Lining Material Properties

TYPICAL PROPERTIES OF THREE REFRACTORY MATERIALS USED COMMONLY FOR MAKING INDUCTION FURNACE LINING

SR NO SILICA (SiO2) ALUMINA (A1203) MAGNESIA (MG O)
1. Nature Acidic Neutral Basic
2. Melting Point, (0C) 1723 2050 2800
3. Free Energy at 14500 C, (kj / mol) -594 -758 -732
4. Average Thermal Conductivity between 00C and 12000C, (W/mk) 1.7 2.6 4.0
5. Expansion Coefficient between 00C and 12000C 12.2 8.2 13.8
6. RelativeThermal shock Resistance (R+6K/Ea) 715 480 345
7. Relative Cost (taking silica cost as unity) 1 5 to 10 5 to 10

Where:

  • 6 = tensile strength
  • K= thermal conductivity
  • E= modulus of elasticity
  • a= thermal expansion coefficient
  • TYPICAL SIZE GRADING OF SILICA RAMMING MASS

    SIZE TYPICAL CONTENT %
    Coarse -4 mm + 0.85 mm 33
    Medium -0.85 mm + 0.20 mm 30
    Fine -0.20 mm + 0.063 mm 17
    Ultrafine -0.063 mm 20

    The ultrafine and fine particles combine with boric oxide to form a low-melting point glassy phase which fills in the gaps between the coarse and medium size quartz grains and binds these grains with one-another.

    Note: The bond is complete in the inner-most sintered layer which has been heated to above 13000C. in the middle fritted layer, which has been exposed to a temperature between 9000C and 13000C, the bond is partial. The outermost layer in contact with asbestos Sheet is not heated beyond few hundred degrees centigrade, and the bond does form in This Layer.