• Proceedings of the KWS Conference
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• 2006.10a
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• pp.123-124
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• 2006

This study aimed at exploiting low heat input characteristic of laser welding to effectively control grain coarsening in the fusion zone(FZ) and heat affected zone(HAZ) of 1.5mm thick 18wt% Cr ferritic stainless steel weld. The study demonstrated that as compared with gas tungsten arc welding(GTAW), laser welding brought about significant grain refinement in the FZ and HAZ. However, the impact absorbed energy of GTA weld was superior than that of laser weld because the strengthening effect during welding and cooling stage was higher In laser weld than that in GTA weld. The coarser grains in each weld than base metal resulted in an inferior toughness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.119-124
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• 2001

Currently knowledge of strain in welds has mainly been obtained form strain gaging method:; that is directly attaching most of the material to the gate. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemisry, food instrument and electronic appliances.

• Journal of Advanced Marine Engineering and Technology
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• v.18 no.3
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• pp.68-77
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• 1994

TIG welding process is applied for the active metal such as aluminum and titanium, also sometimes for overlay welding of superalloy. However the welding speed to be applied is very low because of the unstable bead formed in the region of high current and high welding speed. The present study was carried out to examine the basic phenomena of high speed TIG melt run welding by the 2% Th - W electrode(dia.3.2mm) of various tip shapes.

• 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.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.155-161
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• 2001

Currently knowledge of strain in welds has mainly been obtained from strain gaging method; that is directly attaching most of the material to the gage. The very few non-contact method are still in the early stage. One of the non-contact methods is by the use of the laser that has high-level of the accuracy for the measurement, and this laser also has excellent characteristics on which many studies for its applications are focused throughout the many fields. The dissertation is on the measurement of the strain caused by the characteristics and the temperature changes of the TIG welded zone which is used with 3D ESPI system that is functionally modified through the laser ESPI system. This system employed the aluminum sheet-metal which are mainly used for the steel plate such as for the electronics, chemistry, food instrument and electronic appliances.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.3
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• pp.31-39
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• 1996

The objective of this study is to investigate the influence of welding residual stresses on the fatigue crack growth behavior of cracks located transverse to the weld bead. For this purpose, G. T. A (Gas Tungsten Arc) welding was performed on hte Al alloy 1100-O plate and the same initial crack is made on HAZ(Heat Affected Zone), weld metal and base meta respectively. Specimens were used CT(Compact Tension) specimens. Initial welding residual stresses were measured by using strai gage sectioning method. All specimens were tested under constant amplitude load with stress ratio R=0.1, It is possible to predict fatigue crack growth behaviors and the fatigue life, using numerical analysis together with distribution of initial residual stress and the values of C and m obtained from $da/dN-{\Delta}K$

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.176-178
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• 2004

Gas tungsten arc welds on Al-4 wt% Cu alloys were investigated to determine effects of gravitational orientation on the weld solidification behavior. Outward convection flows in the parallel-down weld might be inhibited because of its reverse direction with respect to the gravity vector. This resulted in abnormal 'S' shape of the trailing s-1 interface and the solidification rate (Vs), which was receded toward the weld pool center. Significant influence of gravitational orientation resulted in the variation on the weld pool shape associated with convection flows, which in turn affected solidification orientation/morphology and the primary dendrite spacing(λ$_1$).

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.55-55
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• 2010

마그네슘 판재는 경량화 소재로 주목받는 소재이다. 본 연구는 압연 마그네슘 판재의 용접시 발생하는 온도이력 및 응력에 대한 해석을 수행하였다. 해석은 2차원 해석을 수행하였으며 해석수행에 있어서 열물성값은 기존의 데이터를 이용하였으며 응력해석은 온도별 고온 인장시험을 수행한 결과를 이용하여 해석을 수행하였다. 본 연구에서 수행한 대상은 마그네슘 압연판재인 AZ31B 이며 두께 3.5 mm 판재를 GTAW용접을 수행한 경우에 대하여 검토하였으며, 해석결과 중 온도분포의 한 예를 그림 1에 나타낸다.

• 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.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.99-99
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• 2009

마그네슘은 지구상에서 존재하는 금속 중 가장 가벼운 실용화 금속이다. 따라서 최근 산업 전반적으로 대두되는 경량화에 대응하는 데 중요한 소재로 각광받고 있으며 그 활용이 활발하게 추진되고 있다. 본 연구에서는 이러한 동향에 대응하는 일환으로 POSCO에서 생산되고 있는 압연 마그네슘판재를 적용하였다. 적용 대상은 철도 분야의 경량화를 위한 전장품을 선정하고, 실물 크기로 제작하였다. 제작은 두께 3.5 mm 의 판재를 사용하였으며 용접은 Friction Stir Welding 및 GTAW 를 사용하였다. 그림1에 제작이 완료된 형상을 나타낸다. 그리고 제작중의 용접과정에 대하여 3차원 열탄소성 해석을 수행하여 변형 과정에 대한 검토를 수행하였다. 그림2에 해석과정의 한 예를 나타낸다.