Abstract: The invention relates to a flat wire or a narrow strip having a profiled cross-section, composed of a high-strength steel having the following composition (in weight-%): C 0.2-0.9%, Mn 12-25%, Si up to 0.5%, Al 0.5-2.0%, Cr 1.8-3.5%, S max. 0.005%, P max. 0.06%, N max. 0.1%, Mo max. 1.5%, B max. 0.01%, Ni max. 2.0%, Cu max. 2.0%, Ca max. 0.015%, Nb 0.02-0.35% and/or V 0.02-0.35%, as well as optionally Ti 0.01-0.35%, and, as the remainder, iron and unavoidable, production-related contaminants, cold-rolled and/or cold-profiled from wire-form precursor material, with optional intermediate annealing and/or an optional final annealing treatment, to achieve the following mechanical values: Rp0.2 500-1650 MPa, Rm 750-1800 MPa, A80 3-50%, for the production of armoring plies in flexible pipes for conveying petroleum and natural gas, as well as for transport of liquefied natural gas (FLNG) under acid gas conditions (acidic attack media).