JPH0338332B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to improving aluminum alloys for brazing, and aims to provide an Al alloy for heat exchanger connectors that has excellent burning resistance and stress corrosion cracking resistance. Generally, an aluminum heat exchanger requires a connector, and as shown in Fig. 1, an extruded tube 1 and a connector 2 having a screw at its tip are connected via a brazing material 3. . Further, FIG. 2 shows a drawing tube 1' and a connector 2' joined together via a brazing material 3'. These connectors 2 and 2' require excellent mechanical properties when used, so after brazing, they are made of alloys that easily harden when cooled and then age harden at room temperature, such as JIS 7003 area No. 7. is used. The tube 1 or drawing tube 1' is made of industrial pure aluminum such as JIS1050, 1100, 1200 or Al-
Mn-based alloys such as JIS3003, 3203, 3005, Al-Mg
-Si-based alloys such as JIS6063 are used. On the other hand, when an Al-Si alloy is used as the brazing material, its melting temperature is 577 to 600°C. The brazing methods include torch brazing, furnace brazing, and immersion brazing using flux, as well as vacuum brazing and inert gas brazing that do not use flux. The standard brazing temperature is 600 to 630°C, but in the case of torch brazing, it can instantaneously rise to 640°C. Due to such variations in brazing temperature, when the connector material reaches a melting start temperature or higher, melting occurs at the grain boundaries, a so-called burning phenomenon, which can cause cracking or cause stress corrosion cracking during use. It was hot. As a result of intensive research aimed at improving these drawbacks, the present invention improves the burning resistance during brazing at high melting temperatures without reducing functional performance to the extent that wear of the threaded portion becomes a problem during use. At the same time, we have discovered an aluminum alloy for brazing that has excellent strength and stress corrosion cracking resistance after brazing. That is, the present invention provides (1) Zn3.1~3.9wt%, Mg0.3~0.8wt%, Mn0.2~
Alloy consisting of 0.9wt%, Zr0.05~0.5wt%, balance Al, (2) Zn3.1~3.9w%, Mg0.3~0.8wt%, Mn0.2~
0.9wt%, Zr0.05~0.5wt% and Cu0.01~0.3wt
%, or any one of Ti0.01~0.3wt%
It is an alloy that contains one or both seeds and the remainder is Al. In the present invention, Zn and Mg are necessary components for mechanical performance, especially for hardening by general cooling after brazing heat, and then aging hardening by leaving at room temperature, and less than 3.1 wt% Zn and 0.3 wt% Mg. In the case of , the melting temperature increases and it is extremely effective against burning, but the mechanical performance after brazing heat decreases, for example, the tensile strength becomes less than 10 kg/mm ² , and the wear of the screw part during use is reduced. cause Also Zn3.9wt%,
If Mg exceeds 0.8wt%, the melting temperature will drop below 619°C, causing burning. Furthermore, Mn and Zr are added to supplement the mechanical performance produced by reducing the amounts of Zn and Mg added, and to improve stress corrosion cracking resistance. Note that it does not affect the melting temperature. If the amount added is less than 0.2wt% Mn and 0.05wt% Zr, mechanical performance and stress corrosion cracking resistance cannot be improved, and even if it exceeds 0.9wt% Mn and 0.5wt% Zr, the mechanical performance and resistance There is no noticeable improvement in stress corrosion cracking resistance, and instead coarse intermetallic compounds are formed, which impairs workability. Furthermore, both Ti and Cu improve stress corrosion cracking resistance, but if the amount added is less than 0.01wt%, no effect will be seen, and if it exceeds 0.3wt%, the effect will hardly change. It warps and forms coarse intermetallic compounds, which impairs workability. Next, examples of the present invention will be described. Examples 1-2 and Comparative Examples 1-3 An alloy having the composition shown in Table 1 was melted and a billet of 230φ was cast. This billet was homogenized at 500°C for 3 hours, then immediately hot extruded at 500°C to produce a 50φ round bar, which was then cold drawn to produce a hexagonal bar (- This was used as a sample of material H). This sample was processed into a connector (union) as shown in the drawing, and was brazed to a 1050 odd-shaped tube or a 3003 drawing tube through a brazing material to obtain a heat exchanger. The brazing method used was furnace brazing using flux, and was carried out at 620°C. In order to test the performance of the heat exchanger obtained in this way, a torque of approximately 3 kg·m was applied to the screw part, tensile stress was applied to the tip part, and a dry-wet alternating test (10 The stress corrosion cracking property was measured by dipping for 50 minutes and drying for 50 minutes. Furthermore, a round bar tensile test piece was processed from the hexagonal bar, heated in the same way as above assuming brazing heat, and then subjected to a tensile test. The results are shown in Table 2.

【table】

【table】

[Table] Notes: ○ None △ Some × × The alloy of the present invention has excellent burning resistance during brazing, and stress corrosion cracking resistance during use, as well as high tensile strength and wear resistance. When used as an excellent connector, the threaded part did not wear out. Comparative example products (2) and (3) have excellent burning resistance and stress corrosion cracking resistance;
The mechanical performance of (2) deteriorated and the threaded portion was worn out, making it unusable as a connector. In addition, Comparative Example Product (3) had poor workability during material production and cracked by more than 50%, making it impossible to use it as a material. In addition to connectors, the alloy of the present invention can also be used for parts of heat exchangers to be brazed, such as bracket materials for radiators. As detailed above, the present invention has remarkable effects such as being able to provide an excellent heat exchanger without causing burning or stress corrosion cracking resistance during brazing.

[Brief explanation of the drawing]

Figures 1A and 2A are cross-sectional views showing the joint between the connector and the tube or drawing tube, Figure 1B is a cross-sectional view of the connector taken along line X-X in Figure 1A, and Figure 2
FIG. B is a sectional view of the connector taken along line Y--Y in FIG. 2A, and FIGS. 1C and 2C are sectional views of the brazing material. 1...tube, 1'...drawing tube, 2,2'...
Connector, 3,3'...brazing material.

Claims (1)

[Claims] 1 Zn3.1~3.9wt%, Mg0.3~0.8wt%, Mn0.2~
An aluminum alloy for brazing characterized by comprising 0.9wt% to Zr0.05 to 0.5wt%, the balance being Al. 2 Zn3.1~3.9wt%, Mg0.3~0.8wt%, Mn0.2~
0.9wt%, Zr0.05~0.5wt% and Cu0.01~0.3wt%,
An aluminum alloy for brazing, characterized in that it contains one or both of 0.01 to 0.3 wt% of Ti, and the balance is Al.