The effect of prior austenite grain size on the transformation behaviour of C-Mn-Ni weld metal

Farrar, R. A.; Zhang, Z.; Bannister, S.; Barritte, G. S.

doi:10.1007/bf01191982

Cited by 50 publications

(30 citation statements)

References 5 publications

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“…Other factors, such as composition and austenitization temperature and time, which determine the austenite grain size, also influence the resulting microstructure. [2,3] Acicular ferrite formation is a mechanism competitive with bainite formation, as generally recognized. [4] In the latter case, clusters of bainitic plates grow, emanating from austenite grain surfaces, whereas acicular ferrite plates nucleate intragranularly.…”

Section: Introductionmentioning

confidence: 99%

Upper acicular ferrite formation in a medium-carbon microalloyed steel by isothermal transformation: Nucleation enhancement by CuS

Madariaga

Romero

Gutiérrez

1998

Metall Mater Trans A

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The isothermal transformation vs time of a medium-carbon microalloyed steel at 450 ЊC, following austenitization at 1250 ЊC for 45 minutes, has been investigated using optical microscopy, scanning electron microscopy, and transmission electron microscopy (TEM). At short times, the fine microstructure of acicular ferrite is nucleated at MnS inclusions, which are covered by a shell of a hexagonal CuS phase. The special orientation between MnS and the CuS crystals of this shell enables the formation of a low-energy interface between the ferrite and the inclusion with, at the same time, the ferrite satisfying one of the 24 variants of the orientation relationship into the Bain region with austenite. As the treatment times are increased, the increase in the volume fraction of acicular ferrite being formed raises the carbon concentration of the austenite, such that some retained austenite instead of martensite is observed for these intermediate treatment times. This retained austenite transforms to ferrite plus carbides at long treatment times, resulting in a final microstructure of acicular ferrite, very similar in nature to those encountered in the case of upper bainite formation.

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Section: Introductionmentioning

confidence: 99%

Upper acicular ferrite formation in a medium-carbon microalloyed steel by isothermal transformation: Nucleation enhancement by CuS

Madariaga

Romero

Gutiérrez

1998

Metall Mater Trans A

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“…[8][9][10][11] A lot of authors also have provided convincing evidences that acicular ferrite is essentially intragranularly nucleated banite and is mainly nucleated at inclusions in the weld. [12][13][14] Accordingly, if thermal and chemical conditions in the weld favor the ferrite transformation, acicular ferrite will nucleate at inclusions along with other microstructural constituents.…”

Section: Introductionmentioning

confidence: 99%

Effect of Inclusion Size on the Nucleation of Acicular Ferrite in Welds.

et al. 2000

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Low-carbon steel weld with a high density of oxide inclusions prepared using a experimental metal-cored wire has been examined to study the effect of inclusion size on the formation of acicular ferrite, and to understand the role of inclusion in the nucleation of ferrite lath. Depending on the ferrite morphology associated with inclusions, a total of 282 inclusions observed under TEM could be classified into two groups, i.e. the non-nucleant and the nucleant. Experimental results showed that the group of inclusions acted as nucleant were appreciably larger in size compared with those of non-nucleant resulting in the increased probability of nucleation with the increase of inclusion size, even though the chemical and structural natures appeared to be the same. The group of nucleant-inclusion was further divided into two types depending on the degree of nucleation, which was evaluated by the number of ferrite lath nucleated. Statistical analysis performed on inclusion size indicated that the larger the inclusion size is the more ferrite laths could be nucleated. Those laths nucleated from a large single inclusion have grown in many different radial directions and mostly had a different crystallographic orientation from those of adjacent ferrite laths. As a result of this study, it is demonstrated that larger inclusions are indeed more potent nucleation sites when compared with those of smaller size. Thus it could be concluded that the provision of the inclusion surface as for the inert surface for the heterogeneous nucleation of acicular ferrite lath would be the principal role of inclusions playing in the weld metal of low alloy steels. Other possible mechanisms were also considered, but they were unlikely to be operated in the present weld metal system.

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“…14) The acicular ferrite (AF) is generally expected to form in the bainite range of temperatures. Various authors 8,15,[18][19][20][21][22] have reported that the AF is generated at different temperature ranges in the vicinity of 650-440°C depending on the exact chemical compositions and cooling rate of steels. The acicular ferrite arises when the low-carbon steel is cooled from the austenitic state at a rapid rate, to suppress the formation of GBA, WF and massive ferrite.…”

Section: Effect Of Acicular Ferrite On Mechanical Properties Of Steelsmentioning

confidence: 99%

On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

2009

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The effects of non-metallic inclusions in nucleating acicular ferrite in steels during cooling from a weld or cooling from an austenitic temperature are reviewed. The influence of the acicular ferrite (AF) structure on mechanical properties of steels such as strength and toughness is briefly mentioned. The different factors affecting the formation of acicular ferrite, such as the soluble content of alloying elements in steel, cooling rate from austenitizing temperature, austenite grain size and inclusion characteristics in steel, are discussed. The mechanisms of acicular ferrite formation on non-metallic inclusions, such as reduction of interfacial energy, mismatch strain between the inclusion and ferrite/austenite, thermal strains at the inclusions and changes in matrix composition near the inclusions are also discussed. Finally, the effects of inclusion characteristics, such as size, number and composition are described and their effectiveness in nucleating acicular ferrite is discussed.KEY WORDS: non-metallic inclusions, intragranular acicular ferrite formation, strength and toughness, steel. 1063

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The effect of prior austenite grain size on the transformation behaviour of C-Mn-Ni weld metal

Cited by 50 publications

References 5 publications

Upper acicular ferrite formation in a medium-carbon microalloyed steel by isothermal transformation: Nucleation enhancement by CuS

Upper acicular ferrite formation in a medium-carbon microalloyed steel by isothermal transformation: Nucleation enhancement by CuS

Effect of Inclusion Size on the Nucleation of Acicular Ferrite in Welds.

On the Role of Non-metallic Inclusions in the Nucleation of Acicular Ferrite in Steels

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