A. Refractories used in muffle furnace should have low thermal conductivity
B. The electrical resistivity of refractories drops rapidly with rise in temperature
C. For reducing spalling tendency, the refractory should be well fired and its porosity should be
more
D. Refractoriness under load (RUL) of a refractory is always less than its refractoriness
Related Mcqs:
- Pick out the wrong statement ?
A. A ceramic material which becomes fluid upon heating and can be moulded in liquid/viscous
state is termed s glass
B. Ceramic materials do not undergo vitrification on heating
C. Ceramic materials are brittle in nature
D. Non-oxide ceramic materials generally act as a semi-conductor - Pick out the wrong statement?
A. Fluxing material like lime is added in clay to reduce the vitrification temperature
B. Main constituents of clay are alumina and silica
C. Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and
reduces its shrinkage on burning
D. Vitrification of fireclay material is done to increase its porosity - Pick out the wrong statement ?
A. Electrical conductivity of refractory is not important, when these are to be used in electrical
furnaces
B. Graphite and metals are the good electrical conductor among the refractories and others are all
electrical insulators
C. Refractories used for lining electrical furnaces should ordinarily have very low electrical
conductivity
D. Electrical conductivity of porous refractory material is low - Pick out the wrong statement?
A. Sand & coke is the main raw material for the manufacture of silicon carbide
B. Carbon refractories cannot be used in the furnaces operating under reducing conditions
C. Mullite can be obtained by the heating of alusite, kyanite or sillimanite
D. Silica occurs in nature in all cellular, amorphous or crystalline form - Pick out the wrong statement?
A. Insulating refractories used in place of regular refractory bricks are usually called light weight
refractories, and they have similar composition as heavy bricks
B. Graphite refractories are also called plumbago refractories
C. Superduty fireclay bricks correspond to a pyrometric cone equivalent of 26-28
D. Calcined magnesite is also called dead burnt magnesite - Refractory materials are never used in the construction of _________________?
A. Segar cones
B. Orton cones
C. Pressure vessels
D. Ovens & retorts - Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of ______________ percent respectively?
A. 80 and 20
B. 20 and 80
C. 50 and 50
D. 60 and 40 - A steel member used in the furnace construction to take the thrust of the brickwork is called___________________?
A. Buckstay
B. Breast wall
C. Armouring
D. Baffle - Cold crushing strength of refractories depends upon its_________________?
A. Composition
B. Texture
C. Firing temperature
D. All A., B. and C. - 10 to 30% magnesite is added to Chromite to produce chrome-magnesite refractories. Magnesite addition is mainly done to improve the _____________ of Chromite?
A. Spalling resistance
B. Refractoriness
C. Crushing strength
D. Resistance to slag
