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Chemical and Thermal Curing
Strengthening the Transparent: A Technical Guide to Glass Engineering
1.Physical Tempering: Strength Through Thermal Shock)
Commonly known as 'safety tempering,' this process relies on extreme temperature differentials. By heating glass to 650°C -700°C and then rapidly cooling (quenching) it with high-pressure air, the outer surfaces contract and solidify while the core remains fluid. As the core eventually cools and shrinks, it pulls the outer layers into a permanent state of high compression.
● The Safety Mechanism:When the stress equilibrium is broken, the stored energy causes the glass to fracture into small, granular 'dice' rather than dangerous shards.
● Best For: Building facades, appliances.
2.Chemical Strengthening: Precision Through Ion Exchange
Chemical strengthening is a low-temperature molecular process (~400-450°C). The glass is submerged in a molten potassium nitrate (KNO3) bath. Through ion exchange, smaller sodium ions (Na+) leave the glass surface and are replaced by larger potassium ions (K+). This 'stuffing' of larger atoms into the surface lattice creates deep, uniform compressive stress without any thermal softening.
● The Optical Advantage:Because the glass never reaches its softening point, it maintains perfect flatness and zero optical distortion.
● Best For: display cover glass, precision optics.
