The heat treatment parameters were chosen in order to produce microstructures ranging from predominantly lamellar to globular cementite
Modeling of Cementite
Formation in Extra and Ultra Low Carbon Steels (J.
Eventually there were accepted that quenching from 800[degrees]C or 860 [degrees]C temperatures enabled the formation of martensite structure and enlarged coagulated particles of alloyed cementite
(up to 15% vol.
Conventional annealing in the furnace resulted in ferritic microstructure with spheroidized cementite
replacing the initial lamellar pearlitic areas.
The purpose is to convert pearlitic carbides, in the absence of free cementite
, to ferrite and graphite by a gradual diffusion process, rather than by transformation.
Scarce traces of preserved cementite
lamellae can be found only below the surface of the specimen where the strain level was lower.
The structure of the base material, is formed from polyhedral ferrite granulate, to the limit of which also appear tertiary cementite
precipitancy, evidenced by the halving of granulate limits (figure 1).
In the absence of enough Mn, S has a marked stabilizing action on the cementite
and promotes carbides (chill).
The microstructure consists of a ferrite matrix with globular cementite
and primary carbide chrome in annealed state (Fig.
In addition, the ferrite effect suppresses cementite
formation and inhibits chills;
The zone of thermal influence essentially depends on a material of a basis and for steel 45 will consist from troostite-martensite and ferritic grids, for steel O8--from martensite, austenite, troostite-pearlite and cementite
In the Fe-C system, carbon (C) may exist as either cementite
Low elongation usually results from high levels of pearlite, floated graphite or cementite
in the microstructure, or low residual Mg content.
To receive stable readings, especially of solidus, the iron is forced to solidify according to the metastable system where C is precipitated as cementite
by adding tellurium to the sample.
No effect of different N levels has been identified with the graphite nodule formation, but a stabilizing effect has been reported (at higher N levels) for the pearlite and cementite
contents of ductile iron.