• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.10 no.1
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• pp.15-19
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• 2014

A Failure or degradation of reactor upper head penetration is a recurring problem due to long term operation at nuclear power plants. And a flaw in the reactor upper head penetration has caused unplanned plant shutdown for repair as well as high economic impact on the plants. Consequently, a detection of flaws is of the utmost importance. Prior to the replacement of reactor upper head penetration, some utilities have repaired the flaws of reactor upper head penetration generated by overlay weld. Until now, only the base metal in reactor upper head penetration has been inspected according to 10 CFR 50.55a and ASME code case N-729-1. Accordingly, it is difficult to detect manufacturing defects and repair defects in overlay weld. This paper presents a case study on the application of Time of Flight Diffraction technique for reactor head penetration mockup with artificial flaws in overlay weld. This study offers a way to understand the flaws detected in reactor upper head penetration overlay weld.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.11
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• pp.42-50
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• 2016

Overlay welding affects the chemical components and weld hardness by dilution of the lamination layer thickness, which determines the surface properties. This study experimentally investigates different numbers of layers for overlay welding monel materials, which are anti-corrosion materials. The Fe content, weldability of the base metal and monel materials, hardness, and surface flatness were examined. Each evaluation was carried out after overlay welding with three layers on the base material and pipe base material of the plate. The Fe content was evaluated by analyzing the constituents of each layer. The Fe content was satisfactory in the three layers. The weldability of the laminate specimens was evaluated by a bending test. The hardness and bead flatness of the laminate specimens were evaluated by micro Vickers and 3D measurements. The hardness was highest in the heat-affected zone with one layer, and it decreased with increasing lamination. In the case of bead flatness, there is a sharp difference in the deviation with increasing numbers of laminations, which should be considered carefully.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.211-213
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• 2000

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.499-500
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• 2011

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.495-496
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• 2013

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2000.04a
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• pp.16-16
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• 2000

분무주조법으로 제조된 Al-25Si-(Fe,V) 합금빌렛의 미세조직을 광학현미경, 주사전자현미경, 투과전자현미경으로 분석하였으며, 빌렛내에서 관찰되는 2차상의 형성거동을 정확히 분석하기 위해 over-sprayed 분말의 미세조직을 분무주조 빌렛과 함께 관찰하였다. 먼저 분무주조 빌렛을 표면으로부터 중심부까지 관찰한 결과, 분무주조 빌렛의 미세조직은 표면부 10mm 가량을 제외하고는 매우 균일한 미세조직을 보여주었다. 이에 본 연구에서는 분무주조 빌렛의 표면부와 중심부, 그리고 over-sprayed 분말조직으로 구분하여 각각에서 관찰되는 2차상을 관찰하였으며, 이를 바탕으로 분무주조 빌렛내에 형성된 2차상의 형성기구를 규명하고자 하였다. Over-sprayed 분말의 미세조직은 기지조직내에 균일하게 분포된 침상의 $\delta$-AlFeSi 상과 각형의 Si 입자로 구성되어 있었다. 반면, 분무주조 빌렛의 경우, 그 중심부에서는 기자조직내에 균일하게 분포된 막대형의 $\beta$-AlFeSi과 부정형의 조대한 Si입자가 관찰되었으며, 표면부에서는 부정형의 Si 입자와 함께 막대형의 $\beta$-AlFeSi/$\delta$-AlFeSi 복합상이 관찰되었다. 특히, 빌렛 표면부의 $\beta$-AlFeSi 상과 $\delta$-AlFeSi 상간에는 일정한 방위관계가 존재하였으며, 이러한 결과는 분무주조 빌렛내에 분포된 $\beta$-AlFeSi상들이 분무액적내에 형성된 준안정 $\delta$-AlFeSi 상으로부터 상분해되어 형성되었음을 제시한다. 이상의 분무주조 조직과 over-sprayed 분말의 미세조직으로부터 분무주조 빌렛의 최종 주조조직은 반응고상태의 분무액적 조직에 의해 지배됨을 알 수 있다.r plate)의 단면 미세조직 사진으로써 모재부와 오버레이충을 함께 보여주고 있다. 모재와 오버레이 충간의 경계면은 모재 일부가 용융된 후 웅고하면서 형성됨으로 인해서 도금이나 용사층과는 달리 매우 견고하게 결합되어 있다. 따라서 계면부의 탈락이라는 문 제점은 거의 없어 심한 응력을 받는 기계구조물 및 부품에도 본 기술은 널리 적용되고 있다. 그리고 사진 1에서 알 수 있는 바와 같이 모재와는 전혀 상이한 재료를 자유로이 선택하여 표면 유효층 일부만 오버레이시키며I 주조 및 단조가 불가능한 재료까지도 표면부에 오버레이 시킴으로 서 부품 및 설비의 제조에 있어 재료비의 절감과 제품의 수명이 획기적으로 개선될 수 있다. 그리고 최근에는 도금 빛 용사 둥과 같은 표면처리를 할 경우임의 소재 표면에 도금 및 용 사에 용이한 재료를 오버레이용접시킨 후 표면처리를 함으로써 보다 고품질의 표면층을 얻기위한 시도가 이루어지고 있다. 따라서 국내, 외의 오버레이 용접기술의 적용현황 및 대표적인 적용사례, 오버레이 용접기술 및 용접재료의 개발현황 둥을 중심으로 살펴봄으로서 아직 국내에서는 널리 알려지지 않은 본 기 술의 활용을 넓이고자 한다. within minimum time from beginning of the shutdown.및 12.36%, $101{\sim}200$일의 경우 12.78% 및 12.44%, 201일 이상의 경우 13.17% 및 11.30%로 201일 이상의 유기의 경우에만 대조구와 삭제 구간에 유의적인(p<0.05) 차이를 나타내었다.는 담수(淡水)에서 10%o의 해수(海水)로 이주된지 14일(日) 이후에 신장(腎臟)에서 수축된 것으로 나타났다. 30%o의 해수(海水)에 적응(適應)된 틸라피아의 평균 신사구체(腎絲球體)의 면적은 담수(淡水)에 적응된 개체의 면적보다 유의성있게 나타났다. 해수(海水)에 적응(適應)된 틸라피아의 신단위(腎單位)의 사

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.21-30
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• 2017

Of the marine engine components, the piston crown and exhaust valve are repaired most frequently. These works are conducted through conventional welding processes such as GTAW or SAW, domestically in marine engine repair factories. New high-efficiency welding or overlay processes such as tandem SAW, tandem MAG, hybrid TIG-MIG welding, pulsed-GMAW, CMT welding, and super TIG welding have been developed recently. Moreover, the plasma transfered arc (PTA) process is an efficient spray method for overlaying on the exhaust valve. In this review paper, the new high-efficiency repair welding methods are introduced for marine engine components. The problems due to repair welding for marine engine components are also presented.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.9 no.1
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• pp.70-76
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• 2013

Several finite element models for the leak-before-break (LBB) assessment of overlay dissimilar metal weldment were constructed and analyzed to develop a simple finite element modeling method. The J-integral, crack opening displacement (COD) and J-integral distribution along the crack front in thickness direction due to the applied moment were obtained from the analysis results of the constructed finite element models, and studied compared to the previous literatures. It is concluded that the modeling with base material only is simple and produces a slightly conservative results compared to the complex modeling composed with weld metal and base metal in the calculation of J-integrals and COD values which are used for the calculation of fracture toughness and postulated leakage crack length respectively.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.39-52
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• 1990

The research is to insure the soundness of the stainless steel overlaid weld metal(21/4Cr-IMo steel + SUS 309L) for a pressure vessel application. Detail studies were conducted for the PWHT influence on the micrstructure and intergranular corrosion characteristics of the overlaid weld metal as well as initiation of hydrogen embrittlement crack(or Disbonding) when welded metal are exposed to the hydrogen atmosphere. Hydrogen was experimentally charged to the overlaid weld metal in order to study PWHT effect on the susceptibility of hydrogen embrittlement crack. The results of this research are as follows: 1. At the bond region, austenite grain of the stainless steel side became coarsed and Cr23C6 type carbide was precipitated at the coarsed austenitic grain boundaries. Intergranular Corrosion width(by Straiss test) increased with increasing PWHT temperature and PWHT time.

• Journal of Welding and Joining
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• v.31 no.4
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• pp.62-66
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• 2013

Overlay welding is carried out to improve the corrosion resistance, wear resistance and heat resistance on the surface of the chemical plant and steelmaking plant structures. In overlay welding, control of the bead size and the temperature distribution of weldment are particularly important because that is directly connected to the improvement of quality and productivity. The aim of this study is to model the welding heat source that is very useful to analyze the bead size and temperature distribution of weldment. To find the welding heat source model, numerical analyses are performed by using FE software MSC-marc.