METHOD FOR PRODUCING SINGLE PIPE FOR DOUBLE DISCHARGING OF EXHAUST MANIFOLD

摘要

PROBLEM TO BE SOLVED: To ensure formation of a cylindrical adiabatic space between internal and external single pipes by maintaining high concentric accuracy of both internal and external single pipes with reduced radius of curvature of the bent portion as least as possible. SOLUTION: In a method for forming a double exhaust single pipe formed of the internal single pipe 10 and the external single pipe 11 each having a bent portion C and a straight portion S connected thereto, the internal and external single pipes 10, 11 respectively are molded using a small-diameter steel pipe and the large diameter steel pipe. The resultant external single pipe 11 is divided into the bent portion C and the straight portion S, which are respectively fitted to the outer periphery of the bent portions C and straight portion S of the internal single pipe 10 for connecting together through welding.