Prediction of static failure in metal inert gas welded nuclear grade pipe 347 SS: Experimentation and finite-element analysis approach

Defect repair, one of primary concerns in the maintenance system for pipelines and other high strength components, is crucial in improving the reliability and economic benefits. Even though modern industries use several welding techniques to join metals, metal inert gas (MIG) welding is frequently preferred to weld stainless steel components by producing strong joints at high speed. In this study, MIG welding was used to butt weld 347 SS pipes. Research related to material failure is critical to engineers in order to find suitable application. Tensile test provides the static behavior of material. Therefore, predicting the strength and failure of material helps in satisfying industrial needs. Finite-element analysis (FEA) is an efficient technique to predict physical phenomenon virtually, therefore reducing the need for real-time prototypes. Johnson-Cook (J-C) material failure model is utilized to define failure in FEA model. Error percentage obtained while comparing FEA and experimental results of weld metal is 1.03%. Presence of niobium carbide is evident through the line map of energy-dispersive X-ray spectroscopy spectrum which prevents knife line attack through retarding chromium carbide precipitation at high temperature cycles. Welded samples with tensile strength of 583 ± 3 MPa exhibit better mechanical strength than base metal with tensile strength of 575 ± 2.5 MPa. This change in mechanical properties is caused by microstructural variation led by occurrence of constitutional supercooling while melt-pool solidifies. Failure mechanism of ductile fracture is understood from fractography (Tensile sample). Hence, this study provides a complete knowledge on failure mechanism of MIG-welded nuclear grade steel pipe under static loading. The failure mechanisms are explained in terms of FEA (J-C model) and fractography.