Microstructure and impact toughness of reheated coarse grain heat affected zones of API X65 and API X80 linepipe steels

Arora, Kanwer Singh; Pandu, Sangeetha Ranga; Shajan, Nikhil; Pathak, Prashant; Shome, Mahadev

doi:10.1016/j.ijpvp.2018.04.004

Cited by 56 publications

(20 citation statements)

References 24 publications

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“…The effect of welding on the microstructure of the HAZ, is characterized by significant changes at different distances from the fusion line ( Figure 5). The original microstructure consisting of ferrite and pearlite, also observed for 3.0 mm from the fusion line (3FL), is modified and lath and granular bainite are observed closer to the fusion line (1FL), which is consistent with other investigations 18,21,[65][66][67] . At 2.0 mm from the fusion line, lower microhardness values (~10%) compared to the base metal are observed, both in the as welded and heat treated conditions.…”

Section: Mechanical Properties and Microstructural Characterizationsupporting

confidence: 91%

“…At 2.0 mm from the fusion line, lower microhardness values (~10%) compared to the base metal are observed, both in the as welded and heat treated conditions. This softening reported by the literature is usual in API X80 steel 14,65,[68][69][70][71][72][73][74] , and is due to the predominance of polygonal ferrite 65,72,73 . However, some works 14,68,74 state that the softening of HAZ may be more serious and a study on high-strength pipeline steel should not only pay attention to the embrittlement but also to the softening of the welding heat affected zone 73 , because the reduction in hardness can be around 10-20% in comparison to the base metal 70 .…”

Section: Mechanical Properties and Microstructural Characterizationmentioning

confidence: 76%

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Investigation into the Impact Toughness of API 5L X80 Steel Weldments and its Relationship with Safe Welding Procedures

et al. 2020

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API 5L X80 steels are widely used in welded pipes in the petroleum industry. However, microstructural changes in the heat affected zone are a concern when welding such pipes due to the potential formation of regions with low toughness. Despite all the research concerning mechanical properties of welded joints, the acceptance criteria for the qualification of welding procedures are still limited. Welded joints do not always guarantee the safe operation of industrial equipment, because the current Standards adopted are not able to evaluate the properties at some critical regions of the welded joint. This work studied the characteristics of a girth welded joint and showed evidences of low toughness at 0.5 mm from the fusion line due to the micro-phases necklacing the prior austenite grain boundaries. As this feature is not considered by the current Standards for approval of welding procedures, this work proposes an alternative approach to improve the safety of welded structures.

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Section: Mechanical Properties and Microstructural Characterizationsupporting

confidence: 91%

Section: Mechanical Properties and Microstructural Characterizationmentioning

confidence: 76%

Investigation into the Impact Toughness of API 5L X80 Steel Weldments and its Relationship with Safe Welding Procedures

et al. 2020

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“…One alternative is to use thermal simulation for each sub-HAZ to assess individual performance. 18,19 Although thermal simulation methods have been widely used to study the microstructure and mechanical properties of the HAZ, 20,21 reports on the fatigue performance of the HAZ mainly focused on the properties of the overall welded joint, 22,23 and little work has been done to investigate the fatigue properties of each sub-HAZ in an X80 pipeline, especially in terms of fatigue crack growth. 24 In addition, the performance of ICHAZ has been rarely reported.…”

Section: Introductionmentioning

confidence: 99%

Research on the fatigue properties of sub‐heat‐affected zones in X80 pipe

Qiao

Wang

et al. 2020

Fatigue Fract Eng Mat Struct

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Pipeline transmission is an essential means of oil and gas transportation, but its safety is threatened by fatigue fracture that generally occurs in the heat-affected zone (HAZ) adjacent to welded joints of the pipeline. Therefore, it is important to determine the fatigue properties of HAZ. In this work, the microstructure and mechanical properties in the HAZ of a X80 pipe were accurately simulated by thermal simulation. The fatigue life and crack growth rate of typical sub-HAZ were tested. The results showed that fine grain HAZ exhibited the lowest strength and fatigue life. In contrast, coarse grain HAZ had the highest strength, but its fatigue life was lower than that of the intercritical HAZ. The microstructure of each sub-HAZ and the effect of this structure on fatigue properties were analysed and discussed in detail. The results provide insight into the effects of microstructure and mechanical properties on the service safety of pipeline transportation.

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“…These regions form adjacent to the weld deposit as a result of being heated to temperatures ≥1200, 900-1200 and 700-900 ∘ C, respectively [20]. In addition, a great deal of researches directed on the toughness of welded parts indicated that FGHAZ and ICHAZ are far more tougher than CGHAZ in welded parts [21,22]. This is due to the formation of prior coarse-grained austenite [23] in the CGHAZ of welded steels, which subsequently transform to plate-like bainitic ferrite matrix associated with some martensite/austenite islands during cooling.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Evolution and Carbon Partitioning in Interstitial Free Weld Simulated API 5L X60 Steel

Zarchi

Khajesarvi

Banadkouki

et al. 2019

Reviews on Advanced Materials Science

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The microstructural characterizations and partitioning of carbon element in the weld heat affected zones of a commercial API 5L X60 line pipe steel were studied by applying a high speed heating and cooling dilatometry technique in the present research work. The hollow cylindrical specimens were quickly heated to 1000°C, soaked for only 5 s followed by continuous cooling to ambient temperature. Besides the construction of CCT diagram of this high strength low alloy steel using the dilatation data, the hardening response, microstructural features and carbon partitioning of weld simulated specimens were investigated. The obtained results showed that the hardening response of samples increased from 142 to 261HV10kg with increasing cooling rates. These hardening variations were attributed to the changes in microstructural features and carbon partitioning that occurred between the microconstituents present in the microstructures of weld simulated samples.

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Microstructure and impact toughness of reheated coarse grain heat affected zones of API X65 and API X80 linepipe steels

Cited by 56 publications

References 24 publications

Investigation into the Impact Toughness of API 5L X80 Steel Weldments and its Relationship with Safe Welding Procedures

Investigation into the Impact Toughness of API 5L X80 Steel Weldments and its Relationship with Safe Welding Procedures

Research on the fatigue properties of sub‐heat‐affected zones in X80 pipe

Microstructural Evolution and Carbon Partitioning in Interstitial Free Weld Simulated API 5L X60 Steel

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