Inconel 600 vs 625 Steel Pipe: A Complete Superalloy Grade Comparison Guide
Inconel 600 vs 625 Steel Pipe: A Complete Superalloy Grade Comparison Guide
Both Inconel 600 and Inconel 625 tubing are nickel-chromium high-temperature alloys, offering excellent high-temperature and corrosion resistance. However, due to the addition of molybdenum and niobium, Inconel 625 tubing exhibits higher strength and greater corrosion resistance in corrosive chemicals and marine environments. For applications that do not require the extreme performance of Inconel 625 tubing, Inconel 600 tubing is more cost-effective.
What grade is Inconel 625 pipe?
Typically, this cold-worked Inconel 625 seamless pipe is supplied in two conditions: Grade 1 and Grade 2. ASTM B444 UNS N06625 Grade 1 pipe is supplied in the annealed condition, while Grade 2 pipe is supplied in the solution-annealed condition.
Inconel 600: Basic Nickel-Chromium-Iron Alloy
Inconel 600 tubing is a high-quality nickel-chromium-iron alloy designed for extremely harsh applications. This alloy offers excellent heat and corrosion resistance, with a nickel content of at least 72%, typically 72% to 76%. Its nickel alloy composition effectively prevents corrosion from both organic and inorganic substances, and resists chloride stress corrosion cracking. These properties make Inconel 600 a reliable choice for high-temperature, high-purity systems such as nuclear reactors and chemical processing units.
Inconel 625: Molybdenum-Niobium Superalloy
Inconel 625 tubing is a refined version of the nickel-chromium alloy, strengthened by the addition of significant amounts of molybdenum (Mo) and niobium (Nb, or niobium tungsten). The chromium content in 625 alloy tubing (20-23%) is also higher than in 600 alloy tubing (14-17%), which improves its oxidation resistance and overall resistance to oxidizing conditions at higher temperatures.
Equivalent Grades of Inconel Alloy 600/625 Tubes
| STANDARD | WERKSTOFF NR. | UNS | JIS | BS | GOST | AFNOR | EN |
| Inconel 600 | 2.4816 | N06600 | NCF 600 | NA 13 | МНЖМц 28-2,5-1,5 | NC15FE11M | NiCr15Fe |
| Inconel 625 | 2.4856 | N06625 | NCF 625 | NA 21 | ХН75МБТЮ | NC22DNB4M | NiCr22Mo9Nb |
Chemical Composition of Inconel Alloy 600/625 Tubes
| Grade | C | Mn | Si | S | Cu | Fe | Ni | Cr |
| Inconel 600 | 0.15 max | 1.00 max | 0.50 max | 0.015max | 0.50 max | 6.00 – 10.00 | 72.00 min | 14.00 – 17.00 |
| Inconel 625 | 0.10 max | 0.50 max | 0.50 max | 0.015 max | - | 5.0 max | 58.0 min | 20.0 - 23.0 |
Inconel Alloy 600/625 Pipes Mechanical Properties
| Element | Density | Melting Point | Tensile Strength | Yield Strength (0.2%Offset) | Elongation |
| Inconel 600 | 8.47 g/cm3 | 1413 °C (2580 °F) | Psi – 95,000 , MPa – 655 | Psi – 45,000 , MPa – 310 | 40 % |
| Inconel 625 | 8.4 g/cm3 | 1350 °C (2460 °F) | Psi – 1,35,000 , MPa – 930 | Psi – 75,000 , MPa – 517 | 42.5 % |
Why does Alloy 625 pipe outperform Alloy 600 pipe under high stress conditions?
The difference in alloy composition gives this advanced grade of alloy a significant advantage in mechanical properties. These mechanical properties are crucial when selecting materials for high-pressure, high-stress piping systems.
| Property (Annealed) | Inconel 600 (UNS N06600) | Inconel 625 (UNS N06625) Grade 1 | Design Implication |
| Min. Tensile Strength | 655 MPa (95,000 psi) | 827 MPa (120,000 psi) | 625 can handle substantially higher maximum loads and pressure. |
| Min. Yield Strength | 310 MPa (45,000 psi) | 414 MPa (60,000 psi) | Higher allowable design stress per pressure vessel codes. |
| Max Structural Service Temp | Up to 1900°F (1038°C) | Up to 1800°F (982°C) | 600 has better oxidation resistance; 625 has better sustained strength. |
| Creep Resistance | Moderate | Very Good | 625 is superior for long-term, sustained thermal-stress applications. |
The higher minimum tensile and yield strength of Alloy 625 tubing allows system designers and developers to use thinner walls while meeting the necessary pressure carrying capacity and safety factor requirements of various specifications, such as ASME B31.3. This is crucial in weight-sensitive industries such as aerospace, where Inconel tubing needs to be both strong and lightweight.
Summary
For applications requiring high strength, high mechanical loads, and excellent corrosion resistance (including highly corrosive, acidic, or saltwater environments), choose Inconel 625 tubing. It is the standard material for marine engineering, aerospace engine components, and chemical equipment.
For more general high-temperature applications where cost is a primary consideration and the extreme corrosion resistance characteristic of Inconel 625 tubing is not required, choose Inconel 600 tubing. Common applications include heat exchanger components, furnaces, and general refining equipment.
Why Choose Gnee as Your Nickel-Based Alloy Supplier
✅ Over 18 years of export experience, products sold to more than 80 countries
✅ Certified by ISO, SGS, and BV
✅ Global inventory of Inconel, Hastelloy, Incoloy, and Monel alloy tubing, plates, and bars
✅ Custom processing services available – including cutting, polishing, CNC machining, and packaging
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📦 Packaging and Shipping
All stainless steel products are packaged using the following methods:
Wooden pallets or crates
Moisture-proof packaging
Labels with furnace number, standard, and size labels
Shipped worldwide by sea, air, or express
Gnee Steel also supplies custom Inconel 600 products in various sizes and specifications. Please send us your drawings for a quote!
Gnee Steel is a supplier of Inconel 600 alloy, offering a wide range of products including: seamless pipe (sizes: 4-219 mm; thickness: 0.5-20 mm); welded pipe (sizes: 5.0-1219.2 mm; thickness: 0.5-20 mm); plates (thickness: 0.1 to 100 mm; width: 10-2500 mm); strips; alloy round bars (diameter: 3-800 mm); flat bars (thickness: 2-100 mm; width: 10-500 mm); hexagonal bars (size: 2-100 mm); wire rods; and extruded profiles. We collaborate with steel mills to provide our customers with Inconel 600 alloy products that meet or exceed numerous leading industry standards, including ASTM, ASME, SAE, AMS, ISO, DIN, EN, and BS standards.
Gnee Steel stocks and sells Inconel 600, pipes, plates, strips, round bars, flat bars, forged billets, hexagonal steel, wire rods, and extruded profiles. Please feel free to contact us at ss@gneesteel.com for a quote.
