Influence of welding position and dilution on mechanical properties and strengthening design of flux cored arc weld metal for high manganese steels

In the flux cored arc welding of high-Mn steels, the effects of the welding position and heat input on the dilution rate and mechanical properties were investigated using an austenitic stainless steel filler with a lower strength than that of the base metal. Horizontal (2G) and vertical-up (3G-UP) position welding was conducted under low- and high-heat input conditions. The 3G-UP welding position had a higher dilution rate than the 2G welding position, and the yield strength and tensile strength were relatively high at appropriate heat input rather than excessive heat input in 3G-UP. A fully austenitic microstructure with a dendritic structure was primarily observed, and oxide inclusions were observed in the weld metal. The primary dendrite arm spacing was dependent on the heat input rather than on the chemical composition. From the multiple regression model based on the chemical composition and heat input, the strength of the weld metal was determined mainly by monitoring the welding heat input and C, Cu, Mo, and Cr contents. The soundness of high-Mn steel welds with an under-matched filler was confirmed to fulfill the mechanical property requirements for cryogenic applications regardless of the welding position and heat input, and an empirical model to estimate the strength of high-Mn welds was established as follows: Yield Strength (MPa) = 297.7 + 382 × C + 23.2 × Mo + 2.93 × Cr + 438 × Cu – 2.58 × Heat Input (HI).