Hot Rolled Cold Rolled Steel
HRS vs. CRS
- HRS
–AKA hot finishing – ingots or continuous cast shapes rolled in the “HOT” condition to a smaller shape.
–Since hot, grains recrystallize without material getting harder!
–Dislocations are annihilated (recall dislocations impede slip motion).
- HRS Characterized by:
–Extremely ductile (i.e. % elongation 20 to 30%)
–Moderate strength (Su approx. 60 – 75 ksi for 1020)
–Rough surface finish – black scale left on surface.
- CRS
–AKA cold finishing – coil of HRS rolled through a series of rolling mills AT ROOM TEMPERATURE.
–Since rolled at room temperature, get crystal defects called dislocations which impede motion via slip!
–AKA work hardening
–Limit to how much you can work harden before too brittle.
–How reverse? Can recrystallize by annealing.
- CRS Characterized by:
–Less ductile – almost brittle (i.e. % elongation 5 to 10%)
–High strength (Su approx. 120 ksi for 1020)
