• Proceedings of the KSR Conference
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• 2001.10a
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• pp.488-493
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• 2001

CWR technology is generally believed to contribute to the increase of train speed and bring a variety of significant advantages, such as the decrease in track works, noise and vibration as well as the improvement of passenger comfort. In CWR technology, welding is considered to be one of the most important element technologies. Among the various welding methods, thermit welding is the most frequently used one for site welding since the operation is simple and the instruments are light as well as easy to deal with. However, it could cause interference with safety operation of trains since thermit welding points, are essentially made of castings and there are potentialities of defects according to the operation conditions, the environment of the site as well as the dexterity of the worker. This study tries to describe the characteristics of thermit welding, defect-causing factors and defect-detection methods at welding points.

• Journal of Welding and Joining
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• v.19 no.6
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• pp.630-635
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• 2001

The characteristics of spatter generation in the short circuit transfer region of $CO_2$ welding was investigated. Spatteriing phenomena could be classified into three types : Type I generated due to the abrupt increase of arc voltage in arcing duration. Type II by the gas ejection from molten metal and Type III generated by the arc instability at the moment of arc re-ignition just after short circuiting. Main observed types were dependent on the chemical composition of welding wires. The case of YCW12 wires was mainly composed of spatters generated by Type l and Type II, while most, spatters in YCW11 wires were generated by Type II and Type III.

• 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.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.53-56
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• 2007

Magnesium sheet used in electrical device due to mobility and EMF shielding characteristics. Magnesium case by press forming was advantageous compare with conventional die casting process, because of its thin gauge of wall and surface quality. But it need to makes the boss to fix inner part or assemble the case. CD stud welding was effective way for joining the boss to the thin gauge case of the electrical devices. In this study, we investigated the performances of the magnesium boss welder To measure the process parameters such as the force and the weld current, we design the monitoring system for CD stud welding. We test the characteristics of CD stud welding for AZ31 sheets at some variables. Finally we select the optimum welding range of magnesium sheets in CD stud welding process.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.775-780
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• 2004

CWR technology is generally believed to contribute to the increase of train speed and bring a variety of significant advantages, such as the decrease in track works, noise and vibration as well as the improvement of passenger comfort. In CWR technology, welding is considered to be one of the most important element technologies. Among the various welding methods, gas pressure welding is the most frequently used in vicinity of train line station since the operation is simple and the instruments are not heavy. The gas pressure welding is constructed exactly by good manual book on which simple and excellent welding methods is written and has the same performance as raw material. But this can be poor in the variety of the processing of rail end surface to be welded, the control of oxyacetylene flame and axil compressive force. This study tries to describe the characteristics of gas pressure welding, defect-causing factors and preventive counterplan of defects

• Journal of Welding and Joining
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• v.28 no.3
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• pp.36-41
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• 2010

High Mn steel has been developed for automotive applications since the steel has an excellent combination of strength and ductility. However, from the viewpoint of welding, high Mn steel has a few problems related to its chemical composition. This paper describes characteristics of dissimilar $CO_2$ laser welding for expanding application of high Mn steel. From this work it was cleared that dissimilar laser welded joint between high Mn steel and carbon steel had poor formability due to the formation of martensite within weld metal. In order to improve ductility of welded joint, the method of controlling the dilution ratio of high Mn steel was suggested.

• Journal of Welding and Joining
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• v.33 no.2
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• pp.32-39
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• 2015

This study examined the welding residual stress and fracture toughness of 78mm thick steel electro gas welding (EGW) and flux cored arc welding (FCAW) welded joints by numerical analyses of the thermal elasto-plastic behavior and fracture toughness(KIC). The residual stress, fracture toughness characteristics and production mechanism on the welded joints were clarified. Moreover, the effects of the welding process (EGW and FCAW) on the welding residual stresses and fracture toughness of welded joints were evaluated. The results showed that the new welding process (EGW) appears to be an effective substitute for the existing welding process (FCAW) in a thick steel plate with high strength.

• Journal of Welding and Joining
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• v.22 no.6
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• pp.30-35
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• 2004

Laser welding is obviously an attractive method to join small, thin parts such as small stainless steel tubes, but it is very sensitive to the joint clearance and tolerance, and this makes laser welding difficult to obtain consistent welding qualities over time. Recently, Plasma Augmented Laser Welding(PALW) is being developed to solve these problems. In this study, plasma arc welding(PAW) was introduced to join conventional V-grooved butt joint of thin stainless steel strips using single laser heat source in manufacturing small stainless steel tubes. The effect of the welding speed enhancement is investigated by the experiments. Effects of welding directions, distance between the heat sources and intensity of arc heat source on the optimal welding speed was investigated. Through this research, it was confirmed that PALW process has higher welding speed and robustness than laser welding process.

• Journal of Welding and Joining
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• v.35 no.3
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• pp.75-81
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• 2017

Recently in the welding field, the establishment of unmanned and automated systems are rapidly developing. Accurate interpretation of the welding phenomenon is applied a number of monitoring systems. In this paper, butt welding (6t) type I using Plasma-MIG welding was carried out. And we evaluated characteristics of the Al-5083 aluminium alloy in Plasma-MIG hybrid welding. Process variables including the plasma current, MIG voltage, wire feeding rate and the welding speed were used. Butt welding was conducted 1 pass. Argon gas was used as the protective gas that results from the experiment were able to achieve full penetration. In addition to monitoring the welding process occurring during MIG welding current, welding votage and Plasma current, voltage were collected in real time, the photodiode and CCD cameras observing the phenomenon that the welding is in progress were measured using a quantity of light.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.68-74
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• 2016

The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration, and has increased the automation and flexibility of an entire industry. Laser welding of dissimilar metals has been widely used to improve the wear resistance and corrosion resistance of industrial parts. The objective of this research is to investigate the influence of process parameters on the welding of SM45C and STS304 with CW Nd:YAG lasers. Bead-on-plate welding tests were carried out for several combinations of the experimental conditions. In order to quantitatively examine the characteristics of the dissimilar welding, the welding quality of the cut section, strain-stress behavior, and hardness of the welded part were investigated.