Extruded multi-path flat tubes of aluminium alloy for heat exchanger and method of manufacture thereof

摘要

An aluminum alloy-based extruded flat tube having the increased proof strength and pressure-resistant strength is disclosed. An aluminum alloy-based extruded multi-path flat tube that is obtained by extruding an aluminum alloy billet is subjected to the low strain working at the low strain of 2 % to 15 % prior to the brazing process. After the flat tube is brazed, it may have the organization that includes the surface layer containing equal to 5% or more than 5 % of non-recrystallized grains and the inner layer containing equal to 30% or more than 30 % of recrystallized grains. The strain may be expressed as (1 - H/H o ) * 100 %, for example, in which H o refers to the height of the flat tube prior to low strain working process, and H refers to the height of the flat tube after the low strain working process is completed. The proof strength can be increased by the non-recrystallized grains contained in the surface layer la and in the surface layer 2a in the path of fluid passage. The reduction in the strength that might be caused by the filler erosion can be prevented as the filler erosion is restricted by the recrystallized grains contained in the inner layer 1b.