• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 F
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• pp.2155-2158
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• 1997

This paper describes the performance improvement of dc TIG (Tungsten Inert Gas) welder. The TIG welder consists of single phase full bridge IGBT inverter which incorporates the high frequency transformer, the boost converter for improving the input power factor, and the arc start system. The arc will be generated without fail even when the extension cable between the torch and the power source is 100m long. In addition, the arc start system with a short dc output voltage will generate less EMI noise than the traditional arc start system with a high frequency output voltage. To demonstrate the practical significance of the proposed methods, some simulation studies are presented.

• Journal of Welding and Joining
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• 제33권4호
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• pp.50-56
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• 2015

In general, discontinuity of metallurgical and structural points of weld zone could decline the fatigue strength. For the lightweight trend, the AHSS application in automotive chassis is in-progress. However, there are few research reports on AHSS welds fatigue strength in especially automotive chassis parts. Therefore, in this study, we evaluated the effects of the factors affecting the AHSS welding fatigue strength. As the result, the stress concentration of weld bead is the most important factor for welding fatigue strength. For the enhancement of welding fatigue strength, we focused on reducing the stress concentration of the welding beads. So, we applied and proved the plasma welding process and GTAW (Gas Tungsten Arc Welding) dressing method. It was verified by uniaxial fatigue specimen, fatigue performance increased from 40 to 60% by applying TIG dressing method compared to the conventional GMAW (Gas Metal Arc Welding). These results could be recommended the enhancement of fatigue performance of AHSS.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2053-2058
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• 2008

Extruded aluminium panels have been widely used for railway vehicle structures because of their light specific weight and other merit. 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-T6 which are used for car body structures was chosen. The influence of main parameters such as : pin rotating speed, welding speed, shoulder diameter, pin length and tilting angle on mechanical properties was examined. Optical microscope observation, micro hardness test and tensile test were carried out. Tensile strength of the stir welded plates is 74% of that of the base material.

• 한국정밀공학회지
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• 제14권1호
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• pp.150-157
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• 1997

Uniform weld pool shape is important in determining the weld quality. And weld pool width is one of the most dominant factors of the seld pool shape. In order to control the weld pool width, the fuzzy logic controller, which is well adapted to the complicated nonlinear systems such as welding, was used in this study. The weld pool image was obtained through CCD camera, and the weld pool width was calculated by processing the image. Uaing the calculated width, welding speed, as a control input, was inferred by the fuzzy logic controller. An uniform weld pool width can be successfully obtained regardless of the disturbances in the system.

• 한국분말재료학회지
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• 제22권3호
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• pp.181-186
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• 2015

In this study, the effect of the friction stir welding (FSW) was compared with that of the gas tungsten arc welding (GTAW) on the microstructure and microhardness of Cu-Ni alloy weldment. The weldment of 10 mm thickness was fabricated by FSW and GTAW, respectively. Both weldments were compared with each other by optical microstructure, microhardness test and grain size measurement. Results of this study suggest that the microhardness decreased from the base metal (BM) to the heat affected zone (HAZ) and increased at fusion zone (FZ) of GTAW and stir zone (SZ) of FSW. the minimum Hv value of both weldment was obtained at HAZ, respectively, which represents the softening zone, whereas Hv value of FSW weldment was little higher than that of GTAW weldment. These phenomena can be explained by the grain size difference between HAZs of each weldment. Grain size was increased at the HAZ during FSW and GTAW. Because FSW is a solid-state joining process obtaining the lower heat-input generated by rotating shoulder than heat generated in the arc of GTAW.

• 동력기계공학회지
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• 제15권6호
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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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• 제37권1호
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• pp.29-34
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• 2013

용접과정 중에 용접부가 공기에 노출되면 용접성능을 약화시킨다. 불활성가스 텅스텐 아크용접(GTAW)법을 사용하여 티타늄 용접을 하는 경우 용접부가 자주/적색, 청색, 노란색, 회색, 흰색 등의 빛깔을 보이면 이는 용접 시 공기 중의 산소와 질소에 오염된 것을 의미한다. 따라서 용접부를 대기로부터 보호하기 위한 방법으로 실딩 가스를 사용한다. 이것은 대기에 의한 오염을 방지할 뿐만 아니라 용착부와 열영향부도 상온까지 냉각될 때까지 대기로부터 차단시킨다. 본 연구에서는 Trailing Shielding Jig 의 모양과 형태 그리고 토치보호($13{\sim}20{\ell}/min$), 후방보호($22{\sim}30{\ell}/min$), 이면보호($25{\sim}30{\ell}/min$)등 건전한 용접부에 적합한 실딩 가스에 대한 결과를 도출하였다.

• 한국공작기계학회논문집
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• 제15권5호
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• 한국표면공학회지
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• 제47권4호
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• pp.174-180
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• 2014

In this study, TiAlSiN coatings have been successfully synthesized on stainless steel and tungsten carbide substrate by a hybrid coating method employing a cathodic arc and a magnetron sputtering source. TiAl and Si target were vaporized with the cathodic arc source and the magnetron sputtering source, respectively. Process gas was the mixture of nitrogen and argon gas. With the increase of Si content, the crystallinity and the grain size of TiAlSiN film was decreased. At the Si content of more than 8 at.%, grain size of TiAlSiN was saturated at around 2 nm. The hardness value of the TiAlSiN film increased with incorporation of Si, and had the maximum value of ~ 3,233 Hv at the Si content of 9.2 at.%. The oxidation resistance of TiAlSiN film was enhanced with the increase of Si content.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.144-145
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• 2007

Magnesium alloys are the lightest in commercial alloys. Also, they have high damping capacity and the shielding effect of electromagnetic waves. Recently, magnesium alloys have received considerable attention from the transportation industry. Many manufacturers of cars try to increase the use of magnesium alloys in their product. In order to evaluate the weldability of magnesium alloy, gas-tungsten arc welding(GTAW) have been applied to the AZ31, AZ61 and AZ91 alloys and established the optimum welding conditions.