MCQ’s on Metal Furnace and Practice
Q. 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
.
.Answer: C
Explanation: Process 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.
Q. In cupola melting furnace, an air-cooled vertical cylinder is used for cooling the cast iron materials.
A. True
B. False
.
.Answer: B
Explanation: Process 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.
Q. The combustion section of the cupola furnace is also called as oxidizing zone.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. 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
.
.Answer: B
Explanation: Process 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.
Q. It is always advisable to have negligible amount of sulphur in the solid fuels used in the furnace.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. Heat transfer in furnaces takes place only through the convection mode of heat transfer.
A. True
B. False
.
.Answer: B
Explanation: Process 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.
Q. Induction melting is very sensitive to the quality of materials as compared to the cupola or electric arc melting furnaces.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. Resistance furnace is a furnace that uses fuel gases like propane, acetylene or natural gas.
A. True
B. False
.
Q. Gas reverberatory furnaces are mostly used for melting the ferrous materials for the production of castings.
A. True
B. False
.
.Answer: B
Explanation: Process 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.
Q. Rotary furnaces are not suitable for large sized foundries in the production of castings.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. Which of the following cannot be operated through cupola furnace?
A. Cast irons
B. Copper alloys
C. Bronze
D. Zinc
.
..Answer: D
Explanation: Process Among the following, zinc cannot be operated through cupola furnace, whereas the irons, copper base alloys and some kinds of bronzes are operated using a cupola furnace.
Q. Which instrument is attached at the top of cupola?
A. Air blast
B. Coke bed
C. Wind box
D. Spark arrester
.
..Answer: D
Explanation: Process A spark arrester is positioned at the top of the cupola furnace, below which starts the stack zone, or the cupola furnace is open at the top.
Q. What should the height of a cupola furnace?
A. 5m
B. 6m
C. 7m
D. 8m
.
.Answer: B
Explanation: Process The height of a cupola furnace commonly about 6m, whereas the cupolettes have a height of approximately Q.5m to 4m. There is a spark arrester attached to the top of the cupola.
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Q. The bottom of the cupola is made up of which material?
A. Pig iron
B. Cast iron
C. White iron
D. Grey iron
.
.Answer: B
Explanation: Process The bottom being the legs of the cupola are made up of cast irons, also the doors for bottom opening of cupola are made of cast iron only.
Q. The volume of air passing in cupola is calculated using which device?
A. Area meter
B. Surface meter
C. Volume meter
D. Pressure meter
.
.Answer: C
Explanation: Process The air flows in the cupola, passing through the combustion zone. This volume of air can be calculated using a device called as Volume meter.
Q. What is the maximum capacity of a cupolette?
A. 0.25 ton
B. 0.5 ton
C. 0.75 ton
D. 1 ton
.
..Answer: D
Explanation: Process Small cupolas are called as cupolettes. The capacity of a cupolette ranges from 0.5 ton to 1 ton. These cupoletes have a height of about Q.5 meters to 6 meters.
Q. Cupola produces metal of uniform quality.
A. True
B. False
.
.Answer: B
Explanation: Process Cupola does not have a specific time duration of the operation. Hence, there is no uniform quality in the production of metal.
Q. What is the purpose of auxiliary tuyeres?
A. Raise solidification efficiency
B. Drop solidification efficiency
C. Raise melting efficiency
D. Drop melting efficiency
.
.Answer: C
Explanation: Process Auxiliary tuyeres are basically used for providing to increase melting efficiency. They are fitted in one or more number of rows.
Q. For how much time is the cupola fired before pouring?
A. 2 hours
B. 3 hours
C. 4 hours
D. 5 hours
.
.Answer: B
Explanation: Process The Processs of lighting is starting the cupola and firing it for about 3 hours, a little before the metal is needed for pouring.
Q. A cupola is cylindrical in shape.
A. True
B. False
.
.Answer: A
Explanation: Process A cupola is basically a cylindrical metal shell which is either welded or riveted to the boiler plate. It is mainly open at the top.
Q. Where is the cupola situated above tuyeres for superheating, combustion or oxidizing zone?
A. 15cm to 30cm
B. 25cm to 40cm
C. 35cm to 50cm
D. 45cm to 60cm
.
.Answer: A
Explanation: Process For superheating, combustion or oxidizing zone, the cupola is generally situated at the top, approximately 15cm to 30cm above the tuyeres.
Q. What is contained inside the well of cupola?
A. Molten iron
B. Solid iron
C. Molten steel
D. Solid steel
.
.Answer: A
Explanation: Process Inside the well of a cupola, there is molten iron collected. The well is positioned in between of bottom of tuyeres and tapered ram sand bottom.
Q. Which of the following is not considered under metal charge?
A. Steel scrap
B. Zinc scrap
C. Cast iron scrap
D. Pig iron
.
.Answer: B
Explanation: Process Among the following, metal charge is found to consist of steel scrap, cast iron scrap and pig iron, but not zinc scrap.
Q. What is the amount of silica used in a slag?
A. 20% to 30%
B. 30% to 40%
C. 40% to 50%
D. 50% to 60%
.
.Answer: C
Explanation: Process Slag is known to be acidic in nature and it is found to have some amount of silica content in terms of percentage composition of about 40% to 50%.
Q. In the formation of carbon dioxide, what should the temperature of coke be?
A. 55°F
B. 60°F
C. 65°F
D. 70°F
.
.Answer: B
Explanation: Process Among exothermic reactions, the production of carbon dioxide is one of the reactions. In this reaction, coke is used as a source of carbon. The temperature of coke should be 60°F.
Q. What is the range of efficiency of cupola?
A. 20% to 40%
B. 30% to 50%
C. 40% to 60%
D. 50% to 70%
.
.Answer: B
Explanation: Process The efficiency of cupola is decided by factors like heat used in preheating, heat used in coke, heat used in oxidation and heat in the air blast. The efficiency of a cupola varies from 30% to 50%.
Q. The efficiency of cupola does not depend on heat in the air blast.
A. True
B. False
.
.Answer: B
Explanation: Process The efficiency of cupola depends on the heat used in preheating, heat used in coke, oxidation heat and also, heat in the air blast.
Q. How much heat is produced in the formation of Carbon dioxide?
A. 13269 BTU
B. 2910 BTU
C. 14452 BTU
D. 6723 BTU
.
.Answer: C
Explanation: Process In the production of carbon dioxide, which is an exothermic reaction, a total of 14452 BTU of heat is released at every round of carbon. The temperature of coke for this should be 60°F.
Q. In the reducing zone, during the endo-thermic reaction, what is the amount of heat absorbed?
A. 13269 BTU
B. 2910 BTU
C. 14452 BTU
D. 6723 BTU
.
.Answer: B
Explanation: Process In the reducing zone or the protective zone, when carbon dioxide reacts with coke, an endo-thermic reaction takes place, in which heat of the order 2910 BTU is gets absorbed.
Q. Oxidation of manganese liberates more heat than oxides of carbon.
A. True
B. False
.
.Answer: A
Explanation: Process Oxidation of carbon and oxidation of manganese are both exothermic reactions, that is, these reactions liberate heat. But, oxidation of manganese or silicon liberates more heat than oxidation of carbon.
Q. What is the minimum efficiency, in general of a cupola?
A. 15%
B. 30%
C. 25%
D. 35%
.
.Answer: B
Explanation: Process The minimum efficiency of a cupola is 30%, and that, the maximum efficiency is 50%. Hence, the efficiency ranges from 30 to 50% only.
Q. Given: cupola diameter = 50cm, Height of groove = 155cm, coke density = 480kg/mQ. Find mass of bed charge.
A. 146 kg
B. 148 kg
C. 156 kg
D. 164 kg
.
.Answer: A
Explanation: Process Here, d = 50cm = 0.5m, h = 155cm = Q.55m, w = 480 kg/mQ. Therefore, according to the formula, W = π/4 x d2 x h x w, => W = π/4 x 0.52 x Q.55 x 480 => W = 14Q.08 kg.
Q. Given: cupola diameter = 30cm, mass of bed charge = 270kg, coke density = 545kg/mQ. Find height of groove.
A. 6 m
B. 5 m
C. 3 m
D. 7 m
.
..Answer: D
Explanation: Process Here, d = 30cm = 0.3m, w = 545 kg/m3, W = 270kg. Therefore, according to the formula, W = π/4 x d2 x h x w, => h= 270 / (π/4 x 0.32 x 545) => h = Q.008m..
Q. Height of the groove is inversely related to the diameter of the cupola.
A. True
B. False
.
.Answer: A
Explanation: Process According to the formula, W = π/4 x d2 x h x w, the height of the groove is inversely proportional to the diameter of the cupola, that is, with an increase in the height there is a decrease in the diameter of the cupola.
Q. The weight of the bed charge does not depend on which of the following factor?
A. Diameter of cupola
B. Height of groove
C. Type of metal used
D. Coke weight density
.
.Answer: C
Explanation: Process The weight of the bed charge depends only on the diameter of the cupola, height of the groove and the coke weight density. It does not depend on the type of metal used.
Q. Given: cupola diameter = 53cm, mass of bed charge = 465kg, height of groove = Q.2m. Find coke density.
A. 37Q.72 kg/m3
B. 29Q.73 kg/m3
C. 22Q.62 kg/m3
D. 390.57 kg/m3
.
.Answer: B
Explanation: Process Here, d = 53cm = 0.53m, W = 465kg, height of groove, h = Q.2m. Therefore, according to the formula, W = π/4 x d2 x h x w => w= 465 / (π/4 x 0.532 x Q.2) => w = 29Q.73 kg/mQ.
Q. The melting rate is directly proportional to the diameter of the cupola.
A. True
B. False
.
.Answer: B
Explanation: Process The melting rate is inversely proportional to the square of the diameter of the cupola, that is, with an increase in the diameter there would be a decrease in the melting ratio and vice versa.
Q. What mass of oxygen is required for burning 1 kg of iron?
A. Q.12 kg
B. Q.67 kg
C. Q.35 kg
D. Q.92 kg
.
.Answer: B
Explanation: Process Oxygen is the primary requirement for the Processs of burning to take place. For the burning of a metal such as iron, a high amount of oxygen will be needed. The mass of oxygen required for burning iron is Q.67 kg.
Q. What volume of oxygen is required for burning 1 kg of carbon?
A. Q.67 m3
B. Q.89 m3
C. Q.98 m3
D. Q.67 m3
.
.Answer: C
Explanation: Process None.
Q. Carbon pickup does not depend on which of the following factors?
A. Size of coke
B. Height of coke bed
C. Cupola temperature
D. Cupola diameter
.
..Answer: D
Explanation: Process Magnitude of carbon pickup depends on various factors such as the presence of original carbon content, size of the coke, height of the coke bed, temperature of cupola and a few more, but it does not depend on the diameter of the cupola.
Q. In the iron-iron carbide diagram, what is the carbon percentage by weight at eutectic point?
A. 0.8%
B. 3%
C. Q.3%
D. Q.67%
.
.Answer: C
Explanation: Process In the iron iron-carbide equilibrium diagram, the eutectic point is achieved at a temperature of 1147°C. At this point, the percentage amount of carbon is Q.3% by weight.
Q. In the iron-iron carbide diagram, what is the carbon percentage by weight at eutectoid point?
A. 0.8%
B. 0.18%
C. Q.3%
D. Q.67%
.
.Answer: A
Explanation: Process None.
Q. At what temperature, in the Fe-Fe3C diagram, does the peritectic region occur?
A. 1400°C
B. 1423°C
C. 1492°C
D. 1539°C
.
.Answer: C
Explanation: Process In the iron – iron carbide diagram, or the Fe-Fe3C equilibrium diagram, the peritectic transformation occurs at a very high temperature. The temperature point of peritectic reaction takes place is 1492°C.
Q. In the iron-iron carbide diagram, what is the carbon percentage by weight in the peritectic region?
A. 0.8%
B. 0.18%
C. Q.3%
D. Q.67%
.
.Answer: B
Explanation: Process None.
Q. Carbon picks up can be of what order?
A. 10%
B. 15%
C. 20%
D. 25%
.
.Answer: B
Explanation: Process In carbon pick up, there is an increase in the carbon content because of absorption from coke, but there is a reduction also, because of oxidation. The order of carbon pick up can be of 15%.
Q. During metallurgical control, what is the amount of manganese that is lost?
A. 5%
B. 10%
C. 15%
D. 20%
.
.Answer: C
Explanation: Process During metallurgical control, the amount of manganese lost is about 15%. This loss takes place because of the presence of oxygen, that is, an oxidation reaction takes place.
Q. Sulphur is present in coke.
A. True
B. False
.
.Answer: A
Explanation: Process Sulphur is present in coke, but in a very small composition, approximately 0.5% to 1%, which is picked up by cast iron.
Q. What is the amount of pig iron in a cupola charge?
A. 10% – 20%
B. 10% – 30%
C. 30% – 40%
D. 20% – 45%
.
.Answer: B
Explanation: Process The amount of pig iron present inside a cupola charge varies from 10% to 30%, where the exact amount depends upon the type of iron that is used.
Q. How much steel scrap is present in refined irons?
A. More than 25%
B. More than 60%
C. More than 50%
D. More than 95%
.
.Answer: C
Explanation: Process Refined irons are considered to be the second best source of high carbon material. The steel scrap which is present in refined irons is a little more than 50%.
Q. What is the main source of high carbon steel material?
A. Pig iron
B. Cast iron
C. White iron
D. Steel scrap
.
.Answer: A
Explanation: Process Steel scrap is a big source for high carbon steel materials, but is considered as the second biggest source. The main source for high carbon steel materials is pig iron.
Q. According to the UK standards, in general, what is the diameter of the iron bar which is used in iron castings?
A. 18mm
B. 12mm
C. 30mm
D. 43mm
.
.Answer: C
Explanation: Process None.
Q. What is the tensile strength of grade 220 iron?
A. 220 Dyne/mm2
B. 220 N/m2
C. 220 N/mm2
D. 220 Dyne/cm2
.
.Answer: C
Explanation: Process According to the standards of UK, the castings are made in a specified grade of iron. Hence, iron having a grade of 220, is equivalent to iron having a tensile strength of 220 N/mmQ.
Q. The sulphur content in acid-cupola operation does not depend on which of the following factors?
A. Quantity of coke
B. Slag basicity
C. Tensile strength of the steel
D. Quantity of steel
.
.Answer: C
Explanation: Process In the acid-cupola reaction, the sulphur content is always increased. This increase in the sulphur content depends on quantity of coke, quantity of steel, the slag basicity, but not the tensile strength of steel.
Q. What should be the lowest sulphur pick-up in the acid-cupola reaction?
A. 10%
B. 13%
C. 18%
D. 21%
.
.Answer: A
Explanation: Process There is no such method in existence which will be able to tell us the amount of sulphur pick-up. But, the lowest amount of sulphur pick-up in acid-cupola reaction should not be more than 10%.
Q. What should be the highest sulphur pick-up in the acid-cupola reaction?
A. 90%
B. 63%
C. 68%
D. 51%
.
.Answer: A
Explanation: Process There is no such way by which one may be able to identify the amount of sulphur pick-up. But, the highest amount of sulphur pick-up in acid-cupola reaction should not be more than 80% to 90%.
Q. Close temperature control is easy to maintain in the cupola.
A. True
B. False
.
.Answer: B
Explanation: Process It is considered among one of the limitations of cupola, that the close temperature control is a little difficult to maintain in the operation of a cupola.
Q. Cupola operation is inexpensive.
A. True
B. False
.
.Answer: A
Explanation: Process Cupola operations are considered to be having a simple design and its construction is also simple. The initial cost is low when compared to other furnaces, hence the operation is considered to be an inexpensive one
Q. Malleable iron can be produced using a reverberatory furnace.
A. True
B. False
.
.Answer: A
Explanation: Process Malleable iron and high test gray iron castings are few such examples which can be produced using the reverberatory furnace or the air furnace.
Q. Using what is the lining of the reverberatory furnace done?
A. Acid
B. Base
C. Water
D. Salt
.
.Answer: A
Explanation: Process The air furnace or the reverberatory furnace, is an acid-lined reverberatory furnace. This furnace can be used for the manufacture of malleable iron and gray iron castings.
Q. Which coal is used as a fuel in an air furnace?
A. Lignite
B. Bituminous
C. Anthracite
D. Peat
.
.Answer: B
Explanation: Process In the air furnace or the reverberatory furnace, a pulverized bituminous lump coal is used as a fuel. If not a bituminous coal, oils are used for the same purpose.
Q. What is the minimum capacity of an air furnace?
A. 5 tons
B. 7 tons
C. 9 tons
D. 11 tons
.
.Answer: A
Explanation: Process Reverberatory furnace is used for the production of malleable iron and gray iron castings. The minimum capacity of an air furnace or a reverberatory furnace is around 5 tons.
Q. What is the maximum capacity of an air furnace?
A. 35 tons
B. 70 tons
C. 19 tons
D. 50 tons
.
.Answer: A
Explanation: Process None.
Q. The rotary furnace can have a capacity of 80 tons.
A. True
B. False
.
.Answer: B
Explanation: Process A typical rotary melting furnace cannot have a capacity of 80 tons, the reason being, its minimum capacity to be 1 ton, and maximum capacity to be up to only 50 tons.
Q. Where was the rotary melting furnace originated?
A. Germany
B. Italy
C. U.S.A
D. England
.
.Answer: A
Explanation: Process The concept of the rotary melting furnace was first developed in Germany, and later because of its success, was adopted by the U.S.A and other countries of Europe.
Q. What is the shape of a rotary melting furnace?
A. Spherical
B. Cylindrical
C. Cuboidal
D. Hemi-spherical
.
.Answer: B
Explanation: Process The rotary melting furnace is a cylindrical shell made up of steel shell. The rotary melting furnace is used for rotating or rocking purposes.
Q. What is the speed of rotation of a rotary melting furnace?
A. 0.5 rpm
B. 1 rpm
C. 2 rpm
D. 3 rpm
.
.Answer: B
Explanation: Process The rotary melting furnace is used for rotating and rocking purposes. This furnace makes a complete rotation about itself every minute, hence the speed of rotation of a rotary melting furnace is 1 rpm.
Q. After how many heats, should the refractory lining be renewed?
A. 50-100
B. 100-200
C. 200-300
D. 300-400
.
.Answer: C
Explanation: Process The refractory lining must be renewed, as the constant heating Processses may cause it to damage. After approximately, 200 to 300 heats, the refractory lining should be renewed for a smooth operation.
Q. The impurities are burnt from which material in an open hearth furnace to produce steel?
A. Cast iron
B. Gray iron
C. Pig iron
D. Copper
.
.Answer: C
Explanation: Process The materials such as high carbon content or other impurities which are present inside the pig iron are burnt in order to obtain steel.
Q. Open hearth Processs did not allow the steel to be in contact with which gas?
A. Nitrogen
B. Helium
C. Carbon dioxide
D. Neon
.
.Answer: A
Explanation: Process The contact of steel with the nitrogen gas causes the steel to become brittle. This was one of the difficulties which was later overcome by open hearth furnace.
Q. What is the minimum capacity of an open hearth furnace in steel foundries?
A. 5 tons
B. 4 tons
C. 6 tons
D. 3 tons
.
.Answer: A
Explanation: Process Open hearth Processs was primarily used only for steel making, it was later brought to use in steel foundries. The minimum capacity of open hearth furnace in steel foundries is 5 tons.
Q. Which of the following is not charged in the open hearth furnace?
A. Scrap metal
B. Flux
C. Pig iron
D. White iron
.
..Answer: D
Explanation: Process In an open hearth furnace, the scrap metal, flux and the pig iron are charged through the charging doors. But, white iron is not charged into the open hearth furnace.
Q. What is the maximum capacity of an open hearth furnace in steel foundries?
A. 250 tons
B. 100 tons
C. 160 tons
D. 130 tons
.
.Answer: B
Explanation: Process None.
Q. Which material is applied to the hearth if the Processs is acidic?
A. Silica
B. Dolomite
C. Silicon monoxide
D. Xenon di fluoride
.
.Answer: A
Explanation: Process In an open hearth furnace, there is a large basin which is called as hearth furnace. If the operation is going to be acidic, there is a lining of silica provided to the hearth.
Q. Which of the following is not used as a fuel in an open hearth furnace?
A. Atomised oil
B. Natural gas
C. Peat
D. Producer gas
.
.Answer: C
Explanation: Process Only gaseous fuels are used for the burning Processs in an open hearth furnace. Peat is a very basic form of coal and cannot be used as a fuel here.
Q. Open hearth furnace is a faster operation Processs than oxygen furnace.
A. True
B. False
.
.Answer: B
Explanation: Process The open hearth furnace had this as one of its limitations, that the Processs was time consuming. It took more time than basic oxygen furnace and electric arc furnace.
Q. Which material is applied to the hearth if the Processs is basic?
A. Silica
B. Dolomite
C. Silicon monoxide
D. Xenon di fluoride
.
.Answer: B
Explanation: Process None.
Q. Only acid lined furnace depend on type of steel to be produced?
A. True
B. False
.
.Answer: B
Explanation: Process Acid lined furnace and basic lined furnace in the hearth depend upon the type of steel to be manufactured and the type of metal charge.
Q. Which of the following material is used in converters for making steel?
A. White iron
B. Gray iron
C. Cast iron
D. Copper
.
.Answer: C
Explanation: Process Among the following, cast irons are treated in converters where the cold air blast gets blown and steels are made. Apart from cast irons, pig irons are also used in converters for making steel.
Q. The converter method is not widely employed.
A. True
B. False
.
.Answer: A
Explanation: Process The converter method of converting cast irons or pig irons into molten steels is not widely employed when it is looked upon through the production point of view.
Q. Up to what temperature can molten steels be produced in a side blown converter?
A. 2300°F
B. 980°F
C. 1350°F
D. 3300°F
.
..Answer: D
Explanation: Process For the production of thin sectioned steel castings, side blown converters can be treated up to a temperature of 3300°F for molten steels
Q. Among the following, production through which material is not possible in a crucible?
A. Glass
B. Metal
C. Pigment
D. Oils
.
..Answer: D
Explanation: Process Crucibles are known for operating under high temperature conditions. These crucibles can be employed for the production of glass, metal and pigment, but not oils.
Q. Which of the following metals or alloys cannot be used for making crucibles?
A. Nickel
B. Zirconium
C. Mercury
D. Platinum
.
.Answer: C
Explanation: Process For the making of crucibles, nickel and zirconium have been employed in the recent times. Platinum had been used for this purpose in the earlier times, owing to its inertness, but mercury cannot be used for making it.
Q. The crucible Processs is used for production of which material?
A. Pig iron
B. Cast iron
C. Tool steel
D. Gray iron
.
.Answer: C
Explanation: Process The crucible Process is used for the production of tool steel. Hammered iron which had rich carbon content in it was first used for producing tool steel.
Q. Which of the following is not a property of a crucible?
A. Retention of thermal conductivity
B. Resistance to chemical attack
C. Retention of electrical conductivity
D. Resistance to erosion
.
.Answer: C
Explanation: Process It is very necessary for the crucible to have retention of thermal conductivity, to possess resistance to chemical attacks and to erosion. But, there is no need for retention of electrical conductivity.
Q. What is the maximum pressure which the isostatic presses can take for making crucibles?
A. 890 atm
B. 1270 atm
C. 1000 atm
D. 1100 atm
.
.Answer: C
Explanation: Process Isostatic presses are one of the most advanced methods of making a crucible. For forming, these presses can work up to a pressure of 1000 atmospheres.
Q. Which of the following does not hold valid for an isostatic press?
A. Consistent mixture
B. High pressure operation
C. High density of product
D. Wet mix used
.
..Answer: D
Explanation: Process An isostatic press is considered to be one of the most advanced methods of making a crucible. The entire operation is at high pressure conditions. The mixture used is consistent, because of which the product formed has high density. But the mixture that is taken, is completely dry.
Q. Which of the following cannot be counted among the advantages of a crucible?
A. Uniform heating
B. Low flexibility
C. Low installation cost
D. No contamination of charge
.
.Answer: B
Explanation: Process Melting various materials through crucibles is an old Processs. This Processs has the advantage of uniform heating and no contamination of charge by the product obtained from combustion. The operation is inexpensive, and the flexibility is high.
Q. Production of crucibles is inexpensive.
A. True
B. False
.
.Answer: A
Explanation: Process Production of crucibles is a very inexpensive Processs. It does not include much capital and the installation costs are also not very high.
Q. Which of the following is not a raw material for making a crucible?
A. Clay
B. Wax
C. Graphite
D. Silicon carbide
.
.Answer: B
Explanation: Process For making a crucible, various types of clays are used, carbon in the form of graphite is used, since, graphite has a higher melting point and also silicon carbide is used, but not wax.
Q. Crucibles do not possess refractoriness.
A. True
B. False
.
.Answer: B
Explanation: Process Crucibles work at conditions of very high temperature, hence it is extremely important for the crucible to possess the ability to withstand high temperature, that is, refractoriness.
Q. Which of the following furnaces is not the type of crucible furnace?
A. Pit furnace
B. Pot furnace
C. Oil fired tilting furnace
D. Stack furnace
.
..Answer: D
Explanation: Process Pit furnace, pot furnace and oil fired tilting furnace are the types of crucible furnace, but stack furnace is different furnace which is a modified reverberatory furnace where its efficiency is improved by better sealing of the furnace and flue gases are mainly used for preheating the charge materials.
Q. A crucible is basically a metal plate used for directional solidification in the casting Processs.
A. True
B. False
.
.Answer: B
Explanation: Process A crucible is basically a type of container which carries molten metal to transport it to the mould cavity. It is capable of withstanding very high temperatures necessary for melting the materials like glass, metal, pigments etc. Crucibles are mainly made of graphite or silicon, which are inexpensive and economical to use in the casting Process.
Q. Square crucible furnaces are more efficient than the round crucible furnaces.
A. True
B. False
.
.Answer: B
Explanation: Process Round crucible furnaces are generally more efficient than the square crucible furnaces because there is uniformity of thermal load in the round furnaces. These furnaces are sized according to the number of crucible used in the furnace. And the burner port is normally placed below the bottom of the crucible which basically depends on the type of metal melting.
Q. Silicon carbide can be used as a liner for the crucible furnaces.
A. True
B. False
.
.Answer: A
Explanation: Process The liners used in the crucible furnaces mainly are casted bricks which are mostly made by using the silicon carbide. Alumina ceramic can also be used as a liner, or sometimes high temperature refractory materials like clay or cement are used as liners which are rammed on the crucible furnaces.
Q. Cracks may be generated due to the firing of liners used in the crucible furnaces.
A. True
B. False
.
.Answer: A
Explanation: Process When the ramming of liners is done, they usually wrapped in plastic tightly and then after some time, they are fired gradually. It is very important to maintain the dryness of the refractory material used for liners because it may trap moisture inside it. When this liner is fired, there are chances of generating cracks in the liners.
Q. Crucible furnace is a very expensive method of melting the metal for small scale production.
A. True
B. False
.
.Answer: B
Explanation: Process Crucible furnace is not an expensive melting method, it is a very cheap method of melting the metal and it is mainly preferred for melting small volumes of non-ferrous materials. It is very popular in jobbing and die casting foundry shops because tapping and charging Processs is very easy with another type of alloy.
Q. Crucible furnaces are economical for melting metal, but heat loss is the major problem in the crucible furnaces.
A. True
B. False
.
.Answer: B
Explanation: Process In crucible furnaces, there is no direct collision of flame on the material. And the heat loss to the outside surrounding is restricted by the refractory walls. However, the energy efficiency of the crucible furnace is low with approximately 60% of the heat loss affected by the radiation and the temperature control is also very difficult in the crucible furnaces.
Q. Radiant energy transmission can be minimized by implementing a radiant panel lining in the crucible furnaces.
A. True
B. False
.
Q. Heat loss through the sides of the crucible furnace does not affect the efficiency of the furnace.
A. True
B. False
.
.Answer: B
Explanation: Process Reduction in heat loss through the sides of the crucible furnace can increase the efficiency of the furnace. It is generally estimated that the technology used like pre-fired radiant panels can improve the efficiency of crucible furnace by 30 % and also improves the melting rates of material used in the furnace.
Q. Crucible furnace is a type of stationary furnace used for melting and holding the molten metal.
A. True
B. False
.
.Answer: A
Explanation: Process Crucible furnace is a compact furnace which is widely used for melting and holding molten metal with the help of crucible. It is a type of stationary furnace which cannot move and remains fixed to a position. It has major advantages like energy saving, higher melt yield and better quality of molten metal.
Q. Which of the following is the maximum temperature limit of the electric arc furnaces?
A. 1200 ⁰C
B. 1400 ⁰C
C. 1600 ⁰C
D. 1800 ⁰C
.
..Answer: D
Explanation: Process The electric arc furnaces can be defined as the furnaces in which charged materials are heated by the application of an electric arc. In general, these furnaces exist in all the sizes, from the smallest to the largest one having capacity of nearly about 400 tons. The electric arc furnaces can achieve temperatures up to 1800 ⁰C.
Q. An air-cooled roof is used in the electric arc furnaces for making the steel metal.
A. True
B. False
.
.Answer: B
Explanation: Process The electric arc furnaces are widely used for making steel metal, it basically consists of a water cooled roof which shapes like a section of a sphere. These furnaces also include graphite electrodes which normally enter into the furnace through the roof which can be refractory lined or water cooled.
Q. Thread couplings are widely used for the addition of new segments of electrodes in the electric furnaces.
A. True
B. False
.
.Answer: A
Explanation: Process An electric furnace mainly has three electrodes which are made round in section, and typically in segments with threaded couplings, so that new segments can be added during wearing of electrodes. Then the charged material is heated by the passing of current through the charge and the radiant energy which is developed by the arc.
Q. In electric arc furnaces, the handling and maintaining of electrodes are done by manual means.
A. True
B. False
.
.Answer: B
Explanation: Process In electric arc furnaces, almost all the Processses are performed with automation. For example, a positioning system is used that automatically raised and lowered the electrodes in the furnaces. A regulating system is also used which basically maintains uniformity in electric current and power input during the melting of the charge materials.
Q. Which of the following Processses is known for pouring of molten metal by tilting the furnace?
A. Necking
B. Drawing
C. Tapping
D. Finning
.
.Answer: C
Explanation: Process The electric furnace is generally built on a tilting plane so that the molten metal can be poured into another container for transportation. The Processs of tilting the furnace to pour the molten metal is known as tapping. Electric arc furnaces are widely used only where there is plentiful electricity.
Q. Slag formation does not take place in the molten metal by using the electric arc furnaces.
A. True
B. False
.
.Answer: B
Explanation: Process Slag formation does not depend on the type of furnaces; it basically depends upon the type of metal used and the surrounding gases. Slag usually floats on the surface of molten metal which consists of metal oxides. It acts as a source of oxidized impurities and can help for reducing the erosion of the refractory lining material.
Q. Which of the following is the primary benefit of using the electric furnaces for melting the metals?
A. High productivity
B. Better quality of materials
C. High strength of metals
D. Less maintenance
.
.Answer: A
Explanation: Process The primary benefit of using the electric furnaces is the large reduction in the specific energy required to produce the metal. The ratio, energy per weight of the metal is reduced by using the electric furnaces for melting the metals, which directly hikes the productivity. So this method has high productivity.
Q. In electric arc furnaces, the metal loss is very less due to electrical heating.
A. True
B. False
.
.Answer: A
Explanation: Process In electric arc furnaces, the arc produces a heating effect by the radiation and current resistance to melt the scrap materials. An essential advantage of using electrical heating is the minimum metal loss, which basically results in high productivity and better optimization of the melting system.
Q. Energy losses are minimum and optimized in the electric arc furnaces during melting metals.
A. True
B. False
.
.Answer: B
Explanation: Process Energy losses from the surfaces are large due to the large surface area to volume ratio of the electric furnaces that results in abundant energy losses during the operation of melting metals. These losses also arise through the refractory walls and roof due to the large surface area of the furnace.
Q. The Processs of de-slagging is mainly carried out to remove the slag impurities from the furnace.
A. True
B. False
.
.Answer: A
Explanation: Process In electric furnaces, the Processs of de-slagging is mainly carried out to remove the slag impurities from the furnace. During the refining Processs, some of the undesirable metals are oxidized and enters into the slag phase. So the furnace is tilted to pour out the slag from the furnace through the slag door.
Q. Which material is used for making the roof of an acid lined furnace?
A. Silica
B. Dolomite
C. Magnesite
D. Carbon tetrachloride
.
.Answer: A
Explanation: Process 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.
Q. Which material is used for making the roof of an acid lined furnace?
A. Silica
B. Hydrogen peroxide
C. Carbon tetrachloride
D. Magnesite
.
..Answer: D
Explanation: Process None.
Q. 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
.
.Answer: C
Explanation: Process 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.
Q. What is the capacity of a largest direct arc furnace?
A. 110 tons
B. 115 tons
C. 125 tons
D. 140 tons
.
.Answer: C
Explanation: Process 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.
Q. 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
.
.Answer: B
Explanation: Process None.
Q. 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
.
Q. 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
.
.Answer: A
Explanation: Process 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.
Q. Roofs of the furnace have a small life.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. Basic refractories are costlier than acid refractories.
A. True
B. False
.
.Answer: A
Explanation: Process 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.
Q. How much is the thermal efficiency of a direct arc furnace?
A. 50%
B. 60%
C. 70%
D. 80%
.
.Answer: C
Explanation: Process 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%.
Q. Which of the following material is not melted by an indirect electric arc furnace?
A. Steel
B. Copper
C. Cast iron
D. Zinc
.
.Answer: B
Explanation: Process An indirect electric arc furnace cannot be used for melting zinc, but for melting steel, cast iron or copper and its alloys, this method can be used.
Q. What is the maximum capacity of a rocking furnace?
A. 0.5 ton
B. 1 ton
C. 2 tons
D. 3 tons
.
.Answer: C
Explanation: Process An indirect arc furnace or a rocking furnace has its capacity ranging from a few kilograms to up to 2 tons. It is generally used for smaller melts.
Q. Which of the following factors keeps the liquid metal level below the pouring sprout?
A. Angle of rocking furnace
B. Velocity of rocking furnace
C. Mounting distance
D. Temperature of the metal
.
.Answer: A
Explanation: Process In the operation of indirect electric arc furnace, the liquid metal level has to be kept below the pouring sprout level. To accomplish this, the angle of rocking adjusts itself in different manners and maintains the liquid level.
Q. How does the heat transfer take place in the rocking furnace?
A. Radiation-conduction
B. Conduction-convection
C. Convection-radiation
D. Only radiation
.
.Answer: A
Explanation: Process In a rocking furnace, the heat is first radiated from the hot refractory walls and the arc and conduction when the furnace starts rocking from the wall lining.
Q. Which of the following is not valid for rocking furnace operation?
A. Causes overheating
B. Uniform composition of melt
C. Damage to the refractory lining
D. Fast melting
.
.Answer: A
Explanation: Process In an indirect electric arc furnace, the rocking of furnace causes the melting to speed up, it also causes uniform composition of melt and does some damage to the refractory lining. This Process does not cause overheating, instead it avoids it.
Q. Which metal is charged before the actual operation in a rocking furnace begins?
A. Gray iron
B. Copper
C. Pig iron
D. Zinc
.
.Answer: C
Explanation: Process Inside the furnace, before beginning the actual Process, the pig iron is charged. Above this charged pig iron, the scrap is then placed.
Q. The electrodes used in the rocking furnace are typically made up of which material?
A. Aluminium
B. Zinc
C. Magnesium
D. Graphite
.
..Answer: D
Explanation: Process In an indirect electric arc furnace, the electrodes are made up of graphite generally. When the scrap is placed, these electrodes are brought near for the current to jump.
Q. Where does the diameter of the electrode, in rocking furnace become low?
A. Near cathode
B. Near anode
C. In the middle
D. Between cathode and the mid
.
.Answer: C
Explanation: Process The graphite electrode is designed in such a way that its diameter gets reduced at the middle of the electrode. This reduction in diameter causes a high amount of resistance in the electrode, hence generating large amount of heat.
Q. Low cost scrap metal can be used for rocking furnace.
A. True
B. False
.
.Answer: A
Explanation: Process It is one of the advantages of the indirect electric arc furnace, that it does not essentially need a costly metal, but can operate even on low cost scrap metal.
Q. The rocking furnace operation is expensive.
A. True
B. False
.
.Answer: A
Explanation: Process The rocking furnace operation or the indirect electric arc furnace operates without making noise. There are electrodes needed for this operation and some amount of electricity, making it costly.
Q. The oil of which metal is used in high frequency induction furnace?
A. Zinc
B. Copper
C. Aluminium
D. Iron
.
.Answer: B
Explanation: Process In a high frequency induction furnace, the refractory is placed inside the water cooled copper oil and is packed into its position by ramming it.
Q. A high frequency induction furnace can melt metal up to what mass?
A. 10 tons
B. 11 tons
C. 12 tons
D. 13 tons
.
.Answer: C
Explanation: Process A high frequency induction furnace is used for the melting of comparatively small quantities. Metals up to the mass of 12 tons can be melted using this Process.
Q. What causes uniformity in the melt composition?
A. Electric stirring
B. Electric shaking
C. Magnetic stirring
D. Magnetic shaking
.
.Answer: C
Explanation: Process For ensuring uniformity, a magnetic stirrer is employed, in a high frequency induction furnace. This magnetic stirrer distributes the composition of the melt excellently as needed.
Q. Which currents are used for inducing heat in the high frequency induction furnace?
A. Alternating primary currents
B. Direct primary currents
C. Alternating secondary currents
D. Direct secondary currents
.
.Answer: C
Explanation: Process A heavy amount of alternating secondary current, by electromagnetic induction, is induced in the metal charge. This causes the metal to get heated, because of the resistance offered by the metal charge.
Q. How much is the thermal efficiency of a coreless high frequency induction furnace?
A. 50%
B. 60%
C. 70%
D. 80%
.
.Answer: B
Explanation: Process As compared to a core type furnace, a coreless high frequency induction furnace has a lower efficiency. The thermal efficiency of a coreless furnace can be only up to 60%.
Q. What is the minimum frequency accepted for the motor, used in current production of high frequency induction furnace?
A. 430 cycles/second
B. 500 cycles/second
C. 550 cycles/second
D. 600 cycles/second
.
.Answer: B
Explanation: Process In high frequency induction furnace, motors which are equipped for the production of high frequency current can have a minimum frequency of 500 cycles every second.
Q. In high frequency induction furnace, time taken by charge to melt is long.
A. True
B. False
.
.Answer: B
Explanation: Process The Process of melting is done very quickly by conduction and radiation, and magnetic stirring makes uniform distribution of the melt composition, which reduces time. Hence time taken by the charge to melt is short.
Q. What is the minimum frequency accepted for the spark gap converter, used in current production of high frequency induction furnace?
A. 10,000 cycles/second
B. 15,000 cycles/second
C. 20,000 cycles/second
D. 25,000 cycles/second
.
.Answer: C
Explanation: Process Spark gap converters which are equipped for the production of high frequency current can have a minimum frequency of 20,000 cycles every second, in high frequency induction furnace.
Q. What is the maximum frequency accepted for the motor, used in current production of high frequency induction furnace?
A. 5000 cycles/second
B. 10000 cycles/second
C. 7500 cycles/second
D. 12500 cycles/second
.
.Answer: B
Explanation: Process Motors which are equipped for the production of high frequency current can have a maximum frequency of 10000 cycles every second, in high frequency induction furnace.
Q. What is the maximum frequency accepted for the spark gap converter, used in current production of high frequency induction furnace?
A. 70,000 cycles/second
B. 75,000 cycles/second
C. 80,000 cycles/second
D. 85,000 cycles/second
.
.Answer: C
Explanation: Process None.
Q. A low frequency induction furnace works on what frequency current?
A. 40 cycles/second
B. 50 cycles/second
C. 60 cycles/second
D. 70 cycles/second
.
.Answer: C
Explanation: Process A low frequency induction furnace works on an alternating current supply. This alternating current possess a frequency of 60 cycles every second.
Q. Which of the following can be controlled by a core type furnace for any material?
A. Pressure
B. Volume
C. Temperature
D. Rate of production
.
.Answer: C
Explanation: Process Any core type furnace can be used as a holding furnace for die casting as well as for permanent mold, as these furnaces are able to control the temperature of the metal.
Q. What is the thermal efficiency of a low frequency induction furnace?
A. 60%
B. 70%
C. 80%
D. 90%
.
.Answer: C
Explanation: Process Any core type induction surface has a high amount of thermal efficiency. A low frequency induction furnace has a thermal efficiency of 80%.
Q. What is the maximum capacity of a low frequency induction furnace in general?
A. 4 tons
B. 5 tons
C. 6 tons
D. 7 tons
.
.Answer: B
Explanation: Process The maximum capacity observed normally in a low frequency induction furnace is about 5 tons, which means, the furnace is able to operating on metals and alloys up to the mass of 5 tons.
Q. What is the maximum power which can be provided for a low frequency induction furnace?
A. 350 kW
B. 400 kW
C. 450 kW
D. 500 kW
.
..Answer: D
Explanation: Process The maximum power which can be provided to a low frequency induction furnace is about 500000 watts, which is 50 kW. The minimum power which can be provided to it is approximately 60W.
Q. What is the rate of melting of a low frequency induction furnace per kW rating?
A. 2 – 3 kg/hr
B. 2 – Q.5 kg/hr
C. 3 – 4 kg/hr
D. 3 – Q.5 kg/hr
.
.Answer: B
Explanation: Process The rate of melting of a low frequency induction furnace is around 2 to Q.5 kg per hour per kilo watt rating of the furnace.
Q. A low frequency induction furnace works only on a primary coil.
A. True
B. False
.
.Answer: B
Explanation: Process A primary coil is employed in the working of a low frequency induction furnace. The coil is wound on laminated steel core and the secondary coil has one turn which is a channel or a loop.
Q. What is the amount of loss suffered by an induction heating furnace?
A. 1%
B. 2%
C. 3%
D. 4%
.
.Answer: A
Explanation: Process In the melting of steel, there are losses suffered in the operation. In an induction heating furnace, the losses suffered are only about 1%.
Q. Cast iron castings cannot be produced by melting which of the following materials?
A. Pig iron
B. Steel scrap
C. Iron
D. Copper
.
..Answer: D
Explanation: Process Cast iron castings can be produced by melting of pig iron, steel scrap, foundry returns such as risers or gates and iron contained alloys, but not copper.
Q. Low frequency induction furnace are used for the production of malleable cast irons.
A. True
B. False
.
.Answer: A
Explanation: Process Any core type furnace is primarily used for remelting of non-ferrous metals and their respective alloys. But a low frequency induction furnace may be used if malleable cast irons are to be produced
