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Electric arc furnace steel slag was modified by wastes in hot-stage process with the aim to improve the cementitious activity. Effect of basicity on cementitious activity of modified steel slag was investigated in this research. The modified slag was characterized by XRD, DTA and Raman spectra techniques to investigate the correlations between structural features and the cementitious activity. The results showed that modified steel slag with a basicity index of 1.67 possessed the highest activity index, 107%, due to the precipitation of Belite, high content of amorphous phase and low polymerization degree. The polymerization degree of modified slag was demonstrated by nonbridging oxygen per tetrahedrally coordinated cations value which was calculated through curve-fitted Raman spectra. The value of modified slag increased as the basicity promoted from 1.05 to 1.67, indicating a lower degree of polymerization. Modified slag with a basicity index of 1.86 possessed the poor cementitious activity mainly because of the significant decrease of glass phase content.

There are always differences between the magnetic properties (core loss and magnetic induction) of the head and those of the tail, with the same chemical composition, in a medium-grade non-oriented silicon steel coil (or MGNO for short). To work out the reason leading to the differences and get methods to increase the magnetic properties, this paper studied the types and the distribution of the inclusions in MGNO, and the effects of the inclusions on the magnetic properties of the MGNO, by using SEM + FEEM observation and statistic analysis. The results show that there are oxide inclusions, sulfide inclusions, nitride inclusions and composite inclusions in the MGNO. More inclusions shorter than 500 nm are bad for the magnetic properties of the MGNO. On a lower order of the sizes, the number of the inclusions would more obviously affect the MGNO on its magnetic properties. The Al2O3 shorter than 1 µm and the MnS whose size is 100∼500 nm are the main inclusions that decrease the magnetic properties of the MGNO. In order to get better magnetic properties of the MGNO, the steelmaking process and the hot rolling process should be improved, chiefly the RH and the heat furnace.

This experimental investigation was aimed at studying the influences of 21∼36% oxygen concentrations on the heating rate, emissions and temperature distributions. In consideration of the actual needs, 1300 °C was selected for the heating temperature of flue gas. When the billet was taken out from furnace, the billet core temperature were about 1200 °C, and the temperature difference between the billet surface and core fluctuated between 10 to 50 °C. At the same time, in order to ensure the quality of billet and save energy and cost, the heating temperature and oxygen concentration in furnace should not be too high. Increasing the oxygen concentration led to higher heating rate due to lower level of the inert gas (N2) in the combustion air. When the oxygen concentration was increased from 21% to 36%, the heating rate of flue gas was increased by 68.3% in the heating test, and the heating rate of billet core was increased by 39.5%. Higher oxygen concentration yielded higher flame temperature. Hence, the NOxconcentration increased with increasing oxygen concentration. Moreover, the generation of NOxconcentration was faster and more under the excess oxygen at higher oxygen concentration levels. The NOxconcentration is very low and the highest NOxconcentration is only 27.2 ppm even at the highest oxygen concentration under flue gas cycle combustion conditions. Under the graded oxygen combustion and concentrated oxygen combustion conditions, the higher the oxygen concentration, the greater the difference in NOxemission concentration. The concentration of NOxin the graded oxygen supply is relatively low. Additionally, Numerical Simulations indicated that the temperature distributions became progressively nonuniform with increasing oxygen concentration because the absorption coefficient and convective heat transfer coefficient were altered.