• Journal of Welding and Joining
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• v.22 no.5
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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.

• International Journal of Precision Engineering and Manufacturing
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• v.7 no.3
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• pp.30-34
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• 2006

We investigated fatigue crack growth behavior in laser-welded sheet metal caused by a single applied overload The fatigue specimens were made using butt jointed cold rolled sheet metal that was welded with a $CO_2$ laser, The effects of the specimen thickness and overload ratio were determined from fatigue crack propagation tests, These tests were performed in such a way that the fatigue loading was aligned parallel to the weld line while the crack propagated perpendicular to the weld line, Overload ratios of 1.0, 1.5, and 2. 0 were applied near the tip of the fatigue crack at points located 6, 4, and 2 mm from the weld line. The specimens were either 0.9 or 2.0 mm thick. The size of the plastic zone at the crack tip due to the single applied overload was also determined using finite element analysis.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.263-265
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• 2003

The transverse crack, a type of cold crack, occurs perpendicular to the axis of the weld interface, longitudinal residual stresses ($\sigma$k direction) are more important in transverse crack occurrence from my own experience. Specimens were fabricated and welded under actual construction conditions, and then residual stresses of longitudinal stresses were measured for different welding conditions with SAW and FCAW process. The residual stress values for the specimen welded Interpass temperature below 30$^{\circ}C$ was higher than the specimen welded interpass temperature of 100～120$^{\circ}C$. And also the residual stress values for a specimen measured at weld surface, as welded condition, was higher than that of longitudinal residual stresses that was measured from a small test piece, due to the residual stress was relieved in the process of the cutting and machining. Transverse weld cracks were detected in the area of the maximum residual stresses both SAW and FCAW process.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.199-202
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• 2007

The center floor is a part of underbody of cars. The assembling method is mostly a resistant spot welding. But the resistant spot welding has many demerits in productivity such as low welding speed, large spatter occurring, hard to verify the welding quality. The laser welding has many merits such as high welding speed, high static and dynamic weld strength. So the laser welding has been studied to substituted the resistant spot welding. Therefore, in this study, as a pre-evaluation stage for replacing the resistance spot welding with laser in production of automobile parts, the weldability of cold rolled and zinc coated steel sheets is studied and also evaluated the weld strength by the tensile shear test. And the shape of weld bead appearances and micro structure of the weld bead section is also evaluated.

• Journal of Welding and Joining
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• v.10 no.1
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• pp.52-59
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• 1992

Resistance spot weldability of cold rolled 80kg/mm$^{2}$ and 45kg/mm$^{2}$ grade high strength steel sheets for automobile structure was investigated focussing on the influences of welding parameters such as welding current and welding time on the weld strength and the nugget formation. The results of this study showed that the optimum ranges of welding current for the grade 80 and grade 45 were 5.0 cycle(250 m sec.) It was also shown that the tensile shear strength of the resistance spot weld was strongly influenced by both current and time applied in welding procedure, however, the tensile shear strength was mainly affected by welding time for the higher strength steel.

• 한국기계연구소 소보
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• s.9
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• pp.75-82
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• 1982

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.251-253
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• 2006

• Proceedings of the KWS Conference
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• 2006.05a
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• pp.257-259
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• 2006

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.109-112
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• 2007

• Proceedings of the KWS Conference
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• 1992.10a
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• pp.196-198
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• 1992