• 한국산업보건학회지
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• 제16권3호
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• pp.254-263
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• 2006

Manganese has a role as both toxic and essential in humans. Manganese is also an essential component in the welding because it increases the hardness and strength, prevents steel from cracking of welding part and acts as a deoxidizing agent to form a stable weld. In this study, manganese generation rate and its content was determined in flux cored arc welding on stainless steel. Domestic two products and foreign four products of flux cored wires were tested in the well designed fume generation chamber as a function of input power. Welding fume was measured by gravimetric method and metal manganese was determined by inductively coupled plasma-atomic emission spectrophotometer. The outer shell of the flux cored wire tube and inner flux were analyzed by scanning electron microscopy to determine their metal compositions. Manganese generation rate($FGR_{mn}$) was increased as the input power increased. It was 16.3 mg/min at the low input power, 38.1 mg/min at the optimal input power, and up to 55.4 mg/min at the high input power. This means that $FGR_{mn}$ is increased at the work place if welder raise the current and/or voltage for the high productivity. The slope coefficient of $FGR_{mn}$ was smaller than that of the generation rate of total fume(FGR). Also, the correlation coefficient of $FGR_{mn}$ was 0.65 whereas that of FGR is 0.91. $FGR_{mn}$ was equal or higher in the domestic products than that of the foreign products although FGR was similar. From the electron microscopic analytical data, we concluded that outer shell of the wire was composed mainly of iron, chromium, nickel and less than 1.2 % of manganese. There are many metal ingredients such as iron, silica, manganese, zirconium, titanium, nickel, potassium, and aluminum in the inner flux but they were not homogeneous. It was found that both $FGR_{mn}$ and content of manganese was higher and more varied in domestic flux cored wires than those of foreign products. To reduce worker exposure to fumes and hazardous component at the source, further research is needed to develop new welding filler materials that improve the quality of flux cored wire in respect to these points. Welder should keep in mind that the FGR, $FGR_{mn}$ and probably the generation rate of other hazardous metals were increased as the input power increase for the high productivity.

• 한국산학기술학회논문지
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• 제20권8호
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• pp.649-656
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• 2019

조선소, 교량 구조물, 건설기계, 플랜트 산업 등 다양한 분야에서 폭 넓게 활용되고 있는 이산화탄소 아크용접(FCAW: Flux Cored Arc Welding)은 피복 아크 용접(SMAW: Shielded Metal Arc Welding)의 단점을 보완하기 위한 대안으로 1950년대 초 개발되었다. FCAW는 모든 자세에서 용접이 가능하고 작업여건 변수가 많은 현장에서 우수한 품질을 얻을 수 있는 장점이 있어 탄소강과 합금강의 중판, 후판 용접에 많이 사용되고 있다. 본 연구에서는 FCAW를 이용하여 SS400(일반구조용 압연강재)와 SM490A(용접구조용 압연강재)를 이종용접한 후 용접부의 기계적 특성(인장시험, 굽힘시험, 경도시험, 충격시험, 매크로시험)을 분석하고 다음과 같은 결론을 도출하였다. 인장시험 결과, 모든 용접자세에서 KS 규격 인장강도 범위($400{\sim}510N/mm^2$)를 만족하였다. 굽힘시험 결과, 대부분의 시편에서 굽힘시 표면의 터짐 현상이나 기타 결점이 나타나지 않았고, 소성변형 후에도 충분한 인성을 발휘하는 것을 확인할 수 있었다. 경도시험 결과, 모든 결과 값이 KS B 0893의 규격치 350Hv보다 낮게 나타나 양호한 것으로 판단된다. 충격시험 결과, 모든 결과가 KS 기준 수치인 27J 보다 큰 것으로 나타났다. 매크로시험 결과 용접부의 형상별로 균일한 조직 상태를 나타냈으며, 용접부 전단면에 걸쳐 내부 결함, 기포 또는 불순물 등이 발견되지 않아 라미네이션의 우려가 없는 것으로 나타났다.

• Journal of Welding and Joining
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• 제32권1호
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• pp.15-21
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• 2014

FCAW(Flux Cored Arc Welding), SAW(Submerged Arc Welding), EGW(Electro Gas Welding), and three-pole SAW are applicable in manufacturing the offshore wind tower. In this paper, mechanical properties of these welded-joints for TMCP steels were evaluated in all above welding processes. The tensile strength of welded-joints for all the welding methods satisfied the standard guideline (KS D 3515). No cracking on weldment was found after the bending test. Changes of weldedments hardness with welding processes were observed. In a weld HAZ (heat-affected zone), a softened HAZ-zone was formed with high heat input welding processes (SAW and EGW). However, the welded-joint fractures were found in the base metal for all cases and small decrease in welded-joint strength was caused by a softened zone. The multi-pole SAW welds exhibited similar mechanical properties comparing to the one with one-pole SAW process.

• Journal of Welding and Joining
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• 제34권6호
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• pp.28-34
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• 2016

Galvannealed(GA) steels are now generally used in car body manufacturing for corrosion resistance. In this study, the weldability and joint mechanical behavior of a newly developed 1.2GPa grade GA ultra high strength TRIP(transformation induced plasticity) steel was investigated for three joining processes, such as adhesive bonding, resistance spot welding and weldbonding. Under both shear and peel stress conditions, the failure mode of the adhesive joints were the mixture of the adhesive cohesive failure, adhesive interface failure and coating layer failure. It means that the adhesion strength of GA coating onto the base metal was similar to that of adhesive bonding onto the GA coating. Under the shear stress condition, the weldbonding exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel because the strength of adhesive bond overwhelmed that of the resistance spot weld. Under the peel stress condition, the weldbonding also exerted to expand the optimal spot welding condition of 1.2GPa GA TRIP steel by inducing the tear fracture mode rather than the partial plug fracture mode.

• 비파괴검사학회지
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• 제29권2호
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• pp.153-161
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• 2009

2002년 미국 Davis Besse 원전에서 원자로 압력용기의 상부헤드 관통관 부위의 손상이 발견되고, 2002년 벨기에 Tihange 2호기 및 2003년 일본 쓰루가 원전의 가압기 노즐에서 균열이 발견되어 세계적으로 니켈합금기기의 일차 수응력 부식균열(PWSCC; primary water stress corrosion cracking)이 원자력안전에 상당히 위협적임을 인식하게 되었다. 이에 따라 2005년부터 4년간 계획으로 미국 NRC를 중심으로 니켈합금기기의 검사에 관한 국제공동연구(PINC; program for the inspection of nickel alloy components, 이하 PINC라 함)를 시작하였고 본 논문에는 2005년부터 수행된 PINC 국제공동연구의 수행현황에 대해서 소개한다. PINC 국제공동연구의 목적은 일차 수응력 부식균열의 형상(morphology)을 규명하고, 일차 수응력 부식균열에 대한 비파괴검사기법을 평가하는 것이다. 이 목적을 위하여 한국에서는 한국원자력안전기술원(Korea Institute of Nuclear Safety, KINS, 이하 KINS라 함)을 주축으로 한국원자력연구원, 성균관대, 원자력발전기술원, 한전KPS, (주)엔스코, (주)UMI, (주)세안, 두산중공업(주)이 참가하였고, PINC 수행 결과는 2009년 상반기에 NUREG 보고서로 발간될 예정이다. 이러한 국제공동연구를 수행함으로써 국내 기계재료분야의 결함 형성 및 분석기술이 선진국 수준임을 과시하고, 국내 비파괴검사 기술을 선진국 수준으로 끌어 올릴 수 있었으며, 이번 기회를 통하여 국내 산학연이 서로 협력하여 니켈합금기기의 건전성평가 기술을 한 단계 상승시킬 수 있었다.