• Proceedings of the KWS Conference
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• 2009.11a
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• pp.33-33
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• 2009

This study is to develop the resistance welding apparatus and investigate the welding characteristics of Zircaloy-4 end-plate of fuel bundle in the cases of the resistance welding and the laser beam welding. The welding parameters which affect the weld nugget and the torque values have been also compared. The effect of the torque strength of end-plate welding using by the resistance welding and the laser beam welding has been studied and optimum conditions of Zircaloy-4 end-plate welding have been found. Futhermore, micro-structures and micro-hardness of the resistance welded specimens have been also compared.

• Journal of Welding and Joining
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• v.29 no.1
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• pp.115-122
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• 2011

This study is to propose an in-process monitoring system for micro resistance spot welding processes using minute accelerometer. A minute accelerometer is mounted on the upper moving electrode tip holder. With its high sensitivity and frequency response characteristics, accelerometer output signal has been successfully recorded and integrated twice to reflect electrode expansion during micro spot welding processes. The analysis of electrode expansion pattern was attempted to find its correlation with spot weld quality. Major previous findings1-6) regarding spot weld quality assessment with the electrode expansion signal in large scale resistance spot welding processes were proved to be true in this in-process monitoring system.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.622-629
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• 2001

The aim of this experiment is to establish the method that obtains symmetrically two nuggets in microresistance series spot welding. The sheets of austenite stainless steel STS304 applied to various electronic parts were experimented by the inverter welding power source of polarity controllable type and by the twin head for left and right electrode force to be controlled separately. The experimental results were obtained as follows : 1) When series spot welding was carried out by DC 1 pulse as welding current with same electrode force at left and right, the asymmetry of nuggets was resulted from the larger nugget of the (-) pole because of the Peltier effect. The dynamic resistance of weld spot at left and right was appeared differently according to the growth of nuggets. 2) When AC 1 cycle by welding power source of polarity controllable type was applied, the nuggets were almost symmetrically formed. 3) In a twin head, if the electrode force of (-) pole was larger than that of (+) pole, the diameters of two nuggets became to same. It was confirmed that the dynamic resistance of (-) pole was decreased to the same level as it of (+) pole. 4) Although the forces of left and right electrode were same, and only DC 1 pulse was applied, symmetric nuggets were obtained if the conductivity of (+) pole was lower than it of (-) pole.

• Proceedings of the KWS Conference
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• 2003.11a
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• pp.159-161
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• 2003

Electrode movement signal has been widely used in resistance spot welding system This study is to compare accelerometer signal with gap sensor signal in servo gun system. This study propose that accelerometer output signal is a useful technique of quality monitoring in resistance welding processes.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.58-68
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• 2000

When SS400 steel was welded with low hydrogen type and ilmennite type welding, the effect of post-weld heat treatment(PWHT) was investigated with parameters such as micro vickers hardness, corrosion potential, polarization behaviors, galvanic current, Al anode generating current and Al anode weight loss etc. Hardness of each parts(HAZ, BM, WM) by PWHT in case of low hydrogen type and ilmennite type welding was lower than that of each parts by As-welded However hardness of WM area in case of low hydrogen type and ilmennite type welding was the highest among those three parts regardless of PWHT, Whereas in case of ilmennite type welding, WM area was the highest potential among these three parts on galvanic potential series with As-welded while BM area was the highest potential among these three parts by PWHT on the contrary. And in case of low hydrogen type welding, galvanic corrosion and micro cell corrosion of welding parts was decreased with PWHT. However, It was increased with PWHT in case of ilmennite type welding. Moreover Al anode generating current and anode weight loss in case of low hydrogen type was decreased by PWHT compared to As-wedled but, which was increased than that of As-welded in case of ilmennite type welding. Therefore, it is suggested that Corrosion resistance property in case of low hydrogen type welding is increased by PWHT. However its property was devreased with PWHT in case of ilmennite type welding.

• Proceedings of the KWS Conference
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• 2000.10a
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• pp.320-323
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• 2000

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.305-307
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• 2001

• International Journal of Korean Welding Society
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• v.5 no.1
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• pp.53-59
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• 2005

Auto industry has employed resistance spot welding(RSW) to join steel sheets for structural rigidity of automobile body. Driven by the need to reduce weight and fuel consumption, car companies have been evaluating aluminum intensive vehicles(AIVs) as a way to reduce vehicle weight without downsizing. During the transition from all steel-construction vehicle body to aluminum intensive body, joining aluminum to steel sheets emerges as a serious contender in automobile body. This paper deals with application of transition material to RSW aluminum to steel. Placing transition material insert between the aluminum/steel interface was found very effective to overcome physical incompatibility between aluminum and steel. Use of transition insert allows for two separate weld nuggets to be formed in their respective aluminum/aluminum and steel/steel interfaces. This RSW processes was monitored with the aid of dynamic resistance sampling. Typical patterns in sampled dynamic resistance curves indicated formation of sound nugget. The growth of two separate nuggets was examined by micro-cross section test.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.331-337
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• 2010

This study compared the macro and micro electrochemical characteristics at the local area of welding metal on dissimilar welding parts for type 304 stainless steel (SS) and type 316L SS. The materials are used for double wall gas pipe of duel fuel engine for a ship. The various potentiodynamic experiments were performed several times in 10% ${H_2C_2O_2}{\cdot}{H_2O}$ solution using macro and micro methods, respectively. The micro electrochemical experiments conducted to resolve at local area on cross-section of dissimilar welding materials by micro-droplet cell device. The micro-droplet cell techniques can be used almost electrochemical experiments to resolve corrosion characteristics of the limited electrode area of the metallic surface between wetted spot of working electrode and tip of sharpened capillary tube. The results of macro electrochemical experiments show that resistance of active dissolution reaction at welding zone was high due to low current density by formation of passivation protection film at passive region. According to the micro electrochemical experiment, the corrosion current density of welding zone and bond zone were relatively high.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.187-192
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• 2002

Applicability of laser micro welding process to the fabrication of medical devices was investigated. Austenitic stainless steel wire (SUS304) was spot melted and crosswise welded, which is one of the most possible welding process for the fabrication of medical devices, by using a Nd-YAG laser. Effects of welding parameters on the microstructure, tensile strength and corrosion resistance were discussed. In the spot melting, melted metal width decreased with decreasing the input energy and pulse duration. Controlling the laser wave to reduce laser noise which occurred in the early stage of laser irradiation made reasonable welding condition wider in the welding condition of small pulse duration such as 2ms. The microstructure of the melted metal was a cellular dendrite structure and the cell size of the weld metal was about 0.5~3.5 ${\mu}{\textrm}{m}$. Tensile strength increased with the decrease of the melted metal width and reached to a maximum about 660MPa, which is comparable with that for the tempered base metal. Even by immersion test at 318K for 3600ks in quasi biological environment (0.9% NaCl), microstructure of the melted metal and tensile strength hardly changed from those for as melted material. In the crosswise welding, joints morphologies were classified into 3 types by the melting state of lower wire. Fracture load increased with input energy and melted area of lower wire, and reached to a maximum about 80N. However, when input energy was further increased and lower wire was fully melted, fracture load decreased due to the burn out of weld metal.