Refractory Technology

31. Cermets are combination of ceramic and metallic materials due to which they have high strength & resistance to high temperature. Cermets are used in the

1. Hearth of the blast furnace
2. Nuclear reactors, missiles & space crafts
3. Insulation of high temperature furnaces
4. Roof of electric furnaces

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32. Chemically, mullite refractories is

1. 3Al2O₃.2SiO₂
2. Al2O₃
3. ZrSO₄
4. ThO₂

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33. Chrome magnesite brick is not used for lining the

1. Hearth of soaking pits
2. Bottom hearth of reheating furnace
3. Coke oven regenerator
4. Burning zone of limestone rotary kilns

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34. Chrome magnesite bricks are

1. Acidic in nature
2. Neutral in nature
3. Having higher RUL than silica bricks
4. Made by mixing 30% Chromite and 70% Periclase

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35. Chrome magnesite bricks are used in the

1. Side walls of soaking pits and arc furnaces
2. Copper melting furnaces & converters
3. Burner block of glass tanks
4. All (A), (B) and (C)

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36. Chrome magnesite is not used in the

1. Inner lining of L.D. converter
2. Aluminium melting furnaces
3. Wear out lining of steel melting furnaces
4. All (A), and (B) and (C)

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37. Chromite refractories

1. Are bonded with lime and clay
2. (Free from silica) have better thermal fatigue resistance than silica and magnesite refractories.
3. Are resistant to basic slag
4. All (A), (B) and (C)

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38. Chromite refractories are

1. Acidic refractory
2. Neutral refractory
3. Basic refractory
4. Fired at a temperature of 600°C only

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39. Chromite refractories are used in

1. Bottom of soaking pits
2. Between acid & basic linings in basic open hearth furnaces to prevent their chemical action with each other
3. Both (A) & (B)
4. Neither (A) and (B)

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40. Cold crushing strength of a refractory does not depend upon its

1. Shape
2. Composition
3. Firing temperature
4. Texture

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