An effective strategy for preparing fluxed metallized pellets from converter slag: Synergistic mechanism and consolidation behavior

Abstract

A systematic study was conducted on the preparation and metallurgical properties of fluxed metallized pellets from converter slag, focusing on the consolidation behavior and interfacial reactions during the preparation process. The optimal preparation parameters were determined to be a preparation temperature of 1200 °C, a roasting time of 2 h, a basicity of 1.5, and an FC/O ratio of 0.8. Under these conditions, the prepared fluxed metallized pellets exhibited a compressive strength of 4125 N/P, an RDI_+3.15 of 75.2 %, and an RDI_+3.15 of 65.2 %. The results indicated that higher roasting temperatures and basicity levels promoted the formation of stable, low-melting-point phases such as gehlenite and olivine. These phases enhanced the crystalline and adhesive structures, thereby increasing the compressive strength of the fluxed metallized pellets. In addition, variations in the compressive strength as an important metallurgical indicator were closely related to the formation of wustite and olivine at lower basicity levels. Higher basicity facilitated the formation of dicalcium silicate (C₂S), whose phase transition-induced volume expansion caused self-pulverization of the pellets during the cooling process. The presence of solid solutions phases, such as gehlenite (Ca_xMg_2-xSiAl₂O₇) and olivine (Ca_xFe_2-xSiO₄), played an important role in preventing fragmentation and pulverization, effectively improving the RDI_+3.15 and RDI_+6.3 values of the pellets. The preparation and metallurgical properties of the fluxed metallized pellets meet the evaluation criteria for feed materials used in the ironmaking process in blast furnaces.