Clay Refractory Firebricks
Clay refractory firebricks are an essential component of the production and maintenance of furnaces. As the demands of industry continue to expand, firebrick knowledge will become increasingly important.
In a general sense, clay refractory firebricks provide many of the same functions as cast refractories, but with improved resistance to thermal shock, mechanical shock, erosion, and abrasion. Additionally, clay firebricks have higher refractoriness, meaning they can resist higher temperatures than cast refractories.
Clay Refractory Firebricks are manufactured in a variety of shapes and sizes, most commonly referred to as standard bricks or modular bricks. Standard bricks usually measure 9” x 4.50” x 3” and are used in large commercial and industrial applications. Modular bricks are typically made to fit tightly into specific configurations, typically in order to form a uniform wall thickness along the furnace walls. Another type of brick is called fused clay refractory firebricks. These are highly compacted and have a higher refractoriness than the standard or modular bricks.
In terms of manufacturing, the raw materials used to produce Clay Refractory Firebricks are typically clays such as kaolinite and bentonite, combined with aggregates such as sand, alumina, and zircon. A variety of processes are employed in order to manufacture the desired end shape and properties of the brick.
The most common method is extrusion, whereby the material is forced through a shaped metal die to form the desired shape. Other processes such as isostatic pressing and ram pressing may be employed to produce Clay Refractory Firebricks with the desired properties.
The brick that is typically used for most applications is called a high performance brick, and usually is comprised of 60% clay and 40% aggregate. The high performance brick is ideal for furnace linings, stacks, and other high heat applications.
The brick used in industrial applications also typically includes additives such as alumina, magnesia, and zircon in order to improve the brick’s refractoriness and other physical properties.
The cross-section of a firebrick typically shows a core material that is surrounded by several layers of a protective coating. The core is usually composed of a mixture of clay, alumina, and magnesia, while the protective coating or shell is a mortared clinker or ceramic fiber design. The shell helps to protect the core material and helps to create an insulating layer of high-temperature, fire-resistant material between the core and the furnace walls.
Due to their heavy composition, firebricks often require two people to install. The bricks usually have fin-type projections that help to create a better bonding action to the furnace wall. Additionally, many firebricks are designed with a beveled edge on one side in order to create an air gap that can be filled with a refractory mortar in order to increase air circulation and create a better seal between the firebrick and the furnace wall.
In conclusion, Clay Refractory Firebricks are an important component for the manufacture and maintenance of furnaces. Understanding the range of shapes and sizes, manufacturing methods, and the nuances of the cross-section, are all essential components of maintaining and operating a safe and reliable furnace.
