Aluminum alloy brazing sheet for a heat exchanger, and process for producing the same

1. An aluminum alloy brazing sheet for a heat exchanger, comprising a core material, a first filler material cladded on one surface of the core material and a second filler material cladded on the other surface of the core material, wherein:

the core material consists of an Al alloy including 0.05-0.6% by mass of Si, 0.05-0.7% by mass of Fe and 0.6-2.0% by mass of Mn, the balance being Al and inevitable impurities, contents of Si, Fe and Mn satisfying a formula: Si+Fe≤Mn; and

each of the first and second filler materials consists of an Al—Si based alloy including 4.5-13.0% by mass of Si and 0.05-0.8% by mass of Fe, the balance being Al and inevitable impurities, and wherein

the brazing sheet is given a temper designation of HXY, X being 1 or 2 and Y being a natural number from 2 to 6, and has an electric resistivity at room temperature of 31-50 nΩm in a portion formed of the core material;

a dispersion ratio of second phase particles having a circle equivalent diameter of not more than 0.5 μm is 5-50%·μm −1 in the portion formed of the core material, the dispersion ratio of the second phase particles being defined as f/r, wherein f (%) represents an area ratio of the second phase particles while r (μm) represents an average circle equivalent diameter of the second phase particles;

the brazing sheet has an n-value of a work hardening exponent of not less than 0.010, where a nominal strain is within a range of 1%-2%; and

the brazing sheet has a push-in depth of not less than 10 mm when a penetration crack is generated in a punch stretch forming test using a round-head punch having a diameter of 50 mm.

2. An aluminum alloy brazing sheet for a heat exchanger, comprising a core material, a first filler material cladded on one surface of the core material, an intermediate layer material cladded on the other surface of the core material, and a second filler material cladded on a surface of the intermediate layer material opposite to the core material, wherein:

the core material consists of an Al alloy including 0.05-0.6% by mass of Si, 0.05-0.7% by mass of Fe and 0.6-2.0% by mass of Mn, the balance being Al and inevitable impurities, contents of Si, Fe and Mn satisfying a formula: Si+Fe≤Mn;

each of the first and second filler materials consists of an Al—Si based alloy including 4.5-13.0% by mass of Si and 0.05-0.8% by mass of Fe, the balance being Al and inevitable impurities; and

the intermediate layer material consists of an Al alloy including 0.05-0.6% by mass of Si, 0.05-0.7% by mass of Fe and 0.05-5.0% by mass of Zn, the balance being Al and inevitable impurities, and wherein

the brazing sheet is given a temper designation of HXY, X being 1 or 2 and Y being a natural number from 2 to 6, and has an electric resistivity at room temperature of 31-50nΩm in a portion formed of the core material;

a dispersion ratio of second phase particles having a circle equivalent diameter of not more than 0.5 μm is 5-50%·μm −1 in the portion formed of the core material, the dispersion ratio of the second phase particles being defined as f/r, wherein f (%) represents an area ratio of the second phase particles while r (μm) represents an average circle equivalent diameter of the second phase particles; and

the brazing sheet has an n-value of a work hardening exponent of not less than 0.010, where a nominal strain is within a range of 1%-2%; and

the brazing sheet has a push-in depth of not less than 10 mm when a penetration crack is generated in a punch stretch forming test using a round-head punch having a diameter of 50 mm.

3. The aluminum alloy brazing sheet for a heat exchanger according to claim 1 , wherein the Al alloy constituting the core material further includes at least one of 0.05-1.0% by mass of Cu and 0.05-3.0% by mass of Zn.

4. The aluminum alloy brazing sheet for a heat exchanger according to claim 1 , wherein the Al alloy constituting the core material further includes at least one of 0.05-0.3% by mass of Ti, 0.05-0.3% by mass of Zr and 0.05-0.3% by mass of Cr.

5. The aluminum alloy brazing sheet for a heat exchanger according to claim 1 , wherein the Al—Si based alloy constituting the first or second filler material further includes at least one of 0.05-1.5% by mass of Cu and 0.05-5.0% by mass of Zn.

6. The aluminum alloy brazing sheet for a heat exchanger according to claim 1 , wherein the Al—Si based alloy constituting the first or second filler material further includes at least one of 0.003-0.05% by mass of Na and 0.03-0.05% by mass of Sr.

7. The aluminum alloy brazing sheet for a heat exchanger according to claim 2 , wherein the Al alloy constituting the intermediate layer material further includes 0.05-2.0% by mass of Mn.

8. A process for producing the aluminum alloy brazing sheet for a heat exchanger according to claim 1 , comprising a step of performing a hot clad-rolling process wherein the filler materials, or the filler materials and the intermediate layer material, each of which are rolled to have a predetermined thickness, are stacked on opposite surfaces of the core material to form a laminar material and the laminar material is subjected to hot rolling, and wherein

a maximum rate of strain of a sheet of the laminar material with reduction of its thickness in each pass during a hot rolling operation in the hot clad-rolling process is 0.5-10s −1 ; and

a maximum temperature of the laminar material during the hot rolling operation is held within a range of 400-510° C.

9. A structural material for a heat exchanger, comprising the aluminum alloy brazing sheet according to claim 1 .

10. A fin for a heat exchanger, comprising the aluminum alloy brazing sheet according to claim 1 .

11. The aluminum alloy brazing sheet for a heat exchanger according to claim 2 , wherein the Al alloy constituting the core material further includes at least one of 0.05-1.0% by mass of Cu and 0.05-3.0% by mass of Zn.

12. The aluminum alloy brazing sheet for a heat exchanger according to claim 2 , wherein the Al alloy constituting the core material further includes at least one of 0.05-0.3% by mass of Ti, 0.05-0.3% by mass of Zr and 0.05-0.3% by mass of Cr.

13. The aluminum alloy brazing sheet for a heat exchanger according to claim 2 , wherein the Al—Si based alloy constituting the first or second filler material further includes at least one of 0.05-1.5% by mass of Cu and 0.05-5.0% by mass of Zn.

14. The aluminum alloy brazing sheet for a heat exchanger according to claim 2 , wherein the Al—Si based alloy constituting the first or second filler material further includes at least one of 0.003-0.05% by mass of Na and 0.03-0.05% by mass of Sr.

15. A process for producing the aluminum alloy brazing sheet for a heat exchanger according to claim 2 , comprising a step of performing a hot clad-rolling process wherein the filler materials, or the filler materials and the intermediate layer material, each of which are rolled to have a predetermined thickness, are stacked on opposite surfaces of the core material to form a laminar material and the laminar material is subjected to hot rolling, and wherein

a maximum rate of strain of a sheet of the laminar material with reduction of its thickness in each pass during a hot rolling operation in the hot clad-rolling process is 0.5-10s −1 ; and

a maximum temperature of the laminar material during the hot rolling operation is held within a range of 400-510° C.

16. A structural material for a heat exchanger, comprising the aluminum alloy brazing sheet according to claim 2 .

17. A fin for a heat exchanger, comprising the aluminum alloy brazing sheet according to claim 2 .