• Journal of Welding and Joining
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• 제25권6호
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• pp.27-29
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• 2007

GMA 용접 시스템을 시뮬레이션 하기 위한 요소 기술과 문제점에 대하여 간단하게 설명하였다. 현재까지의 연구 결과로부터 GMA 용접 시스템을 해석하는데 필요한 원리 및 기본 방정식은 거의 알려진 상태이지만, 이와 같은 시뮬레이션은 이상적인 조건에서 계산한 결과로서 실제와는 차이가 발생한다. 이와 같은 오차는 실험을 통하여 지속적으로 수정 및 보완되어야 시뮬레이션의 정확도를 향상시킬 수 있으며, 향후 시뮬레이션이 용접 생산성과 품질을 향상시키는 도구로 활용될 수 있기를 기대한다.

• Journal of Welding and Joining
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• 제25권6호
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• pp.4-10
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• 2007

• Journal of Welding and Joining
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• 제8권1호
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• pp.31-42
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• 1990

Arc must be stable during welding first of all other factors for obtaining sound weldment, especially in the automation of welding process. Arc stability is somewhat sophisticated phenomenon which is not clearly defined yet. In consumable electrode welding, the voltage and current variation due to metal transfer enables to assess arc stability. Recently, statistical analyses of the voltage and current waveform factors are performed to assess the degress of arc stability which is assessed and controlled by operator's own experience by now. But, considering the increasing need and the trend of automation of welding process, it is necessary to monitor arc stability in real-time. In this sutdy, the modified stability index composed of two voltage and current wvaeform factors (arc time and short circuit time) reduced from four factors (arc time, short circuit time, average arc current and average short circuit current) in Mita's index by the welding electrical circuit modeling is proposed and verified by experiments to be well estimating arc stability in the static sense. Also, the recursive calculation form estimating present arc stability in the dynamic sense is developed for real-time estimation. The results of applying the recursive index during welding show good estimation of arc stability in real-time. Therefore, the results of this study offers the mean for real-time control arc stability.

• Journal of Welding and Joining
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• 제33권4호
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• pp.50-56
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• 2015

In general, discontinuity of metallurgical and structural points of weld zone could decline the fatigue strength. For the lightweight trend, the AHSS application in automotive chassis is in-progress. However, there are few research reports on AHSS welds fatigue strength in especially automotive chassis parts. Therefore, in this study, we evaluated the effects of the factors affecting the AHSS welding fatigue strength. As the result, the stress concentration of weld bead is the most important factor for welding fatigue strength. For the enhancement of welding fatigue strength, we focused on reducing the stress concentration of the welding beads. So, we applied and proved the plasma welding process and GTAW (Gas Tungsten Arc Welding) dressing method. It was verified by uniaxial fatigue specimen, fatigue performance increased from 40 to 60% by applying TIG dressing method compared to the conventional GMAW (Gas Metal Arc Welding). These results could be recommended the enhancement of fatigue performance of AHSS.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제12권5호
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• pp.2019-2024
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• 2011

The effect of the wear of contact tips on the weld beads made by a Gas Metal Arc Welding(GMAW) process was studied. In order to correlate between the wear of tips and beads, the droplet transfer was investigated by a high speed camera and waveform shapes, and the condition of beads was examined by a low magnification camera as well. It was found that the worn contact tip had caused to shift the contact point between the tip and the welding wire which resulted in nonuniform beads. In addition, the worn contact tip had changed the welding resistance and brought about the arc instability during welding.

• Proceedings of the KAIS Fall Conference
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• 한국산학기술학회 2011년도 추계학술논문집 2부
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• pp.394-397
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• 2011

The effects of heat input(1.4~3.2kJ/mm), shielding gas(Ar80%+$CO_2$20%) and postweld heat treatment(PWHT, $600^{\circ}C$, 40hr.) on the TMCP HSB600 steel weldments made by GMAW process were investigated. The tensile strength and CVN impact energy of as-welded specimens decreased with increasing heat input. The fine-grained acicular ferrite was mainly formed in the low heat input while polygonal and side plate ferrites were dominated in the high inputs. High performance steel for bridges requires higher performance in tensile and yield strength, toughness, weldability, etc. Thus, the purpose of the experiment is to study HSB 600 in GMAW.

• The Transactions of the Korean Institute of Power Electronics
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• 제8권4호
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• pp.307-312
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• 2003

Joining thin aluminum alloy is difficult using most welding techniques. Many of problems associated burn-through by the high heat input. Common welding techniques are TIG, MIG, and MIG-PULSE welding. The VP-GMAW provides more control of the heat balance in the welding arc by taking advantage of the different arc characteristics obtained with each of the two polarities. In this paper, we proposed new VP-GMAW method by control DSP 320C32, and the characteristic and experiment result-voltage, current, welding bead, penetration by this method are presented.

• Journal of Welding and Joining
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• 제21권2호
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• pp.50-56
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• 2003

Metal matrix composites(MMC) consist of metal matrix into which is distributed a second solid phase. The normal intension is to develop a material with superior mechanical properties (for example increased toughness, stiffness and wear resistance) compared to those inherent in the matrix component. In this study, WC-12%Co/low carbon steel MMC overlays have been prepared by Gas Metal Arc Welding(GMAW) according to feeding rate of WC-12%Co grit. The macro and microstructures were examined using optical microscopy (OM) and scanning electron microscopy(SEM) each other. The characteristics of hardness and wear resistance have been investigated. WC-12%Co/low carbon steel MMC overlays which have been taken good beads without porosity and cracks were manufactured by method of GMAW. Matrix of overlayed surface was seen as fish bone and faceted dendrite structures. It was known that structures were iron tungsten carbides, Fe$_{6}$W$_{6}$C which have been occurred by melting of WC-12%Co grits. After MMC had been tested by block-roll wear test it was known that WC-12%Co/low carbon steel MMC has a excellent wear resistance by exiting Fe6w6c and WC-12%Co grit. The consequence was that region of overlay with Fe$_{6}$W$_{6}$C phase has been showed a model of adhesive wear, but region of overlay with WC-12%Co grit was restrained as a result of mechanism that wear of WC-12%Co grit is not adhesive but fracture.racture.

• Proceedings of the KWS Conference
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.71-71
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• 2010

SBD (Strain-based design) of pipe lines have gained world-wide attention in recent years. The present research aims to evaluate the fracture characteristics of API (America Petroleum Institute) SBD X100 girth weldment that typically applied for cold climate and deep water offshore, with the focus on the influence of heat input changing with 6kJ/cm and 10kJ/cm from GMAW (Gas Metal Arc Welding). At a low heat input at 6kJ/cm, the weld metal had Multi-phase matrix (Acicular ferrite + Banite + Martensite) that could fill up both fracture toughness and strength as reported previously. Also, the weld metal exhibited 859MPa YS (Yield strength), 108J impact toughness at $-40^{\circ}C$ and 0.52mm CTOD (Crack Tip Open Displacement) at $-10^{\circ}C$. These results can be satisfied with the requirement of API SBD X100 girth weldment and Alaska pipe line project.

• Proceedings of the KWS Conference
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.48-48
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• 2009

Conventionally in pulsed gas metal arc welding (GMAW-P), drop transfer is analyzed with simplest square pulse waveform. While the pulse current is described by four parameters (peak current magnitude and time plus base current magnitude and time), it deviates the real pulse shape. Real pulse can be better idealized by the trapezoidal pulse waveform described by two additional parameters, i.e., current rise and fall rate (dI/dt). Power source response rate is described by these parameters. In this work, the effect of these parameters on drop transfer is predicted by the force displacement model (FDM). While peak current has significant effects on drop detachment, drop transfer is also influenced by the current rise rate. Predictions indicate that the current rise rate can have considerable effects on the size of the detached drop if other pulse parameters are kept constant. FDM is applied to determine peak time for one drop one pulse condition (ODOP) when rests of the pulse parameters are given. The predicted range of ODOP shows good agreement with experimental data.