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JCO 밴딩과 SA용접으로 제조된 API-X70급 강관의 HIC/SSCC 저항성 평가
유회수,김희진,이동언,Ryoo, Hoi-Soo,Kim, Hee Jin,Lee, Dong-Eon 대한용접접합학회 2014 대한용접·접합학회지 Vol.32 No.5
This study aims at manufacturing SA welded API-X70 line-pipe with sour gas resistance. A pipe was manufactured by JCO bending process and SA welding using the API-X70 plate guaranteed HIC resistance. SA welded pipe was expanded in order to reduce the residual stress. The evaluation of a pipe for resistance to HIC and SSCC were performed by the RS D 0004 and RS D 0005 standards. For verification that a pipe has acceptable resistance to HIC, fullscale test was carried out. Results showed no cracking for the HIC and SSCC.
$CO_2$박판 고속용접에서 용접현상 분석과 전류상승기울기의 영향
김영삼,유회수,김희진,Kim, Young-Sam,Ryoo, Hoi-Soo,Kim, Hee-Jin 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.5
In high speed $CO_2$ welding, it has been blown to produce no sound bead with undercut or humping bead. In this study welding phenomena through synchronized high speed camera and output welding voltage and current waveform has been analyzed. For the purpose to improve a welding bead, effect of short circuit current rise slope has been examined. With commercial power source it was produced no sound bead by instantaneous short circuit, long arc period and stubbing at welding speed 2.5mm/min Humping bead or undercut were showed by instantaneous short circuit and long arc period. Also, the weld bead was not formed during the long short circuit period after stubbing start and long arc extinguishment period after wire sticking by failure of arc regeneration, because the droplet was not transferred to weld pool. With increasing short circuit current rise slope the frequency of stubbing was decreased and the normal short circuit rate was increased. A control of short circuit current rise slope was effective factor in high speed welding.
서준석,김희진,유회수,Seo Jun Seok,Kim Hee Jin,Ryoo Hoi-Soo 대한용접접합학회 2005 대한용접·접합학회지 Vol.23 No.3
It is required for the steel materials used in the sour environment to have sufficient resistance to hydrogen induced cracking(HIC). For line pipe steels, HIC resistance could be varied during pipe making process due to the large plastic deformation applied in the thick-wall pipe. In order to figure out such effect, HIC tests were performed not only in the plate condition but in the pipe condition and their results were compared in terms of cracking ratio. Test results demonstrated a detrimental effect of plastic deformation to HIC resulting in a substantial increase in the cracking ratio after pipe forming process. All of the cracks found in the pipe material were located in the outer layer of pipe where the tensile strain was resulted during pipe forming stage. In order to understand the HIC resistance of the pipe but in the plate condition, it was suggested to pre-strain the plate to some extent before the HIC test.