Answer:
(a) 2.5 and 6 seconds
(b) 265 HB (27 HRC)
Explanation:
(a) A horizontal line at 550°C intersects the 50% and reaction completion curves at about 2.5 and 6 seconds, respectively; these are the times it will take for the austenite-to-pearlite reaction to go to 50% completion
(b) The pearlite formed will be fine pearlite. From Figure 10.30a, the hardness of an alloy of composition 0.76 wt% C that consists of fine pearlite is about 265 HB (27 HRC).
