1. (a) Outline the principles and essential differences between Continuous Cooling Transformation and Isothermal Transformation Diagrams Â Â (b)...

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Mechanical Engineering

1. (a) Outline the principles and essential differences betweenContinuous Cooling Transformation and Isothermal TransformationDiagrams
Â Â (b) Using the TTT diagram for a plain carbon steelwith 0.53%wt C, define the nature of the final microstructure (interms of micro-constituents present and approximate percentages) ofsmall samples (5 x 5 x 5 mm) subjected to the followingtime-temperature heat treatments.In each case, assume that thespecimen was austenitised at 860?C and held at this temperaturelong enough to achieve a homogeneous austenitic structure prior tocooling.
(i) Rapidly cool to 500^oC, hold for 7s, rapidly coolto 400oC, hold for 103s and water quench to room temperature.
(ii) Rapidly cool to 400^oC, hold for 7s and waterquench to room temperature.
(iii) Rapid cooling to room temperature within 1s.
(iv) Rapidly cool to 650^oC, hold for 1h and waterquench to room temperature.
(v) Rapidly cool to 400^oC, hold for 1s, followed bywater quenching to room temperature.

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4.4 Ratings (803 Votes)

In isothermal transformation austenite is rapidly brought to some specific temperature and to be maintained at elevated temperature from above eutectoid temperature But continuous cooling is more practical to apply Most steels are heat treated with See Answer

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