Low-magnesium multilayer aluminum alloy brazing expansion material and application thereof

The invention discloses a low-magnesium multilayer aluminum alloy brazing extension material and application thereof, wherein the low-magnesium multilayer aluminum alloy brazing extension material comprises a core layer, a brazing layer and a covering layer which are sequentially compounded, and the covering layer consists of the following components in percentage by weight: 0-14% of Si, less than or equal to 0.3% of Fe, less than or equal to 0.1% of Mg, 0-0.3% of Bi0, and the balance of aluminum, wherein the brazing layer consists of the following components in percentage by weight: si: 2-15%, Fe is less than or equal to 0.3%, Mg: 0.02 to 0.15%, Bi: 0.05-0.3%, Zn: 0-4%, rare earth elements: 0.05-0.3 percent of aluminum, and the balance of aluminum, wherein the core layer consists of the following components in percentage by weight: one of 1xxx, 3xxx, 5xxx, 6xxx or 7 xxx; or 0.05-0.2% of rare earth elements, and the balance of 3xxx, 5xxx, 6xxx or 7 xxx; the invention can saturate the welding quality of the welding head, and overcomes the defects that the soldering flux is not easy to clean and corrode products.