PURPOSE: To prevent the erosion corrosion of edge parts of oil loading pipes connected by a flexible joint with a gap left between the edges by hardening the edge parts within a specified range each from the edge along the axial direction.

CONSTITUTION: Oil loading cast pipes 1 contg. 0.5W1.5% Cr and linearly connected by flexible joint 2 composed of joint tube 4, sealant 5, holding rings 6 and clamping bolt 7 with a gap left between the edges. The edge parts of pipes 1 are quench hardened within 10W150mm range each from the edge along the axial direction. Thus, the corrosion resistance of the pipe edge parts where corrosion due to erosion begins is enhanced.