Question

Lower critical of steel is

• A. 950°C
• B. 1560°C
• C. 800°C
• D. 723°C

Answer 1

Answer:

D. 723°C

3. The lower critical temperature of all steels is 723°C, the temperature of Pearlite to Austenite transformation, below which austenite does not exist. Hypo-eutectoid steels have carbon content from 0-0.83% with primary ferrite and Pearlite. Eutectoid steel with 0.83% carbon entirely consists of pearlite. Hyper-eutectoid steels have carbon content from 0.83-2.06% with primary cementite and pearlite. Upper critical temperature (Point A3) is the temperature below which ferrite starts to form in hypo-eutectoid alloys. Upper critical temperature (Point Acm) is the temperature below which cementite starts to form in hyper-eutectoid alloys.