• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.5
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• pp.110-117
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• 2004

In automatic welding process using a robot, seam tracking is one of the important parts. Sensor for seam tracking is divided broadly into two categories as non contact sensor and contact sensor. The arc sensor is one of the non contact sensors, and it can be applied in weaving arc and rotating arc welding process. In such the arc sensors, rotating arc sensor can be applied to high speed welding over tens of Hz. The decrease of self regulation by high rotating speed causes to improve accuracy and response of sensor. In this study, fuzzy controller was used to track the seam for the $CO_2$ arc welding which had unstable arc. It could be shown that the rotating arc sensor was better than the weaving arc sensor.

• 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$_3$.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.189-192
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• 1998

• Journal of Welding and Joining
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• v.22 no.6
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• pp.14-18
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• 2004

• Journal of Welding and Joining
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• v.21 no.3
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• pp.35-39
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• 2003

Laser welding has good characteristics such as high density energy, high speed and short heating time, as compared with conventional arc welding. The joint of laser welding also has good mechanical characteristics in general. However, relevant research is not sufficient to understand laser welding in the view point of mechanics until a recent date. In this paper, numerical simulation has been conducted to analyze distribution of welding residual stresses. Welding residual stresses of specimen have been measured by using sectioning method to compare the results between simulation and experiment.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.8-12
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• 2012

Application for laser welding have increased steadily in recent years due to its benefits such as high speed, high productivity and high density energy heat source. In this study, the influence of welding parameters was investigated on penetration characteristics, mechanical properties including formability test in disk laser welded 1000MPa class steels. A shielding gas was used and bead-on-plate test was performed with various welding speeds. The main welding test was performed by butt welding with various welding speeds at 2.5 kW laser power.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.62-67
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• 2017

The automotive industry is in constant pursuit of alternative materials and processes to address the ever changing needs of their customers and the environment. Applications of laser welding have increased steadily in recent years due to its benefits including high speed, high productivity, and high energy density of heat source. This paper investigated the relationship between laser welding parameters and penetration characteristics. The Welding power was fixed at 5kW and welding speeds were varied for the thickness of the workpiece material. Full penetration occurred in the energy per unit area of $21J/mm^2$. The hardness of the weld zone was different for each strength of the workpiece material, however the lowest hardness values were the same in the heat-affected zone.

• Laser Solutions
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• v.4 no.2
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• pp.1-12
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• 2001

This study has been performed to evaluate basic characteristics of CW-CO$_2$ laser welding process of A5083 and A7N01 Al alloy. The effect of welding parameters, such as shielding gas, gas flow rate, laser power and welding speed on the bead shape and porosity from bead on plate welding tests have been investigated. Welds shielded by He gas had deeper penetration and better bead shape than those shielded by Ar. The penetration depth was augmented with the increase of laser Power and the decrease of welding speed. Welds of A7N01 alloy had deeper penetration than those of A5083 alloy In beads of A5083 alloy which has deeper penetration, the volume fraction of porosities was high due to the number of its was few, but size of its was larger. The case of deeper penetration beads of A7N01 alloy, the porosity reduced under relatively higher power The Volume fraction of porosities in weld of A5083 alloy was significantly higher than that in weld of A7N01 alloy.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.8
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• pp.1076-1082
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• 2012

Today the welding for LNG carrier is known to be possible using arc and plasma arc welding process. But because of the lower energy density, arc welding is inevitable to multi-pass welding for thick plate and has a limit of welding speed compared to laser which is high energy density heat source. When thick plate is welded, weld defect by multi-pass welding and heat-affected zone by high heat-input were formed. Therefore one-pass welding by key-hole has been considered to work out the problems. It is possible for Laser, electron beam, plasma process to do key-hole welding. Nowadays, plasma process has been used for welding membrane of cargo tank for LNG carrier instead of arc process. Recently, many studies have examined to apply laser process to welding of membrane. In this paper, weldability, microstructure and mechanical properties of stainless steel for LNG carrier welded by fiber laser were compared to those by plasma. As a result, although the laser welding has several times faster speed, similar properties and smaller weld and heat affected zone were obtained. Consequently, this study proves the superiority of fiber laser welding for LNG carrier.

• Journal of Welding and Joining
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• v.33 no.1
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• pp.54-60
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• 2015

Laser-arc hybrid welding has been considered as an effective pipe girth welding process since early 2000's. Tolerance for fit-up offsets such as gap and edge misalignment is one of most important requirements in pipe girth laser-arc hybrid welding, and several approaches using parameter optimization, a laser beam scanning and an arc oscillation have been tried. However the required offset tolerance has not been fully accomplished up to now and laser-arc hybrid welding has not been widely applied in pipeline construction than expected, despite of its high welding speed and deep penetration. In this study, internal welding was adopted to ensure the offset tolerance and sound back bead. The effect of welding parameters on bead shape was investigated at the flat position. Also tolerances for gap and edge misalignment were verified as 0.5 mm and 2.0 mm, respectively. The position welding trials were conducted at several welding positions from the flat to the overhead position in a downward direction. With the fixed welding speed, arc current for gas metal arc welding current and laser output power, adequate welding voltages for gas metal arc welding were suggested for each position.