Effects of the welding processes and consumables on the fatigue and fracture performances for 3.5 wt.% nickel steels

Abstract

Ethylene based on ethane gas in petrochemical products has a great economic advantage. Ethane gas can typically be liquefied by cooling to − 95 °C for more efficient transportation. To ensure the structural integrity of very large ethane gas carriers, ethane gas storage tanks are fabricated using materials that exhibit excellent fatigue and fracture performances at cryogenic temperatures, such as SUS304L, Invar alloys, Al 5083-O, high-manganese steels, and nickel steels. This study compared the fatigue and fracture performances of 3.5-wt.% nickel steels considering the welding processes and consumables. To compare the fatigue and fracture performances of 3.5-wt.% nickel steels, three different welding consumables were used for the weld metals with flux core arc welding and flux core arc welding + submerged arc welding. Fatigue and fracture tests with various nickel alloy steels were conducted according to ASTM E647 and ISO 12135, respectively. The mechanical properties with flux core arc welding + submerged arc welding were higher than those with flux core arc welding. In the case of the fracture toughness, the crack tip opening displacement values with flux core arc welding were approximately 45 and 18% lower than those with flux core arc welding + submerged arc welding at room and low temperatures (173 K), respectively. With a fixed slope of 3.0 and a material constant, C, the associated fatigue crack growth rate of the heat-affected zone with flux core arc welding was higher than that in the weld metal. In addition, the fatigue crack growth threshold values of the weld metal were higher than those of the heat-affected zone. The fatigue and fracture performance of various nickel alloy steels was explained in terms of the microstructure of weld metals.