Materials Processing Fundamentals: Steelmaking
Sponsored by: TMS Extraction and Processing Division, TMS: Process Technology and Modeling Committee
Program Organizers: Antoine Allanore, Massachusetts Institute of Technology; Jonghyun Lee, Iowa State University; Guillaume Lambotte, Boston Electromet
Wednesday 8:30 AM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Guillaume Lambotte, Boston Electromet; Antoine Allanore, Massachusetts Institute of Technology
A Systems Approach for Modeling the Dynamic Thermomechanical Response of Carbon Steels: Shengyen Li1; Steven Mates1; Mark Stoudt1; Carelyn Campbell1; Greta Lindwall1; Sindhura Gangireddy1; 1National Institute of Standards and Technology
In manufacturing processes, workpiece materials are subjected to rapid heating, high loading rates and large plastic strains. Depending on the temperatures involved, the phase transformations can occur that significantly affects the mechanical behavior. For example, the initial pearlite/ferrite steel system can transform into a pearlite/ferrite/austenite microstructure, drastically reducing alloy strength. To capture this behavior, we use diffusion-controlled models along with dislocation-mechanics based constitutive model to predict time-dependent plastic deformation under rapid heating and loading. The systems approach to this problem includes data collection, model simulation, and software application, with a workflow concept based on easy entry from microstructure information, thermomechanical data, to mechanical measurements, into a materials data curation system (MDCS). The MDCS supports essential information to calibrate phase-based models, being applied to different sets of experimental conditions. This systems approach is designed for other materials systems and/or different micromechanical behaviors, such as dynamic strain ageing in steels.
Development of Ultra High-basicity Mold Fluxes for Peritectic Steel Continuous Casting: Xiao Long1; Shengping He1; Qian Wang1; Petrus Pistorius2; 1Chongqing University; 2Carnegie Mellon University
In the continuous casting of peritectic steels, mold fluxes play significant roles in providing defect-free surfaces of slabs. In this work, a traditional high-basicity mold flux was studied. Slag film samples were solidified from molten flux, with an improved water-cooled copper probe and using different probe immersion times. The film microstructures, interfacial roughness and porosity were studied. Based on the results, ultrahigh-basicity mold fluxes (CaO wt%/SiO2 wt%=1.5~1.8) were developed. A typical ultrahigh-basicity mold flux (CaO wt%/SiO2 wt%=1.74) was analyzed in the laboratory and applied in industrial processes. The laboratory experiments and industrial results indicate that the novel mold fluxes developed in this work have excellent performance in balancing heat transfer control by the solid film and lubrication by molten flux.
Evolution and Formation of CaS-bearing Inclusion in Low-Carbon Al-killed Steel: Yanhui Sun1; Xuefeng Bai1; 1University of Science and Technology Beijing
Evolution of CaS-bearing inclusion characteristics (size, composition, morphology, structure) in low-carbon Al-killed and Ca-treated steel was investigated systematically in industrial trials. Analysis methods include scanning electron microscopy (SEM), inclusion classifier feature (INCA FEATURE) and energy dispersive spectroscopy (EDS). Moreover, classical thermodynamics and software Factsage were applied to calculate the stability diagram and equilibrium precipitation of inclusions during refining and solidification process. The results indicated that the formation of CaS-bearing inclusion in steel can form in three ways. The first is that CaS acts as an intermediate reaction product modifying Al2O3 inclusions shortly after calcium treatment and then the mixture converts to xCaO•yAl2O3. The second is that [S] and [Al] reacts with CaO in liquid CaO-Al2O3 (-MgO) inclusion during secondary refining and continuous casting. The third one is that CaS could precipitate on the surface of low modified MgO•Al2O3 spinel and Al2O3 core during solidification.
Influence of MgO Saturation on the ConSteel EAF Foaming Slag Practice: Esmail Ahmad1; Magnus Krokstad2; Reza Beheshti1; Ragnhild Aune1; 1NTNU; 2Celsa Nordic Amerinsstål
To ensure a stable and efficient processing of scrap in an Electric Arc Furnaces (EAF) good slag foaming practice is essential. Foamy slag requires full control of the chemical composition of the slag in order to control the slag viscosity and gas generation rate. In the present work experiments have been performed with the aim to study the saturation of MgO in the Al2O3-MnO-CaO-SiO2-FeO slag used in the ConSteel EAF production at Celsa Armeringstål in Norway. Molten slag samples, with the FeO content ranging from 20-40% and the basicity (CaO%/SiO2) from 1.6-2.1, have been thermally treated at 1550-1750˚C at temperature steps of 100˚C. The chemical composition of each sample was later evaluated and used as input data for thermodynamically evaluating Isothermal Stability Diagrams (ISD) at constant basicity and temperature. The obtained results are compared and discussed in view of the data available in Factsage version 7.0 for the same system.