Refractory Technology

121. Rate of slag attack on refractories increases with rise in temperature due to the

1. Decreased viscosity of slag
2. Increased thermal conductivity of brick
3. Oxidising condition in the furnace
4. None of these

View answer

122. Refractories are dried in the

1. Rotary kilns
2. Tunnel kilns
3. Sun
4. None of these

View answer

123. Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to

1. Thermal spalling
2. Slag attack
3. Fusion under load
4. CO attack

View answer

124. Refractoriness of a typical silica brick corresponds to Segar cone number, '32', which is equivalent to a temperature of _________ °C.

1. 1380
2. 1520
3. 1710
4. 1915

View answer

125. Refractoriness under load (RUL) is the most important property for the refractory bricks

1. At the hearth bottom of the furnace on which stock is placed
2. Used for furnace insulation
3. Used in the roof of the furnace
4. None of these

View answer

126. Refractoriness under load (RUL) of fireclay bricks (under a load of 2 kg/cm2) is _________ °C.

1. 500
2. 1000
3. >1350
4. >2000

View answer

127. Refractoriness under loads (RUL) is quite close to the fusion temperature (PCE) for _________ bricks.

1. Fireclay
2. Silica
3. Dolomite
4. Very low alumina

View answer

128. Refractoriness/fusion points of 'Superduty' refractories is _________ °C.

1. 1520-1630
2. 1630-1670
3. > 1730
4. > 2000

View answer

129. Refractory bricks having lower porosity have

1. High insulating properties
2. Low heat capacity
3. Low thermal conductivity
4. Greater strength

View answer

130. Refractory bricks with lower permeability is produced by using

1. Higher firing temperature
2. Higher moulding pressure
3. Finer grog size
4. All (A), (B) and (C)

View answer