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내부식용 API 5L X70 다전극 SAW 용접부의 내면 저온인성에 미치는 외면 입열의 영향
안현준,이희근,박용규,은성수,강정윤,An, Hyun-Jun,Lee, Hee-Keun,Park, Young-Gyu,Eun, Seong-Su,Kang, Chung-Yun 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.1
This study aims to investigate the effect of heat input of outside SAW weld on low temperature toughness($-20^{\circ}C$) of inside SAW weld for API 5L X70 with sour gas resistance. As increasing heat input of the outside weld, low temperature toughness of the inside weld was decreased. Especially, in spite of the same heat input, the value of low temperature toughness was fluctuated. On the basis of fracture and microstructure analysis, the low temperature toughness is correlated with the fracture area ratio of shear lips and four kinds of fracture sections. These sections were divided with size and shape of dimple correlated with grain boundary ferrite and cleavage correlated acicular and polygonal ferrite in grain. Therefore, it was seen that these sections were two of final solidification area in the inside weld and the outside weld, no reheated zone and reheated zone in the inside weld. In conclusion, it is thought that the difference of low temperature toughness at the same heat input is due to the fact that each of impact test specimens could have the different microstructure, even though the notch was machined under the error tolerance of 1mm. It is because the final solidification area of the inside weld is very narrow.
순 Ti GTA 용접부의 미세조직과 경도에 미치는 Ar-N<sub>2</sub> 보호가스 중 질소량의 영향
안현준,전애정,홍재근,정보영,이종섭,강정윤,An, Hyun-Jun,Jeon, Ae-Jeong,Hong, Jae-Keun,Jeong, Bo-Young,Lee, Jong-Sub,Kang, Chung-Yun 대한용접접합학회 2012 대한용접·접합학회지 Vol.30 No.2
In this study, effect of nitrogen volume in the shielding gas of Ar-$N_2$ mixing gas on the bead shape, hardness and microstructure of GTA welds of 3mm thick Commercial Pure Ti was investigated. As the nitrogen volume increased, the welding current for full penetration was reduced and hardness in the fusion zone significantly increased compared with that of the base metal, but there is no difference in the hardness of HAZ. Microstructure in the fusion zone with pure Ar gas changed from equiaxed alpha of the base metal to serrated alpha. On the other hand, microstructure using Ar-$N_2$ mixing gas changed to acicular alpha. With the increasing of nitrogen content, the amount of acicular alpha increased and the size of that was fine.
김정수(Kim Jung Su),이재남(Lee Jae Nam),이기승(Lee Gi Seung),안현준(An Hyun Jun) 한국철도학회 2006 한국철도학회 학술발표대회논문집 Vol.- No.-
The command of Subway is intended to adjust and control the train operation, and to play a key role of the total passenger transport and all kinds of affairs related to the safe train operation. Also, this can be considered as affairs to be controlled and operated by Total Traffic Control. For the purpose of developing the ATO system in using the new control technology by substituting the conventional ATS equipment, this technical document includes the technical points resulted from doing the replacement construction in the entire section of Subway Line 2 by Seoul Metro. The replacement work with the new ATO System should neither stop nor affect the system under operation while operating the current ATS System. The different systems should not interfere with each other while performing their individual affairs, and be composed to share the important data for the parallel operation. This technology is needed to proceed in assurance of a high degree of reliability.