Effect of Heat Input on the Mechanical Properties of SA508 class 3 Steel Weldments with Submerged Arc Welding

Seo, Yun-seok; Koh, Jin-Hyun; Kim, Nam-Hoon; Oh, Se-Yong; Choo, Kee-Nam

JWJ > Volume 22(5); 2004 > Article

Journal of KWJS 2004 October;22(5) :38-45.
Published online November 12, 2004.

Effect of Heat Input on the Mechanical Properties of SA508 class 3 Steel Weldments with Submerged Arc Welding

Yun-seok Seo, Jin-Hyun Koh, Nam-Hoon Kim, Se-Yong Oh, Kee-Nam Choo

Correspondence: Published online November 12, 2004

ABSTRACT

The present study is to investigate the effect of heat input on the microstructure, tensile properties and toughness of single-pass submerged arc bead-in-groove welds produced on SA508 class 3 steels. The heat input was varied in the range of 1.6, 3.2 and 5.0 kJ/mm. The toughness of weld metals was evaluated by using subsize Charpy V-notch specimens in the temperature range of -190℃ to 20℃. The weld microstructure and fractography were observed by optical and scanning electron microscopies, respectively. With increasing heat inputs, tensile strength and hardness of weld metals were decreased while elongation was increased. The poor notch toughness at 1.6 kJ/mm was attributed to the formation of ferrite with aligned second phase and banitic microstructure with high yield strength while that at 5.0 kJ/mm was due to the presence of grain boundary and polygonal ferrites. The microstructure of the intermediate energy input welds consisted of a high proportion of acicular ferrite with limited polygonal ferrites, which provide improved notch toughness.