904L Forgings, UNS N08904 / EN 1.4539, to ASTM A182 F904L
Seamless rolled rings, flanges, discs, shafts, bars, sleeves and tube sheets, forged and solution annealed by Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China.
904L (UNS N08904, EN 1.4539, X1NiCrMoCu25-20-5) is a non-stabilised low carbon high alloy austenitic stainless steel of roughly 20 % Cr, 25 % Ni, 4.5 % Mo and 1.5 % Cu. The copper gives it resistance to reducing acids, sulphuric acid above all; the nickel and molybdenum give resistance to chloride pitting, crevice corrosion and stress corrosion cracking. Jiangyin Jiangnan Metal Co., Ltd. forges 904L to ASTM A182 F904L as rolled rings, flanges, discs, shafts, sleeves, bushings, tube sheets and shapes to drawing, with ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921 and certificates to EN 10204 3.1 or 3.2.
What 904L is
904L holds carbon to 0.02 % maximum, low enough that chromium carbides do not precipitate at the grain boundaries during welding, so no stabilising element is needed. The nickel content of 23 to 28 % is the reason for its resistance to chloride stress corrosion cracking, and the 1 to 2 % copper is what separates it from 316L: copper is what carries the alloy through sulphuric and other reducing acids, particularly in the aggressive mid concentration range. The alloy is non-magnetic in all conditions, and its austenitic structure keeps toughness down to cryogenic temperatures.
With a pitting resistance equivalent of about 35, 904L handles warm seawater and other high chloride media well. Its overall corrosion performance sits between 316L and the 6 % molybdenum super austenitic grades. It is worth knowing the limits too: in aggressive nitric acid it is less resistant than molybdenum free grades such as 304L and 310L, and it costs a great deal more than the standard austenitics because of its nickel and molybdenum content. A number of duties once given to 904L are now covered by duplex 2205 at lower cost.
Chemical composition
| Element | C | Mn | Si | P | S | Cr | Ni | Mo | Cu |
|---|---|---|---|---|---|---|---|---|---|
| A182 F904L | 0.02 max | 2.00 max | 1.00 max | 0.04 max | 0.03 max | 19.00–23.00 | 23.00–28.00 | 4.00–5.00 | 1.00–2.00 |
| Typical heat | 0.015 | 1.5 | 0.4 | 0.025 | 0.001 | 20.0 | 25.0 | 4.5 | 1.5 |
Flat product specifications quote slightly wider limits for phosphorus and sulphur, so datasheets do not always agree. For forgings, the A182 F904L limits above are the ones that govern the order. Nitrogen is normally around 0.10 % in commercial heats. Free machining additions such as lead or selenium are not permitted under A182.
Mechanical and physical properties
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min | 490 MPa | 71 ksi |
| Yield strength, 0.2 % offset, min | 215 MPa | 31 ksi |
| Elongation in 2 in., min | 35 % | 35 % |
| Reduction of area | Not specified in A182 for this grade | |
| Hardness | Not specified in A182; purchasers often call for 220 HBW max | |
| Property | Value |
|---|---|
| Density | 7.95 g/cm³ |
| Modulus of elasticity | 190 GPa |
| Thermal expansion | 15.8 µm/m·°C |
| Thermal conductivity | 11.5 W/m·K |
| Specific heat, 0–100 °C | 450 J/kg·K |
| Electrical resistivity | 9.52 µΩ·cm |
| Magnetic response | Non-magnetic in all conditions |
| Pitting resistance equivalent | About 35 |
Equivalent designations
| System | Designation |
|---|---|
| ASTM / AISI | 904L; forgings F904L |
| UNS | N08904 |
| EN number | 1.4539 |
| EN name | X1NiCrMoCu25-20-5 |
| France | Z2 NCDU 25-20 |
| United Kingdom | 904S13 |
| Sweden | SS 2562 |
| Trade names | URANUS B6, NAS 255, FO 25-20 U |
Forging route and heat treatment
Billets are hot worked between about 950 and 1150 °C. Working below 950 °C is avoided because the alloy becomes crack sensitive. ASTM A182 then requires the forging to be cooled below 538 °C (1000 °F) before heat treating, followed by solution treatment at 1050 to 1150 °C (1920 to 2100 °F) and a liquid quench down below 260 °C (500 °F). General mill datasheets give the wider solution treatment range of 1090 to 1175 °C with rapid cooling. The alloy takes no strength from heat treatment; it cannot be hardened thermally.
Melting is by electric furnace with separate degassing and refining, by vacuum furnace, or by either route followed by vacuum arc or electroslag consumable remelting, as A182 allows. Sufficient discard is taken from the ingot to clear piping and segregation, and the part is forged as close to final shape as the geometry allows. A182 also puts practical limits worth knowing at the enquiry stage: parts are limited to 4540 kg (10 000 lb) each, above which austenitic forgings go to ASTM A965, and flanges, elbows, return bends and tees may not be machined from bar stock. Cylindrical parts may be machined from solution annealed forged or rolled bar without further hot working.
Corrosion behaviour and service limits
904L was developed for sulphuric acid and keeps that reputation, but it also performs across phosphoric and acetic acid, in chloride bearing process water and in warm seawater. For the best stress corrosion cracking resistance in critical service, the steel should be solution treated after cold work. Oxidation resistance is good, but like other high alloy grades it precipitates brittle phases such as sigma at temperature, so it should not be used above about 550 °C; design stress values in the ASME Boiler and Pressure Vessel Code extend to 371 °C. In the other direction the grade stays tough into cryogenic service.
Welding can be carried out by all standard processes with matching filler such as ER385 to AWS A5.9. The weld metal solidifies fully austenitic, which makes restrained joints sensitive to hot cracking, so joint design and heat input matter. No preheat is used and post weld heat treatment is normally not required. In machining, 904L is a clean low sulphur grade and will not cut as freely as a free machining steel, but it responds to standard techniques with rigid setups and positive feeds.
904L forged products
Every item is made from a traceable heat and supplied rough machined, proof machined or finish machined to drawing.
Ring rolled 904L rings and rolled ring blanks for pumps, valves and vessels.
Weld neck, blind, slip on, lap joint and special flanges to ASME B16.5, B16.47, EN 1092-1 or drawing.
Forged discs, tube sheets and blind blanks for heat exchangers and reactors.
Pump shafts, agitator shafts, eccentric shafts and stepped forged shafts.
Forged round and square bars, hollow bars for valve and fitting machining.
Forged sleeves, bushings, cylinders and hollow sections.
Valve bodies, bonnets, stems, seat rings and forged blocks.
Nozzles, manifolds, rolls, gears and near net open-die forging parts.
Diameter, section and unit weight depend on press and ring mill capacity. Send the drawing and we confirm the forging route, forging weight and delivery before quoting.
Where 904L forgings are used
Chemical plant takes the largest share: rings, flanges, shafts and tube sheets for sulphuric, phosphoric and acetic acid service, fertiliser production, and pulp and paper bleaching circuits. In marine and seawater work the grade is specified for seawater cooling equipment, pumps, gate valves on tanker ballast systems, desalination internals and deep sea sampling and incubation chambers. Refinery and oil and gas users apply it to downhole and production equipment, wellhead and Christmas tree parts, gas scrubbing plant and flue gas cleaning. It also appears in hydrometallurgy and minerals processing, heat exchangers, crystallisers, storage tanks and reactors, pharmaceutical and food processing equipment, and electrostatic precipitator internals.
Testing, inspection and certification
Non-destructive testing is carried out to ASTM A388, EN 10228-3 or SEP 1921 as agreed on the order. The standard test package covers chemical analysis and PMI, tensile and yield strength with elongation, hardness, intergranular corrosion testing to ASTM A262 where the purchaser calls for it, and dimensional inspection against the approved drawing. Mechanical test specimens are taken from production forgings or from separately forged test blanks heat treated with the finished product, and are not removed until heat treatment is complete, as A182 requires. Certificates are issued to EN 10204 3.1, or to EN 10204 3.2 with third party witness by TUV, SGS, BV, LR or DNV.
904L against the alternatives
| Grade | Case for it over 904L | Case for staying with 904L |
|---|---|---|
| 316L | Much lower cost, widely stocked. | Far lower corrosion resistance in acids and chlorides. |
| Duplex 2205 | Higher strength at lower cost with similar corrosion resistance; now covers many former 904L duties. | Not suited above about 300 °C, and 904L holds the edge in sulphuric acid through its copper. |
| 6 % Mo super austenitics such as Alloy 926 and Alloy 31 | Higher pitting and crevice corrosion resistance. | 904L is the cheaper choice when 6 Mo performance is not needed. |
| 304L and 310L | Better in aggressive nitric acid, being molybdenum free. | Both are well behind 904L in chlorides and reducing acids. |
| Hastelloy C-276 and Alloy 59 | Mixed acid and hot chloride duties beyond stainless capability. | Nickel alloys carry a heavy cost premium over 904L. |
The manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. We forge stainless steel, nickel alloy, alloy steel, tool steel and carbon steel into rings, seamless rolled rings, flanges, discs, bars, shafts, sleeves and tube sheets, working from customer drawings rather than a fixed catalogue. Enquiries are handled by engineers who confirm the forging route, heat treatment condition, test package and certification before a price goes out. Call 0086-189-2135-9659 or write to sales@steelforgepieces.com.
Questions we are asked about 904L
What is 904L stainless steel?
A non-stabilised low carbon high alloy austenitic stainless steel, UNS N08904 and EN 1.4539, running about 20 % chromium, 25 % nickel, 4.5 % molybdenum and 1.5 % copper. Copper handles reducing acids such as sulphuric; nickel and molybdenum handle chloride pitting, crevice corrosion and stress corrosion cracking. It is non-magnetic in all conditions and has a pitting resistance equivalent around 35.
Which standard covers 904L forgings?
ASTM A182 / A182M grade F904L, covering forged flanges, fittings, valves and parts for pressure systems. Products to A182 are capped at 4540 kg each; heavier austenitic forgings go to ASTM A965. General forging requirements sit in ASTM A788.
What mechanical minimums apply to A182 F904L?
Tensile 490 MPa (71 ksi) minimum, 0.2 % yield 215 MPa (31 ksi) minimum, elongation in 2 in. 35 % minimum. Reduction of area and hardness are not specified for the grade in A182, though purchasers often add a 220 HBW maximum.
How is 904L heat treated after forging?
Cool below 538 °C after hot working, solution treat at 1050 to 1150 °C, then liquid quench to below 260 °C. Mill datasheets quote 1090 to 1175 °C with rapid cooling as the general range. The grade cannot be hardened by thermal treatment.
Is 904L better than 316L?
In acids and chlorides, clearly. It carries more chromium, nickel and molybdenum plus copper, so sulphuric and phosphoric acid, warm seawater and pitting are all handled far better. 316L costs much less, so 904L is specified only when the medium demands it. Duplex 2205 is the usual middle ground below about 300 °C.
What temperature can 904L work at?
Not above about 550 °C, because brittle phases such as sigma precipitate. ASME Boiler and Pressure Vessel Code design stress values run to 371 °C. Low temperature service is no problem; the austenitic structure stays tough into cryogenic range.
Can 904L be welded?
Yes, by all standard processes with matching filler such as ER385 to AWS A5.9. It solidifies fully austenitic and so is prone to hot cracking in restrained weldments. No preheat, and post weld heat treatment is usually unnecessary.
What testing comes with the forgings?
Ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921, chemical analysis and PMI, tensile and elongation, hardness, intergranular corrosion testing to ASTM A262 on request, and dimensional inspection. Certificates to EN 10204 3.1, or 3.2 with third party witness.
How do I get a price?
Email the drawing or rough sizes, quantity, specification and certificate requirement to sales@steelforgepieces.com, or call 0086-189-2135-9659. We reply within one working day.
Ask for a 904L quotation
Rolled rings, flanges, discs, shafts, sleeves, tube sheets and shapes to drawing in 904L, UNS N08904, 1.4539, certified to EN 10204 3.1 or 3.2.