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해석 해의 온도곡선을 이용한 템퍼비이드 용접공정 평가기술
이호진,이봉상,박광수,변진귀,정인철,Lee, Ho-Jin,Lee, Bong-Sang,Park, Kwang-Soo,Byeon, Jin-Gwi,Jung, In-Chul 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.5
Brittle microstructure created in a heat affected zone (HAZ) during the welding of low alloy steel can be eliminated by post-weld heat treatment (PWHT). If the PWHT is not possible during a repair welding, the controlled bead depositions of multi-pass welding should be applied to obtain tempering effect on the HAZ without PWHT. In order to anticipate and control the tempering effect during the temper bead welding, the definition of temperature curve obtained from the analytical solution was suggested in this research. Because the analytical solution for heat flow is expressed as a mathematical equation of weld parameters, it may be effective in anticipating the effect of each weld parameter on the tempering in HAZ during the successive bead depositions. The reheating effect by the successive bead layer on the brittle coarse grained HAZ formed by earlier bead deposition was estimated by comparing the overlapped distance between the temperature curves in the HAZ. Three layered weld specimens of SA508 base metal with A52 filler were prepared by controlling heat input ratio between layers. The tempering effect anticipated by using the overlapped distance between the temperature curves was verified by measuring the micro-hardness distribution in the HAZ of prepared specimens. The temperature curve obtained from analytical solution was expected as a good tool to find optimal temper bead welding conditions.
이종재료 Butt 용접에 대한 Overlay 용접의 잔류응력해석
김강수(Kang Soo Kim),이호진(Ho Jin Lee),이봉상(Bong Sang Lee),정인철(In Chul Jung),변진귀(Jin Gwi Byeon),박광수(Kwang Soo Park) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.11
In recent years, the dissimilar metal, Alloy 82/182 welds used to connect stainless steel piping and low alloy steel or carbon steel components in nuclear reactor piping system have experienced cracking due to primary water stress corrosion(PWSCC). It is well known that one reason of the cracking is the residual stress by the weld. But, it is difficult to estimate exactly weld residual stress due to many parameters of welding. In this paper, the analysis of 3 FEM models made by ABAQUS Code is performed to estimate exactly the weld residual stress on the dissimilar metal weld. 3 FEM models are Butt model, Repair model and Overlay model and are the plane?strain 2D model. The thermal analysis and the stress analysis are performed on each model and the residual stresses on each model were calculated and compared respectively. Also, the specimen of Butt model was made and the residual stresses were measured by X-Ray method and Hole Drilling Technique. These results were compared with the FEM result of Butt model.
펄스형 Nd:YAG 레이저빔을 이용한 인코넬 판재의 용접 특성
변진귀, 박광수, 한원진, 심상한 한국레이저가공학회 2000 한국레이저가공학회지 Vol.3 No.1
The nuclear steam generators are subjected to corrosion environmental condition during operation that can result in stress corrosion in the tube wall. If any tube wall degradation is recognized, the tube must be repaired by plugging or sleeving. For the sleeving repair, Nd:YAG laser welded sleeving technology is one of the most promising when considering radioactive working conditions in the nuclear power plant. In this paper, the laser welding characteristics of steam generator tube and sleeve materials are investigated. The effects of average laser power, laser energy, welding speed, pulse duration and frequency are evaluated. Based on these results, Nd:YAG laser welded sleeving repair was applied to the degraded steam generator tubes in real environment.