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오스테나이트계 SS배관의 협개선 TIG 용접부 특성 조사
심덕남(Deog-Nam Shim),정인철(In-Cheol Jung) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision<br/> welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width<br/> reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in<br/> heavy wall pipe welding. Generally Narrow-gap TIG welding is used as orbital welding process, it is important to<br/> select the optimum conditions for the automatic control welding<br/> This paper looks at the application and metallurgical properties on Narrow-gap TIG welding joint of heavy wall<br/> large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness.<br/> The fracture toughness depends slightly on the welding heat input.
염화물 환경에서 스테인리스강 용접부의 공식저항성 향상을 위한 마찰교반공정 적용효과에 관한 연구
하종문,심덕남,김승현 한국압력기기공학회 2023 한국압력기기공학회 논문집 Vol.19 No.2
As temporary storage facilities for spent nuclear fuels in domestic nuclear power plants are expected to be saturated, external intermediate storage facilities would be required in the future. Spent nuclear fuels are stored in metal canisters and then placed in a dry environment within concrete or metal casing for operation. In the United States, the dry storage method for spent nuclear fuels has been operated for an extended period. Based on the corrosion experiences of dry storage canisters in chloride environments, numerous studies have been conducted to reduce corrosion in welds. With the construction of intermediate storage facilities in Korea for spent nuclear fuels expected near coastal areas adjacent to nuclear power plants, there is a need for research on the corrosion occurrence of welds and mitigation methods for canisters in chloride environments. In this paper, we measured and compared the residual stresses in the Heat-Affected Zones (HAZ) after electron beam welding (EBW) and gas tungsten arc welding (GTAW) processes for candidate materials such as 304L, 316L, and duplex stainless steel(DSS). We investigated the possibility of microstructure control through the application of surface modification processes using friction stir processing (FSP). Corrosion tests on each welded specimen revealed a higher corrosion rate in EBW welds compared to GTAW. Furthermore, it was confirmed that corrosion resistance improved due to phase refinement and redistribution of precipitates when FSP was applied.
STS304L 및 STS316L 용접부의 응력 부식 균열 개선을 위한 저온 분사 코팅의 잔류 응력 감소 효과에 대한 연구
박광용,심덕남,하종문,이상동,조성우 한국압력기기공학회 2023 한국압력기기공학회 논문집 Vol.19 No.2
A Chloride-induced stress corrosion cracking (CISCC) of austenite stainless steel in dry cask storage system (DCSS) can occur with extending service time than originally designed. Cold spray coating (CSC) not only form a very dense microstructure that can protect from corrosive environments, but also can generate compressive stress on the surface. This characteristic of CSC process is very helpful to increase the resistance for CISCC. CSC with several powders, such as 304L, 316L and Ni can be optimized to form very dense coating layer. In addition, the impact energy generated as the CSC powder collides with the surface of base metal at a speed of Mach 2 or more can remove the residual tensile stress of welding area and serve the compress stress. CSC layers include no oxidation and no contamination with under 0.2% porosity, which is enough to protect from the penetration of corrosive chloride. Therefore, the CSC coating layer can be accompanied by a function that can be disconnected from the corrosive environment and an effect of improving the residual stress that causes CISCC, so the canister’s CISCC resistance can be increased.
가상 고정물을 이용한 축 대칭 용접물의 용접 변형 해석 모델링 기법
이호진,이봉상,정인철,심덕남,Lee, Ho-Jin,Lee, Bong-Sang,Jung, In-Chul,Shim, Deog-Nam 대한용접접합학회 2010 대한용접·접합학회지 Vol.28 No.2
Although two dimensional axi-symmetric modeling is useful for calculating the residual stresses of a cylindrical weldment such as a core barrel, this conventional axi-symmetric modeling can not express the behavior of shrinkage well in the locally heated weld zone. New technique of two dimensional axi-symmetric modeling using a virtual fixture is suggested to simulate the behavior of dimensional changes in the weld zone during the heating period of the welding. The virtual fixture in the model has a role to restrain the expansion of the high temperature heated region, which simulates equivalent intrinsic restraint effect of the weldment. In the restraint condition of the virtual fixture above the critical yield strength, the calculated shrinkages by using the suggested axi-symmetric model agreed well with those measured in a welded mock-up. The calculated residual stresses by using the suggested axi-symmetric model also agreed well with those calculated by using conventional axi-symmetric model which has beenused for calculating residual stresses in the weldment.
HSC발전소 터빈용 초내열합금 Alloy 617 및 263 용접부의 미세조직에 미치는 후열처리의 영향
김정길(Jeong Kil Kim),심덕남(Deog Nam Shim),박혜지(Hae Ji Park) 대한용접·접합학회 2016 대한용접·접합학회지 Vol.34 No.3
Recently nickel based superalloys are extensively being regarded as the materials for the steam turbine parts for hyper super critical (HSC) power plants working at the temperature over 700℃, since the materials have excellent strength and corrosion resistance in high temperature. In this paper, alloy 617 of solution strengthened material and alloy 263 of γ-precipitation strengthened material were prepared as the testing materials for HSC plants each other. Post weld heat treatment (PWHT) was conducted with the gas tungsten arc (GTA) welded specimens. The microstructure of the base metals and weld metals were investigated with Electron Probe Micro-Analysis (EPMA) and Scanning Transmission Electron Microscope (STEM). The experimental results revealed that Ti-Mo carbides were formed in both of the base metals and segregation of Co and Mo in both of the weld metals before PWHT and PWHT leaded to precipitation of various carbides such as Mo carbides in the specimens. Furthermore, fine γparticles, that were not precipitated in the specimens before PWHT, were observed in base metal as well as in the weld metal of alloy 263 after PWHT.
이상철(S. C. Lee),심덕남(D. N. Shim),공창식(C. S. Kong) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.11
Component reliability is most important in nuclear power plants and other large industrial plants. For example, steam generator failures are very costly and dangerous, in terms of lost production as shutdown and drain radioactive. In the fabrication of steam generator, the tubes are attached to the tubesheet by means of an expansion process, including mechanical rolling, explosive expansion and hydraulic expansion. Tube expansion by its nature creates a high level of residual stresses in the tube wall. Residual stress, combined with the interference, create a stress field which increases the susceptibility of the tube to stress-corrosion cracking(SCC) with its costly consequences. This paper presents an experimental technique for the detailed determination of the state of residual stress, evaluation of the residual stresses in the three expansion methods.
확산접합기술을 이용한 H2 Station용 PCHE형 Compact 열교환기 개발
김정길(Jeong Kil Kim),심덕남(Deog Nam Shim),선칠령(Chil Yeong Seon),양기훈(Ki Hoon Yang),박해지(Hae Ji Park),김동진(Dong Jin Kim) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.5
Diffusion bonding was performed on STS316L plate with micro channels to understand the relationship between bonding conditions and mechanical properties of the joints. Various defects such as spot and line defects developed along the joints bonded at various bonding conditions. As the bonding temperature increased, these defects had a tendency to decrease. With experimental results, it was revealed that bonding temperature was the most critical for formation of defects along the joints. Additionally, the sound joint showed coalescence of grains along the joint by migration of the grain boundaries. Tensile test result showed that the sound joint had better mechanical properties than STS316L base metal, and that crack initiated at spot and line defects followed by fracture. Based on experimental results, PCHE was manufactured and it passed hydraulic test under 1200 bar.