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고(<24%)Mn 플럭스코어드와이어를 사용한 다층 용접 시 초층 응고조직의 결정면방위에 따른 미세조직과 경도
한일욱(Il-Wook Han),엄정복(Jung-Bok Eom),윤중길(Joong-Gil Yun),이봉근(Bong-Geun Lee),강정윤(Chung-Yun Kang) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.5
In this study, Microstructure and hardness of 1st layer with crystallographic orientation were investigated about solidification structure in multipass weld using high Mn-Ni flux cored wire. Microstructure of solidification consisted of austenite matrix and a little ε-phase in grain boundaries. Orientation of grains was usually (001), (101), (111). According to crystallographic orientation, morphology of primary dendrite was different. The depletion of Fe and the segregation of Mn, C, Ni, Si, Cu, Cr, O were found along the grain boundaries. The area of segregation was wide with an order of (001), (101), (111) grains. And hardness of grains with crystallographic orientation increased with an order of (001), (101), (111) grains because of the segregation along dendrite boundary.
Ni가 첨가된 고망간 용접봉의 입열량에 따른 인장 특성과 미세조직의 영향
한일욱(Il-Wook Han),윤중길(Jung-Gil Yun),이봉근(Bong-Geun Lee),강정윤(Chung-Yun Kang) 대한용접·접합학회 2018 대한용접·접합학회지 Vol.36 No.1
The cryogenic high manganese steel is designed for tanks that transport liquefied natural gas, which has increased in demand globally. For this purpose, high manganese steel weld wire with ni added for Flux Cored Wire welding was welded under various heat input conditions. Then, a tensile test was measured to evaluate the mechanical properties. As a result, the heat input condition satisfying the required yield strength was 1.5 kJ. The reason for this phenomenon is that a small amount of Cu contained in the base metal and the welding rod is generated in grain boundaries of Cu₂O during solidification, causing liquefaction cracking.
고강도 구조용 철강소재의 대입열 용접 시 열영향부의 조직 미세화 및 기계적 특성 향상에 미치는 TiN 및 B의 효과
박진성,황중기,조재영,한일욱,이만재,김성진,Park, Jin-seong,Hwang, Joong-Ki,Cho, Jae Young,Han, Il Wook,Lee, Man Jae,Kim, Sung Jin 한국재료학회 2019 한국재료학회지 Vol.29 No.2
In the current steel structures of high-rise buildings, high heat input welding techniques are used to improve productivity in the construction industry. Under the high heat input welding, however, the microstructures of the weld metal (WM) and heat-affected zone (HAZ) coarsen, resulting in the deterioration of impact toughness. This study focuses mainly on the effects of fine TiN precipitates dispersed in steel plates and B addition in welding materials on grain refinement of the HAZ microstructure under submerged arc welding (SAW) with a high heat input of 200 kJ/cm. The study reveals that, different from that in conventional steel, the ${\gamma}$ grain coarsening is notably retarded in the coarse grain HAZ (CGHAZ) of a newly developed steel with TiN precipitates below 70 nm in size even under the high heat input welding, and the refinement of HAZ microstructure is confirmed to have improved impact toughness. Furthermore, energy dispersive spectroscopy (EDS) and secondary-ion mass spectrometry (SIMS) analyses demonstrate that B is was identified at the interface of TiN in CGHAZ. It is likely that B atoms in the WM are diffused to CGHAZ and are segregated at the outer part of undissolved TiN, which contributes partly to a further grain refinement, and consequently, improved mechanical properties are achieved.