This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Selection of Remelting Furnace”.
1. Which of the following furnaces is the primary method for melting the cast iron metal?
a) Electric arc furnace
b) Rotary furnace
c) Cupola furnace
d) Induction furnace
View Answer
Explanation: Cupola furnace is a furnace which is a primary method for melting the cast iron metal in the iron foundries. The cupola furnace has many unique features which are responsible for its widespread use as a melting unit. Cupola furnace is basically used for melting the scrap material or pig iron for production of several cast irons. It is also used for producing nodular and malleable cast irons.
2. In cupola melting furnace, an air-cooled vertical cylinder is used for cooling the cast iron materials.
a) True
b) False
View Answer
Explanation: In cupola melting furnace, a typical water cooled vertical cylinder is used which is generally lined with refractory material. The charge is introduced into the furnace through an opening half way up the vertical shaft. The charge mainly includes alternate layers of the material to be melted, flux and coke fuel.
3. The combustion section of the cupola furnace is also called as oxidizing zone.
a) True
b) False
View Answer
Explanation: The combustion section of the cupola furnace is also known as oxidizing zone. It is generally located between the upper part of the tuyeres and a theoretical level above it. The maximum height of this section can be up to 30 cm. The combustion takes place in this section by taking the free oxygen completely from the air and generating abundant heat.
4. Which of the following furnaces is mainly used for re-melting the steel metal?
a) Blast furnace
b) Electric arc furnace
c) Rotary furnace
d) Cupola furnace
View Answer
Explanation: A furnace is a tool used for melting the ferrous and nonferrous materials for the production of castings; different furnaces are used for melting and re-melting the ferrous and nonferrous materials. A blast furnace basically used for melting the iron ore to get pig iron, cupola furnace is used to produce cast iron metal and an electric arc furnace is used for re-melting the steel metal.
5. It is always advisable to have negligible amount of sulphur in the solid fuels used in the furnace.
a) True
b) False
View Answer
Explanation: The flue gases from the fuel makes direct contact with the metals used in the furnace, the type of fuel selected is very important. For example, many metals cannot tolerate sulphur in the fuel. Solid fuels basically create particulate matter which can interrupt the metal placed inside the furnace. To avoid this problem, gaseous or liquid fuel is used in the place of solid fuels.
6. Heat transfer in furnaces takes place only through the convection mode of heat transfer.
a) True
b) False
View Answer
Explanation: In furnaces, heat is transferred to the metal or stock by both the radiation and convection mode of heat transfer. Radiation mainly occurs from the flame, the furnace walls, roof and hot combustion products. And convection occurs due to the movement of hot gases over the metal surface. But at the high temperatures, the radiation mode of heat transfer is dominant in the furnaces.
7. Induction melting is very sensitive to the quality of materials as compared to the cupola or electric arc melting furnaces.
a) True
b) False
View Answer
Explanation: Induction melting produces very less fumes than that produced by the melting in an electric arc furnace or cupola melting furnaces. It is very easy to achieve melt composition in induction melting. And induction melting is very sensitive to the quality of materials used as compared to the cupola or electric arc melting furnaces.
8. Resistance furnace is a furnace that uses fuel gases like propane, acetylene or natural gas.
a) True
b) False
View Answer
Explanation: In resistance furnace, a current is passed through the charged material which results in high resistance that further causes heating of the charged material. The heating is mainly due to the radiation from the heating material. And fuel gases like propane, acetylene or natural gas are mainly used in oxy-fuel furnaces in which oxygen is combined with these gases to generate heat.
9. Gas reverberatory furnaces are mostly used for melting the ferrous materials for the production of castings.
a) True
b) False
View Answer
Explanation: Gas reverberatory furnaces are generally used for melting the non-ferrous metal in the casting foundries, as they gives large reservoir of liquid metal and ensures steady and reliable supply of metal to the foundry shop. So that, many large and medium sized foundry shops use them as central melting system.
10. Rotary furnaces are not suitable for large sized foundries in the production of castings.
a) True
b) False
View Answer
Explanation: Rotary furnaces are mostly used for small and medium sized foundries which uses cupola or induction furnaces. They are highly efficient than the other type of furnaces like reverb furnaces for small production. In these furnaces, heat transfer has occurred through both the radiation and direct contact between the molten metal and the refractory material.
Sanfoundry Global Education & Learning Series – Casting, Forming and Welding.
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