Particle-Size-Grouping Model of Precipitation Kinetics in Microalloyed Steels

Xu, Kun; Thomas, Brian G.

doi:10.1007/s11661-011-0938-y

Cited by 16 publications

(10 citation statements)

References 79 publications

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“…As result shows, the characteristics of particles in Fe-O-Al-Ca melts are dependent on their collision and coagulation behavior. The collision rate of particles in the liquid steel can be estimated as population balance model for collision 44,59 :Where d n i /d t is collision rate of particles (mm −3 ·s −1 ), n i is the number of size i particles per unit volume (mm −3 ) and β i , j is the collision frequency between size i and size j particles (m 3 ·s −1 ). δ i,k is the Kronecker delta 60 , δ i,k = 1 for i = k, and δ i,k = 0 for i ≠ k. When i = 1, the Equation simplifies to…”

Section: Discussionmentioning

confidence: 99%

Coarsening Behavior of Particles in Fe-O-Al-Ca Melts

Wang

Yang

et al. 2019

Sci Rep

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The characteristics of particles greatly affect the microstructure and performance of metallic materials, especially their sizes. To provide insight into coarsening phenomena of particles in metallic melts, Fe-O-Al-Ca melt with calcium aluminate particles was selected as a model system. This study uses HT-CSLM, SEM detections and stereological analysis to probe the behavior of particles and their characteristics including size, number density, volume fraction, spreading of particle size, inter-surface distance and distribution of particles. Based on the experimental evidence and calculation of collision, we demonstrate that the coarsening of inclusion particles is not only dependent on the Ostwald growth as studied in previous study, but also on the particle coagulation, and floatation. The collision of particles affects the maximum size of the particles during whole deoxidation process and dominates the coarsening of particles at later stage of deoxidation under the condition without external stirring in Fe-O-Al-Ca melts. The factors influencing collision behaviors and floating properties were also analyzed, which is corresponding to coarsening behavior and change of particle characteristic in the melts with different amounts of Ca addition. Such coarsening mechanism may also be useful in predicting the size of particles in other metallic materials.

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Section: Discussionmentioning

confidence: 99%

Coarsening Behavior of Particles in Fe-O-Al-Ca Melts

Wang

Yang

et al. 2019

Sci Rep

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“…The presence of precipitates in the steels at the TMCP conditions considered in this study means that a unimodal grain size structure can be expected if these precipitates are effective in pinning the grain boundaries. 5,14,15) …”

Section: The Solubility Behavior Of the Precipitatesmentioning

confidence: 99%

“…The Zener pinning forces offered by the precipitates in these steels are also found to be more effective than the driving force for grain growth, hence greater grain growth inhibition. 5,6,15,16) Figure 5 shows the STEM images of precipitates observed by TEM after reheating of 0.03%Nb steel at different austenitizing temperatures.…”

Section: Microstructure and Grain Size Distributionmentioning

confidence: 99%

Austenite Grain Growth Kinetics after Isothermal Deformation in Microalloyed Steels with Varying Nb Concentrations

2018

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Grain growth equation constants n, Q and A for Nb bearing steels with the Nb varying from 0.002 wt% to 0.1 wt%, were experimentally determined under reheating and high temperature hot rolling roughing conditions. The constants from these treatments were then used to develop constitutive equations that incorporate the initial grain size D o and a Nb-effect for grain growth predictions in these steels. Comparative analysis of the results showed that the values of the constants generated under rough rolling deformation conditions were slightly higher than those generated under reheating conditions. The activation energy for grain boundary migration Q was found to be in the range of 256 to 572 kJ/mol, the exponential constant n ranged from 2.6 to 6.5 and the material and processing condition's constant A was found to range from 5.23 × 10 11 to 4.96 × 10 28 in all cases as a function of the Nb content. Analysis of the influence of the initial grain size D o showed that any contribution of D o can be neglected unless it is equal or more than 70 percent of the average size of the measured austenite grain size D. A logical degree of precision in predicting austenite grain growth in microalloyed steels with different Nb contents, has been achieved in the current work.

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“…The observed results are in agreement with Zener's basic relationship for the pinning force of particles on grain boundaries (Zener, 1948, as cited by Ringer, Li, and Easterling, 1989), which predicts a stronger effect of pinning with increased volume fractions of small precipitates at constant particle sizes. The higher Nb content accounts for a greater volume fraction of NbN precipitates as shown in Figure 3, providing a greater area fraction of solute-rich regions compared to the steels containing less Nb (Xu and Thomas, 2011;Brewer, Erven and Krauss, 1991;Deus et al, 2002;Akamatsu, Senuma and Hasebe, 1992). The quantitative analysis of the optical measurements of austenite grain growth, is shown in Figure 6, which confirms the substantial influence of an increased Nb content on austenite grain growth inhibition in these steels.…”

Section: Austenite Grain Growth Behaviour In the Steels After Deformamentioning

confidence: 98%