• Proceedings of the KWS Conference
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• 2009.11a
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• pp.67-67
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• 2009

알루미늄 합금 재질은 무게의 경량화와 기계적강도가 우수하며 다른 비철금속에 비하여 값이 저렴한 장점이 있다. 현재 산업현장에서 활용하는 가장 흔한 접합법으로 TIG, RSW 등과 같은 용융 용접법을 현재는 많이 사용 하고 있지만 열전도도가 높아 열 확산이 빠르고, 이에 따라 모재의 팽창이 일어나 열변형을 유발하며, 산화피막은 그 내부에 함유된 결정수가 아크용접 중 분해되어 수소를 방출함으로 기공이 발생하여 부도체로 저항용접시 전도성을 방해하는 등의 문제를 발생시킨다. 또한 철에 비해 4배정도 큰 전기전도율에 따라 저항용접시 대전류를 사용해야 하는 등의 문제점이 발생하고 있다. 이와 같은 알루미늄 합금의 용융용접 과정에서 발생하는 단점을 극복하는 기술로 고상접합 방법인 마찰교반용접법(Friction Stir Welding)이 활용되고 있다. FSW는 1991년 영국의 TWI에서 개발된 최신 용접법으로 모재를 용융점 아래에서 고상용접시키는 방법으로 용융에 따른 열변형과 흄가스(hume gas)와 스패터(spatter)를 억제시켜 주는 친환경적인 용접법이다. 이러한 마찰교반용접의 기술은 그동안 특허에 따른 로열티가 산업현장에서 사용하는데 문제가 되었으나 특허보호 기간인 20년이 1년정도의 기간밖에 남지 않은 상황에서 그 사용은 날로 증가하리라 본다. 이러한 마찰교반용접부의 결함을 평가하는 방법에는 UT, RT 등이 활용되고 있으나 얇은 박판에서의 결함검출은 용이하지 않다. 이리한 문제점을 해결하기위하여 초음파 가진을 이용한 적외선 열화상 검출 기법을 이용하여 마찰교반용접부의 결함 검출 가능성을 연구하였다. 20kHz의 주파수를 400Watt로 가진시켜 겹치기(lap joint) 마찰교반용접이된 A6061-T6의 용접부에 초음파를 입사하였을 때 발생하는 열을 적외선 열화상 카메라를 이용하여 측정함으로써 마찰교반겹치기 용접부의 결함 검출에 활용하였다. 용접부에 초음파를 입사하였을 때 부분적으로 온도차이가 발생하였고, 그에 따른 열화상을 검출 할 수 있었다. 이러한 열화상과 실제 시험편의 용접부의 강도를 평가하기 위하여 인장시험을 하였다. 그 결과 초음파 적외선 열화상 검출에서 발열부위가 나타난 부분이 인장시험에서 낮은 인장강도를 보였다.

• Journal of Environmental Health Sciences
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• v.27 no.4
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• pp.51-62
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• 2001

Geometric mean of airborne welding fume concentration at technical high schools was 4.80mg/㎥)N.D~35.39 mg/ ㎥ and the percentage of samples exceeded TLV of the Korean ministry of labor was 43.6%, Geometric mean of airborne Mn concentration was 0.06 mg/㎥(N.D~0.42mg/㎥) and the percentage of samples exceeded TLV of ACGIH was 15.4 % In case of airborne Me concentration, there is a significant difference among schools (p<0.05) Mn concentrations in blood of the exposed and control groups were 1.84$\mu\textrm{g}$/dl and 1.91 mg/dl respectively. Mn concentrations in urine of the exposed and control groups were 1.36$\mu\textrm{g}$/ιand 0.57$\mu\textrm{g}$/ι respectively. In case of Mn concentrations in urine there is a significant difference between both groups(P<0.001) and among schools(p<0.05) Mn concentrations in blood and urine of exposed group were not over BEIs of the Korean ministry of labor. Mn levels in blood and urine were not significantly affected by smoking, drinking and residence, There was no correlation between Mn concentration in air and blood but there was a statistically significant correlation between Mn concentration in air urine(r=0.323). There was no a statistically significant correlation between Mn concentration in blood and urine.

• Toxicological Research
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• v.20 no.1
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• pp.55-61
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• 2004

Respiratory effects in full time welders include bronchitis, airway irritation, lung function changes, and lung fibrosis. Welder's pneumoconiosis has been generally determined to be benign and not associated with respiratory symptoms based on the absence of pulmonary function abnormalities in welders with marked radiographic abnormalities. Accordingly, to investigate pulmonary function changes during 60 days induced by welding-fume exposure, male Sprague-Dawley rats were exposed to manual metal arc-stainless steel (MMA-SS) welding fumes with concentrations of 64.8$\pm$0.9 mg/$m^3$ (low dose) and 107.8 $\pm$ 2.6 mg/$m^3$ (high dose) total suspended particulates for 2 hr/day, 5 days/week in an inhalation chamber for 60 days. Pulmonary function was measured every week with whole body plethysmograph compensated (WBP Comp, SFT38116, Buxco Electronics, Sharon, CT). The rats exposed to the high dose of welding fumes exhibited statistically significant (p<0.05~0.01) body weight decrease as compared to the control whereas cell number increase of the bronchoalveolar lavage fluid (BALF) (total cell, macrophage, polymorphonuclear cell and lymphocyte) during the 60 days exposure period. And only tidal volume was significantly decreased in dosedependantly during 60 days of MMA-SS welding fume exposure. This pulmonary function change with inflammatory cell recruitment confirms the lung injury caused by the MMA-SS welding fume exposure.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.1
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• pp.1-8
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• 2001

This study was performed to evaluate a local exhaust ventilation system capability and welding fume concentration in welding laboratory at 5 technical high schools. Results of the study are as follows; 1. The personal exposure of welding fume in welding laboratory was measured. The geometric mean of 73 personal samples was $6.27mg/m^3$($3.85{\sim}9.88mg/m^3$), and 68.5% of these exceeded TLV of the Korea Ministry of Labor. 2. The geometric mean of welding fume at outside of booth was $2.27mg/m^3$($1.57{\sim}2.58mg/m^3$). All of measured concentrations were lower than TLV of the Korea Ministry of Labor. 3. Local exhaust ventilation system in welding laboratory could not remove hazardous substance effectively because of inappropriate canopy hood and absurd design. 4. The possibility of exposure risk was estimated to be high because of working point under breathing zone, misplacement of working table and insufficient supply of respiratory protector. 5. The mean values of capture velocity and transportation velocity of local exhaust ventilation system in welding laboratory were 0.38m/sec, 4.27m/sec respectively. These values were satisfied the guideline of the Korea Ministry of Labor. 6. The efficiency of performance of local ventilation system was anticipated to be decreased because of accumulated dust and alien substance on fan and duct.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.172-183
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• 1995

The airborne concentrations of the welding fumes produced during $CO_2$ arcwelding process at shipbuilding, shiprepairing, container manufacturing and car accessary manufacturing industry were investigated. The effects how much reduced the welding fume were checked when the portable fan was used. The results were as follows; 1.The geometric mean of welding fume concentration in shipbuilding factory was $10.05mg/m^3$. This exposure concentration was higher than other 3 manufacturing industries at 95% confidence level. 2. The sampling filters for welding fume could be digested with acid within 1 hour by microwave oven. The recoveries for investigated metal elements were all over 95%. 3. The optimal wavelength could be selected for the simultaneous analysis of 8 metal elements by ICP(Inductively Coupled Plasma). 4. Noxious gases($O_1,NO_2$) produced during $CO_1$ gas arc welding process were detected that the concentration of ozone($O_1$) was less than 0.01 ppm and that of nitrogen dioxide($NO_2$) was 0.01-0.03 ppm. 5. The geometric mean of welding fume particle diameter was $1.26{\mu}m$ and geometric standard deviation was 1.51 for the counts when particle an analyzer(ELZONE) had been used. 6. When the portable fan had been used,the reduced percent of total welding fume for workers was about 47.8% when portable fan was applied to blow and 71.7% when to exhaust.

• Journal of Environmental Health Sciences
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• v.33 no.4
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• pp.276-282
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• 2007

The purpose of this study is to assess the accurate state of the following: total welding fumes versus welding fumes in the air, respirable particulate mass, and exposure of dockyard welders to heavy metals. In addition, this study provides basic data for proposing improvements to create efficient and appropriate welding environments and to prevent occupational diseases. The subjects of this study were 94 laborers who worked at the block construction sites of large-scale dockyards located in Gyeongnam Province from March 2005 to June 2005. In order to collect samples on total welding fumes in the air and respirable particulate mass from the welders, Methods 0500 and 0600, established by the National Institute for Occupational Safety and Health (NIOSH), were used. The metals within the welding fumes were also analyzed using Inductively Coupled Plasma (ICP) under Method 7300 from NIOSH. The results of this research are summarized below. The geometric mean concentration of total welding fumes and that of respirable particulate mass were $4.11\;mg/m^3\;and\;3.53\;mg/m^3$, respectively. As a result of comparing the two measurement methods, there were significant differences (p<0.05) between the two groups for Ca, Cu, Cr, and Ni; however, there were no differences in Fe, Mg, Zn, Mg, Pb, and Cd. As a result of the analysis, the correlation between Mn and the concentration of heavy metals in the total welding fumes and respirable particulate mass was found to be -0.29, a significant negative correlation. The correlation between other heavy metals, however, was low. Finally, in the same total welding fumes, the correlation of Fe and Mg was high.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.11 no.1
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• pp.42-47
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• 2001

The purpose of this study was to investigate for filtration efficiency of several dust masks, comparing with filtration efficiency certified by KOSHA(Korea Occupational Safety & Health Agency), and to require of the right use of protective respirators. Using a welding fume generator and chamber, several dust masks, which were widely used in the workplaces in korea, were tested for their filtering efficiency for stainless steel arc welding fume. The filtration efficiency testing system consisted of a welding fume generator, a chamber and a filtration unit. The filtration unit was made of a mask which was inserted into the sampling cassette and another sampling cassette, which contained mixed cellulose ester filter paper. These two cassettes were connected with tubing. Stainless steel arc welding fume generator was delivered into an chamber. The welding fume in the chamber was passed into the filtration unit with flow rate of 30 liter/min. The welding fume filtration efficiency was evaluated by gravimetric measurement. Metal concentrations in the welding fume before and after filtration were measured with inductive coupling plasma analyzer. Following results were obtained: Filtration efficiency of welding fume for common hygienic mask was 63.82% and the average efficiencies for A, B, C, D, E, F and G masks were 94.62%, 96.58%, 83.20%, 82.76%, 77.25%, 86.55% and 93.22%, respectively. Our results indicate that dust masks used widely in the welding workplaces in korea are not proper for protecting worker's health and then the use of fume mask should be required.

• Proceedings of the Korean Environmental Health Society Conference
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• 2002.04a
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• pp.37-39
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• 2002

Geometric mean of airborne welding fume concentration at technical high schools was 4.80mg/㎥(N.D∼35.39mg/㎥) and the percentage of samples exceeded TLV of the Korean ministry of labor was 43.6％, Geometric mean of airborne Mn concentration was 0.06mg/㎥(N.D∼0.42mg/㎥) and the percentage of samples exceeded TLV of ACGIH was 15.4％. In case of airborne Mn concentration, there is a significant difference among schools (P＜0.05). Mn concentrations in blood of the exposed and control groups were 1.84$\mu\textrm{g}$/㎗ and 1.91$\mu\textrm{g}$/㎗, respectively. Mn concentrations in urine of the exposed and control groups were 1.36$\mu\textrm{g}$/$\ell$ and 0.57$\mu\textrm{g}$/$\ell$, respectively. In case of Mn concentrations in urine, there is a significant difference between both groups(P＜0.001) and among schools(P＜0.05). Mn concentrations in blood and urine of exposed group were not over BEIs of the Korean ministry of labor. Mn levels in blood and urine were not significantly affected by smoking, drinking and residence. There was no correlation between Mn concentration in air and blood, but there was a statistically significant correlation between Mn concentration in air and urine(r=0.323). There was no a Statistically significant correlation between Mn concentration in blood and urine.

• 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 Environmental Health Sciences
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• v.25 no.3
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• pp.108-112
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• 1999

A study was conducted for the effects of input energy on fume formation ratios based on electrode(FFR$_{electrode}(g/kg_{electrode})),\;deposited\;metal(FFR_{weld}(g/kg_{weld}))\;and\;slag(FFR_{slag}(g/kg_{slag}))\;at\;CO_2$ flux cored arc welding on stainless steel. Experiments were run in well designed welding fume box. Six types of flux cored wires were used and three levels of current and voltages were given. The measured values of $FFR_{electrode},\;FFR_{weld},\;FFR_{slag}\;are\;7.90{\pm}1.47\;g/kg_{electrode},\;9.18{\pm}1.65\;g/kg_{\electrode},\;71.8{\pm}24.2\;g/kg_{slag}$ respectively. Fume formation ratios are not increased dramatically by input energy because of simultaneous increasing of melted electrodes, deposited metal and slag. The results indicate that the test of fume formation ratios in the research on production of low fume welding wire can be run at the fixed condition of input energy rather than various condition.