• 한국공작기계학회논문집
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• 제14권3호
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• pp.87-95
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• 2005

The object of this study is to investigate the effect of joinability by using acoustic emission(AE) signals and doing a pattern recognition for weld heat affected zone(HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding(SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding $>\;CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.40-48
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• 2004

The object of this study is to investigate the effect of joinability by using acoustic emission (AE) signals and doing a pattern recognition for weld heat affected zone (HAZ) in tensile testing. This study was carried out an SWS 490A high tension steel for electric shielded metal arc welding (SMAW), $CO_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. The results of the tensile test of weld HAZ come out electric shield arc welding > $CO_2$ gas arc welding > TIG welding in case of single welding. It is believed that this is a phenomenon where difference of its root opening or base metal thickness. Also, the technique of AE is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 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.

• 열처리공학회지
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• 제7권1호
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• pp.35-43
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• 1994

For the purpose of studying the change of mechanical properties of weld parts, shielded metal are welding, one-pole and two-pole submerged arc welding were accomplished weldability on $60kg/mm^2$ quenched and tempered high strength steel. Charpy impact values of the weld metal in welded parts by SMAW and SAW were lower than those of the heat affected zone and increased in order of bond, coarsened, refined and carbon spheroidized regions in the heat affected zone. Grain size of prior austenite or M-A constituent did not significantly affect toughness of welded parts, but precipitated carbide films which forms at the grain boundaries or within matrix and volume fraction of pearilte were most important factor for toughness.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.289-294
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• 2003

The object of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals fur weld heat affected zone (HAZ) in tensile testing. This study was carried out a SM 490A high tension steel for electronic shielded metal are welding (SMAW), $\textrm{CO}_2$ gas arc welding and TIG welding. And correspondingly, the root openings are 3, 4 and 2.8mm. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. These history plots give us useful and powerful information to analyze the results of material evaluation testing.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.365-369
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• 2004

Recently, Inconel 625 is used widely in offshore processing piping in order to extend the maintenance tenn and improve the quality of anti-corrosion. According to the resistance to attack in various corrosive media at temperatures from $200^{\circ}C$ to aver $1090^{\circ}C$, in combination with good low- and high-temperature mechanical strength. In general, High quality weldments for this material are readily produced by commonly used processes. in recent years, the flux cored arc welding(FCAW) process is becoming more popular due to higher deposition rate and a better weld quality as compared to the shielded metal arc welding (SMAW) process, at the same time, exhibiting equally good weld metal toughness similar to the SAW process. In this study, the weldability and weldment characteristics(mechanical properties and corrosive environment) of Inconel 625 are considered in FCAW weld associated with the several weld shielding gases($80\%Ar\;+\;20\%\;CO_2,\;50\%Ar\;+\;50\%\;CO_2,\;100\%\;CO_2$) in viewpoint of welding productivity.

• Journal of Advanced Marine Engineering and Technology
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• 제12권3호
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• pp.57-67
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• 1988

Although handicapped by the inability to bridge the size gap between small laboratory sample and large engineering component, the V charpy test sample method does possess certain advantages, such as each of preparation, simplicity of test method, speed, low cost in test machinery, and low cost per test. On the other hand, the COD test method does posses advantages, which reduce the size gap between the laboratory sample and actual engineering component. Consequently, the correlation between V charpy absorbed energy and the critical COD value is required for estimating critical COD value from the simple V charpy test results. In this paper, the high tensile strength steel AH36 plate specimens having a single edge cracked notch were investigated to find out the correlation between V charpy absorbed energy and critical COD value in the welded parts under such various welding methods as shielded metal arc welding, the submerged arc welding and the electro gas welding by means of V charpy impact test and static 3-point bending test. Main results obtained are as follow ; 1. The relationships between V charpy absorbed energy Wc' and critical COD value ($\delta_c$)show; $\delta_c$=0.0065 Wc'+0.1906. 2. Ductile- brittle transition behaviours can be estimated by means of fracture appearance and general yielding behaviours. 3. The V charpy absorbed energy of SMAW is higher than that of SAW, EGW and similar relationships are obtained in the COD tests.

• 대한건축학회논문집:구조계
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• 제34권1호
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• pp.11-18
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• 2018

An experimental study on the ultimate behaviors of the mild carbon steel (SPHC) fillet-welded connection is presented in this paper. Seven specimens were fabricated by the shielded metal arc welding (SMAW). All specimens failed by typical block shear fracture in the base metal of welded connections not weld metal. Block shear fracture observed in the base metal of welded connection is a combination of single tensile fracture transverse to the loading direction and two shear fractures longitudinal to the loading direction. Test strengths were compared with strength predictions by the current design equations and suggested equations by previous researchers. It is known that current design specifications (AISC2010 and KBC2016) and Oosterhof & Driver's equation underestimated overly the ultimate strength of the welded connection by on average 44%, 31%, respectively and prediction by Topkaya's equation was the closest to the test results. Consequently, modified equation is required to be proposed considering the stress triaxiality effect and material property difference on the block shear strength for base metal fracture in welded connections fabricated with mild carbon steel.

• Nuclear Engineering and Technology
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• 제50권1호
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• pp.116-125
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• 2018

Modified 9Cr-1Mo ferritic steel is a preferred material for steam generators in nuclear power plants for their creep strength and good corrosion resistance. Austenitic stainless steels, such as type 316LN, are used in the high temperature segments such as reactor pressure vessels and primary piping systems. So, the dissimilar joints between these materials are inevitable. In this investigation, dissimilar joints were fabricated by the Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. The notch tensile properties and Charpy V-notch impact toughness properties of various regions of dissimilar metal weld joints (DMWJs) were evaluated as per the standards. The microhardness distribution across the DMWJs was recorded. Microstructural features of different regions were characterized by optical and scanning electron microscopy. Inhomogeneous notch tensile properties were observed across the DMWJs. Impact toughness values of various regions of the DMWJs were slightly higher than the prescribed value. Formation of a carbon-enriched hard zone at the interface between the ferritic steel and the buttering material enhanced the notch tensile properties of the heat-affected-zone (HAZ) of P91. The complex microstructure developed at the interfaces of the DMWJs was the reason for inhomogeneous mechanical properties.

• 한국해양공학회지
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• 제22권3호
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• pp.82-88
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• 2008

The diesel engine of the merchant ship has been aperated in severe environments more and more, because the temperature of the exhaust gas of a combustion chamber is getting higher and higher with increasing use of heavy oil of law quality, due to the significant increase in the price of oil in recent some years. As a result, the degree of wear and corrosion between exhaust valve and seat ring is more serious compared to other engine parts. Thus the repair welding of exhaust valve and seat ring is a unique method to prolong the life of the exhaust valve, from an economical point of view. In this study, the corrosion property of both weld metal and base metal was investigated using electrochemical methods such as measurement of corrosion potential, cathodic and anodic polarization curves, cyclic voltammogram, and polarization resistance in 5% H2SO4 solution. The test specimen was a part of an exhaust valve stem being welded as the base metal, using various welding methods. In all cases, the corrosion resistance as well as hardness of the weld metal zone was superior to the base metal. In particular, plasma welding showed relatively good properties for both corrosion resistance and hardness, compared to other welding methods. In the case of DC SMAW (Shielded metal arc welding), corrosion resistance of the weld metal zone was better than that of the base metal, although its hardness was almost same as the base metal.