'Sorbite' is obtained when:

'Sorbite' is obtained when: Correct Answer Quenching steel during transformation

Explanation:

The structure (phase) to which austenite will decompose will depend upon the rate of cooling:

• If austenite is slowly cooled (furnace cooling), it will decompose to form the mechanical mixture of ferrite and cementite called pearlite
• An increased rate of cooling (air cooling) of steel, leads to the formation of finely dispersed pearlite, known as sorbite (at about 600°C)
• It the steel us cooled at a faster rate, an even finer structure of austenite decomposition is obtained (at 500°C - 550°C) which is called troosite
• If the temperature is lowered from 550°C to 220°C, acicular (needle-like) troosite is formed, which is known as bainite
• Steel can be cooled at a rate so high that the austenite does not have enough time to decompose into sorbate or toorsite; It will be transformed into martensite
• B.H.N of pearlite is 180, of sorbite 350 and of troosite 450