254 SMO (S31254)

What is 254 SMO and its applications?

254 SMO (UNS S31254) is a high-alloy austenitic stainless steel containing molybdenum and nitrogen. It is used in seawater-handling equipment, pulp bleaching and gas-cleaning systems.

Seawater systems: Cooling-water, ballast-water and associated components.
Pulp bleaching: Equipment in aggressive process streams.
Gas cleaning: Components exposed to compatible corrosive condensates.

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Engineering Application & Selection Guide

Chromium, molybdenum and nitrogen improve resistance to localized corrosion; nitrogen also contributes strength. PREN is a composition-based screening measure, not proof of immunity to crevice corrosion or stress-corrosion cracking.

254 SMO stud bolts — For seawater flanges, provide temperature, chlorination, stagnation and crevice details.
254 SMO hex bolts — For bleach-plant joints, specify the complete process chemistry and compatible tightening procedure.
254 SMO socket head cap screws — For compact fluid controls, review trapped solution and access for inspection beneath heads and washers.

Compare 254 SMO and Duplex 2205 using both corrosion requirements and condition-specific mechanical data. An austenitic structure avoids the duplex phase balance, but does not make 254 SMO immune to detrimental precipitation during arbitrary thermal exposure.

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254 SMO Composition

Composition limits · wt.%

ElementWeight %

Cr: 19.5–20.5%
Ni: 17.5–18.5%
Mo: 6.0–6.5%
N: 0.18–0.25%
Cu: 0.50–1.0%
C: ≤0.02%
Mn: ≤1.0%
P: ≤0.03%
S: ≤0.010%
Si: ≤0.80%

ASTM / ASME specifications by product form

Finished-product requirements

Specify the finished-fastener mechanical requirements, condition and inspection separately from the starting-stock specification.

254 SMO hex bolt requirements ↗

Fasteners · dimensional references

Product	Reference
Hex bolts	ISO 4014 / ISO 4017 · ASME B18.2.1
Threaded studs	DIN 976-1 · ASME B18.31.2
Hex nuts	ISO 4032 · ASME B18.2.2
Socket head screws	ISO 4762 · ASME B18.3
Flat washers	ISO 7089 / ISO 7090 · ASME B18.21.1
Custom fasteners	Customer drawing

Raw-material specifications

Product form / scope	Reference
Bar & shapes · Specify grade, condition and order requirements.	ASTM A276
Plate	ASTM A240 / EN 10088-2

Dimensions do not define material or finished-part compliance. Specify the grade, condition and applicable requirements.

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254 SMO Mechanical Properties

Reference sample and condition

Data basis: Catalogue reference minimums
Gauge length: A5, as labelled in supplied table

Key properties	Value
Tensile strength	≥650 MPa
0.2% yield strength	≥300 MPa
Elongation	≥35%

Supplied technical reference · Scanned PDF page 2 · printed page 14

Procurement and application guide

Specify the material and final condition

Check crevices, chloride concentration and temperature.

Material forms in the technical reference: Bar · Shapes · Plate.

Define the finished-part acceptance

Include the material or bolting specification, required final condition, dimensions and quantity. State the service medium, temperature and loading where known. Agree the required tests, inspection coverage and acceptance criteria for the finished part.

Start with the information you have

Send a drawing or share the product form and dimensions. Identify any undecided requirements for review rather than copying a typical property value into the purchase order.

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