Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

Li, Rutao; Zuo, Xunwei; Hu, Yueyue; Wang, Zhenwei; Hu, D S

doi:10.1016/j.matchar.2011.05.013

Cited by 45 publications

(10 citation statements)

References 19 publications

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“…Austenite that did not transform to ferrite turned to martensite (M) with complicated substructures subdivided by LAB and HAB during quenching immediately after the hot-compression. The KAM value corresponds to local misorientation within each grain [25], so that it expresses the degree of strains accumulated within grains. Ferrite grains show smaller KAM values (less-red colours) than martensite representing more red colours in Figure 4(a), which corresponds to the difference in misorientation (lattice defects) between ferrite and martensite.…”

Section: Resultsmentioning

confidence: 99%

Microstructure evolution during thermomechanical processing in 3Mn-0.1C medium-Mn steel

Hou

Bai

Shibata

et al. 2019

Materials Science and Technology

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Medium-Mn steels are energetically investigated as a candidate of the third generation advanced high strength steels (AHSSs). However, their phase transformation and microstructaure evolution during various heat treatments and thermomechanical processing are still unclear. The present study first confirmed the kinetics of static phase transformation behaviour in a 3Mn-0.1C medium-Mn steel. Hot compression tests were also carried out to investigate the influence of high-temperature deformation of austenite on subsequent microstructure evolution. It was found that static ferrite transformation was quite slow in this steel, but ferrite transformation was greatly accelerated by the hot deformation in austenite and ferrite two-phase regions. Characteristic dual-phase microstructures composed of martensite and fine-grained ferrite were obtained, which exhibited superior mechanical properties. This paper is part of a Thematic Issue on Medium Manganese Steels.

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Section: Resultsmentioning

confidence: 99%

Microstructure evolution during thermomechanical processing in 3Mn-0.1C medium-Mn steel

Hou

Bai

Shibata

et al. 2019

Materials Science and Technology

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“…To increase transport efficiency and to lower the costs of pipeline construction, longitudinally submerged arc welded (LSAW) pipes with larger diameters and thicker walls have been increasingly used by the pipeline industry. [1][2][3][4] For example, in Russia, the LSAW pipeline in the Bovanenkovo-Ukhta project 2 was recently constructed with K65 steel (the highest grade of the Russian natural gas pipeline), which is similar in specifications and yield strength requirement (550 MPa grade) to API X80 but has a stricter low temperature toughness value of 60 J at −40°C (compared to −20°C for API X80 grade 5,6 ) due to the extreme Arctic environment. In that project, in which over 1.8 million tonnes of pipe were used, the target capacity is 50 billion m 3 /year, and the length of the main line is 2600 km.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the microstructure and toughness of 550 MPa grade pipeline after the hot-bending process

Wang

Tsai

Yang

et al. 2016

Materials Science and Technology

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In this work, the effects of the hot-bending process on the microstructure and low temperature (−40°C) toughness of weld metal of pipeline K65 (the highest grade of the Russian natural gas pipeline) were studied. The weld metal from the longitudinally submerged arc welding (LSAW) pipe making process was compared with that subsequently treated by the hot-bending process. It was found that the latter process led to serious deterioration in toughness, which obviously degraded the sound properties achieved in the original weld metal of LSAW pipes. Microstructural characterisation revealed that the weld metal, which originally consisted mainly of acicular ferrite in the as-deposited condition, became predominantly composed of bainitic ferrite after hot bending. It is clear that reaustenisation caused a smaller austenite grain-sized matrix, which brought about a very high volume fraction of bainite. Consequently, the low temperature toughness was deteriorated, in contrast to the excellent toughness achieved in the as-deposited weld metal.

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“…Particularly, the toughness in the coarse grain heat affected zone (CGHAZ) of high grade pipeline steels deteriorates severely after the welding thermal cycle [4]. In order to evaluate and improve the toughness of the welding joint [5,6], it is necessary to show the evolution of microstructure and toughness in the CGHAZ with varying welding heat inputs, as well as the effective microstructure unit in control of toughness.…”

Section: Introductionmentioning

confidence: 99%

The Role of the Bainitic Packet in Control of Impact Toughness in a Simulated CGHAZ of X90 Pipeline Steel

Guo

Fan

Wang

et al. 2016

Metals

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X90 pipeline steel was processed with the simulated coarse grain heat affect zone (CGHAZ) thermal cycle with heat input varying from 30 kJ/cm to 60 kJ/cm, the microstructures were investigated by means of optical microscope (OM), scanning electron microscope (SEM), electron backscattering diffraction (EBSD), and transmission electron microscope (TEM), and the impact properties were evaluated from the welding thermal cycle treated samples. The results indicate that the microstructure is primarily composed of lath bainite. When decreasing the heat input, both bainite packet and block are significantly refined, and the toughness has an increased tendency due to the grain refinement. The fracture surfaces all present cleavage fracture for the samples with different heat inputs. Moreover, the average cleavage facet size for the CGHAZ is nearly equal to the average bainite packet size, and the bainitic packet boundary can strongly impede the crack propagation, indicating that the bainitic packet is the most effective unit in control of impact toughness in the simulated CGHAZ of X90 pipeline steel.

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Microstructure and properties of pipeline steel with a ferrite/martensite dual-phase microstructure

Cited by 45 publications

References 19 publications

Microstructure evolution during thermomechanical processing in 3Mn-0.1C medium-Mn steel

Microstructure evolution during thermomechanical processing in 3Mn-0.1C medium-Mn steel

Investigation of the microstructure and toughness of 550 MPa grade pipeline after the hot-bending process

The Role of the Bainitic Packet in Control of Impact Toughness in a Simulated CGHAZ of X90 Pipeline Steel

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