2.4856 Forgings: NiCr22Mo9Nb / UNS N06625 / Alloy 625 Forged Rings, Flanges, Shafts and Discs
2.4856 is the EN/DIN material number for NiCr22Mo9Nb, a solid-solution-strengthened nickel-chromium-molybdenum-niobium alloy containing at least 58 % nickel, 20–23 % chromium, 8–10 % molybdenum and 3.15–4.15 % niobium. It is the same chemistry as UNS N06625, is commonly called Alloy 625, and is sold by Special Metals Corporation under the trademark Inconel® 625. Its PREN of roughly 51 puts it well beyond the reach of chloride pitting, and it is treated as immune to chloride stress-corrosion cracking. Usable strength runs from cryogenic temperatures to about 982 °C.
Jiangyin Jiangnan Metal Co., Ltd., an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China, forges 2.4856 into seamless rolled rings, flanges, shafts, discs, tube sheets, sleeves, bushings, valve components and round bar in diameters from 80 mm to 6,000 mm, lengths to 12,000 mm and single-piece weights from 10 kg to 15,000 kg. Material is supplied to ASTM B564 Grade 1 (annealed) or Grade 2 (solution annealed) with EN 10204 3.1 mill certificates as standard and 3.2 third-party witnessed certificates on request. Enquiries: 0086-189-2135-9659 · sales@steelforgepieces.com.
- Material no.
- 2.4856NiCr22Mo9Nb
- UNS
- N06625Alloy 625
- Nickel
- ≥ 58 %balance
- Density
- 8.44g/cm³ (0.305 lb/in³)
- PREN
- ≈ 51Cr + 3.3 Mo
- UTS, Gr 1
- ≥ 827MPa (120 ksi) min
- Max service
- 982 °CGrade 2, ASME code limit
- Melting range
- 1290–1350°C
What is material 2.4856?
2.4856 is a nickel-base alloy designed to do two things at once: resist aggressive aqueous corrosion, and hold strength at temperature. The chromium provides the passive film and oxidation resistance. The 8–10 % molybdenum suppresses pitting and crevice attack in chlorides and gives most of the solid-solution strengthening. The 3.15–4.15 % niobium adds further solid-solution strengthening and ties up carbon as NbC, which is why 2.4856 resists sensitisation in the heat-affected zone after welding. Because the nickel content exceeds 58 %, the alloy is austenitic and non-magnetic in every delivery condition, and it is one of very few structural alloys considered effectively immune to chloride stress-corrosion cracking.
A point that is frequently misunderstood on procurement documents: 2.4856 is not an age-hardening alloy. Its strength comes from solid solution, not from precipitates. ASTM B564 recognises only two delivery conditions: annealed (Grade 1) and solution annealed (Grade 2). Holding the alloy between roughly 550 °C and 750 °C does precipitate γ″ (Ni₃Nb) and will raise strength, but it costs ductility and toughness and is not a specified condition. If a drawing calls for "solution treatment plus ageing" on 2.4856, that callout belongs to a precipitation-hardening grade such as 2.4668 / Alloy 718, not to this one.
Seawater and chlorides
PREN ≈ 51 puts 2.4856 above super-duplex and 6 Mo austenitics. Used for subsea manifolds, riser components, seawater lift-pump parts and desalination hardware.
Sour service
Listed in NACE MR0175 / ISO 15156-3 for H₂S environments in the annealed or solution-annealed condition, which makes it a default for wellhead, christmas-tree and downhole parts.
High temperature
Grade 2 material carries ASME code allowables to 982 °C. Used for flue-gas desulphurisation, incinerator internals, aero exhaust hardware and heat-exchanger tube sheets.
Fabricability
Welds with matching ERNiCrMo-3 filler and needs no post-weld heat treatment for corrosion service. That is one reason the same alloy dominates weld overlay and cladding.
What are the equivalent designations of 2.4856?
Engineers arrive at this alloy from at least eight different naming systems. All of the designations below describe the same chemistry, and Jiangyin Jiangnan Metal Co., Ltd. accepts purchase orders written against any of them, issuing a multi-designation mill certificate that lists every specification the heat satisfies.
| Region / body | Designation | Notes |
|---|---|---|
| Germany · EN / DIN | 2.4856 · NiCr22Mo9Nb | Material number and chemical designation; DIN 17744, EN 10302, VdTÜV Werkstoffblatt 499 |
| USA · UNS | N06625 | Unified Numbering System; the designation to quote on international purchase orders |
| USA · common name | Alloy 625 | Generic industry name, not a trademark |
| USA · ASTM forgings | ASTM B564 | Nickel alloy forgings; the governing spec for rings, flanges, discs and shafts |
| USA · ASTM bar | ASTM B446 | Hot-worked rod and bar; forging-quality bar is furnished to chemistry and surface inspection |
| USA · ASTM plate / tube | ASTM B443 · B444 · B366 | Plate, sheet and strip; seamless pipe and tube; fittings |
| USA · ASME | SB-564 · SB-446 · SB-443 | Boiler and Pressure Vessel Code, Section II Part B |
| USA · aerospace | AMS 5666 · AMS 5837 | Bar, forgings and rings; annealed and solution-annealed respectively |
| UK · BS | NA 21 | BS 3072–3076 series |
| Japan · JIS | NCF 625 | JIS G 4901 / G 4902 designation family |
| France · AFNOR | NC22DNb | Also seen as NC22FeDNb |
| China · GB | GH3625 (GH625) · NS3306 (NS336) | Superalloy and corrosion-resistant-alloy designation systems respectively |
| Sour service | NACE MR0175 / ISO 15156-3 | Overlay requirement added to the base specification, not a separate grade |
What is the chemical composition of 2.4856?
The table below gives the EN / VdTÜV limits for NiCr22Mo9Nb alongside the ASTM limits for UNS N06625. Most suppliers present these as identical. They are not quite: the EN specification sets a carbon minimum of 0.03 % that ASTM does not, and ASTM holds phosphorus to half the EN limit. Both differences matter. The carbon minimum exists because carbon contributes to creep strength, so a very low-carbon heat that passes ASTM can fall short of the EN creep dataset. The tighter ASTM phosphorus limit is the cleaner requirement for sour and subsea service.
| Element | EN 2.4856 (NiCr22Mo9Nb) | ASTM B564 UNS N06625 | Function in the alloy |
|---|---|---|---|
| Carbon (C) | 0.03–0.10 min set | 0.10 | Contributes to creep strength; forms NbC and stabilises against sensitisation |
| Silicon (Si) | 0.50 | 0.50 | Deoxidiser; kept low to protect weldability |
| Manganese (Mn) | 0.50 | 0.50 | Deoxidiser |
| Phosphorus (P) | 0.020 | 0.015 tighter | Impurity; promotes hot cracking and grain-boundary weakness |
| Sulphur (S) | 0.015 | 0.015 | Impurity; strongly detrimental to hot workability |
| Chromium (Cr) | 20.0–23.0 | 20.0–23.0 | Passive film, oxidation resistance, pitting resistance |
| Molybdenum (Mo) | 8.0–10.0 | 8.0–10.0 | Pitting and crevice resistance in chlorides; solid-solution strengthening |
| Niobium (Nb, +Ta) | 3.15–4.15 | 3.15–4.15 | Solid-solution strengthening; carbide stabiliser; source of γ″ if mis-heat-treated |
| Iron (Fe) | 5.0 | 5.0 | Residual from raw materials; capped to protect corrosion performance |
| Aluminium (Al) | 0.40 | 0.40 | Deoxidiser residual |
| Titanium (Ti) | 0.40 | 0.40 | Deoxidiser residual; secondary carbide former |
| Cobalt (Co) | 1.0 | 1.0 | Residual; restricted for nuclear service |
| Copper (Cu) | 0.50 | — | Residual; limited by EN only |
| Nickel (Ni) | ≥ 58 | ≥ 58 | Matrix; austenite stability, immunity to chloride SCC |
| Practical consequence: a heat melted to satisfy both the EN carbon minimum and the ASTM phosphorus maximum will pass every other listed specification simultaneously. That is our standard purchasing rule for 2.4856, and it is why we can cross-certify a single heat to ASTM B564, EN 10302 and VdTÜV 499 on one certificate. | |||
Melting route
2.4856 for forging is melted by EAF + AOD/VOD followed by electroslag remelting (ESR), or by VIM + ESR where the cleanliness requirement is higher, for example aerospace rings or subsea pressure-containing parts. ESR is not optional for heavy sections: it controls the segregation of niobium, which otherwise concentrates in the interdendritic regions and produces Laves phase that will not fully dissolve during annealing.
Grade 1 or Grade 2? The one decision that matters most
Every ASTM B564 order for UNS N06625 has to name a grade, and the two grades are not interchangeable. They are the same chemistry given different final heat treatments, and the choice is driven entirely by service temperature.
| Grade 1, annealed | Grade 2, solution annealed | |
|---|---|---|
| Heat treatment | 871 °C minimum | 1093 °C minimum |
| Normal service range | Up to 593 °C (1100 °F) | Above 593 °C, where creep and stress-rupture resistance govern |
| Tensile strength, min | 827 MPa · 120 ksi | 690 MPa · 100 ksi |
| Yield strength 0.2 %, min | 414 MPa · 60 ksi | 276 MPa · 40 ksi |
| Elongation, min | 30 % | 30 % |
| Grain size | Finer | Coarser, by design, for creep life |
| Typical use | Subsea and topside hardware, valve and pump parts, flanges, sour-service components, heat-exchanger tube sheets | Flue-gas and incinerator internals, furnace and exhaust hardware, high-temperature bellows and ducting components |
| Supplied if grade is not stated | Grade 1, the default under the ASTM specifications | Only when explicitly ordered |
Two consequences follow. First, if a drawing quotes a room-temperature yield strength of 414 MPa but the service temperature is 750 °C, the specification is internally contradictory. Grade 2 will not reach that yield strength, and Grade 1 will creep. Second, a stabilisation anneal at 982 °C minimum can be applied after solution annealing to further improve resistance to sensitisation; it is worth naming explicitly when the part will be welded and then exposed to hot acids.
2.4856 service-temperature map
Where the alloy is comfortable, where it needs a decision, and where it stops. Move the selector below and the marker moves with it.
Grade & service-temperature selector
ExclusiveEnter the conditions your 2.4856 part will actually see. The tool returns the grade to specify, the governing design consideration, and any warning that applies. It also moves the marker on the map above.
What are the mechanical properties of 2.4856?
The specification minima are the numbers you can hold a supplier to; the typical values are what a well-processed forging actually delivers. Design to the minima, and expect the typical values on the certificate.
| Property | Grade 1 minimum | Grade 2 minimum | Typical, forged & annealed |
|---|---|---|---|
| Tensile strength Rm | 827 MPa (120 ksi) | 690 MPa (100 ksi) | 830–1000 MPa |
| Yield strength Rp0.2 | 414 MPa (60 ksi) | 276 MPa (40 ksi) | 450–600 MPa |
| Elongation A5 | 30 % | 30 % | 40–55 % |
| Reduction of area | not specified | not specified | 45–60 % |
| Hardness | ≤ 35 HRC where NACE MR0175 applies | 165–240 HB annealed | |
| Charpy V, room temp. | not specified by ASTM; order as a supplementary requirement | > 100 J | |
| Charpy V, −196 °C | supplementary | > 70 J typical | |
| Modulus of elasticity E | 207.5 GPa at 20 °C, falling to about 148 GPa at 870 °C | ||
| Typical values are indicative for open-die forged and annealed sections up to roughly 200 mm. Heavier sections and Grade 2 material trend toward the lower end. Guaranteed values are those on the mill certificate for the specific heat and test location. | |||
Strength at temperature
2.4856 loses yield strength slowly compared with stainless steels. As a planning figure, expect roughly 85 % of room-temperature yield at 400 °C and about 75 % at 650 °C for Grade 1 material. Above 650 °C, short-term tensile data stops being the right design basis: use ASME Section II Part D allowable stresses for Grade 2 and check stress-rupture life for the intended duty. Contact our engineering team if you need the creep dataset for a specific temperature and design life.
Physical properties of 2.4856
| Property | Value | Unit / condition |
|---|---|---|
| Density | 8.44 | g/cm³ (0.305 lb/in³) at 20 °C |
| Melting range | 1290–1350 | °C (2350–2460 °F) |
| Modulus of elasticity | 207.5 | GPa at 20 °C |
| Poisson's ratio | 0.278 | at 20 °C |
| Coefficient of thermal expansion | 12.8 | ×10⁻⁶ / K, 20–93 °C |
| Thermal conductivity | 9.8 | W/m·K at 20 °C, roughly two-thirds that of 316L |
| Specific heat | 410 | J/kg·K at 20 °C |
| Electrical resistivity | 1.29 | μΩ·m at 20 °C |
| Magnetic permeability | 1.0006 | relative, at 20 °C; non-magnetic |
| Curie temperature | < −196 | °C |
| The low thermal conductivity has two practical effects: heat concentrates at the cutting edge during machining, and thick sections need longer soak times to reach annealing temperature through the wall. | ||
How corrosion-resistant is 2.4856?
The pitting resistance equivalent number is the shorthand: PREN = %Cr + 3.3 × %Mo, which for mid-range 2.4856 chemistry gives approximately 21.5 + 3.3 × 9 ≈ 51. For comparison, 316L sits near 25 and super-duplex 2507 near 42. A PREN above about 40 is the usual threshold for ambient seawater service, so 2.4856 clears it with room to spare, and its critical crevice corrosion temperature is well above the range that defeats stainless steels.
- Chloride pitting: excellent
- Crevice corrosion: excellent
- Chloride SCC: effectively immune
- Sulphuric acid: good at all concentrations, moderate temperature
- Phosphoric and organic acids: very good
- Hydrochloric acid: good at low concentration, check temperature
- Sour service H₂S: NACE MR0175 / ISO 15156-3 listed
- Oxidation in air: resistant to about 1050 °C
- Alkalis and seawater: excellent
Two limits should be stated plainly. Hot concentrated reducing acids, notably hydrochloric above moderate concentration and temperature, are better served by a Ni-Mo alloy such as C-276. And material that has spent long periods between 650 °C and 870 °C can suffer intergranular attack because of grain-boundary carbides; where that history is possible, specify an intergranular corrosion test to ASTM G28 Method A on the delivered condition.
Alloy comparison: is 2.4856 the right choice?
Exclusive2.4856 is expensive. This comparison is here so you can confirm it is necessary, or find the cheaper alloy that would also do the job. Relative cost is indexed to 316L = 1.
| Alloy | UNS | PREN | Yield, min | Max service | Cl⁻ SCC | Rel. cost | Choose it when |
|---|---|---|---|---|---|---|---|
| 316L | S31603 | ≈ 25 | 170 MPa | 870 °C* | Susceptible | 1× | Mild chlorides, general process duty |
| 2205 duplex | S32205 | ≈ 35 | 450 MPa | 300 °C | Good | 1.3× | Strength plus moderate chlorides, ambient to 300 °C |
| 2507 super-duplex | S32750 | ≈ 42 | 550 MPa | 300 °C | Very good | 2× | Seawater at ambient, where 300 °C is never exceeded |
| Alloy 825 | N08825 | ≈ 31 | 241 MPa | 540 °C | Resistant | 2.5× | Sulphuric acid duty where 625 is over-specified |
| 2.4856 / Alloy 625 | N06625 | ≈ 51 | 414 MPa | 982 °C | Immune | 4–5× | Seawater, sour service, or high temperature, especially two of them at once |
| Alloy C-276 | N10276 | ≈ 70 | 283 MPa | 1040 °C | Immune | 6× | Hot reducing acids, notably HCl and wet chlorine |
| 2.4668 / Alloy 718 | N07718 | ≈ 30 | 1030 MPa | 650 °C | Resistant | 5× | High strength needed at temperature; it is age-hardened |
| * 316L retains oxidation resistance to 870 °C but has almost no useful design strength there. Cost indices are indicative for forged product and move with LME nickel and ferro-molybdenum. Values are published typical figures for comparison only. Design to the applicable specification. | |||||||
Where the money goes
If your part sees ambient seawater and nothing hotter than 300 °C, super-duplex is usually the economic answer. If it sees chlorides and temperature, or H₂S, or it is a pressure-containing subsea part where a leak is unacceptable, 2.4856 earns its price. If it must be strong and hot, look at 2.4668 / Alloy 718 instead.
How is 2.4856 forged and heat treated?
Forging 2.4856 is not forging steel with a different chemistry. The alloy has roughly twice the hot flow stress of a carbon steel at the same temperature, the working window is narrow, and it loses heat quickly to the dies because of its low thermal conductivity. That combination drives the whole process plan.
- Billet preparation ESR or VIM+ESR billet, heat number verified by optical emission spectrometry before cutting. Surface conditioned to remove any oxide or seams. A defect on a nickel alloy billet propagates rather than welding shut.
- Soak Charged into a furnace and soaked to 1150–1180 °C. Soak time is generous: the low conductivity means a 300 mm section needs substantially longer than the same steel section to be uniform through the wall.
- Heavy reduction Taken between 1010 °C and 1180 °C. This is where the cast structure is broken down. Reductions are incremental. A single heavy blow on a cold-surfaced nickel billet is how bursts start.
- Reheat cycles The billet returns to the furnace as often as the geometry requires. Nickel alloys generally need more reheats than steel for the same shape, which is a real element of the cost.
- Finish reduction Light finishing passes down to about 930 °C refine the grain. Finishing hot leaves a coarse grain that ultrasonic testing will struggle to penetrate; finishing too cold cracks the part.
- Ring rolling For seamless rolled rings, the pierced blank is rolled radially and axially on a 3 m or 6 m mill, producing continuous circumferential grain flow, which is why a rolled ring outperforms a ring cut from plate.
- Annealing Grade 1 at 871 °C minimum, or Grade 2 solution annealing at 1093 °C minimum, followed by rapid cooling. Rapid cooling is not a detail: slow cooling through 870–650 °C re-precipitates the carbides that annealing just dissolved.
- Testing and release Ultrasonic testing to ASTM A388, EN 10228-3 or SEP 1921; liquid penetrant testing; chemistry and tensile testing; hardness; ASTM G28 intergranular corrosion test where ordered. Certificate issued to EN 10204 3.1 or 3.2.
| Operation | Temperature | Notes |
|---|---|---|
| Soaking / start of forging | 1150–1180 °C | Do not exceed 1180 °C; incipient melting risk at niobium-rich boundaries |
| Heavy reduction | 1010–1180 °C | Breaks down cast structure; incremental passes |
| Light / finishing reduction | 930–1010 °C | Grain refinement; below ~930 °C cracking risk rises sharply |
| Anneal, Grade 1 | 871 °C minimum, typically 925–1010 °C | Rapid cool, water or forced air by section |
| Solution anneal, Grade 2 | 1093 °C minimum, typically 1120–1180 °C | Rapid cool; coarsens the grain on purpose, for creep life |
| Optional stabilisation anneal | 982 °C minimum | After solution annealing, to further resist sensitisation |
| Avoid: slow cooling or holding | 650–870 °C | δ-phase and M₂₃C₆ carbide precipitation; loss of ductility and IGC resistance |
| Not a delivery condition | 550–750 °C ageing | γ″ precipitation raises strength but sits outside ASTM B564; do not specify it |
Welding and machining 2.4856
Welding
2.4856 is one of the most weldable of the corrosion-resistant nickel alloys, which is why the same chemistry dominates weld overlay and dissimilar-metal joints. Use matching filler: ERNiCrMo-3 wire for GTAW, GMAW and SAW, or ENiCrMo-3 covered electrodes for SMAW, per AWS A5.14 and A5.11. No preheat is required and no post-weld heat treatment is needed for corrosion service. Keep interpass temperature below about 150 °C and heat input moderate. The alloy is sensitive to hot cracking if the weld pool is oversized. Clean the joint scrupulously: sulphur and lead from marking pens, grease or shop dirt cause cracking in nickel alloys at levels that carbon steel tolerates without comment.
Machining
2.4856 work-hardens ahead of the cutting edge and conducts heat away from it poorly, so the two failure modes are a glazed, hardened surface and a burnt tool. Practical rules: rigid setup and short tool overhang; sharp positive-rake carbide; low cutting speed with a heavy positive feed; never dwell or let the tool rub; flood or high-pressure through-tool coolant. Take the cut under the previously work-hardened layer rather than skimming it. Where the geometry allows, near-net-shape forging is worth paying for on this alloy. Removing 30–50 % of the machining stock at the press saves more on a nickel alloy part than on any steel part.
What 2.4856 forgings can we supply?
Jiangyin Jiangnan Metal Co., Ltd. produces the following forms in 2.4856 / UNS N06625, made to customer drawing and supplied rough-machined, semi-finished or finish-machined as required.
- Seamless rolled rings
- Contoured rolled rings
- Forged flanges
- Forged shafts
- Forged discs and disks
- Tube sheets
- Sleeves and bushings
- Forged pipes and tubes
- Forged bars, round, flat and square
- Blocks and blanks
- Valve bodies and bonnets
- Valve stems, seat rings, plugs
- Forged nozzles
- Spindles
- Gear blanks
- Wellhead and christmas-tree components
- Near-net-shape forgings to drawing
Production capability and inspection
The factory envelope below is our overall open-die capability. Nickel alloys such as 2.4856 have higher hot strength than steel, so the practical maximum for a given press stroke is smaller than the steel figure. Send the drawing and we will confirm the envelope for your specific part rather than quote a headline number.
- Diameter
- 80–6000mm
- Length
- up to 12000mm
- Single-piece weight
- 10–15000kg
- Ring mills
- 3 m / 6 mradial-axial
- Hydraulic press
- 5000 topen die
- Hammers
- 1·3·5·9 topen die
Equipment
Press and hammers
5,000 tonne open-die hydraulic press; 1, 3, 5 and 9 tonne open-die forging hammers. Multiple reheat furnaces sized for long soak cycles on nickel alloys.
3 m and 6 m mills
Radial-axial ring rolling for seamless and contoured rings, giving continuous circumferential grain flow.
Annealing and solution annealing
Furnaces capable of the 1093 °C minimum solution anneal required for Grade 2, with charts recorded per batch and rapid-quench facilities.
UT, MT, PT
Ultrasonic testing to ASTM A388, EN 10228-3 and SEP 1921; magnetic particle equipment for ferrous grades; liquid penetrant for nickel alloys.
Chemistry and mechanical
Optical emission spectrometer; universal testing machine; impact testing machine; hardness testers; metallographic microscope for grain size and microstructure.
EN 10204 3.1 / 3.2
3.1 mill certificates as standard. 3.2 certificates witnessed by TÜV, DNV, BV, Lloyd's Register or ABS on request, arranged per order.
Where is 2.4856 used?
Subsea and wellhead
Christmas-tree components, wellhead parts, hubs, connectors, valve bodies, seat rings and stems for sour and deepwater service under NACE MR0175 / ISO 15156.
Vessels and exchangers
Tube sheets, flanges, nozzles, pump shafts and impeller hardware for acid, chloride and mixed-service duty; digesters and bleach plant in pulp and paper.
Flue-gas desulphurisation
Absorber internals, reheater components, dampers, ducting hardware and stack liners, where wet acidic chlorides defeat stainless steel.
Seawater systems
Seawater lift pumps, valve trim, propulsion and shipbuilding hardware, desalination plant components.
Hot gas path hardware
Exhaust systems, bellows, thrust-reverser and ducting parts, turbine and compressor casings in the Grade 2 condition.
Reactor and waste handling
Core and internals hardware, reprocessing plant components. Cobalt content is restricted on request for these applications.
Six specification mistakes we see on 2.4856 orders
- Specifying "solution treatment and ageing" 2.4856 is solid-solution strengthened, not precipitation hardened. There is no ageing condition in ASTM B564, and holding the alloy in the ageing range costs ductility. write "ASTM B564 Grade 1, annealed" or "Grade 2, solution annealed at 1093 °C minimum". If you do need an age-hardened nickel alloy, the grade you want is 2.4668 / Alloy 718.
- Ordering by trademark only A purchase order that says only "Inconel 625" names a brand owned by Special Metals Corporation, which narrows your supplier base and can hold up customs and certification paperwork. specify "UNS N06625 / W.Nr. 2.4856 to ASTM B564 Grade 1" and add the trademark in brackets if your drawing history requires it.
- Leaving the grade unstated If no grade is named, Grade 1 is supplied by default. A part destined for 800 °C service then arrives in the wrong condition and creeps in service. always name Grade 1 or Grade 2, and state the design temperature on the order so the supplier can flag a mismatch.
- Quoting a room-temperature yield strength for a hot part Grade 2 cannot meet the Grade 1 yield minimum. That follows directly from its coarser grain. design hot parts against ASME Section II Part D allowables and stress-rupture data, not against room-temperature minima.
- Specifying UT acceptance written for steel A flat-bottom-hole sensitivity that is routine on a fine-grained steel forging may be unachievable in a coarse-grained solution-annealed nickel forging. agree the UT procedure, sensitivity and acceptance class with the manufacturer before production, and record it on the order.
- Forgetting the intergranular corrosion test If a welded or thermally cycled part will see hot acid, grain-boundary carbides matter and no chemistry check will reveal them. add ASTM G28 Method A on the delivered condition as a supplementary requirement when the service is acidic.
How to specify a 2.4856 forging order
- Designation UNS N06625 / W.Nr. 2.4856 / NiCr22Mo9Nb, to ASTM B564 (forgings) or ASTM B446 (bar).
- Grade and condition Grade 1 annealed, or Grade 2 solution annealed at 1093 °C minimum, with or without a stabilisation anneal.
- Form and dimensions Ring, flange, shaft, disc, tube sheet or bar, with finished dimensions, machining allowance and tolerance class. Attach the drawing or 3D model.
- Testing UT to ASTM A388 / EN 10228-3 / SEP 1921 with acceptance class; PT to ASTM E165; ASTM G28 Method A where the service is acidic; Charpy impact if low-temperature toughness is required.
- Certification EN 10204 3.1, or 3.2 with a nominated third party: TÜV, DNV, BV, Lloyd's Register or ABS.
- Service conditions Design temperature and pressure, fluid, chloride level and H₂S partial pressure, so NACE MR0175 / ISO 15156 compliance can be confirmed and stated on the certificate.
- Commercial Quantity, target delivery, Incoterm and destination port. Send it to sales@steelforgepieces.com for a reply within 24 hours.
Drawing callout template
MATERIAL: UNS N06625 / W.Nr. 2.4856 / NiCr22Mo9Nb
SPECIFICATION: ASTM B564 (ASME SB-564 where code work applies)
CONDITION: Grade 1, annealed // or Grade 2, solution annealed 1093 °C min, rapid cooled
MECHANICAL: Rm >= 827 MPa, Rp0.2 >= 414 MPa, A5 >= 30 % (Grade 1)
HARDNESS: <= 35 HRC where NACE MR0175 / ISO 15156-3 applies
NDT: UT per ASTM A388, acceptance class ____
PT per ASTM E165
IGC per ASTM G28 Method A (acidic service only)
CERTIFICATE: EN 10204 3.1 // 3.2 witnessed by ____ on request
MARKING: Heat number, grade, specification, drawing number, low-stress stamp2.4856 forging weight calculator
ExclusiveNet weight at density 8.44 g/cm³. Add machining stock to get the forging weight. The allowance below is a starting point, not a substitute for a process plan.
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- Forging billet, approx.
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Designation lookup
ExclusiveType any name you have on a drawing (2.4856, N06625, NiCr22Mo9Nb, NA 21, NCF 625, GH3625) and confirm whether it is this alloy.
Frequently asked questions about 2.4856
What is material 2.4856?
2.4856 is the EN / DIN material number for NiCr22Mo9Nb, a solid-solution-strengthened nickel-chromium-molybdenum-niobium alloy containing at least 58 % nickel, 20–23 % chromium, 8–10 % molybdenum and 3.15–4.15 % niobium. It is the same chemistry as UNS N06625 and is widely called Alloy 625. Jiangyin Jiangnan Metal Co., Ltd. forges 2.4856 into seamless rolled rings, flanges, shafts, discs, tube sheets and bars to ASTM B564.
Is 2.4856 the same as Inconel 625?
The chemistry and the applicable specifications are the same. Inconel® is a registered trademark of Special Metals Corporation, so material made by that company and sold under that brand is theirs. Material produced by Jiangyin Jiangnan Metal Co., Ltd. is correctly described as UNS N06625 / W.Nr. 2.4856 / NiCr22Mo9Nb to ASTM B564, and is supplied with a multi-designation mill certificate.
What are the equivalent designations of 2.4856?
2.4856 corresponds to UNS N06625 and Alloy 625 in the United States, NiCr22Mo9Nb in Germany, NA 21 in the United Kingdom (BS 3072–3076), NCF 625 in Japan (JIS), NC22DNb in France (AFNOR), and GH3625 / GH625 or NS3306 / NS336 in China (GB).
What is the chemical composition of 2.4856?
Per the EN / VdTÜV limits for NiCr22Mo9Nb: carbon 0.03–0.10 %, silicon 0.50 % max, manganese 0.50 % max, phosphorus 0.020 % max, sulphur 0.015 % max, chromium 20.0–23.0 %, molybdenum 8.0–10.0 %, niobium 3.15–4.15 %, iron 5.0 % max, aluminium 0.40 % max, titanium 0.40 % max, cobalt 1.0 % max, copper 0.50 % max, nickel 58 % minimum. ASTM B564 for UNS N06625 uses the same ranges but sets no minimum carbon and limits phosphorus to 0.015 % max.
What is the difference between Grade 1 and Grade 2 of UNS N06625?
Grade 1 is annealed at 871 °C minimum and is normally used at service temperatures up to 593 °C; its minimum properties are 827 MPa tensile strength, 414 MPa yield strength and 30 % elongation. Grade 2 is solution annealed at 1093 °C minimum for service above 593 °C where creep and rupture resistance govern; its minimum properties are 690 MPa tensile strength, 276 MPa yield strength and 30 % elongation. Grade 2 has a coarser grain size and therefore lower room-temperature strength but far better creep life.
What is the maximum service temperature of 2.4856?
2.4856 retains useful strength from cryogenic temperatures up to about 982 °C in the solution-annealed Grade 2 condition, and resists oxidation to roughly 1050 °C. Grade 1 material is normally limited to 593 °C. Long exposure between about 650 °C and 870 °C precipitates delta phase and carbides that reduce room-temperature ductility, so this band needs a deliberate design decision rather than a default.
Can 2.4856 be used in sour service under NACE MR0175?
Yes. UNS N06625 is listed in NACE MR0175 / ISO 15156-3 for H₂S-containing service in the annealed or solution-annealed condition, with a hardness limit that is commonly stated as 35 HRC. Cold-worked material carries different limits. Jiangyin Jiangnan Metal Co., Ltd. supplies a NACE compliance statement on the mill certificate when sour-service conditions are declared on the order.
Is 2.4856 magnetic?
No. 2.4856 has an austenitic face-centred-cubic structure with a Curie temperature below −196 °C, and its relative magnetic permeability is approximately 1.0006 at room temperature, so it is treated as non-magnetic.
What is the density of 2.4856?
The density of 2.4856 / UNS N06625 is 8.44 g/cm³, equivalent to 0.305 lb/in³. Use this value when converting a forging drawing volume into billet weight. The weight calculator above does it for you.
Does 2.4856 need an ageing heat treatment?
No. 2.4856 is strengthened by solid solution, mainly by molybdenum and niobium, not by precipitation hardening. ASTM B564 recognises only the annealed and solution-annealed conditions. Holding the alloy in the 550–750 °C range does precipitate γ″ and will raise strength, but it lowers ductility and toughness and is not a specified delivery condition.
What is the forging temperature range for 2.4856?
Heavy reductions are made between about 1010 °C and 1180 °C. Light finishing reductions can be taken down to roughly 930 °C, which refines the grain. The alloy has high hot strength, so a 2.4856 forging needs more press capacity and more reheats than the same shape in carbon or alloy steel, and it must be annealed or solution annealed after forging.
How large a 2.4856 forging can Jiangyin Jiangnan Metal produce?
Jiangyin Jiangnan Metal Co., Ltd. produces forgings from 80 mm to 6,000 mm in diameter, up to 12,000 mm in length and from 10 kg to 15,000 kg in single-piece weight, using 1, 3, 5 and 9 tonne open-die hammers, a 5,000 tonne hydraulic press and 3 metre and 6 metre seamless ring rolling mills. The practical maximum size for nickel alloys such as 2.4856 is lower than for carbon steel because of the higher hot strength, so confirm the envelope for your specific part.
Can 2.4856 be welded?
Yes. 2.4856 is readily welded by GTAW, GMAW, SMAW and SAW using matching ERNiCrMo-3 filler or ENiCrMo-3 electrodes. No post-weld heat treatment is required for corrosion service. The same filler is widely used for dissimilar joints and for weld overlay on carbon steel.
What certification is supplied with 2.4856 forgings?
Every 2.4856 forging is supplied with an EN 10204 3.1 mill certificate as standard, listing heat number, full chemistry, mechanical test results, heat-treatment records and NDT results. EN 10204 3.2 certificates witnessed by a nominated third party such as TÜV, DNV, BV, Lloyd's Register or ABS are available on request.
Glossary
- 2.4856
- EN / DIN material number for the nickel-chromium-molybdenum-niobium alloy NiCr22Mo9Nb; identical chemistry to UNS N06625.
- NiCr22Mo9Nb
- EN chemical designation naming the principal alloying elements: nominally 22 % chromium, 9 % molybdenum, with niobium.
- UNS N06625
- Unified Numbering System designation, the neutral international identifier for this alloy.
- Grade 1 / Grade 2
- The two ASTM heat-treated conditions for N06625: annealed at 871 °C minimum, and solution annealed at 1093 °C minimum.
- Solid-solution strengthening
- Strength derived from alloying atoms dissolved in the matrix, here mainly molybdenum and niobium, rather than from precipitates. It is why 2.4856 is not aged.
- γ″ (gamma double prime)
- A metastable Ni₃Nb precipitate that forms roughly between 550 °C and 750 °C. It strengthens the alloy but costs ductility; it is the hardening phase of Alloy 718, not a delivery condition for 2.4856.
- δ-phase (delta)
- The stable orthorhombic Ni₃Nb phase that forms on grain boundaries with long exposure around 650–870 °C, reducing toughness.
- PREN
- Pitting Resistance Equivalent Number, %Cr + 3.3 × %Mo (+ 16 × %N). Roughly 51 for 2.4856; values above about 40 are the usual threshold for ambient seawater service.
- Sensitisation
- Chromium depletion next to grain-boundary carbides, which opens the boundary to intergranular attack. Niobium ties up carbon as NbC and largely prevents it in 2.4856.
- ESR
- Electroslag remelting, a secondary melting route that reduces segregation and inclusions. Standard practice for heavy 2.4856 forging billet.
- ERNiCrMo-3
- AWS A5.14 filler-wire classification matching this alloy; the corresponding covered electrode is ENiCrMo-3.
- EN 10204 3.1 / 3.2
- Inspection certificate types: 3.1 is issued by the manufacturer's independent inspection department; 3.2 is countersigned by a nominated third party.
- ASTM G28 Method A
- A boiling ferric-sulphate / sulphuric-acid test that reveals intergranular attack caused by grain-boundary carbides.
- NACE MR0175 / ISO 15156
- The materials standard governing metals used in H₂S-containing oil and gas production. N06625 is listed for sour service in the annealed and solution-annealed conditions.
Technical references
Chemistry, mechanical, physical and heat-treatment data on this page are drawn from the published standards and reference works listed below. Values reported on our mill certificates are independent test results traceable to calibrated equipment.
- ASTM B564-22, Standard Specification for Nickel Alloy Forgings, ASTM International, West Conshohocken, PA.
- ASTM B446-19, Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy (UNS N06625) Rod, Bar and Wire, ASTM International.
- ASTM B443-19, Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy Plate, Sheet and Strip, ASTM International.
- ASTM B444-18, Standard Specification for Nickel-Chromium-Molybdenum-Columbium Alloy Pipe and Tube, ASTM International.
- ASME Boiler and Pressure Vessel Code, Section II Part B (SB-564, SB-446) and Part D (allowable stresses), ASME.
- EN 10302, Creep resisting steels, nickel and cobalt alloys, CEN, Brussels.
- DIN 17744, Wrought nickel alloys with molybdenum and chromium, DIN.
- VdTÜV Werkstoffblatt 499, NiCr22Mo9Nb.
- NACE MR0175 / ISO 15156-3, Petroleum and natural gas industries — Materials for use in H₂S-containing environments — Part 3: Cracking-resistant CRAs and other alloys, ISO.
- ASM Handbook, Volume 2, Properties and Selection: Nonferrous Alloys and Special-Purpose Materials, ASM International.
- ASM Handbook, Volume 14A, Metalworking: Bulk Forming, ASM International.
- AWS A5.14 / A5.11, filler metal specifications for nickel and nickel-alloy welding consumables, American Welding Society.
- ASTM A388-19, Standard Practice for Ultrasonic Examination of Steel Forgings; EN 10228-3; SEP 1921.
- ASTM G28-02, Standard Test Methods for Detecting Susceptibility to Intergranular Corrosion in Wrought Nickel-Rich Chromium-Bearing Alloys, ASTM International.
Standard revisions cited are those current at the last review of this page. For contract purposes, always reference the revision in force at the order date.
About the manufacturer
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory located at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. The company operates open-die forging hammers from 1 to 9 tonnes, a 5,000 tonne open-die hydraulic press, and 3 metre and 6 metre seamless ring rolling mills, and employs approximately 460 people including 9 senior engineers and 32 intermediate engineers. Production covers carbon steel, alloy steel, tool steel, stainless steel and nickel alloys, with in-house raw-material control, forging, heat treatment, machining and testing. Quality management is certified to ISO 9001:2015, and material is supplied with EN 10204 3.1 certificates as standard or 3.2 third-party witnessed certificates on request.
Citing this page
This page is maintained as a technical reference. If you are quoting it in a specification, report, please attribute it as follows.
Jiangyin Jiangnan Metal Co., Ltd. (2026). "2.4856 Forgings — NiCr22Mo9Nb / UNS N06625 / Alloy 625."
Jiangyin, Jiangsu, China. Last updated 10 August 2026.
https://www.steelforgepieces.com/Nickel-Alloy/2.4856.html
Source of record: Jiangyin Jiangnan Metal Co., Ltd., No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China · Tel 0086-189-2135-9659 · sales@steelforgepieces.com
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Send the drawing, the grade condition (ASTM B564 Grade 1 or Grade 2), the testing and certification you need, and the quantity. We reply within 24 hours with price, lead time and confirmation of the applicable standards. If the specification is ambiguous, we will say so before quoting rather than after delivery.
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Jiangyin Jiangnan Metal Co., Ltd., Open-Die Forging Factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel 0086-189-2135-9659 ·
Email sales@steelforgepieces.com ·
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