A flat wire or a narrow strip has a profiled cross-section and is 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. ...