• Journal of Welding and Joining
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• 제32권6호
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• pp.35-40
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• 2014

The contact tip for gas metal arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. If the contact tip is damaged, it is a cause of lowering the welding productivity due to removal of welding defects and replacement of contact tip. In case of the use of a contact tip for a long time the arc is unstable because the processed hole in the contact tip center is larger, and the variation of aiming position of the welding wire causes a seam tracking error. In this study, gas metal arc welding experiments using contact tip of three different materials were performed. The contact tips with Cu-P, Cu-Cr, and Cu-ODS were used at the experiments, and the welding characteristics by each contact tip were evaluated. After welding contact tip appearance, welding spatter adhesion amount of the nozzle, and weld bead appearance were evaluated. The welding current and welding voltage were measured to verify arc stability during arc welding.

• Journal of Welding and Joining
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• 제31권4호
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• pp.42-46
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• 2013

The contact tip for flux cored arc welding has important functions to transmit the welding current to the wire and to guide the wire to molten pool. A damaged contact tip causes a productivity reduction and a welding quality problem. In this study, the welding experiments for the wear resistance of contact tip regarding flux cored wire types were performed. With two fold type and a seamless type flux cored wires, the wear rates of contact tips were compared. In addition, the wear rate was checked according to the contact tip position.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.1-10
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• 2002

The thermal contact conductance at different temperatures and with different electrode forces and zinc coating morphology was measured by monitoring the infrared emissions from the one dimensionally simulated contact heat transfer experiments. The contact heat transfer coefficients were presented as a function of the harmonic mean temperature of the two contacting surfaces. Using these contact heat transfer coefficients and experimentally measured temperature profiles, the electrical contact resistivities both for the faying interface and electrode-workpiece interface were deduced from the numerical analyses of the one dimension simulation welding. It was found that the average value of the contact heat transfer coefficients for the material with zinc coating (coating weight from 0 g/$mm^2$to 100 g/$mm^2$) ranges from 0.05 W/$mm^2$$^{\circ}C$ to 2.0 W/$mm^2$$^{\circ}C$ in the temperature range above 5$0^{\circ}C$ harmonic mean temperature of the two contacting surfaces. The electrical contact resistivity deduced from the one dimension simulation welding and numerical analyses showed that the ratio of electrical contact resistivity at the laying interface to the electrical contact resistivity at the electrode interface is smaller than one far both bare steel and zinc coated steel.

• Journal of Welding and Joining
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• 제22권4호
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• pp.35-42
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• 2004

Contact tips are required to have a higher resistance to wear and thus to have an extended life time under the advanced GMAW welding process. Several requirements have been specified and employed by domestic industries for selecting their tips for such a purpose. However no attempt has been made to justify their requirements based on the experimental data of wear resistance or life time of contact tips. In this study, five different contact tips with three different compositions were employed for actual GMA welding up to 4 hours and were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. It was further noticed that Cr is an excellent alloying element for improving the wear resistance of contact tips only when it is in an properly aged condition. Initial hardness may play some role in the early stage of wear but not in the later stage of welding because the microstructure of tip changes significantly by the prolonged exposure to welding arc heat. Based on these results, critical review has been made on the current requirements employed by domestic industries. Of importance is that a new guideline has been confirmed to be more reasonable.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2019-2024
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• 2011

GMA용접 공정에서 콘택트팁의 마모가 용접비드에 미치는 영향에 대해서 연구하였다. 콘택트팁과 용접비드 사이의 연관성을 조사하기 위하여 초고속 카메라와 파형분석을 이용하여 용적이행을 관찰하였고, 저 배율의 카메라로 비드의 상태를 관찰하였다. 콘택드팁의 마모는 팁과 용접와이어 사이의 접촉 지점을 변화시켜 결과적으로 불규칙비드를 생성하였다. 이것은 마모된 콘택트팁이 용접시 용접저항의 변화를 초래하여 용접아크 불안정의 원인이 되기 때문이다.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2011년도 춘계학술논문집 2부
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• pp.683-686
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• 2011

The effect of welding material such as welding wires and materials for contact tip on the contact tip wear was investigated. Two types welding wires such as solid and flux cored wire and a variety of contact tips made of Cu-P, Cu-Cr(0.25%), Cu-Cr(1%) and Cu-Cr-Zr were employed for the comparison of wear resistance. It was found that the wear resistance of contact tips materials was Cu-Cr-Zr, Cu-Cr(1%), Cu-Cr(0.25%), Cu-P in order while the solid wire had a better wear resistance than flux cored wire.

• Journal of Welding and Joining
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• 제22권1호
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• pp.43-49
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• 2004

Contact tip is located so near to welding arc that it is heated to high temperature during long time welding. In such a situation, tip changes in its microstructure and in turn its mechanical properties. This study was intended to investigate those changes by using simulated heat treatment. As a result of this study, it was confirmed that tip of Cu-P alloy hardened with severe cold deformation lose its initial hardness to a large extent within 60 min due to the occurrence of rapid recrystallization while that of Cu-Cr composition hardened by proper aging treatment can preserve its intial hardness for about 1,000 min or longer. Based on these results, suggested was a guideline that can classify contact tips into two different grades: deformation-hardened type and precipitation-hardened type. Following a guideline, a tip with Cu-Cr composition can be classified into the deformation-hardened type if it is in the over-aged condition. Such a guideline is well described.

• 한국생산제조학회지
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• 제21권6호
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• pp.860-864
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• 2012

The contact tip is higher the wear of resistance and the longer life are demanded to GMA welding process. In this study, four different contact tips with three different compositions by two wires were evaluated their wear resistance by measuring in every one hour the area of enlarged hole at the exit side during actual wleding. Experimental results clearly showed that the Cr-containing tips strengthened by precipitation hardening have much better resistance to wear than those made by work hardening. In addition, flux cored wire is excellent abrasion resistance test results showed. Based on these results, the domestic industry, the life of the contact tip to know will be used as basic data.

• 대한기계학회논문집
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• 제10권5호
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• pp.661-669
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• 1986

In this study, the resistance spot welding process of an aluminum alloy was analyzed through the numerical simulation including the electric contact resistance and the heat generation in the electrode. The finite element model was used to solve the electro-thermal responses in weld cycles. The resistance of the contact area was represented as the contact element modeling, but the thermal resistance between the contact surfaces was neglected. Welding tests of Alclad 2024-T3 aluminum alloy were made not only to get the input data for the numerical simulation, but also to compare the numerical results. The contact resistance was determined initially by the contact resistance tests and assumed to decay exponentially up to the solidus temperature. The temperature distributions and dynamic resistance obtained numerically were in good agreement with the experimental results. Numerical results revealed that nugget growth depends mainly on the heat generated in the workpiece and its contact area. The heat generated in the electrode has, however, only a little effect on the nugget growth, and the heat generation in the electrode-workpiece interface is initially high but decrease repidly.

• 한국공작기계학회논문집
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• 제13권5호
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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.