Yuanchi Dong

Performance of Low Fluoride Dephosphorization Slag of Hot Metal

The purpose of the study is to decrease content of CaF2 in dephosphorization slag. The dephosphorization effects of CaF2 replaced by B2O3 were investigated. The dephosphorization experiments were carried out at 1450 °C in air atmosphere. The results show that the melting points and dephosphorization ratios change little when CaF2 was replaced by B2O3. The dephosphorization ratios are all greater than 80% and melting points can meet the requirement of hot metal pretreatment. Because of the change of alkalinity caused by B2O3, the oxidation of slag increases with increasing of B2O3 contents. It is beneficial to pre-dephosphorization. As a result, for decreasing its pollution, CaF2 can be replaced by B2O3 to dispose fluoride-free pre-dephosphorization slag.

Thermodynamic Properties of Fe-C-N and Fe-C-B-N Melts

The saturated solubility of carbon and nitrogen in Fe-C-N and Fe-C-B-N melts was measured experimentally at 1 485 °C to obtain the activity interaction coefficients between components in these melts. A new method was used to treat experimental results. Using thermodynamic derivation and calculation, some important interaction coefficients between components in these melts were obtained.

Separation of ZnO from the Stainless Steelmaking Dust and Graphite Mixture by Microwave Irradiation

Abstract In this study, microwave was used to treat stainless steelmaking dust containing zinc oxide. The effects of heating time, carbon content and zinc oxide content on the removal efficiency of zinc oxide and the reduction efficiency of iron oxide were investigated. Experimental results show that, for the sample with 16% (mass percent, the same below) graphite heated for 10 minutes by 10 kW power microwave, the removal efficiency of zinc oxide is between 80% and 90% and the metallization ratio of iron oxide is between 40% and 60%; Initial zinc oxide content has a slight effect on the removal efficiency of zinc oxide. The results indicate microwave treatment is one of the feasible ways to process metallurgical solid waste containing the metal with low boiling point.

Size analysis of slag eye formed by gas blowing in ladle refining

The formation of slag eye in a gas stirred ladle was studied through cold models and industrial trials. In the cold model, water and sodium tungstate solution were employed to simulate liquid steel, and silicon oil was employed to simulate slag. The simulation results revealed that the gas flow rate and bath height had strong effects on the slag eye size. In particular, the thickness of slag layer played a strong role in the slag eye size. In addition, the slag eye could not be formed when the thickness of the top layer was more than 4 cm in water-silicone oil model. Besides, the section area of vessel had a great impact on the slag eye size. Industrial trials results showed a similar trend that the gas flow rate was very significant on the slag eye size. The predictions of the existing models showed larger predictions deviations compared with the experimental data. Moreover, a new model without fitting parameters was developed based on force balance and mathematical derivation, and verified by the experimental data. The new model provides the prediction with small deviations by comparing with the data acquired from cold models and industrial trials.

Thermodynamic Analysis of V-concentrating Phase Formation in V-bearing Steelmaking Slag Modified by MgO

Abstract In the study, magnesium oxide acting as modifier was added to V-bearing steelmaking slag to concentrate vanadium, and then the effect of magnesium oxide on the formation of V-concentrating phase during cooling was investigated. Experimental results show that, in the case of the original slag, di-calcium silicate along with most of vanadate and phosphate in the slag forms solid solution, calcium ferrite which contains small part of vanadium in the slag and matrix without vanadium in turn precipitate during slowly cooling; For the sample with 8% MgO addition, two new phases (merwinite and V-concentrating phase) generate during slowly cooling, and the amount of di-calcium silicate decreases. Merwinite phase doesn’t contain vanadium, and V-concentrating phase (Ca3(V,P)2O8·nCa2SiO4) contains 17–19% V2O5 by mass; For the sample with 16% MgO addition, another new phase (monticellite) precipitates from liquid slag, the phase of di-calcium silicate disappears, and most of vanadium concentrates in V-concentrating phase-Ca3(V,P)2O8·nCa2SiO4 (18–21%V2O5).

Thermodynamic Model for Calculating Activity of Nitrogen and Boron in Fe-C-B-N Molten Metal

The solubility of nitrogen in Fe-C-B-N system was measured at 1 758 K, and the computational model on activity (action concentration) of nitrogen and boron was established based on phase diagram and the coexistence theory about metal melt structure model. Comparing the computed results with the experimental results, satisfactory conclusion can be obtained. The result shows that BN and B4C can exist in Fe-C-B-N molten metal at high temperature, which consequently restrains the nitrogen removal from the melt. However, B4C content is extremely low. Before graphite is precipitated, the influence of carbon on activity of nitrogen in melt is higher in ternary system than in binary system; however, this effect is contrary to that after graphite is precipitated.

Existence of a solid solution between 3CaO · V2O5 and 3CaO · P2O5

In the present work, a solid solution of 3CaO · V2O5 and 3CaO·P2O5 was found below 1573 K. The solution could be described as 3CaO+xV2O5+(1−x) P2O5. The solid solutions at three compositions, namely, X=1/3, X=1/2, and X=2/3, were synthesized. X-ray diffraction (XRD) patterns revealed that the crystals exhibited a rhombohedra structure. X-ray indexes at these compositions were reported.