Method of manufacturing a brazing sheet
In a brazing sheet manufacturing method, a cladding slab is prepared by overlaying at least a core-material slab composed of an aluminum material and a filler-material slab composed of an Al—Si series alloy, in which a metal element that oxidizes more readily than Al is included in at least one of the slabs. A clad sheet is prepared by hot rolling this cladding slab, which then has at least a core material layer composed of the core-material slab and a filler material layer composed of the filler-material slab and disposed on at least one side of the core material. Then, a surface of the clad sheet is etched using a liquid etchant that contains an acid. Subsequently, the clad sheet is cold rolled to a desired thickness. In flux-free brazing, such a brazing sheet is capable of curtailing degradation in brazeability caused by fluctuations in dew point and oxygen concentration.
1. A brazing sheet method for brazing an aluminum material in an inert-gas atmosphere without the use of flux, comprising:
preparing a cladding slab by overlaying a plurality of aluminum slabs that includes a core-material slab composed of an aluminum material and a filler-material slab composed of an Al—Si series alloy, in which a metal element that oxidizes more readily than Al is included in at least one of the slabs;
preparing a clad sheet, which comprises a core material composed of the core-material slab and a filler material composed of the filler-material slab and disposed on at least one side of the core material, by hot rolling the cladding slab;
etching a surface of the clad sheet using a liquid etchant that contains an acid; and
subsequently cold rolling the clad sheet to a desired thickness;
wherein:
the aluminum material of the core material comprises 0.81-4.0 mass % Mg; and
the Al—Si alloy of the filler material comprises less than 0.01 mass % Mg.
2. The brazing sheet manufacturing method according to claim 1 , wherein in the etching step, 0.05-2 g/m 2 of the clad sheet is etched.
3. The brazing sheet manufacturing method according to claim 1 , wherein in the etching step, the liquid etchant contains hydrofluoric acid and an inorganic acid other than hydrofluoric acid.
4. The brazing sheet manufacturing method according to claim 1 , wherein after the etching has been performed, the clad sheet is cold rolled to a rolling reduction of 5-80%.
5. The brazing sheet manufacturing method according to claim 1 , further comprising:
between the hot rolling step and the etching step, cold rolling the clad sheet to a rolling reduction of 20% or more.
6. The brazing sheet manufacturing method according to claim 1 , wherein in the cold rolling step, the clad sheet is cold rolled to a rolling reduction of 25-75%.
7. The brazing sheet manufacturing method according to claim 6 , wherein the liquid etchant contains hydrofluoric acid and an inorganic acid other than hydrofluoric acid.
8. The brazing sheet manufacturing method according to claim 7 , further comprising:
between the hot rolling step and the etching step, cold rolling the clad sheet to a rolling reduction of 20% or more.
9. The brazing sheet manufacturing method according to claim 2 , wherein:
between the hot rolling step and the etching step, the clad sheet is cold rolled to a rolling reduction of 20% or more;
in the etching step, 0.05-2 g/m 2 of the clad sheet is etched; and
in the cold rolling step after the etching step, the clad sheet is cold rolled to a rolling reduction of 5-80%.
10. A method for manufacturing a brazing sheet, comprising:
overlaying at least a first layer and a second layer, the first layer being composed of aluminum or an aluminum alloy and the second layer being composed of an Al—Si series alloy, wherein a metal element that oxidizes more readily than Al is contained in at least one of the first and second layers,
hot rolling the overlaid first and second layers to form a clad sheet;
etching a surface of the clad sheet using a liquid etchant that contains an acid; and
subsequently, cold rolling the clad sheet to reduce the thickness of the clad sheet wherein:
the aluminum material of the first layer comprises 0.81-4.0 mass % Mg; and
the Al—Si alloy of the second layer comprises less than 0.01 mass % Mg.
11. The method according to claim 10 , wherein:
the metal element that oxidizes more readily than Al is Mg.
12. The method according to claim 11 , wherein the second layer contains 6.0-13.0 mass % Si.
13. The method according to claim 12 , wherein after the etching has been performed, the clad sheet is cold rolled to a rolling reduction of 5-80%.
14. The method according to claim 13 , wherein in the etching step, the liquid etchant contains hydrofluoric acid and an inorganic acid other than hydrofluoric acid.
15. The method according to claim 14 , further comprising:
between the hot rolling step and the etching step, cold rolling the clad sheet to a rolling reduction of 20% or more.
16. The brazing sheet manufacturing method according to claim 9 , wherein:
after the etching has been performed, the clad sheet is cold rolled to a rolling reduction of 5-80%; and
between the hot rolling step and the etching step, the clad sheet is cold rolled to a rolling reduction of 20% or more.