Q. Heat hardening is the process done at_______________?
a. Heating 750Â°C and slowly cooling to zero degree
b. Heating quickly upto 450Â°C followed by sudden quenching
c. Heating upto 250Â°C for 15 to 30 min
d. Heating at 750Â°C and then quenching to room temperature
No explanation is available for this question!