• Journal of Welding and Joining
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• 제22권5호
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• pp.58-64
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• 2004

Although leakage at a low carbon steel pipe made by electrical resistance welding (ERW) was reported due to grooving corrosion, the cause for the corrosion has not yet been cleared. In order to clarify the main cause, failure analysis on the leaked pipe was carried out, followed by metallographic investigation and corrosion test for the various ERW pipe made with different welding heat input. The microstructure, particularly inclusion content, of the weldment is dependant on the welding heat input applied. For an improper low heat input, the amount of inclusion at the weld was high. High inclusion content accelerated grooving corrosion at the weld. It is therefore that welding heat input should be controlled based on the carbon content of the pipe in order to improve the corrosion resistance of the ERW pipe.

• Journal of Welding and Joining
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• 제26권4호
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• pp.85-91
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• 2008

The grooving corrosion is caused mainly by the different microstructures between the matrix and weld which is formed during the rapid heating and cooling cycle in welding. By this localized corrosion reaction of pipes, it evolves economic problems such as the early damage of industrial facilities and pipe lines of apartment, and water pollution. So lots of researches were carried out already about grooving corrosion mechanism of ERW carbon steel pipe but there is seldom study for water hammer happened by fluid phenomenon and corrosion rate by flow velocity. In this study, the analysis based on hydrodynamic and fracture mechanics was carried out. ANSYS, FLUENT and STAR-CD were used for confirmation of flow phenomenon and stress on the pipe. As the results, fatigue failure is able to be happened by water hammer and grooving corrosion rate is increased cause by turbulent. Grooving corrosion is happened on the pipe, then friction loss of fluid is occurred from corroded part. Erosion can be happened enough in corroded region of microscopic size that wear "V" form. Also pipe is able to be damaged by water hammer effects because of corroded region is general acting as a notch effects. Corrosion depth was more than half of total thickness, it can be damaged from water hammer pressure.

• 동력기계공학회지
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• 제11권3호
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• pp.41-46
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• 2007

The microstructure and electrochemical analysis of welds of electric resistance welding(ERW) pipe were investigated. The direction of metal flow line in HAZ of ERW pipe shifted to the inner(or outer) surface of pipe by plastic deformation during welding. The lowest heat input welds of ERW pipe was showed crack by liquid penetrant testing. Accelerated corrosion test by constant current density of 20mA/$cm^{2}$ developed groove at the welds of ERW pipe and the measured grooving factors were about $1.2{\sim}1.5$. Corrosion potential of base metal obtained by cyclic polarization in artificial sea water(3.5wt.% NaCl solution) was 100mV higher than that of weld metal of ERW pipe.

• Corrosion Science and Technology
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• 제17권3호
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• pp.109-115
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• 2018

Electrical Resistance Welding (ERW) on a longitudinal seam-welded pipe has been extensively used in oil and gas pipelines. It is well known that the weld zone commonly suffers from grooving corrosion in ERW pipes. In this paper, the grooving corrosion performances of API X65 grade non-sour service (steel-A) and API X70 grade sour gas resistant (steel-B) steel electrical resistance welding pipelines were evaluated. The microstructure of the bondline is composed of coarse polygonal ferrite grains and several elongated pearlites. The elongated pattern is mainly concentrated in the center of the welded area. The grooving corrosion test and electrochemical polarization test were conducted to study the corrosion behavior of the given materials. A V-shaped corrosion groove was found at the center of the fusion zone in both the steel-A and steel-B ERW pipes, as the corrosion rate of the bondlines is higher than that of the base metal. Furthermore, the higher volume fraction of pearlite at the bondline was responsible for the higher corrosion rate at the bondline of both types of steel.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.1-6
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• 2004

Lots of researches were gone already about grooving corrosion mechanism of ERW carbon steel pipe. But there is seldom study for water hammer happened by fluid and acceleration of corrosion rate by incresed flow velocity. Therefore, in this study carried out the analysis based on hydrodynamic and fracture mechanics. Analyzed stress that act on a pipe using ANSYS as a program, and also FLUENT and STAR-CD were used for flow phenomenon confirmation. As the result, fatigue failure is happened by water hammer and corrosion rate was increased because of turbulent flow.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권3호
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• pp.197-206
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• 2015

Failure analysis of pre-insulated pipe (SPPS 380, 400A) transporting high temperature water ($95{\sim}110^{\circ}C$) for a plant was carried out. The damaged area (${\Phi}5mm$) of pre-insulated pipe was found only on welds. The chemical composition of damaged pipe meets specification of carbon steel pipes for pressure service (KS D 3562). As results of microstructure analysis, crack propagated from outer to inside after pitting corrosion occurred on the outside surface. The non-metallic inclusion existed on the end of crack. And the non-metallic inclusion continuously and linearly formed along with the bond line of welds. Based on SEM-EDS analysis, the nonmetallic inclusions have higher Manganese (Mn) and Oxygen (O) content but sulfur (S) was not detected. As results of water quality analysis, hydrogen ion concentration and minerals like Fe, Mg, Si were in low level. But the content of dissolved oxygen (11.2 ppm) was slightly higher than that of standard. It seems that the cause of damaged pipe is grooving corrosion due to MnO inclusion formed on bond line and corrosion took place nearby welds.

• Corrosion Science and Technology
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• 제3권2호
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• pp.67-71
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• 2004

Galvanized Steel pipes have been widely used in industries and apartments, Unexpected early leakage has been found in an apartment. Tunneling corrosion or penetration was found in the water supply pipes. The chemical compositions of the pipes and properties of coating layer were evaluated. The pipes met the specification of KS D 3507. The cause of early failure was analyzed through the examination of macrostructures and microstructures, It was found that the pipes were failed by grooving corrosion, which resulted from galvanic corrosion of weld bead and matrix.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.82-82
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• 2009

강관은 물, 유류, 천연 가스 등을 운송하는 배관용 및 건물의 골조, 유압 및 공압 실린더, 가이드 레일 등 의 기계적 부품으로도 널리 사용되기도 한다. 이렇게 사용되는 강관의 70% 이상은 고주파 전기저항용접(High Frequency Electrical Resistance Welding,이하 ERW)으로 제조되고 있다. 아파트 등 실제 현장에서 ERW 강관에 흐르는 유체는 비드가 제거된 내면 부위에서 와류 (vortex)를 일으켜 기계적 침식(erosion)을 수반할 가능성이 있으며, 수격현상으로 인해 부식 부위에서 반복피로 하중을 받아 부식의 전파속도가 증가되어 최종적 으로 파손되는 경우도 예상할 수 있다. 이에 본 연구에서는 입열량을 달리하여 제조된 ERW 강관을 대상으로 강관 내부에서의 유속에 따라 홈부식 감수성에 미치는 영향을 확인하고자 하였다. 이를 위해 실제 사용 환경을 모사할 수 있는 장치를 제작하고 경계 조건을 선정하여 실험을 실시하였다. ERW 강관의 내부에서 유속이 빨라질 경우 부식속도는 증가를 하였고, 입열을 많이 받은 강관의 경우 부식속도가 감소하는 경향을 가졌다. 이러한 결과를 바탕으로 하여 ERW 강관에서 발생하고 있는 결함발생에 의한 피해를 극소화시킴으로서 안전하고 효율적인 관리에 기여하고자 한다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1990년도 특별강연 및 추계학술발표 개요집
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• pp.87-90
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• 1990

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2004년도 추계학술발표대회 개요집
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• pp.269-271
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• 2004