Effect of Welding Position on the Low-Temperature Impact Toughness of Weld Metal in High-Strength Low-Alloy Steel

The effect of welding position on the mechanical properties of high-strength low-alloy steel weld metals was investigated with an emphasis on low-temperature impact toughness. Welding was performed in horizontal (2G) and vertical-up (3G) positions using two filler wires with different alloying element contents. For the lower-alloying-content weld metals, the higher heat input associated with the 3G position promoted the formation of grain boundary ferrite and Widmanst?tten ferrite, while acicular ferrite remained the dominant phase, resulting in a pronounced reduction in impact toughness. In contrast, for the higher-alloying-content weld metals, excessive bainite formation in the 2G position led to a significantly reduced impact toughness, whereas a refined acicular ferrite microstructure developed in the 3G welds, yielding the highest impact toughness.