Low-cycle Fatigue and Fracture Behaviour of 9%Ni Steel Flux Cored Arc Welding joint at Cryogenic Temperature

• Published in: MATEC Web of Conferences Vol. 269; p. 3008
• Main Authors: Mu, Weidong, Li, Yuzhang, Cai, Yan, Wang, Min
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Les Ulis EDP Sciences 2019
• Subjects: Arc welding; Crack initiation; Crack opening displacement; Crack propagation; Crack tips; Cryogenic temperature; Fatigue cracks; Fatigue failure; Fatigue life; Fatigue tests; Flux core wire welding; Fracture mechanics; Fracture toughness; Heat treating; Low cycle fatigue; Metal fatigue; Nickel steels; Propagation modes; Welded joints; Welding fluxes
• ISSN: 2261-236X; 2274-7214; 2261-236X
• DOI: 10.1051/matecconf/201926903008

In the present work, low-cycle fatigue (LCF) test and crack tip opening displacement (CTOD) test were performed for 9% Ni steel flux cored arc welding (FCAW) joint at room temperature (296 K) and cryogenic temperature (80 K). At cryogenic temperature, the strain amplitude had a far greater impact on fatigue life of 9%Ni steel welded joint and it decreased dramatically lead to a significant increase in fatigue life. It was found that most fracture initiation of joints located in fusion area at room temperature, while it occurred in weld seam at low temperature. The fracture toughness of weld seam was higher than that of fusion zone no matter the testing temperature. The effect of precipitated phase was the true reason. The fatigue cracks propagated in transgranular mode at room temperature, ultimately, and intergranular mode at low temperature in both LCF specimens and CTOD specimens.