JPH0191992A - Method for brazing heat exchanger made of aluminum - Google Patents

Abstract

PURPOSE:To stabilize quality when a fin material clad with an Al (alloy) or Al-Si brazing filler metal is brazed, by holding the fin material in a specified temp. range for a prescribed time during heating before the brazing. CONSTITUTION:A fin material made of a brazing sheet clad with an Al (alloy) or Al-Si brazing filler metal is formed into fins 4 and the fins 4 are brazed to a tube 5. At this time, the fins 4 are held at a constant temp. within the temp. range of 300-450 deg.C for >=1 min during heating before brazing. By this method, the quality of a product is improved.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to a method for brazing aluminum heat exchangers, and in particular, it is necessary to prevent buckling (sag) of the fin material during brazing. .

(Prior art) Automotive aluminum heat exchangers include radiators,
There are air conditioner condensers, evaporators, etc., which consist of a tube that forms a refrigerant passage and fins that perform efficient heat exchange between the refrigerant and the air, and are usually manufactured using the brazing method. For example, in a radiator, as shown in Fig. 3, a corrugated fin (4) not clad with brazing material is assembled to an electric resistance welded tube (5) whose outside is clad with brazing material.
They are joined together by brazing. The thickness of the fin is o
, around im. In the figure, (6) is the header, (
7) indicates a tank.

In addition, as shown in Figure 4, the capacitor is constructed by assembling fins (8) made by corrugating a brazing sheet clad with brazing filler metal between extruded flat tubes (9) bent in a serpentine shape, and joining them by brazing. ing. Fin thickness is 0
．． 1-0.2Ml11. The cladding ratio of the filler metal is 1 on one side.
Around 0% is used.

Fin core made of bare fin material without cladding with brazing material or brazing sheet with cladding of brazing material (Δ is JIS 1100, etc., Hotun A1, JIS 3003, 3
A1-Mn alloys such as 203, alloys to which ln, (n, 3n, etc. are added to have a sacrificial effect), JIS
AJ-M9 series alloys such as 5005 and He1-tVtg-8i series alloys such as JIS 6951 are used, and are hard +
'A (HlX, H2X>) is mainly used. Brazing is performed by heating to the melting temperature 1i (590 to 610°C) of the A1-5; or Al-8i - Mg brazing filler metal, A1-Si-based brazing filler metal is used for flux brazing (using chloride-based flux or non-corrosive fluoride-based flux), and AJ-Si-M is used for vacuum brazing.
G-based brazing filler metal is used to heat the heat exchanger parts, and heating is performed at a relatively low temperature up to the melting point of the brazing filler metal.
The temperature will rise in time.

Flux brazing uses a continuous furnace to complete brazing in about 20 to 30 minutes, and the change in actual temperature is
As shown in Fig. 5, the stomach was heated continuously by charging the
After being held at 0 to 610°C for 5 minutes, it was cooled and taken out from the furnace. For vacuum brazing, a semi-continuous furnace with 3 to 5 chambers is used, and the vacuum level is maintained at 10-5 Torr.
Brazing is completed in about 60 minutes, and a temperature raising process similar to flux brazing is used. That is, 2-b: Heating is not performed and the temperature is not maintained at a constant temperature during the heating process.

(Problem to be solved by the invention) In recent years, in order to reduce the weight of aluminum heat exchangers, the aluminum members have become thinner, and the fin material has become extremely thin, with a thickness of around 0.1 m. During brazing heating at 610° C., deformation occurs due to the clamping force of the jig or the load of other aluminum members, causing problems such as poor brazing of the core and dimensional changes.

In order to reduce the force applied to the fins, the condenser core is brazed in a horizontal position to prevent the load of the extruded tube and jig from being applied. In order to improve the forming ability and prevent the fins from slipping (falling off), it is necessary to apply a certain amount of pressure to the fins through other members, making it extremely difficult to reduce the thickness of the fins.

(Means for Solving the Problems) In view of this, the present invention has been developed as a result of various studies, and by devising the brazing IJu heat process, deformation of the fins in the high temperature range during brazing is prevented, thereby preventing the fins from deforming in the high temperature range. We have developed a brazing method for aluminum heat exchangers that allows for thinner aluminum heat exchangers.

That is, the mounting method of the present invention is applicable to fin materials made of aluminum or aluminum alloy, Af-8i series, A1-5i
- In a method of heating and brazing by assembling the fins to the pipe body forming the refrigerant passage of an aluminum heat exchanger using a fin material consisting of a brazing sheet clad with VG brazing filler metal, when the heating temperature is increased during brazing, 300-450
It is characterized by heat brazing that is held at a constant temperature within the temperature range of °C for 1 minute or more.

(Function) As a result of examining the deformation (sag) and marocrystalline pattern during brazing, it was found that the fins were
It has been found that by incorporating a step of holding at a constant temperature within the temperature range of 50° C. for 1 minute or more, it is possible to extremely reduce the fin hanger in the high temperature range (at the melting humidity of the filler material).

When hard fin materials are brazed and heated, recrystallization usually ends at the softening humidity of the fins (300 to 450°C), and the fins soften. If the fin rig is made of bare material, it will begin to sag as it softens, and especially if it is exposed to high temperatures exceeding 50 ()°C, the high temperature strength of aluminum is only a few kgf/mtA, so (if it becomes large at both ends) There is.

On the other hand, Brazing Sea is clad with brazing wood! In the case of fin materials consisting of ・, as the brazing filler metal melts, Sit dispersion to the core material progresses, the degree of erosion of the core material varies depending on the size of the grain, and the amount of sag changes depending on the thickness of the remaining core.

Although there are many unknowns about the effects of heating conditions and sag fluctuations during heating, Si precipitation and recrystallization compete with each other by holding the temperature at a constant temperature within the softening temperature (300 to 450°C) for more than 1 minute. It promotes this phenomenon, causes coarsening of crystal grain size, and further improves heat resistance strength.

However, holding at temperatures below 300°C or above 450°C makes it impossible to cause competitive phenomena;
If the heat exchanger core is held for less than 10 minutes, it is not possible to uniformly improve the heat resistance strength of each fin portion of the heat exchanger core.

〔Example〕

JIS 3003 (A 1-0.15% CLJ-1%
An alloy consisting of Mn) + 1.5% Zn + 0.15% Zr was produced, soaked at 520°C for 3[li], and then hot rolled and cold rolled to a thickness of 0.14%.
This plate was intermediately annealed at 400° C. for 2 hours, and then cold-rolled to produce a T114 tempered fin material with a thickness of O11#.

A sample with a length of 70 m and a width of 20 m in the rolling direction was cut out from this fin material, and a sag test jig (1) shown in Fig. 1 was cut out.
Attach the fin material (2) so that it protrudes by approximately 50m,
It was charged into a brazing furnace and the amount of nug during brazing heating was measured. In the top view, (3) shows a scale for measuring the amount of sag. Brazing heating was performed in a vacuum, and the temperature increase rate was set to match the heating pattern shown in Figure 5. The sag behavior of the fin material during brazing heating was observed from outside the furnace, and the fin material was attached to a nag test jig. The sag ω was read on the scale. The results are shown in Table 1 in comparison with the conventional method in which the temperature is raised continuously.

As is clear from Table 1, 300% during heating during brazing heating.
Mounting method No. of the present invention held at ~450°C for 1 minute or more
, 1 to 6 are all conventional method Nos. in which the temperature was raised continuously,
It can be seen that the amount of sag is smaller compared to 9.

On the other hand, in comparison method No. 7 and 8, in which the temperature was kept constant at 280°C and 470°C during heating, the sag amount was N in the conventional method.
It can be seen that the value increases from 0.9.

Further, FIG. 2 shows the change in the amount of sag during the temperature increase process of the present invention methods No. 4, in which the temperature was maintained at 350° C. for 10 minutes, and the conventional method Nα9, in which the temperature was continuously increased.

In the figure, Nα4 indicates the change in sag amount when brazing and heating is performed by the method of the present invention, and Nα9 indicates the change in sag amount in the conventional method in which the temperature is continuously increased. The amount of sag increases at 600°C. On the other hand, in the case of the method of the present invention, sag progresses slightly by holding at 350°C for 10 minutes, but after that, the sag progresses slightly.
It can be seen that the Nag unit when heated to 00°C is extremely small.

It should be noted that the larger the grain size of the fin material, the greater the effect of maintaining the temperature at 300 to 450° C. during the heating process, and a similar tendency was observed in the fin material made of a brazing sheet clad with a brazing material.

Furthermore, as fin materials, IXXX series, 3XXX series, and 5XXX
A similar tendency was observed for the 6XXX series.

[Effects of the invention] - As described above, according to the brazing method of the present invention, the heating time is not much different from that of the conventional brazing method, and the amount of sag in the fins can be suppressed to a small level, making it possible to reduce the amount of sag in the aluminum heat exchanger. It is possible to perform brazing reliably, there is little variation in core dimensions, and it has industrially significant effects such as making it possible to make the fins thinner and the core lighter.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a sag test jig, Fig. 2 is an actual measurement value showing the relationship between temperature and sag m, Fig. 3 is a perspective view showing an example of a radiator, and Fig. 4 is an example of a condenser. The perspective view and FIG. 5 are explanatory diagrams showing changes in actual temperature during flux brazing. 1. Sag test jig 2, fin material 3, scale 4, fin 5, electric resistance welded tube 6, header 7, tank 8, fin 9, extruded flat tube Figure 1 Opening Figure 2 i11+'c+ Figure 3 A% PJI (min)

Claims (1)

[Claims] Fin material made of aluminum or aluminum alloy or Al-Si
Brazing is a method in which the fins are assembled and heat-brazed to the pipe body forming the refrigerant passage of an aluminum heat exchanger using a fin material consisting of a brazing sheet clad with an Al-Si-Mg brazing material. 1. A method for brazing an aluminum heat exchanger, the method comprising heating and brazing after holding the temperature at a constant temperature within a temperature range of 300 to 450° C. for 1 minute or more during heating.