Method for preventing narrow gap in vacuum brazing from blocking

The invention discloses a method for preventing a narrow gap in vacuum brazing from blocking. The method comprises the following steps: preparing a blocking article according to the size of the narrow gap of an article to be welded; blocking the blocking article into the narrow gap; coating brazing filler to the brazing article of which the narrow gap is blocked with the blocking article, and then transferring into a vacuum brazing furnace for brazing; moving out the blocking article from the narrow gap of the brazing article after the vacuum brazing; blowing the narrow gap with compressed air so as to ensure that the narrow gap is free of residual blocking article, wherein the blocking article is prepared from materials which do not react with the brazing article and the brazing filler. The method is applicable to the brazing process in which the brazing filler and base metal are free of active elements which can react with carbon elements; in addition, a formed brazing joint enables that the narrow gap of the product cannot be blocked, and the brazing joint with high brazing seam quality can be obtained. The method has the advantages of being small in cost, high in adaptability, and simple and convenient to operate.