Monolithic refractories have developed over the years to become what they are today. This technical blog post will talk specifically about castables, gunning mixes and dry vibratables and how they have evolved.
Refractory materials are fabricated in two forms: shaped and unshaped (monolithic) refractories. Shaped refractories include fired and unfired materials with predetermined shapes, precast shapes and fusion cast refractories. Monolithic materials include plastic mixes, castables, ramming materials, dry vibratable, gunning materials, fettling materials, coatings and mortars. Monolithic materials differ from refractory bricks in that they are not shaped and fired before use. These materials do not have high energy requirements, are more readily available, take shorter times to install, can be repaired locally and require less manpower.
Last week Munich hosted one of the largest ceramic exhibitions: Ceramitec 2018. From 10-13 April the international ceramics industry gathered around the exhibition, which was, in general terms, really successful. In case you couldn't attend, we were there to be able to show you.
In the past, potters used to “age” their moist clay in damp cellars or storage containers for years to achieve the effects that are now possible after a few minutes of clay mixing.
The raw materials used to make bricks are the most important part of the process. The quality of the brick and the success or failure of the brick plant can often be traced to the raw materials. The planning and implementation of a raw materials program is the backbone of a well-run brick plant. Brick plants are often built in close proximity to the primary raw materials to be used for decades. The quality and consistency of these raw materials normally vary throughout the mine property. When the characteristics of some mined materials are too far out of specifications it may be necessary to avoid these raw materials thus reducing the raw material reserves. Some of the characteristics and some of the ways to optimize the usage of raw materials are described below.
The pressing stage is one of the most demanding in the production of ceramic bodies. Therefore, gaining any improvements here is directly translated into savings along the production process. These improvements will help to optimize the total costs of the manufactured products by reducing losses whilst improving the quality of the shaped materials.
Generally, refractories are classified as basic, high alumina/silica, fireclay and insulating. There are also classes of “special refractories” which include Silicon Carbide, Silicon Nitride, Graphite, Zircon, Zirconia, fused cast and several others. Most refractory materials are supplied as preformed shapes. However, they also are manufactured in the form of special purpose clays, bonding mortars and monolithic such as castable, plastic refractories, ramming mixes and gunning mixes. In fact, many refractories materials have been developed specifically to meet the service conditions of a particular process. The characteristic properties of each refractory class are a function of both their raw material base and the methods used to manufacture the refractory products.
Drying is one of the most critical parts of making quality brick. There are a number of things that can be done to improve drying and reduce drying defects. In order to reduce cracking there needs to be an understanding of the drying process and understanding of the brick body that is being dried.