CRYSTALLIZED GLASS FOR SUBSTRATE OF MAGNETIC HEAD OR MAGNETIC DISC AND ITS PRODUCTION

PURPOSE:To obtain a crystallized glass for substrate, improved in processability by crystallizing and heat-treating glass raw materials obtained by adding one or more oxides of Al2O3, ZnO, CaO and Fe2O3 to Li2O and SiO2 of a specific ratio of Li2O/SiO2 and melting and solidifying the mixture and depositing the resultant crystal. CONSTITUTION:0.5-5wt.% one or more oxides of ZrO2 and TiO2 as a nucleus forming agent or 0.001-0.01wt.% one or more metals among Pt, Au an Ag are added to a glass component consisting of a blend of 1 mol Li2O, 1-2mol SiO2, 0.001-0.1mol Al2O3, 0.01-0.15mol P2O5 and 0.01-0.17mol and the mixture is melted and solidified. This solid glass is heated up to 500-800 deg.C nucleus forming temperature at a rate of 60-80 deg.C/hr and kept for a prescribed time at this temperature to form nucleus and then heated up to 850-1200 deg.C crystallization temperature at a rate of 60-80 deg.C/hr and kept for a prescribed time at this temperature to crystallize the glass. Then the temperature of the glass is lowered at a rate of 150-300 deg.C/hr to provide the objective crystallized glass having =600 Vickers hardness HV.