How tempered glass is produced
The process begins with cutting the glass to the desired size and shape, followed by polishing the edges to remove sharpness. The glass is then thoroughly cleaned to eliminate any contaminants that might interfere with the heating process.
Next, the glass is heated in a special tempering furnace and becomes soft and malleable. Once heated, the glass is rapidly cooled by high-pressure air. This rapid cooling causes the outer surface of the glass to solidify quickly, creating compressive stress, while the inner core remains under tension. This balance of stress makes tempered glass much stronger than ordinary glass, increasing its resistance to breakage.
Heating temperature and time
The temperature to which glass is heated is one of the most critical factors affecting the quality. The glass must be heated to a temperature between 600°C and 650°C to achieve the desired strength and durability. If the temperature is too low, the glass may not fully temper, resulting in a lower resistance to breakage. If overheated, the glass can become too soft, leading to deformation or structural weakness. Additionally, the heating time must be carefully controlled. Insufficient heating time may prevent the glass from reaching uniform temperature, while excessive heating time may compromise the material’s integrity.
Cooling rate
After being heated, the glass is subjected to rapid cooling, typically by high-pressure air. This process, known as quenching, causes the outer surface of the glass to cool and solidify much faster than the inner layers, creating a compressive stress on the surface and tension within the core. The cooling rate must be uniform to avoid stress imbalances that can lead to cracks or uneven strength. If the cooling is too fast or uneven, the glass may not achieve the desired mechanical properties, resulting in potential safety hazards or structural failure under stress.
Raw glass composition
The chemical composition of the glass is another critical factor. Glass made from different raw materials or with varying proportions of ingredients (such as sodium, calcium, and magnesium) can have differing thermal expansion rates and behaviors during the tempering process. Variations in composition can lead to differences in how the glass behaves under heat and pressure, affecting the final quality of the tempered glass.
Cutting and edging
Since tempered glass cannot be re-cut after tempering, it is essential to accurately cut the glass sheets, ensuring the correct size and shape. The following procedure is to grind and polish the glass edge. Ideal edging performance helps remove sharp edges and micro-cracks generated during the cutting process, ensuring an even edge without sharp corners or notches. This prevents stress concentration at the edges during tempering, which could otherwise cause the glass to break.
Washing and drying
After cutting and edging, the glass must undergo washing and drying to remove dust, grease, fingerprints, and other impurities from the surface, as well as any glass debris left from the cutting and grinding processes. This ensures the glass surface is clean and flawless, which helps improve the tempering quality. If the glass is not properly cleaned or not fully dried before tempering, bubbles or defects may form during the tempering process.
Conclusion
The performance of tempered glass is influenced by multiple factors that must be precisely controlled throughout the manufacturing process. From heating and cooling rates to glass composition, each step requires careful attention to ensure the glass achieves its desired strength, durability, and safety.
Manufacturers must balance these variables to optimize the tempering process and deliver high-quality tempered glass that meets both industry standards and customer expectations.
