Evaluation and Comparison of Weldabilities with Various Welding Processes on TMCP Steels

Choi, Chul Young; Ji, Chang Wook; Kim, Hyoung Chan; Nam, Dae-Geun; Kim, Joungdon; Kim, Soon Kook; Park, Yeong-Do

doi:2014.32.1.6

J Weld Join > Volume 32(1); 2014 > Article

Special Issue

Journal of Welding and Joining 2014;32(1):6-14.
DOI: https://doi.org/10.5781/JWJ.2014.32.1.6 Published online February 27, 2014.

Evaluation and Comparison of Weldabilities with Various Welding Processes on TMCP Steels

Chul Young Choi^*, Chang Wook Ji^*, Hyoung Chan Kim^**, Dae-Geun Nam^**, Joungdon Kim^***, Soon Kook Kim^****, Yeong-Do Park^****

Correspondence: Yeong-Do Park,
Email: ypark@deu.ac.kr

Abstract

This paper has an aim to evaluate microstructure and fracture toughness of TMCP steel weldment applied for off-shore wind tower with the focus on the effect of heat input on the weldment with various welding processes; FCAW(13kJ/cm and 30kJ/cm), SAW(62kJ/cm), and EGW(177kJ/cm). Based on experimental results developed from this study, it was found that the impact toughness of top side for TMCP steel weldments with heat input up to 62 kJ/cm satisfied the required minimum value except the EGW(177kJ/cm). The heat input and microstructure are the main factors of impact toughness. The heat input of 13kJ/cm on back side with low heat input increased the amount of grain boundary ferrite which has low impact toughness, and heat input of 177kJ/cm on top side is significant enough to produce the austenite grain growth. The compositions and sizes of inclusions which are the dominant factors for the formation of acicular ferrite were analyzed by OM and EDS. As the heat input increased, the inclusions also grew and a nucleation site decreased. The size of nonmetallic inclusions and the crack width was nearly similar, therefore the inclusions were related with the crack propagation.

Key Words: TMCP, Wind tower, FCAW, SAW, EGW