Consider 2.5 kilograms of an ASTM 1040 plain carbon steel originally held at 870°C in an inert
atmosphere until the metal reached equilibrium. Answer the following. You must show your work
for full or partial credit.
9-1
9-2.
What phase(s) are present and what is the composition of the phase(s) at 870°C?
What are the final microconstituents and approximate masses of those microconstituents
when the following time-temperature treatments are applied to unique 2.5 kg specimens:
Specimen a. Rapidly cool to 400°C, hold for 11 seconds, then quench to room temperature.
9-3.
Specimen b. Rapidly cool to 600°C, hold for 5 seconds, rapidly cool to 300°C, hold for 120
seconds, then quench to room temperature.
Specimen c. Rapidly cool to 300°C, hold for 10 seconds, then cool to room temperature.
Specimen d. Rapidly cool to 625°C, hold for 2 seconds, rapidly cool to 400°C, hold for 85
seconds, quench to room temperature, then reheat the specimen to 675°C, hold for
10º seconds, then cool to room temperature.
Specimen e. Rapidly cool to 670°C, hold for 120 seconds, rapidly cool to 450°C, hold for 40
seconds, then quench to room temperature.
Rank the specimens (a, b, c, d, and e) in terms of their relative hardness.
Specimen letter designation
Hardest
Softest
