Elevated temperature strain softening characteristics of 12Cr1 MoV steel friction welding pipe joints

摘要

The strain softening characteristics analysis of 12Cr1MoV steel friction welding pipe joints, which were removed from heating apparatus pipes after over 9 and 15 years of service, was undertaken. It is concluded that the evident softening did not occur in the weld metal and HAZ during service, whereas it did in the base metal 2mm apart from the center of the weld metal. The difference is due to the restriction of the pipe hoop, which is formed on the joint during friction welding. The bainite microstructure in the weld metal and HAZ, which is harder than the pearlite microstructure in the base metal, makes contribution too. This phenomenon is peculiar to the friction welding pipes.