Analysis of columnar-to-equiaxed transition experiment in lab scale steel casting by a multiphase model

Abstract

Correct prediction of composition heterogeneities and grain structure across a steel ingot is critical in optimizing the industrial processing parameters for enhanced performance. The columnar to equiaxed transtion (CET) is a microstructural transition which is strictly controlled as it affects the mechanical properties of the final product along with the macrosegregation patterns. Larger equiaxed regions are preferred for most industrial applications. CET is significantly affected by the number density of equiaxed grains and by the nucleation undercooling. 8 kg 42CrMo4 alloy steel ingots (240 mm x 60 mm x 60 mm) were cast. The cast structure was characterized by ASCOMETAL. The experiments were simulated with a process-scale model of solidification that incorporates a multiscale description of the microstructure formation. The goal of the present study is to show the capabilities of such a process-scale solidification model to explain the observed structure distributions (extent of the columnar and equiaxed zones, equiaxed-to-columnar transition).

Numerical modeling of a benchmark experiment on equiaxed solidification of a Sn–Pb alloy with electromagnetic stirring and natural convection

“…Furthermore, it is generally supposed that electromagnetic stirring promotes fragmentation of dendrites and these fragments serve as nucleation sites or already present equiaxed grains. This can be introduced into the model using various assumption [28,49]. In the present work this phenomena was not taken into account to decrease number of uncertain parameters, yet, it deserves further study.…”

Concurrent model for sharp and progressive columnar to equiaxed transitions validated by directional solidification experiments processed in microgravity conditions

“…Since Flood and Hunt, several authors have critically reviewed the selection of the blocking fraction and alternative values have been proposed. Biscuola and Martorano [26] proposed a blocking fraction as low as 𝜙 = 0.2 or Al-7wt.%Si, Sachi et al [27] used a blocking fraction of 𝜙 = 0.5, Pineda and Martorano [28] found improved agreement in their results with a blocking fraction of 𝜙 = 0.99 and Mirihanage et al [29] proposed a blocking fraction of unity with their macroscopic model of CET. The range of blocking fractions proposed in the literature (from 0.2 to unity) demonstrates the importance of model validation with experimental datasets in order to characterize any given model's blocking fraction when using the mechanical blocking criterion.…”