Aluminum alloy cladding material for heat exchanger

Abstract

An aluminum alloy clad material includes a core material, one side being clad with cladding material 1, the other side being clad with cladding material 2, the core material including an aluminum alloy that includes 0.5 to 1.8% of Mn, and limited to 0.05% or less of Cu, with the balance being Al and unavoidable impurities, the cladding material 1 including an aluminum alloy that includes 3 to 10% of Si, and 1 to 10% of Zn, with the balance being Al and unavoidable impurities, and the cladding material 2 including an aluminum alloy that includes 3 to 13% of Si, and limited to 0.05% or less of Cu, with the balance being Al and unavoidable impurities, wherein the Si content X (%) in the cladding material 1 and the Si content Y (%) in the cladding material 2 satisfy the value (YX) is 1.5 to 9%.

Claims

1. An aluminum alloy clad material for heat exchangers in which an aluminum alloy part thereof is a three-layer clad material that comprises: a core material, a first cladding material, and a second cladding material, one side of the core material being directly clad with the first cladding material, the other side of the core material being directly clad with the second cladding material, the core material comprising an aluminum alloy that consists of 0.5 to 1.8 mass % of Mn, limited to 0.05 mass % or less of Cu, and optionally 0.5 mass % or less of Mg, with the balance being Al and unavoidable impurities, the first cladding material comprising an aluminum alloy that consists of 0.3 to 1.8 mass % of Mn, 3 to 10 mass % of Si, 1 to 10 mass % of Zn, optionally 0.005 to 0.05% mass % of Sr, optionally 0.001 to 0.10 mass % of In, optionally 0.001 to 0.10 mass % of Sn, and optionally less than 0.05 mass % of Ni, with the balance being Al and unavoidable impurities, and the second cladding material comprising an aluminum alloy that consists of 3 to 13 mass % of Si, and limited to 0.05 mass % or less of Cu, and optionally 0.005 to 0.05 mass % of Sr, with the balance being Al and unavoidable impurities, wherein an Si content X (%) in the first cladding material and an Si content Y (%) in the second cladding material satisfy a value (YX) is 1.5 to 9%, and the aluminum alloy clad material is used in a state in which the first cladding material comes on the air side, wherein the first cladding material has a composition which is different than a composition of the second cladding material.

2. The aluminum alloy clad material according to claim 1, wherein 0.5 mass % or less of Mg is present in the core material.

3. The aluminum alloy clad material according to claim 1, wherein 0.005 to 0.05 mass % of Sr is present in the first cladding material.

4. The aluminum alloy clad material according to claim 1, wherein either or both of 0.001 to 0.10 mass % of In and 0.001 to 0.10 mass % of Sn are present in the first cladding material.

5. The aluminum alloy clad material according to claim 1, wherein Ni in a content of less than 0.05 mass % is present in the first cladding material.

6. The aluminum alloy clad material according to claim 1, wherein 0.005 to 0.05 mass % of Sr is present in the second cladding material.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic view illustrating a three-layer clad material according to one embodiment of the invention.

(2) FIG. 2 is a schematic view illustrating a refrigerant tube that is formed using a three-layer clad material.

(3) FIG. 3 is a schematic view illustrating another refrigerant tube that is formed using a three-layer clad material.

(4) FIG. 4 is a view illustrating the state (before brazing) of an inverted-T test specimen used for a brazing test.

(5) FIG. 5 is a view illustrating the state (after brazing) of an inverted-T test specimen used for a brazing test.

(6) FIG. 6 is a view illustrating the state (before brazing) of a specimen used for a corrosion test A.

(7) FIG. 7 is a view illustrating the state (before brazing) of a specimen used for a corrosion test B.

DESCRIPTION OF EMBODIMENTS

(8) As illustrated in FIG. 1, a three-layer aluminum alloy clad material according to one embodiment of the invention is a material in which one side of a core material 3 is clad with a cladding material 1, and the other side of the core material 3 is clad with a cladding material 2. For example, when a refrigerant tube is produced using the clad material, the clad materials according to one embodiment of the invention are formed so that the cladding material 1 forms a convex surface, and the cladding material 2 forms a concave surface, assembled so that the concave surfaces face each other, and subjected to brazing to form a plurality of refrigerant passages 4 (see FIG. 2) (first embodiment). When the refrigerant tube has been completed, the cladding material 1 comes on the air side, and the cladding material 2 comes in contact with a refrigerant so that heat is exchanged between the refrigerant and the air. Although FIG. 2 illustrates an example in which the refrigerant tube includes a plurality of refrigerant passages 4, the refrigerant tube may include only one refrigerant passage 4.

(9) As illustrated in FIG. 3 (second embodiment), the clad materials according to one embodiment of the invention may be formed so that the cladding material 1 forms a convex surface, and the cladding material 2 forms a concave surface, assembled so that the concave surfaces face each other, and subjected to brazing to form a refrigerant tube. When the refrigerant tube has been completed, the cladding material 1 comes on the air side, and the cladding material 2 comes in contact with a refrigerant so that heat is exchanged between the refrigerant and the air. As illustrated in FIG. 3, a corrugated bare fin 5 may be placed within the refrigerant passage 4.

(10) The clad materials illustrated in FIG. 2 may be combined so that the convex surfaces face each other, and the end of the lower clad material may be bent in the shape of the character U so as to engage with the horizontal end of the upper clad material, followed by brazing to form the end of the refrigerant tube (third embodiment).

(11) The effect of each alloy component included in the aluminum alloy clad material according to the embodiments of the invention, and the reason that the content of each alloy component in the aluminum alloy clad material is limited as described above, are described below.

(12) Core Material

(13) Mn

(14) Mn improves the strength of the core material. The Mn content in the core material is preferably 0.5 to 1.8%. If the Mn content in the core material is less than 0.5%, the strength of the core material may not be sufficiently improved. If the Mn content in the core material exceeds 1.8%, deterioration in rolling workability may occur. The Mn content in the core material is more preferably 1.0 to 1.7%.

(15) Cu

(16) The Cu content in the core material is limited to 0.05% or less. When the core material is clad with a sacrificial anode material (e.g., AlZn-based alloy or AlSiZn-based alloy), a high sacrificial anode effect is obtained after brazing by reducing the Cu content in the core material. If the Cu content in the core material exceeds 0.05%, the potential of the external surface cladding material may increase due to diffusion of Cu into the external surface cladding material during brazing, whereby the sacrificial anode effect may decrease. The Cu content in the core material is preferably 0.03% or less.

(17) Mg

(18) Mg improves the strength of the core material. However, Mg diffuses from the core material into the filler metal during brazing, and reacts with a fluoride flux applied to the surface of the core material to form a compound having a high melting point. This decreases the activity of the flux, whereby brazability deteriorates. If the Mg content in the core material exceeds 0.5%, the above phenomenon may occur significantly. Therefore, the Mg content in the core material is limited to 0.5% or less. The Mg content in the core material is preferably 0.3% or less.

(19) The core material normally includes about 0.1 to 0.2% of Fe as an unavoidable impurity. The Fe content in the core material may be reduced to 0.1% or less in order to further improve the corrosion resistance of the core material. Alternatively, 1.0% or less of Fe may be added to the core material in order to improve the strength of the core material. The advantageous effects of the invention are not impaired even when the core material includes 0.3% or less of V, 0.3% or less of Mo, 0.3% or less of Ni, 0.1% or less of Pb, 0.1% or less of Li, 0.1% or less of Ca, and 0.1% or less of Na. 0.3% or less of Ti may be added to the core material in order to refine the cast structure, and 0.1% or less of B may be added to the core material in order to prevent oxidation. 0.1% or less of Sr may also be added to the core material. Sr diffuses into the filler metal to promote refinement of the solidified structure of the filler metal. The advantageous effects of the invention are not impaired even when the core material includes about 0.4% or less of Si as an unavoidable impurity.

(20) Cladding Material 1 (External Surface Cladding Material)

(21) Si

(22) When an appropriate amount of Si is added to the external surface cladding material, a small amount of liquid filler is formed in the external surface cladding material, and a bare fin material or an aluminum sheet material can be jointed to the external surface cladding material. The Si content in the external surface cladding material is preferably 3 to 10%. If the Si content in the external surface cladding material is less than 3%, a sufficient liquid filler may not be formed, and a sufficient fillet may not be formed at the joint between the external surface cladding material and a bare fin material or an aluminum sheet material. If the Si content in the external surface cladding material exceeds 10%, most of the external surface cladding material may be melted, and Zn added to the external surface cladding material may also flow during brazing. As a result, the external surface cladding material may not serve as a sacrificial anode material. The Si content in the external surface cladding material is more preferably 3.5 to 8.5%.

(23) Zn

(24) Zn included in the external surface cladding material diffuses into the core material during brazing to form a Zn concentration gradient in the core material along the thickness direction. The potential of the external surface cladding material thus becomes lower than that of the core material, and the external surface cladding material serves as a sacrificial anode material to suppress the progress of corrosion in the thickness direction. The external surface cladding material used in connection with the invention includes Si. Si increases the potential of the external surface cladding material upon dissolution to counterbalance the potential-decreasing effect of Zn. Since Zn is included in the liquid filler that is formed due to the addition of Si, the amount of residual Zn decreases. The Zn content in the external surface cladding material is preferably 1 to 10%. If the Zn content in the external surface cladding material is less than 1%, a sufficient potential-decreasing effect may not be obtained. If the Zn content in the external surface cladding material exceeds 10%, a sufficient potential-decreasing effect is obtained, but a fillet formed at the joint may be corroded in the short time. The Zn content in the external surface cladding material is more preferably 2 to 9%.

(25) Mn

(26) The external surface cladding material used in connection with the invention includes Si, and part of Si included in the external surface cladding material is melted during brazing to form a solidified structure. Therefore, the external surface cladding material includes a primary phase and a eutectic phase. Since the potential of the eutectic phase is lower than that of the primary phase, the eutectic phase is preferentially corroded as compared with the primary phase. If the eutectic phase is corroded, the primary phase is isolated, and falls off. If the primary phase that has a sacrificial anode effect falls off, the sacrificial anode material disappears without exerting the sacrificial anode effect. Therefore, the core material is corroded in the short time, and perforation corrosion occurs. In order to suppress the above phenomenon, it is necessary to coarsen the primary phase so that the primary phase does not easily fall off even when the eutectic phase has been preferentially corroded, and form a low-potential area in the primary phase. Since the primary phase is coarsened by adding Mn to the external surface cladding material, it is possible to suppress a situation in which the primary phase falls off. Moreover, an AlMnSi-based compound is formed in the primary phase, and an Mn/Si-deficient layer that is formed around the AlMnSi-based compound serves as a low-potential area, so that the preferential corrosion of the eutectic phase is relatively suppressed. The Mn content in the external surface cladding material is preferably 0.3 to 1.8%. If the Mn content in the external surface cladding material is less than 0.3%, a sufficient effect may not be obtained. If the Mn content in the external surface cladding material exceeds 1.8%, the Si concentration in the external surface cladding material may significantly decrease due to formation of an AlMnSi compound, whereby the amount of liquid filler to be formed may decrease. The Mn content in the external surface cladding material is more preferably 0.3 to 1.3%.

(27) Sr

(28) Sr finely disperses the Si particles included in the external surface cladding material, so that the liquid filler of a molten filler metal formed during brazing are easily jointed to each other. This makes it possible to improve the fluidity of the liquid filler, and achieve excellent brazability. The Sr content in the external surface cladding material is preferably 0.005 to 0.05%. If the Sr content in the external surface cladding material is less than 0.005%, a sufficient effect may not be obtained. If the Sr content in the external surface cladding material exceeds 0.05%, a coarse AlSiSr-based compound may be produced, and the effect may deteriorate.

(29) In and Sn

(30) A potential-decreasing effect is obtained by adding a small amount of In and Sn. Therefore, the potential of the external surface cladding material becomes lower than that of the core material by adding In and Sn to the external surface cladding material, so that a sacrificial anode effect can be obtained. The In content and the Sn content in the external surface cladding material are preferably 0.001 to 0.10%, respectively. If the In content and the Sn content in the external surface cladding material are less than 0.001%, a sufficient effect may not be obtained. If the In content and the Sn content in the external surface cladding material exceed 0.10%, deterioration in self-corrosion resistance may occur. The In content and the Sn content in the external surface cladding material are more preferably 0.01 to 0.04%, respectively.

(31) Ni

(32) Ni forms an AlNi-based compound. Since the AlNi-based compound serves as a cathode, the self-corrosion resistance of the external surface cladding material (sacrificial anode material) decreases, whereby corrosion is promoted, and perforation corrosion occurs in the short time. The above phenomenon may occur significantly when the Ni content in the external surface cladding material is 0.05% or more. Therefore, the Ni content in the external surface cladding material is preferably limited to less than 0.05%.

(33) The external surface cladding material includes about 0.1 to 0.2% of Fe as an unavoidable impurity. The Fe content in the external surface cladding material may be reduced to 0.1% or less in order to further improve the corrosion resistance of the external surface cladding material. Alternatively, 1.0% or less of Fe may be added to the external surface cladding material in order to improve the strength of the external surface cladding material. The advantageous effects of the invention are not impaired even when the external surface cladding material includes 0.3% or less of V, 0.3% or less of Mo, 0.1% or less of Pb, 0.1% or less of Li, 0.1% or less of Ca, and 0.1% or less of Na. 0.1% or less of B may be added to the external surface cladding material in order to prevent oxidation.

(34) Cladding Material 2 (Internal Surface Cladding Material)

(35) Si

(36) When the clad material according to the exemplary embodiments of the invention is used as a refrigerant tube, it is necessary to form a refrigerant passage by assembling the formed clad materials so as to face each other, or jointing the formed clad material to another member (see FIGS. 2 and 3). Therefore, it is necessary to add Si to the internal surface cladding material to obtain an ordinary AlSi-based alloy filler metal. The Si content in the internal surface cladding material is preferably 3 to 13%. If the Si content in the internal surface cladding material is less than 3%, a sufficient amount of filler metal may not be melted, and the internal surface cladding material may not sufficiently serve as a filler metal. If the Si content in the internal surface cladding material exceeds 13%, primary-phase Si may be crystallized, and it may be difficult to produce a sound material.

(37) When a refrigerant passage is formed by assembling the formed clad materials so as to face each other, a molten filler metal may flow during brazing from the external surface cladding material that includes Zn toward the joint, and the joint may be preferentially corroded. In this case, when the Si content in the internal surface cladding material is increased, a molten filler metal flows during brazing from the internal surface cladding material toward the joint, and it is possible to suppress a situation in which a molten filler metal that flows from the external surface cladding material that includes Zn is concentrated at the joint, and the joint is preferentially corroded. However, if the Si concentration in the internal surface cladding material is too high, a molten filler metal flows from the internal surface cladding material toward the external surface, and the Zn concentration in the external surface filler metal decreases, whereby the Zn concentration in the vicinity of the joint significantly decreases after brazing, and a sufficient sacrificial anode effect is not obtained.

(38) It was found that it is possible to suppress a situation in which the joint is preferentially corroded, and obtain a sacrificial anode effect in the vicinity of the joint, when the Si content X (%) in the external surface cladding material (filler metal) and the Si content Y (%) in the internal surface cladding material (filler metal) satisfy the value (YX) is 1.5 to 9%. If the value (YX) is less than 1.5%, Zn included in the external surface cladding material (filler metal) may be concentrated at the joint, and the joint may be preferentially corroded. When the value (YX) is 1.5 to 0%, Zn included in the external surface cladding material (filler metal) may flow toward the joint, but the joint is not preferentially corroded since the Zn concentration at the joint is lower than the external surface Zn concentration. The value (YX) is more preferably 0 to 8.5%, still more preferably 0.2 to 7.5%, and most preferably 0.5 to 6.5%, in order to prevent a situation in which Zn flows toward the joint.

(39) Sr

(40) Sr finely disperses the Si particles included in the internal surface cladding material, so that the liquid filler of a molten filler metal formed during brazing are easily jointed to each other. This makes it possible to improve the fluidity of the liquid filler, and achieve excellent brazability. The Sr content in the internal surface cladding material is preferably 0.005 to 0.05%. If the Sr content in the internal surface cladding material is less than 0.005%, a sufficient effect may not be obtained. If the Sr content in the internal surface cladding material exceeds 0.05%, a coarse AlSiSr-based compound may be produced, and the effect may deteriorate.

(41) Cu

(42) When the internal surface cladding material includes Cu, Cu included in the internal surface cladding material (filler metal) may move to the outer surface (may be scattered on the outer surface) in an area in which the internal surface cladding material and the external surface cladding material are situated close to each other (see the second embodiment (see FIG. 3) and the third embodiment) due to the flow of a molten filler metal from the internal surface cladding material during brazing. In this case, the Cu-containing area having a potential-increasing effect may serve as a cathode, and promote corrosion in the peripheral area. The above phenomenon significantly occurs when the Cu content in the internal surface cladding material exceeds 0.05%. Therefore, the Cu content in the internal surface cladding material is preferably limited to 0.05% or less, and more preferably 0.03% or less.

(43) The internal surface cladding material normally includes about 0.1 to 0.2% of Fe as an unavoidable impurity. The Fe content in the internal surface cladding material may be reduced to 0.1% or less in order to further improve the corrosion resistance of the internal surface cladding material. Alternatively, 1.0% or less of Fe may be added to the internal surface cladding material in order to improve the strength of the internal surface cladding material. The advantageous effects of the invention are not impaired even when the internal surface cladding material includes 0.3% or less of V, 0.3% or less of Mo, 0.3% or less of Ni, 0.1% or less of Pb, 0.1% or less of Li, 0.1% or less of Ca, and 0.1% or less of Na. 0.1% or less of B may be added to the internal surface cladding material in order to prevent oxidation.

(44) The clad material according to one embodiment of the invention is produced by subjecting each of an aluminum alloy for producing the core material, an aluminum alloy for producing the cladding material 1 (external surface cladding material), and an aluminum alloy for producing the cladding material 2 (internal surface cladding material), to continuous casting, homogenizing the resulting ingot according to an ordinary method, hot-rolling the ingot of the aluminum alloy for producing the cladding material 1, and the ingot of the aluminum alloy for producing the cladding material 2, cladding the ingot of the aluminum alloy for producing the core material with the ingot of the aluminum alloy for producing the cladding material 1, and the ingot of the aluminum alloy for producing the cladding material 2, and subjecting the resulting laminate to hot clad rolling, optional process inter-annealing, cold rolling, and final annealing.

EXAMPLES

(45) The invention is further described below by way of examples and comparative examples to demonstrate the advantageous effects of the invention. Note that the following examples are provided for illustration purposes only, and the invention is not limited thereto.

Example 1

(46) Each of an aluminum alloy for producing an external surface cladding material (cladding material 1) having the composition shown in Table 1, an aluminum alloy for producing a core material having the composition shown in Table 1, and an aluminum alloy for producing an internal surface cladding material (cladding material 2) having the composition shown in Table 1, was subjected to continuous casting, and the resulting ingot was homogenized according to an ordinary method. The ingot of the aluminum alloy for producing the cladding material 1, and the ingot of the aluminum alloy for producing the cladding material 2 were hot-rolled, and placed on the ingot of the aluminum alloy for producing the core material according to the combination shown in Table 1 so that the thickness ratio of the cladding material 1, the core material, and the cladding material 2 was 10%/80%/10%. The resulting laminate was subjected to hot clad rolling, cold rolling, optional process annealing, and final annealing to produce a three-layer clad material (O-temper material) having a thickness of 0.30 mm.

(47) The resulting clad material was subjected to the following Tests 1 to 5. The test results are listed in Table 2.

(48) Test 1: Tensile Test

(49) The clad material was cut to have a size of 100250 mm. About 5 g/m.sup.2 of a fluoride-based flux was applied to each side of the clad material, and dried. The clad material was then subjected to brazing by heating the clad material to 600 C. (maximum temperature) in a nitrogen gas atmosphere at an average heating rate of 50 C./min. A JIS Z 2201 No. 5 specimen was prepared using the clad material, and subjected to a tensile test at room temperature in accordance with JIS Z 2241. A case where the tensile strength was more than 70 MPa was evaluated as Good, and a case where the tensile strength was 70 MPa or less was evaluated as Bad.

(50) Test 2: Inverted-T Test

(51) The clad material was cut to have a size of 2550 mm, and subjected to an inverted-T test for evaluating brazability (horizontal plate: cladding material 2, vertical plate: 3003 alloy sheet (25501.0 (thickness) mm, O-temper)) (see FIGS. 4 and 5). The jointed sample was buried in a resin, and the cross-sectional area of a fillet formed at the joint with the vertical plate was measured. The ratio of the cross-sectional area of the fillet after brazing to the cross-sectional area of the cladding material 2 before brazing was calculated, and taken as the flow factor determined by the inverted-T test. A case where the flow factor was 0.15 or more was evaluated as Good, and a case where the flow factor was less than 0.15 was evaluated as Bad.

(52) Test 3: Mini-Core Test

(53) The clad material was cut to have a size of 25100 mm. A corrugated bare fin material (fin height: 10 mm, fin pitch: 4 mm) made of a 3003 alloy (thickness: 0.07 mm, H14 temper) was placed between two clad materials, and the laminate was secured using a jig so that the cladding material 1 was situated to be jointed to the fin material. About 5 g/m.sup.2 of a fluoride-based flux was sprayed onto the jointing area, and dried. The laminate was then brazed by heating the laminate to 600 C. (maximum temperature) in a nitrogen gas atmosphere at an average heating rate of 50 C./min. The sample that was jointed in the shape of a mini-core was buried in a resin, and the cross-sectional area of a fillet formed at the joint with the fin was measured. The ratio of the cross-sectional area of the fillet after brazing to the cross-sectional area of the cladding material 1 before brazing was calculated, and taken as the flow factor determined by the mini-core test. The brazability was evaluated as Good when the flow factor was 0.05 or more, and was evaluated as Bad when the flow factor was less than 0.05.

(54) Test 4: Corrosion Test a

(55) The clad material was cut to have a size of 5050 mm, and two clad materials were secured using a jig so that the cladding material 1 and the cladding material 2 overlapped each other by 10 mm (see FIG. 6). About 5 g/m.sup.2 of a fluoride-based flux was applied to each side of the clad materials, and dried. The clad materials were then brazed by heating the clad materials to 600 C. (maximum temperature) in a nitrogen gas atmosphere at an average heating rate of 50 C./min. After masking the cladding material 2 (including the end face), the sample was subjected to a SWAAT test (ASTM-G85-A3) for 8 weeks in order to evaluate corrosion resistance. The corrosion resistance was evaluated as Good when perforation corrosion from the cladding material 1 did not occur, and was evaluated as Bad when perforation corrosion from the cladding material 1 occurred. The corrosion resistance was evaluated as Good when separation due to corrosion did not occur at the joint when 8 weeks had elapsed, and was evaluated as Bad when separation due to corrosion occurred at the joint.

(56) Test 5: Corrosion Test B

(57) The clad material was cut to have a size of 2550 mm, and pressed. About 5 g/m.sup.2 of a fluoride-based flux was applied to each side of the clad material, and dried. Two clad materials were placed so that the cladding materials 2 (non-pressed area) overlapped each other by 2 mm (see FIG. 7), a 3003 alloy sheet (thickness: 1.00 mm, O-temper) was brought into contact with each cladding material 1 (pressed area), and the laminate specimen was secured using a jig. The laminate specimen was then brazed by heating the laminate specimen to 600 C. (maximum temperature) in a nitrogen gas atmosphere at an average heating rate of 50 C./min. After masking the joint between the 3003 alloy sheet and the cladding material 1, the 3003 alloy sheet, and the cladding material 2 (including the end face) so that only the joint between the cladding materials 2 and the cladding material 1 were exposed, the laminate specimen was subjected to a SWAAT test (ASTM-G85-A3) for 8 weeks in order to evaluate corrosion resistance. The corrosion resistance was evaluated as Good when perforation corrosion from the cladding material 1 did not occur, and was evaluated as Bad when perforation corrosion from the cladding material 1 occurred. The corrosion resistance was evaluated as Excellent (5) when separation due to corrosion did not occur at the joint when 8 weeks had elapsed, and less than 10% of the cross-sectional area of the joint was corroded, was evaluated as Very good (4) when 10 to 20% of the cross-sectional area of the joint was corroded, was evaluated as Good (3) when 20 to 30% of the cross-sectional area of the joint was corroded, was evaluated as Fair (2) when 30 to 50% of the cross-sectional area of the joint was corroded, was evaluated as Almost separated (1) when 50 to 100% of the cross-sectional area of the joint was corroded, and was evaluated as Bad when separation due to corrosion occurred at the joint.

(58) TABLE-US-00001 TABLE 1 Cladding material 1 Cladding material 2 Composition (mass %) Core material Composition (mass %) Clad Si Composition (mass %) Si Y-X material (X) Zn Mn Sr In Sn Ni Other Cu Mn Mg Other (Y) Sr Cu Other (%) 1 3 4 1 0.05 1.2 3 0 2 10 4 1 0.5 13 3 3 5 1 1 1.8 8 0.01 3 4 5 10 1 8 0.05 3 5 5 4 0.3 8 0.05 3 6 5 4 1.8 1.2 0.5 8 0.03 3 7 5 4 1 0.01 0.03 1.2 5 0 8 5 4 1 0.05 1.1 5.2 0.2 9 5 5 1 1.7 5.5 0.5 10 5 6 1 1.2 0.3 6 1 11 5 4 1 0.001 1.3 6.5 1.5 12 5 4 1 0.1 1.4 7 2 13 5 4 1 0.001 1.2 7.5 2.5 14 5 4 1 0.1 1.2 8.5 3.5 15 3.5 4 1 0.04 1.2 10 6.5 16 3.5 4 1 1.2 11 7.5 17 8.5 4 1 1.2 8.5 0 18 5 2 1 1.2 12 7 19 5 9 1 1.2 8.5 3.5 20 4 4 1.3 1.2 12.7 8.7 21 5 4 1 0.04 1.2 8.5 3.5 22 5 4 1 0.04 1.2 8.5 3.5 23 5 4 1 0.8 8.5 3.5 24 6 4 1 1.5 8.5 2.5 25 7 4 1 Fe: 0.1 1.2 Fe: 0.1 8.5 Fe: 0.1 1.5 26 5 4 1 Fe: 1.0 1.2 Fe: 1.0 9 Fe: 1.0 4 27 6 4 1 1.2 Ni: 0.1 9.5 Ni: 0.1 3.5 28 7 4 1 Pb: 0.1 1.2 Pb: 0.1 10 Pb: 0.1 3 29 4 4 1 Li: 0.1 1.2 Li: 0.1 12.5 Li: 0.1 8.5 30 5.5 4 1 Ca: 0.1 1.2 Ca: 0.1 13 Ca: 0.1 7.5 31 4 4 1 Na: 0.1 1.2 Na: 0.1 13 Na: 0.1 9 32 8.5 4 1 B: 0.1 1.2 B: 0.1 7 B: 0.1 1.5 33 8.5 3 1 1.2 7.5 1 34 8.5 4 1 1.2 8.5 0 35 8.5 9 1 1.2 9 0.5 36 8.5 4 1 1.2 7.5 1 37 8.5 4 1 1.2 8.5 0 38 5 4 1 0.01 1.2 9 4 39 4.5 4 1 0.01 1.2 11 6.5 40 4.5 4 1 0.01 1.2 12 7.5 41 3.5 4 1 0.01 1.2 11.5 8 42 4 4 0.2 3 1 43 5 4 1 0.03 1.2 8 0.01 3 44 5 4 1 0.01 1.1 8 0.05 3

(59) TABLE-US-00002 TABLE 2 Test 4 Test 5 Whether or Test 1 Test 2 Test 3 Corrosion test A Corrosion test B not clad Tensile Inverted-T Mini-core Perforation Separation Perforation Separation material Clad strength test (flow test (flow after at joint after at joint could be material (>70 MPa) factor 0.15) factor 0.05) 8 weeks after 8 weeks 8 weeks after 8 weeks produced 1 Good Good Good Good Good Good 3 Good 2 Good Good Good Good Good Good 5 Good 3 Good Good Good Good Good Good 5 Good 4 Good Good Good Good Good Good 5 Good 5 Good Good Good Good Good Good 5 Good 6 Good Good Good Good Good Good 5 Good 7 Good Good Good Good Good Good 3 Good 8 Good Good Good Good Good Good 4 Good 9 Good Good Good Good Good Good 5 Good 10 Good Good Good Good Good Good 5 Good 11 Good Good Good Good Good Good 5 Good 12 Good Good Good Good Good Good 5 Good 13 Good Good Good Good Good Good 5 Good 14 Good Good Good Good Good Good 5 Good 15 Good Good Good Good Good Good 5 Good 16 Good Good Good Good Good Good 4 Good 17 Good Good Good Good Good Good 3 Good 18 Good Good Good Good Good Good 4 Good 19 Good Good Good Good Good Good 5 Good 20 Good Good Good Good Good Good 2 Good 21 Good Good Good Good Good Good 5 Good 22 Good Good Good Good Good Good 5 Good 23 Good Good Good Good Good Good 5 Good 24 Good Good Good Good Good Good 5 Good 25 Good Good Good Good Good Good 5 Good 26 Good Good Good Good Good Good 5 Good 27 Good Good Good Good Good Good 5 Good 28 Good Good Good Good Good Good 5 Good 29 Good Good Good Good Good Good 3 Good 30 Good Good Good Good Good Good 4 Good 31 Good Good Good Good Good Good 2 Good 32 Good Good Good Good Good Good 2 Good 33 Good Good Good Good Good Good 2 Good 34 Good Good Good Good Good Good 3 Good 35 Good Good Good Good Good Good 5 Good 36 Good Good Good Good Good Good 2 Good 37 Good Good Good Good Good Good 3 Good 38 Good Good Good Good Good Good 5 Good 39 Good Good Good Good Good Good 5 Good 40 Good Good Good Good Good Good 4 Good 41 Good Good Good Good Good Good 3 Good 42 Good Good Good Good Good Good 2 Good 43 Good Good Good Good Good Good 5 Good 44 Good Good Good Good Good Good 5 Good

(60) As shown in Table 2, Specimens 1 to 44 according to the invention had a tensile strength of more than 70 MPa or more after brazing, a flow factor (cladding material 2) determined by the inverted-T test of 0.15 or more, and a flow factor (cladding material 2) determined by the mini-core test of 0.05 or more. Perforation corrosion and separation due to corrosion did not occur when Specimens 1 to 44 were subjected to the SWAAT test for 8 weeks (i.e., Specimens 1 to 44 exhibited excellent brazability and excellent corrosion resistance).

Comparative Example 1

(61) Each of an aluminum alloy for producing an external surface cladding material (cladding material 1) having the composition shown in Table 3, an aluminum alloy for producing a core material having the composition shown in Table 3, and an aluminum alloy for producing an internal surface cladding material (cladding material 2) having the composition shown in Table 3, was subjected to continuous casting, and the resulting ingot was processed in the same manner as in Example 1 to produce a three-layer clad material (O-temper material) having a thickness of 0.30 mm. The clad material was subjected to Tests 1 to 5 in the same manner as in Example 1 to evaluate the brazability and the corrosion resistance. The test results are shown in Table 4. In Table 3, the values that fall outside the scope of the invention are underlined.

(62) TABLE-US-00003 TABLE 3 Cladding material 2 Cladding material 1 Core material Composition Composition (mass %) Composition (mass %) Clad Si (mass %) Si Y-X material (X) Zn Mn Sr In Sn Ni Cu Mn Mg (Y) Sr Cu (%) 45 3 4 1 1.2 12.2 9.2 46 3.5 4 1 1.2 13 9.5 47 8.5 4 1 1.2 3 5.5 48 8.5 4 1 1.2 5 3.5 49 8.5 4 1 1.2 6.5 2 50 3 4 1 1.2 12.3 9.3 51 3 4 1 1.2 12.5 9.5 52 3 4 1 1.2 12.7 9.7 53 3 4 1 1.2 13 10 54 2 4 1 0.05 1.2 2 0 55 4 4 1 0.5 14 10 56 3 0.5 1 1.8 2 0.06 1 57 5 11 1 8.5 3.5 58 3.5 4 2 1.2 0.5 13 9.5 59 5 4 1 0.0005 0.1 1.2 5 0 60 5 4 1 0.15 1.2 5.2 0.2 61 5 4 1 0.0005 0.4 5.5 0.5 62 5 4 1 0.15 1.2 6 1 63 5 4 1 0.06 1.2 6.5 1.5 64 5 4 1 1.9 7 2 65 5 4 1 1.2 0.6 9 4 66 11 4 1 0.05 1.2 4 7 67 5 4 1 0.01 0.05 1.2 8 3

(63) TABLE-US-00004 TABLE 4 Test 4 Test 5 Whether Test 1 Test 2 Test 3 Corrosion test A Corrosion test B or not clad Tensile Inverted-T Mini-core Separation Separation material Clad strength test (flow test (flow Perforation at joint Perforation at joint could be material (>70 MPa) factor 0.15) factor 0.05) after 8 weeks after 8 weeks after 8 weeks after 8 weeks produced 45 Good Good Good Good Good Bad 5 Good 46 Good Good Good Good Good Bad 5 Good 47 Good Good Good Good Good Good Bad Good 48 Good Good Good Good Good Good Bad Good 49 Good Good Good Good Good Good 1 Good 50 Good Good Good Good Goad Bad 5 Good 51 Good Good Good Good Good Bad 5 Good 52 Good Good Good Good Good Bad 5 Good 53 Good Good Good Good Good Bad 5 Good 54 Good Bad Bad Good Good Good 3 Good 55 Bad 56 Good Bad Good Bad Good Bad 2 Good 57 Good Good Good Good Bad Good 5 Good 58 Good Good Bad Good Good Bad 5 Good 59 Good Good Good Bad Good Bad 3 Good 60 Good Good Good Bad Bad Bad 4 Good 61 Bad Good Good Good Good Good 5 Good 62 Good Good Good Bad Bad Bad 5 Good 63 Good Good Good Bad Goad Bad 5 Good 64 Bad 65 Good Bad Bad Good 66 Good Good Good Bad Good Bad Bad Good 67 Good Good Good Bad Good Bad 5 Good

(64) As shown in Table 4, Specimens 45, 46, 50, 51, 52, and 53 in which the difference (YX) between the Si content in the cladding material 1 and the Si content in the cladding material 2 was large, exhibited insufficient corrosion resistance, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks (Test 5 (corrosion test B)), since the liquid filler metal flowed from the cladding material 2 toward the cladding material 1, and the surface Zn concentration in the cladding material 1 decreased. Specimens 47, 48, and 49 in which the value (YX) was small, showed separation at the joint when the specimen was subjected to the SWAAT test for 8 weeks (Test 5 (corrosion test B)), since Zn was concentrated at the joint.

(65) Specimen 54 had a flow factor determined by the mini-core test of less than 0.05 since the Si concentration in the cladding material 1 was low, and had a flow factor determined by the inverted-T test of less than 0.15 since the Si concentration in the cladding material 2 was low. Specimen 55 showed significant edge cracking during rolling (i.e., a clad material could not be produced) since the Si concentration in the cladding material 2 was high, and primary-phase Si was crystallized.

(66) Specimen 56 exhibited insufficient corrosion resistance since the Zn concentration in the cladding material 1 was low, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Specimen 56 had a flow factor determined by the inverted-T test of less than 0.15 since the Si concentration in the cladding material 2 was low. The Si particles included in the cladding material 2 were not refined during brazing since the Sr concentration in the cladding material 2 was high. When Specimen 57 was subjected to the SWAAT test for 8 weeks (Test 4 (corrosion test A)), Zn was concentrated in the fillet, and separation occurred at the joint, since the Zn concentration in the cladding material 1 was high.

(67) Specimen 58 had a flow factor determined by the mini-core test of less than 0.05 since the Mn concentration in the cladding material 1 was high. Specimen 59 exhibited insufficient corrosion resistance due to diffusion of Cu into the cladding material 1 since the Cu concentration in the core material was high, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Specimen 60 had a problem in that the corrosion rate of the cladding material 1 was high since the In concentration in the cladding material 1 was high, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Moreover, the joint was significantly corroded, and separation occurred when the specimen was subjected to the SWAAT test for 8 weeks.

(68) Specimen 61 had a tensile strength of 70 MPa or less since the Mn concentration in the core material was low. Specimen 62 had a problem in that the corrosion rate of the cladding material 1 was high since the Sn concentration in the cladding material 1 was high, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Moreover, the joint was significantly corroded, and separation occurred when the specimen was subjected to the SWAAT test for 8 weeks. Specimen 63 had a problem in that the corrosion rate of the cladding material 1 was high since the Ni concentration in the cladding material 1 was high, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Specimen 64 showed significant edge cracking during rolling (i.e., a clad material could not be produced) since the Mn concentration in the core material was high.

(69) Specimen 65 could not be brazed since the Mg concentration in the core material was high, and had a flow factor determined by the mini-core test of less than 0.05. Specimen 65 had a flow factor determined by the inverted-T test of less than 0.15. Moreover, the SWAAT test could not be performed since a joint could not obtained by brazing. Specimen 66 had a problem in that Zn flowed during brazing, and could not serve as a sacrificial anode material since the Si concentration in the cladding material 1 was high, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks. Moreover, Zn was concentrated at the joint, and separation occurred at the joint when the specimen was subjected to the SWAAT test for 8 weeks (Test 5 (corrosion test B)). Specimen 67 exhibited insufficient corrosion resistance since the Cu concentration in the cladding material 2 was high, and Cu flowed toward the surface of the cladding material 1, and perforation corrosion occurred when the specimen was subjected to the SWAAT test for 8 weeks.

REFERENCE SIGNS LIST

(70) 1 Cladding material 1 2 Cladding material 2 3 Core material 4 Refrigerant passage 5 Bare fin