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Right option is (b) 5 TONS

The best explanation: 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.

The correct answer is (b) Copper

To EXPLAIN I WOULD say: 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.

Right CHOICE is (a) True

Easy explanation: 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.

The correct ANSWER is (B) False

The explanation: In electric arc furnaces, almost all the processes 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.

Right choice is (b) Low FLEXIBILITY

To elaborate: Melting various MATERIALS through crucibles is an old PROCESS. This process 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.

Right ANSWER is (a) True

To explain I would say: 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.

Correct choice is (c) CAST iron

The best I can EXPLAIN: 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.

Right option is (d) 7 m

Explanation: Here, d = 30cm = 0.3m, w = 545 kg/m^3, W = 270KG. THEREFORE, according to the formula, W = π/4 x d^2 x h x w, => h= 270 / (π/4 x 0.3^2 x 545) => h = 7.008m.

The correct option is (c) 220 N/mm^2

Easiest explanation: 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/mm^2.

Correct ANSWER is (C) 60 cycles/second

Easiest explanation: A low frequency INDUCTION furnace WORKS on an alternating current supply. This alternating current possess a frequency of 60 cycles every second.

Right answer is (B) 2 – 3.5 kg/hr

For explanation I would say: The rate of MELTING of a LOW frequency INDUCTION furnace is around 2 to 3.5 kg per hour per kilo WATT rating of the furnace.

Right choice is (b) False

Easiest explanation: 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.

The correct option is (b) False

To explain: 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.

Correct OPTION is (b) 219.5 KG

Best explanation: According to the question, d = 65CM = 0.65m, h = 135cm = 1.35m, w = 490 kg/m^3. THEREFORE, according to the formula, W = π/4 x d^2 x h x w => W = π/4 x 0.65^2 x 1.35 x 490 => W = 219.5 kg.

The correct option is (C) Retention of ELECTRICAL CONDUCTIVITY

For explanation: 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.

Correct CHOICE is (b) False

Best explanation: 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.

Correct OPTION is (d) Spark arrester

Easiest explanation: 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.

Right choice is (b) False

The best 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.

Correct answer is (d) 3300°F

Easiest explanation: For the PRODUCTION of THIN sectioned steel castings, side BLOWN converters can be treated up to a TEMPERATURE of 3300°F for MOLTEN steels.

The correct choice is (b) Tuyeres

For explanation I WOULD say: In the following FIGURE, the question mark is representing the PART called tuyeres. Tuyeres are situated at the left of the side BLOWN converters, and air is blown through the charge from left to right.

Right answer is (c) Type of metal USED

To explain: 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.

Correct option is (c) 14452 BTU

The explanation: 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.

The correct choice is (d) 1 ton

Easiest explanation: 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 4.5 meters to 6 meters.

Right choice is (c) 80%

For explanation I WOULD SAY: Any core TYPE induction surface has a HIGH amount of thermal efficiency. A low frequency induction furnace has a thermal efficiency of 80%.

Right ANSWER is (b) Wax

Explanation: 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.

The correct answer is (c) Wind box

Easiest explanation: In the shown figure, the QUESTION mark is representing a wind box. This box is LOCATED a little outside the side blown CONVERTER towards the left. From this box, AIR BLASTS are passed.

Correct choice is (b) 1 rpm

Best explanation: 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.

The CORRECT answer is (a) Pig iron

To explain I would say: 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.

The correct ANSWER is (b) 30%

EXPLANATION: The minimum efficiency of a cupola is 30%, and that, the maximum efficiency is 50%. Hence, the efficiency RANGES from 30 to 50% only.

The correct choice is (a) 314.38 kg/m^3

Easy explanation: Here, d = 45cm = 0.45m, W = 325kg, height of GROOVE, h = 6.5m. THEREFORE, according to the FORMULA, W = π/4 x d^2 x h x w, => w= 325 / (π/4 x 0.45^2 x 325 x 6.5) => w = 314.38 kg/m^3.

Right option is (d) COPPER

The explanation: 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.

Right answer is (a) True

For EXPLANATION I would say: 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.

The CORRECT choice is (C) Mercury

Explanation: 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.

The CORRECT option is (c) PEAT

For explanation I would say: Only GASEOUS fuels are used for the burning process in an open hearth FURNACE. Peat is a very basic FORM of coal and cannot be used as a fuel here.

Right answer is (a) SILICA

Best EXPLANATION: 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.

The CORRECT ANSWER is (b) 100 tons

To ELABORATE: NONE.

Right ANSWER is (C) Pig iron

The best I can EXPLAIN: The materials such as high carbon CONTENT or other impurities which are present INSIDE the pig iron are burnt in order to obtain steel.

The CORRECT option is (d) Graphite

To elaborate: 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.

Right option is (a) True

Easiest 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.

Right choice is (d) Cupola diameter

Easy explanation: 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.

Correct OPTION is (B) False

Easy explanation: 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.