Inconel 601 Flanges Manufacturer in India
UNS N06601 Flanges |
2.4851 / NiCr23Fe |
Al₂O₃ + Cr₂O₃ Oxide Protection |
601 vs 600 vs 625 vs 718 |
Furnace & Thermal Processing |
ERNiCrFe-11 Welding |
ASTM B564 / ASME B16.5
What is Inconel 601 (UNS N06601 / 2.4851)?
Inconel 601 is a nickel-chromium-aluminium alloy engineered specifically for extreme high-temperature service. It is designated UNS N06601 (ASTM/ASME), Werkstoff 2.4851 (European/DIN), and NiCr23Fe (EN 10095). It is classified as a nickel-based superalloy — not stainless steel — with a nominal composition of 60% Ni, 23% Cr, 13% Fe, and 1.3% Al. The ASTM specification for flanges and forgings is ASTM B564 (UNS N06601).
The defining feature of Inconel 601 is its 1.0–1.7% aluminium addition, which creates a highly protective Al₂O₃ (alumina) film at elevated temperatures, working in combination with the Cr₂O₃ (chromia) film provided by the 23% chromium. This dual-oxide protection mechanism gives 601 outstanding resistance to oxidation and scaling at temperatures up to 1250°C (2280°F) — significantly higher than Inconel 600 (max ~1100°C) or standard austenitic stainless steels (max ~925°C).
Tesco Steel & Engineering manufactures Inconel 601 flanges to ASTM B564, dimensioned per ASME B16.5 (½″–24″ NB) and ASME B16.47 for larger sizes, in all flange types — Weld Neck, Blind, Slip-On, Socket Weld, Threaded, and Lapped Joint — in pressure Classes 150 to 2500. All flanges are supplied with EN 10204 3.1 Mill Test Certificates.
The Aluminium Advantage: The 1.3% Al addition in Inconel 601 selectively forms a thermodynamically stable Al₂O₃ (alumina) scale at high temperatures. Alumina has extremely low oxygen diffusivity — acting as a near-impermeable barrier. Combined with the Cr₂O₃ chromia layer, this dual-oxide protection makes 601 the preferred alloy for cyclic high-temperature service (repeated heating/cooling), where oxide spallation is a major failure mode for less aluminium-bearing alloys.
Oxidation Resistance — How Al₂O₃ + Cr₂O₃ Dual Oxide Works
Inconel 600 (no Al)
Relies solely on Cr₂O₃ scale (from 16% Cr). Above 1100°C, chromia becomes volatile (CrO₃ forms), and the scale spalls during thermal cycling. Maximum effective use: ~1100°C. Under cyclic conditions, rapid metal loss occurs above 950°C.
Inconel 601 (1.3% Al)
Al₂O₃ forms beneath the Cr₂O₃ layer — alumina is thermodynamically more stable than chromia and resists spallation during thermal cycling. Combined dual-oxide scale remains protective to 1250°C in oxidising atmospheres. Ideal for cyclic furnace applications.
| Temperature Range |
Inconel 600 |
Inconel 601 |
310S SS |
Incoloy 800H |
| < 800°C |
Excellent |
Excellent |
Excellent |
Excellent |
| 800–1000°C |
Good |
Excellent |
Good–Fair |
Good |
| 1000–1100°C |
Fair–Poor |
Excellent |
Poor |
Fair |
| 1100–1200°C |
Poor |
Very Good |
Unsuitable |
Poor |
| 1200–1250°C |
Unsuitable |
Good |
Unsuitable |
Unsuitable |
| Max Continuous Temp |
~1100°C |
~1250°C |
~925°C |
~1100°C |
Chemical Composition — Inconel 601 (UNS N06601 / ASTM B564)
| Element |
Min % |
Max % |
Nominal % |
Role in Alloy |
| Nickel (Ni) |
58.0 |
63.0 |
60.0 |
Base matrix — provides corrosion resistance, ductility, and matrix stability at high temperature; resists reducing environments |
| Chromium (Cr) |
21.0 |
25.0 |
23.0 |
Forms Cr₂O₃ (chromia) protective oxide scale; higher Cr (23%) vs Inconel 600 (16%) substantially improves both oxidation and corrosion resistance |
| Iron (Fe) |
— |
Balance |
~13.0 |
Cost-reducing base element; contributes to solid-solution strengthening; lower than in stainless steels (~13% vs 65–70%) |
| Aluminium (Al) |
1.0 |
1.7 |
1.3 |
Key differentiator — forms Al₂O₃ (alumina) scale at high temperature, providing dual-layer oxidation protection with Cr₂O₃; dramatically improves resistance to cyclic oxidation and scaling above 1000°C |
| Carbon (C) |
— |
0.10 |
≤0.10 |
Controlled low to minimise grain boundary carbide precipitation during service; however, higher C than 'L' grades of stainless — PWHT not used |
| Manganese (Mn) |
— |
1.0 |
≤0.50 |
Deoxidiser during melting; controlled to preserve aluminium activity for oxide scale formation |
| Silicon (Si) |
— |
0.50 |
≤0.30 |
Minor deoxidiser; very low limit — excess Si reduces ductility and hot workability of Ni alloys |
| Sulphur (S) |
— |
0.015 |
≤0.010 |
Strictly controlled — S causes hot cracking during welding and forging; also attacks oxide scale in high-temperature service |
| Copper (Cu) |
— |
1.0 |
≤0.50 |
Residual element — unlike Monel (Ni-Cu alloy), Inconel 601 contains negligible copper; Cu is not a design element |
Mechanical Properties — Inconel 601 vs Inconel 600 vs Incoloy 800H
| Property |
Inconel 601 (B564 N06601) |
Inconel 600 (B564 N06600) |
Incoloy 800H (B564 N08810) |
310S SS (A182 F310) |
| Tensile Strength (UTS) |
515 MPa min |
550 MPa min |
450 MPa min |
515 MPa min |
| Yield Strength (0.2% PS) |
205 MPa min |
240 MPa min |
170 MPa min |
205 MPa min |
| Elongation |
30% min |
30% min |
30% min |
30% min |
| Hardness |
88 HRB max |
90 HRB max |
85 HRB max |
95 HRB max |
| Max Oxidising Temp |
1250°C |
1100°C |
1100°C |
925°C |
| ASME Material Group |
Group 3.2 |
Group 3.2 |
Group 3.3 |
Group 2.2 |
| Min Service Temp |
−196°C (cryogenic) |
−196°C |
−196°C |
−196°C |
Inconel 601 vs 600 vs 625 vs 718 — Which to Choose?
| Property |
Inconel 600 |
Inconel 601 |
Inconel 625 |
Inconel 718 |
| UNS |
N06600 |
N06601 |
N06625 |
N07718 |
| Werkstoff (EN) |
2.4816 |
2.4851 |
2.4856 |
2.4668 |
| Ni % |
72% |
60% |
58% |
52% |
| Cr % |
16% |
23% |
22% |
19% |
| Al % |
None |
1.3% |
0.4% max |
0.8% |
| Mo % |
None |
None |
9% |
3% |
| Nb % |
None |
None |
3.6% |
5.1% |
| Max Oxidising Temp |
~1100°C |
~1250°C ✓ |
~1050°C |
~705°C (strength) |
| Primary Strength |
Ni solid solution |
Cr+Al oxidation |
Mo corrosion resistance |
Nb age hardening (γ″) |
| ASTM Flanges |
B564 N06600 |
B564 N06601 |
B564 N06625 |
B637 N07718 |
| Best For |
General high-temp, nuclear |
Furnaces, cyclic heat, >1000°C |
Seawater, sour gas, cryogenic |
Gas turbines, aerospace structures |
Choose Inconel 601 When:
- Service temperature > 1000°C
- Cyclic heating and cooling (furnace duty)
- Oxidising or neutral atmosphere at high temp
- Industrial heat treatment piping
- Radiant tube or muffle furnace flanges
- Inconel 600 is underperforming above 1000°C
Consider Inconel 625 Instead When:
- High chloride or seawater corrosion (9% Mo)
- Sour gas (H₂S) service
- Cryogenic service with high toughness
- Service temp < 800°C with corrosive media
- NACE MR0175 sour service compliance needed
Inconel 601 Grade Cross-Reference
| Standard / System |
Designation |
| UNS (ASTM/ASME) | N06601 |
| ASTM Forgings (Flanges) | B564 — Grade N06601 |
| ASTM Plate / Sheet | B168 — UNS N06601 |
| ASTM Rod / Bar | B166 — UNS N06601 |
| ASTM Pipe / Tube | B167 — UNS N06601 |
| ASME Equivalent | SB-564 (ASME BPVC Section II Part B) |
| EN Werkstoff Number | 2.4851 |
| EN Full Designation | NiCr23Fe (EN 10095 — Heat-Resisting Nickel Alloys) |
| ISO Designation | NiCr23Fe (ISO 6208) |
| DIN | NiCr23Fe (DIN 17742) |
| Trade Name (Special Metals) | Inconel® 601 |
| Trade Name (VDM Metals) | Nicrofer 6023 |
| ASME Material Group | Group 3.2 |
Inconel 601 Flange Specifications (ASME B16.5)
| Inconel 601 Flanges — Available Specifications |
| Size Range | ½″ NB to 24″ NB (ASME B16.5); 26″ to 60″ NB (ASME B16.47 Series A & B) |
| Pressure Classes | Class 150, 300, 600, 900, 1500, 2500 (ASME B16.5) |
| PN Ratings | PN 6 / 10 / 16 / 25 / 40 / 64 / 100 / 160 (EN 1092-1) |
| Forging Standard | ASTM B564 Grade N06601 / ASME SB-564 |
| Dimension Standard | ASME B16.5, ASME B16.47 Series A/B, MSS SP-44, DIN 2527/2631/2632 |
| Flange Types | Weld Neck (WNRF), Blind (BLRF/BLFF/BLRTJ), Slip-On (SORF/SOFF), Socket Weld (SWRF), Threaded, Lapped Joint, Long Weld Neck (LWN), Orifice, Reducing, Spectacle Blind |
| Face Types | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ), Tongue & Groove (T&G) |
| Face Finish | 3.2–6.3 µm Ra (serrated) for RF per ASME B16.5 §6.4.4; smooth for RTJ groove (63 µin) |
| Material Certificate | EN 10204 Type 3.1 (standard); Type 3.2 (with third-party witness) |
| Dimensional Ref | ASME B16.5 Flange Dimensions → |
Welding Inconel 601 Flanges — Guidelines
| Parameter |
Recommendation |
Reason |
| Filler Metal (GTAW/TIG) |
ERNiCrFe-11 (AWS A5.14) — matching composition filler |
Maintains Ni-Cr-Al composition in weld metal; preserves high-temperature oxidation resistance of joint |
| Alternative GTAW Filler |
ERNiCr-3 (Inconel 82 wire, AWS A5.14) |
Acceptable for lower-temperature service; higher Mo content improves corrosion resistance but reduces Al content in weld |
| Filler Metal (SMAW) |
ENiCrFe-4 (AWS A5.11) |
Compatible SMAW electrode for field repairs and site welding |
| Pre-heat Temperature |
None required (ambient) |
Austenitic nickel alloys do not require pre-heat; heating would promote grain growth |
| Max Inter-pass Temperature |
150°C maximum |
Limits grain growth in HAZ and prevents hot cracking; allows time for full outgassing of residual sulphur from weld pool |
| Post-Weld Heat Treatment |
Not required for most applications |
For applications above 1050°C in service, a solution anneal at 1180°C may be specified to homogenise the HAZ microstructure |
| Shielding Gas (GTAW) |
Pure Argon |
Prevents oxidation of aluminium in weld pool; H₂ additions sometimes used to increase fluidity but not standard for 601 |
| Joint Preparation |
Mechanically cleaned; stainless steel brushes only |
Iron contamination from carbon steel tools causes pitting and local oxidation at high temperature; aluminium is sensitive to any contamination |
| Heat Input |
Low heat input; stringer beads preferred |
Ni alloys have low thermal conductivity — heat concentrates in weld zone; low heat input minimises HAZ grain coarsening |
Applications of Inconel 601 Flanges by Industry
| Industry / Application |
Specific Use Case |
Why Inconel 601 is Specified |
| Industrial Furnaces |
Radiant tubes, muffle furnace flanges, annealing box nozzles, roller hearth kiln flanges |
Continuous service at 900–1250°C in air/combustion atmosphere; Al₂O₃+Cr₂O₃ scale prevents scaling; cyclic operation compatibility |
| Heat Treatment Industry |
Furnace atmosphere gas supply flanges, quench oil return flanges, atmosphere generator outlet connections |
Repeated thermal cycles between ambient and 1100°C; 601 maintains dimensional stability and oxide integrity; no σ-phase embrittlement |
| Thermal Processing |
Cement kiln precalciner flanges, glass melting furnace burner connections, ceramic sintering kiln gas flanges |
Sustained temperatures 1000–1200°C; 601 resists scaling and maintains pressure-tight joints in high-temperature oxidising environments |
| Petrochemical — Steam Reforming |
Steam methane reformer (SMR) pigtail manifold flanges, outlet collection header connections, transfer line flanges |
Process temperatures 850–1000°C with H₂/CO/steam; high creep strength at temperature; carburisation resistance from Ni+Cr |
| Ethylene Production |
Pyrolysis furnace effluent transfer line flanges, TLE (transfer line exchanger) inlet connections |
Temperatures to 1100°C in high-temperature zone; thermal cycling during shutdown/startup; carburising atmosphere resistance |
| Gas Turbines |
Combustor liner flanges, transition duct connections, burner can flanges |
Operating temperatures 900–1200°C in oxidising combustion gases; 601's high Cr+Al provides oxidation and hot corrosion resistance |
| Power Generation |
Boiler steam superheater and reheater outlet flanges, combustion air preheater flanges |
Long-term creep resistance at 700–900°C; resistance to coal ash sulphidation and vanadium attack in heavy fuel oil boilers |
| Chemical Processing |
High-temperature nitric acid plant flanges (above 300°C), organic acid distillation column flanges |
High Cr (23%) provides excellent resistance to concentrated nitric acid (HNO₃) and organic acids at elevated temperature; inert to many oxidising environments |
| Aerospace / Defence |
Jet engine test cell high-temperature flanged ductwork, afterburner section connections, exhaust system flanges |
Intermittent service to 1200°C in jet exhaust environment; cyclic thermal loads; 601 retains mechanical strength and oxidation resistance |
Standards and Compliance — Inconel 601 Flanges
| Standard |
Scope |
| ASTM B564 (N06601) | Nickel alloy forgings — primary material standard for Inconel 601 flanges from forgings |
| ASTM B168 (N06601) | Ni-Cr-Fe alloy plate, sheet, strip — for ring and plate flanges cut from plate |
| ASTM B166 (N06601) | Nickel-chromium-iron alloy rod and bar |
| ASTM B167 (N06601) | Nickel-chromium-iron alloy seamless pipe and tube |
| ASME SB-564 | ASME equivalent of ASTM B564 — used for ASME code stamped pressure equipment flanges |
| ASME B16.5 | Pipe flanges and flanged fittings NPS ½–24 — dimensional and P-T rating standard |
| ASME B16.47 | Large diameter steel flanges NPS 26–60 — Series A (MSS SP-44) and Series B (API 605) |
| ASME BPVC Section II Part B | Material specifications for non-ferrous materials used in ASME coded pressure vessels — covers SB-564 |
| EN 10095 | Heat-resisting steels and nickel alloys — covers NiCr23Fe (2.4851) composition and properties |
| EN 1092-1 | Circular flanges for pipes, fittings and valves — European PN-rated flanges standard |
| EN 10269 | Steels and nickel alloys for fasteners with specified elevated and/or low temperature properties |
| DIN 17742 | Nickel alloys — composition and properties (NiCr23Fe / 2.4851) |
| MSS SP-44 | Steel pipeline flanges (Series A) for large bore flanges |
| ISO 9001:2015 | Quality management system — Tesco Steel & Engineering certification |
Inconel 601 Flange Types — Full Range
- Inconel 601 Weld Neck Flanges (WNRF)
- Inconel 601 Blind Flanges (BLRF)
- Inconel 601 Slip-On Flanges (SORF)
- Inconel 601 Socket Weld Flanges (SWRF)
Frequently Asked Questions — Inconel 601 Flanges
Precise technical answers to the most common questions from engineers, procurement teams, and AI search engines about Inconel 601 (UNS N06601 / 2.4851) flanges.
Inconel 601 is a nickel-chromium-aluminium alloy (NOT stainless steel) with UNS designation N06601 and European Werkstoff number 2.4851. Nominal composition: 60% Ni, 23% Cr, 13% Fe, 1.3% Al. The ASTM forging standard is ASTM B564. Its defining feature is a protective Al₂O₃ + Cr₂O₃ dual oxide scale that provides oxidation resistance to 1250°C (2280°F) — significantly higher than Inconel 600 (~1100°C) or 310S stainless steel (~925°C). Inconel is a registered trademark of Precision Castparts Corp. (formerly Special Metals).
Two key differences:
1. Aluminium addition: 601 contains 1.0–1.7% Al; 600 contains none. Al forms a protective Al₂O₃ scale at high temperature that dramatically improves oxidation resistance above 1000°C.
2. Higher Chromium: 601 has 21–25% Cr vs 14–17% in 600 — higher Cr further improves both oxidation and corrosion resistance.
Result: Max continuous service temperature 601: 1250°C vs 600: ~1100°C. For cyclic heating/cooling applications (most furnace duties), 601 is substantially superior. For applications below 1000°C or in reducing/nuclear environments, 600 may be acceptable and is typically less expensive.
Maximum continuous service temperature in oxidising atmosphere: 1250°C (2282°F).
In cyclic oxidation service: ~1200°C (due to repeated oxide spallation and re-formation).
In reducing or sulphur-containing atmospheres: limited to approximately 980–1050°C — sulphur attacks the protective oxide film.
In carburising atmospheres: limited by carbon absorption at grain boundaries — typically ~1000°C before significant metal dusting risk.
Comparison: Inconel 600 ~1100°C | Incoloy 800H ~1100°C | 310S SS ~925°C | 316L SS ~925°C (ASME maximum).
ASTM B564 (UNS N06601) — Standard Specification for Nickel Alloy Forgings. This covers forged flanges, fittings, and valve bodies in Inconel 601 composition. The ASME equivalent is ASME SB-564.
Additional standards: ASTM B168 (plate — for plate-cut flanges), B166 (rod/bar — for machined flanges), B167 (pipe/tube).
Dimensional and P-T ratings: ASME B16.5 (½″–24″ NB) and ASME B16.47 (26″–60″ NB). ASME Material Group: 3.2 — P-T ratings from Group 3.2 tables in ASME B16.5.
European equivalent:
Werkstoff 2.4851, full EN designation
NiCr23Fe per
EN 10095 (Heat-Resisting Steels and Nickel Alloys). Other equivalent designations:
- ISO: NiCr23Fe (ISO 6208)
- DIN: NiCr23Fe (DIN 17742)
- Trade names: Nicrofer 6023 (VDM/ThyssenKrupp), Pyromet 601, Alloy 601
For forgings: EN 10269 covers mechanical property requirements for nickel alloy forgings used in pressure equipment. Mill certificates are supplied per
EN 10204 Type 3.1 or 3.2.
Aluminium (1.0–1.7%) is added specifically to improve
high-temperature oxidation resistance. At elevated temperatures, Al selectively oxidises to form
Al₂O₃ (alumina) — which has:
- Extremely low oxygen diffusivity (nearly impermeable to O²⁻ ions)
- High thermodynamic stability — doesn't volatilise like CrO₃ does above ~1100°C
- Good adhesion to the Ni-Cr-Fe matrix during thermal cycling
The Al₂O₃ forms beneath the outer Cr₂O₃ layer, creating a
dual-barrier scale. This dual-layer (Al₂O₃ under Cr₂O₃) is far more protective than Cr₂O₃ alone (as in Inconel 600) — explaining why 601 can operate reliably at 1250°C in cyclic conditions where 600 fails.
Per ASTM B564 / UNS N06601:
Nickel (Ni): 58.0–63.0% (nominal 60%)
Chromium (Cr): 21.0–25.0% (nominal 23%)
Iron (Fe): Balance (~13%)
Aluminium (Al): 1.0–1.7% (nominal 1.3%) — key differentiator
Carbon (C): 0.10% max
Manganese (Mn): 1.0% max
Silicon (Si): 0.50% max
Sulphur (S): 0.015% max
Copper (Cu): 1.0% max
Note: Inconel 601 is a nickel-chromium-iron-aluminium alloy — NOT a stainless steel. It contains no molybdenum (unlike 316L or 317L) and no titanium or niobium (unlike 625 or 718).
Inconel 601 has
limited resistance to sulphur — this is its primary weakness compared to its exceptional oxidation resistance. In reducing atmospheres containing H₂S, SO₂, or sulphur vapour at temperatures above ~700°C, sulphidation attack can occur — sulphur reacts with Ni to form NiS, which disrupts the protective oxide layer.
Practical guidance:
- Oxidising SO₂/air atmospheres: generally acceptable to ~1050°C
- Reducing H₂S atmospheres above 700°C: limit use; consider Alloy HR-160 (Co-Ni alloy) or Hastelloy X
- Carburising atmospheres: 601 has moderate resistance; Alloy 602CA (N06025) is preferred for carburising above 1050°C
GTAW (TIG): ERNiCrFe-11 (AWS A5.14) — matching composition filler, preferred for high-temperature service above 1000°C. ERNiCr-3 (Inconel 82 filler) is an alternative for lower temperature or corrosive service.
SMAW: ENiCrFe-4 (AWS A5.11)
GMAW (MIG): ERNiCrFe-11
Key parameters:
- Pre-heat: None required
- Max inter-pass temp: 150°C
- PWHT: Not required (solution anneal at 1180°C may be specified for very high-temp service)
- Shielding gas: Pure Argon
- Use stainless steel wire brushes only — no iron contamination
Per ASTM B564 (N06601), annealed condition:
Tensile Strength (UTS): 515 MPa (75 ksi) minimum
Yield Strength (0.2% PS): 205 MPa (30 ksi) minimum
Elongation: 30% minimum
Hardness: 88 HRB maximum
At elevated temperature: UTS ≈ 310 MPa at 700°C; ≈ 110 MPa at 1000°C. The alloy maintains useful ductility across the full temperature range from −196°C to 1200°C. No sigma phase embrittlement occurs (unlike duplex or high-Mo austenitic stainless steels), ensuring safe operation after long-term high-temperature exposure.
