How can the crack resistance of rice cooker cover glass be improved when subjected to thermal shock?
Release Time : 2025-12-17
As a component of kitchen appliances that directly comes into contact with high-temperature steam and low-temperature environments, the rice cooker cover glass's resistance to thermal shock directly affects the product's safety and lifespan. Improving this performance requires comprehensive improvements across multiple dimensions, including material selection, structural design, process optimization, and usage and maintenance, to reduce the risk of cracking caused by thermal stress.
Material selection is fundamental to improving crack resistance. Traditional soda-lime glass, due to its high coefficient of thermal expansion, is prone to cracking due to significant thermal stress generated by the temperature difference between the inside and outside during rapid heating and cooling. Tempered glass, through physical or chemical strengthening treatments, forms a compressive stress layer on the surface and a tensile stress layer internally. This stress distribution effectively offsets external thermal stress, significantly improving impact resistance and crack resistance. Furthermore, some high-end products use high borosilicate glass, whose coefficient of thermal expansion is only 1/3 that of ordinary glass, and its heat resistance can reach temperature differences of over 150℃, making it more suitable for the frequent temperature fluctuations in rice cooker use.
Structural design must balance sealing and stress dispersion. Rice cooker cover glass is typically fixed to a metal or plastic frame using adhesive or clips. If the difference in thermal expansion coefficients between the frame and the glass is too large, inconsistent deformation during temperature changes can lead to stress concentration at the edges. Optimized design can employ elastic sealing rings or flexible transition layers, allowing for slight relative displacement between the glass and the frame, reducing stress transmission. Simultaneously, chamfering the glass edges avoids stress peaks caused by right angles, while curved transitions further disperse stress, reducing the risk of cracking.
Process optimization is a key aspect of improving performance. During tempering, parameters such as heating temperature, cooling rate, and air pressure directly affect the stress distribution within the glass. Excessively rapid cooling may result in insufficient surface compressive stress, while excessively slow cooling may lead to excessive internal tensile stress, both reducing crack resistance. Therefore, optimal process parameters must be determined experimentally to ensure a uniform and appropriately deep compressive stress layer on the glass surface. Furthermore, the edges of the cut glass must be finely polished to remove microcracks and other defects, preventing these defects from expanding into cracks under thermal stress.
Surface treatment technologies can further enhance the glass's thermal shock resistance. Nanocoating technology reduces surface roughness and minimizes localized overheating during heat conduction by depositing an extremely thin ceramic or polymer film on the glass surface. Simultaneously, some coatings are hydrophobic, preventing condensation buildup and stress concentration caused by sudden temperature drops. Furthermore, ion exchange strengthening technology replaces sodium ions with potassium ions on the glass surface, forming a deeper compressive stress layer and significantly improving crack resistance.
Usage habits also significantly impact the lifespan of rice cooker cover glass. Frequent rapid heating and cooling (such as rinsing immediately with cold water after cooking) accelerates glass fatigue and reduces crack resistance. Therefore, users are advised to allow it to cool naturally after use and avoid direct contact with cold water or air. Additionally, use a soft cloth or sponge for cleaning to avoid scratching with hard objects, which can cause micro-cracks that may expand into macro-cracks under thermal stress.
Regular maintenance and inspection are crucial for preventing cracking. Users should regularly check the sealing strips around the glass edges for aging or detachment. If any problems are found, replace the sealant promptly to prevent steam leakage and localized overheating due to seal failure. Additionally, if minor scratches or cracks are found on the glass surface, stop using the product immediately and replace the cover with a new one to prevent the cracks from spreading during subsequent use.
Improving the thermal shock resistance of rice cooker cover glass requires collaborative improvements in materials, design, manufacturing processes, usage, and maintenance. By selecting high-performance materials, optimizing structural design, precisely controlling process parameters, applying surface treatment technologies, and cultivating good usage habits, the risk of cracking in alternating hot and cold environments can be significantly reduced, extending product lifespan and enhancing the user experience.