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Sourav Kr. Saha,Hyoungjin An(안형진),Byungrok Moon(문병록),Jaeseok Yoo(유재석),Jong Min Park(박종민),Kwang Hee Yun(윤광희),Namhyun Kang(강남현) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.5
The study is devoted towards the investigation of a hydrogen-induced cold cracks (HICC) in welded joints of structural steels. HICC is a well-known phenomenon in structural metals that limit their uses in various valuable applications such as hydrogen transport, marine application, ship building etc. Normally, hydrogen in the weld metal produces hydrogen embrittlement (HE), therefore suppressing the cold crack and HE should be considered. In the present study, multi-pass butt welds were fabricated with low and high heat input conditions (10 kJ/cm and 35 kJ/cm) using various welding fillers having various strength levels as of American Welding Society standard and two base metals (DH36 and S500). HE effects on various specimens were evaluated using the in-situ slow strain rate test (SSRT) and hydrogen permeation test. The HE sensitivity index (HE index) calculated using the SSRT suggests that HE index increased with the strength of welding fillers in low heat input condition. However, reverse phenomenon occurred in high heat input condition. Hydrogen diffusion coefficient (Deff) and reversible hydrogen trap concentration (Crev) calculated using permeation test reflects that Crev increased with the strength level of welding filler. On the other hand, welding specimen fabricated in high heat input condition showed a lower Crev and higher Deff in comparison to the low heat input specimen and thereby decreasing the HE. Microstructure analysis suggests that in low heat input condition, low transformation bainite phase was dominated and vulnerable for HE with increasing strength level of welding filler. On the other hand, high heat input condition produced larger amount of acicular ferrite with increasing strength level and inhibited HE.