Lip Bricks for Rolled Glass Production
Lid bricks used in rolled glass production are classified into various types based on their material, including low-porosity clay, zircon mullite, α-β corundum, sillimanite, and fused silica. Currently, most solar rolled glass production lines use lip bricks made of zircon mullite, sillimanite, and α-β corundum.
Zircon-Mullite Lip Bricks
The main components of zircon-mullite lip bricks are ZrO₂≥6%, Al₂O₃≥75%, SiO₂≤18%, and Fe₂O₃≤0.5%. They are made from industrial alumina (or high-alumina bauxite) and zircon as raw materials, mixed, shaped, dried, and then fired at high temperatures in a shuttle kiln using a reaction sintering process. Zircon-mullite lip bricks possess a dense crystal structure, high mechanical strength at high temperatures, good wear resistance, good thermal shock stability, low reheat shrinkage and high-temperature creep, and extremely high chemical stability and resistance to alkaline media erosion. Their room temperature compressive strength is ≥100MPa, load softening start temperature is ≥1670℃, bulk density is 2.8g/cm³, and air cooling performance is ≥10 cycles. Due to their good wear resistance, long service life, short debubbling time, and minimal impact on the forming after lip wear, zircon-mullite lip bricks offer high cost-effectiveness. Therefore, it is increasingly used in solar rolled glass production lines.
Sillimanite Lid Bricks
Sillimanite, with the molecular formula Al₂O₃·SiO₂, has a theoretical chemical composition of 62.93% Al₂O₃ and 37.07% SiO₂. Typically, sillimanite’s mineral composition contains ≥55% Al₂O₃, ≤37% SiO₂, and ≤5% Fe₂O₃, TiO₂, CaO, MgO, Na₂O, K₂O, etc., making it a high-quality, high-alumina raw material. Sillimanite undergoes irreversible transformation into 83.96% mullite (3Al₂O₃·2SiO₂) and 16.04% silicate glass phase during high-temperature sintering at 1500–1750℃, a process known as sillimanization. Mullite-treated sillimanite can be used to prepare high-density clinker with a porosity of less than 3%. This clinker, after being pulverized, can be used to make refractory materials, including lip bricks. Lid bricks made of sillimanite can be used in high-temperature operations up to 1650℃, and have advantages such as high high-temperature strength, low porosity, good volume stability and thermal shock resistance, and resistance to molten glass corrosion. Therefore, sillimanite lip bricks are also used in solar rolled glass production lines.
α-β Corundum Lip Bricks
Corundum lip bricks are made from raw materials containing ≥94% alumina, ≤1.2% Na₂O, and ≤0.02% Fe₂O₃, through high-temperature alumina melting and casting in an electric arc furnace at temperatures above 2000℃. α-β corundum products consist of α-alumina and β-alumina, with their interlocking crystals forming a very dense microstructure, exhibiting excellent alkali resistance. In temperature ranges below 1350℃, its resistance to glass melt erosion and scouring is better than that of zirconia corundum bricks, possessing excellent mechanical strength and a long service life. Because it contains almost no impurities such as Fe₂O₃ and TiO₂, the matrix glass phase is extremely low, with a porosity ≤2% and a bulk density of 3.4 g/cm³. It produces very few bubbles or other foreign matter when in contact with molten glass, making it the best material for producing lip bricks. However, α-β corundum lip bricks suffer from poor thermal stability, are prone to cracking, and are expensive, limiting their widespread use in solar rolled glass production lines.
Regardless of the lip brick material, its appearance quality must meet the following requirements: the upper surface must be smooth and flat, free of molten holes. The lip brick edge must not have cracks, not gaps, or defects. The working surface and all contact surfaces must be finely ground to a precision of ±0.5mm, and the lip brick’s curvature must be consistent.
Processing Before Lip Brick Assembly
After the lip bricks arrive at the rolled glass manufacturing plant, if their length exceeds the required length or their surface is not smooth, they need to be processed to the required size using a cutting machine or ground.
- ① First, cut the lower edge of the lip brick. This should be done gradually and repeatedly to ensure a smooth, flat surface with good curvature.
- ② When processing the upper surface of the lip brick, it should also be done gradually and repeatedly to ensure a smooth, flat surface.
- ③ The bottom of each lip brick must be flat to maintain the stability of the lip brick and the brick frame support.
- ④ After pre-assembling the lip bricks, ensure that the contact area between the lip brick tips is less than 1mm. If the connection is not tight, grinding is required. The back of the lip brick should be as tight as possible while ensuring a tight fit, requiring a gap of less than 1.5mm.
- ⑤ Ensure that the inner dimensional tolerance of the lip brick is no greater than 5mm.
- ⑥ Based on the condition of the lip brick, use an aluminum alloy ruler and ink lines to clearly mark the areas where the lip brick tips will be processed. ⑦ Place the processed lip bricks near the kiln and bake for at least 72 hours.
- ⑧ Secure the baked lip bricks with clamps on a lip brick support, install the edge bricks, and fix them in place.
- ⑨ Precautions for processing lip bricks:
- When cutting lip bricks, leave approximately 5mm of length for processing.
- Use a pneumatic brick grinder for rough processing, and an electric angle grinder with a diamond wheel for fine processing.
- When processing the contact surface of the lip brick, repeated up-and-down finishing is required. Be careful to control the force applied; do not use excessive force.
- When high precision is required for the contact surface of the lip brick, it must be manually ground with a whetstone; do not use an electric angle grinder.
- When using a pneumatic angle grinder, pay attention to the orientation of the lip brick to prevent small brick pieces and dust from directly hitting your face. Wear protective gear to prevent facial injury.
- Handle lip bricks gently, ensuring the lip tip does not touch the ground. Lay cardboard on the ground to prevent damage.
- Because lip brick processing is delicate work, it takes one to two days. Therefore, the processing of lip bricks must be carried out in a timely manner so that they can be installed and used immediately once the calendering machine is replaced.
Buy high-quality glass kiln lip bricks, such as zircon mullite bricks, sillimanite bricks, α-β Corundum Bricks, etc. Fused AZS Bricks for glass kiln, please feel free to contact Rongsheng Refractory Factory now!
