# Casting Questions and Answers – Direct Arc Furnace

This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Direct Arc Furnace”.

1. Which material is used for making the roof of an acid lined furnace?
a) Silica
b) Dolomite
c) Magnesite
d) Carbon tetrachloride

Explanation: A very heavy steel shell is equipped in making the roof, with the help of refractory bricks. To this, silica is added when the furnace is acid lined.

2. Which material is used for making the roof of an acid lined furnace?
a) Silica
b) Hydrogen peroxide
c) Carbon tetrachloride
d) Magnesite

Explanation: None.

3. What is the minimum transformer power supply needed by the direct arc furnace?
a) 600 kVA
b) 700 kVA
c) 800 kVA
d) 900 kVA

Explanation: For the remelting of steel, a high amount of power supply is needed by the direct arc furnace. The minimum transformer power supply needed by the furnace is 800 kVA.

4. What is the capacity of a largest direct arc furnace?
a) 110 tons
b) 115 tons
c) 125 tons
d) 140 tons

Explanation: The direct arc furnace is widely used in the steel foundries for the remelting unit. The largest direct arc furnace is found to have a capacity of 125 tons for remelting steel.

5. What is the maximum transformer power supply needed by the direct arc furnace?
a) 35,000 kVA
b) 40,000 kVA
c) 45,000 kVA
d) 50,000 kVA

Explanation: None.

6. What is typically the diameter of a direct arc furnace?
a) Up to 5m
b) Up to 6m
c) Up to 7m
d) Up to 8m

Explanation: The direct arc furnace is widely used in the steel foundries for remelting steels of various compositions. In general, the diameter of a direct arc furnace is found to be only up to 6 meters.

7. What would be the amount of current carried by the electrode for a direct arc furnace having capacity 50 tons?
a) 25 kilo amperes
b) 25 mega amperes
c) 25 micro amperes
d) 25 nano amperes

Explanation: For a direct arc furnace having a capacity of around 50 tons, the electrode would carry a current of approximately 25,000 amperes, which is 25 kA. These electrodes can be moved upwards and downwards.

8. Roofs of the furnace have a small life.
a) True
b) False

Explanation: The roofs of the furnace bear with many damages during the operations. A few spare roofs should always be available since the roof does not have a very long life.

9. Basic refractories are costlier than acid refractories.
a) True
b) False

Explanation: To be operating in a basic refractory, it is advantageous as the inferior scrap can be used for the production of good quality steel. Hence, basic refractories are costlier than acid refractories.

10. How much is the thermal efficiency of a direct arc furnace?
a) 50%
b) 60%
c) 70%
d) 80%

Explanation: In a direct arc furnace, the analysis of the melt can be accurately calculated and its efficiency can go as high as up to 70%.

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