ALUMINUM ALLOY BRAZING SHEET AND BRAZING METHOD

Abstract

An aluminum alloy brazing sheet exhibits excellent brazability by effectively weakening an oxide film formed on the surface of a filler metal. The aluminum alloy brazing sheet includes a core material and a filler metal, and is used to braze aluminum in an inert gas atmosphere or in vacuum, the core material including aluminum or an aluminum alloy, the filler metal including 6 to 13 mass % of Si, with the balance being Al and unavoidable impurities, and one side or each side of the core material being clad with the filler metal, wherein the core material is clad with the filler metal in a state in which a sheet material is interposed between the core material and the filler metal, the sheet material including one element, or two or more elements, among 0.05 mass % or more of Li, 0.05 mass % or more of Be, 0.05 mass % or more of Ba, and 0.05 mass % or more of Ca, with the balance being Al and unavoidable impurities.

Claims

1. An aluminum alloy brazing sheet comprising a core material and a filler metal, and being used to braze aluminum in an inert gas atmosphere or in vacuum, the core material comprising aluminum or an aluminum alloy, the filler metal comprising 6 to 13 mass % of Si, with the balance being Al and unavoidable impurities, and one side or each side of the core material being clad with the filler metal, wherein the core material is clad with the filler metal in a state in which a sheet material is interposed between the core material and the filler metal, the sheet material comprising one element, or two or more elements, among 0.05 mass % or more of Li, 0.05 mass % or more of Be, 0.05 mass % or more of Ba, and 0.05 mass % or more of Ca, with the balance being Al and unavoidable impurities.

2. An aluminum alloy brazing sheet comprising a core material and a filler metal, and being used to braze aluminum in an inert gas atmosphere or in vacuum, the core material comprising aluminum or an aluminum alloy, the filler metal comprising 6 to 13 mass % of Si, with the balance being Al and unavoidable impurities, and one side or each side of the core material being clad with the filler metal, wherein the core material is clad with the filler metal in a state in which a sheet material and a sacrificial anode material are interposed between the core material and the filler metal so that the core material, the sacrificial anode material, the sheet material, and the filler metal are situated in this order, the sheet material comprising one element, or two or more elements, among 0.05 mass % or more of Li, 0.05 mass % or more of Be, 0.05 mass % or more of Ba, and 0.05 mass % or more of Ca, with the balance being Al and unavoidable impurities, and the sacrificial anode material comprising 0.9 to 6 mass % of Zn, with the balance being Al and unavoidable impurities.

3. An aluminum alloy brazing sheet comprising a core material, a filler metal, and a sacrificial anode material, and being used to braze aluminum in an inert gas atmosphere or in vacuum, the core material comprising aluminum or an aluminum alloy, the filler metal comprising 6 to 13 mass % of Si, with the balance being Al and unavoidable impurities, the sacrificial anode material comprising 0.9 to 6 mass % of Zn, with the balance being Al and unavoidable impurities, one side of the core material being clad with the filler metal, and the other side of the core material being clad with the sacrificial anode material, wherein the core material is clad with the filler metal in a state in which a sheet material is interposed between the core material and the filler metal, the sheet material comprising one element, or two or more elements, among 0.05 mass % or more of Li, 0.05 mass % or more of Be, 0.05 mass % or more of Ba, and 0.05 mass % or more of Ca, with the balance being Al and unavoidable impurities.

4. The aluminum alloy brazing sheet according to claim 1, wherein the sheet material further comprises 0.4 to 4.0 mass % of Mg.

5. The aluminum alloy brazing sheet according to claim 1, wherein the sheet material further comprises 2 to 13 mass % of Si.

6. The aluminum alloy brazing sheet according to claim 1, wherein the filler metal further comprises 0.004 to 0.2 mass % of Bi.

7. The aluminum alloy brazing sheet according to claim 1, wherein the core material that comprises the aluminum alloy comprises one element, or two or more elements, among 1.8 mass % or less of Mn, 1.2 mass % or less of Si, 1.0 mass % or less of Fe, 1.5 mass % or less of Cu, 0.8 mass % or less of Zn, 0.2 mass % or less of Ti, and 0.5 mass % or less of Zr, with the balance being Al and unavoidable impurities.

8. The aluminum alloy brazing sheet according to claim 7, wherein the core material that comprises the aluminum alloy further comprises 0.4 to 1.3 mass % of Mg.

9. A brazing method comprising effecting brazing in an inert gas atmosphere or in vacuum using the aluminum alloy brazing sheet according to claim 1 without applying a flux.

10. A brazing method comprising effecting brazing in an inert gas atmosphere using the aluminum alloy brazing sheet according to claim 1 in a state in which a fluoride-based flux is applied to the entirety or part of a brazing area in an amount of 1 to 20 g/m.sup.2.

11. The aluminum alloy brazing sheet according to claim 2, wherein the sheet material further comprises 0.4 to 4.0 mass % of Mg.

12. The aluminum alloy brazing sheet according to claim 2, wherein the sheet material further comprises 2 to 13 mass % of Si.

13. The aluminum alloy brazing sheet according to claim 2, wherein the filler metal further comprises 0.004 to 0.2 mass % of Bi.

14. The aluminum alloy brazing sheet according to claim 2, wherein the core material that comprises the aluminum alloy comprises one element, or two or more elements, among 1.8 mass % or less of Mn, 1.2 mass % or less of Si, 1.0 mass % or less of Fe, 1.5 mass % or less of Cu, 0.8 mass % or less of Zn, 0.2 mass % or less of Ti, and 0.5 mass % or less of Zr, with the balance being Al and unavoidable impurities.

15. The aluminum alloy brazing sheet according to claim 14, wherein the core material that comprises the aluminum alloy further comprises 0.4 to 1.3 mass % of Mg.

16. The aluminum alloy brazing sheet according to claim 3, wherein the sheet material further comprises 0.4 to 4.0 mass % of Mg.

17. The aluminum alloy brazing sheet according to claim 3, wherein the sheet material further comprises 2 to 13 mass % of Si.

18. The aluminum alloy brazing sheet according to claim 3, wherein the filler metal further comprises 0.004 to 0.2 mass % of Bi.

19. The aluminum alloy brazing sheet according to claim 3, wherein the core material that comprises the aluminum alloy comprises one element, or two or more elements, among 1.8 mass % or less of Mn, 1.2 mass % or less of Si, 1.0 mass % or less of Fe, 1.5 mass % or less of Cu, 0.8 mass % or less of Zn, 0.2 mass % or less of Ti, and 0.5 mass % or less of Zr, with the balance being Al and unavoidable impurities.

20. The aluminum alloy brazing sheet according to claim 19, wherein the core material that comprises the aluminum alloy further comprises 0.4 to 1.3 mass % of Mg.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is an external view illustrating a cup specimen that is used to evaluate brazability (see the examples).

[0031] FIG. 2 is a cross-sectional view illustrating a cup specimen.

DESCRIPTION OF EMBODIMENTS

[0032] An aluminum alloy brazing sheet according to a first embodiment of the invention includes a core material and a filler metal, and is used to braze aluminum in an inert gas atmosphere or in vacuum, the core material including aluminum or an aluminum alloy, the filler metal including 6 to 13% of Si, with the balance being Al and unavoidable impurities, and one side or each side of the core material being clad with the filler metal, wherein the core material is clad with the filler metal in a state in which a sheet material is interposed between the core material and the filler metal, the sheet material including one element, or two or more elements, among 0.05% or more of Li, 0.05% or more of Be, 0.05% or more of Ba, and 0.05% or more of Ca, with the balance being Al and unavoidable impurities. The filler metal with which the core material is clad has an Si content of 6 to 13%. If the Si content in the filler metal is less than 6%, brazability may deteriorate. If the Si content in the filler metal exceeds 13%, cracks may easily occur during material production, and it may be difficult to produce a brazing sheet.

[0033] Li, Be, Ba, and Ca that may be included in the sheet material that is interposed between the core material and the filler metal are diffused or dissolved in the filler metal during brazing (heating), and form an oxide within the aluminum oxide film that covers the surface of the filler metal. The oxide induces breakage of the aluminum oxide film, and significantly improves brazability. The sheet material has a function of supplying these elements to the filler metal.

[0034] If the content of Li, Be, Ba, and Ca in the sheet material is less than 0.05%, respectively, these elements may not be sufficiently diffused or dissolved in the filler metal, and may not induce breakage of the oxide film formed on the surface of the filler metal. The upper limit of the content of Li, Be, Ba, and Ca in the sheet material is preferably 1.5%. If the content of Li, Be, Ba, and Ca in the sheet material exceeds 1.5%, cracks may occur when the sheet material is produced by casting and rolling.

[0035] The sheet material may be produced by casting an alloy that includes one element, or two or more elements, among 0.05% or more of Li, 0.05% or more of Be, 0.05% or more of Ba, and 0.05% or more of Ca, with the balance being Al and unavoidable impurities, and cutting the resulting ingot in the shape of a sheet. A rolled sheet (hot-rolled sheet or cold-rolled sheet) obtained by rolling the ingot may also be used as the sheet material.

[0036] An aluminum alloy brazing sheet according to a second embodiment of the invention is characterized in that the core material is clad with the filler metal in a state in which a sheet material and a sacrificial anode material are interposed between the core material and the filler metal so that the core material, the sacrificial anode material, the sheet material, and the filler metal are situated in this order, the sheet material including one element, or two or more elements, among 0.05% or more of Li, 0.05% or more of Be, 0.05% or more of Ba, and 0.05% or more of Ca, with the balance being Al and unavoidable impurities, and the sacrificial anode material including 0.9 to 6% of Zn, with the balance being Al and unavoidable impurities. When brazing is effected using the aluminum alloy brazing sheet according to the second embodiment of the invention, the resulting heat exchanger, machine part, and the like exhibit corrosion resistance due to the sacrificial anode material.

[0037] The Zn content in the sacrificial anode material is 0.9 to 6%. If the Zn content in the sacrificial anode material is less than 0.9%, a sufficient anticorrosive effect may not be obtained. If the Zn content in the sacrificial anode material exceeds 6%, corrosion may be promoted, and the corrosion perforation life may decrease.

[0038] An aluminum alloy brazing sheet according to a third embodiment of the invention includes a core material, a filler metal, and a sacrificial anode material, and is used to braze aluminum in an inert gas atmosphere or in vacuum, the core material including aluminum or an aluminum alloy, the filler metal including 6 to 13 mass % of Si, with the balance being Al and unavoidable impurities, the sacrificial anode material including 0.9 to 6% of Zn, with the balance being Al and unavoidable impurities, one side of the core material being clad with the filler metal, and the other side of the core material being clad with the sacrificial anode material, wherein the core material is clad with the filler metal in a state in which a sheet material is interposed between the core material and the filler metal, the sheet material including one element, or two or more elements, among 0.05% or more of Li, 0.05% or more of Be, 0.05% or more of Ba, and 0.05% or more of Ca, with the balance being Al and unavoidable impurities. The sacrificial anode material provides an anticorrosive effect.

[0039] When the sheet material further includes 0.4 to 4.0% of Mg, it is possible to promote breakage of the oxide film particularly when the heating rate during brazing is high. If the Mg content in the sheet material is less than 0.4%, the effect of breaking the oxide film formed on the surface of the filler metal may be insufficient. If the Mg content in the sheet material exceeds 4.0%, joinability during clad rolling may deteriorate, and it may be difficult to produce a brazing sheet. Moreover, when the brazing sheet is used in combination with a flux, Mg that that has been diffused from the sheet material into the surface of the filler metal may react with the flux, and the function of the flux may deteriorate.

[0040] When the sheet material further includes 2 to 13% of Si, it is possible to promote breakage of the oxide film particularly when the heating rate during brazing is high. If the Si content in the sheet material is less than 2%, the effect of breaking the oxide film formed on the surface of the filler metal may be insufficient. If the Si content in the sheet material exceeds 13%, crack may easily occur during rolling, and it may be difficult to produce a brazing sheet.

[0041] The filler metal may further include either or both of 0.004 to 0.2% of Bi. If the Bi content in the filler metal is less than 0.004%, the effect of improving brazability may be insufficient. If the Bi content in the filler metal exceeds 0.2%, Bi may form a specific oxide, whereby the fluidity or the fillet-forming capability of the molten filler metal may become non-uniform.

[0042] It is preferable that the core material include pure aluminum, or include an aluminum alloy that includes one element, or two or more elements, among 1.8% or less of Mn, 1.2% or less of Si, 1.0% or less of Fe, 1.5% or less of Cu, 0.8% or less of Zn, 0.2% or less of Ti, and 0.5% or less of Zr, with the balance being Al and unavoidable impurities, or include the aluminum alloy that further includes 0.4 to 1.3% of Mg.

[0043] Mn that may be included in the core material (aluminum alloy) is effective for improving the strength of the core material, and adjusting the potential of the core material. If the Mn content in the core material exceeds 1.8%, cracks may easily occur when rolling the material. The lower limit of the Mn content in the core material is preferably 0.3% from the viewpoint of an improvement in the strength of the core material. Si is effective for improving the strength of the core material. If the Si content in the core material exceeds 1.2%, local melting may occur during brazing due to a decrease in melting point, whereby the core material may be deformed, and may exhibit decreased corrosion resistance. The lower limit of the Si content in the core material is preferably 0.3%.

[0044] Fe is effective for improving the strength of the core material. If the Fe content in the core material exceeds 1.0%, the corrosion resistance of the core material may deteriorate, and coarse precipitates may be produced. The lower limit of the Fe content in the core material is preferably 0.2% from the viewpoint of an improvement in the strength of the core material. Cu is effective for improving the strength of the core material, and adjusting the potential of the core material. If the Cu content in the core material exceeds 1.5%, intergranular corrosion may easily occur, and the melting point of the core material may decrease. The lower limit of the Cu content in the core material is preferably 0.2% from the viewpoint of an improvement in the strength of the core material.

[0045] Zn is effective for adjusting the potential of the core material. If the Zn content exceeds 0.8%, the natural electrode potential may decrease, and the corrosion perforation life may decrease. The lower limit of the Zn content in the core material is preferably 0.1%. Ti is effective for causing corrosion to proceed in layers. If the Ti content in the core material exceeds 0.2%, coarse precipitates may be easily produced, and rollability and corrosion resistance may deteriorate. The lower limit of the Ti content in the core material is preferably 0.06%. Zr is effective for increasing the crystal grain size of the core material. If the Zr content in the core material exceeds 0.5%, cracks may easily occur during material production. The lower limit of the Zr content in the core material is preferably 0.2%.

[0046] When the core material (aluminum alloy) includes Mg, it is possible to improve the strength of the brazing sheet, and promote breakage of the oxide film formed on the filler metal. If the Mg content in the core material is less than 0.4%, the strength of the brazing sheet may not be sufficiently improved, and it may be difficult to sufficiently weaken the oxide film formed on the filler metal when brazing is effected in an inert gas atmosphere or in vacuum without using a flux. If the Mg content in the core material exceeds 1.3%, the melting point of the core material may decrease, and local melting may occur during brazing, whereby the core material may be deformed, and eroded due to the molten filler metal. As a result, brazability and corrosion resistance may deteriorate.

[0047] A brazing method according to one embodiment of the invention that utilizes an aluminum alloy brazing sheet includes effecting brazing in an inert gas atmosphere or in vacuum using the above aluminum alloy brazing sheet without applying a flux, to produce a heat exchanger, a machine part, or the like.

[0048] A brazing method according to another embodiment of the invention that utilizes an aluminum alloy brazing sheet includes effecting brazing in an inert gas atmosphere using the above aluminum alloy brazing sheet in a state in which a fluoride-based flux is applied to the entirety or part of a brazing area in an amount of 1 to 20 g/m.sup.2, to produce a heat exchanger, a machine part, or the like.

[0049] When producing a heat exchanger, a machine part, or the like using the brazing method that utilizes a flux, it is preferable to apply the fluoride-based flux to a brazing area that is difficult to braze in an amount of 1 to 20 g/m.sup.2. If the fluoride-based flux is applied in an amount of less than 1 g/m.sup.2, a sufficient effect may not be obtained. If the fluoride-based flux is applied in an amount of more than 20 g/m.sup.2, the amount of flux residue may increase, and the outward appearance of the resulting product may be impaired.

EXAMPLES

[0050] 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 for illustration purposes only, and the invention is not limited to the following examples.

Example 1

[0051] Aluminum alloys (i.e., an aluminum alloy for producing a filler metal, an aluminum alloy for producing a core material, an aluminum alloy for producing a sheet material, and an aluminum alloy for producing a sacrificial anode material) respectively having the composition listed in Table 1 were subjected to continuous casting to obtain ingots. The ingot for producing a core material was ground to have a length of 163 mm, a width of 163 mm, and a thickness of 27 mm. The ingot for producing a filler metal was hot-rolled to have a thickness of 3 mm, and cut to have a length of 163 mm and a width of 163 mm.

[0052] The ingot for producing a sheet material was hot-rolled to have a thickness of 3 mm, cold-rolled to have a thickness of 0.25 to 2 mm, and cut to have a length of 163 mm and a width of 163 mm. The ingot that was merely cut was also used as the sheet material. The ingot for producing a sacrificial anode material was hot-rolled to have a thickness of 3 mm, cold-rolled to have a thickness of 1.5 mm, and cut to have a length of 163 mm and a width of 163 mm.

[0053] The resulting filler metal, core material, sheet material, and sacrificial anode material were subjected to clad rolling according to an ordinary method to obtain a soft clad sheet material having a thickness of 0.4 mm. The soft clad sheet material was used as a specimen.

[0054] The specimen was pressed in the shape of a cup, degreased using acetone (“Unetched” in Table 1), or degreased using acetone, and etched using a weak acid (“Etched” in Table 1), and a cup specimen illustrated in FIGS. 1 and 2 was prepared using the specimen. A fin obtained by forming and degreasing a 3003 alloy sheet material having a thickness of 0.1 mm was provided inside the cup specimen, and brazing was effected without using a flux. Brazing was effected in a nitrogen gas furnace, or in vacuum.

[0055] The nitrogen gas furnace was a two-chamber experimental furnace including a front chamber and a rear chamber. When the temperature of the specimen heated in the front chamber reached 450° C., the specimen was transferred to the rear chamber, and heated. When the temperature of the specimen reached 600° C., the specimen was transferred to the front chamber, and cooled to 570° C. The specimen was then removed from the furnace, and air-cooled. The heating rate during brazing was adjusted by changing the temperature inside the rear chamber. The heating time from 450° C. to 600° C. was set to 12 minutes, 6 minutes, or 3 minutes. The oxygen concentration during brazing was 15 to 20 ppm.

[0056] The vacuum furnace was a batch-type (single-chamber) experimental furnace. The temperature of the furnace was adjusted so that the heating time from 450° C. to 600° C. was set to 12 minutes. The pressure inside the furnace during brazing was 5 to 8×10.sup.−3 Pa. Heating was stopped when the temperature of the specimen reached 600° C. After cooling the specimen to 500° C. inside the furnace, the pressure inside the furnace was returned to atmospheric pressure by injecting nitrogen gas, and the specimen was removed from the furnace, and air-cooled.

[0057] The brazed state of the cup specimen was evaluated as described below. A fillet formed on the outer side of the flare joint was observed with the naked eye. A case where a sound fillet was formed was evaluated as “A”, a case where the fillet did not break, but was unstable to some extent, or the fillet had a uniform shape, but was small, was evaluated as “B”, a case where the fillet broke was evaluated as “C”, and a case where a fillet was not formed, or the size of the fillet was too small to observe, was evaluated as “D”. The brazed state was determined to be acceptable when evaluated as “A” or “B”. The brazed specimen was divided into two pieces, and the fillet formation state on the inner side of the flare joint and the joint of the fin, and evaluated in the same manner as described above.

[0058] The evaluation results are shown in Table 1. As shown in Table 1, the cup specimens prepared using Specimens 1 to 21 according to the invention had an excellent (acceptable) brazed state even when the etching treatment was not performed. Note that the cup specimen prepared using Specimen 14 that was prepared using a sheet material (length: 163 mm, width: 163 mm, thickness: 5 mm) obtained by cutting the ingot, also had an excellent brazed state.

[0059] The cup specimen prepared using Specimen 17 that was heated from 450° C. to 600° C. within 6 minutes, and included the sheet material including Si, had a brazed state better than that of the cup specimen prepared using Specimen 3 that was also heated from 450° C. to 600° C. within 6 minutes, but included the sheet material that did not include Si, since the supply of Li to the surface of the filler metal was promoted due to Si. The cup specimen prepared using Specimen 18 that was heated from 450° C. to 600° C. within 3 minutes, and included the sheet material including both Si and Mg, had a brazed state better than that of the cup specimen prepared using Specimen 19 that was also heated from 450° C. to 600° C. within 3 minutes.

TABLE-US-00001 TABLE 1  of Composition ( ) Thickness ( - ° C.) Atmo- Co Mn Mg Zr ( ) ( ) ( ) sphere 1 6 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — 12 — — — — — — — — — — — 2 — — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — 12 — — — — — — — — — — — 3 — — — — — — — — — — — —  8 Nitro- Outer side: Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: A — — — 13 — — — — — — — — — — — 4 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 13 — — — — — — — — — — — 5 13 — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 13 — — — — — — — — — — — 6 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: A — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 12 — — — — — — — — — — — 7 10 — — — — — — — — — — — — — 12 Outer side: Outer side: A — — — — — — — — — — — — Inner side: A Inner side: A — — — 12 — — — — — — — — — — — 8 12 — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — 12 — — — — — — — — — — — 9 12 — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — 13 — — — — — — — — — — — 10 — — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — gen Inner side: A Inner side: A — — — 13 — — — — — — — — — — — — — — — — — — — — — — — — — — — 13 13 — — — — — — — — — — 11 — — — — — — — — — — — — 22 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 12 — — — — — — — — — — — 12 — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — 13 — — — — — — — — — — 13 — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — — — — — — — — — — — — — — 12 — — — — — — — — — — — 14 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: A — — — — — — — — — — — — gen Inner side: A Inner side: A — — — — — — — — — — — — — — 15 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — — — — — — — — — — — — 16 — — — — — — — — — — — — — 12 Outer side: Outer side: A — — — — — — — — — — — — Inner side: A Inner side: A — — — — — — — — — — — — — — 17 — — — — — — — — — — — — Nitro- Outer side: Outer side: A — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 13 — — — — — — — — — — — 18 — — — — — — — — — — — —  3 Nitro- Outer side: Outer side: — — — — — — — — — — — — gen Inner side: Inner side: A — — — 12 — — — — — — — — — — — 19 — — — — — — — — — — — —  3 Nitro- Outer side: Outer side: A — — — 12 — — — — — — — — gen Inner side: A Inner side: A — — — 12 — — — — — — — — — — — 20 — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 12 — — — — — — — — — — 21 — — — — — — — — — — — — — 12 Nitro- Outer side: Outer side: A — — — — — — — — — — — — — gen Inner side: A Inner side: A — — — 13 13 — — — — — — — — — — indicates data missing or illegible when filed

Comparative Example 1

[0060] Aluminum alloys (i.e., an aluminum alloy for producing a filler metal, an aluminum alloy for producing a core material an aluminum alloy for producing a sheet material, and an aluminum alloy for producing a sacrificial anode material) respectively having the composition listed in Table 2 were subjected to continuous casting to obtain ingots. A soft clad sheet material (specimen) having a thickness of 0.4 mm was produced in the same manner as in Example 1, and a cup specimen was prepared using the specimen. Brazing was effected in a nitrogen gas furnace in the same manner as in Example 1, and the brazed state of the cup specimen was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 2. In Table 2, the values that fall outside the scope of the invention are underlined. Note that a clad material that did not include a sheet material was also produced as a comparative specimen.

TABLE-US-00002 TABLE 2  of Composition ( ) Thickness ( - ° C.) Atmo- ( ) sphere 22 10 — — — — — — — — — — — 12 Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — — gen Inner side: Inner side: A 23 10 — — — — — — — — — — — 12 Nitro- Outer side: C Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: A 24 — — — — — — — — — — — 12 Nitro- Outer side: C Outer side: — — — — — — — — — — — — gen Inner side: Inner side: A — — — — — — — — — — — — — — 25  4 — — — — — — — — — — — — — 13 Nitro- Outer side: Outer side: C — — — — — — — — — — — — — gen Inner side: Inner side: C — — — — — — — — — — — — — — 26 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — 27 — — — — — — — — — — — — — 13 Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — gen Inner side: Inner side: — — — — — — — — — — — — — — 28 — — — — — — — — — — — — Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — gen Inner side: Inner side: A — — — — — — — — — — — — — — 29 — — — — — — — — — — — — — 13 Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — gen Inner side: C Inner side: — — — — — — — — — — — — — — 30 12 — — — — — — — — — — — — — 13 Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — gen Inner side: C Inner side: — — — — — — — — — — — — — — 31 10 — — — — — — — — — — — — 13 Nitro- Outer side: C Outer side: C — — — — — — — — — — — — — gen Inner side: C Inner side: C — — — — — — — — — — — — — — 32 10 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — 33 — — — — — — — — — — — — — Nitro- Outer side: C Outer side: C — — — — — — — — — — — — gen Inner side: Inner side: — — — — — — — — — — — — — — 34 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — 35 — — — — — — — — — — — — — Nitro- Outer side: C Outer side: C — — — — — — — — — — — — gen Inner side: Inner side: — — — — — — — — — — — — — — 36 — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — 37 — — — — — — — — — — — — — Nitro- Outer side: C Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — — — — — — — — — — — 38 — — — — — — — — — — — — — Nitro- Outer side: C Outer side: — — — — — — — — — — — — — gen Inner side: Inner side: — — — — — — — — — — — — — indicates data missing or illegible when filed

[0061] As shown in Table 2, the cup specimens prepared using Specimens 22 to 24 that did not include a sheet material had an inferior outer-side brazed state. The cup specimen prepared using Specimen 25 having a low Si content, had an inferior inner-side brazed state and an inferior outer-side brazed state since the amount of molten filler metal was insufficient. Cracks occurred during rolling when preparing Specimen 26 since the Si content in the filler metal was high. Specimens 27 to 30 had a problem in that the function of breaking the oxide film formed on the surface of the filler metal was insufficient since the content of Li, Be, Ba, or Ca in the sheet material was low, and had inferior brazability. Specimen 31 had a problem in that the Bi content in the filler metal was high, and a Bi oxide was formed, and had inferior brazability.

[0062] Cracks occurred during rolling when preparing Specimen 32 since the Zn content in the sacrificial anode material was high. Specimen 33 had a problem in that the function of breaking the oxide film formed on the surface of the filler metal was insufficient since the content of Mg and Li in the sheet material was low, and had inferior brazability. Specimen 34 had a problem in that separation occurred at the interface between the sheet material and the filler metal during clad rolling since the Mg content in the sheet material was high. Specimen 35 did not show an improvement in brazed state with respect to Specimen 27 since the Si content in the sheet material was low. Cracks occurred during rolling when preparing Specimen 36 since the Si content in the sheet material was high. Specimen 37 had a problem in that the function of breaking the oxide film formed on the surface of the filler metal was insufficient since the Mg content in the core material and the Li content in the sheet material were low, and had inferior brazability. Specimen 38 had a problem in that the melting point of the core material decreased, and the core material was eroded by the molten filler metal since the Mg content in the core material was high, and was deformed during brazing.

Example 2

[0063] Aluminum alloys (i.e., an aluminum alloy for producing a filler metal, an aluminum alloy for producing a core material an aluminum alloy for producing a sheet material, and an aluminum alloy for producing a sacrificial anode material) respectively having the composition listed in Table 3 were subjected to continuous casting to obtain ingots. A soft clad sheet material (specimen) having a thickness of 0.4 mm was produced in the same manner as in Example 1. The specimen was pressed in the shape of a cup, degreased using acetone (“Unetched” in Table 3), or degreased using acetone, and etched using a weak acid (“Etched” in Table 3), and a fin obtained by forming and degreasing a 3003 alloy sheet material having a thickness of 0.1 mm was provided inside the specimen to prepare a cup specimen illustrated in FIG. 1. A flux (fluoride flux basically including KF and AlF.sub.3) that was diluted with an alcohol was applied to the outer side of the flare joint of the cup specimen (indicated by the arrow in FIG. 2), and the cup specimen was brazed in a nitrogen gas furnace under the same conditions as those employed in Example 1. The brazed state of the cup specimen was evaluated in the same manner as in Example 1. The weight of the specimen was measured after drying using an electronic balance, and the difference between the weight of the specimen measured after drying and the weight of the specimen measured before applying the flux was taken as the amount of the flux applied. The evaluation results are shown in Table 3.

TABLE-US-00003 TABLE 3  of Thick- Composition ( ) ness ( - ° C.) Atmo- Not Ap- Not Ap- Mg Cr Zr Li sphere applied plied applied plied 39 — — — — — — — — — — — — Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: A Outer side: A side: A — — — — — — — — — — — — — — Inner Inner Inner Inner side: A side: A side: A side: A 40 — — — — — — — — — — — — Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: A Outer side: A side: A — — — — — — — — — — — — — — Inner Inner Inner Inner side: A side: A side: A side: A 41 — — — — — — — — — — — — Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: Outer side: A side: A — — — — — — — — — — — — — — Inner Inner Inner Inner side: side: side: side: 42 — — — — — — — — — — — — Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: Outer side: A side: A — — — — — — — — — — — — — — Inner Inner Inner Inner side: side: side: side: 43 — — — — — — — — — — — — Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: A Outer side: A side: A — — — — — — — — — — — — — — Inner Inner Inner Inner — — — — — — 25 — — — — — — — side: A side: A side: A side: A indicates data missing or illegible when filed

[0064] As shown Table 3, the cup specimens prepared using Specimens 39 to 43 according to the invention had an excellent (acceptable) brazed state. Specimens 39 to 43 were prepared using the sheet material including Li, Be, Ba, or Ca. The brazability of the outer side of the cup specimen was improved in a stable manner by applying a small amount of flux when the sheet material including Li, Be, Ba, or Ca was interposed between the core material and the filler metal.

Comparative Example 2

[0065] Aluminum alloys (i.e., an aluminum alloy for producing a filler metal, an aluminum alloy for producing a core material, an aluminum alloy for producing a sheet material, and an aluminum alloy for producing a sacrificial anode material) respectively having the composition listed in Table 4 were subjected to continuous casting to obtain ingots. A soft clad sheet material (specimen) having a thickness of 0.4 mm was produced in the same manner as in Example 1, and a cup specimen was prepared in the same manner as in Example 2 using the specimen. A flux (fluoride flux basically including KF and AlF.sub.3) that was diluted with an alcohol was applied to the outer side of the flare joint of the cup specimen (indicated by the arrow in FIG. 2), and the cup specimen was brazed in a nitrogen gas furnace under the same conditions as those employed in Example 1. The brazed state of the cup specimen was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 4.

TABLE-US-00004 TABLE 4  of Thick- Composition ( ) ness ( - ° C.) Atmo- Not Ap- Not Ap- Fe Co Mn Mg Cr Zn Ti Li ( ) ( ) sphere applied plied applied plied 44 — — — — — — — — — — — — 22 Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: A Outer — — — — — — — — — — — — — — Inner side: Inner side: A side: A Inner side: A Inner side: A side: A — — — — — — — — — — — — 22 Nitro- Outer Outer — — — — — — — — — — — — — gen side: Outer side: A Outer — — — — — — — — — — — — — — Inner side: Inner side: side: A Inner side: A Inner side: A side: A — — — — — — — — — — — — — 22 Nitro- Outer Outer — — — — — — — — — — — — gen side: Outer side: A Outer — — — — — — — — — — — — — — Inner side: C Inner side: side: A Inner side: A Inner side: A side: A indicates data missing or illegible when filed

[0066] As shown in Table 4, the cup specimen prepared using Specimen 44 had an acceptable brazed state. However, since the amount of flux applied was small, an improvement in brazability due to application of the flux was not observed with respect to the cup specimen prepared using Specimen 39 (see Table 3) to which an appropriate amount of flux was applied. The cup specimen prepared using Specimen 45 had a problem in that a large amount of flux residue was observed after brazing since the amount of flux applied was large. Specimen 46 had a problem in that, since the Mg content in the sheet material was high, Mg that was diffused from the sheet material into the surface of the filler metal during brazing reacted with the flux, and the function of the flux deteriorated. Moreover, a solid compound was produced, and brazability was impaired.