254 SMO
254 SMO is a high-alloy austenitic stainless steel developed for severe chloride service. Its high chromium, nickel, molybdenum and nitrogen contents provide strong resistance to pitting, crevice corrosion and stress-corrosion cracking. The requested 250SMO folder name is retained only for URL compatibility; the recognized grade designation is 254 SMO / UNS S31254.
254 SMO Information
254 SMO is a high-alloy austenitic stainless steel developed for severe chloride service. Its high chromium, nickel, molybdenum and nitrogen contents provide strong resistance to pitting, crevice corrosion and stress-corrosion cracking. The requested 250SMO folder name is retained only for URL compatibility; the recognized grade designation is 254 SMO / UNS S31254.
Metallic winding and compatible ring components where service conditions are suitable.
| UNS Number | S31254 |
|---|---|
| EN / Werkstoff | 1.4547 |
| Material Type | 6% molybdenum super-austenitic stainless steel |
| Requested URL | /materials/special-alloys/254-smo/ (legacy folder retained) |
| Common / Applicable Specification | ASTM A240 / A240M |
| Typical Gasket Use | Metallic winding and compatible ring components where service conditions are suitable. |
254 SMO Chemical Composition
Reference composition limits are shown below. Exact requirements should be confirmed against the applicable product specification and certified material documentation.
| Element / Constituent | Symbol | Composition / Information |
|---|---|---|
| Carbon | C | 0.020 max. |
| Manganese | Mn | 1.00 max. |
| Silicon | Si | 0.80 max. |
| Phosphorus | P | 0.030 max. |
| Sulfur | S | 0.010 max. |
| Chromium | Cr | 19.50–20.50 |
| Nickel | Ni | 17.50–18.50 |
| Molybdenum | Mo | 6.00–6.50 |
| Nitrogen | N | 0.18–0.22 |
| Copper | Cu | 0.50–1.00 |
| Iron | Fe | Balance |
254 SMO Mechanical Properties
Reference room-temperature properties are shown for a commonly supplied condition. Exact requirements depend on product form, size, heat treatment and governing specification.
| Property | Reference Value | Unit / Basis |
|---|---|---|
| Tensile Strength | 650 min. | MPa |
| 0.2% Offset Yield Strength | 300 min. | MPa |
| Elongation | 35 min. | % |
| Hardness | 223 max. | HBW |
Values shown are engineering reference data, not universal design allowables. Final procurement and design must use the governing specification, exact product form/condition and certified material test documentation.
254 SMO Physical & Service Information
Reference physical properties and service considerations relevant to material selection for Spiral Wound Gaskets.
| Density | Approx. 8.0 g/cm³ |
|---|---|
| Structure | Austenitic |
| Corrosion Behaviour | Very strong resistance to chloride pitting and crevice corrosion compared with conventional 300-series stainless steels. |
| Heat Treatment | Normally solution annealed; not hardened by heat treatment. |
| Service Selection | Use where chloride concentration, temperature and process chemistry justify a highly alloyed stainless steel. |
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