Characteristics and Applications of Silica Brick

Silica brick is a refractory product primarily composed of silica (SiO₂ content ≥93%). It is manufactured from quartzite with a small amount of mineralizer and fired at high temperatures. Its mineral composition consists of a multiphase structure including tridymite, cristobalite, residual quartz, and a glassy phase formed at high temperatures.

As an acidic refractory material, silica brick exhibits strong resistance to acidic slag erosion but is highly susceptible to alkaline slag attack. It is easily degraded by oxides such as Al₂O₃, K₂O, and Na₂O, while demonstrating good resistance to CaO, FeO, and Fe₂O₃.

A key advantage of silica brick is its high refractoriness-under-load (RUL) temperature, which ranges between 1640–1680°C, close to the melting points of tridymite (1670°C) and cristobalite (1713°C).

When reheated, silica brick undergoes irreversible expansion due to the continued conversion of residual quartz. It maintains stable volume between 300°C and its melting point. Upon heating to 1450°C, it expands by 1.5%–2.2%, ensuring tight joints and improved structural integrity in furnace linings.

However, silica brick has two major drawbacks: low thermal shock resistance (1–4 water-quench cycles) and moderate refractoriness (1690–1730°C), limiting its applications.

Primary Applications:

• Coke ovens
• Glass melting furnaces
• Acidic steelmaking furnaces
• Other high-temperature industrial equipment

Usage Precautions:

1. Avoid rapid heating/cooling below 600°C due to abrupt volume changes from phase transitions at 200–300°C and 573°C.
2. Minimize contact with alkaline slags to prevent chemical corrosion