Correlation of rolling condition, microstructure, and low-temperature toughness of X70 pipeline steels

Hwang, Byoungchul; Lee, Sunghak; Kim, Young Min; Kim, Nack J.; Yoo, Jae‐Young

doi:10.1007/s11661-005-0043-1

Cited by 50 publications

(30 citation statements)

References 21 publications

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“…[3][4][5][6][7][8][9][10][11][12][13][14][15] In the present study, the DBTT was interpreted from the perspectives of grain boundary orientation characteristics and effective grain size by adding EBSD analysis to the results of the cleavage crack propagation path and the cleavage fracture unit in order to identify the microstructural roles of effective grain size in the DBTT variations.…”

Section: Discussionmentioning

confidence: 99%

“…Because material inhomogeneity becomes more serious in the C specimens because of a longer cooling interval than in the B specimens, the USE and DBTT tend to scatter more widely. According to currently available reports on the effects of microstructure on the USE of low-carbon steels, [3][4][5][6][7][8][9][10][11][12]25] PF base structure shows the highest USE of 300 to 500 J, while AF base and bainite base structures show a USE of 300 to 400 J and 150 to 300 J, respectively, which indicates that phases transformed at lower temperatures have the lower USE. However, the C specimens composed of AF and PF show rather higher USE than the A and B specimens having PF matrix.…”

Section: Charpy Impact Propertiesmentioning

confidence: 99%

“…It is generally known that the absorption energy and strength depend on microstructural factors such as type, volume fraction, and morphology of secondary phases, reinforcing phases, grain size, and matrix microstructure, and that DBTT primarily relies on the distance between grain boundaries, i.e., effective grain size, which work as a barrier against the cleavage crack propagation. [3][4][5][6][7][8][9][10][11][12][13] The effective grain size of ferrite-pearlite steels is identified as ferrite grain size; however, those of high-strength acicular ferritic steels, bainitic steels, dual-phase (ferrite-martensite) steels, and complex steels with these microstructures coexisting are still exposed to serious controversies. [12][13][14][15][16][17] Because the increase in strength can be accompanied with deteriorating toughness, systematic understanding of various microstructural factors affecting tensile and Charpy impact properties is needed in order to produce high-strength high-toughness linepipe steels.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

Kim

Shin

Lee

et al. 2007

Metall Mater Trans A

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This study is concerned with the effects of V and Mo addition on tensile and Charpy impact properties of API X70 linepipe steels. Twelve kinds of steel specimens were produced by varying V and Mo additions and rolling conditions. The addition of V and Mo promoted the formation of acicular ferrite (AF), banitic ferrite (BF), and martensite-austenite (MA) constituents, while suppressing the formation of polygonal ferrite (PF) or pearlite (P). The tensile test results indicated that the tensile strength of the specimens rolled in the two-phase region increased with the addition of V and Mo, while the yield strength did not vary much in these specimens except the water-cooled specimens, which showed the increased yield strength with addition of Mo. The tensile strength of specimens rolled in the single-phase region followed by water cooling increased with increasing V and Mo contents. The yield strength, however, did not vary much with increasing V content or with addition of Mo to the low-V alloy. In these specimens, a substantial increase in the strengths was achieved only when Mo was added to the high-V alloy. The specimens rolled in the single-phase region had higher upper-shelf energy (USE) and lower ductile-brittle transition temperature (DBTT) than the specimens rolled in the two-phase region, because their microstructures were composed of AF and fine PF. According to the electron backscatter diffraction (EBSD) analysis data, the effective grain size in AF was determined by crystallographic packets composed of a few fine grains having similar orientations. Thus, the decreased DBTT in the specimens rolled in the single-phase region could be explained by the decrease in the overall effective grain size due to the presence of AF having smaller effective grain size.

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Section: Discussionmentioning

confidence: 99%

Section: Charpy Impact Propertiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

Kim

Shin

Lee

et al. 2007

Metall Mater Trans A

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“…However, the precipitation carbides deteriorate the impact toughness. 31,32) On the basis of the microstructural characteristics of three specimens with different finish rolling temperature, the results of the lowest impact toughness of A940 and the highest impact toughness of A880, can be understood. Moreover, the refined cementite particles and the occurrence of acicular ferrite with relatively small effective grain size at finish rolling temperature 880°C also improve the impact toughness.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Microstructural Characteristics with Various Finish Rolling Temperature and Low Temperature Toughness in Hot Rolled Nb–Ti Ferritic Steel

Ji¹,

Li²,

Tang³

et al. 2016

ISIJ Int.

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“…[11] However, these mechanical properties often display high anisotropy and it is not well understood to which microstructural or crystallographic elements this can be attributed. Mechanical anisotropy has been extensively studied by analyzing the effect of microstructural parameters [4][5][6][7] and by analyzing the effect of texture. [8][9][10] Nevertheless, the effect of texture and microstructure on the anisotropy in the ductileto-brittle transition region (DBTR) is not yet well known.…”

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confidence: 99%

Texture Dependent Mechanical Anisotropy of X80 Pipeline Steel

et al. 2010

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High strength and toughness are the most common requirements for pipeline steels. High strength of the steel contributes to cost reductions of the fuel transportation by decreasing construction, material, and compression costs which increases transportation efficiency. Improvements in strength are generally achieved, though, at the expense of reducing toughness and ductility; but toughness is an imperative property to ensure the structural integrity of the pipeline over a long period of time. [1][2][3][4] Optimized microstructure and texture are necessary to further improve the strength and toughness of pipeline steels. An appropriate design of the chemical composition together with a thermomechanically controlled process (TMCP) contribute to the achievement of effective microstructures and textures, ensuing improved mechanical properties. [6,10] It has been largely reported in the literature that mechanical properties of pipeline steels like yield strength and toughness are strongly affected by thermo-mechanical controlled processing. The properties are mainly dependent on the rolling temperatures, the finish cooling temperature and the cooling rate on the runout table after hot rolling. [11] However, these mechanical properties often display high anisotropy and it is not well understood to which microstructural or crystallographic elements this can be attributed. Mechanical anisotropy has been extensively studied by analyzing the effect of microstructural parameters [4][5][6][7] and by analyzing the effect of texture. [8][9][10] Nevertheless, the effect of texture and microstructure on the anisotropy in the ductileto-brittle transition region (DBTR) is not yet well known.Toughness is most commonly measured by the amount of energy absorbed by a Charpy V-notch specimen during impact testing. Low energy levels are associated with brittle behavior at low temperatures due to cleavage-type fracture. At higher temperatures, high-energy ductile fracture occurs by microvoids coalescence. [12] In numerous studies the low temperature toughness has been linked to microstructural parameters, like the effective grain size represented by the effective free path length available to a moving dislocation. This implies that various types of obstacles such as grain or phase boundaries may act as critical sites of stress concentration and hence can be activated as crack nucleation sites. It is already known that the effective grain size in ferritic steels corresponds to the ferrite grain size [13][14][15] and larger ferrite grains contribute to an increase in the transition temperature and reduction of the impact toughness. [16] However, the effective grain size for acicular ferritic, bainitic, martensitic, or multiphase steels as API steel grades is not wellPipeline steel grades API X80 are used for oil and gas transport. The most important mechanical properties of these steel grades are strength and fracture toughness. A remarkable directional anisotropy of toughness and strength were often observed in the plates. The effect of t...

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Correlation of rolling condition, microstructure, and low-temperature toughness of X70 pipeline steels

Cited by 50 publications

References 21 publications

Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

Effects of Molybdenum and Vanadium Addition on Tensile and Charpy Impact Properties of API X70 Linepipe Steels

Microstructural Characteristics with Various Finish Rolling Temperature and Low Temperature Toughness in Hot Rolled Nb–Ti Ferritic Steel

Texture Dependent Mechanical Anisotropy of X80 Pipeline Steel

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