How does float glass achieve high flatness and optical uniformity?

2025-04-22 09:01:21

The high flatness and optical uniformity of Float glass mainly rely on the following core technologies:

Tin bath forming process

After the molten glass liquid (about 1100 ℃) flows into the tin bath, it floats on the surface of the tin liquid due to density differences (glass liquid 2.5g/cm ³<tin liquid 6.5g/cm ³), and naturally spreads out into a uniform glass strip under the action of gravity and surface tension. The thickness tolerance can be controlled within ± 0.2mm. Nitrogen hydrogen mixed protective gas (with a hydrogen content of 4-8%) is introduced into the tin bath to prevent tin oxidation and maintain a reducing environment, ensuring that the glass surface is free of ripples and oxidation defects.

Precision temperature control and annealing

When the glass ribbon passes through the cooling zone (996-883 ℃) to the thinning zone (883-769 ℃), multiple pairs of edge drawing machines are used to apply lateral tension and accurately control the thickness (0.3-25mm). Subsequently, it enters the annealing kiln for slow cooling at a gradient of 0.5 ℃/cm to eliminate internal stress and avoid optical distortion.

Raw material and process optimization

By using high-purity quartz sand (SiO ₂>99.5%) and low iron formula (Fe ₂ O3<0.015%), the influence of impurities on the transmittance is reduced, resulting in a visible light transmittance of over 92%. Synchronize the implementation of online laser scanning detection and provide real-time feedback on surface flatness data (roughness<1nm) to ensure optical uniformity.

In summary, the float glass process achieves high flatness and optical performance of glass through tin bath forming, annealing stress relief, high-purity raw materials, and full process monitoring, meeting the needs of high-end fields such as building curtain walls and automotive glass.

Longbo Clear Float Glass

Thickness:3-19 mm

Size:2250×3300mm,2550×3300mm,2440×3660mm,etc

Jumbo Size:3300×5000mm,3300×5500mm,3300×5800mm,etc

Moreproduct details：https://longboglass.com/product/2.html