Characterization of Minerals, Metals, and Materials: Ferrous Metals
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Shadia Ikhmayies, Al Isra University; Bowen Li, Michigan Technological University; John Carpenter, Los Alamos National Laboratory; Jian Li, CanmetMATERIALS; Jiann-Yang Hwang, Michigan Technological University; Sergio Monteiro, Military Institute of Engineering ; Firrao Donato, Collegio Universitario, Italy; Mingming Zhang, ArcelorMittal Global R&D; Zhiwei Peng, Central South University; Juan P. Escobedo-Diaz, UNSW Australia; Chenguang Bai, Chongqing University; Eren Kalay, METU; Ramasis Goswami, Naval Research Laboratory; Jeongguk Kim, Korea Railroad Research Institute
Wednesday 2:00 PM
March 1, 2017
Location: San Diego Convention Ctr
Session Chair: Firrao Donato , Politecnico di Torino - DISAT; Mingming Zhang, ArcelorMittal Global R&D
Effects of Alumina and Magnesia on Microstructure and Mineralogy of Iron Ore Sinter: Mingming Zhang1; Marcelo Andrade1; 1ArcelorMittal Global R&D
The evolution of microstructure and mineral phases in iron ore sinters have been investigated by X-ray diffraction, optical microscope and scanning electron microscope. It was found that sinter Al2O3, basicity and MgO together with thermal conditions during sintering play an important role in the formation of mineral phases and microstructure in sinter. The low Al2O3 (<2.0 wt%), medium MgO (2.0-2.5 wt%) and high basicity (>3.0) sinter showed higher Tumbler strength, and higher low temperature degradation index (LTD) due to the presence of silico ferrites of calcium and aluminium (SFCA), and magnetite phase, and lower pore phase as compared to low basicity iron ore sinter. The physical and metallurgical properties of sinter improved with increase in solid fuel for higher alumina and magnesia sinter.
2:20 PM Cancelled
Isothermal Reduction Kinetics of CaO·2Fe2O3 by Thermogravimetric Analysis: Chengyi Ding1; Xuewei Lv1; Senwei Xuan1; Kai Tang1; Yun Chen1; Jie Qiu1; 1Chongqing University
Isothermal reduction kinetics of CF2 by 30% CO and 70% N2 at 1123 K , 1173 K and 1223 K was investigated by TGA in this study. The reduction rate analysis indicated that reduction of CF2 comprises three stages during the whole reduction process, Apparent activation energy of samples CF2 reduction is 34.37 kJ/mol. The ln-ln analysis implied the reduction of CF2 was expressed initially by a 2D subsequently by 3D shrinking layer reaction.
Phase Transformation of MnO2 and Fe2O3 Briquettes Roasted under CO-CO2 Atmospheres: Bingbing Liu1; Yuanbo Zhang1; Zijian Su1; Guanghui Li1; Tao Jiang1; 1Central South University
With the depletion of rich manganese ores, high-Fe content manganese ores are becoming the mainstream resources for manganese extraction. Reduction roasting-magnetic separation process is reported as a relatively effective route to realize the separation of manganese and iron. This study investigated the phase transformation of MnO2 and Fe2O3 briquettes (molar ratio 1:1) roasted under various temperatures and CO-CO2 atmospheres. Results showed that when the CO content was in the range of 0-10 vol.%, MnxFe3-xO4 (x=0-1) phase was formed and its content increased with the rising of temperature. The formation of ferromagnetic MnxFe3-xO4 with strong magnetism resulted in an inferior separation of manganese and iron by magnetization roasting-magnetic separation process. With the increase of CO content to over 25 vol.%, the MnxFe3-xO4 content decreased while the content of feebly magnetic substance (MnO)y(FeO)1-y(y=0-1) increased. Further increasing the CO content to over 80 vol.%, (MnO)y(FeO)1-y was reduced to MnO and metallic iron.
Application of X-ray Computed Tomography for the Characterization of Graphite Morphology in Compact-graphite Iron: Dileep Singh1; Chih-pin Chuang1; John Hryn1; Jonathan Almer1; Peter Kenesei1; Richard Huff2; 1Argonne National Laboratory; 2Caterpillar, Inc.
Properties (mechanical, thermal, castability) of cast irons are strongly dependent on the graphite content, distribution, and its morphology. In the present study, high-energy x-ray tomography technique was used to characterize the graphite morphology of compact graphite iron. The size, shape, spatial connectivity and structure of different graphite morphologies were examined in 3D using computer-aided image analysis. In addition, nodularity analysis was performed in 3D and the results are compared to the traditional 2D technique. It is found that the variation of nodularity within 2 mm of the sample diameter from 2D analysis can be as high as 20 and the averaged nodularity (2D) is ~ 8% lower than that from 3D analysis. The size distribution of spheroidal graphite shows a tri-modal distribution, which suggests a multi-step nucleation process during solidification.
Nitrogen Quantification in Steels by Atom Probe Tomography: Raphaele Danoix1; Mohamed Gouné2; Andrius Martinavicius1; Hugo Van Landeghem3; Frederic Danoix1; 1CNRS - Université de Rouen; 2ICMC Bordeaux ; 3SIMAP Grenoble
Atom probe analysis is recognized as a key method for measuring compositon variations in materials down to the nanometer scale. Even if its mass resolution allows identification of of all chemical species, some uncertainties remain when two or more elements have common isobares or mass to charge ratio. In this situation, the mass resolution necessary for separating the contribution of each specy on mass spectum peaks is several thousands, significantly higher than that of the current instruments (about one thousand). One particularly important such case in physical metallurgy is nitrogen (14), silicon (28) and iron (56), making it particularly difficult to measure iron- or silicon-nitride compositions, or nitrogen content in the matrix of Si bearing steels. In this presentation, we propose several possible ways to, at least partly, overcome this problem, in particular by using 15N isotopicaly enriched nitrogen.
3:40 PM Break
Effect of Grain Boundary Plane on the Sensitization of Austenitic Stainless Steel: Matthew Hartshorne1; Christopher Barr1; Mitra Taheri1; 1Drexel University
Austenitic stainless steels are widely used across the petrochemical, nuclear and renewable energy industries. However, exposure to elevated temperatures can sensitize these steels, limiting their service lives. Sensitization is caused by the precipitation of secondary phases such as chromium carbides at grain boundaries, however grain boundary engineered microstructures have been shown to mitigate this. Grain boundary engineered stainless steels rely on high fractions of low energy grain boundaries, such as ∑3n, however not all of these grain boundaries resist sensitization to the same degree. Experiments will be presented utilizing EBSD stereology and serial sectioning in conjunction with bulk corrosion testing on multiple grain boundary engineered microstructures. TEM and APT will be utilized to correlate the corrosion resistance of specific grain boundaries to both their misorientation and grain boundary plane, illustrating the importance of coherent twin boundaries to corrosion resistance in austenitic stainless steels.
Effect of Binder Phase on Reduction Swelling Property of Iron Ore Pellet: Xiaozhe Wang1; Jian Liang Zhang2; Zhengjian Liu2; Xingle Liu2; 1University of Science and Technology Beijing; 2University of Science and Technology Beijing
The effect of alkalis silicate binder phase on the swelling property of pellets during reduction was studied in this paper. The results indicated that the thermal and chemical stability of alkalis silicate binder phase were poor especially when the phase included fluorine and its melting point sharply decrease to about 600℃. The work presented the swelling index (SI) increased by decreasing melting point. The reduced samples were examined by scanning electron microscope (SEM), energy dispersive spectrometer (EDS) and optical microscope. The SEM and optical microscope results showed that the bonding phase contained alkalis in the pellet became liquid during reduction and flew into the cracks or pores caused by the volume expansion due to rupture of iron oxide crystal or iron whisker growth, thus lost its bonding force to resist the stress. This phenomenon would lead to abnormal swelling and reduced permeability of packed beds of blast furnace.
Important Factors to Consider in FIB Milling of Crystalline Materials: Jian Li1; Pei Liu1; 1CanmetMATERIALS
In recent years FIB has become an important microscopy and microanalysis instrument. In the field of materials research, it has been widely used to perform ion beam sectioning and site-specific TEM specimen preparation. However, there has been lack of understanding of FIB induced artifacts. Gallium ion beam damage and the specimen heating during FIB milling can produce unwanted artefacts during FIB work. Calculations of maximum specimen temperature increase have mostly been based on the assumption that ion beam implantation into substrate of infinite size. This deviates from finite specimen volume in FIB TEM specimen preparation that impedes heat dissipation. In this paper, the authors will summarize common FIB artifacts and make an effort to discuss the concerns of specimen temperature rise in FIB specimen preparation process.
Estimation of Dislocation Density in Metals from Microhardness Test: Ali Ameri1; Nancy Elewa1; Juan Escobedo-Diaz1; Mahmud Ashraf1; Paul Hazell1; 1University of New South Wales-Canberra
This paper presents a newly calibrated technique to estimate the dislocation density of cubic metals using microhardness test. This method is based on the formation of Generally Necessary Dislocation (GND) due to indention size effect (ISE) phenomena during small indention (less than 1μm), and strengthening mechanisms of the material at the micro-level. The performance of the proposed technique has been validated using experimental results obtained for both phases of lean duplex stainless steel 2101 (LDSS2101) alloy. X-Ray diffraction profile for LDSS 2101 was utilized to validate the results of the suggested technique by using the Modified Williamson-Hall and the Modified Warren-Averbach methods. In addition, available experimental data on microhardness and dislocation density of different pure metals were used for further validation of the proposed technique. It is observed that the suggested approach may be used as a general technique to estimate the dislocation density with reasonable accuracy.
Contact Angle of Iron Ore Particles with Water: Measurements and Influencing Factors: Kai Tang1; Senwei Xuan1; Wei Lv1; Xuewei Lv1; Chenguang Bai1; 1Chongqing University
The contact angle between six iron ores and water were determined by the capillary pressure method with cyclohexane as the perfect wetting liquid. The factors influencing the contact angle were discussed, and a relationship between the content of oxy–hydroxides and the contact angle of iron ores was obtained. The results show that the ore F has the lowest contact angle but the ore D get the biggest, which are 32.09 o and 78.16 o, respectively. The volume fraction of oxy–hydroxides is linearly dependent on the contact angle. The contact angle decreased with increasing the volume fraction of Fe2O3•H2O.