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How is high borosilicate glass refined? Unveiling the production process
Borosilicate glass is a special type of glass with high temperature resistance and strong thermal shock resistance, widely used in laboratory utensils, heat-resistant tableware (such as glass cups, freshness boxes), optical instruments, etc. Its manufacturing process is more complex than ordinary glass, and the following are the key production steps:
1. Raw material ratio
The core components of high borosilicate glass are silicon dioxide (SiO ₂, 70-80%) and boron oxide (B ₂ O3, 10-15%), with small amounts of sodium oxide (Na ₂ O) and aluminum oxide (Al ₂ O3) added. The addition of boron significantly reduces the coefficient of thermal expansion, allowing it to withstand drastic temperature differences (such as direct heating or rapid cooling).
2. High temperature melting
The mixed raw materials are melted in an electric furnace or gas furnace above 1600 ℃. Ordinary glass (such as soda lime glass) only requires about 1200 ℃, but high borosilicate glass requires a higher temperature to completely melt and eliminate bubbles due to its boron content.
3. Molding process
Molten glass can be formed in different ways:
Blow molding (such as beakers and test tubes): Dip a metal tube into glass liquid and blow mold it manually or by machine.
Compression molding (such as glass plates): Inject glass liquid into a mold and use a stamping machine to shape it.
Tube forming (such as glass tubes): Molten glass is pulled into a slender tube shape by traction equipment.
4. Annealing treatment
The formed glass needs to be slowly cooled (annealed) to eliminate internal stress. The annealing temperature for ordinary glass is about 500 ℃, while high borosilicate glass requires 560-600 ℃ and is kept in a dedicated annealing furnace for several hours to prevent cracking.
5. Testing and processing
The finished product needs to undergo tests such as light transmittance, resistance to sudden temperature changes (such as ice water → boiling water test), and chemical stability. Some products require secondary processing, such as grinding, scale printing, or tempering reinforcement.
Why is high borosilicate glass safer?
Its low coefficient of expansion (about 3.3 × 10 ⁻⁶/℃) allows it to withstand a temperature difference of * * -30 ℃~400 ℃ * * and is not easy to explode; At the same time, it has strong chemical inertness, acid and alkali resistance, and is suitable for food and medical use.
From raw materials to finished products, the manufacturing of high borosilicate glass integrates precision proportioning and high-temperature processes, making it a “special soldier” in the glass industry.
