Abnormal grain growth in a medium-carbon microalloyed steel

Cabrera, J.M.; Omar, A. Al; Prado, J. M.

doi:10.1007/bf00353110

Cited by 31 publications

(24 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…⅐ ϭ f (, T, S , P ) [1] i j dS i ϭ g (, T, S , P ) [2] i j dt where ⅐ ε is the strain rate, is the flow stress, T is the temperature, S i is the set of state variables that describe the current microstructure (grain size, dislocation density, etc. ), and P j is characteristic properties such as the atomic volumes, bond energies, diffusion constants, etc.…”

Section: Introductionmentioning

confidence: 99%

Modeling the flow behavior of a medium carbon microalloyed steel under hot working conditions

Cabrera

Omar

Prado

et al. 1997

Metall Mater Trans A

Self Cite

177

View full text Add to dashboard Cite

The constitutive equations for the flow behavior of a commercial 0.34 pct C-1.5 pct Mn-0.7 pct Si-0.083 pct V-0.018 pct Ti microalloyed steel were determined. For this purpose, uniaxial hot compression tests were carried out over a wide range of strain rates (10 Ϫ4 to 10 s Ϫ1 ) and temperatures (1123 to 1423 K). In combination with models developed in the literature, the experimental results permit the flow stress of the present steel to be predicted within ‫5ע‬ pct. It is shown that the classical constitutive equations must be modified to take the grain size into account, particularly when the latter is below 30 m.

show abstract

Section: Introductionmentioning

confidence: 99%

Modeling the flow behavior of a medium carbon microalloyed steel under hot working conditions

Cabrera

Omar

Prado

et al. 1997

Metall Mater Trans A

Self Cite

177

View full text Add to dashboard Cite

show abstract

“…The experimental observations are consistent with previous research on the effects of second phase particles on normal and abnormal grain growth. 17,[23][24][25][26][27][28][29] The combined effects of alloy content and thermal processing on the resulting austenite grain structure are complex and reflect competition between the driving forces for normal/abnormal grain growth and pinning forces of precipitates as controlled by precipitate type and size distribution. 17,[30][31][32][33][34][35][36][37][38][39][40][41][42][43] Abnormal grain growth is an important consideration in steels with pinning particles, since AGG can lead to austenite grains that are significantly greater in size than those observed in plain carbon steels where NGG is manifested at all temperatures.…”

Section: Discussionmentioning

confidence: 99%

The Influence of Niobium Microalloying on Austenite Grain Coarsening Behavior of Ti-modified SAE 8620 Steel

2007

View full text Add to dashboard Cite

The potential for suppressing unacceptable austenite grain growth during carburizing by Nb microalloying additions in the range of 0.02 to 0.11 wt% to a Ti-modified SAE 8620 carburizing steel were evaluated. Alloys, were designed based on fundamental equilibrium thermodynamic analyses, as part of an extensive study on the effects of alloy composition, thermomechanical history, and pseudo-carburizing conditions on austenite grain coarsening behavior. Laboratory samples were produced to simulate both conventional hot rolling and controlled rolling practices designed to produce different initial precipitate distributions. Pseudocarburizing heat treatments, i.e. without a carburizing atmosphere, were performed in the temperature range of 950 to 1 100°C for holding times of 30 to 360 min. Precipitate distributions, including size, number density, morphology, distribution, and chemical composition in selected samples from the as-rolled and pseudo-carburized conditions were evaluated with transmission electron microscopy on extraction replicas. Results showed that increasing Nb additions to the Ti-modified SAE 8620 steel restrained austenite grain coarsening, and increased the grain coarsening time, especially at temperatures below 1 050°C. The Nb-free (Ti-modified) steel yielded either severely duplex grain structures or pseudo-normal grain growth (with very large mean grain diameter). However, holding a Ti-Nb-modified steel (e.g. 0.06 Nb wt%) at 950°C for 6 h or at 1 000°C for 4 h. produced fine and uniform austenite grain structures (with a mean grain diameter less than 20 mm). The finer grain sizes observed in the Ti-Nb-modified steels were due to the presence of Nbrich precipitates that hinder austenite grain coarsening, and precipitate distributions and grain growth behaviors are also influenced by the steel rolling history. The results indicate that Nb can successfully be used to suppress grain growth in carburizing steels.KEY WORDS: niobium microalloying; carburizing; precipitation; abnormal grain growth. © 2007 ISIJ Alloy and Process Design 2.1. Thermodynamic Basis for Alloy SelectionExperimental alloys, intended to assess the ability of niobium additions to suppress austenite grain coarsening at elevated temperatures, were developed based on fundamental equilibrium thermodynamic analyses of niobium-carbide precipitate formation. Following the previous work of Davidson et al.,7) which showed that a maximum retardation effect on austenite grain coarsening at carburizing temperatures was observed in a Ti-modified SAE 8620 steel with a Ti : N ratio close to stoichiometric (3.42 by weight), the experimental alloys were developed based on the following assumptions: i) Titanium added stoichiometrically to the SAE 8620 steel will precipitate N as TiN; ii) In the Ti-modified SAE 8620 steel, added niobium will precipitate as NbC; and iii) Maximum temperatures experienced during solid-state processing are below about 1 300°C. With these assumptions, the desired niobium levels were determined based on solubility product ...

show abstract

“…To validate the latter equation at low volume fractions, several experimental results published in the literature [10,[16][17][18][19][20][21][22][23][24][25][26] were employed, as shown in Figure 9, where R c /r is plotted vs f v . One can see a good agreement between these results and Eq.…”

Section: Validation Of Present Modificationsmentioning

confidence: 99%

“…The total variation in the surface area per average grain, , will be the sum of the variations of (dS M /dR M )/N M and the variations in surface area due to the presence of particles given by Eq. [10]: [15] In the case of spherical grains, , and therefore, [16] Grain growth stops when the mean radius is equal to a critical radius R c so that [17] Accordingly, [18] When particles are spherical of radius r and volume fraction f v , the latter expression is simplified to Eq. [19]: [19] Introducing into Eq.…”

Section: Practical Effect Of Particles Clustering On Grain Growthmentioning

confidence: 99%

“…This model has predicted with high accuracy experimental data of several alloys such as microalloyed steels at relatively low volume fractions of particles. [16][17][18] The model is based, following that of Orowan for dislocations, on the additional surface area created at the particle-matrix interface when a grain boundary overpasses a particle. The clustering of particles, in fact, promotes a diminution of the superficial are of the precipitate available to pin the grain boundary, as illustrated in Figure 8.…”

Section: Practical Effect Of Particles Clustering On Grain Growthmentioning

confidence: 99%

See 1 more Smart Citation

Effect of clustering of precipitates on grain growth

Flores

Cabrera

Prado

2004

Metall Mater Trans A

Self Cite

View full text Add to dashboard Cite

The present work shows that clustering of particles promotes deviation in the classical mathematical expressions describing the grain growth control by second-phase particles. On the basis of experimental results and theoretical laws, a semiempirical expression to predict the limiting grain size is presented. The latter expression takes account of agglomeration phenomena and can be extended to large volume fractions of particles, conditions under which classical theories clearly fail. The equation remains valid as far as the nucleation of precipitates takes place at random. From a practical point of view, it is shown that volume fractions larger than 0.12 cannot significatively control the grain size because of the increased probability for clustering.

show abstract

Abnormal grain growth in a medium-carbon microalloyed steel

Cited by 31 publications

References 10 publications

Modeling the flow behavior of a medium carbon microalloyed steel under hot working conditions

Modeling the flow behavior of a medium carbon microalloyed steel under hot working conditions

The Influence of Niobium Microalloying on Austenite Grain Coarsening Behavior of Ti-modified SAE 8620 Steel

Effect of clustering of precipitates on grain growth

Contact Info

Product

Resources

About