• Proceedings of the KWS Conference
• /
• 2000.10a
• /
• pp.281-283
• /
• 2000

• Proceedings of the KWS Conference
• /
• 2006.05a
• /
• pp.27-29
• /
• 2006

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.7 no.3
• /
• pp.263-269
• /
• 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.

• Journal of Power System Engineering
• /
• v.15 no.3
• /
• pp.58-64
• /
• 2011

As well known, the friction stir welding is a novel welding process which is a solid state welding process for sheet or plate using the friction stir phenomenon. This paper describes the effect of welding condition such as the rotation speed and the travelling speed during the friction stir welding process on the micro Virkers hardness and the microstructure of friction stir welded joints in AI-7075-T651 plate. From those investigations, the highest hardness of stir zone was observed at the welding condition of SO-3. The microstructures of the friction stir welded joints was not dependent on the welding conditions, but in the SO-4 specimen, the friction stir welding defect like tunnel shape was found in stir zone.

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

• Proceedings of the KWS Conference
• /
• 2006.10a
• /
• pp.158-160
• /
• 2006

Super alloys are typically used for the liquid thruster in the aerospace industry. In this work, The bead-on-plate welding of Inconel 600, Inconel 625 and Haynes 230 using Nd:YAG laser are studied, in order to examine the effects of experimental parameters on their weldability. The micro-hardness and tensile strength of the specimens are also analyzed, to obtain the optimal welding conditions.

• Journal of Welding and Joining
• /
• v.23 no.6
• /
• pp.43-48
• /
• 2005

This work was carried out to obtain sound welds and to select a most suitable binary metal joint among three different dissimilar binary metal combinations such as Zr-4/Ta, Mo/Ta and Ti/Ta(seal tube/sensor sheath) joints fur the instrumented nuclear fuel irradiation test. To do this, Taguchi experimental method was employed to optimize the experimental data. In addition, metallography, micro-focus x-ray radiography and hardness test were conducted to examine the welds. From the weld bead appearance, penetration depth and bead width as well as weld defects standpoint, Zr-4/Ta joint is suggested for the circumferential joining between a seal tube and a sensor sheath. The optimized welding parameters based on Zr-4/Ta joint are suggested as well.

• Journal of Advanced Marine Engineering and Technology
• /
• v.33 no.1
• /
• pp.104-111
• /
• 2009

This paper shows the behaviors of macro- and micro-structures and mechanical properties for specimen's welding region welded by FSW. according to welding conditions with 5mm thickness aluminum 5083O alloy plate. It apparently results in defect-free weld zone in case traverse speed was changed to 32 mm/min under conditions of anti-clockwise direction and tool rotation speed such as 800 and 1250 rpm with tool's pin diameter of 5 ${\Phi}mm$ and shoulder diameter of 20 ${\Phi}mm$, pin length of 4.5 mm and tilting angle of $2^{\circ}$. The ultimate stress of ${\sigma}_T=331$ MPa and the yield point of 147 MPa are obtained at the condition of the travel speed of 32 mm/min with the tool rotation speed of 1250 rpm. There is neither voids nor cracks on bended surface of $180^{\circ}$ after bending test. The improvement of toughness after impact test was found. The lower rotating and traverse speed became, the higher were yield point, maximum stress and elongation(%) with the stresses and the elongation(%) versus the traverse speed diagram. Vickers hardness for cross section of welding zone were also presented. The typical macro-structures such as dynamically recrystallized zone, thermo-mechanically affected zone and heat affected zone and the micro-structures of the transverse cross-section were also showed. However, the author found out that the region of 6mm far away from shoulder circumference was affected by friction heat comprehensively, that is, hardness softened and that part of micro-structures were re-solid-solution or recrystallized, the author also knew that there is no mechanically deformation on heat affected zone but there are the flow of plastic deformation of $45^{\circ}$ direction on thermo-mechanically affected zone and the segregation of Al-Mg on nugget. The solid solution wt(%) of parent material as compared against of friction stir welded zone was comprehensively changed.

• Transactions of Materials Processing
• /
• v.8 no.1
• /
• pp.57-64
• /
• 1999

The press formability analysis of welding parts was studied in the current work by the tailor welded blank. As the body panel is used in the press forming of welding parts by a weld method of the tailor welded blank, the following conditions are demanded: 1) The strength of welding parts must be the higher than base metals. 2) After the welding, severe welding deformatins must be avoided. 3) The press formability of welding parts is similar to that of many base metals. 4) The productibility of a welding has to be higher. There are many welding methods satisfying these conditions, but the purpose of this study is to inbestigate the upset weldability and formability of the material (SPCC). SPCC steel sheet showed good weldability and formability under some welding conditions. The experimental results were discussed by the evaluation of the results obtained from tensile tests, hardness tests, micro-structures and Erichsen cup test was a little lower than that of parent material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.10a
• /
• pp.207-210
• /
• 2003

The purpose of this work is to find an appropriate welding approach for rotor assembly of a marine turbocharger. The friction welding and laser welding of dissimilar materials, IN713LC and SCM440 were investigated. The quality of the welded joints obtained from two welding processes was evaluated by microstructure observation, micro-hardness and tensile tests. The friction welded joint indicated a good bonding structure in the weld interface. On the other hand, the laser welded joint showed the weld defects and non-welded area in the weld interface.