• Journal of Welding and Joining
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• v.21 no.6
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• pp.64-70
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• 2003

Multipass welds of the 316L stainless steel have been widely employed in the pipes of Liquid Metal Reactor. Owing to localized heating and subsequent rapid cooling by the welding process, the residual stress arises in the weld of the pipe. In this study, the residual stresses in the 316L stainless steel pipe welds were calculated by the finite element method using ANSYS code. Also, the residual stresses both on the surface and in the interior of the thickness were measured by HRPD(High Resolution Powder Diffractometer) instrumented in HANARO Reactor. The experimental data and the calculated results were compared and the characteristics of the distribution of the residual stress discussed.

• Proceedings of the KWS Conference
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• 1999.10a
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• pp.331-334
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• 1999

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.161-163
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• 2005

• Journal of Welding and Joining
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• v.32 no.5
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• pp.21-25
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• 2014

Oil and gas fields were left unexploited which deemed too deep and sour. New developing markets are emerging in this part and pipe manufacturers need demanding requirements in the combination of sour service requirements with heavier wall thickness required to cope with increasing water depths. Whilst, the strength and fracture toughness needed to meet the strict requirements In order to deliver the optimum sour properties in the final pipe, attention needs to be paid to each stage throughout the process from steel making. The main key during steel making is strengthening, securing mechanical properties and suppression of center segregation by adding proper chemical elements and controlling water cooling and plate rolling. Additionally in welding, it is required to prevent HAZ softening by high heat input during welding of heavy thick pipes and hydrogen assisted cracking in high strength steels with hard phases. In this paper, we introduce markets of sour resistant linepipe steels and in response to this, have a look in the development trend of sour resistant linepipe steels and its sour characteristics in welded joints.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.81-87
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• 2017

The pipe connection process using a clamping ring is used for joining small pipes in the refrigerator and air-conditioner industries instead of the brazing process, which induces inevitable thermal deformation in the pipes. However, few studies have been carried out on the process to select optimal parameters in joining pipes, and studies on the relation between the process parameters of the connection and connecting force of the joint have not been conducted. In this study, the connection process of pipes with the clamping ring was modeled using the finite element method (FEM) and analyzed to obtain the contact stress distribution between the pipes with which the connecting force of the joint was estimated. Considering the characteristics of pipe connection, the process was modeled and simulated in a two-dimensional axisymmetric solution domain. With the numerical model, the effect of ring shape on the connection was studied by adding a projection to the end of a ring or changing the length of a ring. The results of the analyses revealed that the contact stress distribution could be predicted with the suggested model. The effect of the ring shape was also presented. The effect of any combination of process parameters could be easily estimated through the related analyses.

• Journal of Welding and Joining
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• v.16 no.5
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• pp.119-133
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• 1998

To implement full automation in pipe welding, it si most important to develop special sensors and their related systems which act like human operator when detecting irregular groove conditions. In this study, an automatic pipe Gas Metal Arc Welding (GMAW) system was proposed to full control pipe welding procedure with intelligent sensor systems. A five-axes manipulator was proposed for welding torch to automatically access to exact welding position when pipe size and welding angle were given. Pool status and torch position were measured by using a weld-pool image monitoring and processing technique in root-pass welding for weld seam tracking and weld pool control. To overcome the intensive arc light, pool image was captured at the instance of short circuit of welding power loop. Captured image was processed to determine weld pool shape. For weld seam tracking, the relative distance of a torch position from the pool center was calculated in the extracted pool shape to move torch just onto the groove center. To control penetration of root pas, gap was calculated in the extracted pool image, and then weld conditions were controlled for obtaining appropriate penetration. welding speed was determined with a fuzzy logic, and welding current and voltage were determined from a data base to correspond to the gap. For automatic fill-pass welding, the function of human operator of real time weld seam control can be substituted by a sensor system. In this study, an arc sensor system was proposed based on a fuzzy control logic. Using the proposed automatic system, root-pass welding of pipe which had gap variation was assured to be appropriately controlled in welding conditions and in torch position by showing sound welding result and good seam tracking capability. Fill-pass welding by the proposed system also showed very successful result by tracking along the offset welding line without any control of human operator.

• Journal of Welding and Joining
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• v.26 no.4
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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.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.257-259
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• 2003

Sulfide Stress Corrosion Cracking(SSCC) of welded Steel pipe has been investigated. A specimens are stressed into the synthetic sea water saturated with H$_2$S. Therefore SSCC occur at the hardnest point. we are discusses the test methods used for laboratory corrosion testing of welded steel pipe and the results of test.

• Proceedings of the KWS Conference
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• 1997.05a
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• pp.74-77
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• 1997

• Proceedings of the KWS Conference
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• 1998.10a
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• pp.219-222
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• 1998