The proportion of ferrite and cementite forming above the eutectoid point can be calculated from the iron / iron carbide equilibrium phase diagram using the lever rule.
22.
In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K ( 727�C ); other alloys of steel have different eutectoid temperatures.
23.
In plain-carbon steel, austenite exists above the critical eutectoid temperature of 1000 K ( 727�C ); other alloys of steel have different eutectoid temperatures.
24.
In steel alloyed with metals such as nickel and manganese, the eutectoid temperature becomes much lower, but the kinetic barriers to phase transformation remain the same.
25.
The rate at which the steel is cooled through the eutectoid temperature ( about 727�C ) affects the rate at which carbon diffuses out of austenite and forms cementite.
26.
The 3 versions ( lower carbon, at the eutectoid point ) are not necessarily softer, but often tougher, easier to sharpen, and easier to make.
27.
The eutectoid composition of austenite is approximately 0.76 % carbon; steel with less carbon content ( hypereutectoid steels ) will form cementite before reaching the eutectoid point.
28.
The eutectoid composition of austenite is approximately 0.76 % carbon; steel with less carbon content ( hypereutectoid steels ) will form cementite before reaching the eutectoid point.
29.
For instance, in the iron-carbon system, the austenite phase can undergo a eutectoid transformation to produce ferrite and cementite, often in lamellar structures such as pearlite and bainite.
30.
In metallurgy, quenching is most commonly used to harden steel by introducing martensite, in which case the steel must be rapidly cooled through its eutectoid point, the temperature at which austenite becomes unstable.
