• Title/Summary/Keyword: Molten Pool

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A Study on the Welding Current in Butt Joint P-GMA Welding with Acute Groove Angles (작은 그루브 각을 가지는 맞대기 P-GMA 용접에서의 용접전류에 관한 연구)

  • Kim, Ryoon-Han;Na, Suck-Joo;Kim, Cheol-Hee
    • Journal of Welding and Joining
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    • v.28 no.4
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    • pp.55-60
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    • 2010
  • The purpose of this paper is to propose a mathematical model of welding current for the P-GMAW by modifying the well known GMAW model. Welding power circuit is simply modeled as a RL electric circuit and solved as an ODE equation. The welding current depends on the joint shape, molten pool and welding parameters. To compare the molten pool effect to the welding current, CFD numerical simulation technique was adopted. Welding experiment is also conducted with the same welding parameters as used in numerical simulations to verify the proposed welding current model. The current model which is considered molten pool shape, is more fit to experiment result.

A Study on the Arc Characteristics in Butt Joint P-GMA Welding with Acute Groove Angles (작은 그루브 각을 가지는 맞대기 P-GMA 용접에서의 용접아크에 관한 연구)

  • Kim, Ryoon-Han;Na, Suck-Joo;Kim, Cheol-Hee
    • Proceedings of the KWS Conference
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    • pp.53-53
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    • 2010
  • The purpose of this paper is to propose a mathematical model of welding current for the P-GMAW by modifying the well known GMAW model. Welding power circuit is simply modeled as a RL electric circuit and solved as an ODE equation. The welding current depends on the joint shape, molten pool and welding parameters. To compare the molten pool effect to the welding current, CFD numerical simulation technique was adopted. Welding experiment is also conducted with the same welding parameters as used in numerical simulations to verify the proposed welding current model. The current model which is considered molten pool shape, is more fit to experiment result.

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Computational Study of the Mixed Cooling Effects on the In-Vessel Retention of a Molten Pool in a Nuclear Reactor

  • Kim, Byung-Seok;Ahn, Kwang-Il;Sohn, Chang-Hyun
    • Journal of Mechanical Science and Technology
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    • v.18 no.6
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    • pp.990-1001
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    • 2004
  • The retention of a molten pool vessel cooled by internal vessel reflooding and/or external vessel reactor cavity flooding has been considered as one of severe accident management strategies. The present numerical study investigates the effect of both internal and external vessel mixed cooling on an internally heated molten pool. The molten pool is confined in a hemispherical vessel with reference to the thermal behavior of the vessel wall. In this study, our numerical model used a scaled-down reactor vessel of a KSNP (Korea Standard Nuclear Power) reactor design of 1000 MWe (a Pressurized Water Reactor with a large and dry containment). Well-known temperature-dependent boiling heat transfer curves are applied to the internal and external vessel cooling boundaries. Radiative heat transfer has been considered in the case of dry internal vessel boundary condition. Computational results show that the external cooling vessel boundary conditions have better effectiveness than internal vessel cooling in the retention of the melt pool vessel failure.

Control of Molten Pool by Physical Force of Bead Former in TIG Welding of Overhead and Inclined-up Position (위보기 및 경사상진자세의 TIG 용접에서 비드 성형기의 물리적 힘에 의한 용융지 제어)

  • Ham, Hyo-Sik;Ha, Jong-Moon;Lee, Byung-Woo;Cho, Sang-Myung
    • Journal of Welding and Joining
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    • v.28 no.6
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    • pp.21-27
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    • 2010
  • Due to excellent weld quality, orbital welding with TIG is widely applied to pipe welding. But concave back bead is formed easily in overhead and inclined-up position of butt orbital welding. It is difficult to find a paper to overcome this problem. In this study, in order to make convex back bead in overhead and inclined-up position of pipe 5G welding, control method of molten pool was actively investigated. Melt run welds were conducted on thickness 4.0mm SS400 with overhead and inclined-up position and was observed the variation of bead shape after welding with the bead former developed. The height of back bead showed the trend of increase as the distance from molten pool to the bead former was decreased. Also, there is no trend in the bead width of front and back as welding position was changed or the distance from molten pool to the bead former was decreased.

아크 용접에서 구동력에 따른 열 및 물질 유동에 관한 연구

  • 김원훈;나석주
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.27-41
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    • 1996
  • In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

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A Study on Weld Pool Oscillation for Pool Geometry Measurement (완전용입 풀의 진동을 이용한 형상측정에 관한 연구)

  • 유중돈
    • Journal of Welding and Joining
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    • v.11 no.2
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    • pp.62-73
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    • 1993
  • Weld pool oscillation for the full-penetration GTA welding process was investigated for its possible application to weld penetration control through theoretical modeling and experiment. Energy method was used to estimate the natural frequency of the molten pool having the physically-acceptable weld geometry and oscillation modes. An unique experimental system was built which had the data acquisiton and video capabilities so that the pool oscillation signals and molten pool surfaces could be monitored continuously. Pool oscillation was detected through arc voltage and arc light emission simultaneously. The signal from arc light emission showed good coherence with that from arc voltage, and arc light generated the higher quality signal. The molten pool was found to oscillate in different oscillation modes based on the travel speed and weld geometry. The natural frequency estimated from the theoretical model agreed reasonably well with the experimental results.

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Die Manufacturing and Repair Using Laser-Aided Direct Metal Manufacturing (레이저 직접금속조형(DMM)기술에 의한 금형제작 및 보수)

  • 지해성;서정훈
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.104-107
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    • 2002
  • Direct Metal Manufacturing (DMM) is a new additive process that aims to take die making and metalworking in an entirely new direction. It is the blending of five common technologies : lasers, computer-aided design (CAD), computer-aided manufacturing (CAM), sensors and powder metallurgy. The resulting process creates parts by focusing an industrial laser beam onto a tool-steel work piece or platform to create a molten pool of metal. A small stream of powdered tool-steel metal is then injected into the melt pool to increase the size of the molten pool. By moving the laser beam back and forth, under CNC control, and tracing out a pattern determined by a computerized CAD design, the solid metal part is built line-by-line, one layer at a time. DMM produces improved material properties in less time and at a lower cast than is possible with traditional fabrication.

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A Study on the Arc Characteristics and Weld Pool Analysis of GHTAW under the Space Environment (우주 환경에서 GHTAW 아크 특성과 용융지 해석에 관한 연구)

  • Lee, Sang-Hoon;Na, Suck-Joo
    • Journal of Welding and Joining
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    • v.28 no.4
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    • pp.67-72
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    • 2010
  • The purpose of this paper is to understand the behavior of GHTAW process under the space environment with the experimental and numerical analysis. Gas Hollow Tungsten Arc Welding (GHTAW) using a hollow tungsten electrode was adopted, since the ignition and discharge of a conventional GTAW process is not appropriate to the space environment due to low pressure in space. In order to clarify the phenomena of GHTAW under space environment, an investigation of thermal and physical properties of the GHTAW arc plasma was experimentally performed under low pressure conditions. Furthermore, the molten pool behavior and weldment of GHTAW were understood by CFD-based numerical analysis, based on the models of GHTA heat source, arc pressure and electromagnetic force induced by arc plasma, the characteristics of which were obtained by the captured images of a CCD camera.

Laser-Aided Direct Metal Deposition (DMD) Technology (레이저를 이용한 직접금속조형(DMD) 기술)

  • 지해성;서정훈
    • Korean Journal of Computational Design and Engineering
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    • v.8 no.3
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    • pp.150-156
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    • 2003
  • Direct Metal Deposition (DMD) is a new additive process producing three-dimensional metal components or tools directly from CAD data, which aims to take mold making and metalworking in an entirely new direction. It is the blending of five common technologies: lasers, CAD, CAM, sensors and materials. In the resulting process, alternatively called laser cladding, an industrial laser is used to locally heat a spot on a tool-steel work piece or platform, forming a molten pool of metal. A small stream of powdered tool-steel metal is then injected into the metal pool to increase the size of the molten pool. By moving the laser beam back and forth, under CNC control, and tracing out a pattern determined by a computerized CAD design, the solid metal part is eventually built line-by-line, one layer at a time. DMD produces improved material properties in less time and at a lower cost than is possible with traditional fabrication technologies.

CO₂ Weldability of Zn Coated Steel Sheet(2);Mechanism of Weld Defect Formation (아연도금강판의 CO₂ 용접특성(2);용접결함의 형성기구)

  • Lee, Jong Bong;An, Yeong Ho;Park, Hwa Sun
    • Journal of Welding and Joining
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    • v.18 no.2
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    • pp.191-191
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    • 2000
  • The mechanism of the blowhole and the pit formation in lap-jointed fillet CO₂ arc welds of Zn-coated steel sheet was established by the direct observation of the gas behavior in the molten pool with the high speed camera system. Main conclusions obtained are as follows1) Some blowholes were formed by incomplete back-filling to the pits at the last stage of the solidification. This type of blowhole was formed through four stages of gas in the molten pool, incubation, explosion, back-filling and completion of back-filling stage.2) Most of the pits was back-filled at the last stage of their formation. (Received September 27, 1999)