion.

As can be seen from the figure, the bolts 9 of the fixing device are preferably made of ordinary steel because the difference in thermal expansion is larger in the steel. As mentioned above, a laminate with improved flatness,
Vacuum brazing is performed using the brazing material of the brazing material coated thin plate 4 in a vacuum furnace while the fixing device is being tightened. Since the joints are completely adhered, the joint after brazing is also perfect, and each section of the perforated plate is completely isolated. In addition, vacuum brazing
Since it does not require the use of flux, there is no need to worry about clogging of the holes due to residual flux. During vacuum brazing, the brazing material of the brazing material coating thin plate 4 is of course melted, so that the compressive stress on the laminate produced during the heating is released.

If the bolt holes of the retainer plate 8 of the fixture 7 are made blank holes as described above, the load of the retainer plate 8 itself will be applied during brazing. However, even during brazing, considerable compressive force is applied to further improve the adhesion of the joint. , it is desirable to apply a load to the laminate. As a means for this, for example, as shown in FIG. 4, various modes can be considered, such as placing a weight 11 on the holding plate 8, or using a spring or the like. Table 1 shows that by changing the material and load of the fixing bolt,
This figure shows the results of an experiment in which a laminate was brazed.

Note that the laminate is 70Ttm(!)XO. l6~0.2
It consists of 120 perforated aluminum plates with a thickness of 5wn, and the thickness of the brazing metal coated thin plate is 2.75WtHL. Vacuum brazing was carried out at a temperature of 600° C. and a degree of vacuum of 10 −4 rwLHg.

As is clear from the above experimental results, if the fixing bolt is made of ordinary steel, which has a large difference in thermal expansion from aluminum, good results can be obtained even with a small additional load, but if it is made of SUS27, a large load can be obtained. I need.

The laminate produced by the laminate production method of this invention is:
The joints are brazed and have high heat resistance, and the flatness is improved and the joint is perfect.
It has high heat exchange efficiency and can be incorporated into heat exchangers for all kinds of uses to demonstrate excellent performance.

[Brief explanation of drawings]

Fig. 1 is a plan view showing an example of a perforated metal plate, Fig. 2 is a sectional view taken along line A-A thereof, Fig. 3 is a sectional view showing a laminate of perforated metal plates, and Fig. 4 is a fixing device for the laminate. FIG. 5 is a partial sectional view showing the state in which the rod is tightened, and FIG. 5 is a graph showing the difference in thermal expansion between the aluminum rod and the steel rod. 1... Perforated metal plate, 2... Pore, 3... Recess, 4
DESCRIPTION OF SYMBOLS 1... Adhesive, 4... Brazing metal coating thin plate, 5... Opening, 6, 6/... Laminated body, 7... Fixture, 8...
Holding plate, 9...Through bolt, 10...Nut, 11
...A weight.

Claims (1)

[Claims] 1. When producing a heat exchanger laminate by vacuum brazing a large number of perforated metal plates separated by annular and radial recesses with brazing material coated thin plates fitted into the recesses, the vacuum Prior to brazing, the laminate before brazing is tightened with a fixture having a thermal expansion smaller than that of the laminate, and then heated to a temperature equal to or higher than the recrystallization temperature of the perforated metal plate. , flattening the perforated metal plate and flattening the perforated metal plate by heating to a temperature below the liquid phase formation temperature of the brazing filler metal, and utilizing the difference in thermal expansion between the perforated metal plate and the fixture caused by this heating. A method for producing a laminate for a heat exchanger, the method comprising improving the adhesion between the concave portion of the plate and the brazing material coated thin plate.