Alloy Steel Plates
Plates are flat-rolled products, usually 5 mm and thicker (with some specifications starting at about 3 mm), supplied as discrete plates cut from a hot-rolled plate or coil. They're the raw material for pressure vessels, tanks, heat-exchanger tubesheets, structures and wear parts.
Choose a grade below for specifications, composition, sizes and weight charts.
Alloy Steel plates by grade
| Grade | Specification | Key characteristic | Typical use |
|---|---|---|---|
| P5 Plates | ASTM A387 Grade 5 | 4–6% chromium for sulphidation resistance | Refinery heater tubes |
| P9 Plates | ASTM A387 Grade 9 | 8–10% Cr, 1% Mo | Fired heater and furnace tubes |
| P11 Plates | ASTM A387 Grade 11 | 1–1.5% Cr, 0.44–0.65% Mo | Boiler headers, tubes and steam piping |
| P22 Plates | ASTM A387 Grade 22 | 1.9–2.6% Cr, 0.87–1.13% Mo | Main steam and hot-reheat piping |
| P91 Plates | ASTM A387 Grade 91 | Creep-strength-enhanced ferritic (CSEF) steel | Main steam and hot-reheat piping |
How alloy steel plates are made, sized and tested
How it's madeSlabs are hot-rolled on a reversing plate mill (or a Steckel/hot-strip mill for thinner plate), then heat treated (annealed, normalised, or quenched and tempered, depending on material), descaled and pickled or shot-blasted. Plates are cut to size by plasma, oxy-fuel, waterjet or shearing.
- Size range
- Thickness about 3 – 150 mm (and heavier on request), widths 1,000 – 3,000 mm, lengths 2,000 – 12,000 mm; cut-to-size and profile-cut parts
- Finish
- No.1 (hot-rolled, annealed and pickled) for stainless; shot-blasted, mill scale or primed for carbon steel
- Ends
- Mill edge, sheared, plasma or waterjet cut, profile cut to drawing
Testing & documents
- Chemical analysis and tensile tests (per plate or heat)
- Impact tests for low-temperature and pressure-vessel plates
- Ultrasonic testing (e.g. ASTM A435 / A578) when specified
- IGC, HIC and simulated PWHT tests as required
- Flatness and dimensional inspection
- EN 10204 3.1 certificate; 3.2 with third-party inspection
Frequently asked questions
What is the difference between plate and sheet?
Thickness. Sheet is generally below about 5–6 mm and supplied cold-rolled with a finer finish. Plate is thicker and usually hot-rolled.
Can you cut plates to size?
Yes. Plates can be supplied in full mill sizes or cut to size and profile to your drawing.
Which alloy steel grades are available as plates?
P5, P9, P11, P22, P91.
Which specifications cover alloy steel plates?
ASTM A387, depending on grade.
Need alloy steel plates?
Send grade, size, quantity and destination.