Effects of the Welding Process and Consumables on the Fracture Behavior of 9 Wt.% Nickel Steel

In recent years, stringent environmental regulations for air pollution have led to increased demand for liquefied natural gas (LNG). Therefore, the demand for the design and construction of LNG-fueled vessels has also increased. One of the most important points for the design of LNG-fueled vessels is the structural integrity of the LNG fuel tank, particularly at cryogenic temperatures. Low temperature materials are used in the construction of LNG fuel tanks to ensure structural safety. Among the various low temperature materials, nickel steel is commonly employed for the design of LNG storage tanks. In addition, Shielded Metal Arc Welding (SMAW) and Submerged Arc Welding (SAW) are commonly applied to the construction of LNG storage tanks. On the other hand, the application of Flux Cored Arc Welding (FCAW) for nickel steel as an alternative to SMAW and SAW appears to be necessary, considering the high productivity. Nevertheless, there have been few studies of the fracture behavior of nickel steel with FACW compared to SMAW and SAW processes. This study examined the fracture characteristics of 9% nickel steel and weldments considering application for the LNG storage tanks. The fracture characteristics of FCAW was compared with SMAW at 25 degrees C and - 163 degrees C temperatures. As the result, the mechanical properties with FCAW were higher than those with SMAW at 25 degrees C and - 163 degrees C. In addition, SMAW is slightly better than FCAW in terms of the impact absorbed energy. Moreover, the crack tip opening displacement (CTOD) values of the weld metal and heat affected zone (HAZ) with FCAW were higher than those with SMAW.