S. Liu, Colorado School of Mines, Golden, CO
Colorado School of Mines has built a tradition in consumables research for high strength steels during the past three decades. In the 1970's, Mines researchers investigated submerged arc welding for pipeline applications and systematically characterized the fundamental behavior of welding fluxes. They determined the effects of the individual flux ingredients on weld pool chemistry and weld metal chemical composition. They also established the relationships between flux ingredients, weld metal microstructure and weld joint mechanical properties. The knowledge gained in these studies was later applied to the development of coated electrodes for welding steels of 130-ksi yield strength. These studies established the importance of molten flux-weld pool interaction on alloying elements recovery and the non-uniform nature of weld chemical composition. The bimodal nature of weld metal inclusions were observed and related to weld pool deoxidation and weld solidification. High strength steel welding requires more stringent consumables that can deliver low diffusible hydrogen and high weld metal toughness. Consumables that result in low diffusible hydrogen, increased productivity and enhanced weld properties are in great demand. As strength and toughness levels of the steels continue to increase, new generations of consumables must be developed. Two novel consumables design concepts are being investigated at the Colorado School of Mines for steels with strengths greater than 100-ksi yield strength. The first one is based on a duplex microstructure consisted of lath martensite and ferrite. The second one is based on low carbon, high alloy martensite.
Summary: Colorado School of Mines has built a tradition in consumables research for high strength steels during the past three decades. In the 1970's, Mines researchers investigated submerged arc welding for pipeline applications and systematically characterized the fundamental behavior of welding fluxes. They determined the effects of the individual flux ingredients on weld pool chemistry and weld metal chemical composition. They also established the relationships between flux ingredients, weld metal microstructure and weld joint mechanical properties. The knowledge gained in these studies was later applied to the development of coated electrodes for welding steels of 130-ksi yield strength. These studies established the importance of molten flux-weld pool interaction on alloying elements recovery and the non-uniform nature of weld chemical composition. The bimodal nature of weld metal inclusions were observed and related to weld pool deoxidation and weld solidification. High strength steel welding requires more stringent consumables that can deliver low diffusible hydrogen and high weld metal toughness. Consumables that result in low diffusible hydrogen, increased productivity and enhanced weld properties are in great demand. As strength and toughness levels of the steels continue to increase, new generations of consumables must be developed. Two novel consumables design concepts are being investigated at the Colorado School of Mines for steels with strengths greater than 100-ksi yield strength. The first one is based on a duplex microstructure consisted of lath martensite and ferrite. The second one is based on low carbon, high alloy martensite.
