COVERAGE This specification covers two grades of high strength steel plates for use in welded construction of offshore structures@ in selected critical portions which must resist impact@ plastic fatigue loading@ and lamellar tearing. Grade 50 is covered in thicknesses up to 6 in. (150 mm) inclusive@ and Grade 60 is covered in thicknesses up to 4 in. (100 mm) inclusive. It is intended that steel produced to Grades 50 of the basic API Spec 2W@ without Supplementary Requirements@ although produced in a different manner and of somewhat different chemical compositions@ be at least equivalent in minimum performance and@ therefore@ in service application@ to the corresponding grades listed in Sections 5 through 7 of API Spec 2H. Higher performance (i.e.@ notch toughness at lower temperatures@ or enhanced weldability) typically available with TMCP steel may be achieved by specification of Supplementary Requirements. API Spec 2W steels are intended for fabrication primarily by cold forming and welding. The welding procedure is of fundamental importance and it is presumed that procedures will be suitable for the steels and their intended service. Because of the characteristic high YS/TS ratio of TMCP steels@ users may want to consider welding consumables which avoid under-matched weld metal. Conversely@ the steels should be amendable to fabrication and welding under shipyard and offshore conditions.