Inconel 625LCF at a glance
- Grade
- Inconel 625LCF (also written alloy 625LCF, 625 LCF)
- UNS number
- N06626
- Werkstoff / DIN
- 2.4856 / NiCr22Mo9Nb
- Alloy family
- Nickel-chromium-molybdenum-niobium, solid-solution strengthened, austenitic, non-magnetic
- Defining control
- C ≤ 0.03 %, Si ≤ 0.15 %, N ≤ 0.02 %, grain size ASTM No. 5 or finer
- Forging standard
- ASTM B564 / ASME SB-564
- Sheet and strip standard
- SAE AMS 5879, also meets ASTM B443 Grade 1
- Delivery condition
- Solution annealed, rapid cooled. Not aged.
- Fatigue service range
- Cryogenic to 650 °C (1200 °F) in cyclic duty
- Density
- 8.44 g/cm³ (0.305 lb/in³)
- Melting range
- 1290–1350 °C (2350–2460 °F)
- Certification
- EN 10204 3.1 or 3.2 (third-party witnessed)
- Forged by
- Jiangyin Jiangnan Metal Co., Ltd., Jiangyin, Jiangsu, China
What Inconel 625LCF is, and when to specify it
Specify 625LCF when the failure mode is fatigue. Where the duty is steady and the concern is corrosion or temperature, standard alloy 625 does the same job for less money.
Alloy 625 is a solid-solution strengthened nickel-chromium alloy. Its strength comes from molybdenum and niobium held in solution rather than from heat treatment. It serves from cryogenic temperatures to about 980 °C and is close to immune to chloride stress-corrosion cracking. In steady service it is one of the more dependable corrosion-resistant alloys available.
Under repeated strain the governing factor is different. Carbides and nitrides formed by carbon, silicon and nitrogen are hard, brittle and poorly bonded to the matrix around them. Each particle raises the local stress. In cyclic loading, cracks start at those particles well before the bulk material comes near its tensile limit.
Alloy 625LCF deals with that. Melting practice and chemistry are controlled to keep carbon, silicon and nitrogen well below the alloy 625 ceilings, and the thermomechanical processing holds a fine, uniform grain size of ASTM No. 5 or finer. Fewer particles mean fewer crack initiation sites. Finer grain means more grain boundaries to arrest the cracks that do form. Thermal fatigue improves for the same reason, since thermal cycling is strain cycling driven by differential expansion.
The alloy is not stronger and not more corrosion resistant than 625. Annealed tensile and yield strength are much the same, and corrosion behaviour is the same. The gain is in cyclic life. It costs more than standard 625, so it is worth specifying only where cyclic strain governs the design.
A note on product form. Alloy 625LCF was developed as a sheet and strip product for metal bellows, and SAE AMS 5879 is written for that form. The chemistry can be forged and we forge it, but the reason for ordering it matters. The common reason is assembly consistency: where the bellows itself is 625LCF, ordering the end collars, weld rings and flanges in the same controlled chemistry keeps weld metal composition and thermal expansion matched across the joint. Where the fatigue requirement applies only to the convolutions, standard alloy 625 forgings to ASTM B564 are usually the better commercial choice for the mating hardware. We will say so on the quotation.
Chemical composition of Inconel 625LCF (UNS N06626)
Composition limits are in weight percent. The three highlighted rows are the controls that separate 625LCF from standard alloy 625. Everything else is common to both grades.
| Element | 625LCF min | 625LCF max | Alloy 625 max | Role in the alloy |
|---|---|---|---|---|
| Nickel (Ni) | 58.0 | balance | 58.0 min | Base element. Austenitic matrix, resistance to chloride stress-corrosion cracking |
| Chromium (Cr) | 20.0 | 23.0 | 20.0–23.0 | Protective oxide film against oxidising media and high-temperature oxidation |
| Molybdenum (Mo) | 8.0 | 10.0 | 8.0–10.0 | Solid-solution strengthening, pitting and crevice corrosion resistance |
| Niobium + Tantalum (Nb+Ta) | 3.15 | 4.15 | 3.15–4.15 | Solid-solution and precipitation strengthening, stabilises against sensitisation |
| Iron (Fe) | — | 5.0 | 5.0 | Residual from raw materials, kept low to preserve corrosion resistance |
| Carbon (C) | — | 0.03 | 0.10 | Fatigue control. Low carbon suppresses carbides that nucleate fatigue cracks |
| Silicon (Si) | — | 0.15 | 0.50 | Fatigue control. Restricted to limit silicide and inclusion formation |
| Nitrogen (N) | — | 0.02 | not specified | Fatigue control. Low nitrogen suppresses embrittling nitride particles |
| Manganese (Mn) | — | 0.50 | 0.50 | Deoxidiser, combines with residual sulfur |
| Aluminium (Al) | — | 0.40 | 0.40 | Deoxidiser, minor contribution to high-temperature stability |
| Titanium (Ti) | — | 0.40 | 0.40 | Ties up carbon and nitrogen |
| Cobalt (Co) | — | 1.0 | 1.0 | Residual limit, restricted further for nuclear service |
| Phosphorus (P) | — | 0.015 | 0.015 | Kept low for hot workability and weldability |
| Sulfur (S) | — | 0.015 | 0.015 | Kept low for hot workability and toughness |
Every 625LCF limit sits inside the corresponding alloy 625 limit, so a 625LCF heat also satisfies UNS N06625. The reverse is not true. Dual N06625 / N06626 certification is normal practice and lets one forging serve both callouts on a drawing.
Mechanical properties of Inconel 625LCF forgings
Specified minimums, annealed condition
These are the values a mill certificate has to meet for annealed material to ASTM B564 / B443 Grade 1. They are minimums, not typical values, and they are the numbers to write on a purchase order.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength, min | 690 MPa | 100 ksi |
| Yield strength 0.2 % offset, min | 276 MPa | 40 ksi |
| Elongation in 50 mm (2 in), min | 30 % | 30 % |
| Average grain size | ASTM No. 5 or finer | ASTM No. 5 or finer |
Grade 2 material (solution annealed at higher temperature, for service above 540 °C where creep governs) carries lower specified minimums of 620 MPa tensile and 241 MPa yield. State Grade 1 or Grade 2 on the order. For 625LCF fatigue duty, Grade 1 annealed is normally correct.
Typical as-delivered values
Annealed 625LCF normally tests well above the specified minimums. The values below are representative of production material and vary with section size, reduction ratio and cooling rate.
| Property | Metric | Imperial |
|---|---|---|
| Tensile strength | 770 MPa | 111,600 psi |
| Yield strength, 0.2 % offset | 319 MPa | 46,300 psi |
| Elongation at break | 63 % | 63 % |
| Modulus of elasticity | 208 GPa | 30,200 ksi |
| Shear modulus | 81.4 GPa | 11,800 ksi |
| Poisson's ratio | 0.28 | 0.28 |
| Hardness, Rockwell B | 84 HRB | 84 HRB |
Typical values are for design screening only. The mill test certificate issued with each forging governs acceptance. Yield strength is low relative to tensile because annealed 625LCF work-hardens steeply, which is what allows it to be formed into deep bellows convolutions.
Physical properties of Inconel 625LCF
Physical properties are the same as alloy 625, since the two share a base chemistry.
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.44 g/cm³ | 0.305 lb/in³ |
| Melting range | 1290–1350 °C | 2350–2460 °F |
| Specific heat, 20 °C | 410 J/kg·K | 0.098 Btu/lb·°F |
| Thermal conductivity, 20 °C | 9.8 W/m·K | 68 Btu·in/ft²·h·°F |
| Mean expansion, 20–100 °C | 12.8 µm/m·K | 7.1 × 10⁻⁶ in/in·°F |
| Electrical resistivity | 1.29 µΩ·m | 776 Ω·circ mil/ft |
| Magnetic permeability, 200 Oe | 1.0006 | essentially non-magnetic |
| Curie temperature | below −196 °C | below −320 °F |
Inconel 625 vs 625LCF: how to choose
The two grades are routinely confused on drawings and purchase orders, partly because they share a Werkstoff number. They differ in three things: residual element limits, melting and processing control, and grain size requirement. Nickel, chromium, molybdenum and niobium content and corrosion behaviour are the same.
| Criterion | Inconel 625 | Inconel 625LCF |
|---|---|---|
| UNS number | N06625 | N06626 |
| Werkstoff Nr. | 2.4856 | 2.4856 |
| Carbon, max % | 0.10 | 0.03 |
| Silicon, max % | 0.50 | 0.15 |
| Nitrogen, max % | not specified | 0.02 |
| Grain size requirement | none specified | ASTM No. 5 or finer |
| Melting practice | EAF + AOD/VOD, ESR or VAR optional | Closely controlled, VIM or VOD + ESR to hold C, Si, N |
| Low-cycle fatigue life | baseline | longer in cyclic bellows service |
| Corrosion resistance | the same | |
| Tensile and yield strength | much the same in the annealed condition | |
| Primary specification | ASTM B564 (forgings), B443, B446, AMS 5599 / 5666 | SAE AMS 5879 (sheet and strip), ASTM B443 Gr 1, B564 for forgings |
| Relative cost | baseline | higher, from restricted melting and processing |
| Choose it when | Service is steady, or governed by corrosion, or by strength at temperature | The part is strain-cycled or thermally cycled and would fail by fatigue |
If the drawing states a fatigue life in cycles, specify 625LCF (UNS N06626) and ask for grain size on the certificate. If it states a corrosion environment or a design temperature, standard alloy 625 (UNS N06625) to ASTM B564 is enough and costs less.
Inconel 625LCF equivalent designations
| System | Designation |
|---|---|
| UNS (USA) | N06626 |
| Werkstoff Nr. (Germany) | 2.4856 |
| DIN / EN name | NiCr22Mo9Nb |
| SAE / AMS | AMS 5879 (sheet and strip, LCF properties), AMS 5599 (625 sheet, plate, strip) |
| ASTM / ASME | ASTM B443 Grade 1 / ASME SB-443 Grade 1, ASTM B564 / ASME SB-564 for forgings |
| ASME pressure design | Code Case 2276, Section VIII Division 1, to 427 °C (800 °F) |
| Sour service | NACE MR0175 / ISO 15156, NACE MR0103 |
| Trade names | INCONEL alloy 625LCF, Nicrofer 6020 hMo (625 family), Chronin 625 |
Where a code case or design registration is involved, order to the UNS number rather than the trade name and check the equivalence against the mill certificate. INCONEL and 625LCF are registered trademarks of Special Metals Corporation. Jiangyin Jiangnan Metal Co., Ltd. is not affiliated with, sponsored by or endorsed by the trademark holder, and the names are used here only to identify the material specification. Material we produce is correctly described as UNS N06626 / W.Nr. 2.4856.
Applicable standards by product form
| Product form | ASTM | ASME | AMS |
|---|---|---|---|
| Forgings (our core product) | B564 | SB-564 | 5666 (bar, forgings) |
| Plate, sheet and strip | B443 Gr 1 | SB-443 Gr 1 | 5879 (LCF), 5599 |
| Rod, bar and wire | B446 | SB-446 | 5666 |
| Seamless pipe and tube | B444 | SB-444 | — |
| Welded pipe | B705 | SB-705 | — |
| Welded tube | B704 | SB-704 | — |
| Fittings | B366 | SB-366 | — |
| Welding filler | AWS A5.14 ERNiCrMo-3, A5.11 ENiCrMo-3 | SFA-5.14 / SFA-5.11 | 5837 |
AMS 5879 is the specification written to capture the fatigue strength of alloy 625LCF, and it applies to sheet and strip. There is no separate LCF forging standard, so the normal ordering practice is ASTM B564 with UNS N06626 chemistry and the ASTM No. 5 grain size requirement stated on the purchase order. We confirm this wording on the quotation.
Inconel 625LCF forgings we produce
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory. Every item below is forged to the customer's drawing or dimensional sketch. There is no fixed catalogue and no tooling charge for open-die work.
Size and weight capability
| Product form | Dimensional range | Unit weight |
|---|---|---|
| Seamless rolled rings | OD 200–3,000 mm, height to 800 mm | 20–8,000 kg |
| Round bars | Ø80–800 mm, length to 6,000 mm | 20–6,000 kg |
| Discs, tube sheets | Ø200–2,500 mm, thickness to 600 mm | 30–10,000 kg |
| Shafts, sleeves, blocks | to 6,000 mm long | to 10,000 kg |
Machining allowance is normally 6–20 mm per surface depending on section size, unless your drawing states otherwise. We also supply finish-machined parts to print.
How we make Inconel 625LCF forgings
- MeltingThe heat is produced by EAF + AOD/VOD with ESR remelting, or by VIM + ESR where the specification demands the tighter carbon, silicon and nitrogen control that defines the LCF grade. Melting practice is the first place 625LCF diverges from standard 625.
- Heat verificationChemistry is confirmed by spectrometer against the UNS N06626 limits before any material is heated, with attention to the 0.03 % C, 0.15 % Si and 0.02 % N ceilings.
- Open-die forgingForged on hydraulic presses and hammers at 1010–1180 °C with a controlled reduction ratio to close porosity and develop wrought grain flow following the part contour. Finish forging temperature is held down to avoid grain growth. Rings are ring-rolled seamless.
- Solution annealingHeld at roughly 1093–1150 °C, then rapidly cooled, to dissolve carbides and retain the fine grain structure. 625LCF is not aged. Ageing would raise strength but cut ductility and fatigue life, which works against the reason for using the grade.
- Rough or finish machiningTurned, bored, drilled and faced to your drawing, with agreed machining allowance or to final dimensions.
- Non-destructive testingUltrasonic examination to EN 10228-3, SEP 1921, ASTM A388 or your nominated class. Liquid penetrant, grain size determination per ASTM E112 and dimensional inspection as required.
- Certification and despatchEN 10204 3.1 mill certificate as standard, 3.2 with third-party witness (TÜV, BV, LR, SGS, DNV) on request. Marked, preserved and packed for sea or air freight.
Where Inconel 625LCF is used
| Industry | Components in Inconel 625LCF |
|---|---|
| Automotive | Flexible exhaust couplings and decoupler bellows, turbocharger connections, EGR components. This is the highest-volume use of the grade. |
| Aerospace | Aircraft ducting, engine exhaust and containment components, bleed-air bellows, flexible joints in high-temperature ducting |
| Chemical and petrochemical | Expansion joints in process and transport piping, bellows-sealed valves, diaphragms and seals, forged end collars and weld rings for bellows assemblies |
| Power generation | Expansion joints in flue gas and steam lines, pressure-retaining parts under thermal cycling, exhaust duct hardware |
| Marine and offshore | Bellows for marine service, seawater-exposed flexible joints, subsea equipment components under chloride attack and cyclic load |
| Pressure vessels and heat exchangers | Forged tube sheets, shell flanges and girth rings where the equipment sees repeated thermal cycling rather than steady service |
| Oil and gas | Wellhead and Christmas tree components, bellows-sealed instrumentation, sour service parts to NACE MR0175 / ISO 15156 |
In each case the part is strain-cycled or thermally cycled in a corrosive environment. Alloy 625LCF is used where a standard 625 component would survive the chemistry but fail on cycles.
Testing, inspection and certification
- Chemical analysis. Spectrometric heat analysis and, on request, product analysis on the finished forging. Carbon, silicon and nitrogen are reported separately on 625LCF orders.
- Mechanical testing. Room-temperature tensile, yield and elongation per ASTM B564. Elevated-temperature tensile and impact testing to your specification.
- Grain size. Determined per ASTM E112. ASTM No. 5 or finer is the requirement that makes the material 625LCF rather than 625, so ask for it on the certificate.
- Fatigue testing. Low-cycle fatigue testing to an agreed strain range and cycle count, by an accredited laboratory, where the contract calls for it.
- Ultrasonic testing. EN 10228-3, SEP 1921 Class C/D/E, ASTM A388 or customer class.
- Surface NDT. Liquid penetrant examination per ASTM E165 / ASME V Article 6.
- Intergranular corrosion. ASTM G28 method A, or ASTM A262 practice as agreed.
- Certification. EN 10204 3.1 as standard. EN 10204 3.2 witnessed by TÜV, BV, LR, SGS or DNV on request. Full heat traceability and hard stamping.
Frequently asked questions about Inconel 625LCF
What is Inconel 625LCF?
Inconel 625LCF (UNS N06626, W.Nr. 2.4856) is the low-cycle-fatigue, bellows-quality version of nickel alloy 625. It has the same nickel-chromium-molybdenum-niobium chemistry as alloy 625, but carbon is held to 0.03 % maximum, silicon to 0.15 % maximum and nitrogen to 0.02 % maximum, and the material is processed to a fine grain size of ASTM No. 5 or finer. These limits suppress the carbides and nitrides that start fatigue cracks. The alloy resists low-cycle and thermal fatigue up to about 650 °C (1200 °F) and keeps the corrosion resistance of standard 625.
What is the difference between Inconel 625 and Inconel 625LCF?
The base chemistry is the same. The differences are the residual element limits, the melting practice and the grain size. Alloy 625 allows up to 0.10 % carbon and 0.50 % silicon and specifies neither nitrogen nor grain size. Alloy 625LCF caps carbon at 0.03 %, silicon at 0.15 % and nitrogen at 0.02 %, and requires an average grain size of ASTM No. 5 or finer. Fewer particles to start fatigue cracks means a longer low-cycle fatigue life in cyclic service. Corrosion resistance, density and annealed strength are much the same. Every 625LCF limit sits inside the 625 limit, so a 625LCF heat also meets UNS N06625.
What is the UNS number for Inconel 625LCF?
Inconel 625LCF is UNS N06626. The Werkstoff number is 2.4856, shared with alloy 625. Standard Inconel 625 is UNS N06625. State UNS N06626 together with the product standard, ASTM B564 for forgings or SAE AMS 5879 for bellows sheet and strip, so the low-cycle-fatigue requirement is clear on the purchase order.
Which standards cover Inconel 625LCF?
SAE AMS 5879 is written for the fatigue properties of alloy 625LCF sheet and strip. The material also meets ASTM B443 Grade 1 and ASME SB-443 Grade 1. Forgings are ordered to ASTM B564 / ASME SB-564, bar to ASTM B446, and seamless pipe and tube to ASTM B444. For pressure design, ASME Code Case 2276 gives allowable stresses for 625LCF in Section VIII Division 1 construction up to 427 °C (800 °F). NACE MR0175 / ISO 15156 and NACE MR0103 apply for sour service.
Can Inconel 625LCF be supplied as forgings and not only as bellows sheet?
Yes. The grade was developed for thin bellows sheet and strip and AMS 5879 covers that form, but the chemistry can be forged and we forge it into rings, flanges, bars, discs, shafts, sleeves, bushings and tube sheets to customer drawings. The usual reason to order forgings in 625LCF is assembly consistency, keeping the end collars, weld rings and flanges welded to a 625LCF bellows in the same controlled chemistry so weld metal and thermal expansion match. Where the fatigue requirement applies only to the convolutions, standard alloy 625 forgings to ASTM B564 are usually the better commercial choice for the mating hardware.
What heat treatment is used for Inconel 625LCF forgings?
Solution annealing at roughly 1093–1150 °C (2000–2100 °F) followed by rapid cooling. Alloy 625LCF is solid-solution strengthened and is not aged for fatigue service. Ageing raises strength but lowers ductility and shortens low-cycle fatigue life, which works against the reason for using the grade. Annealed material is also the condition assumed by AMS 5879 and by the allowable stresses of ASME Code Case 2276.
Can Inconel 625LCF be welded?
Yes. Thin bellows material is normally joined without filler metal by gas tungsten arc welding (GTAW) or plasma arc welding. For heavier sections, matching filler such as ERNiCrMo-3 (AWS A5.14) or coated electrode ENiCrMo-3 (AWS A5.11) is used. Post-weld heat treatment is not normally required for the alloy itself, although the design code may call for it. Keep interpass temperature low and heat input controlled so the fine grain size is not lost in the heat affected zone.
What is Inconel 625LCF used for?
Metal bellows and expansion joints are the main application: automotive flexible exhaust couplings, aircraft ducting and exhaust components, expansion joints in process and transport piping, and bellows for marine service. It is also used for chemical and petrochemical expansion joints, seals and diaphragms, and for pressure-retaining parts that see repeated thermal cycling. Any part loaded cyclically at elevated temperature that would otherwise fail by fatigue rather than by corrosion or creep is a candidate.
What sizes of Inconel 625LCF forgings can you supply?
Seamless rolled rings from 200 to 3,000 mm outside diameter, round bars 80 to 800 mm diameter up to 6,000 mm long, discs and tube sheets to 2,500 mm diameter and 600 mm thick, and shafts, sleeves and blocks up to 6,000 mm long, with single-piece weights up to about 10,000 kg. Everything is forged to the customer drawing or dimensional sketch. Open-die forging needs no dies, so there is no tooling charge and no minimum order quantity by piece, and one-off or prototype parts are economic.
Do you supply a material certificate with Inconel 625LCF forgings?
Every forging ships with an EN 10204 3.1 mill test certificate as standard, showing heat number, chemical analysis, mechanical results, grain size, heat treatment record and NDT results. EN 10204 3.2 certification witnessed by a third party such as TÜV, BV, LR, SGS or DNV is available on request at the time of order, with full heat traceability and hard stamping.
How long does an Inconel 625LCF forging take to produce?
Lead time depends on whether the grade is in raw stock and on the size of the forging. Simple rings and discs from stock material typically run 25 to 40 days. Parts needing a new melt, ESR remelting, heavy machining, fatigue testing or third-party witnessed inspection take longer. Send your drawing and we will confirm a firm date with the quotation.
Who supplies open-die forged Inconel 625LCF parts in China?
Jiangyin Jiangnan Metal Co., Ltd. is an open-die forging factory at No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China. It forges Inconel 625LCF (UNS N06626) and other nickel alloys, stainless steels, tool steels, alloy steels and carbon steels into seamless rolled rings, flanges, round bars, discs, shafts, sleeves, bushings and tube sheets, and exports worldwide. Enquiries: sales@steelforgepieces.com or +86 189 2135 9659.
Request a quotation for Inconel 625LCF forgings
Send a drawing, a sketch, or just the dimensions and quantity. We quote open-die forgings in Inconel 625LCF with no tooling charge and no piece minimum.
Useful details if you have them: grade and standard (Inconel 625LCF / UNS N06626 / ASTM B564), product form, dimensions with machining allowance, quantity, delivery condition, grain size requirement, NDT class, certificate type (EN 10204 3.1 or 3.2) and required delivery date.
- Company
- Jiangyin Jiangnan Metal Co., Ltd.
- Business
- Open-die forging factory
- Address
- No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
- Telephone and WhatsApp
- +86 189 2135 9659
- Website
- www.steelforgepieces.com