Major Types of Refractories, Characteristics, and Their Applications

Major Types of Refractories, Characteristics, and Their Applications

The term ‘refractory’ denotes the mechanical strength of a particular material, especially at high temperatures. Refractory materials produced by the leading Indian refractory suppliers and used across industries come with an extremely high melting point. As a result, these materials are capable of maintaining their strength as well as structure even under the harshest of conditions.  

As per the American Society for Testing and Materials, the definition of refractories is “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) are called refractories”.

Let’s understand refractories by an example

Let’s understand the term in more clarity by some examples. Take the example of a car which is made using a large number of materials as per the requirement. These materials mainly include copper, glass, plastics, and aluminum among others. All these materials call for extremely high temperatures when they are in the manufacturing or processing units. 

For example, when the iron is converted into steel in a unit, the temperature goes up to 20000 degrees Celsius. The furnaces wherein the iron is processed always stay unaffected by the level of heat generated inside because they have a coating of refractory material. In the same way, these special coatings of refractory materials are used to process various other metals and non-metal kinds of stuff such as glass, copper, aluminum, and plastics.

Some major types of refractory materials

Refractory bricks come in a large number of shapes and sizes as per the specific requirements of an industry. Some of the most common examples of refractory materials include the following: 

  • Fireclay refractories
  • High alumina refractories
  • Silica brick
  • Magnesite refractories
  • Chromite refractories
  • Zirconia refractories
  • Insulating materials, and
  • Monolithic refractories.

Based on the service conditions and temperature ranges, a large number of refractory materials are used in applications that include ovens, boilers, kilns, and conventional industrial furnaces.  

Silica Refractory

Silica brick is one of the most important refractory materials having around 93% SiO2. Top refractory cement suppliers in India make use of high-quality rocks as a raw material to manufacture them. Silica bricks are well-known for having outstanding mechanical strength especially when the temperature nears their real fusing point. This unique behavior of silica refractories contrasts with different other refractories including alumino-silicate materials. Refractories apart from silica bricks start fusing and creeping at temperatures that are even lower than their fusion points. A wide range of silica bricks find applications in industries such as glass and steel. 

Fireclay Refractory

The hydrated aluminum silicates that have around 25% -45% Al2O3 and 50% -80% SiO2 are known as fireclay refractories. These refractory materials have only minor additional minerals. Fireclay refractories are not only the most popular and inexpensive ones but also their raw ingredients are commonly available. These refractories find applications in regenerators, furnaces, kilns, stoves, and a large number of other purposes. 

Magnesite Refractory

Magnesite refractories are considered to be chemically fundamental materials having around 85% magnesium oxide. Made of magnesite (MgCO3) and silica, these refractories often feature weaker attributes and their main value lies in their resistance to the basic slags that mainly include lime and iron-rich ones. Magnesite refractories are considered to be the most important refractory materials that find applications in the basic steel manufacturing process. Basics bricks are now used in the following applications:

  • Glass tank checks
  • Lime and cement kilns
  • Metallurgical burners, and
  • Metallurgical furnaces.

When used across applications with exposure to high temperatures, acidic refractories might also be anticipated to have a certain reaction with limes as well as basic oxides. 

High Alumina Refractories

The alumina refractories that have more than 45 percent alumina are known as high alumina refractories. The content range includes the following:

  • Alumina from 45 to 95%
  • Sillimanite (61%)
  • Mullite (70–85%), and
  • Corundum (99%). 

As alumina concentration increases in alumina refractories, their refractoriness also increases. Some of the major applications areas of high alumina refractories include the following:

  • The hearth and shaft of blast furnaces
  • Lime and ceramic kilns
  • Cement kilns
  • Glass tanks, and
  • Crucibles for melting a comprehensive of metals. 

Zirconia Refractories

Zirconia refractories come with an outstanding hardness at room temperature, and across the applications, this hardness can be maintained up to 15000 degrees Celsius temperature range. The thermal conductivity of Zirconia refractories is substantially lower when compared to all other types of refractory materials. These refractories react neither with molten glasses nor any other liquid metal. Consequently, they are an ideal refractory material to be used in high-temperature construction materials in the glass and metallurgical furnaces.

Monolithic Refractory

Monolithic refractories are materials that are put into use as a suspension and finally hardened to create a solid mass. Monolithic is the most common term used for all types of unshaped refractories. Monolithic refractories are fast replacing the conventional type of fir. 

Some of the major types of monolithic refractories include the following:

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

Monolithic refractories find applications in a large number of industrial applications. Some of the most common ones among them include:

  • Non-ferrous metallurgical
  • Steel
  • Cement
  • Petrochemical, and
  • Waste disposal industries. 

When it comes to the availability of monolithic refractories, the choices are in many forms and formulations. The most significant properties of these materials lie in the following:

  • Individual chemical inertness
  • Thermal shock resistance at high temperatures
  • Abrasion resistance, and
  • Mechanical integrity.

Concluding Remarks 

Taking innovation to 1200°C and beyond, RHI Magnesita is among the leading manufacturers and suppliers of supreme quality refractory products. The company has a high level of geographic diversification with shipping in more than 125 countries worldwide, 12,000 employees, and 28 principal production sites. Offering the industry’s most comprehensive product and solutions portfolio including Magnesia and Alumina-based bricks and mixes for large industrial customers, RHI Magnesita is committed to innovation in every aspect of its business. The company’s R&D investment and the team of experts are unrivaled. It always drives breakthroughs in materials and data, new business models, and efficient new processes.