Specifications

Chemical composition and mechanical properties

Limits for plate, sheet and strip to ASTM A240. Pipe (A312), tube (A249, A269) and bar (A276, A479) limits are similar.

Values for plate, sheet and strip; check the standard for other product forms and thicknesses.

Equivalent designations are similar but not identical; order to the standard you need.

Where SMO 254 plate is used

Pulp and paper: bleach plant washers, towers and filtrate tanks handle chloride- and chlorine dioxide-bearing liquors at elevated temperature, where 316L pits; SMO 254 plate is a standard choice. Flue-gas desulphurisation: absorber vessels, inlet ducts and outlet ducts see acidic, chloride-rich condensate. Seawater and desalination: plate heat exchangers, evaporator shells, water boxes and seawater tanks. Chemical processing: vessels and heat exchangers for chloride-contaminated acids. Food processing: equipment handling salty brines.

Fabrication

SMO 254 plate forms cold with more force than 316L because of its higher strength. It is welded with over-alloyed nickel-based fillers such as ERNiCrMo-3 or ERNiCrMo-4, using low heat input; matching-composition welds would be less corrosion resistant because molybdenum segregates during solidification. After welding, heat tint is removed and welds pickled and passivated. Plate is cut by plasma or water-jet, and heat-affected edges are ground before welding.

Clad plate

For large vessels and scrubbers, carbon steel plate clad with SMO 254 by roll bonding or explosion bonding, or carbon steel lined with SMO 254 sheet, can reduce cost while keeping the corrosion-resistant layer on the wetted side. Please send your requirement for confirmation.

Ordering SMO 254 sheets and plates

Please give the specification, thickness, width and length or cut sizes, finish, quantity and any testing such as G48 pitting test, ultrasonic test or third-party inspection. Sheets are packed flat on pallets with interleaving, and plates on wooden skids; each piece is marked with grade, specification, heat number and size.

Why choose SMO 254 plate

Compared with 316L plate, SMO 254 gives a large step up in resistance to pitting, crevice corrosion and chloride stress corrosion cracking, together with about 50% higher yield strength, which can allow thinner plates. Compared with super duplex plate, it is fully austenitic, easier to form and weld in thin gauges, and tougher at low temperatures, although super duplex is stronger. Compared with nickel alloys such as Inconel 625 or Hastelloy C276, it costs considerably less and is adequate for many seawater and bleach-plant duties. The final choice depends on the chloride level, temperature, pH and crevice conditions of the process.

Sizes and cutting

SMO 254 sheets are supplied in standard mill sizes, cold rolled with 2B finish, and plates in hot-rolled widths and lengths. Sheets and plates can be cut to size by shearing, plasma or water-jet, and circles and rings can be cut from plate. Each piece keeps the heat number of the parent plate for traceability. Theoretical weight can be estimated with our weight calculator using a density of about 8.0 g/cm³.

Applications and related products

SMO 254 sheets and plates are used in bleach plants, flue-gas scrubbers, seawater heat exchangers and desalination, and chloride-bearing chemical processes. Matching products include SMO 254 pipes and tubes, SMO 254 round bars, SMO 254 flanges, SMO 254 pipe fittings. Background on the alloy is on the SMO 254 page. Other materials are on our plates and sheets pages.