• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.5
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• pp.568-575
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• 2015

A hand-made vehicle with a formula (VF-1) was designed and manufactured with the aim of realizing a lightweight and high-performance vehicle. The driver's body weight and stiffness of the frame were considered. The vehicle was equipped with a one-cylinder Exiv 250 engine with intake manifold potting for realizing weight reduction, high performance, and low cost. The suspension system for the formula was designed through the analyses and tests of vehicle motion and equipment. In a steering system, anti-Ackerman geometry was introduced to increase the transverse force during cornering. A full electric paddle shift system was adopted to decrease the braking distance. For protection against the distortion and warping of the frame, tungsten inert gas (TIG) welding technology was used.

• Journal of Preventive Medicine and Public Health
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• v.31 no.3 s.62
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• pp.414-423
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• 1998

Metal fume fever has been known as an occupational disease is induced by intense inhalation of fresh metal fume with a particle size smaller than $0.5{\mu}m\;to\;1{\mu}m$. The fumes originate from heating metals beyond their boiling point, as happens, for example, in welding operations. Oxidation usually accompanies this process. In most cases, this syndrome is due to exposure to zinc oxide fumes; however, other metals like copper, magnesium, cadmium, manganese, and antimony are also reported to produce such reactions. Authors report a case of metal fume fever suspected to be associated with copper fume inhalation. The patient was a 42-year-old male and was a smoker. He conducted inert gas tungsten arc welding on copper-coated materials without safety precautions such as a protective mask and adequate ventilation. Immediately after work, he felt metallic taste in his mouth. A few hours after welding, he developed headache, chilling sensation, and chest discomfort. He also complained of myalgia, arthralgia, feverish sensation, thirst, and general weakness. Symptoms worsened after repeated copper welding on the next day and subsided gradually following two weeks. Laboratory examination showed a transient increase of neutrophil count, eosinophilia, elevated erythrocyte sedimentation rate, and positive C-reactive proteinemia. Blood and urine copper level was also increased compared to his wife. Before this episode, he experienced above complaints several times after welding with copper materials but welding of other metals did not produce any symptoms. It was suggested that copper fume would have induced metal fume fever in this case. Further investigations are needed to clarify their pathogenic mechanisms.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.7-7
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• 2009

TIG 용접에서는 후판 용접의 경우 용입의 한계 때문에 깊고 넓은 그루브 가공을 하여 다층 용접을 한다. 이 때, 그루브를 채우는 용착금속에 의한 응고 수축과 과대한 입열로 인한 변형이 문제시 되고 있다. 변형을 줄이기 위해서는 용착금속의 양과 입열량을 줄여야 한다. 이러한 문제를 해결하기 위해 그루브의 루트패이스를 두껍게 하고 그루브각을 줄여서 용착량을 줄인다. 이때, 좁은 그루브에서 두꺼운 루트패이스를 완전 용입할 수 있는 용접 프로세스가 필요하다. 비드가 좁고 깊은 용입 특성을 가지는 Plasma welding(PAW) 경우에는 좁은 그루브 속에 토치가 접근하기 어려워 적용하기 어렵다. 따라서 접근성이 용이한 TIG 용접에서 높은 용입형상비를 가지는 용접공정 개발이 필요하다. 선행연구로 높은 용입 형상비를 가지는 Active flux Tungsten Inert Gas(ATIG) 용접이 연구되었다. ATIG의 용입 증가 메커니즘으로는 Marangoni effect, 음이온들로 인한 아크 수축 효과, 절연 플럭스에 의한 아크 수축효과 등으로 알려져 있다. 또한 선행연구에서 ATIG에서 Ar가스에 He 또는 $H_2$ 가스를 첨가하면 용입이 더욱 증가하는 것을 확인하였다. 본 연구에서는 A-TIG에 He 가스를 적용하고 아크길이 0.5mm, 1.0mm, 2.0mm와 전극 선단각 30도, 60도, 90도에 따른 용입 형상비와 변형량을 검토하기 위해 실험을 하였다. 실험 결과는 아크길이가 감소할수록 전극 선단각이 증가할수록 용입 형상비는 증가하였고, 변형량은 감소하였다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.515-519
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• 2011

Structural tests for the mixing head of a 75tonf class thrust chamber were performed to verify structural stability. The mixing head of a thrust chamber is loaded by high pressure with regeneratively cooled fuel and cryogenic liquid oxygen(LOx) as well as it transfers thrust load generated by liquid rocket engine. Therefore structural stability of mixing head is a very important factor to work without any plastic deformation or structural failure. In this study, two mixing heads were manufactured using different welding methods, Tungsten Inert Gas(TIG) welding and Electron Beam Welding(EBW) and evaluated a structural stability. The results of structural tests showed that the mixing head assembled by EBW can withstand the applied design load without any structural failures and be structurally more stable than that of TIG welding.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.1
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• pp.56-72
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• 1999

Airborne concentrations of welding fumes in which 13 different metals such as Al, Cd, Cr, Cu, Fe, Mn, Mo, Ni, Pb, Si, Sn, Ti, and Zn were analyzed were measured at 18 factories including automobile assembly and manufactures, steel heavy industries and shipyards. Air samples were collected by personal sampler at each worker's worksite(n=339). Blood levels of Cd, Cu, Fe, Mn, Pb and Zn were also measured from samples taken from 447 welders by atomic absorption spectrometry and compared with control values obtained from 127 non-exposed workers. The results were as follows ; 1. Among various welding types, $CO_2$ welding 70.2 % were widely used, shielded metal arc welding(SMAW) 22.1 % came next, and rest of them were metal inert gas(MIG) welding, submerged arc welding(SAW), spot welding(SPOT) and tungsten inert gas(TIG) welding. 2. Welding fume concentration was $0.92mg/m^3$($0.02{\sim}15.33mg/m^3$) at automobile assembly and manufactures, $4.10mg/m^3$($0.02{\sim}70.75mg/m^3$) at steel heavy industries and $5.59mg/m^3$($0.30{\sim}91.16mg/m^3$) at shipyards, respectively, showing significant difference among industry types. Workers exposed to high concentration of welding fumes above Korean Permissible Exposure Limit(KPEL) amounted to 7.9 % and 12.5 %, in $CO_2$ welding and in SMAW at automobile assembly and manufactures and 62.7 % in $CO_2$ welding, and 12.5 % in SMAW at shipyards, and 66.2 % in $CO_2$ welding and 70.6 % in SMAW at steel heavy industries. 3. Geometric mean of airborne concentration of each metal released from welding fumes was below one 10th of KPEL in all welding types. Percentage of workers, however, exposed to airborne concentration of metals above KPEL amounted to 16.8 % in Mn and 7.6 % in Fe in $CO_2$ welding; 37.5 % in Cu in SAW, 30 % in Cu in TIG; and 25 % in Pb in SPOT welding. As a whole, 76 Workers(22.4%) were exposed to high concentration of any of the metals above KPEL. 4. There were differences in airborne concentration of metals such as Al, Cd, Cr, Cu. Fe. Mn, Mo, Ni, Pb, Si, Sn, Ti and Zn by industry types. These concentrations were higher in shipyards and steel heavy industries than in automobile assembly and manufactures. Workers exposed to higher concentration of Pb above KPEI amounted to 7.4 % of workers(7/94) in automobile assembly and manufactures. In shipyards, 19.2 % of workers(19/99) were over-exposed to Mn and 7.1 % (7/99) to Fe above KPEL. In steel heavy industries, 14.4 %(21/146), 7.5 %(11/146) and 13 %(19/146) were over-exposed to Mn, Fe and Cu, respectively. As a whole, 76 out of 339 workers(22.4%) were exposed to any of the metals above KPEL. 5. Blood levels of Cd, Cu, Fe, Mn, Pb, and Zn in welders were $0.11{\mu}g/100m{\ell}$, $0.84{\mu}g/m{\ell}$, $424.4{\mu}g/m{\ell}$, $1.26{\mu}g/100m{\ell}$, $5.01{\mu}g/100m{\ell}$ and $5.68{\mu}g/m{\ell}$, respectively, in contrast to $0.09{\mu}g/100m{\ell}$, $0.70{\mu}g/m{\ell}$, $477.2{\mu}g/m{\ell}$, $0.73{\mu}g/100m{\ell}$, $3.14{\mu}g/100m{\ell}$ and $6.15{\mu}g/m{\ell}$ in non-exposed control groups, showing significantly higher values in welders but Fe and Zn.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.147-158
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• 2016

Objectives: The objective of this study was to evaluate the assessment of exposure to welding fume and heavy metals among construction welders. Methods: Activity-specific personal air samplings(n=206) were carried out at construction sites of three apartment, two office buildings, and two plant buildings using PVC(poly vinyl chloride) filters with personal air samplers. The concentration of fumes and heavy metals were evaluated for five different types of construction welding jobs: general building pipefitter, chemical plant pipefitter, boiler maker, ironworker, metal finishing welder. Results: The concentration of welding fumes was highest among general building pipefitters($4.753mg/m^3$) followed by ironworkers($3.765mg/m^3$), boilermakers($1.384mg/m^3$), metal finishing welders($0.783mg/m^3$), chemical pipefitters($0.710mg/m^3$). Among the different types of welding methods, the concentration of welding fumes was highest with the $CO_2$ welding method($2.08mg/m^3$) followed by SMAW(shield metal arc welding, $1.54mg/m^3$) and TIG(tungsten inert gas, $0.70mg/m^3$). Among the different types of workplace, the concentration of welding fumes was highest in underground workplaces($1.97mg/m^3$) followed by outdoor($0.93mg/m^3$) and indoor(wall opening as $0.87mg/m^3$). Specifically comparing the workplaces of general building welders, the concentration of welding fumes was highest in underground workplaces($7.75mg/m^3$) followed by indoor(wall opening as $2.15mg/m^3$). Conclusions: It was found that construction welders experience a risk of expose to welding hazards at a level exceeding the exposure limits. In particular, for high-risk welding jobs such as general building pipefitters and ironworkers, underground welding work and $CO_2$ welding operations require special occupational health management regarding the use of air supply and exhaust equipment and special safety and health education and fume mask are necessary. In addition, there is a need to establish construction work monitoring systems, health planning and management practices.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.1
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• pp.81-89
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• 2018

Austenitic stainless steels have excellent corrosion resistance, durability and fire resistance. Especially, since STS304L among austenitic types is a low-carbon variation of STS304 and has excellent intergranular corrosion resistance, it can often be used under the welded condition without heat treatment after field welding. This paper investigated ultimate behaviors such as ultimate strength and weld metal fracture mechanism of STS304L fillet-welded connections with TIG(tungsten inert gas) welding through test results. Main variables of specimens are weld length and welding direction against loading. Fracture of specimens are classified into three modes(tensile fracture, shear fracture and block shear fracture). Ultimate strengths were compared according to the welding direction and weld length and TFW series with transverse fillet weld had the highest strength compared with other types(LFW series with longitudinal fillet weld and FW series with all round weld). It is known that current design specifications such as KBC 2016 and AISC2010 underestimated the strength of TFW and LFW specimens and provided unconservative estimates for FW specimens. Finally, strength equations were proposed considering material properties of STS 304L material.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.1
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• pp.46-51
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• 2015

Stainless steel is a popular structural materials for liquid-hydrogen storage containers and piping components for transporting high-temperature fluids because of its superior material properties such as high strength and high corrosion resistance at elevated temperatures. In general, tungsten inert gas (TIG) arc welding is used for bonding stainless steel. However, it is often reported that the thermal fatigue cracks or initial defects in stainless steel after welding decreases the reliability of the material. The objective of this paper is to clarify the characteristics of ultrasonic guided wave propagation in relation to a change in the initial crack length in the welding zone of stainless steel. For this purpose, three specimens with different artificial defects of 5 mm, 10 mm, and 20 mm in stainless steel welds were prepared. By considering the thickness of s stainless steel pipe, special attention was given to both the L(0,1) mode and L(0,2) mode in this study. It was clearly found that the L(0,2) mode was more sensitive to defects than the L(0,1) mode. Based on the results of the L(0,1) and L(0,2) mode analyses, the magnitude ratio of the two modes was more effective than studying each mode when evaluating defects near the welded zone of stainless steel because of its linear relationship with the length of the artificial defect.