Method for preparing flexible welding wire of brittle aluminum-silicon-copper brazing filler metal

The invention discloses a method for preparing a flexible welding wire of a brittle aluminum-silicon-copper brazing filler metal. The method is characterized in that a mixed powder is wrapped by a flexible material aluminum-silicon alloy skin, wherein the mixed powder is prepared from, by weight, 10%-100% of brittle material aluminum-silicon copper powder and 0%-90% of aluminum brazing agent powder. The method comprises the steps that the aluminum-silicon copper powder is prepared from the aluminum-silicon-copper brazing filler metal by a vacuum smelting gas atomization method; the aluminum-silicon copper powder and the aluminum brazing agent powder are mixed according to a weight ratio, and are placed in a double-planetary stirrer for full stirring, and the mixed powder is obtained; an aluminum-silicon brazing filler metal is subjected to smelting, extruding, rolling and slitting to obtain an aluminum-silicon brazing filler metal strip; and the aluminum-silicon brazing filler metal strip is put into a weldin