Questions and Answers Section 4

Questions and Answers

Question :

31.Thermosetting plastics are those materials which 

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are formed into shape under heat and pressure and results in a permanently hard product

Note:-

A thermoset, also called a thermosetting plastic, is a plastic that is irreversibly cured from a soft solid or viscous liquid, prepolymer or resin.

Question :

32.Admirality gun metal contains

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88% copper, 10% tin and 2% zinc.

Note:-

Gunmetal, also called G Metal, variety of bronze, formerly used for ordnance. Modern admiralty gunmetal is composed of 88 percent copper, 10 percent tin, and 2 percent zinc and is used for gears and bearings that are to be subjected to heavy loads and low speeds.

Question :

33.The percentage of phosphorus is phosphor bronze is 

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0.1

Note:-

phosphor bronze is a tough, hard form of bronze containing a small amount of phosphorus, used especially for bearings.

Question :

34.For the pipe fitting like elbow, tee, union etc., which of the following is preferred? 

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Malleable iron.

Note:-

Malleable iron is cast as white iron, the structure being a metastable carbide in a pearlitic matrix. Through an annealing heat treatment, the brittle structure as first cast is transformed into the malleable form.

Question :

35.Chilled cast iron is produced

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by quick cooling of molten cast iron.

Note:-

Chilled cast iron. Iron-carbon alloy with low graphitization factor so that chill occurs forming a graphite-free structure. The carbon is present bonded in the form of iron carbide, which is why the break surface of the material appears whitish instead of gray.

Question :

36.The red flame during the operation of a bessemer converter indicates that the 

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red flame does not occur during the operation of a Bessemer converter.

Note:- Bessemer converter is a steel-making process, now largely superseded, in which carbon, silicon, and other impurities are removed from molten pig iron by oxidation in a blast of air in a special tilting retort (a Bessemer converter ).

Question :

37.Phosphor bronze has

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good wearing qualities and high elasticity .

Note:-

Phosphor bronze is an alloy of copper with 0.5–11% of tin and 0.01–0.35% phosphorus. The tin increases the corrosion resistance and strength of the alloy.  These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain.

Question :

38.In the austempering process of heat treatment, austenite changes into 

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Bainite.

Note:-

Austempering is a heat treating process for medium-to-high carbon ferrous metals which produces a metallurgical structure called bainite. It is used to increase strength, toughness, and reduce distortion.

Question :

39.Which of the following material has maximum malleability? 

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Lead.

Note:-

Lead is a chemical element with symbol Pb and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and has a relatively low melting point.

Melting point: 327.5 °C.

Boiling point: 1,749 °C.

Question :

40.The machine tool guide ways are usually hardened by 

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flame hardening.

Note:-

Heat is applied to the part being hardened, using an oxy- acetylene (or similar gas) flame on the surface of the steel being hardened and heating the surface above the upper critical temperature before quenching the steel in a spray of water. The result is a hard surface layer ranging from 0.050" to 0.250" deep.