Segregation in cast products

Spatial distribution in size and frequency of microalloy precipitates have been characterized in two continuous-cast high-strength, low-alloy steel slabs, one containing Nb, Ti, and V and the other containing only Ti. Microsegregation during casting resulted in an inhomogeneous distribution of Nb and Ti precipitates in as-cast slabs. A model has been proposed in this study based on the detailed characterization of cast microalloy precipitates for predicting the spatial distribution in size and volume fraction of precipitates. The present model considers different models, which have been proposed earlier. Microsegregation during solidification has been predicted from the model proposed by Clyne and Kurz. Homogenization of alloying elements during cooling of the cast slab has been predicted following the approach suggested by Kurz and Fisher. Thermo-Calc software predicted the thermodynamic stability and volume fraction of microalloy precipitates at interdendritic and dendritic regions. Finally, classical nucleation and growth theory of precipitation have been used to predict the size distribution of microalloy precipitates at the aforementioned regions. The accurate prediction and control over the precipitate size and fractions may help in avoiding the hot-cracking problem during casting and selecting the processing parameters for reheating and rolling of the slabs.

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“…The equilibrium partition ratio (k p ) of various alloying elements in steel are listed in Table IV, [11,27,28] …”

Section: A Dependence Of Microsegregation On the Solidification Sequmentioning

confidence: 99%

Prediction of Inhomogeneous Distribution of Microalloy Precipitates in Continuous-Cast High-Strength, Low-Alloy Steel Slab

Roy

Patra

Neogy

et al. 2012

Metall Mater Trans A

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“…An equation for global segregation intensity can be derived by integrating the local segregation intensity [5]:…”

Section: Effect Of V Y On the Formation Of Positive Segregation Profilementioning

confidence: 99%

“…On the other hand, negative segregation takes place in the lower part of the ingot that can be explained by the sedimentation of equiaxed crystals formed in the bulk liquid. Several segregation models, as well as experimental results on segregation intensity, were presented [1][2][3], and macro-segregation modeling was reviewed [4,5].…”

Section: Introductionmentioning

confidence: 99%

Positive segregation as a function of buoyancy force during steel ingot solidification

Radović

Jaukovic

Lalovic

et al. 2008

Science and Technology of Advanced Materials

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We analyze theoretically and experimentally solute redistribution in the dendritic solidification process and positive segregation during solidification of steel ingots. Positive segregation is mainly caused by liquid flow in the mushy zone. Changes in the liquid steel velocity are caused by the temperature gradient and by the increase in the solid fraction during solidification. The effects of buoyancy and of the change in the solid fraction on segregation intensity are analyzed. The relationships between the density change, liquid fraction and the steel composition are considered. Such elements as W, Ni, Mo and Cr decrease the effect of the density variations, i.e. they show smaller tendency to segregate. Based on the modeling and experimental results, coefficients are provided controlling the effects of chemical composition, secondary dendrite arm spacing and the solid fraction.

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“…Generally, when the partition coefficient is high, the partitioning effect is weak, and consequently, a small segregation degree is obtained during solidification [1]. The equilibrium partition coefficient varies from 0 to 1 for most solutes in steel [2,5], thereby indicating that a solute may be rejected from the solid phase to the liquid phase, which enriches the liquid phase during solidification. The solutes may concentrate in the residual liquid pool due to convection, which results in center segregation at the end of the solidification process of casting steel blank [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Phase Transition of Peritectic Steel Q345 and Its Effect on the Equilibrium Partition Coefficients of Solutes

Chen

Long

Cao

et al. 2017

Metals

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Abstract:The solidification path of peritectic steel Q345 was calculated and compared with in-situ observations to investigate the effect of phase transition on the equilibrium partition coefficient. Subsequently, a thermodynamic model for calculating the equilibrium partition coefficient was established and thermodynamic calculations were performed under different phase configurations. Results indicate that L (liquid phase) + δ, L + δ + γ, and L + δ phases coexist in sequence during the solidification of peritectic steel Q345. The phase constitution of the mushy zone evidently affects the evolution of the equilibrium partition coefficient of solutes. The temperature dependence of the equilibrium partition coefficient was quantified through the regression analyses of C, Si, Mn, P, and S solutes under different phase configurations. The average equilibrium partition coefficients of Mn, Si, P, C, and S are 0.696, 0.615, 0.273, 0.2, and 0.033, respectively, thereby indicating the strongest segregation tendency for S and the weakest for Mn.

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Segregation in cast products

Cited by 85 publications

References 11 publications

Prediction of Inhomogeneous Distribution of Microalloy Precipitates in Continuous-Cast High-Strength, Low-Alloy Steel Slab

Prediction of Inhomogeneous Distribution of Microalloy Precipitates in Continuous-Cast High-Strength, Low-Alloy Steel Slab

Positive segregation as a function of buoyancy force during steel ingot solidification

Phase Transition of Peritectic Steel Q345 and Its Effect on the Equilibrium Partition Coefficients of Solutes

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