| 摘要 |
<p>PROBLEM TO BE SOLVED: To temper the glass plate and concurrently to surely break and remove a defective glass sheet product by in an annealing stage, annealing a glass sheet passed through the preceding forming stage, under specified conditions so as to cause cracks on the peripheries of nickel sulfide particles in such a glass plate contg. nickel sulfide and to cause natural breakage of the glass plate contg. nickel sulfide in the subsequent tempering stage. SOLUTION: In an annealing stage of this production, the temp. of a glass plate passed through the preceding forming stage is lowered to 160 to 280 deg.C and then, the glass sheet is maintained at that temp. for 6 to 30 min. Accordingly, when such a glass plate contains nickel sulfide(NiS),α-NiS (α-phase) contained in the glass sheet is subjected to phase transition toβ-NiS (β-phase) to cause cracks due to the volume expansion of nickel sulfide on the peripheries of nickel sulfide particles and in the subsequent tempering stage, when the glass sheet is quenched from a temp. in the vicinity of the softening point, compression stress is caused in a surface layer of the glass plate to allow the cracks to rapidly extend by the difference in thermal stress caused by the quenching. Thus, the glass sheet can be tempered and concurrently, a defective glass sheet product can surely be broken and removed.</p> |
