654SMO Forgings: UNS S32654 / EN 1.4652 Super Austenitic Stainless Steel
Seamless rolled rings, forged flanges, round bars, discs, sleeves, shafts, tube sheets and valve parts, forged to drawing in Jiangyin, China. Page updated September 2026.
UNS S32654EN 1.465200Cr24Ni22Mo7Mn3CuN 7Mo super austeniticPREN above 50
654SMO is a nitrogen-alloyed super austenitic stainless steel, designated UNS S32654 and EN 1.4652. Typical chemistry is 24 to 25 percent chromium, 21 to 23 percent nickel, 7 to 8 percent molybdenum and 0.45 to 0.55 percent nitrogen. That combination of molybdenum and nitrogen gives the highest chloride pitting and crevice corrosion resistance found in the austenitic stainless family, close to nickel-base alloy territory, and the nitrogen also lifts strength above 904L and 254 SMO. Jiangyin Jiangnan Metal Co., Ltd. forges 654SMO to customer drawings, solution annealed, ultrasonically tested and certified to EN 10204 3.1 or 3.2.
654SMO Chemical Composition
| Element | Symbol | Content (%) | Purpose |
|---|---|---|---|
| Carbon | C | 0.02 max | Held low against carbide sensitisation |
| Chromium | Cr | 24.0 to 25.0 | Passive film stability, base of PREN |
| Nickel | Ni | 21.0 to 23.0 | Austenite stability, resistance to SCC |
| Molybdenum | Mo | 7.0 to 8.0 | Pitting and crevice corrosion resistance |
| Nitrogen | N | 0.45 to 0.55 | Strength and pitting resistance |
| Manganese | Mn | 2.0 to 4.0 | Raises nitrogen solubility in the melt |
| Copper | Cu | 0.30 to 0.60 | Resistance in reducing acids |
| Silicon | Si | 0.50 max | Deoxidation |
| Phosphorus | P | 0.030 max | Residual, controlled |
| Sulphur | S | 0.005 max | Cleanliness and hot workability |
| Iron | Fe | Balance |
Mechanical Properties of 654SMO Forgings
The figures below apply to the solution annealed condition. Published data for S32654 solution treated at 1100 to 1150 degrees C reports roughly 750 MPa tensile strength, 430 MPa yield strength, 40 percent elongation and around 250 HB, which matches the minima we certify.
| Property | Imperial | Metric |
|---|---|---|
| Tensile strength, Rm | min 109 KSI | min 750 MPa |
| Yield strength, Rp0.2 | min 62 KSI | min 430 MPa |
| Elongation, A | min 40 % | min 40 % |
| Hardness, typical | about 250 HB | |
| Heat treatment | 1100 to 1150 C, rapid quench |
Corrosion Performance and PREN
Pitting resistance is normally ranked by the pitting resistance equivalent number, PREN = %Cr + 3.3 x %Mo + 16 x %N. On the nominal 654SMO chemistry this puts the grade above 50, against a PRE of about 43 for 254 SMO (UNS S31254). That margin is what lets 654SMO run in chlorinated seawater and hot chloride service where 6Mo grades reach their crevice corrosion limit.
| Characteristic | 254 SMO / S31254 | 654SMO / S32654 |
|---|---|---|
| Family | 6 percent Mo super austenitic | 7 percent Mo super austenitic |
| Molybdenum | about 6 % | 7 to 8 % |
| Nitrogen | about 0.2 % | 0.45 to 0.55 % |
| Chromium / Nickel | about 20 % / 18 % | 24 to 25 % / 21 to 23 % |
| PRE / PREN | about 43 | above 50 |
| Relative cost | Lower | Higher |
| Typical selection | Most high-corrosion industrial duties | Severe hot, high-chloride and aggressive chemical duties |
Where service conditions sit inside the 254 SMO envelope, that grade is usually the more economical specification, and we forge it as well. See our A182 F44 (S31254) forgings. Specify 654SMO when temperature, chloride level or the cost of downtime justify the upgrade.
654SMO Forged Products We Manufacture
Seamless Rolled Rings
Radial and axial rolled 654SMO rings for separators, heat exchangers and pressure vessel shells.
Forged Flanges
Weld neck, blind, slip-on and special-bore flanges for seawater, firewater and subsea pipework.
Round Bars and Hollow Bars
Forged and peeled bar stock for machining into pump, valve and instrument components.
Discs, Blanks and Tube Sheets
Solid discs and drilled tube sheets for shell and tube and plate heat exchangers.
Sleeves and Bushings
Thick-wall forged sleeves and bushings for compressors, generators and subsea equipment.
Shafts, Spindles and Nozzles
Stepped and eccentric shafts, spindles, nozzles and crankshaft blanks to drawing.
Valve Components
Valve bodies, stems, seat rings and blocks for ball, gate, globe, check and plug valves.
Custom Open-Die Forgings
Manifolds, rolls, wheels and structural parts produced from your drawing or sketch.
Typical Applications of 654SMO
Seawater and offshore systems
Seawater, firewater and subsea pipework with the associated risers, manifolds, pressure vessels, valves and heat exchangers, plus subsea and deepwater production equipment.
Desalination and water treatment
Desalination plants, high pressure reverse osmosis trains, seawater piping, demineralised water production and waste water systems.
Chemical and petrochemical processing
Equipment handling pure acids and acids carrying chloride ions, sulphuric acid in particular, as well as organic and mixed acids at raised pressure and temperature.
Power generation and flue gas cleaning
Flue gas desulphurisation systems, waste incineration scrubbers, cooling systems and power generator components.
Pulp, paper, food and pharmaceuticals
Chlorine and chlorine dioxide bleaching equipment, digesters and storage tanks, together with hydrometallurgy, food and beverage and pharmaceutical process equipment.
Standards, Inspection and Certification
654SMO plate and sheet is covered by ASTM A240 and ASME SA-240 under UNS S32654. Forgings are produced to the purchase specification stated on your order. If a piping component specification such as ASTM A182 is required, confirm the applicable grade designation with us at enquiry stage so the material certificate matches the order exactly.
Every 654SMO forging is solution annealed and quenched, then ultrasonically tested to EN 10228-3, SEP 1921 or ASTM A388 as specified. Documentation is issued as an EN 10204 3.1 mill certificate, or an EN 10204 3.2 certificate endorsed by a third party inspection body such as TUV, SGS, BV or Lloyd's on request. PMI, intergranular corrosion testing to ASTM A262, ASTM G48 pitting tests, impact testing and dimensional reports can be added.
654SMO Questions and Answers
What is 654SMO stainless steel?
A nitrogen-alloyed super austenitic stainless steel designated UNS S32654 and EN 1.4652, listed in Chinese practice as 00Cr24Ni22Mo7Mn3CuN. Its 7 to 8 percent molybdenum and 0.45 to 0.55 percent nitrogen give the highest chloride pitting and crevice corrosion resistance of the austenitic stainless grades.
Is 654SMO a powder metallurgy steel?
No. Published data for S32654 lists AOD or VOD decarburisation refining and continuous casting as the production routes. Our billet is melted by EAF plus VOD, with electroslag remelting available on request.
What is the difference between 254 SMO and 654SMO?
254 SMO carries about 6 percent molybdenum and 0.2 percent nitrogen, with a PRE near 43. 654SMO carries 7 to 8 percent molybdenum and around 0.5 percent nitrogen, with a PREN above 50, so it holds up in hotter and more concentrated chloride service at a higher material cost.
Can 654SMO be welded?
Yes, with standard austenitic welding processes. Over-alloyed nickel-base filler metals are normally specified so that weld metal corrosion resistance matches the parent material, and heat input is kept controlled to limit intermetallic precipitation. Confirm the welding procedure with your fabricator before purchase.
What heat treatment do the forgings receive?
Solution annealing near 1100 to 1150 degrees C followed by rapid quenching. Published data for this condition gives about 750 MPa tensile strength, 430 MPa yield strength and 40 percent elongation, which matches the minima on our certificates.
What sizes and weights can you forge?
Ring outside diameter, wall thickness and single piece weight depend on the item. Send the drawing or rough dimensions with your enquiry and we will confirm feasibility, tolerance and lead time before quoting.
How do I get a quotation?
Email the drawing or rough dimensions, quantity, required standard and certification level to sales@steelforgepieces.com, or call +86 189 2135 9659. Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China.
Request a 654SMO Forging Quotation
Send a drawing, a sketch, or simply the rough dimensions. We quote open-die forgings, seamless rolled rings and machined-to-print parts in 654SMO and across the super austenitic, duplex and nickel alloy range.
Email sales@steelforgepieces.com
Related Corrosion-Resistant Grades
Comparable grades we forge include A182 F44 / 254 SMO (S31254), 904L, Sanicro 28, Alloy 31 and Incoloy 926. For duplex and super duplex requirements see F51, F53, F55 and F61. For the most aggressive acid service see Hastelloy C-276 and Inconel 625.