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The correct answer is (B) False

For explanation I would say: The flux is mixed with casting while solidification that basically reacts with a network of OXIDES and converts them into a powder that floats on the casting so it BECOMES easier to separate out that part. The whole reaction takes place is EXOTHERMIC. The flux is normally used after the CLEANING process which prevents progressive oxidation.

Right answer is (d) 10-30 %

Best explanation: Stainless steels mainly CONTAIN 10-30 % of chromium besides other elements such as carbon, manganese, silicon, sulphur etc. Chromium PRODUCES corrosion resistance property in steel, that’s why the material is known as stainless steel as no any kind of stains are OCCUR on the surface of the steel.

Right option is (b) False

Easiest explanation: In GRAIN refinement process, there is another process CALLED carbon INOCULATION, in which, tablets of ORGANIC compounds are used, namely hexachlorobenzene and HEXACHLOROETHANE.

Correct answer is (a) True

Explanation: MANY alloys CONSIST of lead to increase machinability with easy chip formation. But, COPPER components itself have excellent machinability. And copper alloy CASTINGS are recyclable too, the scrapes of copper alloys castings can be melted and can be used again in the manufacturing of other copper PARTS.

The correct option is (a) True

To explain I would say: If the flux has high vapour pressure then it will not be EASY to control it as vapourization will takes place which will have no any affect on the casting material. So it is ALWAYS SUGGESTED to have low vapour pressure of fluxes that will easily mix with the material and will give EXCELLENT results in order to PREVENT oxidation.

The correct option is (c) Sodium chloride

To elaborate: Sodium chloride is commonly used as flux in the casting PROCESS to prevent oxidation. Sometimes potassium fluoride is also preferred as a flux due to its EXCELLENT VOLATILITY. It not only prevents the oxidation, the other inclusions are also REDUCED by using flux. This process avoids METAL wastage and avoids several defects formation.

The correct option is (b) False

Best explanation: After degassing process, the hydrogen does not stop COMING in the casting material. This can only be controlled by using fluxes in the casting material but it is always RECOMMENDED to determine the gas quantity before casting process, a DEVICE called reduced pressure gas DETERMINATION equipment is then used for DETERMINING the gas content.

The correct option is (B) False

The best I can EXPLAIN: Different types of coatings are applied to magnesium ALLOYS to INCREASE corrosion resistance. Coatings for magnesium alloys are applied by using hexavalent chromium material which provides excellent protection, but do not CONSIDERED as eco-friendly. To avoid environmental problems, Teflon resin is basically applied instead of any other coatings.

The correct option is (a) True

For EXPLANATION: Magnesium is very light metal in comparison with other structural metals. Magnesium is commonly USED in a wide range of markets and applications, from automobiles to aircraft applications. In most of the cases of manufacturing, WEIGHT reducing is the PRIMARY objective for magnesium alloys.

The correct choice is (d) High thermal resistivity

Easiest explanation: Magnesium on getting MIXED with other elements STARTS possessing many DIFFERENT properties. It contains good damping capacity, good ELECTRICAL conductivity and good FATIGUE strength, but not, thermal resistivity.

The correct option is (c) Journal bearings

Easy explanation: In the manufacturing of journal and other TYPES of SOLID bearings, copper alloys are mostly PREFERRED. Many other components LIKE worm WHEELS, gear selector forks and electricity wires are also made by using copper alloys; it is mostly preferred where low friction and high wear resistance is required.

Right CHOICE is (b) False

Easy explanation: For properties of copper to be used, but with more STRENGTH, this copper needs to be mixed with certain material, which will provide it the required strength. Cadmium, silver and aluminium oxide are few of those MATERIALS which will aid in increasing its strength. This PROCESS of increasing strength is done by TREATING the alloy through cold working.

Right choice is (a) True

To EXPLAIN: Titanium ALLOYS have melting point greater than that of steels, but maximum TEMPERATURES for various applications normally RANGE from 428 °C to approximately 540 °C. It mainly depends upon the composition and its characteristics. Titanium aluminide alloy can achieve temperature up to 760 °C for some applications.

Right option is (a) True

For explanation: Teflon RESIN is a low cost coating which is PRIMARILY used for MAGNESIUM alloys to improve CORROSION resistant properties. It is a chromium free corrosion resistant coating that can be also used for IMPROVING lubricity and frictional resistance. It also includes non-wetting features which keeps the casting moisture free.

Right answer is (b) False

Easiest EXPLANATION: Copper alloys COMPONENTS are GENERALLY of non-sparking nature, that’s why they are preferred in manufacturing of electrical EQUIPMENT and components where there is a CHANCE of fire hazard. And the ductile nature of copper alloys is totally independent to its non-sparking nature.

Correct choice is (d) 660⁰C

The explanation: The melting POINT for flux to be used for aluminium casting should be approximately 660⁰C. However, the oxidation in aluminum is inevitable but flux is essential to AVOID contact of aluminium melt to atmosphere and to get DRY dross after skimming process which generally maintains the quality of casting MATERIAL.

Right OPTION is (c) 100 lb

To elaborate: It is mainly OBSERVED that magnesium ALLOYS are MANUFACTURED with the help of sand molds only. The amount of silica sand used in magnesium alloys is 100 lbs in both the British mix and the American mix.

The correct answer is (a) 11%

Best EXPLANATION: Magnesium alloys are BASICALLY a COMPOSITION of various metals mixed with magnesium to IMPROVE its physical, chemical, mechanical and thermal properties. In this, the maximum allowable aluminum that can be ADDED is only 11%.

The correct CHOICE is (B) False

The best explanation: Magnesium is MAINLY distinguished by its low density, which is nearly about 25% of steel and about 60% of the aluminium metal. This property makes magnesium to USE for very lightweight construction. In expensive cars, it is highly used in the construction of crankcase and in other parts to increase power to weight ratio.

Correct OPTION is (b) False

Easiest explanation: Magnesium alloys possess many desirable mechanical, physical and thermal properties, which may help in better CASTING PROCESSES. One of these properties is a high strength to WEIGHT ratio.

Right answer is (a) True

The best I can explain: Titanium metal has a high melting point and low thermal conductivity which is responsible for producing a STEEP thermal gradient in the casting during solidification. The reaction with mould materials forms surface LAYERS which include oxygen and other elements taken from the mould. This affects the mechanical PROPERTIES of the castings. So to avoid such problems, graphite or INVESTMENTS moulds are used instead of simple moulds.

Correct answer is (d) Potassium borofluoride

To explain I would SAY: Moulding materials are effectively inhibited by adding 1 to 2 percent of potassium borofluoride. And controlling of INHIBITOR content in moulding materials is very important because they can affect setting times. Sometimes elimination of SILICA content from moulding materials also takes place to avoid chemical reactions.

The correct option is (b) False

Best explanation: The grain SIZE is highly affected by adding zirconium in magnesium metal. Addition of less than 0.6% zirconium in magnesium is SUFFICIENT to obtain grain size less than 80 microns in casted components. This further increases hardness in the material due to FORMATION of fine grains and ductility ALSO decreases simultaneously.

The CORRECT answer is (b) False

The BEST I can explain: Silicon carbide is a good refractory MATERIAL, but cannot be used in mould making process because it is highly reactive with oxygen and GETS burns itself during oxidation. To avoid such oxidation problems, zirconia is preferred which can also bear very high TEMPERATURES and perfectly acts as a refractory material.

Correct answer is (b) False

Easiest explanation: REFRACTORY materials are materials that have high melting POINTS and they basically act as a heat resisting barrier between high and LOW temperature zones. Refractory materials are useful in constructing structures LIKE boilers, furnaces etc. as they minimize heat LOSSES through the structure during working conditions.

Right option is (d) Yellow

The explanation: It is one of the most unusual properties of copper ALLOYS, that on addition of DIFFERENT MATERIALS in them, there is a change observed in its appearance, that is, the colour of the mixture starts changing. On addition of ZINC METAL in copper, the colour of the mixture changes to yellow.

The correct choice is (c) 8.93 g/cc

Best EXPLANATION: A steel is a mixture of IRON and CARBON and copper alloys are mixtures of mainly copper and a few other materials like zinc and nickel with it. The MAIN copper alloys can be brass and bronze. The DENSITY of copper alloys in general is found to be 8.93 g/cc.

Correct answer is (a) MACRO shrinkage

The best explanation: Aluminium alloys are SUSCEPTIBLE to DROSSING, micro shrinkages and solidification shrinkages, but not to macro shrinkages. For the PREVENTION of entering of dross in MOLD cavity, gating system is installed.

Right choice is (b) False

For EXPLANATION I would say: A runner has to be located in the drag. The area of the runner should be SMALL and IDEALLY equal to the ingate area. It should be streamlined to avoid turbulence.

Right choice is (b) 7.87 g/cc

Explanation: A steel is BASICALLY a mixture of iron and CARBON. The composition of iron varies according to the alloy, high alloy STEELS contain more amounts of carbon and low alloy steels contain less AMOUNT of carbon. The density of steels in general is FOUND to be 7.87 g/cc.

The correct option is (c) Manganese

Explanation: There are CERTAIN metals which are added very LATE in the molten cast. By doing this, aluminium alloys get refined. A few of those metals are, boron, titanium, SODIUM, CHROMIUM and columbium. Manganese is added in aluminium during the operation, not late.

Correct option is (d) OXYGEN

The best explanation: FLUXING and flushing is an operation which is done for the removal of hydrogen from the molten metal. In this process, argon GAS, chlorine gas, nitrogen gas and helium gas are USED as fluxes and not oxygen.

Correct option is (d) Engine blocks

For explanation I would say: The FLUIDITY and expandability of MOLTEN grey CAST iron at the time of solidification, due to the FORMATION of graphite flakes, this iron BECOMES ideal for the manufacturing of shrinkage free and intricate castings components like engine blocks. The graphite presence greatly enhances mechanical properties in grey cast iron.

The CORRECT answer is (a) Electric arc furnace

Best explanation: ALUMINIUM alloys can be MELTED or heated directly or indirectly by fuel firing furnace. The HEATING can take place in a pot furnace, induction heating furnace, a crucible furnace or a REVERBERATORY furnace.

The CORRECT choice is (c) Copper

Explanation: With the presence of about 2% to 5% of copper METAL in aluminium alloy aids in the INCREASE in DUCTILITY of the alloy, that is, it becomes easy for the alloy to be STRETCHED into wires.

The correct choice is (b) False

For explanation: When the fracture of grey cast iron OCCURS, the crack path follows the graphite flakes and the fracture SURFACE appears grey in color due to the presence of graphite. The graphite flakes have good damping FEATURES and HIGH machinability because the graphite flakes work as a chip breaker and also lubricates the tools or MACHINES.

Correct option is (a) True

To elaborate: Cast iron is widely USED because of its high ratio of PERFORMANCE to the cost that they offer. This high VALUE of ratio is also achieved by easy controlling of microstructure and properties in the casting condition, this ENABLES its various APPLICATIONS without giving any heat treatment to the casted parts or components.

Right OPTION is (a) True

Explanation: The composition of cast iron generally varies depending on the GRADE of pig iron used in its manufacturing PROCESS. High silicon CONTENT in cast iron makes it resistance to OXIDATION and corrosion by creating a tight adhering oxide layer to minimize other further attacks. Iron castings are used in applications where this type of resistance gives relatively good service.

Right choice is (b) False

To explain I would say: Cast iron mostly contains 2 to 5% carbon, 1 to 3% silicon and approx 1% manganese. The presence of such contents makes their weld-ability POOR. Cast irons are RELATIVELY cheap and can be easily casted into any complex shapes and MACHINED, but most of the grades of cast iron are not weld-able.

Correct choice is (b) Grey cast iron

Easy explanation: Grey cast iron generally includes thin and little black flakes of graphite. These black flakes cause cast iron to appear in grey COLOR, so it is called as grey cast iron. Presence of graphite can MAKE it USE as a lubricant in some manufacturing processes. But it has less TENSILE strength and toughness than the other cast IRONS.

Correct answer is (d) 2.0-5.0

To explain I would say: Cast iron is the OLDEST ferrous material that is used for commercial purposes. It is mainly a MIXTURE of iron (Fe) and carbon (C). It can also include MATERIALS like sulfur (S), SILICON (Si), and manganese (Mn). Generally, for the cast iron, the percentage of carbon in iron is 2 to 5 PERCENT.