A387 Grade 11 Class 1 is a chromium‑molybdenum alloy steel designed for pressure vessels and thermal processing equipment operating under elevated temperatures and hydrogen‑rich conditions. Its alloy balance provides stable creep resistance, oxidation tolerance, and long‑term strength retention during continuous exposure to heat and pressure. This grade is widely used in refinery reactors, petrochemical heaters, steam drums, and high‑temperature processing units where metallurgical stability and weldability are essential for safe operation.

Chemical Composition

The steel contains approximately 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 silicon and manganese support deoxidation and structural integrity. Phosphorus and sulfur are kept at very low limits to ensure clean steel quality and consistent weld performance.

Mechanical Properties

A387 Grade 11 Class 1 typically provides a minimum yield strength around 275 MPa and a tensile strength range of 415–585 MPa, depending on plate thickness. It maintains reliable creep resistance and toughness under prolonged thermal stress, making it suitable for pressure‑bearing components in refinery 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 assemblies.

Applications

• High‑temperature pressure vessels

• Refinery reactors and hydrogen‑service equipment

• Boiler and steam‑drum components

• Petrochemical heaters and thermal processing units