• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1460-1465
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• 2012

The semi-automatic gas metal arc welding equipment was developed and the weldability of zinc coated steel pipes was evaluated in terms of strength, porosity and welding parameters including shielding gas composition. The good bead appearance and the reduction of porosity in the welds could be possibly obtained by adding $O_2$ to Ar. The strength and joint efficiency of welds made by the semi-automatic welding equipment was about 1.8 times higher compared with welds manually made. The integrity of welds was confirmed by the water pressure test as well, Finally, it is expected that the weld productivity will be enhanced even unskilled welders can produce quality welds by operating the semi-automatic welding equipment.

• Journal of Welding and Joining
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• v.16 no.5
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• pp.119-133
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• 1998

To implement full automation in pipe welding, it si most important to develop special sensors and their related systems which act like human operator when detecting irregular groove conditions. In this study, an automatic pipe Gas Metal Arc Welding (GMAW) system was proposed to full control pipe welding procedure with intelligent sensor systems. A five-axes manipulator was proposed for welding torch to automatically access to exact welding position when pipe size and welding angle were given. Pool status and torch position were measured by using a weld-pool image monitoring and processing technique in root-pass welding for weld seam tracking and weld pool control. To overcome the intensive arc light, pool image was captured at the instance of short circuit of welding power loop. Captured image was processed to determine weld pool shape. For weld seam tracking, the relative distance of a torch position from the pool center was calculated in the extracted pool shape to move torch just onto the groove center. To control penetration of root pas, gap was calculated in the extracted pool image, and then weld conditions were controlled for obtaining appropriate penetration. welding speed was determined with a fuzzy logic, and welding current and voltage were determined from a data base to correspond to the gap. For automatic fill-pass welding, the function of human operator of real time weld seam control can be substituted by a sensor system. In this study, an arc sensor system was proposed based on a fuzzy control logic. Using the proposed automatic system, root-pass welding of pipe which had gap variation was assured to be appropriately controlled in welding conditions and in torch position by showing sound welding result and good seam tracking capability. Fill-pass welding by the proposed system also showed very successful result by tracking along the offset welding line without any control of human operator.

• Journal of Welding and Joining
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• v.13 no.1
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• pp.156-166
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• 1995

Experimental models which are able to determine the deviation between weld line and weaving center by measuring the weld current during welding were proposed for the gas metal arc welding process. The models were used for developing a weld seam tracking system which controls the weaving speed of a welding torch. However, it was revealed that the tracking result of the system is affected by the welding conditions. Thus an arc sensor system was developed by using fuzzy control approach for overcoming the difficulty of modelling the nonlinear process. The rule base and parameters of the fuzzy control system were determined on the basis of the results of experiments. This fuzzy control system has shown the successful tracking capability for the wide operating range of welding conditions.

• Journal of Welding and Joining
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• v.8 no.1
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• pp.23-30
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• 1990

The robotic welding has been adapted positively in many welding shops forthe purpose of improving the welding efficiency and liberating operators from the severe working atmosphere. But for a large-size structure with thick plates like ship-building and every kind of plants manufacturing, the application of the arc welding robots is not established yet. The reason is assumed that the conventional arc welding robots are not adaptive for multi-pass welding of thick plates whose grooves are not so accurate. As one solution to this problem, a guidance system which uses the welding arc itself as a sensor is largely used. In this study the velocity controller which changes the tip to workpiece distance for regulating the weld proposed. The proportional and integral gain of velocity controller were determined by using the computer simulation of the control system, and the simulation results compared with the experimental ones. It was revealed that the developed control system using the arc sensor principle has a good capability of tracking the weld joint, although some more studies will be needed to refine the model of arc current.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.199-200
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• 2012

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.512-517
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• 2009

Extruded aluminium panels have been widely used for railway vehicle structures because -of their light specific weight and other merits. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used due to its lots of advantage. In this study aluminium A6005 which is used for car body structures was chosen. The influences of main parameters on mechanical properties such as: pin (tool) rotating speed, pin transition speed, shoulder, diameter, pin length and tilting angle were examined. Optical microscope and scanning electron microscope (SEM) observation, micro hardness tests, and tensile tests were carried out.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.871-877
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• 2008

It is important to investigate the relationship between weld process parameters and weld bead geometry for adaptive arc robot welding. Howeve, it is difficult to predict an exact back-bead owing to gap in process of butt welding. In this paper, the quantitative prediction system to specify the relationship external weld conditions and weld bead geometry was developed to get suitable back-bead in butt welding which is widely applied on industrial field. Multiple regression analysis for the prediction of process parameters was used as the research method. And, the results of the prediction method were compared and analyzed.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.162-170
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• 2001

In torch weaving in arc welding on V groove, the heat input distribution on groove surface is a main factor determining the bead shape and the weld quality with and without the weld defects such as undercut, overlap, etc. In this study, we calculate the heat input varying with the welding current, arc voltage, welding speed and the touch weaving condition using numerical method. And we investigate the heat input distribution on groove surface while applying the various grooves having 2 dimensional heat sources.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.221-223
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• 2003

Effects of electromagnetic force which is one of the most important factor of metal transfer that affects bead geometry and microstructure of weld metal in GMAW(gas metal arc welding). In this paper, different ways of external electromagnetic forces were applied on GMAW process and their effects on the welding were studied. On certain conditions, better bead geometry, better influence on the arc and metal transfer mode and higher welding efficiency could be obtained. Experimental methods and their results will be presented.

• Proceedings of the Korean Reliability Society Conference
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• 2004.07a
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• pp.139-145
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• 2004

용접산업이 발전함에 따라 가스메탈아크 용접에서 고내마모성의 콘택트 팁이 요구되어지고 있다. 현재 국내외에서는 콘택트팁에 대한 수명평가 기준이 없으며, 일부 업계에서 자체 규격을 제정하여 운용하고 있지만 근거가 명확하지 않다. 따라서 본 연구에서는 콘택트팁의 신뢰성 평가기준을 제정하고자 하였다. 팁의 주요 파손기구로는 고온 마찰마모, 전기적 에로존, 번백 등이 있다. 신뢰성 평가는 경도 시험, 열처리 후 경도, 용접 마모, 전기전도도를 시험으로 구성되었다. 팁의 수명은 마모가 45%에 도달했을 경우 송급된 와이어 총 길이로 하였으며, 4시간까지 마모시험 한 결과를 근거로하여 한계수명을 추정하였다. 본 연구에서는 세 가지 조성의 다섯 가지의 콘택트팁에 대하여 4시간동안 내마모성 실험을 하였으며, 마모정도는 1시간 단위로 면적비를 백분율로 환산하여 측정하였다. 실험 결과 가공경화형팁은 1시간이내에 재결정 및 입자성장에 의한 경도 저하로 가공경화가 팁 수명에 지속적 영향을 주지 못하였다. 반면, 석출경화형팁은 석출경화 효과가 지속되어 가공경화형팁보다 수명이 향상 되었다.