• Journal of Welding and Joining
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• v.16 no.1
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• pp.25-37
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• 1998

본 해설에서는 Inconel계와 Hastelloy계로 구분되는 9%Ni강용 피복아크용접봉을 중심으로 LNG저장탱크 용접시공시 발생 가능한 문제점들을 검토하고, Ni합금 피복봉의 심선과 피복제와 관련한 일반적인 제조특성을 살펴보았다. 또한 현재 국내 현장에서 용접시공에 사용되는 용접재료의 화학적, 기계적 특성과 함께 용접작업성을 평가한 결과 이들 피복아크용접봉들은 규격이 정한 요구조건들을 만족하면서 비교적 양호한 용접작업성을 확보하고 있는 것으롤 판단되었다. 이상의 검토결과는 향후 9%Ni강용 Ni합금 피복아크용접봉의 국산화 개발에 기초자료로 활용될 것으로 기대된다.

• Journal of Welding and Joining
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• v.2 no.2
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• pp.1-6
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• 1984

피복아아크 용접봉(이하 용접봉이라 함)의 피복제는 염기도에 따라 산성, 중성, 염기성으로 대별할 수 있다. 용접에서의 화학야금반응은 제강의 화학야금반응과 원리는 비슷하나 양자간 크게 다른 점은 용접시의 반응시간이 극히 짧다는 점이다. 이와같이 반응시간이 짧다는 점 이외에도 작업자가 직접 용융반응을 지켜 보면서 반응후에 나타나는 제반 문제점에 대비하여야 하는 어려운 점이 있다. 제강반응은 전문가만의 독특한 기술인 반면 용접은 용접봉 제조자 뿐만 아니라, 용접작업자 고유의 기술이므로 용접야금반응을 상식화 하고자 하는데 본 고는 의의를 두고 있다. 피복제 중에서의 염기도의 변화, 즉 염기도에 영향을 크게 미치는 탄산칼슘의 양을 임의로 변화시키므로서 다음과 같은 현상을 기대할 수 있다. (1)용접 작업성의 변화 (2)용착 금속의 화학성분 변화 (3)용착금속의 조직 변화 (4) 용착금속내의 수소 함유량 변화 (5)용착금속의 기계적 성질변화 등이다.

• Journal of Welding and Joining
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• v.16 no.4
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• pp.125-135
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• 1998

The shielded metal arc welding (SMAW) by AC power source was performed to evaluate the arc stability by arc monitoring and analysing. In this study, the arc stability index was evaluated quantitatively by using he coefficient of resistance variation for welding time. This coefficient was obtained for the long time (20sec.) by analysing the waveforms of welding current, voltage and resistance. The coefficient was applied to indicate numerically the variation level of arc length and the degree of arc extinction. Using the coefficient of resistance variation in practical welding, the arc stability of the high titanium oxide electrode (KS E4313) turned out to be better than that of the low hydrogen electrode (KS E4316). In evaluating the skill level of welders by the coefficient, the horizontal fillet weaving welding became clear to be very discriminating because the higher level welder could weave in keeping constant arc length, but the lower level welder showed the characteristics of weaving with the unstable arc length. And it was confirmed that the welding defects as blow holes was formed when the arc stability index were high.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.8
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• pp.877-885
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• 2013

A seawater pipe of the engine room in the ships is being surrounded with severely corrosive environments caused by fast flowing of the seawater, containing aggressive chloride ion and high conductivity etc.. Therefore, the leakage of the seawater from its pipe have been often occurred due to its local corrosion by aggressive chloride ions. Subsequently, its leakage area is usually welded by AC shielded metal arc welding with various electrodes. In this study, when the sea water pipe is welded with several types of electrodes such as E4301, E4311, E4313 and E4316, a difference of the corrosion resistance on the welding metal zones was investigated using an electrochemical method, observing microstructure, measuring polarization behaviors and hardness. The weld metal zone welded with E4313 electrode exhibited the lowest value of hardness compared to other weld metal zones. In addition, its zone indicated also the best corrosion resistance than those of other weld metal zones. Furthermore, all of the weld metal zones revealed a relatively better corrosion resistance than those of the base metal zones. and also showed higher hardness than the base metal zones.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.358-369
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• 2000

Shielded metal arc welding machines with AC transformer have been widely used for thin-plate welding applications. Because of being bulky, heavy and of tap-changing property, so the SMAW's are changing to new power electronic circuits such as inverter circuit in order to reduce the system size and also to improve the welding performances at input output sides. The PWM inverter arc welding machine with diode rectifier has better output welding performances but it is has the plentiful harmonics and the lower input power factor. To solve these problems, input current-controlled scheme is considered for PWM inverter arc welding system, and then total input power factor is maintained to be more than 99%. Also a new combined control is proposed which can control both instantaeous welding output voltage and current under constant power condition, and as a result the variations of instantaneous current and voltage can be reduced to very narrow range in the V-I curve relationship, and hence the variance of welding current and voltage become so reduced. In addition the spatter generated during welding process is greatly reduced up to 70%. And the overall effiency can be improved up to 10%, which becomes higher when the load is lower.

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.68-70
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• 1998

• Proceedings of the KWS Conference
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• v.43
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• pp.112-114
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• 2004

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.64-66
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• 2000

• Journal of Welding and Joining
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• v.12 no.4
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• pp.41-49
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• 1994

This study is to compare the welding quality of API 5L-X65 Steel- pipe's for natural gas transmission piping applied by SAW at shop and by GTAW-SMAW at site. The results can be summarized as follows; 1) Tensile strength of the welded zone by SAW(611.5 MPa) and by GTAW-SMAW(608.6 MPa) was maintained greater than that of the base metal(583.5 MPa). 2) Hardness of the welded zone and HAZ by SAW(Hv 194.8) & GTAW-SMAW (Hv 196.1) was slightly increased above that of the base metal (Hv 168.8), but less than the maximum allowable hardness(Hv 248). 3) Impact value of the welded zone by SAW(126.8 J) & GTAW-SMAW(88 J) became lower than that of the base metal(282.5 J), but was above the requirement of API 5L(68J). 4) Microscopic structure of the welded zone and HAZ by both SAW & GTAW-SMAW became fine-grained.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.75-85
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• 1996

In this paper the influence of postweld heat treatment on mechanical properties of SMAW and FCAW stainless steel weldments was examined and the obtained results are as follows ; (1) The amount of $\delta$-ferrite formed by SMAW and FCAW process decreased with increasing holding temperature and time in post weld heat treatment(PWHT), and it was found that the reduced ferrite was transformed into sigma phase after $800^{circ}C{\times}50hr$ PWHT. This sigma phase, even though it was very small, resulted in brittleness of dissimilar weldment between carbon steel and stainless steel in bending test, however in similar weldment between stainless steel and stainless steel was not occured. (2) The chemical composition of sigma phase was measured to 28-30%Cr, 7-9%Mo, 4-6Ni in 316L weldment, and also 35-37%Cr, 0.9-1.0Mo, 6-8%Ni in 309L weldment by EDS analysis.