Multiple choice question for engineering
1. Which type of refractory brick does the following illustration represent?
b) End Skew
Answer: c [Reason:] Refractory bricks are formed after processes such as mining, calcining, crushing, and grinding. This is then mixed with other materials and the desired brick is formed. The above picture illustrates a jamb brick, whereas a soap brick appears as a long cuboidal box.
2. How much silica do silica refractories usually contain?
a) 95 – 97%
b) 0.2 – 1.0%
c) 1.8 – 3.5%
d) 0.3 – 0.9%
Answer: a [Reason:] Silica is a common type of acid refractory material containing high amounts of silica and low amount of alumina. It contains about 95 – 97% of SiO2, 0.2 – 1.0% of Al2O3, 1.8 – 3.5% of CaO, and 0.3 – 0.9% of Fe2O3. It has an approximate fusion temperature of 1700oC.
3. Which of the following is a property of fireclay?
a) Rigid under load
b) Poor resistance to spalling
c) Instability in volume
d) Poor resistance to attack by alkalies
Answer: a [Reason:] Fireclay is a common refractory brick which is available as a semi-silica class. It has a good rigidity under load at high temperatures and good resistance to structural spalling. These bricks are also resistant to penetration and attack by alkalies and fumes, and also possess volume stability.
4. How is the corrosion resistance of high alumina when compared against fireclay?
d) No resistance
Answer: a [Reason:] High alumina is available with 50-90% alumina. It has great mechanical strength at higher temperatures and good resistance to spalling. It possesses a greater resistance to corrosion against fireclay bricks.
5. What is the hardness of tungsten at room temperature?
a) 250 VHN
b) 480 VHN
c) 155 VHN
d) 60 VHN
Answer: b [Reason:] Tungsten is a common refractory material which has the highest melting point of 3410oC among metals. It also has a hardness of 480 (VHN) on the Vickers scale. The hardness of molybdenum and tantalum is 250 VHN and 155 VHN respectively.
6. TMZ is an alloy of _______
Answer: c [Reason:] TMZ is a molybdenum base alloy which is frequently used due to its availability and machinability. It consists of 0.5% titanium, 0.08% zirconium, and remaining molybdenum. These alloys are used for die casting, extrusion, and forging dies.
7. Which of the following is not a characteristic of tungsten?
a) Good strength
b) Good electrical conductivity
d) Good insulation
Answer: d [Reason:] Tungsten is a refractory metal having the same density as gold, is heavy, and has the highest melting point among metals. It possesses a good strength under high temperature and also good electrical conductivity. It is generally used in lamps, electron tubes, and other electrical parts.
8. How can ductility of tungsten be improved?
a) Cold working
c) Hot working
Answer: a [Reason:] Due to the nature of tungsten, it has a low ductility and malleability at room temperature. Its ductility can be enhanced by lowering the recrystallization temperature. This can be achieved by cold working, which lowers the temperature from 600oC to 190oC.
9. What is the oxidizing temperature of niobium?
Answer: c [Reason:] Niobium is a common nuclear and aerospace material which is often found and used with tantalum. Oxidization of niobium occurs above 400oC. To prevent this oxidization, a protective coating is applied to the material to keep it from becoming too brittle.
10. Which phase represents the matrix of the alloy?
b) Gamma Prime
c) Gamma Double Prime
Answer: a [Reason:] Gamma is that phase of a nickel-based superalloy which is composed of the matrix. It is a solid solution having an FCC structure. The commonly used nickel-based alloys are chromium, molybdenum, iron etc.
11. Which crystal structure is the Gamma Double Prime phase of nickel-based superalloy composed of?
Answer: c [Reason:] Gamma Double Prime is a phase of nickel-based superalloys which are used to strengthen the alloys at temperatures lower than 650oC. It consists of a body-centered tetragonal (BCT) crystal structure having a composition of Ni3Nb or Ni3V.
12. In which temperature range is Gamma Prime phase of nickel-based superalloys unstable?
Answer: c [Reason:] The Gamma Prime phase of nickel-based superalloys is used to strengthen the alloys at temperatures lower than 650oC. It is an intermetallic phase consisting of an FCC crystal structure. They are unstable between 600-850oC due to which a transformation from FCC structure into HCP occurs.
13. TCP phase of nickel-based superalloys are formed at a temperature of _______
d) > 750oC
Answer: d [Reason:] TCP refers to a Topologically Close-Packed phase in which the phases have close-packed planes. It includes several phases existing in HCP crystal structure. This phase is formed as a result of high temperature over a long period of time.
14. Which of the following is not an effect of adding boron and silicon to superalloys?
a) Improves adhesion
b) Maintains oxide layer
c) Increases spalling
d) Reduces spalling
Answer: c [Reason:] Since superalloys are operated at high temperatures, they are susceptible to degradation of quality. Addition of elements like boron, silicon, and yttrium improves adhesion, reduces spalling, and maintains the protective oxide layer. This is a minor form of degradation which can be corrected by coatings.
15. The thermal coating ‘thermally grown oxide’ is formed by the oxidation of _______
Answer: d [Reason:] Thermal barrier coatings (TBC) are used to improve the life and performance of the component by applying a thin coating. This consists of a bond coat, thermally grown oxide, and another thermal insulation coating. This thermally grown oxide (TGO) is formed due to the oxidation of aluminum contained in a bond coat.
16. Which of the following applications does a tungsten-carbide coating provide?
a) Abrasion resistance
b) Corrosion resistance
c) Loss of coating mass
d) Heat resistance
Answer: c [Reason:] Cobalt-cermet based coatings are generally used due to their effects on temperature and oxidation. Tungsten carbide is one such cobalt-cermet based coating which is resistant to abrasion, corrosion, and heat. Additionally, these coatings have the benefit of nominal loss of coating mass due to the presence of carbides.
1. Flame hardening can only be performed on steels with a minimum of ______ carbon.
Answer: a [Reason:] Flame hardening is a selective hardening process with a combustible gas flame as the source of heat for austenizing. This process can only be performed with steels with a high carbon content of at least 0.4%. This is in order to allow hardening of the surface.
2. How is heating of surface done in flame hardening technique?
a) Oxy-acetylene torch
b) Carburizing flame
d) Direct sunlight
Answer: a [Reason:] Flame hardening is a selective hardening process with a combustible gas flame as the source of heat for austenizing. The surface to be hardened is heated to a temperature above its upper critical temperature. This is done using an oxy-acetylene torch.
3. Flame hardening technique is suitable for____________
a) Plain carbon steels
b) Alloy steels
c) Cast irons
d) Pig iron
Answer: a [Reason:] Flame hardening is a selective hardening process with a combustible gas flame as the source of heat for austenizing. It is more suitable for plain carbon steels having a carbon composition of 0.4-0.95%. It is used to improve wear resistance and surface hardness of gears, wheels, sheaves, shafts, mills, and other components.
4. Which of the following is an application for flame hardening?
a) Distortion occurs
b) Expensive equipment
c) Suitable for larger quantities
d) Overheating causes cracks
Answer: d [Reason:] The advantage of flame hardening lies in the fact that there is no distortion of workpiece since only a small section of the steel is heated. This process is efficient and economical as the cost of equipment is low, thereby making it more suitable for small quantities. It has a disadvantage that overheating of the steel may cause cracks.
5. How does induction hardening differ from flame hardening?
a) Electric current is used
b) Higher quenching time
c) Low-temperature operation
d) Results In fine grain structure
Answer: a [Reason:] The basic mechanism of both induction and flame hardening techniques remains the same. In induction hardening, however, the heat source is derived from the resistance to induced eddy currents.
6. What is the frequency used for depths of 2 to 3 mm in induction hardening?
a) 1200 Hz
b) 3000 Hz
c) 5400 Hz
d) 9600 Hz
Answer: d [Reason:] The depth to which the heating occurs varies inversely as the square root of the frequency in case of induction hardening. This means that as higher frequencies are used, the depths achieved are shallower. The typical frequencies used are 3000 Hz for 3-6 mm depth and 9600 Hz for 2-3 mm depth.
7. Which of the following is true for induction hardening?
a) Requires less time
b) Hardness and depth is difficult to control
c) Only external surfaces can be hardened
d) It gives a scaling effect
Answer: a [Reason:] Induction hardening has a major advantage that it requires a very less time, typically of the order of 10 seconds. It is easy to control the surface hardness and depth, and can be automated. Here, both external and internal surfaces can be hardened. Since it does not give any scaling effect, the machining is reduced.
8. What is the hardness achieved by flame hardening?
a) HRC 30-40
b) HRC 50-60
c) HRC 80-100
d) HRC 120-140
Answer: b [Reason:] Both flame hardening and induction hardening experience similar results. The hardened layer is about 3 mm thick and has a hardness of about HRC 50-60. Distortion can be often minimized in both processes. Additionally, the surface remains clean in induction hardening.
9. ___________ is a method of obtaining diverse properties by varying thermal histories of various regions.
a) Selective Hardening
Answer: a [Reason:] Selective hardening is a technique by which different properties are obtained by varying thermal histories of various regions. This is otherwise considered as the thermal method of surface hardening. Flame hardening and induction hardening are the two methods of selective hardening.
1. The hysteresis loss in soft magnetic materials must be kept ______
Answer: b [Reason:] Soft magnetic materials are used in cases where regular reversal of magnetization path is required. The hysteresis losses in such materials must be kept to a minimum. This is due to a smaller hysteresis area.
2. The supermaloy primarily composed of ________________
Answer: a [Reason:] Permalloy is a magnetic material invented by the scientist Gustav Elmen. It is composed of just about 80% nickel and 5% molybdenum. It has a high relative permeability of 105.
3. Which of the following is an example of a soft magnetic material?
Answer: a [Reason:] Permalloy is a soft magnet mainly used in electrical and electronic applications. It is composed of roughly 45% nickel. It has a high relative permeability of around 2700.
4. What is the relative permeability of iron?
Answer: a [Reason:] Relative permeability is the measure of the effective permeability of a material. Commercial iron has a relative permeability of 250. The values of relative permeability of Fe-Si, permalloy, and supermaloy are 1500, 2700, and 100000 in that order.
5. The heat treatment of alnico alloys at _____ results in phase separation.
Answer: d [Reason:] Some materials are heat treated in a magnetic field to enhance their properties. At just about 800oC, alnico undergoes a phase separation into two phases having different compositions and amount of magnetizations.
6. What is the hysteresis loss of permalloy?
Answer: b [Reason:] Hysteresis loss of soft magnetic materials is generally kept low due to the small area. This value resides at 120 J m-3 for permalloy and even lower at 21 J m-3 for supermaloy.
7. Which of the following is a property of a hard magnetic material?
a) Low hysteresis
b) Low eddy loss
c) Low coercive force
d) High residual induction
Answer: d [Reason:] Hard magnetic materials are used to produce permanent magnets. These permanent magnets have a high residual induction and large coercive force. Low hysteresis and Low eddy loss are properties of soft magnetic materials.
8. A _____ cooling rate solidifies metallic glass made from iron- base alloys.
a) 10oC s-1
b) 100oC s-1
c) 1000oC s-1
d) 10000oC s-1
Answer: d [Reason:] Metallic glasses produced from iron-base alloys are used to provide a reduction in core losses. When such an alloy is cooled at 104oC s-1, it solidifies into a ribbon-shaped metallic glass instead of crystallization.
9. Which of the following is not a use of magnesium-manganese ferrites?
a) Microwave isolator
d) Memory core of computer
Answer: c [Reason:] Magnesium-manganese ferrites having high resistivity are used as microwave insulators and gyrators in the KHz and MHz range. They are also used in memory cores of the computer when there is a higher manganese to magnesium ratio.
10. Yttrium-iron-garnet is used as microwave isolators in the ____ range
Answer: c [Reason:] Garnets such as Y3Fe5O12 (yttrium-iron-garnet)have a narrow resonance line width. These are popularly used as microwave isolators in the GHz range.
11. What is the coercive force of high carbon steel?
Answer: a [Reason:] Coercive force is defined as the ability of a material to withstand a magnetic field. It is denoted by Hc and must be larger for permanent magnets (hard magnetic material). High carbon steel has a coercive force of 3.98 kA m-1.
12. What is the value of residual induction of alnico alloys?
Answer: c [Reason:] Alnico is a common hard magnetic material containing aluminum, nickel, and cobalt (Al-Ni-Co). It has a residual induction (Br) of 0.8 to 1.2 Wb m-2 and a coercive force (Hc) of 60-12 kA m-1.
1. The liquid temperature of the filler metal used in brazing is _________
Answer: b [Reason:] Brazing is defined as the joining of two metal pieces by using a filler metal. The liquid temperature of the filler metal is above 427oC and below the solidus of the base metal.
2. Copper and aluminum can be joined by brazing when _________ alloy is used.
Answer: b [Reason:] Most metals and alloys such as carbon steels, cast iron, stainless and alloy steels, brass, and others can be brazed. Aluminum and copper can also be joined if an aluminum-silicon alloy is used as the brazing filler metal.
3. Which of the following filler metals is used in electrical industry?
Answer: c [Reason:] Silver brazing filler alloys are used for joining most ferrous and non-ferrous metals except aluminum and magnesium. BAG-5 filler metal is composed of 44-46% Ag, 29-31% Cu, 23-27% Zn, and 0.15% of other elements. It is mostly used in the electrical industry.
4. Nickel filler metals are heat resistant up to ________ in short time service.
Answer: c [Reason:] Nickel filler metals are used for their corrosion and heat resistance properties up to 982oC for continuous service and 1204oC for short time service. These are used primarily on AISI 300 and 400 series stainless steels and nickel and cobalt base alloys.
5. Which of the following filler metals is used for carbide tip brazing?
Answer: b [Reason:] BAG-4 filler metal is used for carbide tip brazing and is composed of 39-41% Ag, 29-31% Cu, 26-30% Zn, 1.5-2.5% Ni, and 0.15% of other elements. BAG-1 freely flows into low and narrow capillary joints. BAG-8 filler metal is used in a controlled atmosphere or vacuum brazing, whereas BAG-18 is used for brazing of ferrous and non-ferrous alloys without flux.
6. Tin-zinc solders are used for joining __________
Answer: a [Reason:] Tin-zinc solders contain a varying composition of tin and zinc, each with a solidus temperature of 199. These solders are used for joining aluminum. Aluminum can also be joined using zinc-aluminum solders.
7. What is the solidus temperature of tin-lead solders?
Answer: a [Reason:] Tin-lead solders constitute the largest portion of all solders in use. They possess good corrosion resistance to most media and can be used to join most metals. Except for the 5/95% Sn/Pb solders, all solders of this type have a solidus temperature of 183.
8. Addition of ___________ increases the mechanical properties of a tin-lead solder.
Answer: c [Reason:] Addition of antimony up to 60% of the tin content increases the mechanical properties of the solder. However, this results in a slight impairment of the soldering characteristics. Of the various solders of this type, the composition of Pb is the highest, whereas that of antimony is lowest.
9. Aluminum can be joined to another aluminum with the use of ________ solder.
d) Fusible alloy
Answer: c [Reason:] Cadmium-silver solders are used for joining aluminum to itself or to other metals. It is composed of 95% cadmium and 5% silver. Due to high cadmium content, improper use of this solder may lead to health hazards.
10. __________ solders are used for glass-to-glass and glass-to-metal soldering.
Answer: d [Reason:] A 50% indium and 50% tin solder is used for glass-to-metal and glass-to-glass soldering. Cadmium-zinc and Tin-zinc solders are used for soldering and joining aluminum. Lead-zinc solders are used for soldering of copper and its alloys.
1. Which is the primary element used for making stainless steel alloy?
Answer: a [Reason:] Stainless steels contain iron and a minimum of 10.5% of chromium. This gives it great resistance to corrosion. Therefore, stainless steels are often known as corrosion-resistant steels or chromium-bearing steels.
2. Addition of _______ gives stainless steels an austenitic structure.
Answer: c [Reason:] Nickel is added to stainless steels with a 3.5% to 22% composition to form austenitic structure. This results in the highest corrosion resistance among all stainless steels. They also possess high strength and ductility.
3. Stainless steels with little carbon and no nickel are called ________
a) Ferritic stainless steel
b) Austenitic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Answer: a [Reason:] Ferritic stainless steels are steels containing 12.5% to 17% of chromium. They are nickel¬-free and contain very little carbon making up its composition. They are, therefore, better resistant to corrosion than martensitic stainless steels.
4. Stainless steels with high strength, but low corrosion resistance are known as _______
a) Austenitic stainless steel
b) Ferritic stainless steel
c) Martensitic stainless steel
d) Duplex stainless steel
Answer: c [Reason:] Martensitic stainless steels are made of 12-14% chromium, along with molybdenum, nickel, and carbon. This makes the steels hard and brittle, but poorly resistant to corrosion. Martensitic stainless steels are used in making Swiss army knives.
5. Which of the following are applications of Ferritic stainless steels?
a) Aircraft engine parts, heat exchangers
b) Milk, kettles
c) Oil burner parts, furnace elements
d) Pumps and valve parts
Answer: c [Reason:] Ferritic stainless steels have the ability to be welded, forged, rolled, and machined. They are used for making oil burner parts and furnace elements. Austenitic stainless steel is used to make engine parts, milk cans; Pumps and valve parts are applications of martensitic stainless steels.
6. Which of the following is not a type of oil-hardening steel?
Answer: d [Reason:] Oil hardening steels are a group of cold working tool steels. This group consists of O1 (0.9% C, 1% Mn, 0.5% Cr), O2 type (0.9% C, 1.5% Mn, 0.3% Si), O6 type (1.65% C, 1% Si, 0.25% Mo, and an O7 type.
7. Mushet steel belongs to which group of tool steels?
a) Oil-hardening steels
b) Air-hardening steels
c) High-speed steels
d) Hot-working steels
Answer: b [Reason:] Mushet steel was the first air-hardening tool steel. It belongs to the Cold-working family of tool steels. It was developed by Robert Mushet.
8. What property does the AISI-SAE tool steel grade ‘L’ possess?
c) Plastic mild
d) Special Purpose
Answer: d [Reason:] The steel grade ‘L’ refers to a special purpose steel containing low alloy. It consists of elements such as carbon, chromium, manganese, and a few others. The L2 and L6 are the most commonly used steels under this category.
9. The low-carbon, high-alloyed steels which possess high strength and toughness are known as _______
a) Carbon steels
b) Alloy steels
c) Maraging steels
d) Stainless steels
Answer: c [Reason:] Maraging steels are those high strength steels which have tensile strengths up to 1900 MPa. They are composed of 18% Ni, 7% Co, and less than 0.05% C.
10. What do TRIP steels stand for?
a) Transformation Induced Porosity
b) Transformation Induced Plasticity
c) Transformation Induced Pearlite
d) Transformation Induced Property
Answer: b [Reason:] TRIP steels are those steels containing high strength and ductility. They are mainly used for automotive industry needs. The expanded form of TRIP is Transformation Induced Plasticity. It contains an austenite microstructure.
11. What is the maximum allowable temperature at which High-Speed Steels retain good cutting ability?
Answer: d [Reason:] High-speed steels have the ability to remove and cut metal at a much higher rate than carbon steels. They have a good cutting ability even at a temperature as high as 540oC. Above this temperature, they soften and lose their cutting edge.
12. Ultra high-speed steels are made of which of the following elements?
a) Tungsten and molybdenum
b) Chromium and molybdenum
c) Vanadium and cobalt
d) Molybdenum and cobalt
Answer: c [Reason:] Ultra high-speed steels have greater tool lives and greater cutting efficiency. This is due to the addition of vanadium (up to 4%) and cobalt (5% to 12%) along with carbon, chromium, and tungsten.
13. What is the microstructure of Hadfield’s steel?
Answer: a [Reason:] Hadfield’s manganese steels (Mangalloy) possess great strength and toughness. Its austenite structure is obtained by heating it. This also results in high wear resistance, which finds its applications in bulldozers, crushers, etc.