• Journal of Welding and Joining
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• v.28 no.4
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• pp.73-80
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• 2010

In this work, the effect of welding variables on weldability of gas tungsten arc(GTA) welding was investigated with experimental analysis for a commercial pure(CP) titanium (Grade.1). The GTA welding tests on sheet samples with 0.5mm in thick were carried out at different process variables such as arc length, welding speed and electrode shape. In order to search an optimum arc length with full penetration, bead- on-plate welding before butt-welding were performed with different arc length conditions. From the bead- on-plate welding results, the optimum condition considering arc stability and electrode loss was obtained in the arc length of 0.8mm. Butt-welding tests based on the arc length of 0.8mm were carried out to achieve the optimum conditions of welding speed and electrode shape. Optimum conditions of welding speed and electrode shape were suggested as 10 mm/s and truncated electrode shape, respectively. It was successfully validated by the microstructural observation, tensile tests, micro-hardness tests and formability tests.

• Journal of Welding and Joining
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• v.17 no.4
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• pp.32-38
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• 1999

PAL(Pohang Accelerator Laboratory) designed and manufactured a 5m-long straight vacuum chamber to adopt U7 undulator that is the first insertion device. Top and bottom plates of the vacuum chamber were made of Al alloy A5083-H321, and welded together by the GTAW welding. The leak rate is less than 1×{TEX}$10^{-10}${/TEX} torr·ℓ/s with negligible welding deformation. The pressure has been maintained below {TEX}$10^{-10}${/TEX} torr after installation. This paper reports the welding process and the method applied to achieve ultimate vacuum performance and t satisfy integrity of welds.

• Journal of Power System Engineering
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• v.15 no.6
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• pp.73-80
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• 2011

The experimental investigation focuses on an influence of artificial aging time in longitudinal butt welded Al 6013-T4 aluminum alloy on the fatigue crack growth resistance. The preferred welding processes for this alloy are frequently tungsten inert gas welding (TIG) process due to its comparatively easier applicability and better weldability than other gas metal arc welding. Fatigue crack growth tests were carried out on compact tension specimens (CT) in longitudinal butt TIG welded after T82 heat treatment was varied in three artificial aging times of 6 hours, 18 hours and 24 hours. Of the three artificial aging times, 24 hours of artificial aging time are offering better resistance against the growing fatigue cracks. The superior fatigue crack growth resistance preferred spatial variation of materials within each specimen in the Paris equation based on reliability theory and fatigue crack growth rate by crack length are found to be the reasons for superior fatigue resistance of 24 hours of artificial aging time was compared to other joints. The highest of crack propagation resistance occurs in artificial aging times of 24 hours due to the increase in grain size (fine grained microstructures).

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.1
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• pp.29-34
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• 2013

The welds tent to be weakened if it is exposed to the air during the welding process. In titanium welding with Gas Tungsten Arc Welding, inappropriate colors of the welds, such as purple/red, blue, yellow, gray, white and pink represents that it is contaminated by oxygen and nitrogen in the air. Shielding gases can be used to protect welds from the contamination. In addition, Weld metal and heat affected zone (HAZ) are also shielded from the air when it is cooled down to the room temperature. In this paper, appropriate shielding gases for the shape and form of Trailing Shielding Jig and torch shielding ($13{\sim}20{\ell}/min$), after shielding ($22{\sim}30{\ell}/min$), and back shielding ($25{\sim}30{\ell}/min$) are studied.

• Korean Journal of Materials Research
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• v.13 no.12
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• pp.850-854
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• 2003

The abrasion wear behavior on the hardfacing weld was investigated by performing abrasion wear, hardness, and microstructural tests. The gas metal arc(GMA) weld was produced by using the cored wire which was filled with the hard metal, i.e., the recycled tungsten carbide (WC) reinforced metal matrix composite. For 30% addition of the hard metal, the abrasion wear resistance was significantly improved comparing with that for 20% addition of the hard metal. Above 30% addition of the hard metal, however, there was no significant improvement of the wear resistance. The improvement of the wear resistance was due to the increased amount of eutectic carbides(W$_{6}$C) which was formed during GMA welding. For the weld in which the hard metal was added to 30-40%, an optimum level of abrasion wear resistance was performed.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.115-121
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• 2014

Alloy 617 is the one of the leading candidate materials for intermediate heat exchangers(IHX) of a very high temperature reactor(VHTR) system. Some of the components are joined by many welding techniques and therefore the welded joints are inevitable in the construction of systems. In the present paper, the low cycle fatigue(LCF) behaviors of Alloy 617 base metal(BM) and the gas tungsten arc welded (GTAWed) weld joints(WJ) are investigated experimentally under strain controlled LCF tests. Fully axial total-strain controlled tests have been conducted at room temperature with total strain ranges of 0.6, 0.9, 1.2 and 1.5%. The weld joints have shown a lower fatigue lives compared with base metals at all the testing conditions. The weld joints have shown a higher cyclic stress response behavior than base metal. Both BM and WJ exhibited cyclic strain hardening behavior, depending on the total strain range. In addition, the strain-life parameters for BM and WJ were determined, based on Coffin-Manson equations.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1120-1125
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• 2004

Welding characteristics of STS304 stainless steel and Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. Alloy 600 being used in steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion environment, stress corrosion cracking can occur on this material. Presented here are the results from a series of experiments in which dissimilar metal welds were made using the gas tungsten arc welding process with pure argon shielding gas. But It is well known that solidification cracking susceptibility of austenitic alloys depends on the solidification temperature range and amount/distribution of solute rich liquid that exists at the terminal stages of solidification. An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent welding zone formation at dissimilar metal welds.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.131-138
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• 2010

Recently, extruded aluminium-alloy panels have been used in the car bodies in order to meet the needs for the speed-up and light-weight of the railway vehicles. Most of the car bodies were jointed by arc weldings, like GMAW (GasMetal Arc Welding) and GTAW (Gas Tungsten Arc Welding), but these weldings became fairly worse the mechanical properties of the junction than the base metal. Nowadays, FSW (Friction Stir Welding), which is superior to the arc weldings, has been applied in the railway vehicles. In this study, the mechanical properties of the joints in both FSW and GMAW for A6005 extruded aluminium-alloy sheets have discussed. In addition, the relationships between the welding conditions and the mechanical properties for the joint of FSW have analyzed through the sensitivity analysis. It can be concluded that the mechanical properties for the joint of FSW are better than those of GMAW and the welding speed is the most sensible welding condition in the process of FSW.

• Journal of the Korean Society for Railway
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• v.12 no.4
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• pp.512-517
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• 2009

Extruded aluminium panels have been widely used for railway vehicle structures because -of their light specific weight and other merits. In the past, GMAW (Gas Metal Arc Welding) and GTAW (Gas Tungsten Arc Welding) were mainly used to join aluminium panels. But recently friction stir welding (FSW) is widely used due to its lots of advantage. In this study aluminium A6005 which is used for car body structures was chosen. The influences of main parameters on mechanical properties such as: pin (tool) rotating speed, pin transition speed, shoulder, diameter, pin length and tilting angle were examined. Optical microscope and scanning electron microscope (SEM) observation, micro hardness tests, and tensile tests were carried out.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.670-677
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• 2003

Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in heavy wall pipe welding. Generally Narrow-gap TIG welding is used as orbital welding process, it is important to select the optimum conditions for the automatic control welding This paper looks at the application and metallurgical properties on Narrow-gap TIG welding joint of heavy wall large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness. The fracture toughness depends slightly on the welding heat input.