Toughening mechanism of inter-critical heat-affected zone in a 690 MPa grade rack plate steel

Tong, Min; Di, Xinjie; Li, Chengning; Wang, Dongpo

doi:10.1016/j.matchar.2018.08.021

Cited by 23 publications

(11 citation statements)

References 42 publications

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“…The EDS spectra results in Figure 5(d) show that the carbon is significantly enriched on the precipitated particles, and the concentration reaches 15.75% (wt-%), which is much higher than that of GB ferrite and M-A constituent. According to the above results, considering that the iron content of these particles is high and the morphology is polygonal ( ∼ 81 nm), which is similar to the cementite we observed previously in ICHAZ [28], so these iron-carbon particles are determined to belong to a type of cementite. Liang et al also observed the precipitation of similar polygonal iron-carbon particles in high-strength steels [29].…”

Section: Microstructure Characterisations Of Cghazsupporting

confidence: 83%

“…Figures 11(a) and 11(b) are the Kernel Average Misorientation (KAM) maps of CGHAZ, and different colour regions represent the local average misorientation obtained by the EBSD test. The KAM value is the average misorientation between a given point and all surrounding adjacent points, which is an important indicator reflecting the geometrically necessary dislocations (GND) and the degree of local strain concentration, the higher KAM value means a higher dislocation density and local strain concentration [28,[33][34][35]. Figures 11(c) and 11(d) show the distribution of KAM values of 0°-5°, and the average KAM values of simulated CGHAZ and Post-heat CGHAZ are 1.09°and 1.34°, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

Yang

et al. 2023

Materials Science and Technology

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To clarify the effect of post-heat treatment on the microstructure and mechanical properties of the coarse-grained heat-affected zone (CGHAZ) for EH47 steel, simulated CGHAZ specimens were subjected to post-heat treatment at 250°C for 1.0 h. The results showed that the microstructure of CGHAZ was composed of granular bainite (GB) and lath bainite (LB), and a large number of iron-carbon particles (∼81 nm) were precipitated after post-heat treatment. The relationship between dislocations, low-angle grain boundaries and iron-carbon particles was revealed by KAM values. The iron-carbon particles hindered the movement of sub-grain boundaries and dislocations, thereby increased the yield strength (∼120 MPa). The precipitation of iron-carbon particles caused the cracking of bainite ferrite and reducing the fracture toughness of CGHAZ.

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Section: Microstructure Characterisations Of Cghazsupporting

confidence: 83%

Section: Discussionmentioning

confidence: 99%

Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

Yang

et al. 2023

Materials Science and Technology

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“…In addition, the performance of ICHAZ has been rarely reported. Despite its proximity to the BM in the HAZ, the properties of the ICHAZ can differ from those of the BM 25 . An extension of the fatigue crack at the welded joint of the pipeline would also pass through the ICHAZ 23 ; therefore, the ICHAZ performance in an X80 pipeline should also be studied.…”

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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“…The coarse bainite located in the CGHAZ area had a large crystallographic effective size, which increased the linear propagation path of the cleavage cracks, and undoubtedly impaired the fracture toughness [ 20 , 21 ]. At the same time, no plastic deformation occurred at the fatigue crack tips, and the major crack extended along the coarse PAGBs [ 22 ]. Furthermore, secondary cracks were found at the board of bainite matrix and M-A constituents, which seriously deteriorated the fracture toughness as well.…”

Section: Resultsmentioning

confidence: 99%

Comparison of Fracture Toughness in the Coarse-Grain Heat-Affected Zone of X80 Pipelines Girth-Welded under Conventional and Ultra-Low Heat Input

Liu

et al. 2022

Materials

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The coarse-grain heat-affected zones (CGHAZs) of X80 girth-welded steel pipelines are prone to embrittlement, which has an extremely adverse effect on their structural integrity. In the present work, the fracture behavior of the CGHAZs of X80 girth welds under the conditions of conventional and ultra-low heat input was studied. The fracture toughness of CGHAZs was evaluated using the crack tip opening displacement (CTOD) test at −10 °C, and the fracture behavior mechanism of CGHAZs were clarified by analyzing microstructural characteristics at prefabricated fatigue cracks containing fracture cloud image, scanning electron microscopy (SEM), and electron back-scatter diffraction (EBSD) figures. The results illustrate that the average fracture toughness (CTOD) value of the ultra-low heat input CGHAZ is 0.6 mm, and the dispersion of CTOD values is small, while the CTOD value of conventional heat input is only 0.04 mm. The ultra-low heat input makes the high-temperature residence time of the coarse-grained region short, reduces the proportion of prior austenite grain boundaries, and inhibits the formation of strip-like bainite and island-like M-A components. The reduction of these deleterious ductile microstructures increases the plastic reserve and deformation capacity of the CGHAZ.

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Toughening mechanism of inter-critical heat-affected zone in a 690 MPa grade rack plate steel

Cited by 23 publications

References 42 publications

Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

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

Comparison of Fracture Toughness in the Coarse-Grain Heat-Affected Zone of X80 Pipelines Girth-Welded under Conventional and Ultra-Low Heat Input

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Toughening mechanism of inter-critical heat-affected zone in a 690 MPa grade rack plate steel

Cited by 23 publications

References 42 publications

Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

Effect of post-heat treatment on microstructure and properties of EH47 steel CGHAZ

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

Comparison of Fracture Toughness in the Coarse-Grain Heat-Affected Zone of X80 Pipelines Girth-Welded under Conventional and Ultra-Low Heat Input

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Toughening mechanism of inter-critical heat-affected zone in a 690 MPa grade rack plate steel