• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.298-300
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• 2006

• Journal of Welding and Joining
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• 제14권1호
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• pp.82-91
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• 1996

The maximum butt-joint gap size in $CO_2$ laser beam welding of SAPH steel plates with different thicknesses and its bending formability were studied. In the range of the gap size$\geq$0.1mm, the optimal butt welding speed was faster than that of no gap (air gap) condition. This behaviour was independent on the difference of thickness at any combination. Also, the allowable gap size in steel plates with different thicknesses was larger than with same thicknesses. In the range of $T/T_0$(bead shape) $\geq$ 0.8, good bending formability was obtained at any combination of thickness. The formability was improved by reducing the hardness in weld bead using pre-heating process. Finally, FEM result of the laser beam welded underframe with different thicknesses was compared to that of the conventional spot welded underframe.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.511-515
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• 2002

Extruded and cast plates of AZ type magnesium alloys were successfully joined by friction stir welding (FSW). Effect of FSW conditions on the formation of the defect was revealed in relation to tool rotation speed and specimen travel speed. Magnesium alloy with higher aluminum content became difficult to be joined and the optimum condition without defect was restricted into narrow condition range. The structure of the stirred zone was a fine-grained recrystallized structure even in the case of cast AZ91D. FSW joint had better mechanical properties than those of GTA welded joint. Especially the toughness of the stirred zone increased more than that of the base metal.

• Journal of Welding and Joining
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• 제16권5호
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• pp.48-55
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• 1998

This study was undertaken to investigate the friction welding of A2024-T6 aluminum alloy and SM45C carbon steel using insert metals. The relationships among the friction welding conditions, the tensile strength of joints, the hardness distribution of welds, the microstructure of welds and the tensile fracture surfaces were mainly investigated through this experiment. When the A6063-T5 aluminum alloy of insert metal was used, the maximum tensile strengh of joint was obtained. In this case, the maximum joint efficiency was 75.3 percent and in the case of unusing the insert metals, it was 37.7 percent. Optimal welding conditions were N=2000rpm, P$_1$=40MPa, P$_2$=140MPa, t$_1$=1.0sec and t$_2$=5sec.

• 한국레이저가공학회지
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• 제11권3호
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• pp.16-20
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• 2008

The lap Joint welding of 6K21 aluminum sheets by Nd:YAG laser were performed with an aluminum 5183 filler wire or without a filler wire. The porosity of laser welding beads were observed through an optical microscope and X-ray photography with various levels of welding speed and gap size. The porosity was observed in the gap between upper and lower sheet near a heat affected zone when autogenous welding. Decrease of welding speed and use of AA5183 filler wire reduced porosity significantly.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.96-96
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• 2010

Magnesium alloy is being used for structural material since it has high specific strength. Tubular shape was effective way for enhanced structural design. To manufacture the tube, it is necessary to weld the butted joint of both tubular formed sides. But the magnesium alloy was hardly welded with conventional welding processes. The laser welding was effective way to joint magnesium alloys because it had high weld strength and productivity compare with other welding processes. In this study, magnesium alloy sheets was formed at elevated temperature to tubular shape and welded with laser. Consequently, the magnesium alloy tube was making successful with warm forming and laser welding and bicycle frame was making with it.

• Journal of Welding and Joining
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• 제19권3호
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• pp.317-324
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• 2001

This study deals with high power Nd:YAG laser welding of thin steels for small pressure vessels. Full penetration welding at the overlap joint was performed so as to assure sufficient weld strength. Results showed that mid-depth weld size reduced drastically with increasing the travel speed. Position of focus had little effect on the bead formation even though short focal system was used. However, the shape factor and the bead width had closely related with the position of focus. Based on the microstructural inspection, acceptable weld was obtained when the overlap clearance was controlled up to 20% of the base metal thickness. In the case that the joint contained more clearance than the critical value, both the tensile shear strength and the tear strength were reduced. Results also demonstrated that shielding gases were proved to play a key role as far as the bead formation characteristics was taken into consideration. Blowing dry air through 5mm in diameter nozzle produced narrower bead cross-section than that of argon or nitrogen shielding.

• 한국디지털건축인테리어학회논문집
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• 제8권1호
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• pp.57-64
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• 2008

There are many problems in present truss-deck slab system for example welding defect, segregation, water leakage, rust and tarnish etc. These problems may be caused by spot welding thin galvanized steel plate and lattice bar. The TOX Joining Systems is to join metal sheets of different material and thickness with and without coating or painting without adding heat or a joining part. Newly developed TOX-deck slab system using non-welding joint is free from above mentioned problems. The objects of this study are suggestion of design strength of TOX joint by experimental and statistical analyses and development of window based program to design the TOX-deck slab system.

• 대한기계학회논문집
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• 제7권3호
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• pp.263-269
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• 1983

Underwater welding by a gravity arc welding process was investigated by using six types of coated electrodes and SM41A steel plates of 10 mm thickness as base metal and it was ascertained that this process may be put to practical use. Main results obtained are summarized as follows: 1. Angle of electrode affects no influence on bead appearance and the proper range of welding current and diameter of electrode for the high titanium oxide type is relatively wider than that for the ilmenite type. And the lime titania type, high titanium oxide type and ilmenite type of domestic coated arc welding electrodes of .phi.4 mm could attain the soundest underwater welded joints which contain no welding imperfection. 2. According to macro-structure, micro-structure and hardness distribution inspectionson underwater welded joint, the area between the HAZ and the surface of the weld in neighbourhood of the bond has the maximum hardness value. The structure of these parts is martensite and bainite. Other parts contain mocro-ferrite, micro-pearlite structure, which contain soundness of welded joint free from weld imperfection. 3. On consideration of both tensile strength of more than 100% joint efficiency and sufficient impact value, the welding condition which can get optimal welding strength is heat input of 1,400-1,500 J/mm, current of 200-215 ampere (voltage of 32-33 volts) in the case of lime titania type electrode. 4. Underwater welding strength (tensile strength, impact strength) depends on heat input (or current) quantitatively and they have the relationship of parabolic function. Each experimental equation has a high reliability and its percent of mean error is 4.14%. 5. It is suggested that the optimal design of weld strength by welding condition (current, heat input) could be utilized for a quality control of underwater welding.

• Steel and Composite Structures
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• 제4권5호
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• pp.355-365
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• 2004

A new reduction method of residual stress in welding joint is proposed where welded metals are shaken during welding. By an experiment using a small shaker, it can be shown that tensile residual stress near the bead is significantly reduced. Since tensile residual stress on the surface degrades fatigue strength for cumulative damage, the proposed method is effective to reduction of residual stress of welded joints. The effectiveness of the proposed method is demonstrated by the response analysis using one mass model with nonlinear springs.