Steel alloys in sheet or plate form, having any of the following characteristics: (a) Steel alloys ‘capable of’ ultimate tensile strength of 1 200 MPa or more, at 293 K (20 °C); or (b) Nitrogen-stabilised duplex stainless steel. Note : the phrase alloys ‘capable of’ encompasses alloys before or after heat treatment. Technical note : ‘nitrogen-stabilised duplex stainless steel’ has a two-phase microstructure consisting of grains of ferritic and austenitic steel with the addition of nitrogen to stabilise the microstructure.