• Journal of Welding and Joining
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• v.21 no.2
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• pp.57-63
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• 2003

Since new types of vehicles or structures made from thin aluminum alloy are under rapid development and some products are already on the market, welding of aluminium sheet is increasing. MIG(Metal Inert Gas), MIG-Pulse, TIG(Tungsten Inert Gas) welding are the typical Ai welding. MIG welding has the advantage of high speed, but it is difficult to apply to the thin plate, because of bum-through by the high heat input and spatter. MIG-Pulse welding can weld without spatter and burn-through, but when the gap exists at the welding joint, there is quite a possibility of bum-through. TIG welding is difficult to weld at a high speed. AC Pulse welding alternates between DCEP(Direct Current Electrode Positive) and DCEN(Direct Current Electrode Negative). DCEN is higher wire melting rate than DCEP, while lower temperature of droplet than DCEP. In AC Pulse welding, far fixed welding current, wire melting rate increases as the EN ratio increases. For fixed wire feed rate, welding current decreases as the EN ratio increases. Because of these features, the temperature of droplet, the depth of penetration, the width of bead decrease and the reinforcement height increases as EN ratio increases, and these are able to weld at a high speed, lower heat input. It is the purpose of this study that design of AC pulse current waveform for MIG welding of Al sheet and estimation of output characteristic.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.69-76
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• 2005

Recently, application of arc welding to galvanized carbon steel sheet is on the increasing Ould in the fields of automobile and construction industries. In arc welding process, zinc is evaporated in weld pool, even under the appropriate welding condition and produce blowhole and/or pit. Zinc gas cause instability of arc and increase spatter and fume. This research is purposed to minimize the heat-input and the formation of porosities in the welded joint of the galvanized carbon steel sheet using variable polarity AC wave pulse MIG welding system. An appropriate welding condition which showed low spatter and good bead appearance was acquired by applying the AC pulse MIG welding machine to DC duplicated MIG welding with the solid wire. When oxygen gas was added to shield gas of MIG welding for galvanized steel sheet, arc length was increased and arc stability was improved. In the AC duplicated welding, the loss of galvanized layer was decreased as the amount of heat-input was decreased when the EN ratio was increased under the condition that average welding current was evenly set.

• Journal of Welding and Joining
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• v.21 no.4
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• pp.56-62
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• 2003

MIG brazing is used for many parts without melting base metal because of high productivity. Pulsed MIG brazing can be used to further reduce heat input and to improve the process stability. However, a significant amount of zinc in galvanized sheet steel is burned off in the area of brazes. Therefore, the brazing method to reduce the heat input is needed. In the brazing for galvanized sheet steel, variable polarity AC pulse MIG arc brazing can be applied to more decrease the heat input by setting EN-ratio adequately. In this research, we studied for the variable polarity AC pulse MIG arc brazing to decrease the heat input by using ERCuSi-A wire. As the result of increasing EN-ratio, melting ratio of base metal and burning off of zinc were reduced in galvanized sheet steel.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.10
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• pp.141-149
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• 2008

Because aluminum has a lighter weight and higher strength than iron, it is frequently used in the transportation industry for the purpose of reducing the weight of a chassis, and thereby increasing fuel efficiency. However, there are some difficulties with arc welding aluminum due to its lower melting point, high thermal conductivity and oxidation coating on its surface. This study proposed using superposition ac pulse MIG arc welding, which has been improved from the pulse waveform of conventional MIG welding. A MIG arc welding power source was developed to test the effectiveness of this method.

• Proceedings of the KWS Conference
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• 2002.05a
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• pp.43-45
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• 2002

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.11a
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• pp.88-91
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• 2001

New type of vehicles made from thin aluminum alloy are under rapid development and some product are already on the market, but when welding sheet metal joint of aluminum alloy, the main problem are burn-through by the high heat input. The purpose of this study, it is to prevent the burn-through and to shallow penetration that AC pulse welding has diminish the penetration and to lower the droplet temperature at Al sheet metal welding. In this study, we observed the bead appearance and whether it was appeared burn through or not , as the variation of the root gap in the lap and butt-joint welding process.

• Proceedings of the KWS Conference
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• 2001.10a
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• pp.15-18
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• 2001

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.31-31
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• 2009

최근 전세계적으로 유가상승 및 환경에 대한 관심이 증대되면서 자동차 업계에서는 차량 경량화를 통한 연비향상에 대한 연구가 활발히 진행되고 있다. 대표적인 기술개발 사례로서 초경량 철강 차체의 개발을 들 수 있다. 이는 고장력강을 적용함으로써 강성을 증대시킴과 동시에 두께감소에 의한 경량화를 이루고자 추진되고 있다. 하지만 고장력강은 자체의 높은 강성을 지니고 있는 반면, 일반 강종에 비해서 스프링백이 크고 용접성도 많이 떨어지는 제약을 안고 있다. 아크 용접법 중 하나인 AC pulse MIG 용접은 DCEP (direct current electrode positive) 와 DCEN (direct current electrode positive) 구간이 주기적으로 반복하는 용접법으로 스패터 발생이 거의 없으며 특히 갭 접합성이 우수하여 자동차 차체 조립공정에 적용되고 있다. 본 연구에서는 자동차 차체용 AHSS 소재의 겹치기 용접 실험을 통해 실제 생산라인에서 용접 이음부에 발생되는 갭에 대해 강건한 용접 공정 조건을 제시하였다. 먼저 고속카메라 촬영을 통해 AC pulse MIG 용접에서 EN ratio 변화에 따른 와이어 용융현상을 분석 하였으며 단면마크로, 인장시험, 인장 파단면 분석을 통해 겹치기 용접에서 0~2mm 사이의 갭 발생에 강건한 용접 조선을 제시하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.4
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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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• v.26 no.6
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• pp.4-7
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• 2008