Refractory Technology

191. Which is the stable form of silica between 1470°C and the melting point 1713°C?

1. Cristobalite
2. Tridymite
3. Quartz
4. None of these

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192. Which is the stable form of silica upto 1470°C?

1. Quartz
2. Cristobalite
3. Tridymite
4. None of these

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193. Which of the following bricks has the most close values of RUL and PCE?

1. Silica bricks
2. Fireclay bricks
3. High alumina bricks
4. Tar dolomite bricks

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194. Which of the following bricks should not be used, if the furnace is to be used intermittently?

1. Firebricks
2. Silica bricks
3. Silicon carbide bricks
4. Sillimanite

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195. Which of the following consumes the maximum tonnage of refractories annually in an integrated steel plant?

1. Soaking pits
2. Reheating furnace
3. L.D. converter
4. Rotary lime kiln

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196. Which of the following does not occur during firing/burning of refractories?

1. Removal of water of hydration
2. Vitrification
3. Decrease in crushing strength
4. Development of stable mineral form

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197. Which of the following has the lowest electrical resistivity?

1. Graphite
2. Fireclay
3. Alumina
4. Zircon

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198. Which of the following impurities reduces the refractoriness of magnesite bricks?

1. Al2O₃
2. CaO
3. SiO₂
4. All (A), (B) & (C)

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199. Which of the following is not a high alumina refractory material?

1. Kyanite
2. Sillimanite
3. Diaspore
4. Periclase

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200. Which of the following is not a neutral refractory?

1. Silicon carbide
2. Magnesite
3. Chromite
4. Graphite

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