[en] Metallic shielding structures are often adopted to mitigate the magnetic fields generated by high-power high-voltage underground power lines. Their design calls for the assessment of the combined influence of their geometrical parameters and the properties of the employed materials. In this paper, we present the study of pure iron shielding of a three-phase power line and the related efficiency. A finite element-boundary element (FE-BE) method is applied to describe the electromagnetic behavior of the cable-enwrapping shield. This is modeled as an indefinitely long cylinder of hexagonal cross-section, obtained by longitudinal juxtaposition of two doubly bent laminations, their thickness ranging between 1 and 10 mm. The magnetic properties of the involved pure iron laminations have been experimentally obtained under three different conditions: as-received, after localized plastic deformation, after stress-relief annealing. A low-carbon steel lamination has also been considered, whose harder magnetic behavior is predicted to lead to inferior shielding properties. The strong increase of iron permeability obtained upon annealing is conducive to improved shielding effectiveness in thin lamination screens, the advantage of the related magnetic softening becoming irrelevant for sheet thickness larger than about 4 mm. Tests performed on a 42 m long archetype three-phase line, endowed with a 4 mm thick annealed pure iron shield, provide figures for the shielding effectiveness that are in close agreement with the FE-BE modeling prediction