There are two types of CCT diagrams that plot the start, fraction, and finish of transformation temperatures against transformation time or cooling rate. CCT diagrams measure the extent of transformation as a function of time for continuously decreasing temperature, as materials are usually cooled continuously. The transformations are delayed compared to isothermal curves, shifting them to longer times and lower temperatures. CCT diagrams differ from TTT diagrams in that continuous cooling prevents the formation of bainite, resulting in pearlite formation instead. Properties like hardness and strength depend on the formed constituent, with martensite being the hardest and strongest. Factors that affect the CCT curve include grain size, carbon content, and alloying elements.

1. CONTINUOSLY
COOLING
TRANFORMATION (CCT)

2.  Introduction
 CCT Diagram for Fe – C
 Carbon Contain and Its Effect On Mechanical
Properties
 Factors Affecting CCT Curve
 Reference

3. There are two types of CCT diagrams
 Plot of (for each type of transformation)
transformation start, specific fraction of transformation
and transformation finish temperature against
transformation time on each cooling curve
 Plot of (for each type of transformation)
transformation start, specific fraction of transformation
and transformation finish temperature against cooling
rate or bar diameter for each type of cooling medium

4.  It measure the extent of transformation as a function
of time for a continuously decreasing temperature.
 Usually materials are cooled continuously, thus
Continuous Cooling Transformation diagrams are
appropriate.
 For continuous cooling, the time required for a reaction
to begin and end is delayed, thus the isothermal curves are
shifted to longer times and lower temperatures
 Main difference between TTT and CCT diagrams: no space
for bainite in CCT diagram as continuous cooling always results in
formation of pearlite.

6. Properties of 0.8% C steel
Constituent Hardness
(Rc)
Tensile strength (MN /
m2)
Coarse pearlite 16 710
Fine pearlite 30 990
Bainite 45 1470
Martensite 65 -
Martensite tempered at
250 oC
55 1990

8.  Grain size
 Carbon content
 Alloying elements

12.  www.msm.cam.ac.uk/phase-
trans/2012/Manna/Part3.ppt
 www.dss.nitc.ac.in/.../32%20TTT%20AND%20
CCT%20DIAGRAMS.ppt
 nptel.ac.in/courses/Webcourse-
contents/IISc.../PPTs/MTS_07_m.pdf
 www.csun.edu/~bavarian/Courses/.../Lectur
es.../ch11_Phase_Transf.ppt