Overview
654SMO seamless stainless steel pipe (UNS S32654, EN 1.4652) is a premium super austenitic alloy designed for extreme resistance to pitting, crevice corrosion, and stress-corrosion cracking (SCC) in highly chlorinated environments. Composed of 24-26% chromium, 21-23% nickel, 7-8% molybdenum, 0.4-0.6% nitrogen, and balanced iron, it holds the highest alloy content among commercial austenitic steels, achieving a Critical Pitting Temperature (CPT) >80°C. Manufactured via seamless hot-piercing and cold-drawing to ensure tight dimensional control, it complies with standards like ASTM A213, ASME SA213, and EN 10216-5.
The combination of high chromium, molybdenum, and nitrogen creates a robust passive film that resists even the most aggressive chloride solutions, making 654SMO a cost-effective alternative to nickel-based alloys in certain applications.
Chemical Composition
| Grade | C | Si | Mn | P | S | Cr | Ni | Cu | N | Mo |
| 654 SMO/UNS S32654 | ≤0.02 | ≤0.50 | 2.00-4.00 | ≤0.03 | ≤0.005 | 24.00-25.00 | 21.00-23.00 | 0.30-0.60 | 0.45-0.55 | 7.00-8.00 |
654 SMO Stainless Steel Standards Comparison Table
| STS | USA | UNS | CHINA | EURONORM | RUSSIA | SWEDISH | JAPANESE |
| GRADE | AISI/ASTM | NO | GB | NO | NAME | GOST | SS | JIS |
| 654 SMO | 654 SMO | S32654 | – | 1.4652 | – | – | – | – |
Features
Unmatched Chloride Resistance: Resists pitting in seawater (35,000 ppm Cl⁻) at 60°C and crevice corrosion in stagnant chloride solutions (50,000 ppm Cl⁻ + 1000 ppm Fe³⁺).
High Strength & Ductility: Nitrogen strengthens the austenitic matrix, providing yield strength (≥350 MPa) twice that of 316L without compromising formability.
Temperature Range: Operates from -196°C (cryogenic) to 400°C, with good oxidation resistance up to 850°C in intermittent service.
Fabrication Flexibility: Weldable using GTAW with 654SMO filler metal; cold forming requires preheating for thick sections to prevent strain-induced martensite.
Mechanical Properties
| Grade | Tensile strength (MPa) | 0.2% proof strength (MPa) | Min. elongation at fracture (%) | Brinell hardness (HB) |
| 654SMO | ≥750 | ≥430 | ≥40 | ≤310 |
Applications
1) Refining, chemical equipment;
2) Flue gas desulfurization device for thermal power generation, wastewater treatment;
3) Atomic power generation, comprehensive utilization of coal, and ocean wave power generation;
4) Marine structures in the sea environment, seawater desalination, marine aquaculture, seawater heat exchange;
5) Salt production, soy sauce brewing food field;
6) Paper industry, high concentration chloride ion environment of various bleaching devices;
7) Oil and gas industry equipment;
8) Offshore platforms, heat exchangers, underwater equipment, firefighting equipment;
9) Chemical processing industry, utensils and pipeline industry;
10) Desalted plants, high pressure RO plants and submarine pipelines;
11) High-strength, corrosion-resistant mechanical equipment and components;
12) Others.
Material Summary
654SMO(EN 1.4652/UNSS32654) is a special stainless steel containing a high percentage of Nickel and Chromium containing 7% Molybdenum,which is the highest corrision restistance in the world.
It has a fairly high electrical conductivity among wrought superaustenitic stainless steels. In addition, it has the lowest thermal conductivity and very high tensile strength.
654SMo (S32654, 1.4652) super austenitic stainless steel features very good local corrosion resistance, good pitting resistance and good stress corrosion resistance under seawater, aeration, gap and low speed scouring conditions. It can be used as a good substitute to nickel-based alloys and titanium alloys. When it comes to high-temperature resistance or corrosion resistance, it is also superior to 904L and 254SMo.
