Inconel 601 adds 1.0–1.7% aluminium and raises chromium from 15.5% to 23% (typical). The aluminium creates an Al₂O₃ sub-layer under the Cr₂O₃ surface oxide, making 601 significantly more resistant to cyclic oxidation and carburisation above 1800°F (982°C). Below 1800°F, where oxidation is not the primary concern, Inconel 600 is adequate and costs less.
ASTM B167 Inconel 600/601/690 Seamless Pipe & Tube Standard
ASTM B167 is the standard specification that covers six Ni-Cr-Fe alloys, including Inconel 600, 601, 690, and specialist grades, and their high-chromium variants. These are the primary Ni-Cr-Fe alloys for extreme-temperature oxidation resistance, nuclear steam generation, and corrosive high-heat service from 1200°F to 2200°F (650°C to 1200°C).
The specification covers six UNS designations (UNS N06600, N06601, N06603, N06690, N06025, and N06045) in cold-worked, hot-worked, and hot-finished conditions. It defines chemical composition, mechanical properties that vary by alloy and diameter, dimensional tolerances for cold-worked and hot-finished products, hydrostatic testing at 1,000 psi (6.9 MPa) maximum, and product marking. General requirements for chemical check analysis conform to ASTM B880.
ASTM B167 Inconel pipe and tube serve chemical processing furnaces, nuclear PWR steam generators, heat treatment retorts and radiant tubes, aerospace gas turbine exhaust ducting, petrochemical reformer components, and waste incineration equipment. This guide covers all six alloys: Inconel 600, 601, 690, 603, UNS N06025, and UNS N06045, with their chemical and mechanical properties, tolerances, fibre stress values, and applications to help engineers and procurement teams select the right Ni-Cr-Fe product.
ASTM B167 PDF Free Download
ASTM B167 PDF Free Download
What is ASTM B167?
ASTM B167 is the ASTM International specification standard for nickel-chromium-iron alloy seamless pipe and tube. It is governed by ASTM Committee B-2 on Nonferrous Metals and Alloys, Subcommittee B02.07 on Refined Nickel and Cobalt and Their Alloys. This standard has been approved for use by agencies of the U.S. Department of Defense.
The specification covers Inconel seamless pipe and tube in six nickel-chromium-iron alloys, each targeting a specific high-temperature or corrosion environment. The Ni-Cr-Fe system, with 45–72% Ni, 14–31% Cr, and 6–25% Fe, forms a stable austenitic structure that resists oxidation, carburisation, and stress corrosion cracking at temperatures far beyond what stainless steels or Incoloy alloys can handle.
Inconel seamless tube dimensions use OD and minimum or nominal wall thickness, while pipe dimensions follow NPS designations per ANSI B36.19. The specification covers sizes from small-bore tubing through large-diameter pipe in both cold-worked and hot-worked conditions.
The ASME equivalent is SB-167, listed in the ASME Boiler and Pressure Vessel Code, Section II, Part B. Materials meeting ASTM B167 can carry the SB-167 designation for code-stamped pressure equipment in nuclear facilities, power plants, and chemical process vessels.
Chemical Composition of ASTM B167
The chemical composition of ASTM B167 tubes is carefully controlled to ensure high strength, corrosion resistance, and performance in extreme environments. It primarily includes nickel, chromium, and other alloying elements, with specific limits varying by grade as shown in the table below.
| GRADE | UNS Designation |
Standard (Pipe) |
Chemical Requirement (Max unless range specified) | ||||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Fe | Ti | Al | Co | |||
| Inconel 600 | N06600 | B167 | 0.15 | 1.00 | - | 0.015 | 0.50 | 72.0 min | 14.0–17.0 | - | 0.50 | 6.0–10.0 | - | - | - |
| Inconel 601 | N06601 | B167 | 0.10 | 1.00 | - | 0.015 | 0.50 | 58.0–63.0 | 21.0–25.0 | - | 1.00 | BAL | - | 1.0–1.7 | - |
| Inconel 690 | N06690 | B167 | 0.05 | 0.50 | - | 0.015 | 0.50 | 58.0 min | 27.0–31.0 | - | 0.50 | 7.0–11.0 | - | - | - |
| Nicrofer 6025 HT | N06025 | B167 | 0.15–0.25 | 0.15 | - | 0.010 | 0.50 | BAL | 24.0–26.0 | - | - | 8.0–11.0 | 0.10–0.20 | 1.8–2.4 | - |
| Alloy 45TM | N06045 | B167 | 0.05–0.12 | 1.00 | - | 0.015 | 1.00 | 44.0–48.0 | 26.0–29.0 | - | - | BAL | 0.30–0.60 | 0.10–0.30 | - |
Mechanical Properties of ASTM B167
Mechanical properties in ASTM B167 vary by alloy, condition (hot-worked vs cold-worked annealed), and product size. Hot-worked annealed pipe over 5 in. (127 mm) OD carries lower tensile and yield requirements than smaller-diameter or cold-worked material. N06025 delivers the highest tensile strength at 98 ksi (680 MPa); N06600 and N06601 provide mid-range strength at 80 ksi (550 MPa). The table below covers all alloy/condition/size combinations.
| Grade | Condition & Size | Standard | Tensile Strength Min, MPa |
Yield Strength Min, MPa |
Elongation Min, % |
| N06600 | Hot-worked or hot-worked annealed; OD≤127mm | B167 | 550 | 205 | 35 |
| N06600 | Hot-worked or hot-worked annealed; OD>127mm | B167 | 515 | 170 | 35 |
| N06600 | Cold-worked annealed; OD≤127mm | B167 | 550 | 240 | 30 |
| N06600 | Cold-worked annealed; OD>127mm | B167 | 550 | 205 | 35 |
| N06601 | Cold-worked annealed or hot-worked annealed | B167 | 550 | 205 | 30 |
| N06690 | HW/HWA ≤5 in. OD | B167 | 85 (586) | 30 (205) | 35 |
| N06690 | HW/HWA >5 in. OD | B167 | 75 (515) | 25 (170) | 35 |
| N06690 | CWA ≤5 in. OD | B167 | 85 (586) | 35 (240) | 30 |
| N06690 | CWA ≤5 in. OD | B167 | 85 (586) | 30 (205) | 35 |
| N06603 | HWA/CWA, all sizes | B167 | 94 (650) | 43 (300) | 25 |
| N06025 | HWA/CWA, all sizes | B167 | 98 (680) | 39 (270) | 30 |
| N06045 | HWA/CWA, all sizes | B167 | 90 (620) | 35 (240) | 35 |
Note: HW = hot-worked, HWA = hot-worked annealed, CWA = cold-worked annealed.
ASTM B167 Tolerances
ASTM B167 tolerances define the allowable variations in outside diameter and wall thickness for cold-worked and hot-worked seamless Inconel pipe and tube, as detailed in the table below:
| STANDARD | OD(D) | TOLERANCE(MM) | THICKNESS(S) | TOLERANCE | LENGTH | TOLERANCE |
| MM | COMMON HIGH | MM | MM | MM | ||
| B167 (Cold-Drawn Tube) |
D<12.7 | +0.13/0 | ave. ±12.5% | min: +25.0%/0 | Cut-to-length ≤9.1m |
+3.2/0 |
| 12.7≤D≤15.9 | ±0.13 | |||||
| 15.9<D≤38.1 | ±0.13 | ave. ±10.0% | min: +20.0%/0 | |||
| 38.1<D≤76.2 | ±0.25 | ave. ±12.5% | min: +22.0%/0 | |||
| D<12.7 | ±0.13 | ave. ±12.5% | min: +25.0%/0 | Cut-to-length >9.1m |
+6.4/0 | |
| 12.7≤D≤15.9 | ±0.15 | |||||
| 15.9<D≤38.1 | ±0.19 | ave. ±10.0% | min: +20.0%/0 | |||
| 38.1<D≤50.8 | ±0.25 | ave. ±12.5% | min: +22.0%/0 | |||
| 50.8<D≤76.2 | ±0.38 | |||||
| B167 (Hot-Finished Tube) |
19≤D≤38 | +0.4/-0.8 | for nominal wall: ±12.5% | for min wall: +28.5%/0 | OD<50.8: +3.2/-0 OD≥50.8: +4.8/-0 Details refer to B829 |
- |
| 38.1<D≤102 | ±0.8 | |||||
| 102<D≤235 | +1.6/-0.8 | |||||
| B167 (Hot-Worked Pipe) |
25≤D≤48 | ±0.38 | for nominal wall: +16%/-12.5% |
for min wall: +28.5%/0 | - | - |
| 48<D≤114 | ±0.51 | |||||
| 114<D≤165 | ±0.64 | |||||
| 165<D≤235 | ±0.79 |
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ASTM B167 Alloy Grades
ASTM B167 covers six alloys: three widely specified (N06600, N06601, N06690) and three specialist grades (N06603, N06025, N06045). Inconel 600 (N06600) is a general-purpose high-nickel alloy. Inconel 601 (N06601) adds aluminium for oxidation resistance. Inconel 690 (N06690) nearly doubles the chromium for nuclear and caustic service. N06603, N06025, and N06045 include rare-earth and silicon additions for the most demanding thermal environments. The table below compares all six.
| UNS | Trade Name | Ni, % | Cr, % | Key Addition | Primary Application |
| N06600 | Inconel 600 | 72.0 min | 14.0–17.0 | None (base alloy) | General high-temp, nuclear, caustic |
| N06601 | Inconel 601 | 58.0–63.0 | 21.0–25.0 | Al 1.0–1.7% | Cyclic oxidation, carburisation |
| N06690 | Inconel 690 | 58.0 min | 27.0–31.0 | High Cr (29.5% typ) | Nuclear PWR, caustic soda |
| N06603 | — | Bal | 24.0–26.0 | Y, Zr, Ce (rare earth) | Extreme-temp thermal processing |
| N06025 | Alloy 602 CA | Remainder | 24.0–26.0 | Al 1.8–2.4, Zr, Y | Extreme oxidation >2000°F |
| N06045 | Alloy 45TM | 45.0 min | 26.0–29.0 | Si 2.5–3.0, Ce | Controlled atmosphere furnaces |
Inconel 600 pipe
Alloy 600 is a versatile nickel-chromium-iron superalloy, known for its exceptional resistance to high-temperature oxidation and various forms of corrosion. The alloy is characterised by a high nickel content (minimum 72%), which provides significant resistance to reducing environments and chloride-ion stress-corrosion cracking, while its chromium content (14–17%) ensures superior performance in oxidising conditions compared to pure nickel.
More About Inconel 600 MaterialInconel 601
Nickel Alloy 601 consists of 1.0–1.7% aluminium in the Ni-Cr-Fe base and raises chromium to 21–25%. The aluminium forms a tightly adherent Al₂O₃ sub-layer beneath the Cr₂O₃ surface oxide, creating a dual-oxide protection system. This makes 601 significantly more resistant to cyclic oxidation and carburisation than 600.
More About Inconel 601 MaterialInconel 690
Alloy 690 raises chromium to 27–31% (29.5% typical) while maintaining 58% minimum nickel. This near-doubling of chromium content (compared to the 600’s 15.5%) significantly improves resistance to primary water stress corrosion cracking (PWSCC) in nuclear PWR primary coolant, high-purity water at 600–650°F (315–343°C) with dissolved hydrogen.
Nicrofer 6025 HT
Alloy 602 CA Nicrofer 6025 HT (Alloy 602 CA, UNS N06025) is a nickel-chromium-iron-aluminium alloy strengthened with rare-earth elements such as zirconium, yttrium, and cerium. These additions improve oxide scale adhesion, reduce scaling during thermal cycling, and enhance creep strength at high temperatures. With about 24–26% chromium and 1.8–2.4% aluminium, the alloy forms a stable Al₂O₃ protective layer, allowing excellent oxidation resistance up to 1200 °C (2200 °F) in industrial furnaces and thermal processing environments.
Alloy 45TM
N06045 uses high silicon (2.5–3.0%) and cerium (0.03–0.09%) instead of aluminium for oxide protection. The silicon forms an SiO₂ sub-layer that is particularly effective in controlled-atmosphere furnaces like carburising, nitriding, and reducing gas environments where Al₂O₃-forming alloys can suffer internal oxidation. It has an elongation of 35%, a tensile strength of 90 ksi (620 MPa) and a yield strength of 35 ksi (240 MPa).
Heat Treatment Requirements for ASTM B167
ASTM B167 products are typically supplied in the annealed condition, either cold-worked annealed or hot-worked annealed, as specified by ASTM International. The recommended annealing temperatures are specified by the standard. Heat treatment requirements vary by alloy grade and are mainly based on the temperature needed to dissolve carbides and intermetallic phases. In certain high-performance alloys (such as those used in nuclear applications), an additional thermal treatment may be specified to achieve the required microstructure and service performance.
Testing and Inspection Requirements
ASTM B167 requires chemical analysis, tension testing, and hydrostatic testing on every lot. These form a three-part verification framework for high-temperature service pipe and tube.
Chemical Analysis
One test per lot (one heat). Testing follows ASTM E 1473 or E 38. Product (check) analysis tolerances follow ASTM B880. Chemical samples are taken during pouring or subsequent processing.
Tension Test
One test per lot. A lot is all material from the same heat, same nominal size (excluding length), and same condition. When not identifiable by heat, the maximum lot weight is 500 lb (227 kg). Full tubular specimens are preferred; longitudinal strip or round specimens are alternatives per ASTM E 8.
Hydrostatic Test
Each pipe or tube with an OD of 1/8 in. (3 mm) or larger and a wall thickness of 0.015 in. (0.38 mm) or over is tested to a standard hydrostatic test of 1,000 psi (6.9 MPa) max. Alternatively, by manufacturer/purchaser agreement, test pressure may be calculated as 1.5× allowable fibre stress using P = 2St/D. The manufacturer and purchaser may agree to test at 1.5× the allowable fibre stress. Any piece showing leaks is rejected.
Allowable fibre stress values by alloy and condition:
| Alloy / Condition | Fiber Stress ≤5 in. OD, psi (MPa) | Fiber Stress >5 in. OD, psi (MPa) |
| N06600, HW/HWA | 20,000 (140) | 16,700 (115) |
| N06601, HW/HWA or CWA | 20,000 (140) | 20,000 (140) |
| N06690, HW/HWA | 21,200 (146) | 16,700 (115) |
| N06690, CWA | 21,200 (146) | 21,200 (146) |
| N06603, HWA/CWA | 24,000 (165) | 24,000 (165) |
| N06025, HWA/CWA | 24,500 (169) | 24,500 (169) |
| N06045, HWA/CWA | 22,500 (155) | 22,500 (155) |
| N06600, CWA | 20,000 (140) | 20,000 (140) |
Frequently Asked Questions
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What is the Difference Between Inconel 600 and Inconel 601?
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How Does ASTM B167 Differ From ASTM B163?B167 covers general-purpose Inconel seamless pipe and tube; B163 covers condenser and heat exchanger tubes specifically. B163 includes additional surface finish, NDE, and dimensional requirements specific to condenser/heat exchanger bundles. For nuclear steam generator tubing, B163 is the typical specification (with B167 for associated piping).
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What is the ASME Equivalent of ASTM B167?ASME SB-167 is the identical specification adopted into ASME BPVC, Section II, Part B. Material produced to ASTM B167 can carry the SB-167 designation for code-stamped nuclear vessels, pressure equipment, and piping systems.
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What Welding Filler Metal Is Used for Inconel 600?For Inconel 600: ERNiCr-3 (AWS A5.14) for GTAW, ENiCrFe-2 (AWS A5.11) for SMAW. For Inconel 601: ERNiCrFe-11. For Inconel 690: ERNiCrFe-7A (FM 52M) for nuclear applications. No preheat is required for any B167 alloy. Maximum interpass temperature should be kept at or below 300°F (150°C). PWHT is generally not needed except in specific nuclear code requirements.
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Can Inconel 600 Handle Sulfuric Acid?Inconel 600 has limited sulfuric acid resistance. It is suitable only for very dilute H₂SO₄ (<5%) at moderate temperatures. For sulfuric acid service, use Incoloy 825 pipe (ASTM B423) or Alloy 20 (ASTM B729). Inconel 600’s strength lies in oxidising environments, caustic solutions, and high-temperature service, not reducing acid resistance.
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What is the Maximum Service Temperature for Inconel 601?Inconel 601 operates continuously up to approximately 2200°F (1200°C) in oxidising atmospheres. Its Al₂O₃/Cr₂O₃ dual-oxide protection system remains effective to this temperature. Above 2200°F, the protective oxides become less stable. For short-term or cyclic exposure in non-loaded applications, 601 can tolerate brief excursions above this limit.
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How Does Inconel 600 Compare to 304/316 Stainless Steel?Inconel 600 has 72% Ni vs 8–10% in 304/316, giving it complete immunity to chloride SCC at all temperatures. It also provides significantly better oxidation resistance above 1200°F (650°C), where 304 begins to scale, and 316 is limited by sigma-phase embrittlement. However, Inconel 600 is typically priced 3-5× higher than 316L stainless steel, depending on the nickel market conditions. The upgrade is justified when chloride SCC, caustic corrosion, or service temperatures above 1200°F are the design drivers.
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What is Sensitisation in Inconel 600 and How Is It Prevented?Sensitisation in Inconel 600 is the precipitation of chromium carbides (Cr₂₃C₆) at grain boundaries during exposure to 900–1400°F (480–760°C), depleting chromium from adjacent zones and creating intergranular corrosion susceptibility. It is prevented by using low-carbon heats (0.03% max C), solution annealing above 1800°F, followed by rapid cooling or, in Inconel 690’s case, using the thermal treatment (TT) to precipitate carbides in a controlled, beneficial manner.
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What is the Density of Inconel 600?Inconel 600 has a density of 0.304 lb/in³ (8.42 g/cm³), slightly heavier than Incoloy 800 pipe (0.287 lb/in³) due to its higher nickel content. Inconel 601 is lighter at 0.291 lb/in³ (8.06 g/cm³) because its higher iron and aluminium content reduces the average atomic weight. For weight-critical aerospace exhaust ducting, this 4% density difference between 600 and 601 can influence material selection.