• Journal of Welding and Joining
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• v.16 no.5
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• pp.93-99
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• 1998

Effects of gas formers of MgCO$_3$, CaCO$_3$ and Li$_2$CO$_3$ on the spattering phenomena were investigated for non-shielded flux cored arc welding. Spattering phenomena were pictured using high speed camera as a speed of 3000 frames per sec. As experimental results, spattering modes were classified into 4 types. The modes were spattering by arc force, gas explosion, short circuit and pore escape. The amount of spatters by arc force was 30%, gas blowing force was 40%, short circuit 10%, pore escape was 10% and others were 10%. When Li$_2$CO$_3$ was added, the amount of spatters was largest, and it decreased in the order of CaCO$_3$ and MgCO$_3$.

• 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.

• Journal of Welding and Joining
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• v.17 no.1
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• pp.62-70
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• 1999

Since various parameters including the welding conditions and material properties are involved in metal transfer, it is difficult to figure out the effects of each parameter. In this study, dimensional analysis in performed to reduce the number of the parameters and to reveal the effect of each parameter on metal transfer. Dimensionless parameters are derived based on the inertia force and surface tension, and their contributions on metal transfer are estimated by analyzing the calculated results using the volume of fluid (VOF) method. Among several dimensionless parameters, $N_{SE}(=$\mu$_{0}I^{2}/d_{w}${\gamma}$)$ which represents the ratio of the electromagnetic force to surface tension, is found to be appropriate to describe metal transfer and estimate the transition current. Predicted results of transition current and drop size are in reasonably good agreements with available experimental date which show the validity of proposed dimensional analysis.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.23-25
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• 2005

This paper presents a numerical analysis method for predicting welding-induced deformation and buckling in ship block with thin plates. The numerical method is particularized on evaluating buckling distortion induced by welding. There are two steps in the numerical analysis model. One is to solve the eigenvalue problem of welded structure by elastic buckling analysis, and the other is to solve the welding-induced buckling distortion of welded structure by post-mechanical analysis. Equivalent force method was used for considering the shrinkage force by welding in the analysis model.

• Journal of Welding and Joining
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• v.25 no.2
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• pp.49-54
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• 2007

Since the wall thickness can be up to 6" or greater, welds must be made in many layers, each layer containing several passes. However, the welding time for the conventional welding processes such as SAW(Submerged Arc Welding) and FCAW(Flux Cored Arc Welding) can be required many hours. The aim of this paper is to develop a high speed welding system with multi-torch and laser vision sensor for increasing the production speed on the line and to remove the need for the operator so that the system can run automatically for the complete multi-torch multi-layer weld. It was shown that the developed laser vision sensor and analysis of arc blow for multi-torch were effective for multi-pass seam tracking and stable arc. A new automated multi-torch welding systems for thick wall applications has been proved in several production lines.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.393-394
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• 2010

• Proceedings of the KWS Conference
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• 2006.10a
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• pp.268-270
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• 2006

• Journal of Welding and Joining
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• v.19 no.4
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• pp.391-398
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• 2001

MIAB welding method uses a rotating arc as its heat source and is known to be efficient in pipe butt welding. The arc is rotated around the weld line by the electro-magnetic force resulting from the interaction of arc current and magnetic field. This paper is concerned with the experiment of initial stage for process control, monitoring for weld quality, and the design of coil system which is efficient of flux generation and concentration. A coil system for the generation of magnetic flux was designed and constructed. Magnetic flux density and arc rotating behavior are important factors in MIAB welding, so the relations between these factors and process parameters were investigated. Various experiments were performed for the steel pipes(48.1mm O.D and 2.0mm thickness). The magnetic flux density is increased by increasing exciting current and decreasing gap size. The maximum of arc rotating frequency is affected by exciting current and gap size. However, the variations of arc rotating frequency during welding and then the melting process are mainly influenced by welding current. Thus, it is considered that the results of this study can be used as important data on the monitoring for weld quality and the design of efficient coil system.

• Journal of Welding and Joining
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• v.17 no.2
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• pp.44-52
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• 1999

This study deals with spot weld ability of dissimilar aluminum alloy sheets in order to take advantage of its lightweight and strength. The paper also shows the relationship between weld elements(i.e. current, welding time and tip force) and weld quality on the resistance spot weld part of the same and dissimilar Al alloy. The conclusions are: (1) Because of excessive tip force, deep indentation remained at the Al 5182 side which is lower stiffness at the dissimilar Al alloy. (2) Weld quality (i.e. tensile shear strength) of dissimilar Al alloy is superior to that of the same Al 6061 alloy. (3) As long cycles, fatigue life of spot weld specimen on dissimilar Al alloy sheets was better than that of the same Al alloy.

• Proceedings of the KWS Conference
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• 1999.10a
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• pp.327-330
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• 1999