Effect of austenite grain size on the bainitic ferrite morphology and grain refinement of a pipeline steel after continuous cooling

Zhao, Hao; Wynne, B.P.; Palmiere, E.J.

doi:10.1016/j.matchar.2016.11.025

Cited by 50 publications

(31 citation statements)

References 32 publications

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“…The toughness of a material is closely related to the ratio of large-angle grain boundaries in the microstructure. [15][16][17] The difference in the orientation angle of adjacent grain boundaries can determine the extension path of the microcracks in the material. When the microcrack extension encounters a large-angle grain boundary, it will deflect and hinder its rapid propagation, thus improving the crack propagation energy of the material.…”

Section: Misorientation and Misorientation Angle Distributionsmentioning

confidence: 99%

Microstructure evolution and fracture analysis of hot-rolled explosive-welded 06Cr13/Q345R composites

Li¹,

Zhao²,

Li³

et al. 2019

Mater. Tehnol.

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In this paper, with electron backscatter diffraction (EBSD) and SEM, the microstructure evolution and fractography of bonded interfaces were analyzed at various reduction rates (0, 15, 30, 40, 50 and 60) %. A 06Cr13/Q345R explosive-welded composite interface of 50-80 μm was the impact area of explosive cladding where the grains of 06Cr13 and Q345R were both low-sized and uniform. Subsequent to hot rolling, the explosive-welding effect on the 06Cr13-side interface was rapidly weakened. Compared to the 06Cr13-steel side, the explosive-cladding effect on the Q345R-side interface was slowly weakened. A continuous orientation distribution occurred, which indicated that a continuous, dynamic recrystallization mechanism existed in the explosive-welded composite plate. In contrast, the dominant recrystallization-deformation mechanism was the discontinuous, dynamic recrystallization, taking place under the rolling deformation. Two peaks existed between the 30-% reduction rate and the 60-% reduction rate, and they were apparently at positions <15°and 50°-60°. As the rolling reduction rate increased, the two materials were significantly bonded together and the interface diffusion distances of the peaks and valleys decreased and tended to be homologous, whereas the composite interface fault was increasingly less apparent.

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Section: Misorientation and Misorientation Angle Distributionsmentioning

confidence: 99%

Microstructure evolution and fracture analysis of hot-rolled explosive-welded 06Cr13/Q345R composites

Li¹,

Zhao²,

Li³

et al. 2019

Mater. Tehnol.

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“…3a, the microstructure contains some aggregates of BF laths with an almost entirely granular aspect with the boundaries between these laths not very clear. This kind of microstructure is usually termed as granular bainite (GB) [5,31]. At the cooling rate of 50°C s -1 , Fig.…”

Section: Optical Microstructurementioning

confidence: 99%

Conditions for the occurrence of acicular ferrite transformation in HSLA steels

2017

Self Cite

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For the class of steels collectively known as high strength low alloy (HSLA), an acicular ferrite (AF) microstructure produces an excellent combination of strength and toughness. The conditions for the occurrence of the AF transformation are, however, still unclear, especially the effects of austenite deformation and continuous cooling. In this research, a commercial HSLA steel was used and subjected to deformation via plane strain compression with strains ranging from 0 to 0.5 and continuous cooling at rates between 5 and 50°C s -1 . Based on the results obtained from optical microscopy, scanning electron microscopy and electron backscattering diffraction mapping, the introduction of intragranular nucleation sites and the suppression of bainitic ferrite (BF) laths lengthening were identified as the two key requirements for the occurrence of AF transformation. Austenite deformation is critical to meet these two conditions as it introduces a high density of dislocations that act as intragranular nucleation sites and deformation substructures, which suppress the lengthening of BF laths through the mechanism of mechanical stabilisation of austenite. However, the suppression effect of austenite deformation is only observed under relatively slow cooling rates or high transformation temperatures, i.e., conditions where the driving force for advancing the transformation interface is not sufficient to overcome the austenite deformation substructures.

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“…Because grain boundary is of high energy, the decrease in grain size reduces the hardenability of austenite. Therefore, soft microstructures are generated after the transformation of austenite . When austenitizing temperature is larger than 1100 °C, the prior austenite grain size is large.…”

Section: Resultsmentioning

confidence: 99%

The Effect of Initial Microstructure on Microstructure Evolution and Mechanical Properties of Intercritically Rolled Low‐Carbon Microalloyed Steel Plates

Shen

Chen

et al. 2019

steel research int.

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Steel plates rolled in the intercritical region have ultrafine and elongated‐grained microstructures, and excellent toughness. The effect of the initial microstructure on microstructure evolution and the mechanical properties of intercritically rolled (IR) low‐carbon microalloyed steel plates is investigated herein. Coarse‐grained initial microstructure mainly containing lath bainite and fine‐grained initial microstructure mainly containing quasi‐polygonal ferrite are produced by austenitization treatments at different temperatures. The results show that the coarse‐grained initial microstructure restrains continuous dynamic recrystallization during intercritical rolling, which leads to a less fraction of high‐angle grain boundaries (HAGBs). However, initial microstructure has little influence on the average size of ferrite grains surrounded by HAGBs. Moreover, coarse‐grained initial microstructure results in a relatively higher strength improving about 15 MPa due to the lower fraction of HAGBs. Fine‐grained initial microstructure is beneficial to the Charpy impact toughness such that the upper shelf energy is improved from 108 to 118 J, and low‐temperature toughness is also enhanced. However, the effect of the initial microstructure on the microstructure and mechanical properties of IR rolled steel plates is not great, which indicates that coarse‐grained initial microstructure can also be used to develop this kind of steel plates with excellent toughness.

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Effect of austenite grain size on the bainitic ferrite morphology and grain refinement of a pipeline steel after continuous cooling

Cited by 50 publications

References 32 publications

Microstructure evolution and fracture analysis of hot-rolled explosive-welded 06Cr13/Q345R composites

Microstructure evolution and fracture analysis of hot-rolled explosive-welded 06Cr13/Q345R composites

Conditions for the occurrence of acicular ferrite transformation in HSLA steels

The Effect of Initial Microstructure on Microstructure Evolution and Mechanical Properties of Intercritically Rolled Low‐Carbon Microalloyed Steel Plates

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