WO2015111182A1

WO2015111182A1 - Aluminum alloy sheet for heat exchanger fin

Info

Publication number: WO2015111182A1
Application number: PCT/JP2014/051474
Authority: WO
Inventors: 好生佐藤
Original assignee: 株式会社Uacj
Priority date: 2014-01-24
Filing date: 2014-01-24
Publication date: 2015-07-30

Abstract

Provided is an aluminum alloy sheet for a heat exchanger fin. Under corrosive conditions, the aluminum alloy sheet promotes the preferential corrosion of an aluminum alloy plate-fin material even when the plate-fin material is used in combination with aluminum alloy refrigerant pipes. With regard to collar moldability, the aluminum alloy sheet has particularly improved draw moldability and stretch formability. An aluminum alloy sheet for a fin that is used in a plate-fin heat exchanger wherein fins have collared holes formed therein and aluminum alloy refrigerant flow pipes are inserted into the collared holes, and wherein the outer walls of the refrigerant flow tubes adhere to the inner surfaces of the collars. The composition of the aluminum alloy sheet comprises 0.3%-1.3% Zn and 0.4%-1.0% Fe, the remainder being Al and unavoidable impurities.

Description

Aluminum alloy plate for heat exchanger fins

The present invention relates to a heat exchanger, and in particular, to an aluminum alloy plate used as a fin material of a plate fin type aluminum alloy heat exchanger in which an aluminum alloy refrigerant circulation pipe is inserted into an aluminum alloy fin.

General heat exchanger structures widely used include plate fin type and corrugated fin type. The plate fin type is frequently used for heat exchangers for home or commercial air conditioners, and the corrugated fin type is often used for heat exchangers for automotive air conditioners.

In the fin material (hereinafter referred to as plate fin material) of the former plate fin type heat exchanger, a hole for inserting a pipe (hereinafter referred to as a refrigerant distribution pipe) through which the heat exchange refrigerant flows is formed, and It is necessary to form a collar for raising the inner peripheral edge portion and closely contacting the outer wall of the refrigerant flow pipe. Conventionally, such plate fin materials are generally drawn (drawn) and then punched, expanded, etc. The so-called draw method combined with overhanging and ironing. Is formed by.

The components and tempering of the plate fin material include pure aluminum-based 1100 alloy O material and H22 material, 1050 alloy O material and H22 material, and further Al-0.2 to 0.6% Mn alloy H22. Materials and H26 materials are widely used. As for the conventional plate fin material by drawing, 1100 alloy or 1050 alloy O material or H22 material having better color formability is used from the viewpoint of emphasizing ductility. When applying drawless molding, strength that can withstand ironing is required, so it is common to use H22 or H26 material of Al-0.1 to 0.5% Mn alloy. .

On the other hand, copper pipes made of pure copper materials such as phosphorous deoxidized copper have been used for a long time from the viewpoint of thermal conductivity as refrigerant flow pipes inserted into plate fin materials, but the price of copper is higher than aluminum materials In addition, since the weight per unit weight is large, in order to meet the demand for light weight and downsizing, a heat exchanger in which aluminum alloy pipes are recently applied to refrigerant flow pipes, that is, aluminum alloys in which all members are made of aluminum alloys. Heat exchangers are becoming popular.

The aluminum alloy refrigerant flow tube is manufactured by extrusion, and the material of the aluminum alloy refrigerant flow tube is a non-heat-treatable alloy such as a 1000 series alloy such as 1050 alloy or 1100 alloy, or a 3000 series such as 3003 alloy or 3004 alloy. An alloy, a 5000 series alloy such as a 5005 alloy or a 5052 alloy is applied, and a 6000 series alloy such as a 6N01 alloy or a 6063 alloy is applied as the heat treatment type alloy.

JP-A-9-176805 JP 2005-264289 A JP-A-9-176805 JP 2005-264289 A JP 2005-264289 A

In the combination of copper refrigerant flow pipe and aluminum alloy plate fin material, aluminum is more electrically base than copper, so aluminum is preferred in the corrosive environment of heat exchangers. However, in the combination of the aluminum alloy refrigerant flow pipe and the aluminum plate fin material, the electrical difference between the two is small. The fin material does not corrode preferentially, and the refrigerant flow pipe may corrode and the refrigerant may leak.

Therefore, it is conceivable to use Al—Zn-based 7000 series alloy, which is the most electrically base alloy among aluminum alloys, for the fin material. Although 7072 alloy which can be cold-rolled to the plate thickness of the plate fin material represented by 0.1 mm with low strength is mentioned, 7072 alloy has a problem that color formability is insufficient.

The present invention has been made as a result of repeated testing and examination based on 7072 alloy in order to eliminate the above-mentioned problems, and its purpose is to make a refrigerant flow tube made of aluminum alloy and aluminum alloy. Even if it is a combination of plate fin materials, by making the fin material side an electrically base composition, the fin materials are preferentially corroded in a corrosive environment, and in particular, the color moldability is drawn. An object of the present invention is to provide an aluminum alloy plate for a heat exchanger fin that has improved properties and stretchability.

In order to achieve the above object, an aluminum alloy plate for heat exchanger fins according to claim 1 is configured such that an aluminum alloy refrigerant flow pipe is inserted into a hole with a collar of a fin in which a hole with a collar is formed. An aluminum alloy plate for fins used in a plate fin type heat exchanger of the type in which the outer wall of the tube is closely attached to the inner surface of the collar, Zn: 0.3% (mass%, the same applies hereinafter) to 1.3%, Fe: 0.4% or more and 1.0% or less, with the balance being composed of Al and inevitable impurities.

An aluminum alloy plate for heat exchanger fins according to claim 2 is the aluminum alloy plate according to claim 1, wherein the aluminum alloy plate has an Erichsen value determined by an Ericksen test according to JIS Z2247 at a tensile speed of 20 mm / min according to JIS Z2241. In the region of tensile strength of 115 to 145 MPa determined by a tensile test using JIS No. 5 test piece, the thickness is 7 to 9 mm.

According to the present invention, even in a combination of an aluminum alloy refrigerant distribution pipe and an aluminum alloy plate fin material, the fin material can be used even in a corrosive environment by making the fin material side electrically base composition. Provided is an aluminum alloy plate for a heat exchanger fin that is preferentially corroded and has improved drawability and stretchability among color formability.

The significance of the alloy component of the aluminum alloy plate for heat exchanger fins of the present invention and the reason for the limitation will be described.
Zn:
Zn is an alloy component that functions to make the plate fin material electrically base, and the preferable content of Zn is in the range of 0.3% to 1.3%. If Zn is less than 0.3%, it is less likely to be electrically lower than the aluminum alloy refrigerant flow pipe made of 1000 series, 3000 series, 5000 series, and 6000 series alloys, and has the effect of preferentially corroding the plate fin material. It is hard to get. If it exceeds 1.3%, a coarse Al—Zn-based intermetallic compound is likely to be formed, which becomes a starting point of cracking during color molding and deteriorates moldability. The more preferable content range of Zn is 0.5% or more and 1.3% or less, and the more preferable content range of Zn is 0.8% or more and 1.3% or less.

Fe:
Fe is an alloy component that functions to improve the color formability, and the preferable content of Fe is in the range of 0.4% to 1.0%. If Fe is less than 0.4%, the dispersion of fine Al—Fe intermetallic compounds is small and the effect of improving color moldability is insufficient. If it exceeds 1.0%, coarse Al—Fe intermetallic compounds are present. This is a starting point of cracking during color molding and deteriorates moldability. The more preferable content of Fe is in the range of more than 0.7% and 1.0% or less. By containing Fe in this range, a more remarkable moldability improvement effect can be obtained.

The balance consists of inevitable impurities and Al, but Ti: 0.005 to 0.05%, more preferably 0.01 to 0.03% can be added for refining the ingot structure. : 5 to 300 ppm, more preferably 10 to 100 ppm can be added. As for Si, it may combine with Al and Fe to form an Al—Fe—Si intermetallic alloy and hinder color moldability. Therefore, the purity of the metal used is increased, and Si is 0.1%. In the following, it is more preferable to limit the content to 0.03 to 0.08%. If a high-purity metal is used, the manufacturing cost increases, so it is not preferable to make Si less than 0.03%.

In the present invention, the aluminum alloy plate according to the present invention is an tensile test using a JIS No. 5 test piece at a tensile speed of 20 mm / min in accordance with JIS Z2241, in which the Erichsen value determined in accordance with JIS Z2247 is determined. The required tensile strength is 115 to 145 MPa, and it is 7 to 9 mm.

If the Erichsen value is less than 7 mm, cracking is likely to occur during drawing and overhanging during color molding, and if it exceeds 9 mm, it is advantageous for color molding, but the tensile strength decreases, and it is used as a plate fin material. It becomes difficult to ensure a tensile strength of 120 MPa or more.

If the tensile strength is less than 115 MPa, the strength as a plate fin material is too low, and the fin tends to bend or bend during handling, and if it exceeds 145 MPa, it is difficult to secure an Erichsen value of 7 mm or more. Since the value is low, cracks are likely to occur during drawing and overhanging during color molding.

In the present invention, an Erichsen value of 7 mm to 9 mm can be ensured by setting the Zn content and the Fe content in the above ranges and adjusting the final annealing conditions to have a tensile strength of 115 MPa to 145 MPa.

The following describes a preferred method for producing an aluminum alloy plate for heat exchanger fins according to the present invention. An aluminum alloy having the above specific composition is melted and ingot-formed by semi-continuous casting, and the surface layer of the resulting ingot is uneven. After chamfering one layer, a homogenization heat treatment is performed at a temperature of 450 to 550 ° C. for 3 to 12 hours. After that, without cooling to room temperature or after cooling to or near room temperature, reheating is performed. Hot rolling is performed.

Hot rolling is industrially performed by a combination of hot rough rolling of reverse rolling and hot finish rolling which is rolled up in one direction by 3 or 4 stands in succession following hot rough rolling. The hot rough rolling is preferably finished at 420 to 520 ° C., and the hot finish rolling is preferably finished at 250 to 300 ° C. The hot finish rolling finished plate thickness is 1.5 to 2.5 mm.

Then, cold rolling is performed to a plate thickness of 0.08 to 0.12 mm, which is a plate thickness equivalent to a plate fin material, with a reduction rate of 90% or more. In addition, intermediate annealing may be performed by a continuous annealing furnace or a batch furnace for forming recrystallized grains before or during cold rolling, and when intermediate annealing is performed, cooling with uniform mechanical properties over the entire width and length is possible. An intermediate-rolled sheet can be obtained, but if manufacturing condition management such as temperature management and speed management in hot rolling is sufficiently performed, there is no need to dare to perform intermediate annealing that requires manufacturing costs. Finally, the cold-rolled sheet having the final thickness is subjected to final annealing so as to have a tensile strength of 115 to 145 MPa. Usually, the final annealing is performed in a batch furnace.

Hereinafter, examples of the present invention will be described in comparison with comparative examples to demonstrate the effects of the present invention. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Example 1 and Comparative Example 1
An ingot (500 mm width) of an aluminum alloy having the composition shown in Table 1 was ingoted by semi-continuous casting, and after rolling the front and back rolling surfaces by 10 mm, homogenization treatment was performed at 520 ° C. for 8 hours, Hot rough rolling was performed without forced cooling. The hot rough rolling end temperature was 480 ° C., and the hot rough rolling end plate thickness was 32 mm. Subsequently, hot finish rolling was performed to a final plate thickness of 2 mm using a hot finish rolling mill consisting of 4 stands. End temperature was 280 ° C. in hot finish rolling. In Table 1, those outside the conditions of the present invention are underlined.

The obtained hot-finished rolled sheet was cold-rolled (rolling rate 95%) without intermediate annealing to a final sheet thickness of 0.1 mm, and the cold-rolled sheet was finally annealed. The final annealing was performed using a batch furnace, and the final annealing conditions were changed according to the alloy components so that the tensile strength was 115 to 145 MPa. Table 2 shows the final annealing conditions.

Using the obtained final annealed plate as a test material (Example: Test materials 1 to 7, Comparative example: Test materials 8 to 10), a tensile test and an Erichsen test were performed by the following methods. The results are shown in Tables 3 and 4.
Tensile test: compliant with JIS Z2241. As the tensile test piece, a JIS No. 5 test piece of JIS Z2201 was used, and the tensile speed was 20 mm / min.
Eriksen test: compliant with JISZ2247. The test piece was 90 mm wide × 90 mm long.

Moreover, the potential evaluation was performed by the following method. As materials for evaluating the potential, test materials 1 to 5 according to the present invention were tested under conditions where the final annealing condition was the B condition (tensile strength in the 130 MPa range (see Tables 2 and 3)). As comparative materials, JIS A1050 (Fe: 0.3%, Si: 0.1%) H26 material (0.1 mm thickness) (comparative material 1) and JIS A1100 (Fe :), which are generally used as fin materials, are used. 0.8%, Si: 0.07%) H26 material (0.1 mm thickness) (comparative material 2), as a reference material, JIS A7072 (Zn: 1%, Fe: 0.3%) based on the present invention. , Si: 0.1%) H26 material (0.1 mm thickness) was used. Furthermore, for potential difference evaluation, JIS A3003 (Mn: 1.2%, Cu: 0.12%, Fe: 0.5%, Si: 0.3%) O material generally used as a refrigerant flow pipe ( 0.5 mm thickness) was used.

The test material was cut into 15 mm width × 70 mm length, and masked with a room temperature dry paint, leaving the upper end and the 10 mm × 10 mm measurement part to obtain a measurement sample. A measurement sample and a reference electrode (saturated calomel electrode) are immersed in a solution at room temperature (25 ° C.) adjusted to pH = 3 by adding acetic acid to a 5% NaCl solution, and the potential difference between the two is measured using an electrometer. The immersion potential was measured. The results are shown in Table 5.

As shown in Tables 3 and 4, all of the test materials 1 to 7 according to the present invention have a tensile strength of 115 to 145 MPa and an Erichsen value of 7 to 9 mm in the region of the tensile strength of 115 to 145 MPa. It was confirmed that the actual color molding had excellent drawability and stretchability.

On the other hand, since the test material 8 has a small amount of Fe, the test material 9 has a large amount of Fe, and the test material 10 has a large amount of Zn, the Erichsen value is less than 7 mm in the region where the tensile strength is 115 to 145 MPa. Cracks occurred in drawing and stretch forming during actual color molding.

Further, as shown in Table 5, the test materials 1 to 7 and the reference material according to the present invention have a lower potential than the evaluation material, and the potential difference between them is as large as around 150 mV, so that the fin collar closely contacting the refrigerant flow pipe In the part, it was confirmed that the fin side corrodes preferentially.

On the other hand, although the comparative material 1 and the comparative material 2 which are conventional materials are both lower in potential than the evaluation material, the difference between the two is as small as 50 mV or less, so the fin side does not necessarily corrode and the refrigerant flow pipe corrodes. It was confirmed that the refrigerant could leak.

Claims

Fin used in a plate fin type heat exchanger of a type in which an aluminum alloy refrigerant flow pipe is inserted into a collar hole of a fin having a collar hole and the outer wall of the refrigerant flow pipe is in close contact with the inner surface of the collar Aluminum alloy plate for use, containing Zn: 0.3% (mass%, the same shall apply hereinafter) to 1.3%, Fe: 0.4% to 1.0%, the balance being Al and inevitable An aluminum alloy plate for heat exchanger fins, characterized by having a composition comprising impurities.
The Erichsen value determined by the Erichsen test in accordance with JIS Z2247 of the aluminum alloy plate is a tensile strength of 115 to 145 MPa determined by a tensile test using a JIS No. 5 test piece at a tensile speed of 20 mm / min according to JIS Z2241. The aluminum alloy plate for heat exchanger fins according to claim 1, wherein the thickness is 7 to 9 mm.