Abstract
To clarify the effect of niobium (Nb) on the changing behavior of oxide inclusions in alloys containing different concentrations of Mn, Si, and Nb, heat treatment experiments at 1473 K were conducted and changes in the morphology, size, quantity, and composition of these inclusions were investigated. The stability of the oxide inclusions in both molten and solid Fe-Mn-Si-Nb alloys was also estimated by thermodynamic calculation using available data. Results showed that the change in the composition of the oxide inclusions owing to heat treatment depended on the concentrations of Nb and Si in the alloy. MnO-SiO2-type oxide inclusions gradually transformed into MnO-Nb2O5-type or MnO-SiO2- & MnO-Nb2O5-type inclusions in low-Si and high-Nb alloys after heating for 60 min. However, the shape of the inclusions did not change clearly. It was indicated that, during the heat treatment at 1473 K, an interface chemical reaction between the Fe-Mn-Si-Nb alloys and the MnO-SiO2-type oxide inclusions occurred according to the experimental and calculation results.
Highlights
By oxide metallurgy technology, fine and dispersed non-metallic inclusions in steel could distribute around austenite boundaries to restrain grain growth and act as heterogeneous nucleus to promote acicular ferrite, which are able to greatly improve the mechanical properties of steel [1,2,3,4]
Shibata et al [5] reported that, in the Fe-Cr alloy containing 10 mass % Cr, MnO-SiO2 -type inclusions transformed into MnO-Cr2 O3 -type inclusions with a low Si content (0.3 mass %), the MnO-SiO2 -type inclusion was stable
Due to the high cooling rate and small size of the alloy specimen, concentrations of Mn, Si, and Nb were firstly confirmed to be homogeneous by using an Electron Probe Microscopic Analyzer (EPMA) (JEOL, Tokyo, Japan) whose primary importance is the ability to acquire precise, quantitative elemental analyses at very small “spot” sizes, primarily by wavelength-dispersive spectroscopy (WDS), and measured and verified by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES)
Summary
Fine and dispersed non-metallic inclusions in steel could distribute around austenite boundaries to restrain grain growth and act as heterogeneous nucleus to promote acicular ferrite, which are able to greatly improve the mechanical properties of steel [1,2,3,4]. Heat treatment is a new approach to precisely controlling and optimizing the physicochemical characteristics of non-metallic inclusions in steel and greatly expanding the application of oxide metallurgy technology in steel production, which is attracting more and more attention. Shao et al [7] confirmed that shape variation of slender MnS was greatly influenced by the heating rate. As heating rate rose from 0.5 to 2 K/s, the amount of split MnS decreased; while the heating rate exceeded 6 K/s, the slender
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
