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The effect of Sr2+ ions on the microstructure and high frequency properties of 2.5 wt% Bi2O3 added to Co(2)Z hexaferrites (3Ba(1-x)SrxO•2CoO•12Fe2O3, x = 0.0, 0.2, 0.4 and 0.6) synthesised using the solid-state reaction method was investigated. Experimental results indicate that the dielectric properties were markedly enhanced with the increase in the content of Sr2+ ions, thereby increasing the miniaturisation factor, which enables a size reduction in a long frequency range. Slight changes to saturation magnetisation (Ms) and coercivity (Hc) were observed, i.e., the saturation magnetisation (Ms) decreased from 39.99 to 38.11 emu/g, and coercivity (Hc) increased from 59.05 to 65.21 Oe when x increased from 0.0 to 0.6. Meanwhile, ε′ increased from approximately 8 to 12, indicating the invariability in μ′. In addition, the processed materials exhibit relatively low magnetic loss and dielectric loss (magnetic loss tanδμ ≈ 0.08 and dielectric loss (tanδε ≈ 0.007)). These results indicate that the substituted CO(2)Z ferrites have excellent potential in high-frequency antenna applications.

The annual cumulative quantity of high and medium alloy steel scrap has exceeded 10 million tons. Using the traditional smelting process involving electric arc refining in a smelting furnace for these scraps causes high percentages of alloy losses, which decreases the value of the alloy steel scrap and poses environmental threats. Existing studies have rarely focused on separate smelting of the scrap and oxidation behaviors of the alloying elements. Therefore, this study proposes an induction melting and electroslag remelting scheme to process the scrap. Based on this scheme, the effects of the temperature, oxygen content, and element contents on the recovery percentages of the alloying elements were investigated using pilot experiment and thermodynamic analysis. The experimental results showed that the alloying elements (tungsten, chromium, nickel, molybdenum, and vanadium) exhibited recovery percentages of 97.36%, 94.62%, 97.63%, 95.09%, and 89.49%, respectively; furthermore, the impurity content did not increase during smelting. The thermodynamic analysis indicated that an increase in carbon content improved the oxidation resistance of the alloying elements except for nickel, whereas the increases in the contents of oxygen and alloying elements increase their oxidation. Steam partial pressure and air suction dramatically increase the concentrations of nitrogen, hydrogen and oxygen. This scheme is an alternative for smelting medium and high alloy steel scrap, and the thermodynamic analysis provides a theoretical understanding of the oxidation behaviors of the alloying elements in the steel scrap and the control of impurity.

To reduce energy and resource consumption, high-strength hot-rolled rebars with yield strengths of ≥400 MPa (HRB500) and ≥500 MPa (HRB600) have been designed and produced in recent years. Optimizing the microstructure in the steel to improve strength necessitates determining the kinetics of the phase transition of austenite to polygonal ferrite. Therefore, in the study, the effect of temperature and holding time on the volume fraction of ferrite is investigated in HRB500 and HRB600 steels. Experimental results show that the ferrite percentage initially increases with an increase in temperature and then decreases as the temperature increases from 600 to 730 °C. The optimum temperature range is 680–700 °C for HRB500 steel and 650–680 °C for HRB600 steel. Based on the Johnson–Mehl–Avrami equation, phase transition kinetic models are established. Model predictions are consistent with the validation data. Thus, this study establishes a reference for studying ferrite formation during cooling.