• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.93-94
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• 2006

The repair welding of small leakage parts on the water pipeline in engine room is often and important factor in standby and emergency condition in a ship. So, the purpose of this study is to evaluate the corrosion characteristics of welding part of leakage water pipe in case of some underwater welding electrodes. The corrosion current density between welding metal and base metal was considerably different according to used underwater welding electrodes. In case of DC welding, its corrosion characteristics was better than that of AC welding.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.176-180
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• 2002

During the last two decades the laser beam has progressed from a sophisticated laboratory apparatus to an adaptable and viable industrial tool. Especially, in its welding mode, the laser offers high travel speed, low distortion, and narrow fusion and heat-affected zones (HAZ). The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. Although high-power laser beams have been combined with the plasma from a gas tungsten arc (GTA) torch for use in welding as early as 1980, recent work at the Ohio State University has employed a low power laser beam to initiate, direct, and concentrate a gas tungsten arcs. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process known as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma (LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well focused melted spots.

• Laser Solutions
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• v.5 no.3
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• pp.15-20
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• 2002

The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process blown as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma(LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well-focused melted spots.

• Journal of Welding and Joining
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• v.8 no.3
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• pp.1-12
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• 1990

• Transactions of Materials Processing
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• v.24 no.4
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• pp.256-263
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• 2015

Electric resistance spot welding has been used to join overlapped steel sheets in automotive bodies. Recently to reduce weight in automotive vehicles, non-ferrous metals are being used or considered in car bodies for hoods, trunk lids, doors parts, etc. Various welding processes such as laser welding, self-piercing rivet, friction stir welding are being used. In the current study, a new electric resistance heated friction stir spot welding is suggested for the spot welding of non-ferrous metals. The welding method can be characterized by three uses of heat -- electric resistance heating, friction stir heating and conduction heating of steel electrodes -- for the fusion joining at the interfacial zone between the two sheets. The welding process has variables such as welding current, diameter of the steel electrodes, revolutions per minute (rpm) of the friction stir pin, and the insert depth of the stir pin. In order to obtain the optimal welding variables, which provide the best welding strength, many experiments were conducted. From the experiments, it was found that the welding strength could be reached to the required production value by using an electrode diameter of 10mm, a current of 7.6kA, a stirring speed of 400rpm, and an insert depth of 0.8mm for the electric resistance heated friction stir spot welding of 5052 aluminum 1.5mm sheets.

• Proceedings of the KWS Conference
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• 1997.10a
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• pp.147-150
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• 1997

The characteristics of underwater welding of SWS490 steel were investigated. The bead-on-plate type welding with one or three pass using ilmenite and water-proofed type electrodes was performed by varying welding currents and the sizes of electrodes used. The amounts of hydrogen absorbed inter the weld metal were measured according to the JIS Z 3118 specification and the results were interpreted in terms of the cold cracking behaviours of the welded steel. The microstructural changes as well as the microhardness distribution after underwater welding were also investigated using Vickers microhardness tester and S.E.M (scanning electron microscopy) and O.M (optical microscopy). The results indicated that the cold cracking could be avoided by three pass welding under low current with an electrode with a small diameter.

• Journal of Ocean Engineering and Technology
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• v.27 no.3
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• pp.79-84
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• 2013

The seawater pipes in the engine rooms of ships are surrounded by severely corrosive environments caused by fast flowing seawater containing chloride ions, high conductivity, etc. Therefore, it has been reported that seawater leakage often occurs at a seawater pipe because of local corrosion. In addition, the leakage area is usually welded using shielded metal arc welding with various electrodes. In this study, when seawater pipes were welded with four types of electrodes(E4311, E4301, E4313, and E4316), the difference between the corrosion resistance values in their welding zones was investigated using an electrochemical method. Although the corrosion potential of a weld metal zone welded with the E4316 electrode showed the lowest value compared to the other electrodes, its corrosion resistance exhibited the best value compared to the other electrodes. In addition, a heat affected zone welded with the E4316 electrode also appeared to have the best corrosion resistance among the electrodes. Furthermore, the corrosion resistance of the weld metal zone and heat affected zone exhibited relatively better properties than that of the base metal zone in all of the cases welded with the four types of electrodes. Furthermore, the hardness values of all the weld metal zones were higher than the base metal zone.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.56-61
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• 2000

This study has been performed for mechanical properties of underwater wet welding electrode with rolled steel (KR-RA) for ship structure, one kind (E 4313) of domestic covered arc welding electrode used in the air and two kinds (UWE-01, UWE-02) of underwater covered arc welding electrode experimentally developed on the same welding condition. The results obtained were as follows : The hardness value of underwater covered arc welding electrode (UWE-01) was about 8.3% lower than domestic covered arc welding electrode(E 4313) in heat affected zone of test of UWF-02 was lower about 4.5%. Tensile strengths of UWE-01 were about 0.9%, and those of UWE-02 were about 6.5% higher than those of domestic covered arc welding electrodes (E 4313) in test specimens. The impect value of UWE-01 were about 15.5%, and those of UWE-02 were about 21.7% highter than those of domestic covered arc welding electrodes(E 4313) in test specimens. So mechanical properties of the underwater arc welding electrode were improved by the composition ratios of covering materials.

• Transactions of Materials Processing
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• v.27 no.3
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• pp.145-153
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• 2018

Magnesium material could be widely used in the automotive industry because of its high strength to weight ratio, but the electric resistance spot welding process of magnesium sheets is difficult because of its low electric resistance and high thermal conduction and thermal expansion. For this reason, an electric resistance surface friction spot welding process using rotating dies is suggested for the spot welding of magnesium metal sheets. This welding method can be characterized by three heating methods: (1) electric resistance heating on contacted surface, (2) surface friction heating by rotating dies, and (3) thermal conduction heating from heated steel electrodes, for the fusion of metal at the interfacial zone between the two magnesium sheets. This welding process also has variables to explore, such as welding currents, diameters of the steel electrode, and rotating dies. It was found that the welding strength could reach industrial requirements by applying a welding current of 11.0kA, with steel electrodes of 12mm diameter, with rotating dies of 4.4 mm diameter, under the condition of a revolution speed of 1200rpm of rotating dies, for the surface friction spot welding process of AZ31 magnesium alloy sheets of 1.4mm thickness.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.13-16
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• 2001

High speed seam weldability of tin coated steels was investigated. Welding was performed by the laboratory wire seam welder that was equipped with process monitoring system Test results showed that increase in applied current and pressure reduced the total resistance across the welding electrodes. Lower and upper limits of welding current increased as the sheet thickness increased, while the acceptable welding condition range decreased. However, extremely low electrode pressure produced unstable welding condition range. The results also demonstrated that slower welding speeds widened the optimum welding heat input range.