PURPOSE: To prevent the distortion, deformation and deterioration of a pipe due to high temp. by filling up a molten paraffin into a metallic pipe, bending the pipe after the paraffin is solidified and melting away the paraffin after working.

CONSTITUTION: A plate 5 whose material is same as the pipe is fixed to the opening at one end of a split pipe 1 by welding or the like and the opening is closed. The expanding slot 3 of the pipe 1 is sealed with an adhesive tape 4. The opening at the other end of the pipe 1 is taken as a pouring port 6. The pipe 1 is vertically placed and the molten paraffin 2 is poured into from the pouring port 6. After the paraffin 2 is solidified, the pouring port is closed by fixing a plate 8 whose material is same as the pipe 1 to the pouring port 6. The pipe 1 is bent. Both end parts 1' of the pipe 1 are cut, the filled paraffin 2 is melted away by dipping it in boiling water 18 and a product is made. The molten paraffin 2 does not mix with the boiling water 18, rises to the surface of the hot water and coheres.