ALUMINUM ALLOY FIN MATERIAL

Abstract

An aluminum alloy fin material has a composition, in % by mass, of the following: Zr: 0.05 to 0.25%, Mn: 1.3 to 1.8%, Si: 0.7 to 1.3%, Fe: 0.10 to 0.35%, and Zn: 1.2 to 3.0%, the remainder being Al and inevitable impurities. The aluminum alloy fin material has a solidus temperature of 615° C. or higher, a tensile strength after brazing of 135 MPa or higher, a pitting potential after brazing in the range of −900 to −780 mV, and an average crystal grain diameter in a rolled surface after brazing in the range of 200 μm to 1,000 μm.

Claims

1-4. (canceled)

5. An aluminum alloy fin material, wherein the aluminum alloy fin material has a composition, in % by mass, of the following: Zr: 0.05 to 0.25%, Mn: 1.3 to 1.8%, Si: 0.7 to 1.3%, Fe: 0.10 to 0.35%, and Zn: 1.2 to 3.0%, the remainder being Al and inevitable impurities, and wherein the aluminum alloy fin material has a solidus temperature of 615° C. or higher, a tensile strength after brazing of 135 MPa or higher, a pitting potential after brazing in the range of −900 to −780 mV, and an average crystal grain diameter in a rolled surface after brazing in the range of 200 μm to 1,000 μm.

6. The aluminum alloy fin material according to claim 5, further comprising, in % by mass, Cu: 0.03 to 0.10%, as compositional component.

7. The aluminum alloy fin material according to claim 5, wherein among second-phase particles distributed in a matrix thereof after brazing, averages of the contents of Mn, Fe and Si in an Al—Mn—Fe—Si compound 0.5 μm or larger in circle-equivalent diameter satisfy a relation of Fe/(Mn+Si)<0.25 by atomic % in compound.

8. The aluminum alloy fin material according to claim 5, wherein in a raw material before working thereof, second-phase particles distributed in a matrix thereof in the range of 0.05 to 0.4 μm in circle-equivalent diameter are present in the range of 20 to 80 particles/μm.sup.2.

9. The aluminum alloy fin material according to claim 6, wherein among second-phase particles distributed in a matrix thereof after brazing, averages of the contents of Mn, Fe and Si in an Al—Mn—Fe—Si compound 0.5 μm or larger in circle-equivalent diameter satisfy a relation of Fe/(Mn+Si)<0.25 by atomic % in compound.

10. The aluminum alloy fin material according to claim 6, wherein in a raw material before working thereof, second-phase particles distributed in a matrix thereof in the range of 0.05 to 0.4 μm in circle-equivalent diameter are present in the range of 20 to 80 particles/μm.sup.2.

11. The aluminum alloy fin material according to claim 7, wherein in a raw material before working thereof, second-phase particles distributed in a matrix thereof in the range of 0.05 to 0.4 μm in circle-equivalent diameter are present in the range of 20 to 80 particles/μm.sup.2.

12. The aluminum alloy fin material according to claim 9, wherein in a raw material before working thereof, second-phase particles distributed in a matrix thereof in the range of 0.05 to 0.4 μm in circle-equivalent diameter are present in the range of 20 to 80 particles/μm.sup.2.

13. A heat exchanger comprising the aluminum alloy fin material according to claim 5.

Description

BRIEF DESCRIPTION OF DRAWING

[0038] FIG. 1 is a perspective view illustrating a use example of an aluminum alloy fin material according to one embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

[0039] Hereinafter, embodiments of the present invention will be described.

[0040] An ingot regulated to compositional components of the present invention can be produced by a conventional method. It is desirable that the casting rate during the casting time be made to be 0.2 to 10° C./s. Thereby, the Fe/(Mn+Si) can be controlled low by regulating the component ratio in an Al—Mn—Fe—Si compound 0.5 μm or larger in circle-equivalent diameter.

[0041] It is desirable that the ingot is homogenized suitably under the condition of 350 to 480° C.×2 to 15 hours. Thereby, there can be regulated the Fe/(Mn+Si) ratio in the Al—Mn—Fe—Si compound 0.5 μm or larger in circle-equivalent diameter. There can further be provided a raw material in which second-phase particles in the range of 0.05 to 0.4 μm in circle-equivalent diameter are dispersed in 20 to 80 particles/μm.sup.2.

[0042] The raw material can be subjected to hot working and cold working by conventional methods. The conditions can be ones according to the conventional methods.

[0043] The above material, as illustrated in FIG. 1, is provided as aluminum alloy fin materials 1, which are assembled with tubes 2 and headers, and are supplied to brazing as a body to be brazed. The conditions of the brazing are not especially limited in the present invention, but may include, for example, a temperature-rise rate of 40° C./min in average starting from room temperature, a holding temperature of 600° C., a holding time of 3 min, a cooling rate of 100° C./min, and the like. A heat exchanger 10 is provided by the brazing.

[0044] The brazed aluminum alloy fin material has a tensile strength after the brazing of 135 MPa or higher, a pitting potential after the brazing in the range of −900 to −780 mV, and further an average crystal grain diameter in the rolled surface after the brazing in the range of 200 μm to 1,000 μm. The brazed aluminum alloy fin material is superior in strength and corrosion resistance.

EXAMPLE 1

[0045] Hereinafter, the present invention will be described by comparing Examples and Comparative Examples.

[0046] An aluminum alloy having a composition (Al and inevitable impurities as the remainder) indicated in Table 1 was melted and cast by a semi-continuous casting method. Here, the casting rate was 0.6 to 2.5° C./s. A homogenizing treatment was further carried out under the condition indicated in Table 2 on the obtained ingot, and thereafter, hot rolling and cold rolling were carried out.

[0047] In the cold rolling step, the resultant was subjected to a cold rolling of 75% or more, thereafter subjected to an intermediate annealing at 350° C., and thereafter subjected to a final rolling of 40% in rolling ratio to thereby obtain a fin material (test material) of 0.06 mm in plate thickness and H14 in quality.

[0048] The resultant was subjected to brazing-equivalent heating under the heat treatment condition of heating up from room temperature to 600° C. at an average temperature-rise rate of 40° C./min, holding the temperature at 600° C. for 3 min, and then cooling at a temperature-fall rate of 100° C./min. For the fin material after the heating, the following evaluation tests were carried out. The results of the respective tests are shown in Table 2.

(Distribution State of the Compound in the Raw Material)

[0049] For the raw material after the homogenizing treatment, the density of the number of particles (particles/μm.sup.2) of the second-phase particles (dispersed particles) in the range of 0.05 to 0.4 μm in circle-equivalent diameter was measured by a transmission electron microscope (TEM).

[0050] The measurement method involved subjecting the raw material to a salt bath annealing of 400° C.×15 s to remove the deformed strain and make it easy for the compound to be observed, thereafter preparing a thin film by mechanical polishing and electrolytic polishing by conventional methods, and taking photographs thereof in 30,000× by a transmission electron microscope. The photographs were taken for 5 visual fields (about 16 μm.sup.2 in total), and the size and the density of the number of the dispersed particles were measured by using image analysis.

(Strength After Brazing)

[0051] The prepared fin material was subjected to a brazing-equivalent heat treatment. The heat treatment specifically involved heating up to 600° C. at an average temperature-rise rate of 40° C./min, holding the temperature at 600° C. for 3 min, and then cooling at a temperature-fall rate of 100° C./min. Thereafter, a sample was cut out parallel to the rolling direction to thereby prepare a test piece of JIS No. 13 shape-B, which was subjected to a tensile test to measure the tensile strength. The tensile rate was made to be 3 mm/min. The evaluation criteria were according to Table 2. The results are shown as TS after brazing.

(Pitting Potential)

[0052] The pitting potential after brazing was measured by an anodic polarization measurement.

[0053] The fin material was subjected to a brazing-equivalent heat treatment. The condition of the heat treatment was the same method as in (Strength after brazing). A sample for the polarization measurement was cut out from the fin material after the brazing-equivalent heat treatment, immersed in a 5% NaOH solution heated to 50° C., for 30 s, then immersed in a 30% HNO.sub.3 solution for 60 s, further washed with city water and ion-exchange water, and thereafter the non-dried sample was measured for pitting potential (reference electrode was a saturated calomel electrode) at room temperature under such conditions in a 2.67% AlCl.sub.3 solution at 40° C. in a degassed atmosphere at a potential sweep rate of 0.5 mV/s. The pitting potential was defined as a potential at which the current density upsurges in a current density-potential diagram. In the case where no clear upsurge of the current density was observed, however, the measurement was made by defining a potential of the current density of 0.1 mA/cm.sup.2 as the pitting potential. The results are indicated as Epit after brazing.

[0054] The case where the pitting potential was less noble than −780 mV was taken as ◯. Here, the less noble, the shallower the corrosion depth of the tube becomes.

(Melting Point)

[0055] For the prepared fin material, the solidus temperature was measured by a conventional method using DTA (differential thermal analysis). The temperature-rise rate during the measurement time was made to be 20° C./min for from room temperature to 500° C., and 2° C./min for in the range of 500 to 600° C. Alumina was used for the reference.

(Crystal Grain Diameter After Brazing)

[0056] The crystal grain diameter after brazing was measured by a stereoscopic microscope. The prepared fin material was subjected to the brazing-equivalent heat treatment, and thereafter immersed in a corrosive liquid in which hydrochloric acid, nitric acid, hydrofluoric acid and pure water were mixed in proportions of 16.4 mL, 15.8 mL, 6.3 mL and 61.5 mL, respectively, for a certain time to be etched until the crystal grain texture of the rolled surface became clearly visible; and thereafter, the crystal grain texture of the rolled surface was observed by a stereoscopic microscope. 20 times was basically employed as the observation magnification, and in the case where the crystal grain is very coarse or fine, the observation magnification was suitably varied according to the size of the crystal grain. The crystal grain texture was photographed for 5 visual fields, and the size of the crystal grain was measured by a sectioning method in the parallel direction to the rolling direction.

Measurement of (the Fe/(Mn+Si) Ratio in the Compound)

[0057] The prepared fin material was subjected to the same brazing-equivalent heat treatment as in the above; thereafter, a cross-section parallel to the rolling direction was exposed by a CP work; and individual compounds 0.5 μm or larger as the subject were quantitatively analyzed by particle analysis with EPMA to thereby determine averages of the contents of Mn, Fe and Si in the Al—Mn—Fe—Si compound. Here, the measurement area was made to be 50×50 μm.sup.2, and the number of visual fields was suitably selected so that the number of the compound particles to be measured was taken to be 300 or more particles at the least.

[0058] The case where the Fe/(Mn+Si) ratio in the compound was 0.25 or lower was taken as ◯◯; higher than 0.25 and lower than 0.30, as ◯; and 0.30 or higher, as X.

(Erosion Property)

[0059] By using the prepared fin material and a tube material (sacrificial material: 7072 (15% clad)/core material: 3003/brazing filler metal: 4045 (10% clad)) of 0.2 mm in plate thickness, a mini-core heat exchanger for evaluation of the erosion property was assembled according to the following procedure. First, the fin material was corrugation-worked. Then, the fin material was assembled on the tube material. A flux was applied in an amount of 5 g/m.sup.2 on a joining portion of the tube material with the fin material, and the resultant was subjected to a brazing heat treatment. The brazing was carried out under the condition of heating up to 600° C. at an average temperature-rise rate of 40° C./min, holding the temperature at 600° C. for 3 min, and then cooling at a temperature-fall rate of 100° C./min. Arbitrary portions of the fabricated mini-core heat exchanger were embedded in a resin, and the cross-section of the fin/tube joining portion was observed. A fin right near a joining portion fillet was observed and the state of the erosion of the fin was examined.

[0060] The case where any buckling was generated on the fin was taken as X; the case where erosion penetrating a half or more and less than the whole of the plate thickness was generated, as ◯; and the case where slight erosion of a half or less of the plate thickness was generated, as ◯◯.

(Sacrificial Anode Effect of the Fin: Corrosion Depth of the Tube)

[0061] A mini-core heat exchanger was fabricated by the same method as in (Erosion property). The heat exchanger assembled for the test was subjected to a SWAAT test (according to G85-A of ASTM) for 30 days. The test piece after the test was immersed in a boiled phosphoric acid-chromic acid mixed solution for 10 min to remove corrosion products; and the corrosion states of the fin and the tube were evaluated.

[0062] The sacrificial anode effect of the fin was evaluated based on the corrosion depth generated on the tube between the fin; and the case where the corrosion depth of the tube was 20 μm or deeper was taken as X; and shallower than 20 μm, as ◯.

(Resistance to Self-Corrosion of the Fin)

[0063] The resistance to self-corrosion of the fin was determined by embedding the test piece in a resin after the removal of the corrosion products, acquiring cross-sections of 20 arbitrary portions of the fin, and determining (an area in each cross-section where the fin remained)/(an area thereof before the corrosion test). The case where the remaining rate of the fin was 80% or higher was taken as ◯◯; 50 to 79%, as ◯; and lower than 50%, as X.

(Comprehensive Evaluation)

[0064] The case where any one test item was X, was evaluated as X.

[0065] The case where the pitting potential after brazing was ◯, and all the other test items were ◯ or better, was evaluated as ◯.

[0066] The case where the pitting potential after brazing was ◯, and all the other test items were ◯◯, was evaluated as ◯◯.

TABLE-US-00001 TABLE 1 Chemical component (%) No. Mn Si Fe Cu Zr Zn 1 1.0 1.0 0.20 0.05 0.15 2.0 2 1.4 1.0 0.20 0.05 0.15 2.0 3 1.55 1.0 0.20 0.05 0.15 2.0 4 1.70 1.0 0.20 0.05 0.15 2.0 5 1.78 1.0 0.20 0.05 0.15 2.0 6 2.0 1.0 0.20 0.05 0.15 2.0 7 1.7 0.4 0.20 0.05 0.15 2.0 8 1.7 0.8 0.20 0.05 0.15 2.0 9 1.7 0.95 0.20 0.05 0.15 2.0 10 1.7 1.15 0.20 0.05 0.15 2.0 11 1.7 1.25 0.20 0.05 0.15 2.0 12 1.7 1.5 0.20 0.05 0.15 2.0 13 1.7 1.0 0.05 0.05 0.15 2.0 14 1.7 1.0 0.20 0.05 0.15 2.0 15 1.7 1.0 0.50 0.05 0.15 2.0 16 1.7 1.0 0.20 0.05 0.02 2.0 17 1.7 1.0 0.20 0.05 0.15 2.0 18 1.7 1.0 0.20 0.05 0.40 2.0 19 1.7 1.0 0.20 0.05 0.15 0.5 20 1.7 1.0 0.20 0.05 0.15 2.0 21 1.7 1.0 0.20 0.05 0.15 3.5 22 1.7 1.0 0.20 0.05 0.15 2.6 23 1.7 1.0 0.20 0.05 0.15 2.9 24 1.7 1.0 0.20 0.05 0.15 3.6 25 1.7 1.33 0.20 0.05 0.15 2.0 26 1.55 1.0 0.20 0.00 0.15 2.0 27 1.7 1.0 0.20 0.00 0.15 2.0 28 1.7 0.95 0.20 0.00 0.15 2.0 29 1.7 1.0 0.20 0.00 0.15 2.6 30 1.7 1.15 0.20 0.00 0.15 2.0

TABLE-US-00002 TABLE 1 TS after Sacrificial brazing Epit after Melting point Crystal Brazing anode effect x less than brazing x - less than grain erosion (corrosion Material 135 MPa x - noble than 615° C. diameter property depth of the Overall evaluation Casting Homogenizing compound ∘135-139 MPa −780 mV ∘615-619° C. after Fe/(Mn + Si) x buckling tube) Resistance x: Either is x rate treatment (Pieces/ ∘∘140 MPa ∘ - less noble ∘∘620° C. or brazing into the ∘slight erosion x 20 or more to self- ∘: All ∘ or more No. Component (° C./Sec.) (° C. × time) μm2) or more than −780 mV more (μm) compound ∘∘no erosion ∘less than 20 corrosion ∘∘: All ∘∘ or more Comparative  1  1   2° C./s 450° C. × 10 h 40 123x −810∘ 619∘  700 0.28∘ ∘ 12∘ x x Example Inventive  2  2   2° C./s 450° C. × 10 h 40 135∘ −806∘ 623∘∘  700 0.27∘ ∘∘ 15∘ ∘ ∘ example  3  3   2° C./s 450° C. × 10 h 40 140∘∘ −804∘ 624∘∘  700 0.20∘∘ ∘∘ 15∘ ∘∘ ∘∘  4  4   2° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘∘  5  5   2° C./s 450° C. × 10 h 40 139∘ −802∘ 624∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘ Comparative  6  6   2° C./s 450° C. × 10 h 40 136∘ −800∘ 624∘∘  700 0.17∘∘ ∘∘ 15∘ ∘∘ x Huge Example intermetallic compound  7  7   2° C./s 450° C. × 10 h 40 120x −775x 634∘∘  700 0.35x ∘∘ 40x x x Inventive  8  8   2° C./s 450° C. × 10 h 40 136∘ −800∘ 633∘∘  700 0.29∘ ∘∘ 15∘ ∘ ∘ example  9  9   2° C./s 450° C. × 10 h 40 142∘∘ −802∘ 628∘∘  700 0.20∘∘ ∘∘ 15∘ ∘∘ ∘∘ 10 10   2° C./s 450° C. × 10 h 40 150∘∘ −805∘ 620∘∘  700 0.18∘∘ ∘∘ 15∘ ∘∘ ∘∘ 11 11   2° C./s 450° C. × 10 h 40 154∘∘ −807∘ 616∘  700 0.18∘∘ ∘∘ 15∘ ∘∘ ∘ Comparative 12 12   2° C./s 450° C. × 10 h 40 164∘∘ −810∘ 601x  700 0.16∘∘ x 13∘ ∘∘ x Example 13 13   2° C./s 450° C. × 10 h 40 141∘∘ −803∘ 626∘∘  700 0.14∘∘ ∘∘ 15∘ ∘ x Cost Inventive 14 14   2° C./s 450° C. × 10 h 40 144∘∘ −803∘ 626∘∘  700 0.19∘∘ ∘∘ 15∘ ∘ ∘ example Comparative 15 15   2° C./s 450° C. × 10 h 40 150∘∘ −803∘ 626∘∘  700 0.45∘∘ ∘∘ 15∘ x x Huge Example intermetallic compound 16 16   2° C./s 450° C. × 10 h 40 141∘∘ −803∘ 626∘∘  100 0.19∘∘ x 15∘ ∘∘ x Inventive 17 17   2° C./s 450° C. × 10 h 40 144∘∘ −803∘ 626∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘∘ example Comparative 18 18   2° C./s 450° C. × 10 h 40 145∘∘ −803∘ 626∘∘ 1100 0.19∘∘ ∘∘ 15∘ ∘∘ x Huge Example intermetallic compound 19 19   2° C./s 450° C. × 10 h 40 144∘∘ −728∘ 633∘∘  700 0.19∘∘ ∘∘ 70x ∘∘ x Inventive 20 20   2° C./s 450° C. × 10 h 40 144∘∘ −803∘ 626∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘ example Comparative 21 21   2° C./s 450° C. × 10 h 40 144∘∘ −878∘ 618∘  700 0.19∘∘ ∘  6∘ x x Example Inventive 22 22   2° C./s 450° C. × 10 h 40 144∘∘ −843∘ 622∘∘  700 0.19∘∘ ∘∘  9∘ ∘∘ ∘∘ example 23 23   2° C./s 450° C. × 10 h 40 144∘∘ −873∘ 621∘∘  700 0.19∘∘ ∘∘  5∘ ∘∘ ∘∘ Comparative 24 24   2° C./s 450° C. × 10 h 40 144∘∘ −940∘ 620∘∘  700 0.19∘∘ ∘∘  2∘ x x Example Inventive 25  2   2° C./s 450° C. × 10 h 40 135∘ −806∘ 623∘∘  700 0.27∘∘ ∘∘ 15∘ ∘ ∘ example 26  2   2° C./s 500° C. × 10 h 35 135∘ −806∘ 623∘∘  500 0.22∘∘ ∘∘ 15∘ ∘∘ ∘ 27  8   2° C./s 450° C. × 10 h 40 136∘ −800∘ 633∘∘  700 0.29∘∘ ∘∘ 15∘ ∘ ∘ 28  8   2° C./s 520° C. × 5 h  33 136∘ −800∘ 633∘∘  550 0.21∘∘ ∘∘ 15∘ ∘∘ ∘ 29  3   2° C./s 450° C. × 10 h 40 140∘∘ −804∘ 624∘∘  700 0.20∘∘ ∘∘ 15∘ ∘∘ ∘∘ Comparative 30  3   2° C./s 600° C. × 10 h  3 142∘∘ −804∘ 624∘∘  50 0.20∘∘ x 15∘ ∘∘ x Example 31 25   2° C./s 450° C. × 10 h 40 156∘∘ −807∘ 613x  700 0.17∘∘ x 15∘ ∘∘ x Inventive 32  3   2° C./s 400° C. × 10 h 40 140∘∘ −804∘ 624∘∘  950 0.20∘∘ ∘∘ 15∘ ∘∘ ∘∘ example Comparative 33  3   2° C./s 330° C. × 20 h 90 134x −804∘ 624∘∘ 1500 0.25∘∘ ∘∘ 15∘ ∘∘ x Example Inventive 34 26   2° C./s 450° C. × 10 h 40 136∘ −847∘ 626∘∘  610 0.20∘∘ ∘∘ 17∘ ∘∘ ∘ example 35 27   2° C./s 450° C. × 10 h 40 139∘ −844∘ 627∘∘  600 0.19∘∘ ∘∘ 18∘ ∘∘ ∘ 36 28   2° C./s 450° C. × 10 h 40 138∘ −842∘ 629∘∘  590 0.20∘∘ ∘∘ 16∘ ∘∘ ∘ 37 29   2° C./s 450° C. × 10 h 40 139∘ −873∘ 624∘∘  620 0.19∘∘ ∘∘  9∘ ∘∘ ∘ 38 30   2° C./s 450° C. × 10 h 40 146∘∘ −845∘ 623∘∘  600 0.18∘∘ ∘∘ 15∘ ∘∘ ∘∘ 39  4  15° C./s 450° C. × 10 h 40 146∘∘ −803∘ 624∘∘  700 0.26∘ ∘∘ 15∘ ∘∘ ∘ 40  4 0.6° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘∘ 41  4   1° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.19∘∘ ∘∘ 15∘ ∘∘ ∘∘ 42  4   5° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.20∘∘ ∘∘ 15∘ ∘∘ ∘∘ 43  4  13° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.23∘∘ ∘∘ 15∘ ∘∘ ∘∘ 44  4  25° C./s 450° C. × 10 h 40 144∘∘ −803∘ 624∘∘  700 0.29∘ ∘∘ 15∘ ∘∘ ∘∘

EXPLANATION OF REFERENCES LETTERS

[0067] 1 ALUMINUM ALLOY FIN MATERIAL [0068] 2 TUBE [0069] 10 HEAT EXCHANGER