Microstructure and mechanical properties of high manganese steel welded joints for LNG storage tanks using two distinct filler wires

Abstract

High-manganese austenitic steel has garnered significant attention for use in LNG vessels due to its substantial cost advantages. The service life of LNG storage tanks strongly depends on the performance of welded high manganese steel structural components in cryogenic environments. Some high-entropy alloys exhibit remarkable mechanical properties at cryogenic temperatures. Promoting the in-situ formation of a high-entropy alloy in the weld metal can be beneficial for optimizing the low-temperature performance of the welded joint. In this study, two types of filler metal were employed to complete the welding process on high manganese steel: a CoCrNi filler wire and a nickel-based filler wire. The microstructure, hardness, and tensile properties of these two types of welded joint were compared and analyzed. Although both types of welded joint exhibited similar tensile properties at 298 K, the CoCrNi joint demonstrated superior tensile strength at 77 K, and the fracture elongation of the CoCrNi joint was ∼1.65 times the value for the nickel-based joint. The superior properties of the CoCrNi alloy could potentially be related to a reduction in the size of the precipitates at the weld seam.