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Induration of Green Pellets
Published in Ram Pravesh Bhagat, Agglomeration of Iron Ores, 2019
The addition of MgO helps in improving the high-temperature properties of the pellets. The temperature at which dissociation takes place with MgO additions happens to be the lowest among the additives.[12] Dolomite, as a source of MgO, may not be preferable as it releases CO2 during its dissociation, resulting in the formation of pores and weakening of the strength on firing. Besides, the crystal size of dolomite is larger; hence, its calcination takes more time (see Secs. 6.8.3 and 9.5.2). In place of dolomite, light burned magnesite[13] and pyroxenite, a magnesium silicate mineral,[14] have been attempted as additives for pellets. Unlike dolomite, these additives do not undergo any endothermic reactions for dissociation. The pyroxenite either reacts with the surrounding iron oxide to form magnesioferrite or is assimilated in the silicate melt that acts as a bonding phase in the pellets. These pellets exhibit less swelling by forming low FeO high melting slag that gives sufficient bond strength to withstand the reduction stresses. Pyroxenite pellets result in better softening-melting characteristics compared to acid pellets due to the formation of high melting point slag and the magnesiowustite phase during reduction.
NaCl and Na2SO4 solution effect on weathering steel visual appearance when the ambient temperature changes cyclically
Published in Cogent Engineering, 2019
Mindaugas Daukšys, Evelina Bitautaitė, Jūratė Mockienė, Dalia Nizevičienė
The protection ability inherent in weathering steel can be affected by the environment in different kind of atmospheric particles rich urban atmospheres (Aramendia, Gómez-Nubla, Castro, & Madariaga, 2014). The presence of atmospheric particles of calcium carbonate does not have a significant negative role in the metal decay process. However, the presence of high magnesium calcite plays an important role in the formation of magnesioferrite, another deleterious product present in the surface of the weathering steel. As all these sulphates are soluble, rain water can dissolve them leading into a continuous decaying and material loss process. Other atmospheric particles such as calcite, charcoal, and chromium rich particles were detected together with several compounds produced in the reaction of steel and deposited particles with acid gases of the atmosphere (Aramendia, Gomez-Nubla, Castro, & Madariaga, 2015b; Nishimura et al., 2000). These particles have a negative effect on the conservation of weathering steel because the change the visual appearance of steel surface and decrease its resistance to atmospheric agents. Chiavari et al. (2012) concluded that pre-patination had no beneficial effects on corrosion of Cor-Ten with different surface finish. Corrosion rate of weathering steel is considerably lower than that of the standard carbon steel. Nevertheless, the possible effect of corrosion on reliable service of the structure throughout the designed service life should be considered when designing the structures (Křivý, 2012; Křivý & Konečný, 2013; Urban, Krivy, & Kreislova, 2015).
Metallurgical resource recovery from waste steelmaking slag from electric arc furnace
Published in Environmental Technology, 2023
Unlike other slags, the iron in EAFSs do not form silicates but usually exist as wustite (FeO), haematite (Fe2O3), magnetite (Fe3O4), magnesioferrite (MgFe2O4), etc. [27]. Atmosumarto and Standish [28] proposed that CaO can replace the FeO in silicates in the slag according to Equations (12) and (13). Thus, there is a need for CaO in the slag to free up FeO from the silicates.
Ironworking slags from Late Iron Age sites in Hungary - composition, microstructure and function
Published in Materials and Manufacturing Processes, 2020
On the basis of XRD results, we can state that slag sample 11 from Jászberény is altered. The presence of lepidocrocite suggests an alteration during forging. Goethite is the result of supergene alteration under the action of soil fluids and oxidation by air. Magnesioferrite is the result of the application of the Search/Match algorithm, however, the EDS identified Mn-bearing magnetite, but this phase is not present in ICDD databases. It is worth mentioning the lack of the amorphous phase.