• Title/Summary/Keyword: Dissimilar Metal Welds

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Determination of Focal Laws for Ultrasonic Phased Array Testing of Dissimilar Metal Welds

  • Jing, Ye;Kim, Hak-Joon;Song, Sung-Jin;Song, Myung-Ho;Kang, Suk-Chull;Kang, Sung-Sik;Kim, Kyung-Cho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.5
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    • pp.427-435
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    • 2008
  • Inspection of dissimilar metal welds using phased array ultrasound is not easy at all, because crystalline structure of dissimilar metal welds cause deviation and splitting of the ultrasonic beams. Thus, in order to have focusing and/or steering phased array beams in dissimilar metal welds, proper time delays should be determined by ray tracing. In this paper, we proposed an effective approach to solve this difficult problem. Specifically, we modify the Oglivy's model parameters to describe the crystalline structure of real dissimilar metal welds in a fabricated specimen. And then, we calculate the proper time delay and incident angle of linear phased array transducer in the anisotropic and inhomogeneous material for focusing and/or steering phased array ultrasonic beams on the desired position.

Dissimilar Metal Welding of SM45C and STS304 by means of CW Nd:YAG Laser (CW Nd:YAG 레이저를 이용한 SM45C와 STS304의 이종금속용접)

  • 신호준;유영태;임기건;안동규
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.1369-1375
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    • 2004
  • For many years and primarily for economical reasons, Dissimilar Metal Welds have been used as transition joints in a variety of equipment and applications. But Dissimilar Metal Welds have several fabrication and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Laser welding techniques have been characterised for various materials. In this paper, the laser weldability of STS304 stainless steel and SM45C at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested

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Welding characteristics of Dissimilar Metal by High Power Laser (고출력 레이저에 의한 이종금속 용접특성)

  • 신호준;유영태;임기건;안동규
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2004.10a
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    • pp.250-256
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    • 2004
  • For many years and primarily for economical reasons, Dissimilar Metal Welds have been used as transition joints in a variety of equipment and applications. But Dissimilar Metal Welds have several fabrication and metallurgical drawbacks that can often lead to in-service failures. In this paper, the laser weldability of STS304 stainless steel and SM45C at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested.

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Generic Procedure Development for the Ultrasonic Examination of Dissimilar Metal Welds in Nuclear Power Plants (원전 이종금속 용접부 초음파 검사 일반 절차서 개발)

  • Yang, Seung Han;Kim, Yong Sik;Yoon, Byung Sik;Guon, Kee Il
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.6 no.1
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    • pp.23-28
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    • 2010
  • To enhance the reliability of ultrasonic testing system, MOST(Ministry of Science and Technology) bulletin 2004-13 was published in 2004.6 requiring performance demonstration in ultrasonic examination and MEST(Ministry of Education, Science and Technology) 2009-37 was published in 2009.9(formerly MOST bulletin 2004-13). In order to meet the MEST bulletin requirement and increase the reliability of ultrasonic testing, all the ultrasonic examination procedure and equipment should be performance demonstrated and qualified. In this paper, generic procedure for the ultrasonic examination of dissimilar metal welds are described and new technique are introduced.

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The Study on the Migration of Carbon in T23/T91 Dissimilar Metal Welds for Boiler (보일러용 T23/T91 이종용접부의 탄소이동에 관한 연구)

  • Park, Ki-Duck;Jung, Byong-Ho;Kang, Chang-Yong
    • Journal of the Korean Society for Heat Treatment
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    • v.27 no.6
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    • pp.288-294
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    • 2014
  • The study on the migration of carbon in T23/T91 dissimilar metal welds for the boiler was conducted at $600^{\circ}C$ with an increase of aging time from 1 to 100 hrs. Following results were obtained. The heavily etched dark band tended to increase from a molten boundary owing to an increase of aging time, which leads to form hard (T91) and soft (T23) zones with different hardness. It was found that carbon was migrated from T23 area to T91 area due to different carbon activities. In addition, soft and hard zones were formed in regional area mainly resulted from carbide dissolutions and precipitates.

Dissimilar Metal Welding of Austenite Stainless Steel and Low Carbon Steel using CW Nd:YAG Laser (CW Nd:YAG 레이저를 이용한 저 탄소강과 오스테나이트계 스테인레스강의 이종금속 용접)

  • Yoo Young Tae;Shin Ho Jun;Ahn Dong-Gyu;Im Kiegon
    • Journal of the Korean Society for Precision Engineering
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    • v.22 no.8 s.173
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    • pp.17-26
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    • 2005
  • Dissimilar-metal welds(DHWs) are used widely in various industrial applications due to the pratical importance from the technical and economic aspect. However, DMWs have several fabricative and metallurgical drawbacks that can often lead to in-service failures. For example, the most pronounced fabrication faults are hot cracks. Recently, DMWs have used the various of heat source to decrease such as faults. In this paper, the weldability on dissimilar metal welds of Austenite stainless steel and Low carbon steel using a continuous wave Nd:YAG laser was experimentally investigated. Experiments were conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser.

Feasibility Study of Flexible Phased Array Ultrasonic Technology Using Irregular Surface Specimen (불규칙 표면 시편을 이용한 Flexible 위상배열초음파기술 적용 연구)

  • Lee, Seung-Pyo;Moon, Yong-Sig;Jung, Nam-Du
    • Journal of the Korean Society for Nondestructive Testing
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    • v.35 no.1
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    • pp.52-60
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    • 2015
  • Nuclear power plant contain many dissimilar metal welds that connect carbon steel components with stainless steel pipes using alloy600 welding materials. Primary water stress corrosion cracks at dissimilar metal welds have been continuously reported around the world. In periodic integrity evaluations, dissimilar metal welds are examined using a generic ultrasonic testing procedure, KPD-UT-10. In this procedure, the gap between the probe and examination surface is limited to 1/32 inch (0.8mm). It is not easy to test some dissimilar metal welds in Korean plants applying ordinary technology because of their tapered shapes and irregular surface conditions. This paper introduces a method for applying a flexible phased array technology to improve the reliability of ultrasonic testing results for various shapes and surface conditions. The artificial flaws in specimens with irregular surfaces were completely detected using the flexible phased array ultrasonic technology. Therefore, it can be said that the technology is applicable to field examination.

Investigation on the Effects of Preventive Maintenance Schemes for Dissimilar Metal Welds on the Residual Stress Distribution (이종금속용접부 예방정비 방법에 따른 잔류응력 분포 고찰)

  • Song, Tae-Kwang;Choi, Young Hwan;Park, Jeong Soon;Chung, Hae-Dong;Oh, Chang-Young
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.7 no.4
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    • pp.1-11
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    • 2011
  • This paper presents the effects of preventive maintenance schemes on the residual stress distributions in dissimilar metal welds. Dissimilar metal weld is known susceptible to PWSCC and thus, effective maintenance schemes to prevent PWSCC are needed. Three preventive maintenances schemes, i.e. weld overlay, MSIP and inlay weld which are widely used in nuclear power plants, are selected and their effects on welding residual stresses are investigated via finite element analyses. As results, weld overlay and MSIP were proved effective method to mitigate residual stresses and inlay weld, on the other hand, produces strong tensile residual stresses in the inner surface. Although Alloy 690 known to be resistant to PWSCC are used in inlay weld, continuous careful observation are needed since tensile welding residual stresses are key parameter for PWSCC.

Simulation Based Investigation of Focusing Phased Array Ultrasound in Dissimilar Metal Welds

  • Kim, Hun-Hee;Kim, Hak-Joon;Song, Sung-Jin;Kim, Kyung-Cho;Kim, Yong-Buem
    • Nuclear Engineering and Technology
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    • v.48 no.1
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    • pp.228-235
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    • 2016
  • Flaws at dissimilar metal welds (DMWs), such as reactor coolant systems components, Control Rod Drive Mechanism (CRDM), Bottom Mounted Instrumentation (BMI) etc., in nuclear power plants have been found. Notably, primary water stress corrosion cracking (PWSCC) in the DMWs could cause significant reliability problems at nuclear power plants. Therefore, phased array ultrasound is widely used for inspecting surface break cracks and stress corrosion cracks in DMWs. However, inspection of DMWs using phased array ultrasound has a relatively low probability of detection of cracks, because the crystalline structure of welds causes distortion and splitting of the ultrasonic beams which propagates anisotropic medium. Therefore, advanced evaluation techniques of phased array ultrasound are needed for improvement in the probability of detection of flaws in DMWs. Thus, in this study, an investigation of focusing and steering phased array ultrasound in DMWs was carried out using a time reversal technique, and an adaptive focusing technique based on finite element method (FEM) simulation. Also, evaluation of focusing performance of three different focusing techniques was performed by comparing amplitude of phased array ultrasonic signals scattered from the targeted flaw with three different time delays.

Evaluation of Mechanical Properties in Inconel 82/182 Dissimilar Metal Welds (인코넬 82/182 이종금속 용접부의 기계물성 평가)

  • Lee, Joung-Hoon;Jang, Chang-Heui;Kim, Jong-Sung;Jin, Tae-Eun
    • Proceedings of the KSME Conference
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    • 2007.05a
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    • pp.244-249
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    • 2007
  • In several locations of the pressurized water reactors, dissimilar metal welds using inconel welding wires are used to join the low alloy steel nozzles to stainless steel pipes. To evaluate the integrity and design the dissimilar welds, tensile and fracture properties variations are needed. In this study, dissimilar metal welds composed of SA508 Gr.3 LAS, inconel 82/182 weld, and TP316 stainless steel were prepared by gas tungsten arc welding and shielded metal arc welding technique. Microstructures were observed using optical and electron microscopes. Different tensile and fracture properties were observed depending on the specimen sampling position at room temperature and $320^{\circ}C,$ and that was discussed based on the microstructure characteristics. It was found that the strength at the bottom of weld was greater than at the top of the weld. Also, from the test data using small punch specimen, more detailed tensile property variations were evaluated.

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