Technical note — material designation
Werkstoff 1.6358 vs 1.6354: what the two material numbers actually mean — and which one belongs on your drawing
Two register entries, one alloy — and four things that neither number tells the mill. Written for the engineer deciding what goes in the title block, and for the buyer who has to defend that decision at the technical clarification meeting.
The short answer
Werkstoff 1.6358 and Werkstoff 1.6354 are two European material-number entries for the same 18 % nickel, cobalt–molybdenum maraging steel at the 300 strength class, both cross-referenced to the EN designation X2NiCoMo18-9-5. Neither is wrong. The difference between them is provenance, not chemistry: 1.6358 is catalogued alongside the American designations, 1.6354 alongside European producer designations.
What matters far more is what both numbers leave out: melt route, product form, delivery condition and acceptance testing. A drawing that says only Material: 1.6354 is under-specified, and every mill that quotes it will price a slightly different product.
Key takeaways
- Same alloy. 1.6358 and 1.6354 are metallurgically interchangeable; both are X2NiCoMo18-9-5, commonly cross-referenced to UNS K93120, AMS 6514 and ASTM A538 Grade C.
- A material number is an index, not a specification. The last two digits of an EN 10027-2 number are a sequential registration index and encode nothing about properties.
- 1.6358 is the better ERP key. Stockists catalogue the grade under 1.6358 far more consistently; a null result for 1.6354 is usually a cataloguing artefact.
- The neighbours are not equivalent. 1.6359 is Maraging 250 (1724 MPa min. PS), 1.6356 is Maraging 350 (2345 MPa), and 1.2709 is the tool-steel and additive variant. One transposed digit changes the alloy class.
- Four omissions cost real money. Melt route, forging reduction, delivery condition and NDT class are all invisible to the material number, yet together they drive most of the spread in fatigue performance and price.
- Fix it with eight lines. Name a controlling standard first, both Werkstoff numbers second, then melt route, form, condition, testing and certificate type.
Contents
- What a Werkstoff number is — and is not
- What each number is actually attached to
- Is the chemistry different?
- The dangerous neighbours
- Four things neither number tells your supplier
- Which one belongs on your drawing
- Writing the callout so a mill can quote it
- How we handle the two numbers on a certificate
- Frequently asked questions
- References and standards
Enquiries for this alloy regularly arrive with both numbers on the same document — sometimes in the same sentence, occasionally contradicting each other between the drawing and the purchase order. The question that follows is always some version of: are these the same thing, and if not, which one do I actually need?
This note answers that from the perspective of a mill that has to convert the designation into an ingot, a forging plan and a certificate. We produce 1.6358 / 1.6354 forgings, rolled rings, bars and shafts, so the ambiguity described here reaches our desk as a technical query on a regular basis.
1. What a Werkstoff number actually is — and what it is not
European material numbers follow the structure defined in EN 10027-2, the successor to the older DIN 17007 scheme. The format is 1.XXXX: the leading 1 identifies the material as a steel, the two digits after the decimal point identify the steel group, and the final two digits are a sequential registration index.
That last point is what most drawings quietly assume away. The final digits are a serial number issued as entries are registered — they encode nothing about composition or properties. Two consecutively numbered steels can be metallurgically unrelated. Conversely, one alloy can carry two numbers, because it was registered through two different routes, in two different decades, by two different national or producer interests.
That is exactly what happened here. A Werkstoff number is an index entry in a register, not a specification. It carries no melt route, no product form, no heat-treatment condition, no test direction and no acceptance criteria. It is a filing label: extremely useful for searching a stockist's database, and insufficient on its own for buying a safety-critical forging.
2. What each of the two numbers is actually attached to
The clearest way to see the difference is to look at the company each number keeps. Across producer datasheets, distributor catalogues and the standard steel designation references, each material number is listed alongside a recognisable cluster of trade names. The two clusters overlap heavily — but they are not identical, and the pattern is informative.
| W.-Nr. | EN designation | Trade designations commonly grouped with it | US / international cross-reference |
|---|---|---|---|
| 1.6354 | X2NiCoMo18-9-5 (300 class) |
Predominantly European producer names — for example Böhler W720 and Aubert & Duval Marval 18 H | Maraging 300 · UNS K93120 · AMS 6514 · ASTM A538 Gr. C |
| 1.6358 | X2NiCoMo18-9-5 (300 class) |
Predominantly American and generic names — Maraging 300 and VascoMax® C-300 above all | Maraging 300 · UNS K93120 · AMS 6514 · ASTM A538 Gr. C |
Read the third column and the pattern is obvious. 1.6354 is the entry that European mill and forge designations cluster around, the Austrian and French producer names in particular. 1.6358 is the entry the American designation set clusters around.
In day-to-day trade this has one practical consequence worth knowing. Stockists and distributors catalogue the grade under 1.6358 more consistently than under 1.6354. If a search of your ERP or a supplier portal for 1.6354 returns nothing, that is usually a cataloguing artefact rather than a genuine availability problem. Search the EN designation instead.
Designation cross-reference lists are revised over time, and individual distributors do not always follow them. Before a first-article or safety-critical order, verify the number against a current designation reference and against the EN designation printed on the same line of the mill certificate. Never accept a four-digit number as the sole identification of the alloy.
3. Is there a real chemical difference between them?
No — not one you can act on. The EN designation itself tells you where the alloy sits: X2NiCoMo18-9-5 reads as very low carbon, nominally 18 % nickel, 9 % cobalt and 5 % molybdenum. Those four elements are what define the 300 class, and published bands for both material numbers fall inside the same window for all of them.
| Element | Range, wt % | Why it defines the class |
|---|---|---|
| Nickel (Ni) | 17.0 – 19.0 | The 18 in the designation. Forms the soft Fe-Ni martensite that transforms on air cooling. |
| Cobalt (Co) | 8.0 – 10.0 | The 9. Lowers molybdenum solubility, raising the volume of hardening precipitate. |
| Molybdenum (Mo) | 4.5 – 5.2 | The 5. Forms the Ni₃Mo phase that does the actual strengthening during ageing. |
| Carbon (C) | ≤ 0.030 | The X2. Deliberately minimised — this steel hardens by precipitation, not by carbon. |
Titanium, aluminium and the residual limits matter too, but they do not distinguish 1.6358 from 1.6354 in any way you can act on. Where a supplier publishes a narrower range under one number than the other, that is an internal aim composition, not a different alloy. For the complete composition and mechanical property tables, including ageing response and elevated-temperature data, see the grade page.
So if your question is "will 1.6354 stock meet a 1.6358 drawing?", the chemistry says yes. The paperwork question is separate, and section 6 deals with it.
4. The dangerous neighbours — where one digit costs 400 MPa
Because 1.6358 and 1.6354 are interchangeable, it becomes tempting to treat the whole 1.63xx band as loosely equivalent. It is not. The adjacent numbers are different strength classes, and a transposed digit on a purchase order is a genuine, recurring failure mode.
| W.-Nr. | EN designation | Class | Min. 0.2 % PS | Note |
|---|---|---|---|---|
| 1.6354 | X2NiCoMo18-9-5 | Maraging 300 | 1862 MPa | Subject of this note |
| 1.6358 | X2NiCoMo18-9-5 | Maraging 300 | 1862 MPa | Subject of this note |
| 1.6359 | X2NiCoMo18-8-5 | Maraging 250 | 1724 MPa | Tougher, lower strength |
| 1.6356 | X2NiCoMoTi18-12-4 | Maraging 350 | 2345 MPa | Harder, markedly lower KIc |
| 1.2709 | X3NiCoMoTi18-9-5 | Tool / additive grade | ≈1800 MPa | Powder, plate, tool blanks — not a forging spec |
1.6356 quoted as an equivalent for Maraging 300. It is not. 1.6356 belongs to the titanium-rich 18-12-4 group — the 350 class. Substituting it pushes hardness well past the NACE MR0175 ceiling and substantially reduces fracture toughness. This error appears on a number of supplier websites, and it propagates into drawings.
1.2709 stock supplied against a 1.6358 forging order. 1.2709 is the titanium-bearing tool-steel and additive-manufacturing variant. It is a close relative, widely stocked as powder and plate, and cheaper to source in small quantities — which is exactly why it gets offered. It is registered, specified and inspected under a different regime, and it should not enter a forging order written to AMS 6514.
5. Four things neither number tells your supplier
Here is the part that costs real money. Two mills can both ship material correctly certified as X2NiCoMo18-9-5, both fully compliant with the chemistry above, and deliver forgings that perform very differently in service. The register number is silent on all four variables that produce that gap.
5.1 Melt route
Air-melted, ESR and VIM+VAR double-vacuum material can all be certified against the same number and the same chemistry limits. With 18–19 % Ni, 8.5–9.5 % Co and 4.5–5 % Mo, this alloy segregates severely on conventional solidification, and cleanliness differences between melt routes show up directly in high-cycle fatigue and fracture toughness. If the purchase order is silent, the supplier is under no obligation to provide the better route.
5.2 Product form and forging reduction
"1.6358 bar" covers hot-rolled bar and open-die forged bar, and the grain-flow structures are not comparable. For rotating and downhole components, a defined minimum forging reduction ratio through section — verified by macro-etch — is what actually secures the fatigue performance. Nothing in the material number requires any of that.
5.3 Delivery condition
Solution annealed (ST, 28–32 HRC, machinable) and solution annealed plus aged (STA, 50–54 HRC) are radically different products carrying the same designation. Which one you receive — and, critically, who performs the final ageing and therefore certifies the mechanical properties — must be stated explicitly. It also determines where the test coupon is taken from.
5.4 NDT class and certificate type
Ultrasonic acceptance to ASTM A388 Class A and Class AA carry materially different yield rates, and therefore different prices. EN 10204 Type 3.1 and Type 3.2 differ by a third-party witness, additional lead time and an inspection fee. None of this is implied by the grade.
6. Which one belongs on your drawing
There is no universally correct answer, because the right number depends on which document governs your project. There is a correct method: name a controlling standard first, then list both register numbers as identification. Four common situations:
Ifthe design authority references AMS or ASTM
Make AMS 6514 (or ASTM A538 Grade C) the controlling specification and put the Werkstoff numbers in brackets as informative cross-reference. The standard, not the register entry, is then what the mill is contractually bound to.
Ifyou source in Europe and your ERP is keyed to material numbers
Use 1.6358 as the primary key — it is the entry stockists catalogue most consistently — and record 1.6354 as an accepted equivalent in the same material master. Still name the controlling standard in the specification field.
Ifyou inherited a legacy drawing that says only 1.6354
Do not reissue the drawing in a hurry. Add melt route, condition and NDT class through a change note or the purchase-order technical annex — that closes the real gap. The number itself is not the problem.
Ifyou supply against a customer or operator approved-vendor list
Reproduce whatever appears on the AVL verbatim, including its formatting, and add the other number as a cross-reference note. Approval bodies match strings; a helpful "correction" can invalidate an approval.
7. Writing the callout so a mill can quote it
Under-specified
Material: 1.6354
Every mill quotes a different product. Expect a technical query, a schedule slip, and a wide price spread that tells you nothing.
Identifies the alloy
Material: Maraging 300,
X2NiCoMo18-9-5
(W.-Nr. 1.6358 / 1.6354)
Unambiguous on what the alloy is. Still silent on how it is made and proven.
A callout that a forging mill can price accurately and a QA department can audit looks like this:
- MATERIAL
- Maraging 300 / X2NiCoMo18-9-5 W.-Nr. 1.6358 or 1.6354 — both accepted
- STANDARD
- AMS 6514 (controlling) / ASTM A538 Grade C
- MELTING
- VIM + VAR double vacuum. ESR or air melt NOT acceptable. Melt route to be declared on the MTR.
- FORM
- Open die forged, min. reduction ratio ___:1 through section
- CONDITION
- Solution annealed 816 °C ± 8 °C, air cool [ST] Ageing 482 °C ± 5 °C / 3 h, by supplier [STA]
- TESTING
- Tensile + hardness, longitudinal, from integral prolongation UT per ASTM A388, acceptance Class ___
- CERT
- EN 10204 Type 3.1 (Type 3.2 if third-party witness required)
Eight lines. It removes every one of the four ambiguities in section 5, and it is the difference between comparable quotations and a price spread you cannot interpret. Our guidance on specification writing for this alloy family is set out on the AMS 6514 forging page.
8. How we handle the two numbers on a certificate
A material test report that names only one of the two numbers creates work for somebody downstream. A European QA reader who receives a certificate headed "Maraging 300, AMS 6514" has to satisfy an auditor that it corresponds to the 1.6354 written on their drawing. An AMS-based reviewer who receives one headed "W.-Nr. 1.6358" has the mirror-image problem.
Our certificates therefore carry the EN designation, both material numbers, the controlling standard, the heat number and the declared melt route on the same page. It costs nothing to print and it removes an entire category of clarification email. If your quality system requires a specific format or a particular number in a particular field, tell us at enquiry stage rather than after the goods are made — certificates are difficult to reissue once material has shipped.
This article covers what the designations mean. For delivery ranges, dimensional capability, tolerances, full property data and enquiry details, see 1.6358 / 1.6354 / X2NiCoMo18-9-5 forging parts.
Frequently asked questions
Is 1.6358 the same material as 1.6354?
For practical procurement purposes, yes. Both register entries sit in the 18Ni cobalt–molybdenum maraging 300 family and both cross-reference to X2NiCoMo18-9-5. The difference is provenance: 1.6358 is catalogued alongside Maraging 300 and VascoMax C-300, 1.6354 alongside European producer designations. Neither number, alone, fixes melt route, product form, delivery condition or testing.
Which number should I put on the drawing?
Put a controlling standard first and the Werkstoff numbers second. A robust callout reads: Maraging 300 to AMS 6514 or ASTM A538 Grade C, X2NiCoMo18-9-5, W.-Nr. 1.6358 / 1.6354, VIM+VAR double vacuum melted, supplied solution annealed. If your ERP or an approved-vendor list is keyed to one number, use that number verbatim and list the other as an accepted equivalent.
Do the two numbers have different chemical compositions?
No. Published bands for both fall inside the same 18Ni(300) window. Where a supplier publishes a narrower range under one number than the other, that is an internal aim composition, not a different alloy. The controlling standard named in your purchase order, not the register number, sets the acceptance limits.
What is the difference between 1.6358 and 1.2709?
1.2709 is X3NiCoMoTi18-9-5, the titanium-bearing tool-steel and additive-manufacturing variant of the 18Ni300 family, supplied mainly as powder, plate and tool blanks. 1.6358 is the wrought forging and bar grade, X2NiCoMo18-9-5. They are close relatives, but they are registered, specified and inspected differently, and 1.2709 should not be substituted into a forging order written to AMS 6514.
Which numbers are Maraging 250 and Maraging 350?
1.6359 is X2NiCoMo18-8-5, the Maraging 250 class. 1.6356 is X2NiCoMoTi18-12-4, the Maraging 350 class. One transposed digit therefore moves an order between roughly 1724 MPa and 2345 MPa minimum yield, with large changes in fracture toughness and weldability. Always verify the four-digit number against the EN designation on the same line of the certificate.
Does a Werkstoff number guarantee VIM+VAR melting?
No. A material number is a register index, not a process specification. Air-melted, ESR and VIM+VAR material can all be certified against the same number and the same chemistry limits while performing very differently in fatigue. Melt route must be stated on the purchase order and declared on the material test report.
Can I accept 1.6354 stock against a drawing that specifies 1.6358?
Metallurgically, yes. Contractually, it depends on your quality system: if the drawing number is a controlled characteristic, a concession or engineering change note is normally required, however identical the material. The practical route is to write both numbers into the material master from the outset, with the controlling standard as the governing requirement.
What is the UNS equivalent of 1.6358?
1.6358 is commonly cross-referenced to UNS K93120, the 18Ni(300) maraging grade, together with AMS 6514 for bars, forgings, tubing and rings and ASTM A538 Grade C for plate. Verify the cross-reference against the mill certificate before a first-article order, because distributor catalogues are not always consistent.
References and standards
- EN 10027-2, Designation systems for steels — Part 2: Numerical system. European Committee for Standardization.
- AMS 6514, Steel, Maraging, Bars, Forgings, Tubing and Rings. SAE International. sae.org
- ASTM A538/A538M, Pressure Vessel Plates, Alloy Steel, Precipitation Hardening (Maraging), 18 Percent Nickel. ASTM International. astm.org
- ASTM A388/A388M, Ultrasonic Examination of Steel Forgings. ASTM International.
- EN 10204, Metallic products — Types of inspection documents. European Committee for Standardization.
- ANSI/NACE MR0175 / ISO 15156, Materials for use in H₂S-containing environments in oil and gas production. AMPP. ampp.org
- Publicly available producer and distributor datasheets for the 18Ni maraging grades, and standard steel designation reference works.
- Background on the alloy class: Maraging steel.
Trademarks, sources and disclaimer
Trademarks. VASCOMAX® is a registered trademark of Carpenter Technology Corporation. BÖHLER is a trademark of voestalpine BÖHLER Edelstahl GmbH & Co KG. MARVAL and DURIMPHY are trade designations of Aubert & Duval. All other product names, trademarks and registered trademarks referred to on this page are the property of their respective owners. They are used here solely for cross-identification of material designations, as permitted for nominative reference. Their use does not imply any affiliation with, sponsorship by, endorsement by, or approval from the trademark owners, nor that material supplied by Jiangsu Liangyi Co., Limited originates from them.
Standards. AMS, ASTM, EN, ISO and NACE/AMPP standards are referenced by designation only. No part of any standard is reproduced here. Purchasers must obtain current copies from the issuing body.
Data. Composition bands and mechanical values on this page are indicative figures compiled from publicly available producer and distributor datasheets and general engineering references. They are not acceptance criteria. Designation cross-references are revised over time and vary between sources. The controlling standard named in your purchase order takes precedence over anything on this page.
No warranty. This page is general technical information published for engineering guidance. It is not a specification, a certificate, a guarantee of properties, or a recommendation for any specific application. Suitability for a given service must be confirmed by the purchaser's own design authority. Jiangsu Liangyi Co., Limited accepts no liability for decisions taken on the basis of this page.
Corrections. If you believe anything on this page is inaccurate, or if you are a trademark owner with a concern about how a designation is referenced, please write to sales@jnmtforgedparts.com and we will review it promptly.
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