API Spec 2H specification for Carbon Manganese Steel Plate for Offshore Structures,API Spec 2H specification covers two grades of intermediate strength steel plates up to 4 in. thick for use in welded construction of offshore structures, in selected critical portions which must resist impact, plastic fatigue loading, and lamellar tearing.API Spec 2H main steel grade:API Spec 2H Grade 2HGr42,Grade 2HGr50 and so on.