Toughness Evaluation on Seam Weld HAZ of High Strength UOE Linepipe

Ishikawa, Nobuyuki; Shinmiya, Toyohisa; Igi, Satoshi; Kondo, Joe

doi:10.1115/ipc2006-10245

Cited by 6 publications

(6 citation statements)

References 8 publications

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“…23, [16]) to show that the coarse-grained heat-affected zone in 9% nickel steel exhibits identical toughness for niobium-containing and niobium-free alloys. In contrast to the work described above, Ishikawa et al [20] present data showing how the fracture-assessed transition temperature increases with niobium additions, claiming that the deterioration in toughness is a consequence of the greater quantity of MA associated with niobium. Remarkably however, they do not present any evidence that niobium increases the fraction of MA; the paper does not include any microstructural characterisation as a function of the niobium concentration.…”

Section: Other Considerationsmentioning

confidence: 80%

Local Brittle Zones and the Role of Niobium

Bhadeshia

2014

MSF

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Abstract. There is a confused and contradictory literature on the role of small concentrations of niobium on the development of the so-called local brittle zones in steels. These zones consist of a mixture of martensite and austenite and hence, their formation should be predictable using modern microstructure calculation methods. Following an assessment of the most relevant literature, a mathematical model is presented which enables three quantities to be calculated, the fraction of martensite, the carbon concentration of the martensite, and its ability to influence toughness. Examples are presented for particular linepipe steels, and then the generic effect of alloying elements other than niobium, on the development of local zones. The Local Brittle Zone as an EntityLocal brittle zones (LBZs) are small regions of hard, brittle phase that form in the heat affected zones (HAZs) of multipass welds [1]. They usually contain untempered martensite that can lead to scatter in toughness data when the test specimen samples a brittle zone [2]. Such scatter reduces confidence in design because of the existence of a few poor values which fall out of the desired range. Experimental data have been interpreted to conclude that the lower bound toughness values deteriorate as the volume fraction of martensite in the form of LBZs increases [3]. However, the same data can be interpreted to indicate that there is a minimum in the toughness as a function of increasing fraction of martensite [4]. Local brittle zones are often treated without a consideration of their detailed microstructure but to make rational assessments it is necessary to address the following questions in a quantitative manner:1. How hard does a LBZ have to be in order to influence scatter in toughness? Or is it the hardness relative to the surrounding material that influences its ability to act as a brittle zone?2. How big does a LBZ have to be in order to matter, relative to the size of the plastic zone in the test used to determine toughness?3. Does the shape of the LBZ matter?4. How many tests are required in order to establish a probability of failure based design?Given these unknowns, it is not surprising that the critique by Liessem and Erdelen-Peppler [5] fails to resolve the fourth query in this list, other than to suggest a change in specification that would allow repeated testing of rejected pipes until the specification is met. The practical problem is that all pipes contain LBZs when longitudinally welded, and it is luck that determines whether the small-scale tests hit an LBZ. The real issue should include a specification of an acceptable level of risk, and probabilistic testing to see whether the material and process combination manages that risk. The generation of probabilistic data is of course, expensive. Martensite/Austenite ConstituentThe martensite-austenite (MA) constituent is a rather clumsy name given to what is essentially a mixture of untempered martensite embedded in carbon-enriched retained austenite. When

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Section: Other Considerationsmentioning

confidence: 80%

Local Brittle Zones and the Role of Niobium

Bhadeshia

2014

MSF

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“…This requires the exact analysis of these low‐toughness regions to demonstrate the probable influence of such defects on structural integrity and continuous performance of the pipe. The issue of defect size (length and depth), defect location (fusion zone, FZ or HAZ) and the effect of low‐toughness HAZ weld on the fitness for service of the pipe as a structure has received great attention in recent years 2–6 . Considerable research on the properties of low and high grades pipeline steels and their welding techniques and characteristics have been carried out 7,8 .…”

Section: Introductionmentioning

confidence: 99%

“…The issue of defect size (length and depth), defect location (fusion zone, FZ or HAZ) and the effect of lowtoughness HAZ weld on the fitness for service of the pipe as a structure has received great attention in recent years. [2][3][4][5][6] Considerable research on the properties of low and high grades pipeline steels and their welding techniques and characteristics have been carried out. 7,8 On one hand, full-scale pipeline burst experiments provide fracture data from real structure under its design pressure and temperature.…”

Section: Introductionmentioning

confidence: 99%

On the relation of microstructure and impact toughness characteristics of DSAW steel of grade API X70

Hashemi

Mohammadyani

Pouranvari

et al. 2009

Fatigue Fract Eng Mat Struct

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A B S T R A C T In this research, mechanical characteristics of double submerged arc-welded line pipe steel of grade API X70 (70ksi yield strength) were investigated. Different experimental examinations including chemical analysis, microstructural investigation, microhardness, tensile and Charpy tests and standard fractography were carried out on different zones of test material. Impact properties of the fusion zone, the heat-affected zone (HAZ) and the base metal were measured on an instrumented Charpy rig and correlated then to their microstructural features. The experimental results showed that the base metal was the toughest, and fusion zone was the least tough region with average Charpy energy of 222 and 128 J, respectively. The latter fulfilled service requirements set by API 5L, despite its relatively low impact energy. Interestingly, the cast microstructure and presence of grain boundary phases such as proeutectoid ferrite in fusion zone confirmed its low energy characteristics. Reduction in HAZ impact energy (compared to base metal) was observed too, together with grain coarsening and the associated HAZ softening adjacent to the weld.

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“…Além da formação de ZFL, existem outros fatores que contribuem negativamente para a diminuição da tenacidade da região de grãos grosseiros da ZTA. Por exemplo, o aumento significativo do tamanho de grão austenítico durante o aquecimento num processo de soldagem pode dar origem a microestruturas finais de baixa tenacidade (Hamad et al, 2008;Ishikawa et al, 2006;Eroglu e Aksoy, 2000;Wu e Davis, 2004).…”

Section: Maurício De Carvalho Silvaunclassified

“…Dependendo da taxa de resfriamento após o processo de soldagem, pode-se obter uma microestrutura martensítica. Os autoresHamad et al (2008),Ishikawa et al, (2006),Eroglu e Aksoy (2000) e Wu e Davis(2004) também relatam em seus trabalhos a influência do tamanho de grão austenítico sobre a tenacidade de aços ARBL soldados. Particularmente,Hamad et al (2008) verificaram ao estudar uma junta soldada de aço API 5L X80 que a condição de soldagem que proporcionou a menor tenacidade foi àquela com maior tamanho de grão austenítico.…”

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Determinação experimental da tenacidade à fratura da zona termicamente afetada de junta soldada de aço API 5L X80.

Silva¹

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Este trabalho investiga a possível correlação existente entre os baixos valores de CTOD e a ocorrência de zonas frágeis localizadas (ZFL) presentes na região de grãos grosseiros (RGG) da zona termicamente afetada (ZTA) de uma junta soldada de aço API 5L X80. Para isto, foi necessário obter corpos-de-prova SE(B) a partir de uma chapa de aço API 5L X80 a qual foi soldada numa junta ½V, para facilitar o posicionamento do entalhe na RGG da ZTA. As dimensões dos corpos-de-prova SE(B) utilizados foram espessura B=17mm, largura W=34mm, distância entre os apoios dos roletes S=138mm e uma relação entre o tamanho de trinca (a) e a largura, a/W=0,5. O entalhe posicionado na RGG da ZTA tem por objetivo evidenciar o efeito de ZFL e para tal os ensaios foram conduzidos nas temperaturas de-40ºC,-50ºC e-70ºC. Os resultados de CTOD crítico obtidos neste estudo sugerem indícios de severa degradação da tenacidade na RGG da ZTA, provavelmente associada à formação de ZFL.

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Toughness Evaluation on Seam Weld HAZ of High Strength UOE Linepipe

Cited by 6 publications

References 8 publications

Local Brittle Zones and the Role of Niobium

Local Brittle Zones and the Role of Niobium

On the relation of microstructure and impact toughness characteristics of DSAW steel of grade API X70

Determinação experimental da tenacidade à fratura da zona termicamente afetada de junta soldada de aço API 5L X80.

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