JPS62161465A - Heat exchanger - Google Patents

Abstract

PURPOSE:To eliminate the deformation and permanent set in fatigue of materials, the deformation of fins by wind pressure, etc. and to obtain a highly corrosion resistant heat exchanger by specifying the material and brazing filler metal of the fins of the heat exchanger which is brazed with flat extruded and perforated pipes made of an Al material and the fins. CONSTITUTION:The Al alloy fin 1 contg., by weight, about 0.3-6.5% Zn and about 0.1-2.2% Mg is prepd. The flat extruded and perforated pipes 2 which are made of Al or A alloy and are provided with a Zn plating film on the surface are prepd. The fins 1 and the pipe 2 are combined as shown in the figure and a mixed flux suspension composed of ZnCl2, Zn powder, additive to accelerate reactive soldering and org. solvent is filled between the films 1 and the pipe 2, then reactive soldering is effected at about 420 deg.C. The melting in the joint part between the fins 1 and the pipe 2 and the problem of pitting of the pipe 2 are solved; in addition, the deformation and permanent set in fatigue of the fins before and after the brazing are prevented without losing the sacrifitial anode effect of the fins 1 by the Zn in the fins 1.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a heat exchanger.

[Prior art and its problems]

For example, heat exchangers used in automobiles and various other devices are made of linal extruded flat multi-hole tubes made of aluminum or aluminum alloy (hereinafter simply referred to as aluminum) from the viewpoint of their light weight and good thermal conductivity. Fins made of aluminum material are At-5i or At-51-
It has been proposed that they be joined using a brazing material such as Mg alloy.

However, it has been pointed out that the heat exchanger proposed above has problems such as deformation of the material and sag, as well as problems such as deformation of the fins due to wind pressure and the like.

In addition, it is essential for a heat exchanger to have high corrosion resistance, and for this reason, a sacrificial anode material of At-Zn alloy is pasted on the surface of an extruded flat multi-hole tube made of aluminum material,
It has been proposed to provide a Rometzki membrane.

However, it has been pointed out that even though the surface of the extruded flat multi-hole tube &ζZn film is provided, the corrosion resistance of the conventional heat exchanger is not sufficient.

[Disclosure of the invention]

As a result of conducting research on the above-mentioned problems, the inventor of the present invention found that the cause of the problem of deformation and sagging of the material constituting the heat exchanger is due to the size of the solder between the extruded flat multi-hole tube and the fins. They found that this is because the temperature is as high as about 570 to 620°C, and that even if a Zn film is provided as a sacrificial anode material on the surface of the extruded flat multi-hole tube, the extruded flat multi-hole tube Since the temperature at the time of soldering between the tube and the fin is high as mentioned above, Zn diffuses to a depth of approximately 100 to 200 pm in the wall thickness direction of the extruded flat multi-hole tube during brazing, and as a result, the original It was noticed that the sacrificial anode effect could not be achieved and the corrosion resistance was insufficient.

Therefore, the inventor of the present invention proposed that the working temperature of brazing is low and Z
For example, heat exchangers made by bonding and assembling extruded flat multi-hole tubes and fins by reactive soldering using Zn (tt), in which n is precipitated, have problems such as deformation and sagging of the material because the working temperature is low. In addition, since Zn, which does not precipitate during reactive soldering, is electrochemically less noble than At, which constitutes the material of the heat exchanger, no Zn film is provided on the surface of the extruded flat multi-hole tube. Based on this idea, we developed an extruded flat multi-hole tube with no Zn film on its surface and fins using reactive solder using ZnC4z. I tried making a prototype heat exchanger that was joined by bonding.

However, contrary to expectations, this prototype heat exchanger was not satisfactory.

As a result of research into such causes, the present inventor found that
Heat exchangers constructed by reactive soldering using ZnC42 do not have the problem of deformation or sagging of the material due to its low working temperature; Since Zn acts as a sacrificial anode, it is consumed rapidly when put into practical use, and is completely melted in a relatively short period of time, ensuring the connection between the extruded flat multi-hole tube and the fins, and improving the efficiency of heat exchange. It was found that the performance deteriorated.

In addition, surplus Zn can be removed by reactive soldering using a Zn film.
There is also a problem in terms of corrosion resistance, such as non-uniformity in the surface of the extruded flat multi-hole pipe, which causes local corrosion on the extruded flat multi-hole pipe and the formation of through holes. We investigated this.

While conducting research on suppressing bond separation between extruded flat multi-hole tubes and fins in heat exchangers, the present inventor found that suppression of bond separation can be achieved by fins bonded to extruded flat multi-hole tubes. They discovered that this can be achieved by taking into account the constituent materials of the tube, and surprisingly, they also discovered that this also made it possible to solve the problem of pitting corrosion in extruded flat multi-hole tubes.

Furthermore, the problem of fin deformation can be solved by considering the constituent materials of the fins, and in doing so, there is no need to sacrifice the effects of suppressing joint separation and preventing pitting corrosion of extruded flat multi-hole pipes. I found it.

In other words, it has been revealed from these research results that when an aluminum alloy containing approximately 0.13% by weight or more of Zn is used as a constituent material of a fin, this alloy has a higher performance than an aluminum alloy that does not contain Zn. Since the fin also becomes electrochemically base, it acts as a sacrificial anode, and the dissolution of Zn at the joint between the fin and the extruded flat multi-hole tube is suppressed by the sacrificial anode effect of the fin.
In particular, it has been found that fins are usually thin and have a significantly large surface area, so they work as extremely effective sacrificial anodes.As a result, dissolution of Zn at the joint can be effectively suppressed, and the joint separation between the extruded flat multi-hole tube and the fin can be effectively suppressed. I was able to solve the problem, and
discovered that the problem of pitting corrosion of extruded flat multi-hole tubes can also be solved.

Note that even if an aluminum alloy containing more than 6.5% by weight of Zn is used as the constituent material of the fin, the above effect will not be lost; however, if the aluminum alloy contains Zn in a larger amount than this, Even if it is, the degree of effect enhancement is not that great, and if it contains too much Zn, problems will occur with workability into fins and brazing properties when joining fins to extruded flat multi-hole pipes. The content of Zn is about 6
．． It is important that the amount is 5% by weight or less.

Furthermore, if the constituent material of the fins contains not only about 0.3 to 6.5% by weight of Zn but also about 0.1 to 2.2% by weight of Mg, the fins and extruded flat It solves problems such as melting of joints with multi-hole pipes and pitting corrosion of extruded flat multi-hole pipes.It solves problems such as deformation of fins just before and after brazing, without losing the above-mentioned effect of Zn. They discovered that they could solve the problems all at once.

In other words, if a fin is constructed using an aluminum alloy containing Mg at an intermediate stage of research, it is expected that the mechanical strength of the fin will be improved, and as a result, the problem of fin deformation can be solved. Received the revelation of deafness,
Furthermore, they have discovered that the above-mentioned effects due to Zn content are not lost even when Mg is added.

Incidentally, since Zn and Mg are both used as essential components as constituent materials of the fin, the improvement in mechanical strength is better than when only Mg is used as an essential component.

In addition, if the Mg content exceeds 2.2% by weight and becomes too large, the workability into fins will deteriorate, and furthermore, the brazability of the fins to extruded flat multi-hole pipes will decrease. M
It is important to keep the g content below about 2.2% by weight.

Furthermore, as a constituent material of the fin, the above 0.3 to 6.
5 wt.% Zn and about 0.1-2.2 wt.% Mg, as well as about 0.1-1 wt.% Mn, about 0.03 wt.%
~0.3 wt.% Cr, approximately 0.03-0.2 wt.% Z
It has been found that the inclusion of one or more types of n is even more desirable from the viewpoint of adjusting the crystal grains after brazing and increasing the recrystallization temperature.

The present invention was made based on the above research results, and includes a tube made of aluminum or aluminum alloy, about 0.3 to 6.5% by weight of Zn, and about 0.1 to 6.5% by weight of Mg.
The present invention provides a heat exchanger in which fins made of an aluminum alloy containing 2.2% by weight are joined by reactive soldering using a Zn compound such as a Zn film.

In addition, tubes such as extruded flat multi-hole tubes in heat exchangers are
It is made of an aluminum alloy containing about 0.1 to 3% by weight of n, or a Zn film with a thickness of about 0.2 to 10/Jm is coated on the surface of this tube, which serves as a passage for the heat exchange medium and working fluid. By providing such a heat exchanger or by satisfying these requirements at the same time, the corrosion resistance of the heat exchanger can be further improved.

[Examples 1 to 15] FIGS. 1(a) and 1(b) are explanatory diagrams of one embodiment of a heat exchanger according to the present invention.

In the figure, 1 is an ingot made of an aluminum alloy with the composition shown in the table by the usual melting and casting method, which is homogenized, solidified, then hot rolled to form a 4-thick plate, and then intermediately annealed as appropriate. The fins were formed by cold rolling to form a thin plate with a thickness of 0.13 mm, which was then slit as required and then corrugated.

1i, is an extruded flat multi-hole tube made of pure aluminum equivalent to JIS A1050, and the surface of this extruded flat multi-hole tube 2 is coated with about 0.2 A Zn plating film with a thickness of ~10 μm is provided.

Then, the fin 1 and the extruded flat multi-hole tube 2 configured as described above are combined as shown in the figure, and between the fin 1 and the extruded flat multi-hole tube 2, Zn CL 2, Zn powder,
The heat exchanger 3 is assembled by filling a mixed fluff pre-turbidity consisting of an additive and an organic solvent to promote reactive soldering, and performing reactive soldering at 420°C.

[Comparative Examples 1 to 3] A heat exchanger was assembled in the same manner as in Example 1 using an aluminum alloy having the composition shown in the table instead of the aluminum alloy for the fins 1.

[Comparative Example 4] Pure aluminum equivalent to JIS A1050 was used instead of the aluminum alloy of the fin 1 in Example 1, and an extruded flat multi-hole tube 2 was provided with a 1 μm Zn film on the surface.
The heat exchanger is assembled by brazing the two using an At-3i alloy brazing material at 600°C.

〔Characteristic〕

A CASS test was conducted for 720 hours to examine the corrosion resistance of the heat exchanger on each side in which the fins 1 were slit, and the results are shown in the table.

In addition, the unslit fin material was fired during the reaction soldering process, and after about a week had passed at room temperature, the tensile strength and 0.2% proof stress were measured at room temperature, and the results are shown in the table.

- In the table, the X mark indicates separation due to dissolution, the Δ mark indicates slight corrosion, and the ○ mark indicates almost no corrosion.

As can be seen from this table, if the fin is made of an aluminum alloy containing about 0.3 to 6.5% by weight of Zn,
The corrosion resistance of the joint between the fin and the extruded flat multi-hole tube is good, and the pitting corrosion of the extruded flat multi-hole tube is shallow, and the corrosion resistance is good, whereas in the comparative example with an extremely low Zn content, the fin and the extruded It has poor corrosion resistance, as the joint portion with the flat multi-hole pipe melts and separates, and furthermore, the pitting depth of the extruded flat multi-hole pipe is deep, resulting in poor corrosion resistance.

By comparing Examples 2, 13, 14.15 and Comparative Example 2, it was found that the fin and the extruded flat multi-hole tube were
When joining by reaction soldering using 10μ
It can be seen that the corrosion resistance is further improved when the Zn film with a thickness of m is provided.

Furthermore, as can be seen from the measurement of the mechanical strength after firing the fins, if the fins are made of an aluminum alloy containing about 0.1 to 2.2% by weight of Mg, the strength after brazing is Therefore, it can be seen that it is extremely resistant to unexpected deformation during assembly work and deformation due to wind pressure.

〔effect〕

The heat exchanger according to the present invention includes tubes made of aluminum or aluminum alloy, and about 0.3 to 6.5% by weight of Zn and M
The aluminum alloy fins containing approximately 0.1 to 2.2% g are joined by reaction soldering using a Zn compound, which solves the problem of material deformation and sagging even though it is lightweight. In particular, the problem of deformation of the fins due to wind pressure does not occur, and it is highly durable.Furthermore, there is no problem of deformation of these parts when assembling the heat exchanger, so the assembly work efficiency is improved accordingly.
It can be manufactured at low cost, has good brazing properties between the fins and the tube, and is free from problems such as joint separation due to melting of the joint between the fin and tube and pitting corrosion of the tube. It has features such as being able to effectively prevent problems and being highly corrosion resistant.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are explanatory diagrams of an embodiment of a heat exchanger according to the present invention. 1...Fin, 2...Extruded flat multi-hole tube, 3...Heat exchanger. (a) (b) Figure 1 Procedures Amendment Book February 3, 1986

Claims (1)

[Claims] A tube made of aluminum or an aluminum alloy and a fin made of an aluminum alloy containing about 0.3 to 6.5% by weight of Zn and about 0.1 to 2.2% by weight of Mg are bonded by reactive soldering using a Zn compound. A heat exchanger characterized by being joined by attaching.