Aluminum alloy heat exchanger and method of producing the same

An aluminum alloy heat exchanger having a tube,

• wherein the tube is composed of a thin aluminum alloy clad material, in which one face of an aluminum alloy core material having an Si content of 0.05 to 1.0% by mass is clad with an Al—Si-series filler material containing 5 to 20% by mass of Si, and in which the other face of the core material is clad with a sacrificial material containing at least one selected from the group consisting of 2 to 10% by mass of Zn and 1 to 5% by mass of Mg, and
• wherein an element diffusion profile of the aluminum alloy clad material after heating for brazing as determined by EPMA from a filler material side satisfies the following expression (1) when the sacrificial material contains Zn, and the following expression (2) when the sacrificial material contains Mg:
• L-LSi-LZn≧40(μm) (1)
• wherein L represents a thickness (μm) of a wall of the tube;
• LSi represents a position (μm) from a filler material surface of a cross point between an elongated line connecting a point corresponding to an Si content of 1.5% by mass and a point corresponding to an Si content of 1.0% by mass, and a line indicating the Si content of the core material, in the diffusion profile by EPMA from the filler material side;
• and
• LZn represents a diffusion region (μm) from a sacrificial material surface, in which an amount of Zn diffused from the sacrificial material is 0.5% by mass or more;
• L-LSi-LMg≧5(μm) (2)
• wherein L and LSi have the same meanings as those in the expression (1);
• and
• LMg represents a diffusion region (μm) from a sacrificial material surface, in which an amount of Mg diffused from the sacrificial material is 0.05% by mass or more,
• wherein a thickness of the aluminum alloy clad material after heating for brazing is 0.23 mm or less,
• wherein an average crystal grain diameter of recrystallized crystals of the core material of the aluminum alloy clad material after heating for brazing is 180 μm or more;
• and
• wherein the aluminum alloy heat exchanger has a clad ratio of the filler material of 7% or more and less than 13%, and a clad ratio of the sacrificial material of 4% or more and less than 16.5%;
• or the aluminum alloy heat exchanger has a clad ratio of the filler material of 7% or more and less than 20%, and a clad ratio of the sacrificial material of 4% or more and less than 30%.