Plates & Sheets

Plate, sheet and the line between them

The distinction is thickness, and the practical consequence is the production route. Sheet is thinner, cold rolled, and comes with a controlled surface finish — 2B, No. 4 or mirror. Plate is thicker, usually hot rolled, annealed and pickled, and arrives with a matt No. 1 finish. If your drawing calls for a finish, it also implicitly constrains the thickness and the available sizes.

Finishes, and why they matter beyond appearance

• No. 1 — hot rolled, annealed, pickled. Structural and pressure work where appearance is irrelevant.
• 2B — cold rolled, bright annealed, lightly skin passed. The standard process finish and the usual starting point for fabrication.
• No. 4 — brushed, directional. Architectural and food equipment.
• BA — bright annealed, highly reflective without polishing.
• Mirror — mechanically polished to a reflective finish. Used decoratively, but also where a very low surface roughness reduces adhesion and makes cleaning easier.

Surface finish is a corrosion variable, not only an aesthetic one. A smoother surface gives contaminants fewer places to sit and initiate pitting, which is why hygienic and high-chloride applications specify finish as tightly as they specify grade.

Structural and pressure grades

SA 516 Gr 60 and Gr 70 are the standard boiler quality plates for pressure vessels, normalised and impact tested where the design temperature requires it. S355J2+N is the workhorse structural grade with guaranteed impact properties at −20 °C. S690QL is quenched and tempered to roughly double that yield strength, which lets designers take weight out of a structure — at the cost of much tighter control over welding heat input and preheat.

In India, IS 2062 governs general structural steel, in grades E250, E350 and E510. Where a drawing quotes both an IS grade and a European one, confirm which governs before ordering; they are close but not identical.

Corten or weathering steel is a special case. It is designed to corrode and then stop, forming a stable adherent patina that protects the metal beneath. It needs alternating wet and dry cycles to form that patina properly — permanently damp or sheltered installations do not develop it and will keep rusting.

Duplex, nickel and titanium plate

Duplex plate is supplied solution annealed and quenched, and the ferrite-austenite balance is what gives it both strength and chloride resistance. That balance is destroyed by uncontrolled welding heat input, so duplex fabrication requires a qualified procedure and ferrite checks afterwards. Nickel alloy and titanium plate are supplied against ASTM B series specifications; titanium in particular must be kept away from steel contamination during cutting and handling, since embedded iron particles will initiate corrosion.

Cutting and circles

We supply plate cut to size and as circles and blanks — for vessel heads, flange blanks and cookware. Plasma, laser and waterjet cutting are all available; waterjet is the right answer where the heat-affected zone must be avoided entirely, particularly on titanium and duplex.

What to tell us when you enquire

Grade and standard, thickness, sheet or plate size (or the cut sizes you need), finish, quantity, and certification level. If the plate is going into a pressure vessel, state the design code and whether ultrasonic testing and impact testing are required — both are ordered against the plate, not added later.