Why Do Two Werkstoffnummer Codes Exist for One Alloy?
If you have ever received a quotation listing 2.4951 when your drawing specifies 2.4630 — or vice versa — you are far from alone. The query reaches our technical team several times a week from procurement engineers across Europe, the Middle East, and Southeast Asia. On its surface the discrepancy looks like a supplier substituting a different material. In reality it is the straightforward consequence of how European metallurgical standards evolved across five decades.
The alloy in question — an 80/20 nickel-chromium base with a controlled titanium addition — was catalogued under two separate Werkstoffnummer codes during successive revision cycles of the German and European standards. When EN 10095:1999 was published as the consolidated heat-resistant steels and nickel alloys standard, both legacy codes were carried forward into the same normative table, mapped to identical composition limits and identical property requirements. The result is two official numbers that describe, without ambiguity, a single specification.
"Neither designation signals a tighter or looser tolerance band. The element ranges, heat treatment conditions, and acceptance criteria listed in the standard are word-for-word identical for both 2.4951 and 2.4630."
How 2.4951 and 2.4630 Came to Co-Exist
Understanding why two codes exist requires a brief look at the evolution of European materials standards from the mid-twentieth century to today.
Post-war industrial reconstruction drives rapid demand for high-temperature turbine materials. Nickel-chromium alloys with titanium stabilisation emerge as the leading solution for furnace hardware and combustion equipment.
The German Werkstoffnummer system assigns 2.4951 to NiCr20Ti under the original DIN catalogue. British standards assign parallel HR-series designations (HR5, HR203, HR403). Special Metals Corporation registers the trade name Nimonic® 75 for the same composition.
A secondary catalogue revision introduces 2.4630 as an alternative reference for the same base composition. Neither code is retired; both remain active in European industry documentation and project specifications.
EN 10095:1999 — Heat Resisting Steels and Nickel Alloys — is published as the pan-European harmonised standard. Both 2.4951 and 2.4630 appear in Table 2 under the same normative row for NiCr20Ti, formally confirming their complete equivalence.
New project specifications increasingly use 2.4951 as the primary code. 2.4630 persists on legacy engineering drawings, older project specifications, and repeat orders in the nuclear and petrochemical sectors. Both remain fully normatively valid.
What EN 10095:1999 Actually Specifies for Each Code
The clearest proof of interchangeability is to look at the standard's normative table. Every row below is identical because both designations share a single normative entry in EN 10095:1999.
| Attribute | 2.4951 | 2.4630 | Result |
|---|---|---|---|
| Chemical name | NiCr20Ti | NiCr20Ti | IDENTICAL |
| Governing standard | EN 10095:1999 | EN 10095:1999 | IDENTICAL |
| Ni content (wt%) | 65.4 – 81.7 | 65.4 – 81.7 | IDENTICAL |
| Cr content (wt%) | 18.0 – 21.0 | 18.0 – 21.0 | IDENTICAL |
| Ti content (wt%) | 0.2 – 0.6 | 0.2 – 0.6 | IDENTICAL |
| C content (wt%) | 0.08 – 0.15 | 0.08 – 0.15 | IDENTICAL |
| Fe max (wt%) | 5.0 | 5.0 | IDENTICAL |
| Co max (wt%) | 5.0 | 5.0 | IDENTICAL |
| Tensile strength (UTS) | ≥ 650 MPa | ≥ 650 MPa | IDENTICAL |
| 0.2% proof strength | ≥ 240 MPa | ≥ 240 MPa | IDENTICAL |
| Elongation A5 | ≥ 30% | ≥ 30% | IDENTICAL |
| Solution anneal | 1050–1150°C + WQ/RAC | 1050–1150°C + WQ/RAC | IDENTICAL |
| UNS equivalent | N06075 | N06075 | IDENTICAL |
| Max service temperature | 1100°C continuous | 1100°C continuous | IDENTICAL |
| MTC interchangeability | Either designation is accepted by standards bodies, inspection agencies, and project authorities | YES | |
| Typical usage trend | New project specifications | Legacy drawings & repeat orders | CONTEXT ONLY |
Both codes occupy a single normative row in the standard. You are not specifying a stricter or looser material depending on which Werkstoffnummer appears — the element windows and property floors are completely identical. For the full composition table, high-temperature mechanical property curves from room temperature to 1000°C, and a complete international standards cross-reference, see the 2.4951 / 2.4630 / NiCr20Ti technical data sheet.
NiCr20Ti Designations Across Global Standards Systems
Because NiCr20Ti has been in industrial service for over seventy years, it carries designations across many national and commercial standards. All of the codes below refer to the same base alloy. When your specification calls out any of these designations, the underlying material requirement is equivalent.
| Standard System | Designation | Scope / Document |
|---|---|---|
| EN / DIN (primary) | 2.4951 · NiCr20Ti | Preferred in current European project specifications; EN 10095:1999 |
| EN / DIN (secondary) | 2.4630 · NiCr20Ti | Common on legacy drawings and nuclear-sector documents; EN 10095:1999 |
| UNS (USA) | N06075 | ASTM / ASME cross-reference; used for North American documentation |
| British Standard | HR5 · HR203 · HR403 · HR504 | BS 3076 (bar), BS 3072 (sheet) |
| AMS (Aerospace) | AMS 5683 · AMS 5651 | Bar and sheet/strip forms; aerospace qualification documents |
| Proprietary trade name | Nimonic® 75 | Registered trademark of Special Metals Corporation (AMETEK); metallurgically equivalent |
| ISO chemical name | NiCr20Ti | Descriptive chemical designation used across all above standards |
Nimonic® 75 is the proprietary trade name for NiCr20Ti, registered by Special Metals Corporation. When ordering from a forging manufacturer that is not the trademark holder, the material is correctly specified by its EN designation (2.4951 or 2.4630) or UNS number (N06075). The metallurgy is identical.
What to Accept on a Material Test Certificate
The dual designation creates real friction at the inspection stage. A heat is cast to one composition, but the mill may issue the MTC listing 2.4951 while the purchase order calls out 2.4630. Quality engineers encountering this for the first time sometimes raise it as a non-conformance — unnecessarily.
When Both Designations Appear on the MTC
The best-practice format from reputable manufacturers lists both numbers — for example, "2.4951 / 2.4630 NiCr20Ti per EN 10095:1999". This confirms the supplier understands the dual-designation history. Accept without query.
When Only One Designation Appears
A certificate showing only 2.4951 satisfies a purchase order written to 2.4630 — and vice versa — provided the reported chemistry and mechanical test results comply with EN 10095:1999 limits. A cross-reference note is good practice but not a normative requirement.
MTC Acceptance Checklist — 8 Points to Verify
- Designation:
2.4951and/or2.4630with reference to EN 10095:1999 - Heat/lot number fully traceable to the melt
- Ladle chemistry within EN 10095 Table 2 limits: Ni, Cr, Ti, C, Fe, Co, Mn, Si, Cu, Al, P, S all reported
- Mechanical test results: UTS ≥ 650 MPa · Rp0.2 ≥ 240 MPa · A5 ≥ 30%
- Heat treatment record: solution annealed at 1050–1150°C + water quench or rapid air cool
- Test piece location and direction reported per EN 10002-1
- EN 10204 3.1 signature from manufacturer's authorised inspector (for 3.2 requirements, third-party inspection must be arranged separately with an approved independent body)
- NDT results if required — UT per EN 10228-3 Class 3 or 4 for critical forging applications
Nuclear, offshore, and some aerospace project specifications impose requirements tighter than EN 10095 alone — for example, capping cobalt at 0.1 wt% to control neutron activation in nuclear service. In those cases, the Werkstoffnummer alone does not guarantee compliance. Always check whether a Supplementary Material Specification (SMS) applies to your project before accepting an MTC on designation match alone.
When placing a purchase order, Jiangsu Liangyi can supply 2.4951 / 2.4630 NiCr20Ti forgings with EN 10204 3.1 Material Test Certificates covering all eight checklist points above.
Which Designation Should You Specify?
For new engineering projects, write 2.4951 / NiCr20Ti per EN 10095:1999. This is the current preferred usage in European project specifications and is unambiguous for any global supplier. Including the chemical name alongside the Werkstoffnummer removes residual doubt about intent.
If your organisation holds legacy documentation referencing 2.4630, there is no technical reason to revise existing drawings. The material you receive — provided the MTC values sit within EN 10095 limits — performs identically in every engineering respect.
For international projects involving American or British counterparts, add UNS N06075 to the purchase document alongside the Werkstoffnummer. This eliminates translation ambiguity for ASME and BS documentation.
Decision Guide — Scenario → Recommended Practice
2.4951 / NiCr20Ti / EN 10095:19992.4951 MTCs without revision or waiverUNS N06075 to the PO line item2.4951 / 2.4630 Forgings from Jiangsu Liangyi
Jiangsu Liangyi manufactures open die forgings and seamless rolled rings in 2.4951 / 2.4630 / NiCr20Ti from 30 kg to 30,000 kg. Available forms include forged round bars up to 2,000 mm diameter and seamless rolled rings up to 6,000 mm OD. All forgings are supplied with EN 10204 3.1 Material Test Certificates referencing EN 10095:1999.
Applications served include gas turbine and steam turbine components, industrial furnace radiant tubes and retorts, nuclear power structural hardware, and petrochemical reformer equipment.
Frequently Asked Questions
2.4951 and 2.4630 designate the same NiCr20Ti alloy under EN 10095:1999 with identical chemical composition, mechanical properties, and heat treatment requirements. Either Werkstoffnummer is fully valid on a Material Test Certificate.2.4951 satisfies a purchase order written to 2.4630 without any deviation or waiver, provided the reported chemistry and mechanical results comply with EN 10095:1999 limits. The reverse is equally true. No additional documentation is required.2.4951 and 2.4630 were retained in the same normative table, formalising their equivalence. Neither code was retired.2.4951 and 2.4630 correspond to UNS N06075. For international projects requiring ASME or BS documentation, add N06075 alongside the Werkstoffnummer on the purchase order to avoid translation ambiguity.2.4951 and 2.4630.2.4951 or 2.4630 per EN 10095:1999, or UNS N06075.2.4951 / 2.4630 (NiCr20Ti) has a maximum continuous service temperature of 1100°C in oxidising atmospheres. The 18–21 wt% chromium content forms a self-healing Cr₂O₃ oxide scale that provides oxidation protection up to this limit. For sustained stress-bearing applications above 815°C, precipitation-hardened superalloys such as Nimonic 80A or Waspaloy are preferred.Need 2.4951 / 2.4630 Forgings for Your Project?
ISO 9001:2015 Certified · EN 10204 3.1 MTCs · 30 kg to 30,000 kg · Ships to 50+ Countries
Open die forgings & seamless rolled rings — bars to 2,000 mm Ø, rings to 6,000 mm OD
Jiangsu Liangyi Co., Limited · Jiangyin, Jiangsu, China · Est. 1997
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