scope:

1 Scope

1.1 Coverage. This 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. These steels are intended for fabrication primarily by cold forming and welding as per API Spec 2B. The welding procedure is of fundamental importance and it is presumed that procedures will be suitable for the steels and their intended service. Conversely, the steels should be amenable to fabrication and welding under shipyard and offshore conditions. API Specifications 2W and 2Y cover companion steels providing similar mechanical properties but with improved weldability. This improvement results from a reduction in the maximum allowed chemical composition and is made possible by changes in the method of heat treatment and/or processing.

1.2 The primary use of these steels is in tubular joints, stiffened plate construction, and other intersections where portions of the plates will be subjected to tension in the thickness direction (Z direction). Supplementary Requirement S-4 provides for through-thickness (Z direction) testing of the plates by the material manufacturer and specified limits for acceptance. Supplementary Requirement S-1 provides for ultrasonic examination of the plates by the material manufacturer and specifies limits for acceptance.

1.3 For applications where through-thickness properties are important but Z direction testing has not been specified, Supplementary Requirement S-5 provides a low-sulfur chemistry intended to reduce the size and number of sulfide inclusions in the plate. Supplementary requirement S-5 is neither a substitute for S-4 Through Thickness Testing nor a guarantee of a minimum level of through-thickness ductility. Experience indicates, however, that tests of low-sulfur carbon-manganese steels usually show at least 20% reduction-of-area. Accordingly, supplementary requirement S-5 is intended as an alternative to supplementary requirement S-4 when testing is not desired. If tested, low-sulfur steel is desired, then both supplementary requirements S-4 and S-5 should be ordered.

1.4 The notch toughness requirements specified in Section 7 or S-12 are suitable for application below water or above water in areas of temperate climate (14°F minimum service temperature). Cold-formed materials have less toughness due to straining than that of the original flat plate, especially in those areas aged by the attachment welding of stubs or braces. The requirements for plates in Section 7 include a moderate adjustment for losses in toughness due to straining and aging; however, differences in composition or fabrication practices may result in significantly greater degradation than that included. Supplementary Requirements S-7 and S-8 deal with the strain-aging problem, and consideration should be given to invoking S-7 and/or S-8 when the strain exceeds 5% or when (Nitrogen × % strain) exceeds 0.040. Supplementary Requirement S-8 provides for testing at the specific temperatures and strain levels of interest and is recommended for all material purchases which exceed the purchaser's experience base.

1.4.1 For applications with lower service temperatures, lower test temperatures should be considered. Supplementary Requirement S-2 provides for impact tests at temperatures other than those specified in Section 6 or S-12. S2.1 provides for Drop Weight or Charpy V-notch testing at −60°C. S2.2 provides for such testing at temperatures less than −40°C but other than −60°C.

1.5 Manufacturers desiring to apply the API Monogram to products covered by this specification shall demonstrate to the satisfaction of the American Petroleum Institute a program of education, training, experience, and/or examination assuring the manufacturer's personnel are competent in chemical analysis, inspection testing, and nondestructive examinations required or referenced by this specification.