68｜Glass Manufacturing Methods, Forming Methods, Processing Methods 6

68-Glass manufacturing methods, molding methods, processing methods 6

Hello everyone! 🎵 The nationwide abnormal weather continues with scorching heat, exceeding body temperatures with 39 or even 40 degrees, and squall-like thunderstorms also occur. It's truly tropicalized.

For those of us from the Showa generation, temperatures above 30 degrees Celsius were considered hot, but we would sprinkle water, and cool ourselves with chilled watermelon or barley tea from the refrigerator. The reflection from the concrete wasn't this bad, and the hot air from air conditioner outdoor units wasn't this hot either, I believe. Just thinking about what kind of world it will be if global warming progresses further makes me feel hot.

Last time, we discussed heat-resistant glass and borosilicate glass. This time, I'd like to delve a little deeper into the topic.

Borosilicate glass is a type of glass that has a low coefficient of thermal expansion and can withstand temperature changes due to the addition of boric acid to its material. When the tensile stress caused by the difference in expansion between hot and cold parts exceeds the allowable limit, it leads to breakage. Therefore, if there is less thermal expansion, the glass can be used as heat-resistant glass, also known as heat-proof glass.

Each material has its own specific coefficient of expansion. Simply put, the coefficient of expansion is a numerical value that indicates how much a material expands linearly when its temperature is raised by 1°C. Comparing the expansion coefficients of several materials, glass and ceramic materials have lower expansion coefficients (they expand less when heated) than metallic materials. For materials and their expansion coefficients (×10-6/°C), borosilicate glass has 3.25, fine ceramics have 4.4, soda-lime glass has 9.0, and iron has a large 11.7.

Furthermore, the heat resistance temperature difference changes depending on the thermal expansion coefficient. According to JIS standards, items with a heat resistance temperature difference of 120°C or more but less than 400°C are labeled as "heat-resistant glass utensils," while those with a heat resistance temperature difference of 400°C or more are labeled as "super heat-resistant glass utensils." Under the Household Goods Quality Labeling Act, the usage changes further depending on the heat resistance temperature difference.

These are always required to be displayed on the product. Please choose and use the correct type of heat-resistant glass according to its intended use.