JPS59185765A - Manufacture of bonded parts of aluminum alloy - Google Patents

Abstract

PURPOSE:To ensure stable performance and to improve the productivity by heat- treating a hollow section obtd. by porthole hot extrusion under prescribed conditions before cutting so as to prevent bonded parts from causing defects by extrusion. CONSTITUTION:A billet of an Al-Zn-Mg alloy JIS7 No.1 is formed into a hollow section by porthole hot extrusion. The hollow section is heat-treated at 590- 620 deg.C for >=1min before or after cutting. By this method, bonded parts are prevented from causing defects, stable performance is ensured, and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing coupling parts such as heat exchanger piping joints and nuts by boathole extrusion of an aluminum-zinc-magnesium alloy.

In general, unions and nuts for connecting parts for heat exchanger piping are made of aluminum, especially aluminum-zinc-magnesilum alloy, which has good machinability and high strength.

Initially, extruded or drawn rods were used as raw materials for connecting parts such as joints and nuts, and these were finished into final parts by external and boring processing.

Next, in order to reduce manufacturing costs, boring was omitted,
Hollow rods with the cross-sectional shape of a hexagonal or other joint part were made as raw materials for parts by mandrel extrusion without seams.

In order to further reduce manufacturing costs, a method was adopted in which hollow rods were manufactured using boathole extrusion, which has a faster extrusion speed than mandrel extrusion and has a clean surface without burning. An example of this boathole extrusion method will be explained below with reference to the drawings. Figure 7 shows the extrusion die, Figure (A) is a side sectional view of the combined dies A and B, Figure (B) is a back view of die A seen from the billet side, and Figure (/→ is a side sectional view of die B). According to the figure, the metal extruded by boat hole extrusion is divided into y parts by the die hole of die A and extruded in the direction of the arrow, and when passing through die B, the divided metal passes through the boat. The metal is hot-pressed in hole 3, and the metal comes out as a hollow section through the gap between the die hole of die B and the mandrel, that is, the hole formed in the hollow section.The porthole extrusion method reduces manufacturing costs. This is the most suitable method for manufacturing hollow sections at a low cost, but as mentioned above, hot crimping creates joints in the extruded sections.Such joints can be made with minimal moss even when other boat hole combination dies are used. Such seams are especially Aj-Z
Portholes tend to appear as defects in porthole extrusions of n-MP alloys. This is a defect in which when the joint part is exposed to a severe corrosive environment, it corrodes preferentially over other parts, reducing the joint strength.

Given the above circumstances, conventional joint parts such as joints and nuts made of aluminum-zinc-magnesium alloys are either made from extruded rod material by boring the outside, or made from seamless hollow rod material by mandrel extrusion method. However, the only way to manufacture it was by cutting the threaded part.

The present invention has been made in view of the above points, and it is possible to prevent defects in joint parts caused by boathole extrusion using a simple method, ensure stable performance, and achieve high productivity. The purpose is to obtain a manufacturing method. That is, A
At-Zn-M'! is used as the At alloy in the production of A7 alloy joining parts by hot extruding T-alloy billets into hollow shapes and cutting the shapes. Alloy JI87NO
/ using boat hole hot extrusion method for extrusion,
It is characterized by performing high temperature heat treatment at a temperature of J9θ~t, zo0a, heating time/minute or more either before or after cutting the threaded part, etc., and when erecting an Ala heat exchanger by brazing. At brazing, which is a high temperature heat treatment of AA alloy joint parts used in joints, is the same as the operation (=
This is a method for manufacturing an At alloy bonded part, characterized in that the heating time is between / and 3θ minutes.

The present invention will now be explained in more detail with the following experiments. The phenomenon in which defects occur in the metal joints of the kt-Zn-MP alloy JI87NO/ caused by boathole extrusion will be explained by experiments/, and the phenomenon in which defects are eliminated by high-temperature heat treatment according to the present invention will be explained by experiments λ.

Experiment/Acidic salt spray test (3% Naat Decaacetic acid, PHI.

J-000) for 2 gθ hours, the joint g in the sample appears in the external appearance as shown in FIG. 2 (side view of the sample).

This is because the joint portion 6 corrodes more preferentially than the vicinity thereof. Line analysis of the sample with EPMA before the corrosion test is shown in Figure 3 (vertical axis is component amount, horizontal axis is analysis location)
As shown in the figure, Zn and MP, which are the main components of the above-mentioned alloy, are concentrated at the joint part B, and conversely become diluted in the vicinity thereof.

Therefore, a local battery is formed between the two due to the potential difference, and as a result, the joint portion dissolves preferentially. The concentration of oxygen O is also slightly high, which indicates that oxides are involved.

Experiment λ, Next (=Experiment/Similarly to the experiment/, if a sample containing a metal joint is heated for more than 7 minutes at a temperature of 0 to t2000, My, Zn, and ○, which were concentrated in the joint, will diffuse. The results of the analysis are shown in Figure G. According to Figure y, the concentration distribution of MP, Zn, and O became uniform. No preferentially affected defects were found.

For reference, Photo 1 shows the appearance after the corrosion test in Experiment 1, and Photo 2 shows the appearance after the corrosion test of the product subjected to the high temperature heat treatment according to the present invention in Experiment 4.

The condition for high-temperature heat treatment is temperature! 90-J, 2θOc, time of 7 minutes or more is! If the value is less than 000 or less than 7 minutes, the concentrated elements at the seam will not be completely diffused until they become uniform, and if it exceeds -θ0c, the A4-Zn-My alloy J-5
This is because since the solidus temperature of zNo/ is exceeded, a burning phenomenon (melting of grain boundaries) occurs, which is undesirable.

In addition, when assembling an aluminum heat exchanger by brazing, the manufacturing method that involves simultaneous heating of the aluminum joint parts for piping used in the joints involves extruding JI87NO/ into a boat hole and cutting it into the shape of the part. The piping (second installation) is to heat-treat the parts at a high temperature together with the brazing process at a brazing temperature of !Q-620°0.In this case, the brazing time, that is, the high-temperature heat treatment time, must be within 3θ minutes. Heating for more than 30 minutes has no effect on the diffusion of concentrated elements in the metal joint, but has a negative effect on the brazing, i.e. the aluminum solder forming the joint, e.g. At-8i brazing material. This is because 81 diffuses from the fillet into the base metal, reducing the strength of the joint.
E37NO/ has a tensile strength of 3011/rrun or more after natural aging after brazing and a Pinkers hardness of 10.
This is because the value becomes 0, resulting in appropriate performance as a joint component.

Next, examples of the present invention will be described.

Example/At-Zn-MP alloy J with composition shown in Table 1
A billet of I87NO/ is heated to 4t♂θ0C,
<120℃ using the boathole die shown in Figure 7.
Perform hot extrusion with 2 g of opposite side, dark, hollow /! A hexagonal bar with a diameter of φ was made, and after air cooling, it was heated at high temperature under the conditions within the range of the present invention as shown in the Example column of Table 1. For up to! After processing the type, artificial aging is performed for 24 hours at /2θ00 and T! manufactured the material.

After cutting nuts from this material, these samples were subjected to the acid salt spray test (3% Nact decaacetic acid, PH5, t0°C) for 24t0 hours to examine the corrosivity of the metal joints. As a comparative example, sample A≦~?
Regarding the three types, the high-temperature heat treatment during sample preparation was outside the scope of the present invention, but the rest was the same as in the example, and the conventional example, in which high-temperature heat treatment was not performed and the other sample preparation was the same as in the example. The corrosive properties of the samples were also investigated. The results are also listed in Table 2. For evaluation of corrosion resistance, those that were not corroded were marked O (good), and those that were corroded as shown in Fig. 2 were marked X (poor).

According to Table 2, Examples A/~! according to the invention! All have good corrosion resistance, and defects in metal joints are completely prevented. Comparative example jI6 in which the high-temperature heating conditions are not according to the present invention
Conventional example JIL'7 which was not subjected to t-s-er and high-temperature heat treatment had poor corrosion resistance.
Table Example 1: A billet of At-Zn-MSI' alloy JI87NO/ having the composition shown in Table 1 was heated to 400°C.
Hot extrusion was performed using the porthole die shown in Figure 7 to produce a hollow hexagonal bar with opposite sides: 14tyam, hollow/4tφ, and after air cooling, artificial aging treatment was performed to achieve T! The material is cut into a nut, which is inserted into the flared piping when brazing the heat exchanger.
In order to braze one end at the same time as the inlet of the heat exchanger,
High-temperature heating by brazing was performed under conditions within the scope of the present invention as shown in the Examples column of Table 3. Thereafter, this nut part was subjected to the acid salt spray test described above to examine the corrosion resistance of the metal joint. The results of the corrosion resistance of the nut parts and the waxiness of the heat exchanger are also listed in the third column. The evaluation of corrosion resistance was the same as in Example/. The brazeability was evaluated as ``poor'' if the formation of the joint fillet between the fin and 'f:L-p was good, and if o1 was defective. Δ is a slightly better case. As a comparative example, brazing was performed at a temperature and time not according to the present invention, and a high-temperature heat treatment was carried out outside the range limited by the present invention.

The results are also listed in Table 3.

Table 3 According to Table 3, all of Examples A-27 according to the present invention had good corrosion resistance, and defects in metal joints were completely prevented. Also, although brazing was performed under the conditions of high-temperature heat treatment according to the present invention, all the samples (two of them had good brazing results. The sample from Okiya 2! was slightly better (Δ mark)
Because BA'13'7B was used as the brazing material, both brazing strength and time seemed to be insufficient.

Judging from the above results, defects in metal joints due to boat hole extrusion can be completely prevented and stable performance can be obtained by the simple method of carrying out the brazing operation by high-temperature heat treatment of the present invention. It was also confirmed that the brazing was performed well even though the operation and high-temperature heat treatment were carried out at the same time.

As mentioned above, when A4 alloy is used for connectors for heat exchangers, for example, nuts and nuts for car cooler piping, if manufactured according to the present invention, products with stable performance can be obtained, and the production cost is lower than that of conventional manufacturing methods. (It is significantly lower than 1 and is extremely effective industrially.

[Brief explanation of the drawing]

Figure 1 shows boat hole combination dies A and B, (A) is a side sectional view, (B) is a back view of die A, (/→
is a front view of die B. Figure 2 is an external view of the porthole extrusion material after a corrosion test, and Figure 3 is the EPMA of the defective part.
Figure 3 shows the measurement results of EPMA in which defects were prevented by the present invention. /:Dice hole 2 of A die:Mandrel 3:Port hole:Dice hole 1 of B die:Formation hole of hollow material ≦:Defect location of joint part Pole diagram Fig. 2 Stirring Fig. 3 Fig. 4

Claims (2)

[Claims] (1) In the production of aluminum alloy joint parts in which an aluminum alloy billet is made into a hollow shape by hot extrusion and the shape is cut, an aluminum-zinc-magnesium alloy JIS7NO is used as the aluminum alloy.
/ using boat hole hot extrusion for extrusion,
Temperature J-90 ~ either before or after cutting
A method for manufacturing an aluminum alloy bonded part, characterized by performing a high temperature heat treatment at θ°C for a heating time of 7 minutes or more. (2) When assembling an aluminum heat exchanger by brazing, high-temperature heat treatment of the aluminum alloy joint parts used in the joints is performed at the same time as the aluminum brazing operation, and the heating time is 7 minutes or more and 30 minutes or less. A method for manufacturing an aluminum joint component according to claim 1, characterized in that: