  The data of different authors on the thermal conductivity of wustite Fe1-xO,
magnetite F3O4, hematite Fe2O3 and pure iron are systematized. The generalized
values are described by piecewise smooth functions containing as varying
parameters the temperatures of magnetiv and polymorphic (for iron)
transformations as well as the thermodynamic stability boundary (for wustite).
At polymorphic transformation a finite break of the thermal conductivity
function is envisaged, at othet critical points only a break of its temperature
derivative is acceptable. The proposed formulas are presented in two forms: the
general form that allow varying the values of critical temperatures and the
particular form corresponding to their basic values: the boundary of
thermodynamic stability of wustite - 570 C, the Curie points of magnetite - 575
C, hematite - 677 C, iron - 770 C and polymorphic transformation temperature of
iron - 912 C. To calculate the thermal conductivity of oxide scale as a whole,
it is proposed to take into account separately metallic iron and composite
matrix of iron oxides. Model computations using the proposed formulas shows
that the true thermal conductivity of oxide scale (without pores), depending on
the temperature may be from 3 to 6 W / (m K) in the absence of metallic iron
and up to 15 W / (m K) if free iron is released in the eutectoid decay of
wustite. The effective thermal conductivity of oxide scale, taking into account
its real porosity, may be lower by 15-35%. The obtained dependencies are
recommended for use in mathematical simulation of production and processing of
steel products in the presence of oxide scale on their surface.
