A387 Grade 11 Class 2 is a chromium‑molybdenum alloy steel plate engineered for pressure vessels and thermal processing equipment operating under elevated temperatures and hydrogen‑rich environments. Compared with Class 1, the Class 2 variant provides higher tensile strength and improved resistance to long‑term thermal degradation, making it suitable for more demanding refinery, petrochemical, and boiler applications. Its alloy balance ensures stable creep resistance, oxidation tolerance, and reliable weldability, supporting fabrication of thick‑section components and welded assemblies exposed to continuous heat and pressure cycles.

Chemical Composition

The steel contains 1.00–1.50% chromium and 0.40–0.65% molybdenum, forming the core of its high‑temperature strength and oxidation resistance. Carbon is controlled at a moderate level to maintain toughness while supporting hardenability. Silicon and manganese contribute to deoxidation and structural stability, and impurities such as phosphorus and sulfur are kept at very low limits to ensure clean steel quality and consistent weld performance.

Mechanical Properties

A387 Grade 11 Class 2 provides a higher tensile strength range of 450–585 MPa compared with Class 1, while maintaining a minimum yield strength around 275 MPa depending on plate thickness. The grade retains excellent creep resistance and toughness during prolonged exposure to elevated temperatures, making it suitable for pressure‑bearing components in refinery heaters, hydrogen reactors, and boiler systems.

Available Size Range

This grade is supplied as hot‑rolled pressure‑vessel plates in thicknesses from 6 mm to 150 mm, widths up to 4200 mm, and lengths up to 18 meters, supporting fabrication of large shells, heads, and welded structures used in high‑temperature industrial environments.

Applications

• Hydrogen‑service pressure vessels

• Refinery reactors and thermal processing units

• High‑temperature boiler components

• Petrochemical heaters and steam‑drum systems