Effect of B <sub>2</sub> O <sub>3</sub> /SiO <sub>2</sub> molar ratio and B <sub>2</sub> O <sub>3</sub> content on viscosity and structure of B <sub>2</sub> O <sub>3</sub> –SiO <sub>2</sub> –Al <sub>2</sub> O <sub>3</sub> –Na <sub>2</sub> O–TiO <sub>2</sub> glass lubricant
Lei Cui, Wei Lv, Peiyuan Ni, Huailiu Wang, Ying Li
Abstract
Abstract Glass lubricant with a suitable viscosity is essential for producing high‐quality titanium products by the hot extrusion process. In this study, a novel lubricant of B 2 O 3 –SiO 2 –Al 2 O 3 –Na 2 O–TiO 2 (BSANT) glass was proposed, where the effects of B 2 O 3 /SiO 2 molar ratio (B/Si) and B 2 O 3 content on viscosity and structure were investigated. The results showed that the BSANT glass viscosity was gradually decreased, and the viscous activation energy was decreased by 20.24% with an increased B/Si ratio from 0.415 to 0.719. This was attributed to the decreased amounts of Q 3 , [BO 4 ], [AlO 4 ], and bridging oxygen (BO) in the network structure, which in turn resulted in a decreased network degree of polymerization. When B 2 O 3 content was increased from 18.70 to 33.12 mol.%, the melt viscosity value at 950 ℃ was decreased by 64.51%, and the viscous activation energy was reduced by 15.82%. Boron anomalies were also observed in glass melts with the B 2 O 3 content from 28.28 to 33.12 mol.%. The mechanisms responsible for this phenomenon were thoroughly discussed in the study. Additionally, a comparison and discussion of the applications of glass lubricants in metal hot working were presented. A glass lubricant with a specific composition was recommended for use in hot extrusion process within the temperature range of 950–1100°C due to its relatively stable viscosity properties.