JP2005089788A - Aluminum alloy piping material for heat exchanger having excellent corrosion resistance, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al alloy piping material for a heat exchanger exhibiting sufficient corrosion resistance even in a severe corrosive environment and to provide a method of manufacturing the material. <P>SOLUTION: The aluminum alloy piping material for a heat exchanger consists, by mass%, of 0.05 to 0.6% Si, 0.05 to 0.7% Fe, 0.04 to 0.7% Cu, 0.6 to 1.0% Mn, 0.01 to 0.15% Mg, 0.1 to 3.0% Zn and the balance Al and inevitable impurities, and has 100 to 150 MPa tensile strength, ≥30% elongation and excellent corrosion resistance. The method for manufacturing the Al alloy piping material for a heat exchanger having excellent corrosion resistance comprises the steps of: subjecting an Al alloy ingot having the above alloy composition to hot extrusion and stretching in this order to obtain a raw pipe; and then subjecting the raw pipe to final annealing at 450 to 550°C for 1 to 10 hours. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aluminum alloy piping material excellent in corrosion resistance suitable for a heat exchanger for automobiles (such as a radiator) and various industrial equipment heat exchangers, and a method for producing the same.

Conventionally, aluminum alloys such as JIS 1000 series, JIS 3000 series, and JIS 6000 series (hereinafter referred to as “Al” as appropriate) have been used for this type of heat exchanger piping material.
For example, Patent Document 1 contains 0.35 to 1.5% Mg, 0.2 to 0.8% Si, 0.1 to 0.3% Zn, and 0.02 to Sn. A JIS6000 series Al alloy containing 0.1% and 0.15 to 0.4% of Cu and having improved balance between intergranular corrosion resistance and pitting corrosion resistance is disclosed.

Japanese Examined Patent Publication No. 61-36577

However, the conventional Al alloy does not have sufficient corrosion resistance. Therefore, in a severe corrosive environment, a JIS3003 alloy having excellent strength and workability is used as a core, and a JIS7072 alloy having a sacrificial anode effect on one or both sides is combined. However, the clad material has a problem of high manufacturing cost.
Therefore, it has been desired to develop an Al alloy piping material for a heat exchanger that can sufficiently withstand a severe corrosive environment, not a clad material, alone.

  An object of this invention is to provide the Al alloy piping material for heat exchangers which has sufficient corrosion resistance also in a severe corrosive environment, and its manufacturing method.

  In the first aspect of the present invention, Si is 0.05 to 0.6% by mass (hereinafter abbreviated as%), Fe is 0.05 to 0.7%, Cu is 0.04 to 0.2%, and Mn is An aluminum alloy piping material containing 0.6 to 1.0%, Mg of 0.01 to 0.15%, Zn of 0.1 to 3.0%, the balance being Al and inevitable impurities, wherein the piping An aluminum alloy piping material for heat exchangers having excellent corrosion resistance, characterized in that the tensile strength of the material is 100 to 150 MPa and the elongation is 30% or more.

  The invention according to claim 2 is that 0.05 to 0.6% of Si, 0.05 to 0.7% of Fe, 0.04 to 0.2% of Cu, and 0.6 to 1.0% of Mn , Subjecting an Al alloy ingot containing 0.01 to 0.15% Mg and 0.1 to 3.0% Zn to the balance and Al and inevitable impurities to hot extrusion and drawing in this order And then subjecting the raw pipe to a final annealing treatment at 450 to 550 ° C. for 1 to 10 hours, which is a method for producing an aluminum alloy piping material for heat exchangers having excellent corrosion resistance.

The present invention has the following effects.
The Al alloy piping material of the present invention is excellent in mechanical properties, bending workability, manufacturing workability, terminal workability, has corrosion resistance that can withstand severe corrosive environment, and is inexpensive because it is a simple substance. Useful for heat exchangers. Moreover, the Al alloy piping material of the present invention can be easily manufactured by subjecting a base pipe manufactured by a conventional method to a final annealing treatment under predetermined conditions.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  The present invention is an Al alloy piping material for heat exchangers containing appropriate amounts of Si, Fe, Cu, Mn, Mg, Zn, and improves the mechanical properties by the action of the Si, Fe, Cu, Mn, and Mg. And corrosion resistance is enhanced by the action of Zn.

  JP-A-63-79936 discloses a high-strength Al alloy plate in which Cu is added to make the natural potential noble and thus improve electrolytic corrosion with the iron member. The Al alloy plate does not improve the corrosion resistance of the material itself as in the present invention, and is used for packaging and is different from the present invention.

The alloy elements of the Al alloy piping material of the present invention will be described below.
Si forms an intermetallic compound with Mg and contributes to strength improvement.
If the Si content is less than 0.05%, the effect cannot be obtained sufficiently, and if it exceeds 0.6%, work hardening becomes large, so many intermediate annealings are required during the drawing process, and productivity is reduced. Inferior. Therefore, the Si content is specified to be 0.05 to 0.6%. A more preferable content is 0.1 to 0.4%.

Fe contributes to improving the strength by dissolving in an Al matrix or by depositing an Al—Fe—Mn intermetallic compound.
If the Fe content is less than 0.05%, the effect cannot be sufficiently obtained. If the Fe content exceeds 0.7%, the Al-Fe intermetallic compound increases and the corrosion resistance decreases, and the intermetallic compound is molded. This is because it becomes a starting point of cracking during processing and terminal processability is lowered. Therefore, the Fe content is specified to be 0.05 to 0.7%. A more preferable content is 0.05 to 0.4%.

Cu dissolves in the Al matrix and contributes to improving the strength, and also suppresses the coarsening of crystal grains when the pipe material is brazed at a high temperature to maintain the terminal processability at a high level.
If the Cu content is less than 0.04%, the effect cannot be sufficiently obtained, and if it exceeds 0.2%, the compound is precipitated and the corrosion resistance is lowered. Therefore, the content is specified to 0.04 to 0.2%. A more preferable content is 0.05 to 0.15%.

Mn dissolves in the Al matrix and contributes to improvement in strength and corrosion resistance.
If the Mn content is less than 0.6%, the effect cannot be sufficiently obtained, and if it exceeds 1.0%, the production processability and the moldability are deteriorated. Therefore, the Mn content is specified to be 0.6 to 1.0%. A more preferable content is 0.6 to 0.8%.

  Mg is dissolved in the Al matrix and forms an intermetallic compound with Si, thereby contributing to strength improvement. If the content is less than 0.01%, the effect cannot be sufficiently obtained. If the content exceeds 0.15%, hot extrudability and terminal processability are deteriorated, and when a fluorine-based non-corrosive flux is used. Brazing property decreases. Accordingly, the Mg content is specified to be 0.01 to 0.15%. A more preferable content is 0.02 to 0.1%.

  Zn forms a solid solution in the Al matrix and reduces the potential difference between the crystal grain boundaries and the crystal grains, thereby suppressing intergranular corrosion. If the content is less than 0.1%, the effect cannot be sufficiently obtained, and if it exceeds 3.0%, the corrosion resistance is lowered. Therefore, the Zn content is specified to be 0.1 to 3.0%. A more preferable content is 0.2 to 1.0%.

  In the present invention, the reason that the tensile strength is 100 to 150 MPa and the elongation is 30% or more is that if the tensile strength is less than 100 MPa, the terminal processability is lowered, and the tensile strength exceeds 150 MPa or the elongation is increased. If it is less than 30%, the bending workability is lowered and it is difficult to assemble the Al alloy piping material to the heat exchanger.

The Al alloy piping material of the present invention can be manufactured by subjecting a raw pipe processed by an arbitrary method to a predetermined final annealing treatment.
In the present invention, the reason for performing the final annealing treatment on the raw pipe is to appropriately control the mechanical properties of the Al alloy piping material by performing the final annealing treatment, thereby improving the bending workability and the terminal workability. This is to facilitate the assembly to the heat exchanger.

  The reason for prescribing the final annealing treatment condition at 450 to 550 ° C. for 1 to 10 hours is that even if the final annealing treatment temperature is less than 450 ° C. and the annealing treatment time is less than 1 hour, the tensile strength exceeds 150 MPa, or This is because the elongation is less than 30%, and as a result, the bending workability is lowered and it is difficult to assemble the piping material to the heat exchanger. Moreover, it is also because the amount of solid solution of Mn decreases and corrosion resistance falls. On the other hand, when the heat treatment temperature exceeds 550 ° C., the strength decreases to less than 100 MPa, cracking occurs during terminal processing, fatigue failure occurs due to vibration of the engine or compressor, and the annealing treatment time exceeds 10 hours. This is because the effect is saturated and uneconomical.

Hereinafter, the present invention will be described in detail with reference to examples.
(Example 1)
An Al 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. The ingot is subjected to homogenization treatment at 610 ° C. for 4 hours, and then cut into a length of 1000 mm and extruded billet This was heated to 510 to 540 ° C. and hot-extruded into a hollow material having an outer diameter of 47 mm. Subsequently, the hollow material was subjected to continuous drawing multiple times at room temperature to give an outer shape of 8.0 mm and a thickness of 1. A 0 mm blank was made, and this blank was subjected to a final annealing treatment at 500 ° C. for 2 hours, and then allowed to cool to produce an Al alloy piping material.

About the obtained Al alloy piping material, (1) corrosion resistance, (2) manufacturing workability, (3) mechanical properties, (4) bending workability, and (5) terminal workability were investigated by the following methods. ,evaluated.
(1) Corrosion resistance: Connect the piping material to a commercially available circulation test device, hold a temperature test at 88 ° C for 8 hours, and then hold a 16-hour cycle test at room temperature for 1 year. After removing, the depth of pitting was measured by the depth of focus method using an optical microscope.
When the maximum depth of the pitting corrosion was 0.5 mm or less, the corrosion resistance was good, and when it was 0.5 mm or more (including penetration), it was evaluated as defective.

(2) Manufacturing processability: The maximum extrusion speed when the hollow material was hot-extruded at a constant extrusion pressure was measured, and the occurrence of cracks and fractures in the drawing process was observed.
When the maximum extrusion speed was not less than the specified value (60 m / min) and no cracks or breaks occurred during drawing, it was evaluated that the manufacturing processability was excellent, and otherwise, the manufacturing processability was inferior.
(3) Mechanical properties: Tensile strength and elongation were measured according to JIS Z 2201. Those satisfying a tensile strength of 100 to 150 MPa and an elongation of 30% or more were evaluated as good, and the others were evaluated as defective.

(4) Bending workability: A tensile bending (stretch bend) test is performed under the conditions of a bending radius of 30 mmφ and a bending angle of 60 degrees. If there is no abnormality in the bent part, the bending workability is good. Rated as bad.
(5) Terminal processability: The shaft seal bead processing portion 1 shown in FIG. 1 is formed by combining tube expansion, punching and rolling, and the shaft seal bead processing portion 1 is cracked, wrinkled, or microcracked. If not, the terminal processability was good, and if it occurred, it was evaluated as bad.

(Example 2)
An Al alloy pipe was manufactured by the same method as in Example 1 except that the final annealing treatment conditions were changed, and the characteristics were investigated and evaluated by the same method as in Example 1.

(Comparative Example 1)
An Al alloy piping material was produced by the same method as in Example 1 except that an Al alloy having a composition outside the scope of the present invention shown in Table 1 was used, and the characteristics were investigated and evaluated by the same method as in Example 1.

(Comparative Example 2)
An Al alloy piping material was manufactured by the same method as in Example 1 except that a conventional Al alloy was used, and the characteristics were investigated and evaluated by the same method as in Example 1.

(Comparative Example 3)
An Al alloy pipe was manufactured by the same method as in Example 1 except that JIS 3003 alloy was used, and the characteristics were investigated and evaluated by the same method as in Example 1.
The results of Examples 1 and 2 and Comparative Examples 1 to 3 are also shown in Table 1.

As is clear from Table 1, the piping material of the present invention was excellent in all of corrosion resistance (pitting corrosion), manufacturing processability, mechanical properties, bending workability, and end workability.
On the other hand, the comparative example 1 No. Nos. 13 to 21 were inferior in any of the above characteristics because the alloy composition was outside the specified value of the present invention.
That is, no. No. 13 was inferior in manufacturing processability and corrosion resistance due to a large amount of Si. No. No. 14 was inferior in corrosion resistance and terminal processability due to the large amount of Fe. No. No. 15 was inferior in tensile strength and terminal processability due to a small amount of Cu. No. No. 16 was inferior in corrosion resistance due to a large amount of Cu. No. No. 17 had poor tensile strength and corrosion resistance due to low Mn. No. No. 18 was inferior in manufacturing processability and terminal processability because of a large amount of Mn. No. No. 19 was inferior in tensile strength, manufacturing processability and terminal processability due to a large amount of Mg. No. No. 20 is low in Zn, so No. No. 21 was inferior in corrosion resistance because of the large amount of Zn.

No. of Comparative Example 2 No. 22 has a low final annealing temperature. No. 23 was inferior in bending workability and corrosion resistance because the final annealing treatment time was short. No. No. 24 was inferior in mechanical properties and terminal workability because the final annealing temperature was high.
No. of Comparative Example 3 25 (conventional material) was inferior in corrosion resistance.

It is explanatory drawing of the shaft seal bead processing part for evaluating terminal workability.

Explanation of symbols

1 shaft seal bead processing section

Claims (2)

  0.05 to 0.6% by mass of Si (hereinafter abbreviated as%), 0.05 to 0.7% of Fe, 0.04 to 0.2% of Cu, and 0.6 to 1.0 of Mn %, Mg is 0.01 to 0.15%, Zn is 0.1 to 3.0%, the balance is aluminum alloy piping material made of Al and inevitable impurities, and the tensile strength of the piping material is 100 An aluminum alloy piping material for heat exchangers having excellent corrosion resistance, characterized by being ~ 150 MPa and elongation of 30% or more.   0.05 to 0.6% Si, 0.05 to 0.7% Fe, 0.04 to 0.2% Cu, 0.6 to 1.0% Mn, 0.01 to Mg An aluminum alloy ingot containing 0.15% and Zn 0.1 to 3.0% and the balance being Al and inevitable impurities is subjected to hot extrusion and drawing in this order to form a raw pipe, The manufacturing method of the aluminum alloy piping material for heat exchangers which is excellent in corrosion resistance characterized by performing the final annealing process for 1 to 10 hours at 450-550 degreeC.

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