• 소성∙가공
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• 제22권4호
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• pp.189-195
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• 2013

In this study, the weld strength of extru-rivet spot welding was investigated by simulation and experiment. In order to obtain hot plasticity flow bonding of the two plates by a single rivet, electrodes are used for heating of the two plates and the rivet by electric resistance. Because weld strength is influenced by the temperature in the weld zone, the diameter of the electrodes and the amount of current supplied to the electrodes are important variables. For the simulation, heat distribution and weld strength were calculated using DEFORM-3D. The weld strength in the weld zone was calculated for various values of the experimental parameters. The simulation results showed that the weld strength was the highest when the weld current was 37kA, the electrode diameter was 12mm, and the welding frequency was 90cycle. Aluminum 5052 was used for the experimental study. A total of three aluminum plates, two welding plates with 1mm thickness and one plate with 2mm thickness for the inserting rivet, were used for the experimental extru-rivet spot welding.

• Journal of Welding and Joining
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• 제19권3호
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• pp.267-273
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• 2001

In this study, welding phenomena involved in formation of penetrators during high frequency electric resistance welding were investigated. High speed cinematography of the process revealer that a molten bridge between neighboring skelp edges forms at apex point and travels along narrow gap toward to welding point at a speed ranging from 100 to 400 m/min. The bridge while moving along the narrow gap swept away oxide containing molten metal from the gap, providing oxide-free surface for a forge-welding at upsetting stand frequency of the budge formation, travel distance and speed of the bridge were affected by the heat input rate into strip. The travel distance and its standard deviation were found to have a strong relationship with the weld defect density. Based on the observation, a new mechanism of the penetrator formation during HF ERW process is proposed.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.13-14
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• 1996

High Frequency Electric Resistance Welding process has been widely used in manufacturing welded steel pipes because of its high welding speed and quality. This process utilizes the skin effect as well as the proximity effect of the high frequency current in heating the skelp edge. In this study, an analytical solution of the edge temperature was obtained based on several assumptions. The assumptions includes the expontial decay of weldingcurrent from the surface and neglect of the heat loss in the welding direction. This calculation shows a good agreement with the observations made from the high speed camera. Using tile analytical model, tile heat required as a function of the welding speed and the skelp thickness was determined. These results were compared with the experimental results obtained.

• Journal of Welding and Joining
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• 제22권5호
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• pp.58-64
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• 2004

Although leakage at a low carbon steel pipe made by electrical resistance welding (ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. In order to clarify the main cause, failure analysis on the leaked pipe was carried out, followed by metallographic investigation and corrosion test for the various ERW pipe made with different welding heat input. The microstructure, particularly inclusion content, of the weldment is dependant on the welding heat input applied. For an improper low heat input, the amount of inclusion at the weld was high. High inclusion content accelerated grooving corrosion at the weld. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion resistance of the ERW pipe.

• Journal of Welding and Joining
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• 제30권2호
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• pp.76-80
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• 2012

In this study, the effect of the welding current on the hardness characteristics and microstructure in the resistance spot welding of 1GPa grade cold-rolled DP steel was investigated, Also, correlation between the hardness and microstructure was discussed. In spite of the change in the welding current, the hardness distributions near weld was similar. the hardness in the HAZ and the fusion zone was higher than that of the base metal and the hardness in the fusion zone was variated with the location. Especially, the hardness of HAZ adjacent to the base metal showed maximum value, and softening zone in the base metal adjacent to HAZ was found. With the increasing of welding current, there were no difference in maximum hardness and average hardness in the fusion zone were, but the hardness of the softening zone reduced. The difference in the hardness in each location of weld due to grain size of prior austenite. The softening of the base metal occurred by tempering of the martensite.

• Journal of Welding and Joining
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• 제29권6호
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• pp.26-32
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• 2011

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1996년도 특별강연 및 춘계학술발표 개요집
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• pp.94-95
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• 1996

• Journal of Welding and Joining
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• 제29권5호
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• pp.99-105
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• 2011

In this study, effect of Si content on nugget diameter in electric resistance spot welded dual-phase(DP) steel was investigated. The cold rolled DP steels with different Si content (0.5, 1.0, 1.5, 2.0 wt.%) were used and thickness of those sheet was 1.2mm. With increasing Si content, nugget diameter was increased at the same welding current. This is attributed to increase of heat input result from high resistivity. Also, nugget diameter was increased with an increase in Si content for the same heat input. For this reason, the melting point of DP steel is lowered with an increase in the Si content. And solid DP steel can easily be transformed to a liquid phase because the low melting point. Finally, a prediction formula for the nugget diameter(N.D.) could be obtained in terms of heat input(Q) and melting point(M.P) as follows: N.D.(mm) = 0.11Q(J) - 0.0031 M.P.($^{\circ}C$) + 0.32.

• 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.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1997년도 특별강연 및 춘계학술발표 개요집
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• pp.151-153
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• 1997