JP2001342531A - Aluminum alloy piping material for heat exchanger and method for producing the same - Google Patents

Abstract

(57) [Summary] [Problem] As a single-layer bare material, not a clad material,
An object of the present invention is to obtain an aluminum alloy piping material for a heat exchanger for an automobile, which has excellent workability in manufacturing and excellent corrosion resistance and bending workability. SOLUTION: Cu exceeding 0.1 wt% and 0.5 wt% or less, Mn exceeding 0.6 wt% and 0.85 wt% or less,
Contains more than 0.1 wt% and less than 0.3 wt% Cr,
0.2 wt% or less of Si as an unavoidable impurity, Fe
Is restricted to 0.6 wt% or less, with the balance being Al and unavoidable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy piping material having excellent corrosion resistance and good workability suitable for piping of a heat exchanger such as an air conditioner for automobiles, an oil cooler, and a radiator.

[0002]

2. Description of the Related Art For example, as shown in FIG. 1, in an air conditioner for an automobile, a condenser 1 made of an aluminum alloy heat exchanger and an evaporator 2 are connected by an aluminum pipe 3, and a CFC between them. The compressor 4 or the receiver 5 for compressing the refrigerant as described above is provided. The aluminum pipe 3 is made of JIS3003 (Al-Mn-based) alloy or J
An IS1100 (pure Al-based) alloy and a JIS 6000-based alloy (Al-Mg-Si-based) are extruded into a base tube, and the base tube is continuously drawn to form an outer diameter of 8 to 16 mm (wall thickness of 1 to 2).
mm), and a piping material having an outer diameter of about 8 to 34 mm of the above-mentioned alloy is also used for the entrance of a radiator or the like. For example, in JIS 6000 series alloy,
JP-A-58-110655 discloses that Mg is contained in an amount of 0.35.
-1.5 wt%, 0.2-0.8 wt% of Si, 0.1-0.3 wt% of Zn, and 0.02-
An aluminum alloy excellent in grain boundary corrosion resistance and pitting corrosion resistance characterized by containing 0.1 wt% and 0.15 to 0.4 wt% of Cu has been proposed. However, when the piping is used in an engine room of an automobile with poor environmental conditions, or when used in a hot and humid environment such as Southeast Asia, penetration corrosion may occur. If this occurs, the refrigerant (cooling water) in the piping leaks, the cooling function is lost in the air conditioner, and the engine burns in the radiator. For this reason, among the conventional methods for preventing corrosion, the method of cladding an Al-Zn alloy on the outer surface of the pipe is the most effective, but the production is troublesome and the cost is unavoidable. Further, although the coating method is simple and low-cost, it is not possible to obtain a sufficient effect, and even recently, there is a tendency that even coating is omitted from the demand for cost reduction. In addition, rust prevention material (inhibitor) is used for refrigerant and cooling water flowing in the piping.
, Corrosion from the inside of the pipe hardly occurs, and the corrosion mainly proceeds from the outside of the pipe. for that reason,
There has been a need for the development of a single-layer material having better corrosion resistance than conventional alloys without cladding or painting. Needless to say, the pipe material is required to have good formability and workability from the viewpoint of extrusion processing when manufacturing it and bending processing when assembling the heat exchanger. However, conventional piping materials are not necessarily sufficient in that they have all of these corrosion resistance, moldability and workability.

[0003]

The above objects of the present invention have been attained by the following means. That is, the present invention
(1) Cu of more than 0.1 wt% and 0.5 wt% or less,
Mn with a content exceeding 0.6 wt% and not more than 0.85 wt%, 0.1
Cr containing more than 0.3% by weight and more than 0.3% by weight.
Aluminum alloy piping material for heat exchangers characterized by being restricted to 6 wt% or less, with the balance being Al and inevitable impurities; and (2) Cu having a content of more than 0.1 wt% and 0.5 wt% or less, 0.6 wt% % And not more than 0.85 wt% M
n, containing more than 0.1 wt% of Cr and not more than 0.3 wt%, and containing 0.2 wt% or less of Si as an unavoidable impurity;
In manufacturing an aluminum alloy piping material for a heat exchanger, the content of Fe is controlled to 0.6 wt% or less, and the balance is made up of Al and inevitable impurities.
Over 1 ℃, heated at a temperature of 450 ℃ or less for 1 to 10 hours,
An object of the present invention is to provide a method for manufacturing an aluminum alloy piping material, wherein the cooling is performed at a cooling rate of 100 ° C./hour or more.

[0004]

BEST MODE FOR CARRYING OUT THE INVENTION The alloy elements of the aluminum alloy piping material of the present invention will be described below. Cu: Cu promotes surface corrosion to suppress the occurrence of pitting corrosion, and also reduces the intergranular corrosion sensitivity to improve corrosion resistance. It also contributes to the improvement of strength. When the Cu content exceeds 0.1 wt%
If the content is less than 0.1% by weight, the effect cannot be sufficiently obtained. If the content is more than 0.5% by weight, deterioration of self-corrosion is promoted and extrusion workability is impaired. The content of Cu is preferably 0.1 to 0.3 wt%. Mn; Mn combines with Fe to form Al ₆ (MnFe)
A compound is generated, thereby reducing the precipitation of a compound such as Al ₃ Fe or Al ₆ Fe that serves as a starting point of pitting corrosion as a cathode, thereby reducing the starting point of pitting. The reason for specifying the Mn content to be more than 0.6 wt% and 0.85 wt% or less is that if it is less than 0.6 wt%, its effect and mechanical strength are insufficient. This is because the sex is impaired. The content of Mn is preferably 0.6 to 0.8 wt%. Cr; Cr improves pitting corrosion resistance and strength. 0.1% Cr content
The reason why the amount is specified to be more than 0.3 wt% or more than 0.
If the content is less than 1 wt%, the effect cannot be sufficiently obtained.
If the content exceeds t%, a coarse compound is crystallized, and the formability such as cold drawing workability and extrusion workability of a product is deteriorated. The content of Cr is preferably 0.1 to 0.2 wt.
%. In the present invention, the inevitable impurity Si is 0.2 wt.
% Or less, and Fe is specified to be 0.6 wt% or less. The reason for this is that pitting corrosion is likely to occur even in any case exceeding the examples of the present invention. The content of Si is preferably 0.1 wt% or less, and the content of Fe is preferably 0.5 wt% or less. It is preferable to add a small amount of Ti to the alloy of the present invention in a range of 0.15 wt% or less for the purpose of refining the casting structure and improving product workability. If the content exceeds 0.15 wt%, a coarse compound of Ti is generated, and the moldability is reduced. The manufacturing process of the piping material of the present invention can be performed according to a conventional method. This is exemplified as follows. Melting casting of aluminum alloy → Homogenization treatment → Hot extrusion → Continuous drawing → Annealing Next, in the present invention, the annealing treatment exceeds 330 ° C.
Heat at a temperature of 50 ° C or less for 1 to 10 hours, and cool at a rate of 1
The reason for the method for producing an aluminum alloy piping material, which is performed at a temperature of 00 ° C./hour or more, will be described.
If the heat treatment temperature is lower than 330 ° C., the elongation of the material is reduced, and the formability such as bending workability is deteriorated.
If the annealing temperature exceeds 450 ° C., Al—Mn-based precipitates are preferentially precipitated at the grain boundaries, promoting intergranular corrosion and impairing corrosion resistance. Further, when the cooling rate is less than 100 ° C./hour, the precipitation of Al—Mn system precipitated at the grain boundary is promoted, the grain boundary corrosion is promoted, and the corrosion resistance is impaired.

[0005]

Next, the present invention will be described in more detail with reference to examples. (1) Aluminum alloy pipe material An aluminum alloy having the composition specified in the present invention shown in Table 1 is melt-cast to form an ingot having a circular cross section, and the ingot is homogenized at 610 ° C. for 4 hours and then cut into a length of 1000 mm. The extruded billet was heated again to 500 ° C., and was hot-extruded into a 50 mm-diameter base tube. Thereafter, continuous drawing was performed a plurality of times in the cold to obtain an outer diameter of 8.0 mm and a wall thickness of 1 mm. .0
mm, and the tube was annealed at 360 ° C. for 2 hours to produce a pipe for an automotive air conditioner. Further, comparative example alloys and conventional alloys deviating from the scope of the present invention shown in Table 1 were produced in the same manner as the alloys of the present invention, and piping materials for automotive air conditioners were produced. After performing a CASS test based on JIS H8601 for 400 hours on this test piece, corrosion products were removed, and the pit depth was measured using an optical microscope to determine the maximum pit depth. Also,
Extrusion workability during the production of this tube material was evaluated by comprehensively judging whether the extrusion force and the extrusion speed at the time of extrusion and a sufficient shape were obtained, and evaluated as good and poor. The bending workability was evaluated on the tube after drawing and annealing by a tensile bending (stretch bend) method used in actual bending. The bending conditions were a bending radius of 30 mmΦ and a bending angle of 60 °. A tube without any abnormality after bending was judged as good, and a tube with broken or rough skin was judged as bad. Table 1 shows the results. As can be seen from Table 1, the piping material using the aluminum alloy of the present invention has better corrosion resistance, extrusion workability, and bending workability than the comparative example and the conventional example, and is excellent.

[0006]

[Table 1]

(2) Manufacturing method of aluminum alloy piping material An aluminum alloy having the composition of the present invention shown in Table 2 and a comparative alloy which does not contain the components of the present invention are melt-cast to form an ingot having a circular cross section. Ingot at 610 ° C 4
After the homogenization treatment for a time, the extruded billet is cut into a length of 1000 mm to obtain an extruded billet, which is reheated to 500 ° C., and is hot-extruded into a base tube having an outer diameter of 50 mm. Go outside diameter 8.0mm, wall thickness 1.0mm
Finished with a tube material. Thereafter, an artificial aging treatment shown in Table 3 was performed, and the test material was cooled at a cooling rate shown in Table 3 to obtain a test piece. These test materials were converted to CA based on JIS8601.
After performing the SS test for 400 hours, the corrosion products were removed, and the pit depth was measured using an optical microscope to determine the maximum pit depth. Extrusion workability during the production of this tube material was evaluated comprehensively by judging whether the extrusion force and extrusion speed at the time of extrusion and a sufficient shape were obtained, and evaluated as good and poor. The bending workability was evaluated on the tube after drawing and annealing by a tensile bending (stretch bend) method used in actual bending. Bending condition is bending radius 30mm
Φ and the bending angle were 60 °. A tube without any abnormality after bending was judged as good, and a tube with broken or rough skin was judged as bad. Table 3
Shows the results. It can be seen that the examples of the present invention have better corrosion resistance, extrusion workability, and bending workability than the comparative examples, and are excellent.

[0008]

[Table 2]

[0009]

[Table 3]

[0010]

As described above, according to the present invention, even if a single-layer bare material is used instead of a clad material as an aluminum alloy piping material for a heat exchanger for an automobile, workability during production and excellent corrosion resistance and A heat exchanger piping material having all of the bending properties can be obtained, and industrially remarkable effects can be obtained, such as reduction in cost of the heat exchanger.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a system of a vehicle air conditioner.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Condenser 2 Evaporator 3 Piping 4 Compressor 5 Receiver

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C22F 1/00 682 C22F 1/00 682 691 691B 691C 692 692A (72) Inventor Yoshiyuki Shibata Chiyoda-ku, Tokyo 2-6-1 Marunouchi Furukawa Electric Co., Ltd. (72) Inventor Satoshi Tanaka 2-6-1 Marunouchi Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (2)

[Claims] 1. An alloy containing Cu exceeding 0.1 wt% and 0.5 wt% or less, Mn containing 0.6 wt% or more and 0.85 wt% or less,
Contains more than 0.1 wt% and less than 0.3 wt% Cr,
0.2 wt% or less of Si as an unavoidable impurity, Fe
Aluminum alloy piping material for heat exchangers, wherein the content is regulated to 0.6 wt% or less, and the balance consists of Al and inevitable impurities. 2. An alloy having a Cu content of more than 0.1 wt% and 0.5 wt% or less, a Mn content of more than 0.6 wt% and 0.85 wt% or less.
Contains more than 0.1 wt% and less than 0.3 wt% Cr,
0.2 wt% or less of Si as an unavoidable impurity, Fe
Is regulated to 0.6 wt% or less, and the balance is made of Al and unavoidable impurities. In producing an aluminum alloy piping material for a heat exchanger, the heat treatment condition is set to a temperature exceeding 330 ° C and a temperature of 450 ° C or less. And a cooling rate of 100 ° C./hour or more.