Alloy 625 Inconel® (UNS N06625 / W.Nr. 2.4856) Nickel Alloy Steel Pipe & Fittings
July 25, 2026
Incoloy 800 (UNS N08800 / W.Nr. 1.4876) Seamless Steel Pipe
High-Temperature Oxidation Resistance, Creep-Rupture Strength, Metallurgical Stability, and Precision Manufacturing Dimensions for Industrial Process Systems.
UNS N08800 Certified
100% PMI Tested
EN 10204 3.1 / 3.2
Key Material Parameters & Operational Limits
1. Seamless Incoloy 800 Pipe
A Seamless Incoloy 800 Pipe (UNS N08800 / W.Nr. 1.4876) represents a cornerstone engineered solution within high-temperature, highly corrosive industrial environments. Designed specifically for structural stability, oxidation resistance, and reliable mechanical properties under severe thermal stresses, Incoloy 800 is an austenitic iron-nickel-chromium solid-solution strengthened alloy. Manufactured through precision hot extrusion or high-grade cold-drawing processes starting from solid alloy billets, seamless pipes manufactured under ASTM B407 eliminate the structural vulnerabilities, localized heat-affected zones (HAZ), and longitudinal stress points common to welded alternatives.
The nickel-iron-chromium triad within Incoloy 800 provides exceptional operational flexibility. Nickel content (30.0% to 35.0%) ensures remarkable resistance to chloride-ion stress corrosion cracking (SCC) while stabilizing the austenitic crystal structure against phase transformations during long-term high-temperature exposure. Chromium (19.0% to 23.0%) imparts essential oxidation, carburization, and scaling resistance by creating an adherent, self-passivating chromium oxide surface coating. The substantial iron balance (minimum 39.5%) maintains structural affordability and excellent fabricability, while strict controls over titanium (0.15% to 0.60%) and aluminum (0.15% to 0.60%) promote stable microstructural behavior under cyclic heating.
Under the specification ASTM B407 (and its companion ASME SB407), seamless Incoloy 800 pipe and tube products undergo rigorous dimensional processing, non-destructive testing, and heat treatments to guarantee thermal stability up to 1500°F (816°C). Whether deployed in petrochemical steam-methane reformers, nuclear steam generator circuits, or industrial furnace retorts, Incoloy 800 seamless pipes deliver superior metallurgical integrity and unyielding performance.
2. Core Metallurgical Characteristics & Technical Advantages
Austenitic Phase Stability
Maintains a completely face-centered cubic (FCC) austenitic structure across all operational temperature ranges. Unlike lower-nickel alloy steels, Incoloy 800 does not experience embrittling phase transformations, such as sigma phase precipitation, during prolonged exposure to temperatures up to 816°C (1500°F).
Carburization & Nitriding Defense
The balanced addition of titanium and aluminum (min 0.30% combined Ti+Al) acts synergistically with high chromium content to establish a barrier layer against carbon and nitrogen ingress in aggressive furnace atmospheres and ethylene cracking furnaces.
Aqueous & SCC Immunity
High nickel concentration grants exceptional resistance to transgranular chloride stress-corrosion cracking, making it superior to 300-series stainless steels in harsh aqueous chemical processing environments containing polythionic acid and caustic media.
Thermal Fatigue & Seamless Strength
The seamless manufacturing process eliminates longitudinal weld imperfections and residual stress gradients. This uniform wall cross-section drastically enhances resistance to rapid thermal cycling, thermal shock, and pressure variations.
3. Chemical Composition Breakdown (ASTM B407 / UNS N08800)
Table 1: Strict elemental limits required for ASTM B407 Incoloy 800 pipe. All values represent mass percentages.
| Element | Symbol | ASTM B407 Min (%) | ASTM B407 Max (%) | Metallurgical Role |
|---|---|---|---|---|
| Nickel | Ni | 30.00 | 35.00 | FCC structure stabilization, SCC resistance |
| Chromium | Cr | 19.00 | 23.00 | High-temperature oxidation & scaling defense |
| Iron | Fe | 39.50 | Balance | Base matrix structure, cost-efficiency |
| Carbon | C | – | 0.10 | Controlled limit prevents excessive carbide growth |
| Aluminum | Al | 0.15 | 0.60 | Internal oxide film formation & strengthening |
| Titanium | Ti | 0.15 | 0.60 | Carbo-nitride stabilization, creep resistance |
| Copper | Cu | – | 0.75 | Aqueous corrosion enhancement in reducing media |
| Manganese | Mn | – | 1.50 | Deoxidizer and hot workability enhancement |
| Silicon | Si | – | 1.00 | Improves oxidation resistance in hot gases |
| Sulfur | S | – | 0.015 | Strictly controlled to prevent hot shortness |
4. Mechanical Property Specifications
Table 2: Minimum room-temperature mechanical property criteria for Incoloy 800 seamless pipes per ASTM B407 under different finishing conditions.
| Condition & Finish | Tensile Strength (MPa) | Tensile Strength (ksi) | Yield Strength 0.2% Offset (MPa) | Yield Strength (ksi) | Elongation in 2 in. (%) | Hardness Max |
|---|---|---|---|---|---|---|
| Cold-Worked Annealed | ≥ 520 | ≥ 75 | ≥ 205 | ≥ 30 | ≥ 30% | 90 HRB / 192 HBW |
| Hot-Finished Annealed | ≥ 450 | ≥ 65 | ≥ 170 | ≥ 25 | ≥ 30% | 85 HRB / 170 HBW |
5. Comprehensive Physical & Thermodynamic Properties
Table 3: Fundamental physical constants and temperature-dependent thermal parameters for Incoloy 800 (UNS N08800).
| Physical Parameter | Metric Units | Imperial Units | Test Condition / Temperature |
|---|---|---|---|
| Density | 8.03 g/cm³ | 0.290 lb/in³ | 20°C (68°F) |
| Melting Range | 1357 – 1400 °C | 2475 – 2550 °F | Liquidus / Solidus Phase Bounds |
| Specific Heat Capacity | 460 J/kg·°C | 0.11 Btu/lb·°F | 20°C (68°F) |
| Thermal Conductivity | 11.2 W/m·K | 77.7 Btu·in/ft²·h·°F | 20°C (68°F) |
| Thermal Conductivity (Elevated) | 24.7 W/m·K | 171 Btu·in/ft²·h·°F | 700°C (1292°F) |
| Mean Coeff. of Thermal Expansion | 14.4 µm/m·°C | 8.0 × 10⁻⁶ in/in·°F | 20°C to 100°C (68°F to 212°F) |
| Mean Coeff. of Thermal Expansion | 17.3 µm/m·°C | 9.6 × 10⁻⁶ in/in·°F | 20°C to 700°C (68°F to 1292°F) |
| Modulus of Elasticity | 196 GPa | 28.5 × 10⁶ psi | 20°C (68°F) Tensile Modulus |
| Electrical Resistivity | 1.06 µΩ·m | 638 Ohm-circ mil/ft | 20°C (68°F) |
| Curie Temperature | -115 °C | -175 °F | Non-magnetic at room temperature |
6. Dimensional Tolerances: Outer Diameter (OD) Per ASTM B407
Table 4: Standard permissible variations in specified or calculated outer diameter for cold-finished and hot-finished Incoloy 800 seamless tubing and piping.
| Manufacturing Process | Specified OD (Inches) | Permissible OD Var. (Inches) | Specified OD (mm) | Permissible OD Var. (mm) |
|---|---|---|---|---|
| COLD-FINISHED SEAMLESS PIPES AND TUBES | ||||
| Cold-Finished | 0.500 to 5/8, excl. | ±0.005 | 12.7 to 15.8, excl. | ±0.127 |
| Cold-Finished | 5/8 to 1 1/2, incl. | ±0.0075 | 15.8 to 38.1, incl. | ±0.190 |
| Cold-Finished | Over 1 1/2 to 3 1/2, incl. | ±0.010 | Over 38.1 to 88.9, incl. | ±0.254 |
| Cold-Finished | Over 3 1/2 to 4 1/2, incl. | ±0.015 | Over 88.9 to 114.3, incl. | ±0.381 |
| Cold-Finished | Over 4 1/2 to 6, incl. | ±0.020 | Over 114.3 to 152.4, incl. | ±0.508 |
| Cold-Finished | Over 6 to 6 5/8, incl. | ±0.025 | Over 152.4 to 168.3, incl. | ±0.635 |
| HOT-FINISHED SEAMLESS PIPES AND TUBES | ||||
| Hot-Finished | 2 1/2 to 5 1/2, excl. | ±0.031 | 63.5 to 139.7, excl. | ±0.787 |
| Hot-Finished | 5 1/2 to 9 1/4, incl. | ±0.047 | 139.7 to 234.9, incl. | ±1.190 |
7. Wall Thickness Tolerances & Eccentricity Controls
Table 5: Permissible percentage variations in nominal wall thickness under ASTM B407 standard manufacturing specifications.
| Pipe Condition | Nominal Outer Diameter Range (Inches) | Nominal Outer Diameter Range (mm) | Permissible Wall Thickness Variation (%) |
|---|---|---|---|
| Cold-Finished | 0.500 to 5/8, excl. | 12.7 to 15.8, excl. | ± 15.0 % |
| Cold-Finished | 5/8 to 4 1/2, incl. | 15.8 to 114.3, incl. | ± 10.0 % |
| Cold-Finished | Over 4 1/2 to 6 5/8, incl. | Over 114.3 to 168.3, incl. | ± 12.5 % |
| Hot-Finished | 2 1/2 to 9 1/4, incl. | 63.5 to 234.9, incl. | ± 12.5 % |
8. Standard Pipe Sizes, Schedules & Nominal Mass Chart
Table 6: Standard ANSI/ASME B36.19M dimensions and calculated lineal weight for Incoloy 800 seamless pipes based on a density of 8.03 g/cm³.
| NPS (Inches) | DN (mm) | Outer Diameter (mm) | Schedule | Wall Thickness (mm) | Inner Diameter (mm) | Nominal Weight (kg/m) | Nominal Weight (lb/ft) |
|---|---|---|---|---|---|---|---|
| 1/2″ | DN 15 | 21.34 | Sch 10S | 2.11 | 17.12 | 1.02 | 0.69 |
| 1/2″ | DN 15 | 21.34 | Sch 40S | 2.77 | 15.80 | 1.29 | 0.87 |
| 1/2″ | DN 15 | 21.34 | Sch 80S | 3.73 | 13.88 | 1.65 | 1.11 |
| 3/4″ | DN 20 | 26.67 | Sch 40S | 2.87 | 20.93 | 1.71 | 1.15 |
| 1″ | DN 25 | 33.40 | Sch 40S | 3.38 | 26.64 | 2.54 | 1.71 |
| 1-1/2″ | DN 40 | 48.26 | Sch 40S | 3.68 | 40.90 | 4.11 | 2.76 |
| 2″ | DN 50 | 60.33 | Sch 40S | 3.91 | 52.51 | 5.53 | 3.72 |
| 2″ | DN 50 | 60.33 | Sch 80S | 5.54 | 49.25 | 7.60 | 5.11 |
| 3″ | DN 80 | 88.90 | Sch 40S | 5.49 | 77.92 | 11.47 | 7.71 |
| 4″ | DN 100 | 114.30 | Sch 40S | 6.02 | 102.26 | 16.33 | 10.97 |
| 6″ | DN 150 | 168.28 | Sch 40S | 7.11 | 154.06 | 28.71 | 19.29 |
| 8″ | DN 200 | 219.08 | Sch 40S | 8.18 | 202.72 | 43.20 | 29.03 |
9. Sub-Grade Comparison: Incoloy 800 vs 800H vs 800HT
While Incoloy 800 (UNS N08800) provides supreme baseline performance for intermediate temperatures up to 1100°F (593°C) and general aqueous corrosion service, high-stress creep applications at elevated temperatures necessitate understanding the specialized variants: Incoloy 800H (UNS N08810) and Incoloy 800HT (UNS N08811).
Table 7: Critical metallurgical distinctions between the primary Alloy 800 sub-grades under ASTM B407.
| Grade Distinction | Incoloy 800 (UNS N08800) | Incoloy 800H (UNS N08810) | Incoloy 800HT (UNS N08811) |
|---|---|---|---|
| Carbon Content (%) | 0.10 Max | 0.05 to 0.10 | 0.06 to 0.10 |
| Aluminum + Titanium (%) | 0.30 to 1.20 Combined | 0.30 to 1.20 Combined | 0.85 to 1.20 Combined |
| ASTM Grain Size | No requirement (Fine grain) | ASTM No. 5 or coarser | ASTM No. 5 or coarser |
| Heat Treatment Temp | Mill Annealed (~980°C – 1010°C) | Solution Annealed (~1120°C min) | Solution Annealed (~1150°C min) |
| Primary Application Focus | General aqueous corrosion & moderate thermal (< 593°C) | High-temperature creep service (> 593°C) | Maximum creep-rupture strength (> 700°C) |
10. International Standard Equivalents Matrix
Table 8: Cross-reference table mapping Incoloy 800 seamless pipes to global engineering standards across primary regions.
| Standardization Organization | Standard Specification Code | Equivalent Alloy Grade / Name | Material Number / UNS |
|---|---|---|---|
| USA (ASTM / ASME) | ASTM B407 / ASME SB407 | Incoloy 800 / Alloy 800 | UNS N08800 |
| Germany / Europe (DIN EN) | EN 10216-5 / DIN 17459 | X10NiCrAlTi32-20 | W.Nr. 1.4876 |
| Japan (JIS) | JIS H 4552 / JIS G 4902 | NCF 800 TP / NCF 800 | JIS NCF 800 |
| China (GB/T) | GB/T 15007 / GB/T 24513.2 | NS1102 / NS112 | 06Cr21Ni30FeUP |
| International (ISO) | ISO 6207 (Seamless Tubes) | FeNi30Cr21AlTi | NW 8800 |
| Russia (GOST) | GOST 14965 | 08ChN35VT / ChN35VT | ЭП670 |
| United Kingdom (BS) | BS 3074 NA15 | NA15 | NA 15 |
11. Seamless Pipe Manufacturing & Processing Workflow
To achieve compliance with ASTM B407 tight dimensional tolerances and uniform grain structures, Incoloy 800 seamless pipes undergo a rigorous, multi-stage hot-extrusion or cold-drawing manufacturing process starting from vacuum-melted high-purity billets.
VIM + ESR Melting
Vacuum Induction Melting (VIM) followed by Electroslag Remelting (ESR) ensures minimal non-metallic inclusions and refined ingot chemistry.
Hot Extrusion / Piercing
Solid billets are heated to 1150°C – 1200°C and extrude-pierced to form a hollow thick-walled seamless shell without longitudinal seams.
Precision Cold Pilgering
Multiple cold-drawing or pilgering passes refine wall thickness, improve surface finish (Ra < 0.8 µm), and tighten outer diameter tolerances.
Bright Annealing
Heat treatment conducted at 980°C – 1040°C in a protective hydrogen atmosphere relieves internal stresses and optimizes ductility.
12. Quality Control, Inspection & Testing Framework
Table 9: Mandatory quality assurance tests executed per ASTM B407 / ASME SB407 for Incoloy 800 seamless pipes.
| Inspection Method | Governing Standard | Acceptance Criteria / Purpose | Execution Frequency |
|---|---|---|---|
| Positive Material ID (PMI) | ASTM E1476 / XRF / OES | Verifies Ni, Cr, Fe content match UNS N08800 specs | 100% of Pipe Lengths |
| Hydrostatic Pressure Test | ASTM B829 / ASTM E1003 | P = 2ST/D; no leaks or permanent distortion at test pressure | 100% of Pipes (Or NDT) |
| Eddy Current Testing (ECT) | ASTM E426 / ASTM E571 | Detects surface defects, micro-cracks, and discontinuities | 100% Seamless Tubing |
| Ultrasonic Examination (UT) | ASTM E213 | Identifies internal volumetric defects and wall thickness variations | Critical Pressure Specs |
| Intergranular Corrosion Test | ASTM A262 Practice C / E | Verifies resistance to chromium depletion at grain boundaries | 1 Sample per Heat / Lot |
| Grain Size Determination | ASTM E112 | Ensures fine-grained matrix structure for Alloy 800 standard | 1 Sample per Heat Lot |
| Flaring & Flattening Tests | ASTM B751 / B829 | No cracking observed under 60-degree cone flaring or flat compression | 2 Pipes per Heat Lot |
13. Primary Industrial Application Sectors
Petrochemical & Refining
- Steam-methane reformer outlet pigtails
- Ethylene pyrolysis furnace transfer lines
- Hydrocracker process heat exchangers
- Thermal cracking heater coils
Power Generation & Nuclear
- Once-through steam generator (OTSG) tubes
- Superheater and reheater tubing circuits
- High-temperature fossil fuel boiler piping
- Nuclear thermal management loops
Industrial Heat Treating
- Radiant furnace heating tubes
- Annealing retorts, muffles, and baskets
- Carburizing atmosphere piping
- Thermocouple protection sheaths
Chemical Processing
- Nitric acid condenser piping systems
- Organic acid processing evaporators
- Polythionic acid resistant process lines
- Domestic appliance element sheathing
14. ASTM & ASME Specification Scope Matrix
Table 10: Full cross-reference of ASTM/ASME specifications applicable to Incoloy 800 across diverse product forms.
| Product Form | ASTM Standard | ASME Standard | Other International Standards |
|---|---|---|---|
| Seamless Pipe & Tube | ASTM B407 / B829 | ASME SB407 / SB829 | BS 3074 NA15, ISO 6207, VdTÜV 412 |
| Condenser & Heat Exchanger Tubes | ASTM B163 | ASME SB163 | ASME N-20 (Nuclear) |
| Welded Pipe | ASTM B514 / B775 | ASME SB514 / SB775 | 100% X-Ray Class 1 / Class 2 |
| Welded Tubes | ASTM B515 / B751 | ASME SB515 / SB751 | Precision redraw tubes available |
| Plate, Sheet & Strip | ASTM B409 / B906 | ASME SB409 / SB906 | BS 3072NA15, AMS 5871, ISO 6208 |
| Rod, Bar & Wire | ASTM B408 | ASME SB408 | AMS 5766, BS 3076NA15, ISO 9723 |
| Forgings & Flanges | ASTM B564 | ASME SB564 | ASME Code Case 1949, ISO 9725 |
| Butt-Weld Pipe Fittings | ASTM B366 | ASME SB366 | WP800 / WP800H / WP800HT |
15. Fabrication, Bending, and Welding Technical Directives
Incoloy 800 seamless pipes exhibit excellent hot and cold workability paired with exceptional weldability. Standard industrial joining procedures, including Gas Tungsten Arc Welding (GTAW / TIG) and Gas Metal Arc Welding (GMAW / MIG), can be readily executed without pre-heating requirement.
Recommended Welding Consumables
- Matching Weld Filler: INCONEL Filler Metal 82 (AWS A5.14 ERNiCr-3) for GTAW/GMAW service up to 1000°F (538°C).
- High-Temperature Filler (> 1000°F): INCONEL Filler Metal 617 or INCO-WELD A (AWS A5.11 ENiCrFe-2) covered electrodes to maintain matching creep strength.
- Dissimilar Welds: When joining Incoloy 800 to carbon steel or stainless steel, INCONEL Filler Metal 82 is recommended to accommodate differential thermal expansion.
Post-Weld Heat Treatment (PWHT): Incoloy 800 does not require mandatory PWHT after welding to restore corrosion resistance. However, for applications exposed to caustic environments or polythionic acid stress corrosion cracking conditions, a solution stress-relief treatment at 870°C to 930°C (1600°F to 1700°F) is recommended.
16. Summary & Order Specification Guidelines
When issuing inquiries or purchase orders for Incoloy 800 (UNS N08800) ASTM B407 seamless pipe, ensure the following parameters are explicitly stated to enable precise compliance testing and mill certification:
ASTM B407 / ASME SB407
NPS / DN size, Schedule 10S/40S/80S or OD x WT
Cold-finished annealed / Hot-finished annealed
100% PMI, Hydrostatic or ECT, EN 10204 3.1
