This paper presents results of experim ental and numerical studies on the effects of undermatched welds on high -strength and heavy-section steels. The studies involved HT-780, HY-100, and HY-130 steels for high-strength steels and A572Gr60 (W14x370) for heavy section steels, whose tensile strength is approximately 750, 700, 900, and 500 MPa, respectively. The objective was to reduce requirements for preheating temperatures, while preventing crack initiation and improving fracture toughness, using undermatched welds for the first several passes of partial- and fullpenetration groove-welded joints involving high-strength and heavy -section steels .
