Write short note on – Alloy steels. Or What are alloy steels ? Why is alloying done ?

Write short note on – Alloy steels. Or What are alloy steels ? Why is alloying done ?

Ans. An alloy steel may be defined as steel to which elements other than

carbon are added in sufficient amount to produce improvements in steel.

Commonly used alloy elements are nickel. chromium, manganese, silicon,

molybdenum, vanadium, phosphorus, tungsten, titanium, copper, zirconium,

cobalt and aluminium. These elements may be used separately or in combination

according to the desired characteristics in the steel. Each of these elements

confer certain qualities upon the steel to which it is added.

Purpose of Alloying– Alloying is done for specific purposes which are

as follows – ·

(i) To increase wear resistance and corrosion resistance.

(ii) To improve hardness, toughness and tensile strength

(iii) To improve machinability.

(iv) To improve low or high temperature stability.

(v) To improve case hardening properties.

(vi) To improve cutting ability.

Advantages of Alloy Steel

(i) Greater ductility at high strength.

(ii) Greater high temperature strength.

(iii) Greater hardenability.

(iv) Less grain growth.

(v) Less distortion and cracking.

(vi) higher elastic  ratio and endurance strength.

Disadvantages of Alloy Steel

(i) High cost.

(ii) Requires special handling.

(iii) Temper brittleness in certain grades.

(iv) Tendency toward austenite retention.

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