UNS N06625: Expert Guide to Inconel 625 Standards & Certification (2025)
Table Of Content
Table Of Content
The Expert's Guide to UNS N06625: Inconel 625 Standards and Certification Explained
What is UNS N06625?
UNS N06625 is the official Unified Numbering System name for the high-performance nickel-chromium-molybdenum alloy known as Inconel 625. It stands out for its strong resistance to corrosion, high strength, and reliable performance in both very cold and very hot temperatures. This guide explains the numbering system, outlines the important standards that control its quality, and shows what real material certification means for engineers and buyers.
Understanding the UNS
The Unified Numbering System (UNS) is the main way to label alloys in North America, run jointly by ASTM International and SAE International. Its purpose is simple yet vital for industry accuracy.
- It removes confusion caused by multiple trade names and brand designations for the same alloy.
- It provides a single cross-reference, connecting various international standards and material specs.
- It creates an organized way to identify metals where the prefix letter shows the metal family.
The "N" in N06625 shows it is a Nickel alloy, instantly telling you its main element.
Decoding UNS N06625
The specific rules in the uns number for inconel 625 specs are what ensure the material will perform as expected. These standards define the exact chemical makeup and strength properties.
This versatile superalloy, Inconel 625, works hard in the toughest settings, from planes to chemical plants. Its special qualities come directly from its carefully controlled mix of metals.
Table 1: Chemical Composition (ASTM B443/B446)
| Element | Weight % |
|---|---|
| Nickel (Ni) | 58.0 min |
| Chromium (Cr) | 20.0 - 23.0 |
| Molybdenum (Mo) | 8.0 - 10.0 |
| Niobium (Nb) + Tantalum (Ta) | 3.15 - 4.15 |
| Iron (Fe) | 5.0 max |
| Carbon (C) | 0.10 max |
Table 2: Typical Mechanical Properties (Annealed)
| Property | Imperial (psi) | Metric (MPa) |
|---|---|---|
| Tensile Strength (Ultimate) | 120,000 - 140,000 | 827 - 965 |
| Yield Strength (0.2% Offset) | 60,000 - 80,000 | 414 - 552 |
| Elongation in 2" | 30 - 50% | 30 - 50% |
Data comes from trusted industry sources like the HAYNES® 625 alloy data sheet.
Cornerstone Quality Standards
For UNS N06625 to meet requirements, it must be made, tested, and delivered according to specific world-recognized standards. ASTM International provides the most common rules for various product forms.
Getting material that meets the right standard is a must for ensuring it works safely in critical uses.
Table: Key ASTM Standards for Inconel 625 (UNS N06625)
| Standard | Product Form | Brief Description |
|---|---|---|
| ASTM B443 | Plate, Sheet, and Strip | Covers dimensions, tolerances, and properties for flat-rolled products. |
| ASTM B444 | Seamless Pipe and Tube | Specifies requirements for seamless tubular products for corrosive service. |
| ASTM B446 | Rod, Bar, and Wire | Defines the standards for solid round, flat, or shaped bars and wire. |
| ASTM B366 | Fittings | Covers factory-made wrought buttwelding fittings. |
| ASTM B564 | Forgings | Specifies requirements for forged components like flanges and custom shapes. |
For special industries, other standards like AMS (Aerospace Materials Specifications) are often needed to meet the strict demands of aircraft and space uses.
What "Certified" Means
Certification is much more than just a simple label. It is a written guarantee that the material you get meets every requirement of the specified standard.
This paperwork gives the proof needed for quality assurance and tracking.
Certified material ensures:
- Chemical Analysis: Proof that the metal's makeup falls within the narrow, acceptable ranges. The final microstructure and mechanical properties directly depend on this exact chemistry.
- Mechanical Testing: Verification that the material provides the required strength and flexibility after correct heat treatment (e.g., solution annealing).
- Traceability: A documented path from the original furnace melt to the final product. This appears on a Material Test Report (MTR), often called a 3.1 Certificate per EN 10204.
- Corrosion Resistance: For certain uses, documents may confirm specific corrosion tests were passed, sometimes measured by its high Pitting Resistance Equivalent Number (PREN).
How to Verify Certification
When checking a supplier for Inconel 625, here is the list our quality engineers use to examine the Material Test Report (MTR). This prevents accepting fake or non-compliant material.
- Check the Standard: Does the MTR clearly state the correct ASTM standard (e.g., ASTM B446 for bar stock)?
- Verify the UNS Number: Does the report identify the material as UNS N06625?
- Confirm Traceability: Is there a unique Heat Number or Lot Number that connects the report to the physical material?
- Review Chemical Analysis: Compare the listed percentages of Ni, Cr, Mo, and Nb to the ranges required by the standard. All elements must be within spec.
- Examine Mechanical Properties: Do the reported strength and flexibility values meet or exceed the minimum requirements of the standard?
- Note Heat Treatment: The report should state the final heat-treated condition, typically "Annealed" or "Solution Annealed."
- Confirm Manufacturer: The MTR must identify the original producing mill. A trustworthy supplier will always provide the original mill's MTR.