Explore topic-wise InterviewSolutions in .

Right option is (d) 1800 ⁰C

The best I can explain: 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.

Correct option is (b) False

For explanation: 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.

Correct OPTION is (b) False

The best I can EXPLAIN: 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.

Right option is (d) Stack furnace

For explanation I would say: 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.

Right option is (C) 1000 atm

For explanation I WOULD say: 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.

The CORRECT option is (d) WHITE iron

To explain: 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.

The correct OPTION is (a) Acid

The best EXPLANATION: 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.

Right answer is (b) False

Explanation: 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.

Correct answer is (b) 2910 BTU

Easiest explanation: 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.

Correct answer is (a) NITROGEN

Explanation: 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.

The correct choice is (a) True

Best explanation: 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.

The correct option is (b) BITUMINOUS

For EXPLANATION I WOULD say: 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.

Correct choice is (b) 60°F

To EXPLAIN: 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.

The CORRECT OPTION is (a) 0.8%

To ELABORATE: NONE.

Correct ANSWER is (c) Raise melting EFFICIENCY

Explanation: Auxiliary TUYERES are basically used for providing to increase melting efficiency. They are FITTED in one or more number of ROWS.

Right answer is (c) 20,000 CYCLES/second

To elaborate: 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.

Right option is (C) In the MIDDLE

Easiest explanation: 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.

The correct ANSWER is (a) True

For explanation: 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.

Correct option is (a) SHELL

For explanation I would say: Here, the QUESTION mark is REPRESENTING the OUTER shell of the converter. Inside the shell, then lies the refractory lining.

Right answer is (a) True

The explanation is: 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.

The correct OPTION is (a) 146 kg

The EXPLANATION is: Here, d = 50cm = 0.5m, h = 155CM = 1.55m, w = 480 kg/m^3. Therefore, according to the formula, W = π/4 X d^2 x h x w, => W = π/4 x 0.5^2 x 1.55 x 480 => W = 146.08 kg.

Correct answer is (c) Refractory lining

Explanation: In this given figure of a ROTARY melting FURNACE, the question MARK is depicting the refractory lining, which is just below the STEEL shell. This lining has to be RENEWED after a certain usage.

The CORRECT OPTION is (d) 500 kW

The best I can EXPLAIN: 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.

The CORRECT CHOICE is (B) 40,000 kVA

To ELABORATE: NONE.

Right answer is (a) High PRODUCTIVITY

The explanation is: 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.

The correct option is (a) True

For EXPLANATION: Malleable iron and HIGH TEST GRAY iron CASTINGS are few such examples which can be produced using the reverberatory furnace or the air furnace.

Right option is (d) Hearth

Easy explanation: The question mark in the picture is DEPICTING a hearth. The given figure is that of an AIR FURNACE or a reverberatory furnace. This hearth finds its place above the FIRE bridge in the apparatus.

The correct answer is (c) More than 50%

For explanation: 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%.

Right ANSWER is (c) 4.3%

To explain I WOULD say: 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 4.3% by weight.

The correct CHOICE is (b) False

Easy 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.

Right option is (a) True

The best explanation: 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.

Right choice is (a) True

Explanation: Radiant ENERGY transmission is generally minimized by having a radiant panel lining in the crucible FURNACES, which BASICALLY MERGES high-alumina radiant panel with the LOW thermal mass insulating material. This produces a surface area that raises radiant energy transfer to the outer surface area of the crucible.

Correct option is (a) Angle of rocking furnace

To explain I WOULD say: 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.

The CORRECT OPTION is (B) Exhaust box

To explain: None.

Right option is (c) 200-300

Easy EXPLANATION: The refractory lining must be renewed, as the constant HEATING processes MAY cause it to DAMAGE. After approximately, 200 to 300 heats, the refractory lining should be renewed for a smooth operation.

The correct choice is (c) Fire bridge

To explain I would SAY: The question mark in the picture is DEPICTING a fire bridge. This bridge is used for holding the molten METAL. The given figure is that of an air furnace or a REVERBERATORY furnace.

The CORRECT option is (b) Skimming door

To elaborate: The given figure is that of an AIR FURNACE or a reverberatory furnace. The QUESTION MARK in the picture is depicting a skimming door.

The CORRECT choice is (a) 5 tons

To explain I would say: 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.