METHOD FOR CASTING DUAL TYPE EXHAUST MANIFOLD

PURPOSE:To lighten a casting by arranging a sprue and runner to a lost foam pattern to form an embedding body, embedding this into non-combustible packing material charged in a flask, pouring molten metal, executing thermal decomposition of the lost foam pattern and replacing this with the molten metal. CONSTITUTION:A first and second branched tubes 4, 8 formed as bending with material lost by heating, are set at front and back sides and branched passages 2, 3 and branched pipe conduits 6, 7 in both branched tubes 4, 8, respectively are connected with flange 11 having the same material. As the same way, the passage and pipe conduit are connected with a second flange 12 to form the lost foam pattern 13. By arranging the sprue 16 and runner to this pattern 13, the embedding body 17 is formed and embedded into the non-combustible packing material 20 charged in the flask 19, and molten metal 22 is poured from the sprue 16. The molten metal reaches the pattern 13 and then, the thermal decomposition is executed to this and the molten metal is entered into the space generated in there and cast. As the shifting between a master mold and core is not developed, allowable space to the shifting of core can be neglected and the casting weight can be lightened by the corresponding weight. Further, as removal work of casting flash is unnecessary, the labor saving is attained.