• Journal of Welding and Joining
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• v.15 no.5
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• pp.92-103
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• 1997

The purpose of this study is to improve the wear resistance and hardness of Al alloy by making a formation of the thick surface hardening layers. The thick surface hardening layers were formed by PTAW(Plasma Transferred Arc Welding), with the addition of metal powders (Cu), ceramics powders (NbC, TiC), and mixture powders (Cu+NbC) in Al alloy (A1050, A5083). Mechanical properties of overlaid layers (wear resistance, hardness) were investigated in relation to the microstructure. The results obtained are summarized as follows: The depth of penetration was increased with increasing powder feeding rate. It is considered that these increase were due to the thermal pinch effect by the addition of powders, especially, for the Cu powders, were due to the heat of reaction with the matrix. The hardness and wear resistance of overlaid layers were improved with increasing powder feeding rate. For the Cu powders, it is considered that these increase were due to the increase of the formation of ${\theta}(CuAl_2)$ phase with increasing feeding rate of Cu powers.

• Journal of Welding and Joining
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• v.26 no.4
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• pp.44-49
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• 2008

Generally, wear plate is steel plate having improved surface contact strength and impact strength by surface hardening which is welded using materials with good corrosion resistance, wear resistance and thermal resistance property. CFP GMAW(Compound Filler Plate Gas Metal Arc Welding) is the cladding method using GMAW with the CFP, which is bound with waterglass, on the substrate. It has advantages of reducing compound powder loss, uniform penetration, and preventing hardness decrease. To develope mass production technique of CFP GMAW process for production of high quality wear plate, the method for controling shallow penetration and increasing productivity is required. In this study, twin torch method applied to CFP GMAW process for increasing productivity. And the method was developed by controling penetration control, CFP dry time, gas formation flux and water glass concentration. As a result, applying twin torch method to CFP GMAW process was possible and high quality wide bead could be made without overlap joint.

• Journal of Welding and Joining
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• v.7 no.2
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• pp.49-59
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• 1989

The effect of non-metallic inclusions on the HAZ hydrogen induced cracking was investigated. Quench and temper high tensile strength steels containing various sulphur contents were employed. The sulphur contents range between 0.007% and 0.040%. Non-metallic inclusions were mainly MnS type sylphide and Mn-Al-Si type. The sensitivity of HAZ delayed cracking was evaluated by implant testing. Diffusible hydrogen content was varied by controlling the moisture absorbing condition of manual arc welding electrodes. The one was asreceived condition, the other was dipping the electrodes in the water for ten minutes. The main results obtained were as follows; 1) The results of implant test showed that critical stress increased with increasing S content up to 0.013%. But steel containing 0.040%S showed lower critical stress than that of 0.013% S. These result suggest that there will be optimum S content to prevent HAZ delayed cracking of high strength steels. 2) Under the lower D.H.C. level, critical stress was increased with rolling reduction, but higher D.H.C. level, effect of rolling reduction was not recognized.

• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1805-1815
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• 2019

While nickel-based alloys have been widely used for power plants due to corrosion resistance and good mechanical properties, during the last couple of decades, failures of nuclear components increased gradually. One of main degradation mechanisms was primary water stress corrosion cracking at dissimilar metal welds of piping and reactor head penetrations. In this context, precise estimation of welding effects became an important issue for ensuring reliability of them. The present study deals with a series of finite element analyses and crack growth rate evaluation of Alloys 690/152. Firstly, variation of residual stresses and equivalent plastic strains was simulated taking into account welding of a cylindrical block. Subsequently, extraction and pre-cracking of compact tension (CT) specimens were considered from different locations of the block. Finally, crack growth curves of the alloys and heat affected zone were developed based on analyses results combined with experimental data in references. Characteristics of crack growth behaviors were also discussed in relation to mechanical and fracture parameters.

• Proceedings of the KWS Conference
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• v.43
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• pp.211-212
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• 2004

Characteristics of the wear resistance thermal sprayed coatings was investigated in order to determine proper coating process. Hardness evaluation and microstructural observation were conducted to find relationship between coating characteristics and its wear performance. It was found that HVOF process would give better properties than arc thermal process in terms of hardness and adhesion strength which resultantly determine wear performance of the coatings.

• Proceedings of the KWS Conference
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• v.43
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• pp.49-51
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• 2004

레이저 아크 하이브리드 용접에서 보호가스로 헬륨을 사용하였을 때 레이저에 의해 발생하는 금속 증기가 아크 플라즈마의 거동에 미치는 영향에 관하여 시뮬레이션 하였다. 해석에 필요한 기본적인 물성치들은 헬륨과 금속 증기의 부분압에 따라 비율로서 결정하였고 아르곤을 사용하였을 때와 비교하여 헬륨 플라즈마의 특성을 파악하였다. 또한 보호가스의 종류에 따라 레이저 빔의 흡수율을 계산하여 고옥의 플라즈마가 발생할 때 헬륨 보호가스가 적당함을 보였다.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2512-2514
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• 1999

A new zero voltage and zero current switching(ZVZCS) full bridge DC-DC converter with transformer isolation is proposed for arc welding machines. The proposed DC-DC converter uses an auxiliary transformer to obtain ZCS for leading leg, which provides load current control capability even in short circuit condition. The auxiliary circuit also operates in ZVZCS mode. The power rating of the auxiliary transformer is about 10% of the main transformer. The operation is verified by experiments for 12[KW] prototype.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1992.04b
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• pp.91-101
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• 1992

본 연구에서는 용접선 추출의 방법으로 현재 많이 사용되고 있는 용접선을 따라 연속적으로 이미지를 얻어 처리하는 사전관찰(preview)기법을 개선하여 용접모재를 한번에 촬영(snapshot)하여 화상처리를 거친 후 용접정보가 들어 있는 CAD database와 비교, 매칭시켜 필요한 용접정보를 획득하는 새로운 방법을 제시한다. 또한 정확한 꼭지점을 추출하기 위해서는 정확한 직선식이 필요한데 이의 계산에는 허프변환(Hough Transform)이 이용되고 있지만 계산시간이 많이 소요되며 부정확하다. 계산시간의 감소 및 정확도의 향상을 위해 기존의 허프변환(Hough Transform)을 개선한 수정된 허프변환(Modified HoughTranform)을 개발하였다.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.109-111
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• 2004

아크 플라즈마의 온도 분포를 측정하는 방법으로 개발된 CCD 카메라를 이용한 온도 측정 방법을 비대칭 플라즈마의 온도 분포 측정에 적용하기 위해 비대칭 플라즈마의 데이터 변환에 이용 가능한 아벨 역산 방법을 개발하였다. 비대칭 플라즈마 중 V-groove 상의 아크는 타원형의 플라즈마로 볼 수가 있으므로 타원형의 단면을 가지는 플라즈마에 대해 온도 측정을 수행하고 그 결과로서 모재로 전달되는 아크의 열속(heat flux)의 분포를 예측 할 수 있었다.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.27-29
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• 2003

최근 레이저와 아크를 동시에 사용하여 용접 속도와 품질을 향상시킬 수 있는 하이브리드 용접 기술이 개발되어 활발히 연구가 진행되고 있다. 레이저와 아크를 동시에 사용하게 되면 각각의 열원이 서로 영향을 주어 새로운 용접 열원으로서 동작하게 되는데 특히 레이저에 의해서 발생하는 모재의 금속 증기는 아크 플라즈마의 안정화를 가져오는 것으로 알려져 있다. 또한 금속 증기 속의 이온과 전자가 아크 플라즈마의 음극점을 형성하는데 도움을 줌으로써 플라즈마의 국부적인 온도 상승을 가져오게 된다. 본 연구에서는 effective electrical potential 개념을 도입하여 이러한 현상을 해석하였고 용접 조건에 따른 플라즈마의 거동 변화를 시뮬레이션 하였다.