• Nuclear Engineering and Technology
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• 제54권8호
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• pp.2755-2770
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• 2022

The need for Dissimilar Welded Joint (DWJ) in the power plant components arises in order to increase the overall efficiency of the plant and to avoid premature failure in the component welds. The Activated-Tungsten Inert Gas (A-TIG) welding process, which is a variant of Tungsten Inert Gas (TIG) welding, is focus of this review work concerning the DWJ of nuclear grade creep-strength enhanced ferritic/martensitic (CSEF/M) steels and austenitic steels. A-TIG DWJs are compared with Multipass-Tungsten Inert Gas (M-TIG) DWJ based on their mechanical and microstructural properties. The limitations of multipass welding have put A-TIG welding in focus as A-TIG provides a weld with increased depth of penetration (DOP) and enhanced mechanical properties. Hence, this review article covers the A-TIG welding principle and working parameters along with detailed analysis of role played by the flux in welding procedure. Further, weld characteristics of martensitic and austenitic steel DWJ developed with the A-TIG welding process and the M-TIG welding process are compared in this study as there are differences in mechanical, microstructural, creep-related, and residual stress obtained in both TIG variants. The mechanics involved in the welding process is deliberated which is revealed by microstructural changes and behavior of base metals and WFZ.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.506-519
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• 2024

To simulate the verification process using materials from a decommissioned reactor, a mock-up of the bottom-mounted instrument nozzle in the Kori 1 reactor, where the nozzle was attached to a plate by J-groove dissimilar metal welding, was fabricated. The mock-up distortion was quantified by measuring the plate surface displacement after welding. The residual stresses formed on the support plate surface and the inner surface of the nozzle were then analyzed using the hole-drilling method, contour method, and neutron diffraction. Welding simulations were performed using a 3D finite element method to validate the measured results. The measured and computed stress distributions on the support plate exhibited reasonable agreement. Conversely, the stresses on the inside of the nozzle were found to have an indisputable difference in the contour method and neutron diffraction measurements, which demonstrated strong tensile and compressive hoop stresses, respectively. The possible origins of such differences were investigated and we have provided some suggestions for a precise evaluation in the simulation. This study is expected to be useful in future research on decommissioned reactors.

• 한국강구조학회 논문집
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• 제13권4호
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• pp.327-335
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• 2001

강관 적층용접부에서 발생하는 잔류응력의 특징과 생성 메커니즘을 밝히기 위해 유한요소법을 이용한 3차원 열탄소성 해석을 수행하였다. 용접에 의해 강관을 접합할 때, 원주방향잔류응력과 두께방향잔류응력은 강관 내 외부에서 모두 접합부에서 인장응력이 발생하고, 길이방향잔류응력은 강관 내무에서 인장응력, 외부에서 압축응력이 발생된다. 또한 강관 적층 용접부의 잔류응력 생성기구를 명확히 하였다. 그 결과, 강관의 용접에 의한 잔류응력은 열응력에 의해 발생 할 뿐만 아니라, 강관의 기하학적 형상변화에 의한 영향도 받는다는 것을 밝혔다. 그리고, 용접조건과 강관의 제원이 달라질 경우에도 잔류응력 생성기구가 변함이 없음을 밝혔다.

• 한국강구조학회 논문집
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• 제26권3호
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• pp.155-167
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• 2014

강-콘크리트 합성보는 오랫동안 건물시공에 사용되어져 왔다. 합성보의 필수요소는 강재단면과 콘크리트 슬래브 사이의 전단접합이며, 주로 기계적 전단연결재가 사용되며 다양한 형상의 장치가 사용되어져 왔다. 본 연구는 앵글 전단연결재를 가진 push-out 실험체의 실험결과를 조사한 것이다. 앵글 전단연결재의 전단성능을 검토하기 위해서 모두 22개의 push-out 실험체를 설계하였으며, 앵글의 높이, 용접길이 및 앵글의 간격 등의 실험변수를 바탕으로 그 영향을 검토하였다. 실험결과를 바탕으로 앵글 전단연결재의 전단강도를 예측할 수 있는 설계식을 제안하였다.

• 한국압력기기공학회 논문집
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• 제6권2호
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• pp.20-27
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• 2010

In order to prevent the corrosion of component contacted primary water designed alloy 600 material in the nuclear power plant. But the primary water stress corrosion cracking(PWSCC) of alloy 600 and weld area occurs continuously due to the residual stress. The leakage accident resulted from PWSCC in the drain nozzle of the steam generator of domestic power plants. Heater sleeves of the pressurizer are welded with alloy 600 weld material and therefore exposed to the primary water environment. PWSCC occurred in heater sleeve material and weld area of many foreign power plants. The current issue of domestic nuclear power plants are consequently concentrated to PWSCC of similar material. In order to improve the detection and the sizing of the PWSCC in the welding sleeve of the pressurizer, the automatic UT system and multi-directions probe sets have been developed. The experimental studies have been performed using the mock-up block containing artificial reflectors(ID connected EDM notch) and semi-artificial cracks made from thermal fatigue. The automatic UT System is applied in the detection and the length sizing of the ID/OD on the tube and the J-groove weld area of the artificial reflectors and results of the detection and the sizing are compared respectively. Also, the developed automatic UT system is successfully accomplished to inspect the heater sleeve and the J-groove weld area on the pressurizer for the detection of PWSCC.

• Journal of Welding and Joining
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• 제30권4호
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• pp.31-37
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• 2012

In recent years, a demand for precision-welding is increasing in wide industrial fields for getting a high quality welded structures. Although laser welding is commonly used for precision-welding, gas tungsten arc (GTA) welding is also attempted as a precision-welding due to the cost benefit. However, welding heat causes an uneven temperature distribution leading to welding deformation. Since it causes geometric errors and degrades product quality, welding distortion recently rises as an important issue in the field of automobile parts. To control welding deformation, it is needed to design in shapes that can maximize stiffness against deformation during welding; control the welding sequence; minimize heat input; and weld allowing reverse deformation; etc. Thus it is necessary to find the one, among such approaches, that can minimize the deformation range by mathematical analysis and understand how effective it would be when it is actually used in industrial fields. This study performs analyses by numerical calculations and experiments for the De-Tent Lever, one of transmission part that requires precision the most among automobile parts, as the subject of experiment. Decrease in welding deformation is required for this part, since there is currently a trouble in guaranteeing precision due to angular deformation by welding between boss and plate. Finally the ways to minimize welding deformation has been suggested in this study through analyses on it.

• 보존과학회지
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• 제35권5호
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• pp.440-452
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• 2019

전통 제철 공정 중 단야공정에서 나타나는 다층구조 무늬의 선명도를 향상시키고자 재현실험을 통해 생산된 사철강(SI)과 탄소의 함량이 다른 3종류의 현대강인 경강(HS), 고탄소강(CS), 니켈탄소강(NiS)을 각각 단접한 소재 SIHS(사철강 + 경강), SICS(사철강 + 고탄소강), SINiS(사철강 + 니켈탄소강)을 대상으로 분석하였다. 사철강과 탄소의 함량이 다른 3종류의 현대강의 접합면에 대한 미세조직 관찰 결과, SINiS의 경우 다른 소재에 비해 단접면의 단접이 잘 이루어졌고 표면무늬 또한 두드러지게 관찰되었다. 결정립 크기는 소재별 큰 차이는 없었으나 경도는 SICS가 가장 높았다. 소재별 접합면에 대한 전자빔 미세분석법 측정 결과, SINiS의 경우 니켈과 탄소가 함유되어 표면무늬의 선명도가 다른 소재에 비해 높은 것으로 관찰된다. 이상의 결과를 통해 전통단접기술의 특징인 다층구조 소재에서 표현되는 표면무늬의 선명도를 높이기 위해서는 니켈이 함유된 탄소강이 가장 적합함을 확인할 수 있었다.