Kiln bricks, also known as refractory bricks, are made through a specialized firing process of a clay-based composition. This involves heating the mixture in a kiln until it achieves partial vitrification, and sometimes glazing for specific applications.
Understanding the Kiln Brick Manufacturing Process
Here's a breakdown of the key steps involved in manufacturing kiln bricks:
- Raw Material Selection: The primary raw material is usually chamotte, a pre-fired clay. Refractory bricks typically contain 30-40% alumina. Other materials can be added to achieve desired properties.
- Mixing and Shaping: The raw materials are thoroughly mixed with water to create a workable clay mixture. This mixture is then shaped into the desired brick form using various methods, including:
- Extrusion: For consistent shapes.
- Molding: Using molds to form individual bricks.
- Pressing: Applying pressure to create dense bricks.
- Drying: The shaped bricks are carefully dried to remove moisture. This step is crucial to prevent cracking during the firing process.
- Firing (Vitrification): This is the most critical step. The dried bricks are loaded into a kiln and fired at high temperatures.
- The temperature depends on the desired properties of the brick and the raw materials used.
- The firing process causes the clay particles to fuse together, a process known as vitrification. Partial vitrification creates a strong and durable brick.
- Cooling: The bricks are slowly cooled to prevent thermal shock and cracking.
- Optional Glazing: For certain applications that require enhanced resistance to chemical attack or abrasion, the bricks may be glazed after firing.
Properties and Composition
The specific properties of kiln bricks depend on their composition and the firing process. Key characteristics include:
- High Heat Resistance: Kiln bricks are designed to withstand extreme temperatures without deforming or melting.
- Thermal Shock Resistance: They can endure rapid temperature changes without cracking.
- Chemical Resistance: Some kiln bricks are formulated to resist corrosion from acids, alkalis, and other chemicals.
- Mechanical Strength: They possess sufficient strength to support heavy loads within a kiln.
The amount of alumina in the brick composition is also important, as it helps give the brick strength and resistance to heat. According to the reference information, refractory bricks usually contain 30-40% alumina.
Summary
In short, kiln bricks are created by firing a clay-based composition, often containing chamotte and 30-40% alumina, in a kiln. This process leads to partial vitrification, and optionally glazing, to create bricks suitable for high-temperature applications.
