American Petroleum Institute

Specification for Steel Plates, Quenched-and-Tempered, for Offshore Structures - Fifth Editon; Effective Date: June 2007
 N SPEC 2Y

Annotation

COVERAGE

This specification covers two grades of high strength steel plate 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 Grade 50 of the basic API Spec 2Y, without Supplementary Requirements, 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 and API Spec 2W.

API Spec 2Y 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 quenched-and-tempered steels, users may want to consider welding consumables which avoid undermatched weld metal. Conversely, the steels should be amenable to fabrication and welding under shipyard and offshore conditions.

POST MANUFACTURING HEATING

Due to the inherent characteristics of quenched-and-tempered material, plates manufactured to this Specification cannot be formed or postweld heat treated at temperatures above the tempering temperature used during manufacture without some risk of sustaining irreversible and significant losses in strength and toughness. If warm-forming is to be required, the tensile and notch toughness properties of the finished component shall be verified and the properties shall conform to the requirements of the specification. The plates may be post-weld heat treated at a temperature higher than that used during manufacture, providing the test coupons are subjected to a thermal cycle to simulate such fabrication operations, as described in Supplementary Requirement S9. Verification or simulation is not necessary for heating at temperatures not exceeding 400°F (205°C).