Microstructure of Microalloyed Linepipe Steels

Sharma, Udit; Ivey, Douglas G.

doi:10.1115/ipc2000-125

Cited by 4 publications

(4 citation statements)

References 13 publications

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“…The microstructure observed by optical microscope was characterized by irregular ferrite. Further observation by TEM revealed that, acicular-like microstructure was actually composed of the subgrain within the acicular ferrite structure, and was constituted with nearly parallel lathing ferrites in which orientation margin of adjacent interfaces was small angle [8,9]. The effective grain size of acicular ferrite was actually the diameter of lathing bundle in it, the corresponding value was no more than 2-3 lm.…”

Section: Analysis and Discussionmentioning

confidence: 98%

Influence of Mo content on microstructure and mechanical properties of high strength pipeline steel

Kong

Lin²,

Guo³

et al. 2004

Materials & Design

161

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Section: Analysis and Discussionmentioning

confidence: 98%

Influence of Mo content on microstructure and mechanical properties of high strength pipeline steel

Kong

Lin²,

Guo³

et al. 2004

Materials & Design

161

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“…Alternatively, XRD broadening may arise from a polycrystalline precipitate structure (i.e., the domain size is a measure of the grain size within the precipitate and not the total precipitate size). However, selected area diffraction (SAD) analysis of the relatively large microalloyed steel precipitates [1] indicates the precipitates are single crystals; as such, the domain and precipitate size are equivalent.…”

Section: Size Of Precipitates >90 Nmmentioning

confidence: 99%

“…The characterization of precipitates in microalloyed steels can be undertaken using a number of analytical techniques, including optical microscopy [1,2], scanning electron microscopy (SEM) [3][4][5][6], transmission electron microscopy (TEM) [2,3,7,8], energy dispersive X-ray (EDX) analysis [2,3,8,9], and small angle neutron scattering (SANS) [10]. Each technique has its own advantages (and disadvantages) in terms of quantifying the number density, volume or weight fraction, composition and/or size of the precipitates.…”

Section: Introductionmentioning

confidence: 99%

Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction

Wiskel

Lü²,

Omotoso

et al. 2016

Metals

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Quantitative X-ray diffraction (QXRD) (also known as the Rietveld method) was used to analyze the precipitates present in Grade 100 microalloyed steel. The precipitates were extracted from the steel using electrolytic dissolution and the residue from the dissolution was analyzed using XRD. The XRD pattern exhibited three (3) distinct diffraction peaks, and significant broadening of a fourth peak corresponding to the <10 nm size precipitates. QXRD analysis was applied to the XRD pattern to obtain precipitate size, composition, and weight fraction data for each of the four diffraction peaks observed. The predicted mean precipitate diameter and average atomic composition of the nano-size (<10 nm) precipitates was 4.7 nm and (Nb 0.50 Ti 0.32 Mo 0.18 )(C 0.59 N 0.41 ), respectively. The predicted precipitate size correlates well with the average size of precipitates measured in previous work by the authors using both transmission electron microscopy (TEM) and small angle neutron scattering (SANS). The average atomic composition correlates well with the composition measured in this work using energy dispersive X-ray (EDX) analysis of individual nano-sized precipitates. The calculated weight fraction of the nano-size precipitates in the extracted residue was 42.2 wt. %. The calculated atomic compositions of the other three diffraction peaks were TiN, (Ti 0.87 Nb 0.13 )N, and (Nb 0.82 Ti 0.18 )(C 0.87 N 0.13 ) with weight fraction values of 12.9 wt. %, 31.7 wt. %, and 13.1 wt. %, respectively. The sizes of both the (Ti 0.87 Nb 0.13 )N and the (Nb 0.82 Ti 0.18 )(C 0.87 N 0.13 ) groups of precipitates were directly measured and were observed to range from 150 nm to 570 nm and from 90 nm to 475 nm, respectively. QXRD was unable to determine a reasonable mean precipitate size for either of these two groups of precipitates. The wide compositional range (i.e., varying levels of Nb and Ti) of these precipitates (as measured by EDX) resulted in XRD peak broadening that was erroneously interpreted as a size broadening effect.

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“…Development of construction in transmission pipeline for oil and gas evolves the requirement of microalloyed steels with higher strength and lower price. Increasing of steel grade will reduce costs of pipe production and implementing action [2]. API X70 steel is categorized in the high strength microalloyed steels and is used as the main steel in production of the transmission pipelines of oil and gas, due to the mechanical strength.…”

Section: Introductionmentioning

confidence: 99%

Production of Ultrafine Grained API X70 Steel with Controlled Rolling

Abdideh¹,

Hizombor²,

Rad³

et al. 2013

AMR

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Development of industries in recent years reveals the essential need to the microalloyed steels with high strength and good ductility. Refinement of Ferrite grains by thermomechanical Treatment is the only lower cost effective method to improve strength and toughness spontaneously in this type of steels. API X70 steel belongs to high strength microalloyed steel group. The manufacturing process of this steel is controlled rolling which is a kind of thermomechanical treatment and it is considered as a grain refining method. In this research, three specimens of API X70 steel were experimentally rolled in order to achieve ultrafine grained microstructure. Rolling operations are designed in such a way that the rolling of these specimens finished at 846, 823 and 800°C. Results of the experiments were analyzed by mechanical tests and microstructures observations. The microstructure observations show that decreasing of finish rolling temperature causes decrease in Ferrite grain size. Results also show that rolling of API X70 steel in the vicinity of Ar3temperature and high strain rates lead to ultrafine Ferrite grains in microstructure. This is due to the transformation of work hardened austenite to Ferrite. On the other side, Tensile and impact tests show that decreasing of finish rolling temperature causes increasing in yield and tensile strength and also improves the toughness.

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Microstructure of Microalloyed Linepipe Steels

Cited by 4 publications

References 13 publications

Influence of Mo content on microstructure and mechanical properties of high strength pipeline steel

Influence of Mo content on microstructure and mechanical properties of high strength pipeline steel

Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction

Production of Ultrafine Grained API X70 Steel with Controlled Rolling

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