• Title/Summary/Keyword: Short Circuit Transfer

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Effect of Si on Arc Stability of MAG Welding (MAG용접의 Arc안정성에 미치는 Si의 영향)

  • 안영호;이종봉;엄동석
    • Journal of Welding and Joining
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    • v.16 no.6
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    • pp.52-58
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    • 1998
  • The effect of Si content in welding wires on th arc stability was investigate, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing Si content, average arcing time and average short circuit time were increased. Therefore, droplet transfer frequency was decreased, due to the increase of arcing time and peak current at the moment of arc-reiginition was increased, due to the increase of short circuit time. In the region of spray transfer, the fluctuations of arc current and arc voltage was the most stable in wire with Si content of about 00.60 wt.%.

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Effect of S on Arc Stability of MAG Welding (MAG용접의 Arc안정성에 미치는 S의 영향)

  • 안영호;이종봉;엄동석
    • Journal of Welding and Joining
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    • v.17 no.1
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    • pp.55-61
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    • 1999
  • The effect of S content in welding wires on the arc stability was investigated, in the region of short circuit transfer and spray transfer. In the region of short circuit transfer, with increasing S content, average arcing time and average short circuit time were decreased. Therefore, droplet transfer frequency was increased, due to the reduction of arcing time and peak current at the moment of arc-reiginition was decreased, due to the decrease of short circuit time. In the region of spray transfer, the fluctuation degree of arc current and arc voltage became more stable, with increasing S content.

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Analysis of Dynamic Behavior in GMAW System (GMA용접 시스템의 동적 거동에 대한 해석)

  • 이재영;최재형;이지혜;유중돈
    • Journal of Welding and Joining
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    • v.18 no.5
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    • pp.41-48
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    • 2000
  • Dynamic behaviors of the GMAW system are simulated using the short-circuit transfer model and the characteristic equations fir the power supply, wire system and arc. The conventional wire equation, which relates the rate change of the wire extension to the wire feed rate and melting rate, is modified to include effects of the molten drop attached at the wire tip. The modified wire equation describes behaviors of the GMAW system more precisely and provides information about the initial bridge volume for short-circuit transfer. The proposed short-circuit model predicts the variation of parameters such as the current, voltage, short-circuit frequency and time considering the effects of the surface tension and electromagnetic force due to current. The calculated results are in broad agreements with the experimental results under the argon shielding condition.

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Relation between Spatter Generation and Waveform factor of $CO_2$ Welding in Short-Circuit Condition ($CO_2$ 용접의 단락이행 조건에서 스패터 발생과 파형인자와의 관계)

  • 김희진;강봉용;이강희;유중돈
    • Journal of Welding and Joining
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    • v.16 no.3
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    • pp.95-101
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    • 1998
  • Waveforms of $CO_2$ gas shielded arc welding in short circuit transfer mode was studied with the waveform analysis program, which can calculate various waveform factors such as number of short circuit event, mean and standard deviation of short circuit time and arc time. The calculated values of these factors were correlated independently or in combination with the spatter generation rate to figure out the most reliable index for evaluating spatter generation and further for arc stability. As a result this study, it was confirmed that the spatter generation tends to decrease with the increase of short circuit frequency. Further to this, it was also found that as the short circuit frequency increases the short circuit event becomes more uniform resulting in the decrease of standard deviations ($\sigma$values) of short circuit time and arc time. This result demonstrated that these factors are strongly correlated with each other and thus any one of these factors can be used for the evaluation index. In the discussion, however, short circuit frequency was proposed for the most practical index in evaluating the arc stability of short circuit transfer mode since it is the one which could be monitored in-process condition without any complex caculation process.

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Effect of Ca on Droplet Transfer Phenomena in GMA Welding (GMAW 용적이행 현상에 미치는 Ca의 영향)

  • 안영호;방국수;이종봉;장내웅
    • Journal of Welding and Joining
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    • v.12 no.4
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    • pp.76-84
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    • 1994
  • Droplet transfer modes due to welding conditions and the effect of Ca in welding wire on droplet transfer were investigated. Droplet transfer mode in CO$_{2}$ welding was classified into 2 modes, that is, short circuit and globular transfer, with increasing welding current and voltage. With increasing Ca content in wire, repulsive pressure due to vaporization of Ca was considerably increased. In short circuit transfer region, arcing time was increased and droplet transfer cycle was decreased, with increasing Ca content. In globular transfer region, welding condition for globular transfer was lower current region, with increasing Ca content.

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Effect of Ti on Spatter Generation of $CO_2$Welding ($CO_2$용접시 Spatter발생에 미치는 Ti의 영향)

  • 안영호;이종봉;방국수;엄동석
    • Journal of Welding and Joining
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    • v.14 no.5
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    • pp.106-112
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    • 1996
  • The effects of Ti addition in welding wire on the spatter generation and the droplet transfer phenomena were investigated. With increasing Ti content the spattering rate was decreased but the ratio of large size spatter (D $\geq$ 1. 0mm) was increased in both short circuit and globular transfer mode of $CO_2$welding. In short circuit transfer region, the arcing time was increased and the droplet transfer frequency was decreased with increasing Ti content In globular transfer region, the transition current and voltage to globular transfer was lowered and the welding condition region for stable globular transfer was widened with increasing Ti content.

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Effect of S on Spatter Generation and Droplet Transfer Phenomena of MAG Welding (MAG용접의 스패터 발생 및 용적이행현상에 미치는 S의 영향)

  • 안영호;이종봉;최원규
    • Journal of Welding and Joining
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    • v.19 no.5
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    • pp.486-491
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    • 2001
  • The effect of S content in welding wires on spattering characteristics and droplet transfer phenomena was studied. In MAG welding using 80%Ar-$20%CO_2$ shielding gas, spattering characteristics and droplet transfer phenomena were varied with S content of wire. Sulfur addition in wire reduced surface tension of droplet and weld pool, and made arc more stable in MAG welding. With increasing S content, the spattering ratio and the ratio of large size spatter ($d{\geq}1.0mm$) were reduced in short circuit transfer mode. In spray transfer mode, spattering ratio, however was increased when sulfur was added more than 0.020wt.% because surface tension of droplets and weld pool was reduced too much even though arc stability was improved.

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A Study on the Back Bead control by Using Short Circuit Frequency in GMA Welding of Sheet Metal (박판 GMA 용접에서 단락 주파수를 이용한 이면비드의 제어에 관한 연구)

  • 안재현;김재웅
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.75-84
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    • 1995
  • In GMA welding of sheet metal, the short circuit metal transfer mdoe is preferred because of its low heat input and capability of bridging the root gap. The molten electrode is transferred to the workpiece during repectitive short circuit in the model. The waveform of welding current or voltage and the frequency of short circuiting are affected by a number of factors including: magnitude of welding current and voltage, root gap, electrode extension, power supply characteristics, and so on. In this study experimental models were proposed, which are able to determine the relationship between the root gap and short circuit frequency and the relationship between the root gap and appropriate welding speed that produces the good quality of back bead without burn through. Using the experimental models, the root gap can be obtained from measuring the short circuit frequency, and then the appropriate weldig speed to the root gap can be determined. Thus a back bead control system was constructed by controlling the welding speed for maintaining the quality of back bead. The developed system has shown the successful capability of back bead control.

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Effect of Metal Transfer Mode on Spatter Generation of $CO_2$ Welding ($CO_2$ 용접의 스패터 발생에 미치는 용적이행 모드의 영향)

  • 강봉용;김희진
    • Journal of Welding and Joining
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    • v.15 no.2
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    • pp.72-80
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    • 1997
  • The spatter generation rate of GMA welding with $CO_2$ gas shielding was measured with the change of welding conditions such as wire feeding rate and welding voltage and then the results were analized with the accompanying changes in metal transfer mode and in bead geometry. The spatter generation rate (SGR) was relatively low not only wit the short circuit transfer but with the truely globular transfer mode. However, the SGR resulted with the mixed mode were consistantly high. The resultant wave pattern of mixed mode was due to the coexistance of short-circuit and globular transfer and characterized by the frequent appearance of instantaneous short circuit. Considering the result of SGR and that of bead geometry, it could be concluded that when the wire feeding rate (or welding current) was either low or high, the optimum bead shape could be obtained along with the low spatter generation. However, in the middle range of wire feeding rate, the optimum bead shape was only obtained in the mixed mode condition resulting in the high spatter generation.

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Dynamic Analysis of Metal Transfer using VOF Method in GMAW (II) - Short Circuit Transfer Mode - (VOF 방법을 이용한 GMA 용접의 금속 이행에 관한 동적 해석 (II) - 단락 이행 모드의 해석 -)

  • 최상균;고성훈;유중돈;김희진
    • Journal of Welding and Joining
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    • v.15 no.3
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    • pp.47-55
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    • 1997
  • Dynamic characteristics of the short circuit mode are investigated using the Volume of Fluid (VOF) method. When the initial molten drop volume, contact area and wire feed rate are given, rate change of the molten bridge profiles, pressure and velocity distributions are predicted. The electromagnetic force with proper boundary conditions are included in the formulation to consider the effects of welding current. It is found that the molten metal is transferred to the weld pool mainly due to the pressure difference caused by the curvatures in the initial stage, and electromagnetic force becomes dominant factor in the final stage of short circuit transfer. Necking occurs at the contact position between the molten drop and weld pool, and the initial molten drop volume and welding current have significant effects on break-up time.

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