Aluminum alloy material for heat exchanger fin, manufacturing method for same, and heat exchanger using the aluminum alloy material

Abstract

Disclosed is an aluminum alloy material for a heat exchanger fin, the aluminum alloy material containing Si: 1.0% to 5.0% by mass, Fe: 0.1% to 2.0% by mass, and Mn: 0.1% to 2.0% by mass with balance being Al and inevitable impurities, wherein 250 pieces/mm.sup.2 or more to 7104 pieces/mm.sup.2 or less of Si-based intermetallic compound particles having equivalent circle diameters of 0.5 to 5 m are present in a cross-section of the aluminum alloy material; and wherein 10 pieces/mm.sup.2 or more and 1000 pieces/mm.sup.2 or less of the AlFeMnSi-based intermetallic compounds having equivalent circle diameters of more than 5 m are present in a cross-section of the aluminum alloy material. The aluminum alloy material may further contain one or more additive elements of Mg, Cu, Zn, In, Sn, Ti, V, Zr, Cr, Ni, Be, Sr, Bi, Na, and Ca.

Claims

1. An aluminum alloy material for a heat exchanger fin, having a superior bonding function under heating of a single layer of the aluminum alloy material and containing Si in an amount from about 2.0% to 5.0% by mass, Fe: 0.1 to 2.0% by mass, and Mn: 0.1 to 2.0% by mass with balance being Al and inevitable impurities; wherein 250 pieces/mm.sup.2 or more to 710.sup.4 pieces/mm.sup.2 or less of Si-based intermetallic compound particles having equivalent circle diameters of 0.5 to 5 m are present in a cross-section of the aluminum alloy material; and wherein 10 pieces/mm.sup.2 or more and 1000 pieces/mm.sup.2 or less of the AlFeMnSi-based intermetallic compounds having equivalent circle diameters of more than 5 m are present in a cross-section of the aluminum alloy material.

2. The aluminum alloy material for the heat exchanger fin according to claim 1, wherein the aluminum alloy material is configured to satisfy T/To1.40 where T denotes tensile strength of a material plate, and To denotes tensile strength after heating at 450 C. for 2 hours.

3. The aluminum alloy material for the heat exchanger fin according to claim 1, further containing one or two selected from Mg: 2.0% by mass or less and Cu: 1.5% by mass or less.

4. The aluminum alloy material for the heat exchanger fin according to claim 1, further containing one or two or more selected from among Zn: 6.0% by mass or less, In: 0.3% by mass or less, and Sn: 0.3% by mass or less.

5. The aluminum alloy material for the heat exchanger fin according to claim 1, further containing one or more selected from among Ti: 0.3% by mass or less, V: 0.3% by mass or less, Zr: 0.3% by mass or less, Cr: 0.3% by mass or less, and Ni: 2.0% by mass or less.

6. The aluminum alloy material for the heat exchanger fin according to claim 1, further containing one or two or more selected from among Be: 0.1% by mass or less, Sr: 0.1% by mass or less, Bi: 0.1% by mass or less, Na: 0.1% by mass or less, and Ca: 0.05% by mass or less.

7. The aluminum alloy material for the heat exchanger fin according to claim 1, wherein tensile strength of the aluminum alloy material before heating for bonding is 80 to 250 MPa.

8. A heat exchanger manufactured by heating and bonding a fin member, which is made of the aluminum alloy material according to claim 1, and another constituent member of the heat exchanger together.

9. The heat exchanger according to claim 8, wherein the aluminum alloy material for the fin member has, after the heating for bonding, a microstructure in which the grain size of an aluminum matrix is 50 m or more, in a cross-section of the fin member.

10. The heat exchanger according to claim 8, wherein, in the microstructure in a cross-section of the aluminum alloy material for the fin member after the heating for bonding, the number of triple points of grain boundaries, where intermetallic compounds having equivalent circle diameters of 1 m or more exist, is 50% or more of the total number of triple points of all the grain boundaries.

11. The heat exchanger according to claim 8, wherein the microstructure in a cross-section of the aluminum alloy material for the fin member after the heating for bonding has 10 pieces/mm.sup.2 to 3000 pieces/mm.sup.2 of eutectic structures having lengths of 3 m or more within matrix grains.

12. A method of manufacturing the aluminum alloy material for the heat exchanger fin according to claim 1, the method comprising a casting step of casting an aluminum alloy for the aluminum alloy material, a heating step of heating a cast ingot before hot rolling, a hot rolling step of hot-rolling the ingot after the heating step, a cold rolling step of cold-rolling a hot-rolled plate, and an annealing step of annealing a cold-rolled plate midway the cold rolling step; wherein a casting speed is set to be 20 to 100 mm/min in the casting step; and wherein while the hot rolling step includes a rough rolling stage and a finish rolling stage, a total reduction ratio in the rough rolling stage is set to be 92 to 97%, the rough rolling stage including three or more passes in each of which a reduction ratio is 15% or more.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates a phase diagram of an AlSi alloy that is a binary eutectic alloy.54r

(2) FIG. 2 is an explanatory view to explain a liquid phase generation mechanism in an aluminum alloy material according to the present invention, which is developed with a bonding method using the aluminum alloy material.

(3) FIG. 3 is an explanatory view to explain a liquid phase generation mechanism in the aluminum alloy material according to the present invention, which is developed with the bonding method using the aluminum alloy material.

(4) FIG. 4 is an external view of a three-stage laminated test piece (mini-core) used in first to third embodiments.

(5) FIG. 5 is a diagram illustrating grain boundaries and a triple point thereof.

(6) FIG. 6 is an explanatory view illustrating a method for discriminating the triple point of the grain boundaries.

MODE FOR CARRYING OUT THE INVENTION

(7) The present invention will be described in detail below in connection with Inventive Examples and Comparative Examples.

First Embodiment

(8) Test Plates Having Compositions A1 to A56 and B1 in Tables 1 and 2 were first cast in sizes of 400 mm thick, 1000 mm wide, and 3000 mm long by the DC casting method. The casting speed was set to 40 mm/min. In the alloy compositions of Table 1, - represents that the content is not more than a detection limit, and balance includes inevitable impurities. After facing an ingot into a thickness of 380 mm, the ingot was heated up to 500 C. and that temperature was held for 5 hours as a heating retention step before hot rolling. The ingot was then subjected to the hot rolling step. In the hot rough rolling stage of the hot rolling step, the total reduction ratio was set to 93%, and the ingot was rolled to a thickness of 27 mm in the relevant stage. In the hot rough rolling stage, the number of passes in each of which the reduction ratio was 15% or more was set to five. After the hot rough rolling stage, a rolled plate was further rolled to a thickness of 3 mm in the hot finish rolling stage. In the subsequent cold rolling step, the rolled plate was rolled to a thickness of 0.09 mm. Furthermore, the rolled plate was subjected to an intermediate annealing step of 380 C.2 hours. Finally, the rolled plate was rolled to a final thickness of 0.07 mm in a final cold rolling stage, whereby a sample plate was obtained. In Comparative Examples 7 to 9, after rolling the plate to a thickness of 3 mm in the hot finish rolling stage, the rolled plate was further cold-rolled to a thickness of 0.120 mm in the cold rolling step. Furthermore, the rolled plate was subjected to the intermediate annealing step of 380 C.2 hours and then rolled to a final thickness of 0.07 mm in the final cold rolling stage, whereby a sample plate was obtained.

(9) TABLE-US-00001 TABLE 1 Com- position Alloy Composition (mass %) No. Si Fe Cu Mn Mg Zn In Sn Ni Ti V Zr Cr Be Sr Bi Na Ca Al IE A1 1.5 0.25 1.0 balance A2 2.0 0.25 1.0 balance A3 3.0 0.25 1.0 balance A4 3.5 0.25 1.0 balance A5 4.8 0.25 1.0 balance A6 2.5 0.1 1.0 balance A7 2.5 0.2 1.0 balance A8 2.5 1.0 1.0 balance A9 2.5 2.0 1.0 balance A10 2.5 0.5 0.12 balance A11 2.5 0.25 1.90 balance A12 2.5 2.00 2.00 balance A13 2.5 0.25 0.1 1.0 balance A14 2.5 0.25 1.5 1.0 balance A15 2.5 0.25 1.0 0.1 balance A16 1.0 0.5 1.2 2.0 balance A17 2.5 0.25 1.0 0.08 balance A18 2.5 0.25 1.0 0.12 balance A19 2.5 0.25 1.0 0.5 balance A20 2.5 0.25 1.0 1.2 balance A21 2.5 0.25 1.0 2.0 balance A22 2.5 0.25 1.0 5.5 balance A23 2.5 0.25 1.0 1.0 2.0 balance A24 2.5 0.25 1.0 2.0 0.1 balance A25 2.5 0.25 1.0 2.0 0.1 balance A26 2.5 0.25 1.0 0.05 balance A27 2.5 0.25 1.0 0.3 balance A28 2.5 0.25 1.0 0.05 balance A29 2.5 0.25 1.0 0.3 balance A30 2.5 0.25 1.0 0.05 balance A31 2.5 0.25 1.0 0.1 balance A32 2.5 0.25 1.0 2.0 balance A33 2.5 0.25 1.0 0.05 balance A34 2.5 0.25 1.0 0.3 balance A35 2.5 0.25 1.0 0.05 balance A36 2.5 0.25 1.0 0.3 balance A37 2.5 0.25 1.0 + 0.05 balance A38 2.5 0.25 1.0 0.3 balance A39 2.5 0.25 1.0 0.05 balance A40 2.5 0.25 1.0 0.3 balance A41 2.5 0.25 1.0 0.001 balance A42 2.5 0.25 1.0 0.1 balance A43 2.5 0.25 1.0 0.001 balance A44 2.5 0.25 1.0 0.1 balance A45 2.5 0.25 1.0 0.001 balance A46 2.5 0.25 1.0 0.1 balance A47 2.5 0.25 1.0 0.001 balance A48 2.5 0.25 1.0 0.1 balance A49 2.5 0.25 1.0 0.001 balance A50 2.5 0.25 1.0 0.05 balance IE: Inventive Example

(10) [Table 2]

(11) TABLE-US-00002 TABLE 2 Composition Alloy Composition (mass %) No. Si Fe Cu Mn Mg Zn In Sn Ni Ti V Zr Cr Be Sr Bi Na Ca Al CE A51 0.9 0.25 0.5 balance A52 5.3 0.25 0.5 balance A53 3.5 0.05 0.12 balance A54 3.5 0.1 0.08 balance A55 2.5 2.5 1.0 balance A56 2.5 0.25 2.2 balance CP B1 0.5 0.3 0.15 1.0 balance CE: Comparative Example CP: Combined Plate

(12) The above-mentioned test plates were evaluated for manufacturability in the manufacturing process. The manufacturability was evaluated by a method of, in manufacturing each plate or slab, rating the test plate to be (acceptable) when the sound plate or slab was obtained without causing any problems during the manufacturing process, and rating the test plate to be x (unacceptable) when any problem occurred during the manufacturing process, such as the occurrence of cracking during the casting, or a difficulty in continuing the rolling due to generation of giant intermetallic compounds during the casting.

(13) The surface density of the intermetallic compounds in the manufactured plate (material plate) was measured with SEM observation (observation of a reflected electron image) of a cross-section of the plate taken in the direction of plate thickness. The Si-based intermetallic compounds and the AlFeMnSi-based intermetallic compounds were discriminated based on the difference in contrast with the observation of the SEM-reflected electron image. The observation was performed on three viewing fields for each sample. The respective surface densities of the Si-based intermetallic compounds having the equivalent circle diameters of 0.5 m to 5 m and the AlFeMnSi-based intermetallic compounds having the equivalent circle diameters of 5 m or more in the sample were measured through an image analysis of an SEM photo in each viewing field.

(14) Tensile tests were performed on the material before and after the heating for the bonding of each manufactured plate and after heating at 450 C. for 2 hours. The tensile tests were carried out on each sample at room temperature on conditions of a tensile speed of 10 mm/min and a gauge length of 50 mm in accordance with JIS Z2241. In the tensile test after the heating for the bonding, the sample was evaluated by heating it under the same conditions of the heating for the bonding as those set for a mini-core described below.

(15) Next, as illustrated in FIG. 4, each test plate was formed into a fin member having a width of 16 mm, a crest height of 7 mm, and a pitch of 2.5 mm. The fin member was combined with a tube member having a plate thickness of 0.4 mm, which was obtained by electrically welding a combined plate having the composition B1 in Table 2. A three-stage laminated test piece (mini-core), illustrated in FIG. 4, was fabricated by assembling the combination of the fin members and the tube members with the aid of a stainless jig.

(16) The above-mentioned mini-core was dipped in a suspension solution containing 10% of non-corrosive fluoride-based flux. After drying, the mini-core was heated in a nitrogen atmosphere under conditions of the heating for the bonding, listed in Table 3, thereby bonding the fin and tube members to each other. For Inventive Example 16, the fin and tube members were bonded by heating them in vacuum without applying flux. Moreover, the retention time at each specified temperature during the bonding was set to 3 min. In the case of the mini-core mentioned above, because of the difference in coefficient of thermal expansion between the stainless jig and the aluminum material, a compression load of about 4N was generated between the stainless jig and the mini-core during the heating for the bonding. This implies that, with calculation based on a bonding area, stress of about 10 kPa is generated at the bonding interface between the fin and tube members.

(17) After heating and bonding the fin and tube members to each other, the fin was peeled from the tube, and a rate (bonding rate) of completely-bonded portions was measured by examining 40 bonding portions between the tube and the fin of the mini-core. The measurement result was determined to be (excellent) when the bonding rate was 90% or more, (good) when it was 80% or more and less than 90%, (fair) when it was 70% or more and less than 80%, and x (poor) when it was less than 70%.

(18) A deformation rate attributable to fin buckling was also evaluated by measuring the fin height in the mini-core before and after the bonding. The deformation rate was determined to be (excellent) when a rate of change in the fin height between before and after the bonding with respect to the fin height before the bonding was 5% or less, (good) when it was more than 5% and 10% or less, (fair) when it was more than 10% and 15% or less, and x (poor) when it was more than 15%.

(19) The material structure of each sample after the heating for the bonding was also examined in the first embodiment. The study was conducted by embedding the mini-core after the bonding in a resin, grinding it, and by observing the structure in a cross-section of the member with an optical microscope. In more detail, grain sizes were first measured by observing a cross-section of the member, taken in the direction of plate thickness, after grinding and etching with the optical microscope. As a measurement method, a mean grain length was measured at a center in the direction of plate thickness in accordance with ASTME112-96.

(20) Furthermore, the surface density of the eutectic structures within the grains, having lengths of 3 m or more, was measured. The measurement was performed by grinding and etching a cross-section of the member, the cross-section being perpendicular to the direction of plate thickness, and by observing the structure in the cross-section of the member with the optical microscope. In addition, after grinding the cross-section of the member in a similar way, the cross-section was etched using the Keller's reagent, for example, and the positions of the intermetallic compounds were identified. Moreover, the grain boundaries in the relevant cross-section were made clear by the anodic oxidation method, and the positions of the triple points of the grain boundaries were identified. By comparing the positions of the intermetallic compounds and the positions of the triple points of the grain boundaries, a rate of the number of triple points of the grain boundaries where the intermetallic compounds having the equivalent circle diameters of 1 m or more existed was determined with respect to the number of triple points of all the grain boundaries. For an unclear region, surface components of elements, such as Si, Fe and Mn were analyzed by employing the EPMA. As a result, portions where the Si composition was reduced in a linear form were identified as the grain boundaries, and portions where the compositions of other elements, such as Si and Fe, were high were identified as the intermetallic compounds. Among the number of triple points of all the grain boundaries, a rate of the number of triple points of the grain boundaries where the intermetallic compounds having the equivalent circle diameters of 1 m or more existed was determined. The observation was made using a single-plate sample that was heated under the conditions of the heating for the bonding as those for the mini-core, and the measurement was performed for five observation fields at a magnification of 200.

(21) Tables 3 and 4 list the respective evaluation results of the manufacturability, the surface density of the intermetallic compounds, the tensile strength, and the material structure after the heating for the bonding for each test piece, as well as the mini-core bonding test. Tables 3 and 4 further list equilibrium liquid phase rates under the bonding conditions (i.e., heating temperature) for each sample. The equilibrium liquid phase rate is a calculated value obtained by employing the equilibrium phase-diagram calculation software. It is to be noted that E+ in Tables 3 and 4 indicates exponential notation. For example, 1.2.E+03 implies 1.210.sup.3.

(22) TABLE-US-00003 TABLE 3 Heating Tensile Conditions Strength (Mpa) for Before Heating Bonding Composition Bonding for Bonding Rate Deformation No. (a) (b) (c) (d) (e) T T.sub.0 T/T.sub.0 (f) (g) (h) (i) (%) Rate IE1 A1 1.2.E+03 1.5.E+02 620 10 127 111 1.14 138 178 67 62 86 IE2 A2 2.3.E+03 2.2.E+02 610 13 135 117 1.15 140 155 72 73 89 IE3 A3 3.1.E+03 3.1.E+02 600 20 146 127 1.15 132 126 83 85 95 IE4 A4 4.2.E+03 3.5.E+02 600 27 150 130 1.15 123 117 89 96 99 IE5 A5 5.7.E+03 5.3.E+02 590 35 151 130 1.16 137 100 93 122 100 IE6 A6 2.4.E+03 1.4.E+02 600 14 140 122 1.15 136 291 76 84 91 IE7 A7 2.5.E+03 2.5.E+02 600 14 142 123 1.15 138 362 76 82 91 IE8 A8 2.3.E+03 2.9.E+02 600 12 150 128 1.17 155 95 73 94 90 IE9 A9 2.4.E+03 3.4.E+02 600 10 151 127 1.19 158 75 70 106 88 IE10 A10 3.5.E+03 1.1.E+02 600 17 120 92 1.31 122 189 77 323 92 IE11 A11 1.9.E+03 5.0.E+01 600 11 160 129 1.24 157 195 72 31 85 IE12 A12 1.7.E+03 2.0.E+01 600 6 170 130 1.31 168 213 54 15 79 IE13 A13 2.6.E+03 1.5.E+02 600 15 155 135 1.15 142 138 76 73 91 IE14 A14 2.5.E+03 1.6.E+02 600 23 220 168 1.31 174 141 83 154 95 IE15 A15 2.3.E+03 1.7.E+02 600 15 155 134 1.16 153 144 73 72 91 IE16 A16 2.7.E+02 1.6.E+02 600 6 225 173 1.30 235 174 42 80 73 IE17 A30 2.5.E+03 1.6.E+02 600 14 141 123 1.15 144 145 74 81 92 IE18 A31 2.6.E+03 1.4.E+02 600 14 145 126 1.15 147 137 76 84 92 IE19 A32 2.7.E+03 1.4.E+02 600 14 165 140 1.18 162 144 82 78 91 IE20 A33 2.6.E+03 1.5.E+02 600 14 145 125 1.16 142 141 76 75 95 IE21 A34 2.5.E+03 1.6.E+02 600 14 150 128 1.17 147 140 72 70 94 IE22 A35 2.5.E+03 1.6.E+02 600 14 142 123 1.15 140 151 76 83 93 IE23 A36 2.4.E+03 1.8.E+02 600 14 144 124 1.16 148 152 75 81 96 IE24 A37 2.6.E+03 1.6.E+02 600 14 145 127 1.14 141 141 76 75 92 IE25 A38 2.7.E+03 1.7.E+02 600 14 152 135 1.13 149 144 76 74 91 IE26 A39 2.5.E+03 1.7.E+02 600 14 145 126 1.15 142 139 74 72 90 IE27 A40 2.4.E+03 1.5.E+02 600 14 153 131 1.17 143 147 76 82 90 IE28 A41 4.1.E+03 1.4.E+02 600 14 140 122 1.15 142 140 68 75 94 IE29 A42 9.2.E+03 1.7.E+02 600 14 142 123 1.15 144 149 76 78 97 IE30 A43 3.6.E+03 1.5.E+02 600 14 143 124 1.15 142 151 69 105 92 IE31 A44 7.8.E+03 1.4.E+02 600 14 140 122 1.15 140 138 77 112 92 IE32 A45 2.4.E+03 1.5.E+02 600 14 140 122 1.15 143 141 73 76 91 IE33 A46 2.6.E+03 1.6.E+02 600 14 139 121 1.15 141 144 76 85 90 IE34 A47 3.4.E+03 1.6.E+02 600 14 144 125 1.15 140 151 78 98 90 IE35 A48 9.3.E+03 1.7.E+02 600 14 140 122 1.15 143 141 75 106 92 IE36 A49 2.4.E+03 1.8.E+02 600 14 143 124 1.15 144 147 71 82 90 IE37 A50 2.7.E+03 1.5.E+02 600 14 140 122 1.15 140 146 76 77 91 IE: Inventive Example (a) Manufacturability (b) Surface Density of Si-based Intermetallic Compounds (number/mm.sup.2) (c) Surface Density of AlFeMnSi-based Intermetallic Compounds (number/mm.sup.2) (d) Heating Temperature ( C.) (e) Equilibrium Liquid Phase Rate (%) (f) After Heating for Bonding (g) Grain Size after Heating for Bonding (m) (h) Rate of Triple Points of Grain Boundaries where Intermetallic Compounds Exist (%) (i) Surface Density of Eutectic Structures within Grains (number/mm.sup.2)

(23) TABLE-US-00004 TABLE 4 Heating Tensile Strength Conditions (Mpa) for Before Heating for Bonding Composition Bonding Bonding Rate Deformation No. (a) (b) (c) (d) (e) T T.sub.0 T/T.sub.0 (f) (g) (h) (i) (%) Rate CE1 A51 2.2.E+02 2.2.E+02 620 2 120 106 1.13 118 141 40 8 14 X CE2 A52 7.2.E+04 1.2.E+03 580 36 155 134 1.16 121 29 93 3200 100 X CE3 A53 4.3.E+03 7.0.E+00 600 17 74 73 1.02 73 230 76 134 91 X CE4 A54 3.2.E+03 8.0.E+00 600 27 75 74 1.02 76 245 88 98 98 X CE5 A55 X CE6 A56 1.8.E+03 9.0.E+00 600 11 78 76 1.02 78 124 79 9 83 X CE7 A7 2.5.E+03 2.5.E+02 600 14 176 124 1.42 138 38 71 65 92 X CE8 A13 2.6.E+03 1.5.E+02 600 15 194 135 1.45 142 29 77 71 92 X CE9 A4 4.2.E+03 3.5.E+02 600 27 184 130 1.42 123 35 89 94 99 X CE: Comparative Example (a) Manufacturability (b) Surface Density of Si-based Intermetallic Compounds (number/mm.sup.2) (c) Surface Density of AlFeMnSi-based Intermetallic Compounds (number/mm.sup.2) (d) Heating Temperature ( C.) (e) Equilibrium Liquid Phase Rate (%) (f) After Heating for Bonding (g) Grain Size after Heating for Bonding (m) (h) Rate of Triple Points of Grain Boundaries where Intermetallic Compounds Exist (%) (i) Surface Density of Eutectic Structures within Grains (number/mm.sup.2)

(24) As seen from Tables 3 and 4, the manufacturability was acceptable in the samples that satisfied the conditions specified in the present invention with regard to the composition of the aluminum alloy material and the heating conditions. On the other hand, in the rolling of the sample having the alloy composition A55, the relevant sample could not be rolled up to the final plate thickness because Fe exceeded the specified amount and giant intermetallic compounds were generated during the casing.

(25) Comparing, as for the results of the bonding tests, the evaluation results of the individual mini-core samples with the compositions (Tables 1 and 2) of the aluminum alloy materials of the fin members, the bonding rate, the fin buckling, and the tensile length were all acceptable in the samples (Inventive Examples 1-37), which satisfied the conditions specified in the present invention with regard to the composition of the aluminum alloy material and the heating conditions. For Inventive Examples 15-27 that were samples made of alloys containing, as additive elements, Mg, Ni, Ti, V, Zr and Cr in addition to Si, Fe, Mn as essential elements, it was confirmed that the evaluation results of the deformation rate was more satisfactory, and that those elements had the effect of increasing the strength.

(26) On the other hand, in Comparative Example 1, because the Si component did not reach the specified amount and the surface density of the Si-based intermetallic compounds in the material plate also did not reach the specified value, the liquid phase generation rate was as low as less than 5% even with the heating temperature set to be relatively high. Hence the bonding rate was reduced and the bonding performance was inferior.

(27) In Comparative Example 2, because the Si component exceeded the specified amount and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate also exceeded the specified value, the liquid phase rate during the bonding was increased even with the heating temperature set to be relatively low. Moreover, the grain sizes after the heating were small. Hence the fin was buckled and the deformation rate was unacceptable.

(28) In Comparative Example 3, because the Fe component did not reach the specified amount and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate also did not reach the specified value, the strengths before and after the heating were low and unacceptable. Moreover, the fin was buckled and the deformation rate was also unacceptable.

(29) In Comparative Example 4, because the Mn component did not reach the specified amount and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate also did not reach the specified value, the strengths before and after the heating were low and unacceptable. Moreover, the fin was buckled and the deformation rate was also unacceptable.

(30) In Comparative Example 5, because the Fe component exceeded the specified amount, a problem occurred in the manufacturability, and the evaluation by the bonding test could not be performed.

(31) In Comparative Example 6, because the Mn component exceeded the specified amount and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate did not reach the specified value, the strengths before and after the heating were low and unacceptable. Moreover, the fin was buckled and the deformation rate was also unacceptable.

(32) In Comparative Examples 7 to 9, because the reduction ratio in the final cold rolling stage was larger and T/To exceeded the specified value, grains became too finer during the heating for the bonding, and the deformation rate was unacceptable.

Second Embodiment

(33) In a second embodiment, influences of the heating temperature as one of the bonding conditions were examined. The material plates manufactured in the first embodiment were optionally selected as listed in Table 3 and were formed into fins similar to those in the first embodiment. Furthermore, as in the first embodiment, three-stage laminated test pieces (mini-cores) were fabricated (FIG. 4). The mini-cores were each dipped in a suspension solution containing 10% of non-corrosive fluoride-based flux. After drying, the mini-cores were heated to various heating temperatures and held there for predetermined times, listed in Table 3, in a nitrogen atmosphere, thereby bonding the fin and tube members to each other.

(34) The bonding rate and the deformation rate attributable to fin buckling were evaluated in the same way as in the first embodiment by measuring the bonding rate and the dimensional change after the bonding. Moreover, as in the first embodiment, the structure in a cross-section of each member was observed to determine the surface density of the intermetallic compounds, the grain sizes after the heating for the bonding, the surface density of the eutectic structures having lengths of 3 m or more within the grains, and the rate of the number of triple points of the grain boundaries where the intermetallic compounds having the equivalent circle diameters of 1 m or more existed with respect to the number of triple points of all the grain boundaries. The evaluation results are listed in Table 5. It is to be noted that in Table 5, for example, 3.1E+03 implies 3.110.sup.3.

(35) TABLE-US-00005 TABLE 5 Heating Conditions for Bonding Bonding Composition Retention Rate Deformation No. (b) (c) (d) (e) Time (sec) (j) (k) (h) (i) (%) Rate IE38 A3 3.1E+03 3.1E+02 590 16 180 576 271 81 79 94 IE39 A3 3.1E+03 3.1E+02 610 27 180 576 401 91 105 99 IE40 A22 2.5E+03 2.4E+02 600 16 180 576 336 81 85 94 IE41 A22 2.5E+03 2.4E+02 620 33 180 576 466 93 116 100 IE42 A17 2.6E+03 2.5E+02 600 15 180 574 349 80 88 93 IE43 A17 2.6E+03 2.5E+02 620 30 180 574 479 93 124 100 IE44 A2 2.3E+03 2.2E+02 600 8 180 591 239 70 65 88 IE45 A3 3.1E+03 3.1E+02 580 12 20 576 65 77 66 92 IE46 A3 3.1E+03 3.1E+02 590 16 3300 576 3391 81 82 94 RE1 A4 4.2E+03 3.5E+02 620 47 180 576 466 93 245 100 X RE2 A2 2.3E+03 2.2E+02 580 2 180 591 109 35 8 32 X RE3 A3 3.1E+03 3.1E+02 620 38 180 576 466 93 289 100 X RE4 A3 3.1E+03 3.1E+02 590 16 5 576 25 46 55 75 RE5 A3 3.1E+03 3.1E+02 610 27 3700 576 3921 91 312 99 X IE: Inventive Example RE: Reference Example (b) Surface Density of Si-based Intermetallic Compounds (number/mm.sup.2) (c) Surface Density of AlFeMnSi-based Intermetallic Compounds (number/mm.sup.2) (d) Heating Temperature ( C.) (e) Equilibrium Liquid Phase Rate (%) (h) Rate of Triple Points of Grain Boundaries where Intermetallic Compounds Exist (%) (i) Surface Density of Eutectic Structures within Grains (number/mm.sup.2) (j) Temperature at which Liquid Phase Rate is 5% ( C.) (k) Time during which Liquid Phase Rate is 5% or more (sec)

(36) As described above, when bonding the aluminum alloy material according to the present invention, it is preferable that the heating temperature is set to temperature at which the liquid phase rate is 5 to 30%, and the time during which the liquid phase rate is 5% or more is 30 sec or longer and 3600 sec or shorter. As seen from Table 3, in Inventive Examples 38-46, those conditions are all satisfied, and the bonding rate and the deformation rate were both acceptable.

(37) On the other hand, in Reference Examples 1 and 3, because the heating temperature was high and the liquid phase rate was too high, the shape could not be maintained, thus causing large deformation. In Reference Example 2, because the heating temperature was low and the liquid phase rate was also low, the bonding was insufficient.

(38) In Reference Example 4, because the retention time during which the liquid phase rate was 5% or more was short, the bonding rate was insufficient. In Reference Example 5, because the retention time during which the liquid phase rate was 5% or more was too long, large deformation occurred.

Third Embodiment

(39) In a third embodiment, influences of additive elements upon corrosion resistance were examined. The material plates manufactured in the first embodiment were optionally selected as listed in Table 6 and were formed into fins similar to those in the first embodiment. Furthermore, as in the first embodiment, three-stage laminated test pieces (mini-cores) were fabricated (FIG. 4). The mini-cores were each dipped in a suspension solution containing 10% of non-corrosive fluoride-based flux. After drying, the mini-cores were heated to various heating temperatures and held there for predetermined times, listed in Table 3, in a nitrogen atmosphere, thereby bonding the fins and the tubes to each other.

(40) The bonding rate and the deformation rate were evaluated in the same way as in the first embodiment by measuring the bonding rate and the dimensional change after the bonding. Moreover, as in the first embodiment, the structure in a cross-section of each member was observed to determine the surface density of the intermetallic compounds, the surface density of the eutectic structures having lengths of 3 m or more within the grains, and the rate of the number of triple points of the grain boundaries where the intermetallic compounds having the equivalent circle diameters of 1 m or more existed with respect to the number of triple points of all the grain boundaries.

(41) In addition, for evaluation of corrosion resistance of the fin itself, the CASS test was conducted for 500 h, and a corrosion state of the fin was confirmed. By observing a cross-section of the fin with an optical microscope, the corrosion state was determined to be (excellent) when a rate of the remaining fin was 70% or more, (good) when it was 50% or more and less than 70%, A (fair) when it was 30% or more and less than 50%, and x (poor) when it was less than 30%. The evaluation results are listed in Table 6. It is to be noted that in Table 6, for example, 2.3.E+03 implies 2.310.sup.3.

(42) TABLE-US-00006 TABLE 6 Heating Conditions for Bonding Composition Bonding Rate Deformation Corrosion No. (b) (c) (d) (e) (h) (i) (%) Rate Resistance IE47 A2 2.3.E+03 2.2.E+02 610 13 72 73 91 IE48 A17 2.5.E+03 2.4.E+02 600 15 73 72 91 IE49 A18 2.6.E+03 2.5.E+02 600 6 42 80 73 IE50 A19 2.6.E+03 2.6.E+02 600 14 76 82 92 IE51 A20 2.5.E+03 2.4.E+02 600 14 82 84 92 IE52 A21 2.7.E+03 2.4.E+02 600 15 85 93 92 IE53 A22 2.4.E+03 2.5.E+02 600 16 92 113 92 IE54 A23 2.5.E+03 2.5.E+02 600 24 93 122 100 IE55 A24 2.6.E+03 2.6.E+02 600 26 93 145 100 IE56 A25 2.6.E+03 2.4.E+02 600 24 92 126 98 IE57 A26 2.7.E+03 2.5.E+02 600 24 93 122 100 IE58 A27 2.4.E+03 2.5.E+02 600 24 90 134 96 IE59 A28 2.5.E+03 2.4.E+02 600 14 83 85 93 IE60 A29 2.4.E+03 2.4.E+02 600 14 78 89 92 IE: Inventive Example (b) Surface Density of Si-based Intermetallic Compounds (number/mm.sup.2) (c) Surface Density of AlFeMnSi-based Intermetallic Compounds (number/mm.sup.2) (d) Heating Temperature ( C.) (e) Equilibrium Liquid Phase Rate (%) (h) Rate of Triple Points of Grain Boundaries where Intermetallic Compounds Exist (%) (i) Surface Density of Eutectic Structures within Grains (number/mm.sup.2)

(43) In Inventive Examples 48 to 60 according to the third embodiment, aluminum alloys containing, as additive elements, Cu, Zn, In, Sn, Ti and V in addition to the essential elements, i.e., Si, Fe and Mn, were used as samples. In those Inventive Examples, as seen from Table 6, the corrosion resistance was improved in comparison with that of an alloy used in Inventive Example 47 not containing Zn, etc. Thus, usefulness of the above-mentioned additive elements was confirmed.

Fourth Embodiment

(44) In a fourth embodiment, influences of changes in distribution of the intermetallic compounds in the aluminum alloy material upon the bonding performance due to the manufacturing process were examined. The material plates manufactured in the first embodiment were optionally selected as listed in Table 7 and were formed into fins similar to those in the first embodiment under manufacturing conditions listed in Table 7. Furthermore, as in the first embodiment, three-stage laminated test pieces (mini-cores) were fabricated (FIG. 4). The mini-cores were each dipped in a suspension solution containing 10% of non-corrosive fluoride-based flux. After drying, the mini-cores were heated to 600 C. and held there for a holding time of 3 min in a nitrogen atmosphere, thereby bonding the fins and the tubes to each other. The manufacturability was also evaluated as in the first embodiment (Table 7).

(45) TABLE-US-00007 TABLE 7 Manufacturing Process Com- Slab posi- Casting Thickness tion Speed after Facing No. (a) (mm/min) (mm) (l) (m) (n) (o) (p) IE61 A3 40 400 25 94 5 480 5 IE62 A3 30 400 25 94 5 480 5 IE63 A3 25 400 25 94 5 480 5 IE64 A3 80 400 25 94 5 480 5 IE65 A3 90 400 25 94 5 480 5 IE66 A3 40 400 32 92 5 480 5 IE67 A3 40 600 18 97 5 480 5 IE68 A3 40 400 25 94 3 480 5 IE69 A3 40 400 25 94 4 480 5 IE70 A3 40 400 25 94 8 480 5 IE71 A3 40 400 25 94 5 440 5 IE72 A3 40 400 25 94 5 480 0 IE73 A3 40 400 25 94 5 480 13 IE74 A3 40 400 25 94 5 520 5 CE10 A3 15 400 25 94 5 480 5 CE11 A3 X 120 400 25 94 5 480 5 CE12 A3 40 600 60 90 5 480 5 CE13 A3 40 750 15 98 5 480 5 CE14 A3 40 400 25 94 2 480 5 IE: Inventive Example CE: Comparative Example (a) Manufacturability (l) Plate Thickness after Hot Rough Rolling Stage (mm) (m) Total Reduction ratio in Hot Rough Rolling Stage (%) (n) Number of Passes in which Reduction ratio is 15% or more in Hot Rough Rolling Stage (number) (o) Heating Retention Temperature before Hot Rolling ( C.) (p) Heating Retention Time before Hot Rolling (hour)

(46) The bonding rate and the deformation rate attributable to fin buckling were evaluated in the same way as in the first embodiment by measuring the bonding rate and the dimensional change after the bonding. Moreover, as in the first embodiment, the structure in a cross-section of each member was observed to determine the surface density of the intermetallic compounds, the grain sizes after the heating for the bonding, the surface density of the eutectic structures having lengths of 3 m or more within the grains, and the rate of the number of triple points of the grain boundaries where the intermetallic compounds having the equivalent circle diameters of 1 m or more existed with respect to the number of triple points of all the grain boundaries. The evaluation results are listed in Table 8. Table 8 further list the results of measuring, in relation to the measurement of the surface density of the intermetallic compounds before the heating for the bonding, not only respective surface densities of the Si-based intermetallic compounds having the equivalent circle diameters of 0.5 m to 5 m and the AlFeMnSi-based intermetallic compounds having the equivalent circle diameters of 5 m or more, but also the Si-based intermetallic compounds having the equivalent circle diameters of 5 m or more and the AlFeMnSi-based intermetallic compounds having the equivalent circle diameters of 0.5 m or more and 5 m or less and of 10 m or more. It is to be noted that in Table 8, for example, 3.1.E+03 implies 3.110.sup.3.

(47) TABLE-US-00008 TABLE 8 (b) (c) 0.5 m 0.5 m Equivalent Equivalent Equivalent Equivalent Equivalent circle circle circle circle circle diameters diameters diameters diameters diameters Bonding Composition 5 m >5 m 5 m >5 m 10 m Rate Deformation No. (number/mm.sup.2) (number/mm.sup.2) (number/mm.sup.2) (number/mm.sup.2) (number/mm.sup.2) (g) (h) (i) (%) Rate IE61 A3 3.1.E+03 0.0.E+00 7.5.E+03 3.1.E+02 0.0.E+00 126 83 85 95 IE62 A3 7.2.E+02 0.0.E+00 5.7.E+03 6.5.E+02 0.0.E+00 102 78 84 80 IE63 A3 3.8.E+02 0.0.E+00 4.7.E+03 8.8.E+02 0.0.E+00 91 79 83 73 IE64 A3 5.5.E+03 0.0.E+00 1.5.E+04 4.2.E+01 0.0.E+00 183 81 84 98 IE65 A3 6.2.E+03 0.0.E+00 1.7.E+04 3.3.E+01 0.0.E+00 205 80 84 99 IE66 A3 2.6.E+03 0.0.E+00 7.5.E+03 8.4.E+02 0.0.E+00 118 79 83 92 IE67 A3 4.6.E+03 0.0.E+00 7.5.E+03 2.2.E+02 0.0.E+00 164 80 85 96 IE68 A3 2.2.E+03 0.0.E+00 7.5.E+03 6.8.E+02 0.0.E+00 106 79 85 90 IE69 A3 2.7.E+03 0.0.E+00 7.5.E+03 4.9.E+02 0.0.E+00 118 78 83 93 IE70 A3 4.3.E+03 0.0.E+00 7.5.E+03 1.9.E+02 0.0.E+00 152 82 84 97 IE71 A3 3.2.E+03 0.0.E+00 7.5.E+03 2.7.E+02 0.0.E+00 90 80 85 94 IE72 A3 3.3.E+03 0.0.E+00 7.5.E+03 2.9.E+02 0.0.E+00 101 81 83 92 IE73 A3 3.1.E+03 0.0.E+00 7.5.E+03 6.8.E+02 0.0.E+00 109 81 83 93 IE74 A3 3.4.E+03 0.0.E+00 7.5.E+03 8.7.E+02 0.0.E+00 92 82 84 93 CE10 A3 2.3.E+02 0.0.E+00 2.8.E+03 1.2.E+03 0.0.E+00 46 82 83 62 X X CE11 A3 CE12 A3 2.4.E+02 0.0.E+00 7.5.E+03 1.1.E+03 0.0.E+00 48 80 84 65 X X CE13 A3 2.3.E+02 0.0.E+00 7.5.E+03 1.3.E+03 0.0.E+00 45 78 85 60 X X CE14 A3 4.7.E+02 0.0.E+00 7.5.E+03 1.1.E+03 0.0.E+00 47 81 83 74 X IE: Inventive Example CE: comparative Example (b) Surface Density of Si-based Intermetallic Compounds (c) Surface Density of AlFeMnSi-based Intermetallic Compounds (g) Grain Size after Heating for Bonding (M) (h) Rate of Triple Points of Grain Boundaries where Intermetallic Compounds Exist (%) (i) Surface Density of Eutectic Structures within Grains (number/mm.sup.2)

(48) In samples (Inventive Examples 61 to 74) manufactured according to the method of the present invention, the bonding rate and the deformation rate were both acceptable.

(49) On the other hand, in Comparative Example 10, because the casting speed was too low, the surface density of the Si-based intermetallic compounds in the material plate did not reach the specified value and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate exceeded the specified value. Thus, due to coarsening of the Si-based intermetallic compounds and the AlFeMnSi-based intermetallic compounds, the grain sizes after the heating were reduced, whereby the fin was buckled and the deformation rate was unacceptable. Moreover, because the amount of the Si-based intermetallic compounds satisfying the specified surface density was reduced, the bonding rate was unacceptable.

(50) In Comparative Example 11, because the casting speed was too high, cracking occurred during the manufacturing of the ingot, and the sample plate could not be manufactured.

(51) In Comparative Example 12, the total reduction ratio in the hot rough rolling stage was less than the specified value, and the Si-based intermetallic compounds and the AlFeMnSi-based intermetallic compounds in the material plate were not sufficiently made finer. Thus, the surface density of the Si-based intermetallic compounds in the material plate did not reach the specified value, and the bonding rate was unacceptable. In addition, because the surface density of the AlFeMnSi-based intermetallic compounds in the material plate exceeded the specified value, the grain sizes after the heating were reduced due to coarsening of the intermetallic compounds. As a result, the fin was buckled and the deformation rate was unacceptable.

(52) In Comparative Example 13, because the slab thickness after the facing was too large, the total reduction ratio in the hot rough rolling stage was more than the specified value. Because the ingot thickness was too large, the cooling rate during the manufacturing of the ingot was reduced, and coarse precipitated deposits were generated. The coarse precipitated deposits were not sufficiently fragmented in the hot rough rolling stage, whereby the surface density of the Si-based intermetallic compounds in the material plate did not reach the specified value and the surface density of the AlFeMnSi-based intermetallic compounds in the material plate exceeded the specified value. The grain sizes after the heating were reduced due to coarsening of the intermetallic compounds. As a result, the fin was buckled and the deformation rate was unacceptable. Because the surface density of the Si-based intermetallic compounds in the material plate did not reach the specified value, the bonding rate was low and unacceptable.

(53) In Comparative Example 14, the number of passes in each of which the reduction ratio was 15% or more was less than three in the hot rough rolling stage. Therefore, the AlFeMnSi-based intermetallic compounds were not sufficiently made finer, and the surface density of those intermetallic compounds exceeded the specified value. Liquid phases were generated around the coarse AlFeMnSi-based intermetallic compounds, and a rate of liquid phase pools occupying in the plate thickness was increased. As a result, the fin was buckled and the deformation rate was unacceptable.

INDUSTRIAL APPLICABILITY

(54) The aluminum alloy material according to the present invention is useful as the fin member of the heat exchanger, and it can be bonded to another constituent member of the heat exchanger, including another fin member, without using a bonding material, such as a brazing filler metal or a welding material. Therefore, the heat exchanger can be efficiently manufactured. Changes in size and shape hardly occur during the bonding of the aluminum alloy material. Thus, the aluminum alloy material and the bonding method using the aluminum alloy material, according to the present invention, are remarkably effective from the industrial point of view.