Editing Refractory (section)

===Thermal conductivity===
Refractories may be classified by [[thermal conductivity]] as either conducting, nonconducting, or insulating. Examples of conducting refractories are [[silicon carbide]] (SiC) and [[zirconium carbide]] (ZrC), whereas examples of nonconducting refractories are silica and alumina. Insulating refractories include [[calcium silicate]] materials, [[Kaolinite|kaolin]], and zirconia.

Insulating refractories are used to reduce the rate of heat loss through furnace walls. These refractories have low thermal conductivity due to a high degree of porosity, with a desired porous structure of small, uniform pores evenly distributed throughout the refractory brick in order to minimize thermal conductivity. Insulating refractories can be further classified into four types:<ref name="IspatGuru" />

# '''Heat-resistant''' insulating materials with application temperatures ≤ 1100&nbsp;°C
# '''Refractory''' insulating materials with application temperatures ≤ 1400&nbsp;°C
# '''High refractory''' insulating materials with application temperatures ≤ 1700&nbsp;°C
# '''Ultra-high refractory''' insulating materials with application temperatures ≤ 2000&nbsp;°C