Correct Answer - Option 2 : Molybdenum
Explanation:
Steel is an alloy of iron and carbon, along with small amounts of other alloying elements or residual elements as well. The plain iron-carbon alloys contain 0.002 - 2.1% by weight carbon.
Alloy steels contain 0.1 - 1.0% carbon. Alloying materials like chromium, nickel, molybdenum, vanadium, copper, aluminium, sulphur etc. are added to improve the properties of steel.
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Element
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Effect
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Boron
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Improves hardenability without the loss of machinability
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Chromium
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Increase hardness and lowers ductility.
Improves oxidation and corrosion resistance
Corrosion resistance may also be enhanced by Ni and Mo addition.
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Cobalt and Tungsten
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Improves strength and hardness at elevated temperatures
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Sulphur
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Improves machinability when combined with manganese
Alone increases the brittleness and lowers impact strength and ductility
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Manganese
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Improves hardenability and wear resistance
Counteracts the brittleness caused by Sulphur
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Molybdenum
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Improves hardenability, forms carbides and enhances wear resistances, improves toughness and lowers ductility.
Improves elevated temperature strength, creep resistance
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Nickel
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Increase strength and hardness without sacrificing ductility and toughness. Hence, Option 1 is correct.
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Vanadium
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Increases strength, hardness, wear resistance and resistance to shock impact at high temperature and lowers ductility.
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Titanium
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Improves strength, Deoxidizes steel
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