Preparation and processing parameter research of high basicity steel slag-based glass-ceramics with one-step sintering process

High basicity (CaO/SiO₂ mass ratio) glass-ceramics were prepared to improve the usage of high calcium metallurgical slags in raw materials. Glass-ceramics with a high basicity of 0. 9 were prepared using steel slag as the main raw material through one- step sintering process. The influences of heat treatment on the microstructure, linear shrinkage, bulk density and bending strength of glass-ceramics were investigated by X-ray diffraction, scanning electron microscopy and performance testing. The results show that one-step sintering process is suitable for preparing high basicity glass-ceramics. The sintering process of the glass-ceramics is basically completed after heat treatment at 1100℃ for 120 min, with the largest bulk density of 2. 4 g·cm^-3 and the optimal bending strength of 56.4 MPa. The main crystalline phase of the glass-ceramics is gehlenite and the secondary crystalline phase is augite. The nucleation and crystallization process is completed in the heating process, while in the heat preservation process the sintering densification and crystal growth are dominant. After heating to 1100℃ and holding for 30 min, the bending strength of the glass-ceramics exceeds 45 MPa. Columnar crystals are intertwined together to form the crystal skeleton which constitutes the microstructure with residual glassphase inside the glass-ceramics. Besides, the linage shrinkage, bulk density and bending strength of the glass-ceramics increase with the increasing of holding time. The crystal morphology transforms from spherical particles and short columns into long rod-like columns with the increasing of holding time, while the crystalline phase content stays constant. The crystal morphology of the glass-ceramics and the integrated dense microstructure formed by the crystals and the residual glass phase are two primary factors of the improvement in mechanical properties of the glass-ceramics.