Producing method of clean brazing filler metal cast ingots

The invention discloses a producing method of clean brazing filler metal cast ingots. Firstly, brazing filler metal alloy is smelted through a conventional method; a tundish is preheated to a temperature lower than a failure temperature of brazing flux, and then molten brazing filler metal alloy is poured into the tundish, wherein a ceramic filter, an activated carbon layer and reaction brazing flux are sequentially arranged in the tundish from top to bottom, and the outer wall of the tundish is wrapped by a heat preservation layer; the molten brazing filler metal alloy firstly passes through the ceramic filter and then passes through the activated carbon layer and the brazing flux for full reaction, so that gas and impurities in the brazing filler metal alloy are removed; the molten brazing filler metal alloy is poured out after the ceramic filter is replaced, after secondary filtration, casting and cooling, 1/3 of the upper portion of a cast ingot is removed, and the remaining 2/3 cast ingot is the obtained clean brazing filler metal cast ingot. The producing method has the advantages that gas removing and impurity removing are carried out at the same time, occupied space of equipment is quite small, operation is simple, gas removing efficiency is high, investment is low and operation cost is low; 1/3 of the upper portion of the cast ingot after pouring is removed, the defects of gas holes and impurities of the cast ingot are further reduced, and later processing of brazing filler metal is facilitated.