• Journal of Ocean Engineering and Technology
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• v.5 no.1
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• pp.81-87
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• 1991

In this paper, an attempt has been taken for improving the weldability of wer welds of TMCP steel plate by shielding around weld arc surroundings. The principal results of this experimental investigation can be summarized as follows: 1) The cooling rates resulting from wet wlds with the developed electrode on TMCP steel plate could be lower than that of the non-shieled wet welds. 2) The metallurgical characteristics in umderwater wet welds of TMCP steel plate and the developed electrode could be improved by shielding around weld arc surroundings.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.25-26
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• 2005

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore, shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.10a
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• pp.301-306
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• 2003

Spot welding is frequently used for industrial purpose, such as automobile and aerospace industries and household appliances due to its high performance. In these day, robotization and systemization of welding process made it possible to produce more precise or smaller electric parts. And when it comes to welding of steel sheet, the size of nugget must be getting smaller. Therefore, welding conditions are limited to avoid defects, such as deformation, damage, weakening of joining area. In this research, the measurement of the nugget size by the nondestructive inspection has been conducted. As a result, the right estimation of the nugget size and void defects, the detection of corona bond near joining area, the selection of the optimum ultrasonic mode, and set up for ultrasonic inspection are studied. From the trustworthy solutions of nugget size estimated by results of measurement, the optimum inspection conditions depending upon the width of welding parts are determined as well.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.8 s.173
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• pp.17-26
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• 2005

Dissimilar-metal welds(DHWs) are used widely in various industrial applications due to the pratical importance from the technical and economic aspect. However, DMWs have several fabricative and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Recently, DMWs have used the various of heat source to decrease such as faults. In this paper, the weldability on dissimilar metal welds of Austenite stainless steel and Low carbon steel using a continuous wave Nd:YAG laser was experimentally investigated. Experiments were conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.740-745
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• 2006

This study suggested the occurrence source of weld-defects and its solution methods in a welding of Electrolyte injection hole by pulsed Nd:YAG laser. In experiment, the ramp down was used in order that solidification crack was removed. Furthermore. shrinkage stress and heat input were reduced by changing of weld trajectory and defocused distance. As a results of a experiment, a sound weld bead shape and crack-free weld bead can be obtained. In conclusion this show that the welding stability is greatly affected by modulation of laser pulse shape for the same laser energy and welding parameters.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.4
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• pp.370-377
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• 2009

A simple preliminary analysis is often useful to check a validity of design alternatives before the detailed analysis phase in the viewpoint of efficiency. This paper describes a preliminary analysis procedure for the selection among basket design candidates for the spent fuel shipping cask of Korean standard nuclear power plant. As the cask should maintain the structural integrity in hypothetical accident condition, the case of 9 m drop is significantly considered as the worst scenario among the accident conditions in structural design viewpoint in this paper. As basket design options, totally four different types are considered and analyzed in the point of structural integrity at drop impact and weldability for fabrication. As a result, an insertion round plate type with densely spaced supports turns out to be the best in both of the viewpoints, though the weld plate type shows a bit more design margin.

• Journal of Welding and Joining
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• v.5 no.4
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• pp.28-35
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• 1987

The feasibility of underwater wet arc welding process is experimentally investigated by using high titanium oxide type electrodes and TMCP steel plates as base metal. It is assertained the tis process may be put to practical use. Main results are summarized as follows; (1) Sound underwater weld can be obtained by skilled welding operator, if proper welding conditions are selected. (2) In underwater wet arc welding process, the mechanical properties of HAZ are depend upon welding condition and the optimum welding condition can obtained. (3) The maximum hardness in the HAZ of TMCP steel plates is increased significantly in this welding process.

• Journal of Welding and Joining
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• v.12 no.4
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• pp.127-140
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• 1994

Resistance spot welding has been widely used in the sheet metal joining processes because of its high productivity and convenience. In the resistance spot welding processes the size of molten nugget is a criterion to assess weld quality. Many research have founded on measuring weld nugget size at the same time monitoring welding process parameters such as dynamic resistance and electrode movement. With increasing demand of energy saving, many efforts were made to employ aluminum alloys that are lighter than steel and have relatively equivalent strength to steel in the automobile industry. In this paper, spot weldability of aluminum alloys for various welding conditions were examined by series of experiments. One of the 6000 series (Mg-Si) aluminum alloy, 6383-T4 was chosen, which is currently considered as a substitute for the galvanized steel. Dynamic resistance, electrode movement and corresponding nugget size were observed and compared to the case of steel. Finally, resistance spot welding of dissimilar material (galvanized steel-aluminum alloy) was attempted.

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.39-41
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• 2006

The weld quality of spacer grids in Pressurized Water Reactors(PWR) fuel is extremely important for the fuel assembly performance in the nuclear renter. The spacer grid welds are currently evaluated mainly by the metallographic examination although it reveals only cross-points which are welded by the laser beam. This experiment is also to compare the weldability of Zircaloy-4 spacer grids using by the GTA and laser beam. The effect of node geometries of spacer grids for GTAW and LBW has been studied and optimum conditions of spacer grid welding have been found. Microstructures and micro-hardness of GTA and laser beam welded zones have been also compared.

• Proceedings of the KWS Conference
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• 1998.05a
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• pp.150-154
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• 1998

The purpose of this paper is to investigate optimum welding conditions of STS 304 thin sheet by GTA welding and control 6 $\delta$--fenite which is harmful in mechanical processing, corrosion problem and can be formed brittle a phase in using long term at high temperature. One series of automatic welds was made using argon plus 10, 20, 30 % nitrogen to ensure a fully austenite deposit. Results obtained were summarized as follows: 1) 6 $\sigma$ferrite content in the weld metals is influenced largely by the nitrogen content. 2) Additions of nitrogen to the shielding gas can significantly reduce the amount of retained delta ferrite and result in an increase in hot cracking. 3) Bead width was increased when Ar + $N_2$ shielding gas was used and travel speed was increased. 4) Ar+$N_2$ shielding gas made weld metal ductile and reduce 6 -$\delta$-ferrite.