Inconel 686 pipes and tubes are selected for highly corrosive environments where resistance to pitting and crevice corrosion is a major concern. UNS N06686, also known as W.Nr 2.4606, contains 19% to 23% chromium, 15% to 17% molybdenum and 3% to 4.4% tungsten. This combination gives Alloy 686 exceptionally strong resistance to localized corrosion, particularly in aggressive chloride containing services. Amardeep Steel supplies Inconel 686 seamless pipe and tube to ASTM B622 and B163, along with welded pipe to ASTM B619. Compare the grade with our Hastelloy C276 pipes and tubes and Inconel 625 pipes and tubes, or browse all Inconel pipes and tubes. Every order includes an EN 10204 3.1 mill test certificate and full heat traceability.
What Are Inconel 686 Pipes and Tubes?
Alloy 686 is a nickel, molybdenum, chromium, as well as tungsten alloy designed for the highly corrosive environments of mixed acids and chlorides that are common in flue gas desulfurization, processing of chemicals and wastes. The extremely low levels of carbon (maximum 0.010) and controlled silicon ensure that grain boundary precipitations in welding can be avoided and thus the corrosion resistance of welded joints is retained.
Why Tungsten and Molybdenum Matter in 686
Molybdenum and tungsten together resist localised attack in chloride and reducing acid media. With about 16% molybdenum, 4% tungsten and 21% chromium, 686 handles both oxidising and reducing conditions better than C276, which has less chromium.
Inconel 686 Pipe and Tube Specifications
Parameter | Details |
|---|---|
Grade | UNS N06686, Inconel 686, Alloy 686, W.Nr 2.4606 |
Seamless pipe and tube | ASTM B622 / ASME SB622 |
Seamless condenser and heat exchanger tube | ASTM B163 / ASME SB163 |
Welded pipe | ASTM B619 / ASME SB619 |
Welded tube | ASTM B626 / ASME SB626 |
Pipe sizes | 1/2" to 6" NB, SCH 5S, 10S, 40S, 80S; larger on request |
Condition | Solution annealed |
Length | Random, fixed and cut lengths |
Ends | Plain end; bevelled on request |
Test Certificate | EN 10204 3.1, with 3.2 available on request |
Inconel 686 Chemical Composition
Element | Content (%) |
|---|---|
Nickel (Ni) | Balance |
Chromium (Cr) | 19.0 to 23.0 |
Molybdenum (Mo) | 15.0 to 17.0 |
Tungsten (W) | 3.0 to 4.4 |
Iron (Fe) | 5.0 max |
Titanium (Ti) | 0.02 to 0.25 |
Carbon (C) | 0.010 max |
Manganese (Mn) | 0.75 max |
Silicon (Si) | 0.08 max |
Phosphorus (P) | 0.04 max |
Sulfur (S) | 0.02 max |
Limits per ASTM B622. Special Metals produces 686 to a tighter iron limit (2.0% maximum).
Inconel 686 Mechanical Properties
Property (annealed, ASTM B622) | Value |
|---|---|
Tensile Strength, min | 690 MPa (100 ksi) |
Yield Strength (0.2% offset), min | 310 MPa (45 ksi) |
Elongation in 50 mm, min | 45% |
Minimums per ASTM B622 for solution annealed pipe and tube.
Inconel 686 Physical Properties
Property | Typical value |
|---|---|
Density | 8.73 g/cm³ |
Melting range | 1338°C to 1380°C |
Mean thermal expansion (0°C to 200°C) | 12.2 µm/m·°C |
Modulus of elasticity (21°C) | 207 GPa |
Typical values from the alloy producer. Values for each heat are on the mill certificate.
Inconel 686 Equivalent Grades
Standard | Designation |
|---|---|
UNS | N06686 |
Werkstoff Nr. | 2.4606 |
EN / DIN name | NiCr21Mo16W |
Trade names | Inconel 686, Alloy 686 |
ASTM pipe / tube | B622, B163 (seamless); B619, B626 (welded) |
Inconel 686 vs Hastelloy C276 vs C22
Property | Inconel 686 | Hastelloy C276 | Hastelloy C22 |
|---|---|---|---|
Chromium | 19.0 to 23.0% | 14.5 to 16.5% | 20.0 to 22.5% |
Molybdenum | 15.0 to 17.0% | 15.0 to 17.0% | 12.5 to 14.5% |
Tungsten | 3.0 to 4.4% | 3.0 to 4.5% | 2.5 to 3.5% |
Carbon, max | 0.010% | 0.010% | 0.015% |
Typical choice | Mixed acids, FGD, severe pitting | Reducing acids, general CPI | Oxidising and mixed media |
For reducing acid service, see our Hastelloy C276 pipes and tubes. For oxidising media, see our Hastelloy C22 pipes and tubes.
Inconel 686 Pipe Schedule and Weight Chart
NPS | OD (mm) | SCH 5S | SCH 10S | SCH 40S | SCH 80S |
|---|---|---|---|---|---|
1/2" | 21.34 | 1.65 mm / 0.89 kg/m | 2.11 mm / 1.11 kg/m | 2.77 mm / 1.41 kg/m | 3.73 mm / 1.80 kg/m |
3/4" | 26.67 | 1.65 mm / 1.13 kg/m | 2.11 mm / 1.42 kg/m | 2.87 mm / 1.87 kg/m | 3.91 mm / 2.44 kg/m |
1" | 33.40 | 1.65 mm / 1.44 kg/m | 2.77 mm / 2.33 kg/m | 3.38 mm / 2.78 kg/m | 4.55 mm / 3.60 kg/m |
1 1/2" | 48.26 | 1.65 mm / 2.11 kg/m | 2.77 mm / 3.46 kg/m | 3.68 mm / 4.50 kg/m | 5.08 mm / 6.02 kg/m |
2" | 60.33 | 1.65 mm / 2.66 kg/m | 2.77 mm / 4.37 kg/m | 3.91 mm / 6.05 kg/m | 5.54 mm / 8.32 kg/m |
3" | 88.90 | 2.11 mm / 5.02 kg/m | 3.05 mm / 7.18 kg/m | 5.49 mm / 12.56 kg/m | 7.62 mm / 16.99 kg/m |
4" | 114.30 | 2.11 mm / 6.49 kg/m | 3.05 mm / 9.31 kg/m | 6.02 mm / 17.88 kg/m | 8.56 mm / 24.82 kg/m |
6" | 168.28 | 2.77 mm / 12.57 kg/m | 3.40 mm / 15.37 kg/m | 7.11 mm / 31.43 kg/m | 10.97 mm / 47.33 kg/m |
Dimensions follow ASME B36.19M. Weights are calculated at 8.73 g/cm³ as (OD minus wall) x wall x π x 8.73 / 1000.
Applications of Inconel 686 Pipes and Tubes
- Flue gas desulfurization ducting, outlet and bypass lines
- Chemical process piping in mixed acid service
- Pollution control and waste incineration scrubbers
- Pulp and paper bleach plant lines
- Seawater and brine systems with severe crevice conditions
Testing and Documentation
Every order of Inconel 686 pipe and tube goes through the checks below at our testing facility or approved third party labs.
- Chemical analysis and PMI
- Tension test
- Flattening and flaring tests
- Hydrostatic or non-destructive electric test on each length
- ASTM G28 intergranular corrosion test on request
- Ultrasonic testing on request
- Visual and dimensional inspection
Mill test certificates are issued to EN 10204 3.1, with 3.2 available on request. You can view our approvals on the certificates page.
Packing and Marking
Each length is marked with the standard, UNS N06686, size, heat number and manufacturer name. Ends are capped and tubes are packed in wooden boxes, kept apart from carbon steel. Read more about our packing and despatch process.
Request a Quote for Inconel 686 Pipes & Tubes
Send us the OD or NB, wall or schedule, standard (B622, B163, B619 or B626), length and quantity, and our team will reply with price and delivery. Use the enquiry form or reach us through the contact page.
Frequently Asked Questions
What is Inconel 686?
Inconel 686 (UNS N06686, W.Nr 2.4606) is a nickel-chromium-molybdenum-tungsten alloy with 19% to 23% chromium, 15% to 17% molybdenum and 3% to 4.4% tungsten, used in severe acid and chloride service.
Which ASTM standard covers Inconel 686 pipe?
ASTM B622 covers seamless pipe and tube, ASTM B163 covers seamless condenser and heat exchanger tube, ASTM B619 covers welded pipe and ASTM B626 covers welded tube.
What are the mechanical properties of Inconel 686 pipe?
ASTM B622 sets 690 MPa (100 ksi) minimum tensile strength, 310 MPa (45 ksi) minimum yield and 45% minimum elongation.
What is the difference between Inconel 686 and Hastelloy C276?
Both have about 16% molybdenum and 4% tungsten, but 686 has 19% to 23% chromium against 14.5% to 16.5% in C276, which improves resistance in oxidising and mixed acid media.
