Effects Of Additives On The Properties Of Vitrified Bond

Alkaline metal oxides (Li₂O, K₂O), alkaline earth metal oxides (MgO, CaO, SrO and BaO) and ZnO, TiO₂, Bi₂O₃, CaF₂ were introduced to Na₂O-B₂O₃-Al₂O₃-SiO₂ basic vitrified bond respectively, and their effects on the main properties of the vitrified bond, including refractoriness, fluidity, thermal expansion linear coefficient (TELC), bending strength and microstructure of vitrified grinding tools, were investigated by using differential scanning calorimetry(DSC), thermal expansion linear coefficient determinator, three-point bending strength tester and scanning electron microscope (SEM). Moreover, the effects of the additives were further studied by means of Winkelmann TELC model and glass strucrural facor analysis.The experimental results showed the basic bond's refractoriness was greatly reduced, and the high temperature fluidity, the devitrification of vitrified bond and bending strength of grinding tool were improved with addition of Li₂O and K₂O separately. Li₂O had larger influence on those properties of vitrified bond than K₂O. Both Li₂O and K₂O induced the increase of TELC. The introduction of alkaline earth metal oxides made the bond's refractoriness decline and its fluidity increase at different degrees. They had effects on reducing the refractoriness and increasing the fluidity in the order of CaO>SrO>BaO>MgO. Except the obvious decrease of bending strength for grinding tools with more than 4wt% addition of SrO, the strengths of vitrified grinding tools with other alkaline earth metal oxides all had improvement to some extent. The strength increased as the following order, CaO>MgO> BaO>SrO. The introduction of ZnO, Bi₂O₃ and CaF₂ inclined to reduce the bond's refractoriness and increase its fluidity, while TiO₂ had contrary effect on the refractoriness and unconspicuous influence on the fluidity. The microstructure and strength showed little change when ZnO,TiO₂,Bi₂O₃ and CaF₂ was introduced respectively.Alkaline metal oxides had more obvious effects on the properties of vitrified bond than alkaline earth metal oxides, which on the other hand were more effective than ZnO,TiO₂,Bi₂O₃ and CaF₂. In a general, the addition of alkaline metal oxides should be around 5%, and it would be better about 2% for alkaline earth metal oxides.