PURPOSE: To manufacture a long life deformed muffle excellent in heat resistance by inserting a deformed annular flange plate between the edges of a hot pressed heat resistant deformed steel pipe to be jointed.

CONSTITUTION: A plate material of about 20 mm thick is cut into a deformed annular shape wider sufficiently than the inside/outside diameter of a deformed pipe 1 to formed a flange plate 2 which is then inserted between the edges of deformed pipes 1, 1. The deformed pipes 1, 1 are then beveled for build up welding at the outer circumferential edge thereof and jointed each other by placing a beat 3 thereat thus producing a muffle of required length. With such a flange plate, dimensional fluctuation of deformed pipe inevitable at the time of hot press can be absorbed and reliable joint can be attained easily. A centrifugally cast heat resistant pipe having high carbon content exhibits high temperature strength and high durability while suppressing cast-defect.