• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 춘계학술발표대회 개요집
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• pp.23-26
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• 2001

• 대한기계학회논문집A
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• 제34권1호
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• pp.79-83
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• 2010

최근 원자력발전소 배관계의 용접 시 결함 발생의 원인이 되는 용접변형과 용접잔류응력을 감소시키고 용접 효율도 증가시키기 위해 협개선 용접법이 적용되고 있다. 협개선 용접법은 기존 용접법에 비해 상대적으로 입열량이 적고 용접변형과 용접잔류응력도 감소시킬 수 있기 때문에 배관 건전성 관점에서 많은 이점이 있을 수 있다. 그러나 실제 협개선 용접부 결함에 대한 정확한 파괴역학적 분석 등을 위해서는 용접 특성을 고려하여 변형 및 용접잔류응력 특성을 정확하게 예측해야 한다. 따라서 본 논문에서는 협개선 용접부에 대한 상세 2차원 유한요소해석을 수행하여 협개선 용접부의 용접잔류응력 분포를 결정하였으며, 이를 일반적인 용접법에 대한 특성과 비교하였다. 본 논문의 결과는 향후 협개선 용접부의 결함 평가와 용접방법 개선 등을 위해 적용될 수 있다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.32-32
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• 2009

Electric Resistance Welding (ERW) process is the most efficient process to manufacture the linepipe. To develop the high performance ERW linepipe using the high strength and the high alloy steels, the modulation of input power waveform such as sinusoidal waveform is introduced because the conventional ERW technology is not sufficient enough to produce the high quality linepipe due to its strength and high alloy contents (high Ceq). In this article, the material used for the experiment was API X60 with 8.2mm thickness, and ERW simulator at POSCO was used to develop a waveform control system for the power modulation. The frequency of power modulation was varied from 50Hz to 150Hz with the fixed amplitude of ${\pm}2%$ power. The non-modulated power input and the modulated power input cases are conducted to demonstrate the variation of the narrow gap length and the arcing frequency due to power modulation. From results of the non-modulated power input case, the excessive power causes the longer narrow gap length and the low arcing frequency due to the large heat input and the strong electro magnetic force that increase the weld defect. On the contrary, the small narrow gap length and the high arcing frequency reduce the weld defect. After modulating the power input with 50Hz and 100Hz at the fixed power, the arcing frequency increases, but the narrow gap length does not change much. The high arcing frequency prevents the formation of weld defect because the sweeping frequently cleans the oxides on the narrow gap edges. As a result, the manufacturing window can be expanded by the power modulation that provides the stable ERW process for the quality improvement of the linepipe made from the high strength/high alloy steels.

• Journal of Welding and Joining
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• 제29권6호
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• pp.77-81
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• 2011

In most industry, manual GTAW welding is preferred for formation of stable back bead in root weld of butt joint. However, manual GTAW welding has low productivity as compared with GMAW, also it has unstable bead quality which depend on skilled workers. So it is necessary to develop process of root pass welding by using automation GMAW that have stable back bead formation and high productivity. In this paper, the design of U-groove with 3mm root face was applied to extend the tolerance of misalignment in condition of standard root gap 1.5mm. Consequently, for the formation of stable back bead in root pass of butt welding, in case of the narrow root gap(0.5mm) the large arc force was applied by increasing the current and voltage. In case of the large root gap(2.5mm), the small arc force was applied by decreasing the current and voltage. Considering the various root gap, the required deposited metal was controlled by welding speed only.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.231-233
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• 2004

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 추계학술발표대회 개요집
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• pp.138-140
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• 2005

Plasma arc welding(PAW) technology is a proven process that has already been adopted by other industrial fields and recently has been considered to join the tank structure of LNG carrier. The purpose of this study is to introduce PAW process for the root welding of stainless steel pipes instead of TIG welding. There are distinctive features of the PAW compared to TIG welding; higher energy density that can increase welding speed by more than twofold, and longer arc length that can be controlled to trace seam line easily because of allowable gap between workpiece and torch. However, PAW process is also very sensitive to the root gap and misalignment due to the characteristics of long and narrow arc shape. So, we have done various experiments to establish the allowable fit-up condition by changing welding parameters including arc length, with or without filler metal, groove shape, and obtained satisfactory result.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.30-33
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• 1996

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.43-46
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• 2010

As the nuclear power plant has been constructed continuously for several decades in Korea, the welding technology for components manufacturing and installation has been improved largely. Standardization for weld test and qualification was also established systematically according to the concerned code. The welding for the main components requires the high reliability to keep the constant quality level, which means the repeatability of weld quality. Therefore the weld process qualified by thorough test and evaluation is able to be applied for manufacturing. Narrow gap SAW and GTAW process are usually applied for girth seam welding of pressure vessel like Reactor vessel, steam generator, and etc. For the surface cladding with stainless steel and Inconel material, strip welding process is mainly used. Inside cladding of nozzles is additionally applied with Hot wire GTAW and semi-auto welding process. Especially the weld joint having elliptical weld line on curved surface needs a specialized weld system which is automatically rotating with adjusting position of the head torch. The small sized pipe, tube, and internal parts of reactor vessel requests precise weld processes like an automatic GTAW and electron beam welding. Welding of dissimilar materials including Inconel690 material has high possibility of weld defects like a lack of fusion, various types of crack. To avoid these kinds of problem, optimum weld parameters and sequence should be set up through the many tests. As the life extension of nuclear power plant is general trend, weld technologies having higher reliability is required gradually. More development of specialized welding systems, weld part analysis and evaluation, and life prediction for main components should be taken into a consideration extensively.

• 대한기계학회논문집A
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• 제35권6호
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• pp.635-642
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• 2011

일반적인 용접법은 용접 그루브(groove) 각도가 크기 때문에 용접 결함 발생의 원인이 된다. 따라서 원자력 발전소 배관 용접 시, 용접 그루브 각도가 작고 용접부 비드 폭이 좁은 협개선 용접법을 다수 수행하고 있다. 이러한 협개선 용접법은 용접시간 단축, 용접부 변형과 잔류응력의 감소, 용접 결함의 감소 등과 같은 장점을 갖고 있다. 본 논문에서는 협개선 용접부의 실제 용접 공정을 모사함으로써, ER308L 용접재의 변형 거동과 용접잔류응력을 비선형 2차원 유한요소해석을 통하여 예측하였다. 특히 용접방법 및 순서가 다른 두 형상에 대한 결과를 비교하고, 용접부 폭 넓이 변화에 따른 잔류응력 분포를 분석하였다. 본 논문의 결과는 향후 협개선 용접부의 용접 개선과 용접부 결함의 건전성 평가 등을 위해 적용될 수 있다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.101-106
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• 2002

Requirements to fabrication processes for arc welding of highly loaded thick-walled joint and problems of research and development in term s of the tendency for the modern aircraft structure development are outlined. A justified, choice of the development line of the new promising welding processes for solution of these problems is presented. A complex of new welding processes and technologies for making highly reliable joints with different thickness (up to 120 mm and more) and length of weld (up to 0.1 m; 0.1-0.5 m and more than 0.5 m) has bee developed. It is shown that the possibility to control the heat flow distribution over the groove surface of the welded joints provides for improved reliability. The new welding processes are equipment are effectively used in serial production of the Mykoyan md Sukhoi supersonic aircrafts as well as in AN-124 Ruslan and AN-225 Mriya wide body aircrafts.