The effect of thermomagnetic treatment on the amplitude dependence of internal friction of magnetically soft Fe-Cr alloys and graphitized steels is investigated. The laws of variation of parameters of internal friction after thermomagnetic treatment of iron alloys with ferritic structure are determined. The effect of four structural characteristics (size of ferrite grains, graphite inclusions in ferrite matrix, content of impurities in alloys with ferritic structure, and content of vanadium and aluminum in alloys having no α-γ transformation) and of the composition on the variation of the damping properties of iron after thermomagnetic treatment is studied. The changes in the damping properties are analyzed depending on the changes in the crystal and magnetic structures.