The influence of silicon in amounts of up to 4.33 wt% was studied in terms of its effect on micro- and macrostructure, on non-metallic inclusions, on mechanical hardening and on magnetic properties of Fe-28Cr-24Co alloy of equiaxial grain structure and of partially ordered structure-the so-called semicolumnar structure. Optimum magnetic properties in the examined alloy are attained with silicon content Si = 1.04 wt%. Magnetic properties of an alloy of semicolumnar structure are markedly superior to those of the alloy devoid of that structure. With up to 1.04 wt% of silicon, the macrostructure of the alloy remains practically unchanged, while with higher contents of silicon a refinement of the structure takes place. The stereometric parameters of non-metallic inclusions (Al2O3, SiO2, Al2O3·SiO2) increase with silicon contents Si > 1.04 wt%. The hardness of the alloy after homogenizing is practically constant up to silicon content Si = 1.65 wt%, but it increases slightly with Si > 1.65 wt%. The examined alloy with silicon up to 1.65 wt% is ductile in the quenched state and could also be cold-worked.