Patent ID: 7923126

Claim:
A method of producing a flexible pipe comprising at least one unbonded armouring layer, at least one unbonded sealing layer comprising an internal sealing layer and comprising an inner armouring layer (carcass) inside the internal sealing layer, the method comprising: producing the inner armouring layer from a duplex steel wherein the duplex steel comprises in weight percent: 0.01-0.05% by weight of carbon (C); at least 0.15% by weight of nitrogen (N); 20.0-23.0% by weight of chromium (Cr); up to 3.0% by weight of nickel (Ni); up to 1.0% by weight of molybdenum (Mo); 3-6% by weight of manganese (Mn); up to 1.0% by weight of copper (Cu); incidental impurities; and balance being iron (Fe).