JPH04313464A - Manufacture of heat exchanger made of aluminum - Google Patents

Abstract

PURPOSE:To execute the brazing at a lower temperature than before, to remarkably reduce the brazing cost, and also, to use a high strength stock of a low melting point which cannot be used up to the present. CONSTITUTION:Immediately after A1 or an A1 alloy stock is subjected to hot extruding of tube stock, the extruded stock concerned is allowed to pass through the inside of a plating tank of a Zn or Zn alloy brazing filler metal and the outside of the tube stock is covered with the brazing filler metal concerned, the extruded tube stock covered with the brazing filler metal is formed as a tube, this tube stock is assembled to a core consisting of an A1 or A1 alloy bare fin and heated and brazed, by which each constituting parts are joined by the brazing filler metal on the surface of the tube stock. Subsequently, the brazing filler metal layer is coated to thickness of 5-100mum, and also, at the time of brazing and heating, a diffusion layer in which Zn is 10-100mum is formed and a sacrifice layer is provided, and moreover, it is desirable that an oxide film on the surface of the A1 or A1 alloy tube is eliminated by applying an ultrasonic wave into the plating tank.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to aluminum heat exchangers such as automobile heat exchanger condensers and evaporators using Zn or Zn alloy brazing material coated tubes for brazing at temperatures below 500°C. The present invention relates to a manufacturing method.

0002

[Prior Art] Most heat exchangers for automobiles are made of Al and A.
L alloy is used and manufactured by brazing method. For example, for capacitors, JIS A 1050, J
IS A 1100, JIS A3003, Al-0.
Extruded aluminum tubes such as 5% Cu alloy, corrugated fins of brazing sheets such as JIS BA 12 PC clad with Al-Si brazing filler metal, and JIS A
6061, JIS A 7N01, etc., combine parts such as unions, apply flux, and braze at a temperature of 60
It is brazed at about 0℃. In recent years, there has been an increasing demand for lower brazing temperatures in order to reduce brazing costs. The low-temperature brazing method currently in practical use involves applying a mixture of Zn powder and ZnCl2-based flux to a core assembled from Al material.
It is known that Zn is brazed by heating to about 450°C.

0003

[Problems to be Solved by the Invention] Recently, in response to the demand for lighter weight automobiles, there has been a demand for lighter weight heat exchangers, that is, thinner materials. Currently, brazing sheets clad with Al-Si brazing filler metal are used for the fins of many heat exchangers, but when the brazing filler metal cladding on the surface of the fin melts, Si forms at the grain boundaries of the core material. As a result, the thickness of the unmelted core material, which is effective for strength, decreases and the high-temperature strength of the fin decreases. As a result, a phenomenon in which the fin collapses, so-called buckling, tends to occur, which prevents the fin from becoming thinner. One solution to this problem is to lower the brazing temperature. Therefore, we considered using Zn or Zn alloy, which can reduce the brazing temperature, as a brazing material and hot-pressing it to the Al alloy fin material. However, hot compression bonding is relatively easy when the brazing filler metal is an Al alloy;
It is difficult to hot press bond a Zn alloy to an Al alloy because of the different properties of Zn and Al as metals. This is Zn and Al
Due to the crystal structure of Z
This is because n-alloys are softened during processing, which causes cracks to occur during hot press-bonding, or to prevent proper press-bonding. A second solution is to make the fin material bare and coat the extruded pipe material with a low-temperature brazing material, but such a material has not yet been developed. These problems have made it difficult to reduce the weight of heat exchangers. Currently, Zn alloy is thermally sprayed or plated on Al alloy, but this is for the purpose of diffusing Zn into Al alloy to improve corrosion resistance, and is not for use as a brazing material. There wasn't.

0004

[Means for Solving the Problems] In order to solve the above problems, as a result of various studies, the fin material was made thinner by using aluminum alloy bare material, and the brazing material was made of a low melting point brazing material.
We have developed a method for manufacturing an aluminum heat exchanger that solves all of the above problems at once by coating an extruded tube made of l-alloy and brazing it at a low temperature.

[0005] That is, in the present invention, immediately after hot extrusion of Al or Al alloy material into a pipe material, the extruded material is passed through a plating bath of Zn or Zn alloy brazing material having a melting point of 500°C or less to coat the outside of the pipe material. is coated with the brazing material, the extruded tubing material coated with the brazing material is used as a tube, and this tubing material and Al or Al
It is characterized by assembling a core made of alloy bare fins, heating it, and brazing it to join each component with the brazing material on the surface of the tube material.
It is effective to coat a brazing metal layer with a thickness of 5 to 100 μm and to provide a 10 to 100 μm diffusion layer of Zn as a sacrificial layer using brazing heat. It is preferable to perform plating while applying an electric current to remove the oxide film on the surface of the Al or Al alloy tube.

[0006]

[Operation] JIS A 1100, JIS A 3003, and JIS A 1100, JIS A 3003, and Al alloy materials for hot extruded tube materials.
Most A, including Al-0.5%Cu alloy, etc.
l alloy can be used. In particular, in normal brazing using Al-Si brazing filler metal, even if the strength is high, alloys with a solidus temperature of 620℃ or less are It was difficult to use. For example, JIA A 2017 (melting point 513-641
℃), JIS A5052 (melting point 593-649 ℃)
), JIS A 7N01 (melting point 615-650°C
), JIS A 7075 (melting point 476-638°C
) alloys have high strength but have low melting points and cannot be used. However, if a brazing filler metal with a low melting point is used, these alloys can be used, and the material can be made thinner. Other alloys with lower melting points can also be used depending on the melting point of the wax to be coated. Zn or Zn alloy with a melting point of 500°C or less includes pure Zn, Zn-0 to 28% Al alloy, Zn-Al-
Cu-based alloy, Zn-Al-Sn-based alloy, Zn-Al-C
These include d-based alloys, Zn-Al-Ag-based alloys, and other Zn-Al-based alloys can also be used. The reason why the brazing filler metal composition is limited to Zn-based alloys is because S is considered to be another low melting point brazing filler metal.
N alloys, Pb alloys, etc. have problems with corrosion resistance, and furthermore, there is a problem of reduced joint strength due to too low melting points, so we selected Zn-based alloys, which have good performance in terms of melting point, corrosion resistance, strength, etc. The hot-dip plating method requires that the surface oxidation does not proceed immediately after extruding the Al alloy, and that the extruded tube is passed through a plating bath in which Zn or Zn alloy is melted at a high temperature, and then coated with a brazing material. Adopt the method of pulling it up. The brazing material layer of the brazing material coated extruded tube thus obtained is uniform and has the necessary amount of brazing material as a brazing material. The reason why the thickness of the brazing metal layer is limited to 5 μm to 100 μm is that
If it is less than m, the amount of brazing material required for brazing is insufficient.
If it exceeds 100 μm, the weight will increase, and furthermore, the amount of melted brazing material will be excessive, resulting in an abnormal fillet. Note that applying ultrasonic waves to the plating bath has the effect of obtaining a more stable plating layer.

The thus produced extruded tube coated with a low melting point brazing material is bent into a predetermined shape in the case of a serpentine type capacitor, combined with a corrugated bare fin, and heated to a brazing temperature of 380 to 500.
Brazing is performed by heating at a temperature of 1 to 10 minutes at a temperature of 1 to 10 minutes. For example, JIS A 1050, JI
AA 1100, JIA A 3003, Al-1%
Bare materials such as Mn-1.5% Zn alloy and JIS A 6951 alloy can be used. Furthermore, the above-mentioned low-melting-point, high-strength materials can also be used, allowing for thinner walls. A chloride-based or fluoride-based flux such as ZnCl2 or KCl is used as the flux and is applied to the core for brazing. Further, the atmosphere in the furnace may be air or a non-oxidizing atmosphere, but a non-oxidizing atmosphere can reduce the amount of flux used. Holding time 1-10 at brazing heat temperature 380-500℃
By brazing in minutes, the Zn of the brazing material diffuses into the tube to form a sacrificial layer. This Zn diffusion layer is
The reason for limiting the thickness to 100 μm is that if the thickness is less than 10 μm, the effect as a sacrificial layer will be small and the corrosion resistance will be poor, and if it exceeds 100 μm, the amount of self-corrosion will increase and the corrosion resistance will deteriorate.

[0008]

[Examples] The present invention will be explained below with reference to Examples.

(Example-1) Using JIS A 1150, a width of 22 mm, a height of 5 mm, and a wall thickness as shown in FIG.
Immediately after extruding a 0.8 mm extruded multi-hole tube (1) at 480°C, an extrusion device (2) as shown in Figure 2 was used.
A brazing filler metal-coated extruded tube (6) was manufactured using an apparatus having a continuous plating tank (4). In the figure (3)
(5) indicates a die, and (5) indicates a plated filler metal. A Zn-5% Al alloy was used as the brazing material to obtain a brazing material layer having the thickness shown in Table 1.

[0010] As shown in Fig. 3, these pipe materials are made into a JIS A tube (6) with a width of 22 mm and a wall thickness of 0.1 mm.
3003 alloy corrugated bare fin (7) is assembled into a core, LiCl, KCl, ZnCl2
A 50% concentration solution of chloride-based flux consisting of the following was applied and brazed at a brazing temperature of 420° C. and a holding time of 3 minutes in the air to evaluate brazing properties. Brazing properties were evaluated by comparing the test pieces shown in Figure 3 with those made using conventional alloys and brazing methods, and rated ○ if a normal fillet was formed, and × if not. The results are shown in Table 1. The comparison material is a tube material with a width of 22 mm and a height of 5 m.
m, wall thickness 0.8mm JIS A 1050 alloy,
The fin material is JIS BA12P with a width of 22 mm and a wall thickness of 0.1 mm, clad with Al-Si brazing filler metal.
Brazing was performed using C alloy at a brazing temperature of 600° C. and a holding time of 3 minutes in the atmosphere.

[0011]

[Table 1]

As is clear from Table 1, inventive example No.
1~No. When using a tube with a brazing material layer thickness of 4,
No. produced by the conventional method. A normal fillet equivalent to No. 8 was obtained, and it was found that it could be used satisfactorily as a material for brazing. On the other hand, comparative example No. In No. 5, the amount of brazing material was insufficient, the fillet was extremely small, and the brazing performance was poor. Also, Comparative Example No. 6, No. In No. 7, a large amount of the brazing material melted out, and too much brazing material accumulated in the fillet portion, so that it could not be said that the brazing property was good.

(Example 2) Immediately after extruding a tube of width 22 mm, height 5 mm, and wall thickness 0.8 mm as shown in Fig. 1 using JIS A 1050 alloy at 460°C, it was extruded as shown in Fig. 2. A brazing material-coated tube was manufactured using an extrusion device with a continuous plating layer.

[0014] Zn-15% Al alloy is used as the brazing material,
Tube materials with brazing metal layer thicknesses of 5 μm, 30 μm, and 70 μm were obtained, and these were JIS-shaped with a width of 22 mm and a wall thickness of 0.15 mm.
A core as shown in FIG. 3 was assembled by combining with corrugated fins made of A3003 alloy. These include LiCl
A 20% concentration solution of a chloride-based flux consisting of , KCl, ZnCl2, etc. was applied, and brazing was carried out at a temperature shown in Table 2 for a holding time of 3 minutes in a nitrogen atmosphere. As a result, a Zn diffusion layer having a thickness as shown in Table 2 was obtained in the tube. The influence of the Zn diffusion layer on the corrosion resistance of these cores was evaluated from the appearance and weight loss in a 360 hour salt spray test, and the results are shown in Table 2. In addition, the corrosion resistance evaluation was compared with conventional materials, and those that were equivalent or better were rated ○.
The equivalent value is represented by a △ mark, and the equivalent or lower value is represented by an × mark.

[0015]

[Table 2]

As is clear from the table, inventive example No.
9~No. When the Zn diffusion layer was provided with an appropriate thickness as in No. 12, better corrosion resistance was exhibited compared to the conventional example. On the other hand, comparative example No. As in No. 13, the thickness of the brazing metal layer is 5 μm.
If the tube material is as thin as this, a sufficient Zn diffusion layer cannot be obtained in the tube material, and the effect as a sacrificial layer is small, so the corrosion resistance is the same as that of conventional materials. Also, Comparative Example No. Even when the thickness of the brazing metal layer is 70 μm as in No. 14, the brazing heating temperature is 49
At a high temperature of 0° C., Zn diffusion progresses and a thick Zn diffusion layer is formed. If the Zn layers were too thick, the amount of corrosion of the diffusion layer itself would increase, and the corrosion resistance could not be said to be good.

(Example 3) In the apparatus shown in FIG. 2, 5
Width 22mm, height 5mm, wall thickness extruded at 00℃
A 0.8 mm JIS A 3003 alloy multi-hole tube was passed through a plating bath to which 20 kHz ultrasonic waves were applied, and a Zn-15% Al alloy brazing material was coated on the extruded tube to form a brazing material layer with a thickness of 40 μm. A material-coated extruded tube was manufactured.

[0018] This tube and corrugated width 22
A corrugated bare fin (7) is combined between a tube (6) bent in a serpentine shape as shown in Fig. 4 using an Al-1%Mn-2%Zn alloy bare fin with a thickness of 0.1 mm. A serpentine type capacitor was assembled, a 10% concentration solution of flux consisting of LiCl, KCl, and ZnCl2 was applied, and brazing was performed at a brazing temperature of 480° C. and a holding time of 5 minutes in a nitrogen atmosphere. Note that (8) in the figure indicates an aluminum union. For comparison, J with a width of 22 mm, a height of 5 mm, and a wall thickness of 0.8 mm
IS A 3003 alloy extruded multi-hole tube and width 22m
A similar capacitor was assembled using a JIS BA 12PC brazing sheet with a wall thickness of 0.1 mm, coated with a 10% concentration solution of fluoride flux whose basic composition was AlF3 and KF, and heated at a temperature of 600°C as described above. Brazed in a furnace.

When the bonding condition after brazing was investigated, it was found that the bonding condition between the fin and the extruded tube in the capacitor using the material according to the present invention was good, and was similar to that of a comparative product using a brazing sheet. However, while the fins of the capacitor of this example were normal, the fins of the capacitor of the comparative example were buckled.

(Example 4) In the apparatus shown in FIG. 2, 5
Width 16mm, height 2mm, wall thickness extruded at 00℃
A 0.5 mm Al-0.5% Cu alloy multi-hole tube was passed through the plating bath to form a brazing material Zn-5% Al-3% C.
A brazing material-coated extruded tube was manufactured by coating the outside of the extruded tube with U alloy. The thickness of the brazing material layer of the tube was 80 μm. Furthermore, the device shown in Figure 2 has an outer diameter of 20 mm and a wall thickness of 1.6 m.
After extruding a pipe made of JIS A 3003 alloy of 40 m at 480℃, Zn-5%Al-3%Cu alloy was coated on both sides.
It was plated to a thickness of μm and made into a header pipe.

Using these, as shown in FIG. 5, a tube (6) with a width of 16 mm and a thickness of 0.07 mm was corrugated between the tubes (6).
A parallel flow type condenser is assembled by combining a JIS A 3004 alloy bare fin (7) and a header pipe (9), and LiCl, KCl, Z
A 20% concentration solution of flux consisting of nCl2 was applied, and brazing was carried out in a nitrogen atmosphere at a brazing heating temperature of 480° C. and a holding time of 10 minutes. In the figure, (8) indicates an aluminum union. For comparison, width 16mm, height 2mm,
An extruded multi-hole tube made of JIS A 1050 alloy with a wall thickness of 0.5 mm, and a fin material with a width of 16 mm and a wall thickness of 0.07 mm.
JIS BA 12PC alloy with a diameter of 20 mm and a wall thickness of 1.6 mm is used for the header pipe.
A parallel flow type capacitor as shown in FIG. 5 was assembled using SA 3004 alloy. A 10% concentration solution of fluoride flux with basic composition of AlF3 and KF was applied to this capacitor, and the brazing temperature was increased to 60°C.
Brazing was performed at 0°C for 3 minutes in a nitrogen atmosphere.

[0022] When we investigated the bonding conditions after brazing, we found that the condenser using the material of the present invention had good bonding conditions between the fin and the extruded tube, and between the extruded tube and the header, compared to a comparative product using a conventional brazing sheet. It was the same. However, in the capacitor using thin fins in the comparative example, the fins buckled, whereas in the capacitor using the material of the present invention, fins with the same thickness as in the comparative example were used, but buckling of the fins was not observed. I couldn't.

[0023]

[Effects of the Invention] As described above, according to the present invention, it is possible to supply pipe materials for heat exchangers that can be brazed at lower temperatures than before, and it is possible to significantly reduce brazing costs. This has significant industrial effects, such as making it possible to use low-melting-point, high-strength materials that were previously unavailable.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an extruded multi-hole tube.

FIG. 2 is a schematic diagram of an apparatus in which an extrusion device and a plating tank are connected.

FIG. 3 is a side view of a test piece that combines a brazing material coated extruded tube and fins.

FIG. 4 is a perspective view of a serpentine type capacitor.

FIG. 5 is a side view showing a parallel flow type capacitor.

[Explanation of symbols]

1 Extruded multi-hole tube 2 Extrusion device 3 Dice 4 Plating tank 5 Plating brazing material 6 Brazing material coated extruded tube 7 Bearfin 8 Al union 9 Header pipe

Claims (4)

[Claims] Claim 1: Immediately after hot-extruding Al or Al alloy material into a pipe material, the extruded material is passed through a plating bath of Zn or Zn alloy brazing material having a melting point of 500° C. or less to coat the outside of the pipe material with the solder material. An extruded tube material coated with a wax material and a brazing material is used as a tube, and a core made of this tube material and an Al or Al alloy bare fin is assembled, and the core is heated and brazed to remove the wax on the surface of the tube material. A method for manufacturing an aluminum heat exchanger, characterized in that each component is joined by a material. 2. The method for manufacturing an aluminum heat exchanger according to claim 1, wherein plating is performed while applying ultrasonic waves in the plating bath to remove an oxide film on the surface of the Al or Al alloy tube. 3. The method for manufacturing an aluminum heat exchanger according to claim 1, wherein the brazing material layer is coated with a thickness of 5 to 100 μm. 4. 10 to 100% of Zn by brazing heat
4. The method for manufacturing an aluminum heat exchanger according to claim 1, wherein a .mu.m diffusion layer is provided as a sacrificial layer.