Inconel 625 Pipe & Tube (UNS N06625, Seamless & Welded, ASTM B444 / B829)
| Share | |
|---|---|
| Categories | Alloy Steel |
| Brand | MESCO: Trusted Steel Wholesale Manufacturer |
| Product Category | Nickel-chromium-molybdenum alloy pipe and tube |
| Grade / UNS | Inconel 625 / UNS N06625 / W.Nr 2.4856 |
| Product Form | Seamless pipe, welded pipe, seamless tube, welded tube, U-bend tube |
| Outside Diameter | 1.58 mm to 168 mm (38 stock series) |
| Wall Thickness | 0.29 mm to 24 mm |
| Stocked Size Combinations | 235 |
| Delivery Condition | Solution annealed; pickled, bright annealed or polished on request |
| Surface Finish | Pickled and annealed / bright annealed / polished |
| Standards | ASTM B444, B704, B705, B829 / ASME SB444, SB704, SB705 |
| Sour Service | NACE MR0175 / ISO 15156 on request |
| Length | Random length, fixed length and cut-to-size to order |
| Origin | China (MESCO STEEL) |
Inconel 625 Pipe & Tube (UNS N06625)
Seamless and welded pipe and tube in Inconel 625 — the nickel-chromium-molybdenum alloy with a niobium addition that delivers high strength and outstanding corrosion resistance without relying on precipitation hardening. MESCO supplies a stocked range of 235 size combinations across 38 outside-diameter series, from 1.58 mm capillary up to 168 mm pipe, in wall thicknesses from 0.29 mm to 24 mm.
- 235 stocked sizes · 1.58–168 mm OD · 0.29–24 mm wall
- Seamless and welded, cold-drawn and hot-finished forms
- ASTM B444 / B704 / B705 / B829 · UNS N06625 · W.Nr 2.4856
Overview
Inconel 625 pipe and tube is specified where a component has to survive hot, wet and chloride-bearing service at the same time. The alloy is a solid-solution-strengthened nickel alloy: molybdenum and niobium are held in solution to stiffen the lattice, so the tube carries useful strength from cryogenic temperatures up to roughly 980 °C without a heat-treatment step that could be disturbed by welding. That single characteristic — strength that does not depend on a critical ageing cycle — is why fabricators specify 625 for welded assemblies rather than an age-hardenable alternative.
In practice the demand comes from two directions. Process engineers use it for heat exchanger tubes, reactor internals, transfer lines and scrubber ducting where chlorides, seawater, organic acids or high-temperature flue gas would attack a stainless grade. Mechanical and aerospace engineers use it where a thin-wall tube must keep fatigue and creep strength at temperature. The same tube serves both, and MESCO supplies it cut to the exact outside diameter and wall thickness the drawing calls for.
What Is Inconel 625 Pipe and Tube?
Inconel 625 is a nickel-based superalloy designated UNS N06625 and Werkstoff number 2.4856, also marketed as Alloy 625, DIN 2.4856, BS NA21 and JIS NCF 625. It is not a stainless steel: nickel is the base element at 58 % or more, and the corrosion resistance comes from the combination of chromium for passive-film formation, molybdenum for resistance to pitting and crevice attack, and niobium plus tantalum for strength by solid-solution and carbide effects.
Pipe and tube are produced in two families. Seamless product is pierced, hot-finished or cold-drawn from a billet with no longitudinal joint, which removes the weld as a corrosion or inspection variable — the usual choice for exchanger tubes and high-pressure lines. Welded product is formed from strip and welded, then cold-drawn or rolled to finished dimensions; it offers lower cost and better availability in thin walls. MESCO supplies both and will state the manufacturing route on the mill certificate so that the purchasing specification can be matched exactly.
| Element | Composition | Element | Composition |
|---|---|---|---|
| Nickel (Ni) | 58.0 min, balance | Manganese (Mn) | 0.50 max |
| Chromium (Cr) | 20.0 – 23.0 | Silicon (Si) | 0.50 max |
| Molybdenum (Mo) | 8.0 – 10.0 | Aluminium (Al) | 0.40 max |
| Niobium + Tantalum (Nb+Ta) | 3.15 – 4.15 | Titanium (Ti) | 0.40 max |
| Iron (Fe) | 5.0 max | Cobalt (Co) | 1.0 max |
| Carbon (C) | 0.10 max | Phosphorus (P) | 0.015 max |
| Sulphur (S) | 0.015 max | — | — |
Size Range and Stocked Dimensions
The table below is the current MESCO stock list for Inconel 625 pipe and tube, given as outside diameter against available wall thickness. Both series are represented: the small imperial instrument-tubing diameters (1/16 in. through 1 in., shown here in millimetres) and the larger metric and nominal-bore pipe diameters. Dimensions outside this range can be produced to order — give us the outside diameter, wall thickness, length and quantity and we will confirm feasibility and lead time.
| Outside diameter (mm) | Available wall thickness (mm) |
|---|---|
| 1.58 | 0.29 |
| 3 | 0.5 |
| 3.175 | 0.5 |
| 4 | 1 |
| 5 | 1 |
| 6 | 0.89, 1, 1.24, 1.5, 2 |
| 6.35 | 0.89, 1.24, 1.65, 2 |
| 8 | 0.8, 1, 1.5, 2 |
| 9.53 | 0.89, 1.24, 1.65, 2 |
| 10 | 1, 1.5, 2, 2.5, 3 |
| 11 | 0.5 |
| 12 | 1, 1.5, 2, 2.5, 3 |
| 12.7 | 1.24, 1.65, 2 |
| 14 | 1, 1.5, 2, 2.5, 3 |
| 14.33 | 2.53 |
| 15 | 2 |
| 16 | 1, 1.5, 2, 2.5 |
| 21.3 | 3, 3.5, 4, 5, 5.5, 6 |
| 22 | 1.5, 2, 2.77, 3, 3.5, 4, 4.5, 5, 5.5, 6 |
| 25 | 1.24 |
| 25 × 25 | 1.65, 2, 2.5, 2.77, 3, 3.5, 4, 4.5, 5, 5.5, 6 |
| 25.4 | 1.24, 1.65, 2, 2.5, 2.77, 3, 3.5, 4, 4.5, 5, 5.5, 6 |
| 26.7 | 2.87, 3, 3.91, 4, 4.5, 5, 5.5 |
| 38 | 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8 |
| 42 | 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8 |
| 45 | 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8 |
| 48 | 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8 |
| 48.3 | 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 8 |
| 50 | 5 |
| 65 | 4, 4.5, 5, 5.5, 6, 8, 10, 12 |
| 73 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12 |
| 76 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12 |
| 89 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12 |
| 102 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10 |
| 140 | 22, 24 |
| 141 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 |
| 159 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24 |
| 168 | 3, 3.5, 4, 4.5, 5, 5.5, 6, 8, 10, 12, 14, 16, 18 |
Sizes are listed as recorded on the current stock sheet. Wall thicknesses follow the standard metric and imperial schedules for each diameter; intermediate and heavier walls are available on request.
Standards and Specifications
Inconel 625 pipe and tube is ordered against the ASTM / ASME product standards below. Which one applies depends on whether the item is pipe or tube, and whether it is seamless or welded — a distinction that changes the permitted manufacturing route, the test schedule and the tolerances. State the standard and the UNS number on the enquiry and MESCO will supply the matching product form.
| Scope | Standard or designation |
|---|---|
| Seamless pipe and tube | ASTM B444 / ASME SB444 |
| Welded tube | ASTM B704 / ASME SB704 |
| Welded pipe | ASTM B705 / ASME SB705 |
| General requirements | ASTM B829 (nickel alloy pipe and tube) |
| Unified numbering system | UNS N06625 |
| Werkstoff / European designation | 2.4856 / NiCr22Mo9Nb |
| Other trade designations | Alloy 625, DIN 2.4856, BS NA21, JIS NCF 625 |
| Sour service qualification | NACE MR0175 / ISO 15156 |
Mechanical and Physical Properties
The values below are the reference figures used when specifying Inconel 625 pipe and tube. Mechanical requirements are minimums taken from the applicable ASTM product standard in the solution-annealed condition; actual results for your heat are reported on the mill test certificate that ships with the order.
| Property | Reference value |
|---|---|
| Tensile strength, solution annealed | 827 MPa (120 ksi) minimum |
| Yield strength, 0.2 % offset | 414 MPa (60 ksi) minimum |
| Elongation | 30 % minimum |
| Hardness | 35 HRC maximum |
| Density | 8.44 g/cm³ |
| Melting range | 1290 – 1350 °C |
| Thermal conductivity at 20 °C | 9.8 W/m·K |
| Coefficient of thermal expansion, 20–100 °C | 12.8 × 10-6/K |
| Service temperature | Cryogenic to approximately 980 °C, depending on load and atmosphere |
| Pitting resistance equivalent number (PREN) | Approximately 50 |
Key Features
Chloride Pitting and Crevice Resistance
The molybdenum content of 8–10 % raises the pitting resistance equivalent number to roughly 50, which is what allows 625 tube to run in chloride-bearing cooling water, seawater and brine circuits where 316L and even 6 % molybdenum super-austenitics begin to pit.
Strength Without Age Hardening
The alloy is strengthened in solid solution by molybdenum and niobium rather than by a precipitation cycle. Welding therefore does not destroy the strength of the parent tube, and the heat-affected zone does not need a post-weld ageing treatment.
Resistance to Chloride Stress Corrosion Cracking
Inconel 625 is effectively immune to chloride-ion stress corrosion cracking in the conditions that crack austenitic stainless steels, which is the principal reason it is selected for hot chloride service and for insulated or heat-traced lines.
High-Temperature Stability
Oxidation resistance and creep strength hold to approximately 980 °C, and the alloy resists scaling and carburisation better than iron-based grades at the same duty point.
Fabrication and Weldability
The tube bends, flares, expands into tubesheets and welds with conventional nickel-alloy procedures. It is routinely supplied as U-bend exchanger tube and as welded assemblies without a post-weld heat treatment.
Broad Chemical Compatibility
Serviceable in nitric and phosphoric acid, in oxidising and reducing media, in neutral salts and in seawater, and qualified for sour service under NACE MR0175 / ISO 15156.
Where Inconel 625 Pipe and Tube Is Used
Heat exchangers and condensers. Seamless 625 tube is the standard answer for shell-and-tube units handling chlorides, seawater or aggressive process streams, and for U-bend bundles where bending must not compromise the tube wall.
Chemical and petrochemical plant. Reactor internals, transfer lines, column internals, catalyst support hardware and flue-gas ducting where mixed acids or hot halides rule out stainless grades.
Marine and offshore. Seawater piping, riser and umbilical components, valve trim and splash-zone hardware — the alloy tolerates both chloride pitting and the crevice conditions created by flanges and supports.
Power generation and pollution control. Superheater and reheater tubing, flue-gas desulphurisation scrubber internals and ductwork exposed to wet chloride-laden gas.
Aerospace and high-temperature engineering. Thin-wall ducting, exhaust and engine hardware where fatigue and creep strength are needed at temperature in a thin section.
Nuclear and cryogenic service. Components requiring strength and toughness across an exceptionally wide temperature band.
How to Specify and Order
Give the size
Outside diameter and wall thickness, in millimetres or inches, plus length and quantity. Where a size does not appear in the stock table above, send the drawing anyway — many outside-range dimensions are producible to order.
State the product form and standard
Seamless or welded, pipe or tube, and the governing standard — ASTM B444, B704, B705 or B829. Add NACE MR0175 where the service contains hydrogen sulphide.
Confirm the delivery condition
Solution annealed is the normal supply condition. Surface finish, straightness, end preparation and tolerance class can be specified at enquiry stage.
Receive the quotation and certificate
MESCO confirms availability, lead time and price, and issues a mill test certificate with the chemical analysis and mechanical results for the heat supplied.
Frequently Asked Questions
What is the difference between Inconel 625 pipe and Inconel 625 tube?
Pipe is dimensioned to nominal bore and a schedule wall, and is used for conveying fluids in process lines. Tube is dimensioned to an exact outside diameter and wall thickness and is used in heat transfer and instrument applications. Both are covered by ASTM B444 for the seamless form, but they are ordered to different dimensional conventions — tell us which you need and we will match the tolerance class.
Can you supply both seamless and welded Inconel 625 pipe?
Yes. Seamless is produced to ASTM B444 / B704 route requirements and welded to ASTM B704 (tube) or B705 (pipe). Seamless is normally preferred for exchanger tube and high-pressure service; welded is generally more economical and more readily available in thin walls and small quantities.
What is the largest size available?
The current stock list runs to 168 mm outside diameter with walls up to 24 mm, and down to 1.58 mm capillary with walls from 0.29 mm. Larger diameters and non-standard walls can be produced to order — send the requirement for a feasibility and lead-time check.
Is Inconel 625 suitable for seawater and for sour service?
Inconel 625 is widely used in seawater piping and in chloride-bearing cooling circuits because of its resistance to pitting, crevice corrosion and chloride stress corrosion cracking. It is also listed for sour service in NACE MR0175 / ISO 15156, subject to the hardness and environmental limits in that standard. Confirm the specific environment with our technical team when the duty is at the limit.
In what condition is the tube delivered?
Solution annealed as standard, with the option of pickled, bright annealed or polished finish. U-bend, cut-to-length and end-prepared forms are available. Full traceability documents travel with every consignment.
What information do you need to quote?
Outside diameter, wall thickness, length, quantity, product form (seamless or welded, pipe or tube) and the governing standard. Send a drawing or a size list and we will respond with availability, price and lead time — a mixed size list on one purchase order is normal for us.
Request a Quotation for Inconel 625 Pipe and Tube
Send your outside diameter, wall thickness and quantity list. MESCO STEEL will confirm which sizes are available from stock, which are produced to order, and the lead time and price for each. Mill test certificates and full traceability documents are issued with every shipment.
- Quote against a size list, a drawing or a specification
- Mixed-diameter orders consolidated into one shipment
- Mill test certificate and heat traceability included
Send your enquiry through the contact form on this page and our technical sales team will reply with availability and pricing.
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