• Proceedings of the KWS Conference
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• 2004.05a
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• pp.197-199
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• 2004

용접성은 모재의 조직과 기계적 성질 및 Bond 부와 열영향부의 조직과 기계적 성질의 관계로 평가된다. 탈소 함량이 높은 레일강의 경우 용접을 하고 나면 열영향부에 마르텐사이트와 같은 취약조직을 형성하여 경도 값이 높아지고 인성이 저하되어 균열발생 가능성이 높아진다. (중략)

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.193-193
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• 2012

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.134-137
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• 1994

In this study, The mean weld current is used to correct depth direction, and weight-value, specially devised to check right-left deviation by placing more weight on the left- and right-most part of weld current during weaving, to correct weaving direction. The methodology of “design of experiments” was introduced to find out dorminant weld parameters affecting these for values.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.469-472
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• 2003

알루미늄 및 그 합금은 가볍고 강도가 높으며, 내식성과 재활용성이 뛰어난 특성을 가지고 있어서 각종 구조물 및 부품의 경량화가 요구되는 분야에 급속하게 이용이 확산되고 있다. 특히, 고속전철, 지하철 등의 철도차량, 선박, LNG선 탱크, 건축 등은 물론이고, 알루미늄 엔진 및 차체개발로 경량화를 목표로 하는 자동차 산업에 확대 적용되고 있다.(중략)

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.217-219
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• 2005

In the conventional GMAW of 9% Ni steel, Inconel wire has been employed. The major problem of the Inconel GMAW is that arc stability and fluidity of weld pool is poor. Lack of fusion and convex weld bead is liable to occur in case of 9% Ni steel because of low melting point of Inconel wire. In this study the effect of shielding gases on the Inconel 625 GMA weldability was investigated.

• Proceedings of the KIEE Conference
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• summer
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• pp.1278-1280
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• 2004

In this paper, we propose a new diagnosis method of DC/DC converter aging. The method is based on the variations of parasitic resistor for the aging process. We apply an on-line diagnosis of DC/DC converter because the observation is not a device, but a system. This study proposes a method of DC/DC converter diagnosis by analyzing the variations of model on the variations of parasitic resistor.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.2
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• pp.99-107
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• 2008

We quantified the human carcinogenic metals (chromium, nickel) in fumes from flux cored arc welding using stainless steel (FCAW/SS) wires. Zinc and calcium were also quantified because of their possibility of zinc chromate and calcium chromate, respectively. Welding was performed in an American Welding Society standard fume collection chamber. Insoluble and soluble forms of metals were analyzed by ISO 15202 method. Total chromium (insoluble+soluble) content and total nickel content were lower in FCAW/SS fumes (4.65%, 1.05%, respectively)than in stainless steel content (ca. 18%, 8%,respectively). Insoluble fraction in total chromium was 79.8 (range 64.5~95.1)% and 94.4(range 90.1~98.1)% in total nickel. Atomic emission spectroscopy used in this study does not differentiate the chromium valence status while ACGIH defines its carcinogenicity according to the valence status. From this study and previous study, we estimated the hexavalent chromium content in FCAW/SS was 0.2~1.1% and about 85% of them was soluble. The content of zinc and calcium, which can be existed as chromate forms, was low (0.02 %, 0.04% respectively) in FCAW/SS. Exposure assessment for zinc chromate and calcium chromate is possible because chromium in both compounds is used as a surrogate even though it is not well known that what compounds of zinc and calcium are formed in welding fume.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.135-144
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• 1999

The purposes of this study were to survey types of pretreatment methods adopted by industrial hygiene laboratories in Korea for extracting heavy metals in welding fume samples and to compare performances of two pretreatment methods, the acid extraction and the microwave digestion, in extracting heavy metals contained in the real workplace samples from various welding jobs including arc, argon, and carbon dioxide. A total of 25 analytical chemists in the industrial hygiene laboratories participating the quality control program directed by the Korea Industrial Safety Corporation were interviewed by telephone. For the purpose of comparing performance of extracting heavy metals from real workplace samples, a total of 53 welders from 21 workplaces located in Anyang, Uiwang, and Kunpo areas were sampled from the period of March 22, 1999 to April 20, 1999. It was found that the most frequently adopted method for samples from the quality control program was the acid extraction method(40%) followed by the NIOSH 7300 method(36%). The NIOSH method, however, was the dominant method(36%) for samples from workplace followed by the acid extraction method(28%). In this study, two extraction methods, the acid extraction and the microwave digestion, were compared in terms of recovery rate, accuracy, and precision for both manganese and chromium. Both methods produced comparable results for the samples prepared for the quality control program. In contrast, concentrations of two heavy metals determined from real workplace samples pretreated with the microwave digestion method were statis tically significantly higher, manganese(166%) and chromium (200%), than those of utilizing the acid extraction method. These findings were consistent regardless of types of welding techniques used. The results of this study clearly show the importance of verifying the analytical performances of extraction methods for heavy metals not only for the samples from the quality control program but also from the real world samples collected from welding jobs.

• Journal of Welding and Joining
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• v.28 no.4
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• pp.26-32
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• 2010

The purpose of this study is to evaluate the residual stresses at the multi-pass FCA weldment using the finite element analysis (FEA). In order to do it, an H-type specimen was selected as a test specimen. The variable used was in-plane restraint intensity. The temperature distribution at the multi-pass FCA butt weldment was evaluated in accordance with the relevant guidance recommended by the KWJS. The effective conductivity for the weld metal corresponding to each welding pass was introduced to control the maximum temperature below the vaporization temperature of weld metal. The heat flux caused by welding arc was assumed to be applied to the weld metal corresponding to welding pass. With heat transfer analysis results, the distribution of transverse residual stresses was evaluated using the thermo-mechanical analysis and compared with the measured results by XRD and uniaxial strain gage. In thermo-mechanical analysis, the plastic strain resetting at the temperature above melting temperature of $1450^{\circ}C$ was considered and the weld metal and base metal was assumed to be bilinear kinematics hardening continuum. According to the comparison between FEA and experiment, transverse residual stresses at the multi-pass FCA butt weldment obtained by FEA had a good agreement with the measured results, regardless of in-plane rigidity. Based on the results, it was concluded that thermo-mechanical FE analysis based on temperature distribution calculated in accordance with the KWJS’s guidance could be used as a tool to predict the distribution of residual stress of the multi-pass FCA butt weldment.

• The Journal of Korean Academy of Prosthodontics
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• v.40 no.2
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• pp.156-171
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• 2002

The purpose of this study was to measure and compare the strains produced by screw-tightening implant frameworks fabricated by aye different fabrication methods; (1) one-piece cast using plastic sleeve, (2) one-piece cast using gold cylinder, (3) laser welding, (4) soldering, and (5) electrical discharge machining, and also to measure and compare the strains produced when the order of screw tightening was changed A research model incorporating eighteen strain gages was made to measure the fit of implant frameworks in three dimensions. Three implants aligned in an arc were fixed on the top ends of the L-shape aluminum bars of the research model, and standard abutments were joined to the implants with abutment screws. Five types of implant framework were placed on the abutments and screwed by a torque wrench using 10 Ncm. Under the conditions of this study, the following conclusions were drawn: 1. The electrical discharge machining group showed the smallest magnitude of strain, followed by the soldering group, the laser welding group, the one-piece cast group using gold cylinder, and the one-piece cast group using plastic sleeve. However, among the magnitude of strain for the remaining groups except the electrical discharge machining group, there were not significant differences. 2. When the order of screw tightening was changed, there were not significant differences in the magnitude of strain. 3. In comparison with the electrical discharge machining group, the laser welding group and the one-piece cast groups showed greater horizontal distortion and the soldering group showed greater horizontal and vertical distortion.