Deyong Wang

Effect of Modification Treatment for Reduction of Dephosphorization Slag in Hot Metal Bath

To extract the valuable elements from the steel slag, a novel approach has been proposed by modification treatment to provide the stronger driving forces and accelerate the reduction. Three types of dephosphorization steel slags were reduced using carbon-saturated iron bath to extract iron and phosphorus simultaneously. During the process of reduction, slag composition, temperature, and original P2O5 content were investigated respectively. Slag modification treatment, adding either silica or alumina to vary the slag composition, was proven to accelerate the reduction of dephosphorization slag. The equilibrium time can be shortened from 60 to 30 min. Slag modification also allowed the reduction reaction to occur at lower temperature. After slag modification, the original P2O5 content in slag presents a slight difference on reduction process. Almost half of the reduced phosphorus was vaporized within 5 and 20 min. As more and more FeO was reduced, CO gas generation decreased, and evaporation amount of phosphorus therefore decreases.

Effect of Magnesium on Evolution of Oxide and Sulphide in Liquid Iron at 1873 K

To reveal the effects of magnesium on the evolution of oxide and sulphide inclusions in liquid iron, both thermodynamic calculations and deoxidization experiments were carried out. The samples extracted from the liquid iron were polished and analyzed by optical microscopy and scanning electron microscopy. The results showed that magnesium could modify oxide and sulphide inclusions simultaneously. Spherical MgO and irregular spinel inclusions were observed in the samples. The elongated MnS inclusions were replaced by small MgO • MgS or MgO • MgS • MnS complex inclusions, and the sulphides were distributed dispersively. The evolution mechanisms of inclusions were discussed comprehensively, and a proposed model for the formation of oxysulphide was set up.

Modification of Inclusions in Liquid Iron by Mg Treatment

Effect of Mg addition on the compositions of inclusions were studied. The results show that Mg can minimize the inclusions of steel obviously. Under the present condition, Mg deoxidation products of low-S content experimental steel would be changed in the order of Al2O3→MgAl2O4→Mg→Al–O–S→Mg–O–S. Mg deoxidation products of high-S content experimental steel generate Mg–S(–O)+MnS type inclusions, except for usual oxysulfide. And it is consistent with the results of thermodynamics calculation. Mg is preferred to react with oxide, compared with sulfide. The reaction reaches the equilibrium after 1 min or 5 min. It shows that the number and diameter of inclusions in all experimental steel samples are well under control, helping to improve the properties of steel.

A Coupling Dynamic Model for Dissolution and Reduction of Chromium Ore in a Smelting Reduction Converter

For describing and resolving the process of chromium ore smelting reduction in a converter preferably, the coupling dynamic model was established based on the kinetic models of chromium ore dissolution and interfacial reducing reaction between the slag and metal. When 150 t stainless steel crude melts with chromium of 12% are produced in a smelting reduction converter with no initial chromium in metal at 1 560 °C, the results of the coupling dynamic model show that the mean reduction rate and injection rate of chromium ore are 0. 091 % • min−1 and 467 kg • min−1, respectively. The foundation of the coupling dynamic model provides a reference and basis on the constitution of rational processing route for a practical stainless steelmaking.

Characteristic Analysis of Solidified Crust for Basic Tundish Flux With Al-Killed Steel Casting

The solidified crust was harmful to Al-killed steel casting using a basic tundish flux. After sampling from an actual tundish, XRD, SEM and EDX examinations were carried out to analyze the microstructure of solidified crusts. The conclusions were obtained as follows: main crystallization phases existing in tundish crust were Ca12A14O33, Ca2SiO4 and a little spinel; spinel and Ca2SiO4 distributed between the grain boundaries of Ca12Au14O33, which increased the connection strength of crystallization phases by pinning grain boundary, density or hardness of solidified crust maybe also significantly increases; when initial composition of tundish flux was located in spinel region of CaO-SiO2-Al2O3-10%MgO phase diagram, it was easier to precipitate spinel from molten slag; three approaches of spinel formation in flux were summarized. When flux was saturated with magnesia on the metal/flux interface, MgO in flux was reduced by dissolved aluminum and then formed spinel. On the interface of steel/refractory, with feasible aluminum content, it was also easy to form spinel, and spinel inclusions will be floated and captured by tundish flux.