Advanced Real Time Imaging: Iron & Steelmaking
Sponsored by: TMS Functional Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Alloy Phases Committee
Program Organizers: Jinichiro Nakano, MatterGreen; David Alman, National Energy Technology Laboratory; Il Sohn, Yonsei University; Hiroyuki Shibata, Tohoku University; Antoine Allanore, Massachusetts Institute of Technology; Candan Tamerler, University of Kansas; Noritaka Saito, Kyushu University; Neslihan Dogan, TU Delft; Zuotai Zhang, Southern University of Science and Technology; Bryan Webler, Carnegie Mellon University; Anna Nakano, US Department of Energy National Energy Technology Laboratory
Tuesday 8:30 AM
February 25, 2020
Room: Theater A-4
Location: San Diego Convention Ctr
Session Chair: Il Sohn, Yonsei University
8:30 AM Invited
Development of HT-LSCM Techniques for the In-situ Study of the Peritectic Phase Transition: Rian Dippenaar1; Dominic Phelan1; Mark Reid1; Stefan Griesser2; Suk-Chun Moon1; Dasith Liyanage1; 1University of Wollongong; 2Inteco
In-situ observation of solidification in a high-temperature laser-scanning confocal microscope is hampered by meniscus formation. In order to overcome this impediment, we developed a concentric solidification experimental technique to study in-situ, the progress of the peritectic phase transition in Fe-C alloys and steels. We create a small, stable, floating, liquid, pool within a thin cylindrically shaped disc-shaped specimen, supported by a solid rim. We then follow the progress of solidification and the subsequent phase transitions in-situ as a function of cooling rate. Solidification occurs within a steep temperature gradient and in order to quantify, and model, the progress of solidification, we measured experimentally, the exact temperature at the solid/liquid interface. In order to verify that observations on the surface are representative of bulk behaviour, we introduced a differential thermal analysis technique, by which we proved that our in-situ observations are indeed representative of bulk behaviour.
8:50 AM
Observation of Spinel Growth for Application in High Al-containing Steel Mold Fluxes: Il Sohn1; 1Yonsei University
Ultra-light advanced high strength steels containing Al greater than 1 mass pct. has been commercially developed, but the production of these new grade of steels are hampered by the limitation of the mold flux performance during continuous casting. Reactions of existing calcium-silicate based fluxes with Al-containing steels are thermodynamically favored resulting in lubrication and heat transfer issues in the mold. Recent developments in spinel-based mold fluxes to inhibit steel/mold flux reactions are discussed and the in-situ crystallization and growth kinetics of spinels as the primary crystal phase within non-reacting mold fluxes are described. Varying composition and cooling rates are employed in the confocal laser scanning microscope to control the spinel crystals in the CaO-Al2O3-MgO-based system at high temperatures.
9:10 AM
In-situ High Temperature Confocal Laser Scanning Microscopy Study during Heat Treatment of Duplex Stainless Steels: Wangzhong Mu1; Niklas Pettersson1; Sohei Sukenaga2; Hiroyuki Shibata2; Peter Hedström1; 1KTH Royal Institute of Technology; 2Tohoku University
It is well known that duplex stainless steels (DSSs) combine excellent mechanical properties and corrosion resistance due to their mixed microstructure of austenite and ferrite. The phase equilibria and kinetics of phase transformations at higher temperatures are important for the microstructure evolution during casting and welding. Therefore, in this work high temperature confocal laser scanning microscope is applied to investigate phase transformations in DSSs during heating and cooling. Five grades from lean to hyper DSS, i.e. 2101, 2304, 2205, 2507, and 3207, are used for the investigations. The effect of cooling rate on the starting temperature of phase transformation is investigated. Thereafter, the microstructure is studied by electron backscatter diffraction (EBSD) and x-ray diffraction (XRD). The results provide further insights in the high-temperature phase transitions in DSS and they support the further work to design new DSS grades with targeted microstructures.
9:30 AM Cancelled
Study on the Interaction Process between Mold Flux and TiN/TiO2 by Sessile Drop Method: Zihang Pan1; Lejun Zhou1; Wanlin Wang1; 1Central South University
The interfacial property is the key factor to determine the solubility and absorption of solid inclusions by mold flux in the continuous casting process. In this study, the interfacial interactions between slag droplet and TiO2, TiN substrates were investigated by sessile drop method. By processing the image of the experimental process, it could be found that the molten flux has a good wettability for both TiO2 and TiN substrates. A large number of bubbles were observed on the surface of the droplet during the reaction between the droplet and the TiN substrate, which indicated that TiN was oxidized by liquid mold flux. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to observe the reaction interface of the sample after the sessile drop test and the results showed that the final products of interfacial interaction between the slag droplet and TiO2 substrate are perovskites, and that for TiN substrate are also perovskites.
9:50 AM Break
10:10 AM Invited
MgO Dissolution Phenomena by Using Hot Thermocouple Technique: Yongsug Chung1; Jaewoo Myung1; 1Korea Polytechnic University
This study utilized the single hot thermocouple technique to examine the dissolution behavior of lumped magnesium oxide (MgO) in CaOAl2O3-SiO2 ternary slags. Results showed that the dissolution rate decreased as the Al2O3 content increased up to 20%. Over 20% Al2O3, MgAl2O4 was formed at the interface of MgO and it did not fully melt at 30% Al2O3. The dissolution behavior and the formation of MgAl2O4 were analyzed by a phase diagram provided by Factsage 7.0 software.
10:30 AM Cancelled
Investigation on the Titanium Extraction from Ti-bearing Slags based on Crystallization Modifications: Yongqi Sun1; Zuotai Zhang2; 1University of Queensland; 2Southern University of Science and Technology
High temperature Ti-bearing blast furnace slags account for an important secondary Ti resource where accurately modifying the crystallization phases containing Ti element makes up a significant strategy, via which the Ti is firstly enriched into a target phase and then separated from the base phases. Controlling the crystallization behaviors of the Ti-bearing phases is the decisive step, which could be modified through two main methods. The first one is to modify the chemical compositions of the slags using other materials or solid wastes and the atmosphere in order to modify the kind of phases. The second one is to modify the cooling process of the slags to enhance the growth of target Ti-containing phases. Both methods rely on the measurement of the crystallization of the Ti-bearing slags. Herein we investigated the crystallization of these slags and compared the results obtained using different methods including the single hot thermocouple technique.
10:50 AM
HT-LSCM as a Tool for Indirect Determination of Precipitates by Real Time Grain Growth Observations: Nora Fuchs1; Christian Bernhard1; Susanne Michelic1; Rian Dippenaar2; 1University of Leoben; 2University of Wollongong
The characterization of precipitation populations in steel with respect to their size distribution or volume fraction is still a challenge for even highly sophisticated analytical methods and hence, statistical data – absolutely essential for the verification of precipitation calculations - is still rare. The present paper aims at the use of HT-LSCM (High-Temperature Laser Scanning Confocal Microscopy) in-situ grain growth observations for the indirect conclusion on the precipitation or dissolution of AlN depending on initial aluminium and nitrogen content and thermal cycle. A formerly developed austenite grain growth model is applied to estimate the time-dependent Zener pinning and the results are finally used to adjust the relevant input parameters for the simulation of AlN precipitation kinetics in the commercial software MatCalc. The proposed paper will present first results and discuss the potential and limits of this efficient and time saving indirect method.
11:10 AM Cancelled
Real-time Imaging of Melting and Crystallization of Synthetic Ferronickel Slags with Varying B2O3 Content: Shifan Dai1; Wanlin Wang1; Lejun Zhou1; Tongsheng Zhang1; Jie Yu1; 1Central South University
In the production of mineral wool, the melting and crystallization behaviors of slag are the key issues to determine the final quality of mineral wool. In this study, three synthetic ferronickel slags with different B2O3 contents have been prepared, and the effect of B2O3 on the melting ranges of the slags has been investigated by Single Hot Thermocouple Technique (SHTT). Meanwhile, the isothermal crystallization characteristics of the samples were studied by high-temperature confocal scanning laser microscope (CSLM). The results showed that the initial and complete melting temperatures decreased with the increase of B2O3 content. Meanwhile, from the time- temperature-transformation diagrams, the crystallization incubation time increased with the increase of B2O3. The crystal morphology formed in the slags was columnar.