JPH0360896B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an Al alloy for heat exchanger piping, and specifically, it is used for piping materials for automobile air conditioners and for joining to Al alloy heat exchangers such as oil coolers and radiators. This relates to an Al alloy with improved pitting corrosion resistance. [Conventional technology] Conventional air conditioners for automobiles are as shown in Figure 1.
A condenser 1 consisting of an Al alloy heat exchanger and an evaporator 2 are connected by a pipe 3, and a compressor 4 or receiver 5 for compressing a refrigerant such as Freon is provided between them. Initially, Cu pipes were used for piping, but recently Al pipes have been used to reduce weight and cost. Such Al pipes are shown in Table 1.
JIS3003 (Al-Mn alloy) or JIS1100 (pure Al alloy)
Most of them are made by continuous drawing of normally extruded raw tubes, and have an outer diameter of about 8 to 16 mm (wall thickness of about 1 to 1.5 mm).
1.5mm) is used. Al tubes shown in Table 1 are also used for the inlet and outlet pipes of radiators and the like, and those having an outer diameter of about 8 to 34 mm are usually used.

[Problem that the invention seeks to solve]

The pipes of the air conditioner and the pipes connected to the radiator are mainly installed in the engine room of an automobile. Freon flows inside the air conditioner piping, and cooling water controlled by an inhibitor flows inside the radiator, so there are no problems with corrosion. However, the exterior of the vehicle is subject to corrosion due to the environment in which the vehicle is used, and in areas where snow melting agents are sprayed, such as coastal areas and cold regions in particular, salt can cause through-pitting corrosion, which has become a problem. For example, if even one point develops through-hole pitting and refrigerant leaks, the air conditioner will lose its cooling function, and the radiator will seize up and damage the engine. As a countermeasure against these problems, anticorrosion by painting is a simple method, but a sufficient effect cannot be obtained. The most effective method is to use an Al-Zn alloy, for example, one clad with JIS7072 shown in Table 1, on the outside of the piping or pipe. Such clad tubes are usually clad during extrusion, but
Increased costs are unavoidable due to the labor involved in manufacturing. [Means for solving the problem] In view of this, the present invention has been developed based on various studies on the current JIS 3003 and 1100,
Si of about 0.3 to 0.4 wt% (hereinafter wt% is simply abbreviated as %)
It was discovered that about 0.5 to 0.6% of Fe deteriorates pitting corrosion resistance, and as a result of further investigation, it was found that it has strength equal to or higher than JIS3003 and has far superior pitting corrosion resistance, and is suitable for automotive air conditioners. piping, radiators,
We have developed an Al alloy for heat exchanger piping that has excellent pitting corrosion resistance and is suitable for piping materials such as oil coolers. One of the alloys of the present invention has Cu0.25~1.0%, Mn0.85
Contains ~1.5% and impurities Si and Fe, respectively.
It is characterized by being regulated to 0.2% or less, with the remainder consisting of Al and other unavoidable impurities. In addition, another one of the alloys of the present invention is Cu0.25~1.0
%, Mn0.85~1.5%, further Mg0.3% or less, Cr0.3
% or less, Zr 0.3% or less, and contains one or more of the following, and the impurities Si and Fe are controlled to 0.2% or less each, with the remainder consisting of Al and other unavoidable impurities. It is characterized by: That is, the present invention eliminates Si and impurities in the alloy composition.
The content of Fe is regulated to 0.2% or less each, Cu, Mn,
Furthermore, by containing one or more of Mg, Cr, and Zr within the above range,
This alloy has strength equal to or higher than JIS3003 and exhibits far superior pitting corrosion resistance. In addition, this alloy can be used for automobile air conditioner piping,
In order to obtain piping materials to be joined to Al alloy heat exchangers such as oil coolers and radiators, for example, an Al base metal with a low content of Si and Fe as impurities is used, and Cu, Mn, and even Mg, After adding Cr and Zr elements and melting and casting, and homogenizing the ingot at a temperature of 450 to 600 degrees Celsius for 1 to 20 hours, a raw tube is made by hot extrusion, which is finished to the desired dimensions by continuous drawing. Annealing may be performed if necessary. [Function] The purpose of adding Cu to the alloy of the present invention is to increase pitting corrosion resistance, making general corrosion more likely to occur, increasing strength, and further reducing susceptibility to intergranular corrosion to improve corrosion resistance. The reason why it is limited to 0.25 to 1.0% is that if it is less than 0.25%, the above effects are insufficient, and if it exceeds 1.0%, the above effects will be saturated and self-corrosion will not only increase, but also the extrudability will decrease. . The purpose of adding Mn is to increase strength, and the reason for limiting its content to 0.85 to 1.5% is that if it is less than 0.85%, sufficient strength cannot be obtained, and if it exceeds 1.5%, not only will moldability be impaired, Increases intergranular corrosion,
This is because it reduces pitting corrosion resistance. In addition, we have reduced the content of Si, which is an impurity, to 0.2% or less, Fe
The reason why the content is restricted to 0.2% or less is that all of these elements act as starting points for corrosion and reduce pitting corrosion resistance.If they are contained in excess of this, susceptibility to intergranular corrosion increases significantly and pitting corrosion resistance deteriorates. This is to reduce the Furthermore, the purpose of adding one or more of Mg, Cr, and Zr to the Al alloy having the above composition is to further improve pitting corrosion resistance and strength, and the content of each of these elements is The reason why the content is limited to 0.3% or less is that if the content exceeds this value, workability in cold drawing processing will be significantly impaired. Note that the addition of a small amount of Ti for grain refinement, which is carried out in general Al alloys, is also effective in the alloy of the present invention, and it is preferable to add Ti within a range of 0.15% or less, if necessary. In addition, unavoidable impurities are normal impurities contained in normal Al metal,
In the present invention, among these impurities, in particular, the Si content is reduced to 0.2
% or less, and the Fe content is regulated to 0.2% or less. [Example] An alloy having the composition shown in Table 2 was melted and cast by a conventional method, and the ingot was soaked at a temperature of 600°C for 3 hours, and then hot extruded at a temperature of 500°C to form a 50 mm diameter ingot. I made a raw pipe. This was finished by continuous cold drawing to an outer diameter of 12.7 mm and wall thickness of 1.0 mm, and annealed at a temperature of 360°C for 2 hours to manufacture piping for automobile air conditioners. The tensile strength, cold drawing workability, and CASS test (500 hours) based on JIS 8601 were conducted on these materials to examine the maximum pitting depth and the occurrence of intergranular corrosion. These results are shown in Table 3. Regarding cold drawing workability, those that cracked or broke during processing were evaluated as poor workability, and those that did not cause such defects were evaluated as good.

【table】

【table】

〔Effect of the invention〕

The alloy of the present invention has tensile strength and workability equal to or higher than conventional alloys, and has far superior corrosion resistance, and is used in piping for automobile air conditioners and aluminum alloy heat exchangers such as radiators and oil coolers. Improves corrosion resistance, especially pitting corrosion resistance, when used in
This not only increases the service life of pipes, but also makes it possible to make pipes thinner and lighter, which has significant industrial effects.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an automotive air conditioner system. 1...Condenser, 2...Evaporator, 3...
Piping, 4...compressor, 5...receiver.

Claims (1)

[Claims] 1 Contains Cu0.25-1.0wt%, Mn0.85-1.5wt%,
An Al alloy for heat exchanger piping, characterized in that the impurities Si and Fe are each regulated to 0.2 wt% or less, and the remainder consists of Al and other unavoidable impurities. 2 Cu0.25-1.0wt%, Mn0.85-1.5wt%, and further Mg0.3wt% or less, Cr0.3wt% or less, Zr0.3wt%
Contains one or more of the following within the range,
An Al alloy for heat exchanger piping, characterized in that the impurities Si and Fe are each regulated to 0.2 wt% or less, and the remainder consists of Al and other unavoidable impurities.