An unbonded flexible tubular structure for oil exploitation comprising: - a polymeric internal barrier layer; - at least one metallic reinforcing layer (30; 34, 36) located outside the polymeric internal barrier layer, said metallic reinforcing layer (30; 34, 36) comprising a pressure vault comprising at least one pressure vault steel wire which is helically wound with a short pitch around the barrier layer and a pair of tensile armor layers (34, 36) both comprising a plurality of armor steel wires (35, 37) wound with a long pitch, comprising an internal armor layer applied on the pressure vault and an external armor layer applied on the internal armor layer, said metallic reinforcing layer (30; 34, 36) comprising at least one elongated steel element having a non-round cross-section and having as steel composition: - a carbon content ranging from 0.20 weight percent to 1.00 weight percent, a silicon content ranging from 0.05 weight percent to 2.0 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, - a chromium content ranging from 0.0 weight percent to 1.0 weight percent, a sulfur and phosphor content being individually limited to 0.025 weight percent, - contents of nickel, vanadium, aluminium all being individually limited to 0.5 weight percent, - the remainder being iron; said steel having martensitic structure that comprises martensitic grains, wherein a fraction of at least 20 volume percent of martensitic grains is oriented; oriented means that the lenticular grains are either crystallographically oriented and/or microstructurally oriented, wherein the crystallographic axis or the axis of lenticular grains are oriented at the same direction within a tolerance of 20° as measured by X-Ray Diffraction analysis or Electron Backscatter Diffraction or by image analysis such as scanning electron microscope. - a polymeric internal barrier layer; - at least one metallic reinforcing layer (30; 34, 36) located outside the polymeric internal barrier layer, said metallic reinforcing layer (30; 34, 36) comprising a pressure vault comprising at least one pressure vault steel wire which is helically wound with a short pitch around the barrier layer and a pair of tensile armor layers (34, 36) both comprising a plurality of armor steel wires (35, 37) wound with a long pitch, comprising an internal armor layer applied on the pressure vault and an external armor layer applied on the internal armor layer, said metallic reinforcing layer (30; 34, 36) comprising at least one elongated steel element having a non-round cross-section and having as steel composition: - a carbon content ranging from 0.20 weight percent to 1.00 weight percent, a silicon content ranging from 0.05 weight percent to 2.0 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, - a chromium content ranging from 0.0 weight percent to 1.0 weight percent, a sulfur and phosphor content being individually limited to 0.025 weight percent, - contents of nickel, vanadium, aluminium all being individually limited to 0.5 weight percent, - the remainder being iron; said steel having martensitic structure that comprises martensitic grains, wherein a fraction of at least 20 volume percent of martensitic grains is oriented; oriented means that the lenticular grains are either crystallographically oriented and/or microstructurally oriented, wherein the crystallographic axis or the axis of lenticular grains are oriented at the same direction within a tolerance of 20° as measured by X-Ray Diffraction analysis or Electron Backscatter Diffraction or by image analysis such as scanning electron microscope. - a carbon content ranging from 0.20 weight percent to 1.00 weight percent, a silicon content ranging from 0.05 weight percent to 2.0 weight percent, a manganese content ranging from 0.40 weight percent to 1.0 weight percent, - a chromium content ranging from 0.0 weight percent to 1.0 weight percent, a sulfur and phosphor content being individually limited to 0.025 weight percent, - contents of nickel, vanadium, aluminium all being individually limited to 0.5 weight percent, - the remainder being iron;