An Explanatory Guide to the Types of Refractory Materials

An Explanatory Guide to the Types of Refractory Materials
‘Refractory’ refers to a material's mechanical strength, particularly at high temperatures. Different types of refractory materials from major Indian manufacturers and utilized across industries have a very high melting point. Therefore, these materials can keep strength and structure intact even under difficult environments. The American Society for Testing and Materials defines refractories as “the non-metallic materials having physical and chemical qualities that make them perfect for different types of constructions or as crucial components of systems applied to temperatures above 1,000 °F (811 K; 538°C)”.
Refractory materials protect iron-processing furnaces from heat. These unique coatings of refractory materials also process glass, copper, aluminum, and polymers.


Some Prominent Refractory Materials Include the Following:

Refractory Bricks

Manufacturers produce a wide range of refractory bricks in several sizes and shapes with many different unique features. Some of the most common ones include the following:
High alumina
Silica brick
Insulating materials, and
Monolithic refractories.
The temperatures and service conditions of boilers, furnaces, kilns, ovens, and other applications influence the kind of refractory employed.

Fireclay Refractories

Fireclay refractories are hydrated aluminum silicates. They contain 25–45% Al2O3 and 50–80% SiO2 and minerals. Most furnaces, kilns, stoves, regenerators, and other purposes utilize fireclay brick. Fireclay brick is inexpensive and accessible.

Silica brick

Silica brick contains at least 93% silica dioxide. The source may be high-grade rocks. Silica brick is strong at temperatures around its fusing point. Many additional refractories, such as alumino-silicates, fuse and creep at temperatures far lower than their fusion points. The glass and steel industries use several silica brick grades.
Pure silica melts at 1713°C, however, it creates silicates that melt readily when mixed with alkaline chemicals. Silica used as a refractory material should not include alkali. Quartzite, Dinas rock, and ganister contain silica. Ganister has 98% natural silicon. It is ready as bricks. Silica bricks are thick, hard, fine-grained quartzite (ganister). The crushed rock is water-ground and blended with 2% lime. Bricks may be hand-molded or mechanically pressed from this mixture and baked at the correct time and temperature after drying with hot air. To strengthen the brick, alkali lime interacts with acidic SiO2 and fuses at specific points.

High Alumina Refractories

High-alumina refractory products contain around 45% alumina. The sample contains 45–95% alumina. The refractory materials sillimanite (61%), mullite (70–85%), and corundum (99%) are the most often utilized forms. Increasing the proportion of alumina in high-alumina refractories often increases the refractoriness of the material. There are a variety of applications for high alumina refractories, such as the hearth and shaft of blast furnaces, lime and ceramic kilns, cement kilns, glass tanks, and crucibles for melting a broad variety of metals.

Magnesite Refractories

Magnesite refractories are materials that are chemically fundamental and include at least 85 percent of the element called magnesium oxide. Magnesite (MgCO3) and silica (SiO2) are the two components that are used in the production of these elements. In general, the physical features of this kind of brick could be better, and the primary reason for their high value is that they are resistant to basic slags, especially slags that are rich in lime and iron. In terms of the fundamental processes involved in the production of steel, these refractories comprise the most significant category. Basic bricks are now being effectively used in a variety of applications, including but not limited to metallurgical furnaces, glass tank checks, lime and cement kilns, and more.

Chromite Refractories

Magnesite-chromite refractories typically comprise at least 60% magnesium oxide and 8-18% chromium oxide, while chrome-magnesite material often has 15-35% chromium oxide and 42-50% magnesium oxide. When it comes to the construction of the critical pathways of high-temperature furnaces, chrome-magnesite refractories are essential. High refractoriness and the ability to tolerate corrosive slags and gases are also characteristics of these materials. In the process of steel melting, the magnesite-chromite products can withstand a wide range of temperatures and may even come into touch with the most fundamental slags. Magnetite-chromite usually has better-spalling resistance than chrome-magnesite.

Zirconia Refractories

At ambient temperature and 15000 degrees Celsius, zirconia refractories maintain their great strength. The data show that its heat conductivity is substantially lower than other refractories. 
Additionally, zirconia does not react well with liquid metals or glasses that are molten liquid. Metallurgical furnaces and glass furnaces may benefit from their use as high-temperature building materials because of their usefulness.

Monolithic Refractory Materials 

Monolithic refractory goods are all unshaped refractory materials that harden into a solid mass upon suspension. A significant number of applications, particularly those of industrial furnaces, are seeing monolithic refractories take the place of traditional-type burned refractories at a considerably quicker pace. 

Some prominent monolithic refractories include the following:

Ramming Refractories
Patching Refractories
Coating Refractories
Castable Refractories
Plastic Refractories
Refractory Mortars, and
Insulating Castables.

Insulating Materials

High porosity and poor thermal conductivity reduce heat loss in insulating refractory materials. Insulating materials are lighter and more heat-resistant than firebricks. No matter what the circumstances are, the thermal conductivity of the insulation will considerably increase as the temperature rises. Insulating refractories are currently accessible in a large variety of combinations and come in a wide range of characteristics. It is also less expensive in comparison to the bricks which are of a higher quality.

Dolomite Refractory  

India is rich in calcium-magnesium bicarbonate. Shaft kilns ignite it. Dolomite bricks are less conductive refractory products than magnesite. Calcium oxide in the brick reacts with atmospheric water and carbon dioxide to collapse it. Though cheaper than magnesite bricks, they function poorly. Repairing basic open hearth stove tops and furnace bottoms using dolomite refractory is common. 

Concluding Remarks 

RHI Magnesita is a prominent manufacturer and supplier of:
All types of refractory materials
Refractory bricks, and
RHI Magnesita innovates in all aspects of its business. The company has the industry's most comprehensive product and solutions portfolio. It includes Magnesia and Alumina-based bricks and mixes for major industrial clients. It spurs material and data breakthroughs, new business models, and efficient procedures.