For questions [23]-[26], use the following answer (which may be used more than o

Question

For questions [23]-[26], use the following answer (which may be used more than once): options (a) 0.035 wt% C (b) 0.70 wt% C (c) 0.76 wt% C (d) 1.95 wt% C (e) 6.7 wt%. C The composition of austenite that decomposes into termite and cementite when a steel is cooled relatively slowly. A steel specimen with this overall composition will produce a microstructure with no proeutectoid phase, for relatively slow cooling conditions. A with this overall composition will feature mostly pearlite and proeutectoid cementite, where the majority of the steel (by mass) is proeutectoid cementite, if cooled relatively slowly. The overall composition that produces the hardest steel upon slow cooling. For the hypereutectoid steel composition, what microstructure is expected if austenite is preserved to 450 degree C and held for 1 second and then quenched to room temperature? (a) Bainite + Martensite (b) Proeutectoid Ferrite + Pearlite (c) Martensite (d) Bainite (e) Pearlite

Explanation / Answer

Ans 22 option A is false

The steel is cooled slowly so that carbon can be diffused out of austenite forming iron carbide ( cementite) and then precipitate ferrite. When it is cooled at a higher rate, carbon is trapped inside, forming martensite.

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