ASTM A335 P9 — Chemical Composition & Mechanical Properties
ASTM A335 P9 is a chrome-moly alloy steel grade for seamless pipe (UNS K90941, EN / W.Nr 1.7386). It is also known as 9Cr-1Mo. This sheet summarises its chemical composition limits, minimum mechanical properties, heat treatment and typical service. Teshi Group supplies this grade as a stockist and supplier, and manufactures matching flanges and fittings.
ASTM A335 P9 at a glance
| Specification | ASTM A335 P9 |
|---|---|
| Material family | Chrome-moly alloy steel |
| Product form | Seamless pipe |
| UNS number | K90941 |
| EN / W.Nr equivalent | 1.7386 |
| Also known as | 9Cr-1Mo |
| Document | TG-MG-120 · Rev. 1 · October 2026 |
Typical service
Furnace tubes and high-temperature refinery piping
Heat treatment
Full or isothermal anneal, or normalised and tempered 675 °C min
Chemical composition of ASTM A335 P9 (weight %)
Single values are maximums unless shown as a range or “min”.
Mechanical properties
| Tensile strength, min | 415 MPa |
|---|---|
| Yield strength (0.2 % offset), min | 205 MPa |
| Elongation, min | 30 % |
| Hardness | Not specified |
About chrome-moly alloy steel
Chrome-moly steels are low-alloy steels with 1–9 % chromium and 0.5–1 % molybdenum. Chromium gives oxidation and sulphidation resistance; molybdenum gives creep strength at high temperature. They are the standard choice for steam and hot hydrocarbon service above the carbon-steel range.
Reference information compiled from the published standard for convenience. It does not replace the current edition of the governing standard, which takes precedence. Verify critical dimensions and properties before design, purchase or fabrication. Teshi Engineers & Sales Promoters (P) Ltd accepts no liability for errors or omissions.
International equivalents of ASTM A335 P9
All equivalents| Standard system | Nearest equivalent grade |
|---|---|
| USA — ASTM / ASME | ASTM A335 P9 · ASME SA-335 P9 |
| USA — UNS | K90941 |
| Europe — EN designation | X11CrMo9-1 (EN 10216-2) |
| Europe — W.Nr | 1.7386 |
| Japan — JIS | STPA26 / SFVAF9 |
| China — GB / NB | 12Cr9MoI (GB/T 9948) / 1Cr9Mo1 |
| China — old GB designation | 1Cr9Mo1 |
| UK — BS (withdrawn) | BS 3604 629 |
Equivalents are the nearest commonly cited grades. Chemistry, mechanical properties and testing differ between standards — compare them before substituting one for another.
Same alloy in other product forms
| Product form | Specification / grade |
|---|---|
| Forged flanges & fittings | ASTM A182 F9 |
| Wrought butt-weld fittings | ASTM A234 WP9 Cl.1 |
Standards for ASTM A335 P9
All material standardsFAQ
ASTM A335 P9: common questions
What is the minimum yield strength of ASTM A335 P9?
205 MPa, with a minimum tensile strength of 415 MPa.
What is the carbon content of ASTM A335 P9?
0.15 max %.
What is the UNS number and EN equivalent of ASTM A335 P9?
UNS K90941; the nearest European designation is W.Nr 1.7386. Equivalents are close but not identical — check the specification if substituting.
How is ASTM A335 P9 heat treated?
Full or isothermal anneal, or normalised and tempered 675 °C min.
What is the Chinese (GB) equivalent of ASTM A335 P9?
The nearest Chinese equivalent is 12Cr9MoI (GB/T 9948) / 1Cr9Mo1, formerly 1Cr9Mo1. Equivalents are close but not identical — compare chemistry and properties before substituting.
What is the JIS equivalent of ASTM A335 P9?
The nearest Japanese (JIS) equivalent is STPA26 / SFVAF9.
Does Teshi Group supply ASTM A335 P9?
Teshi Group supplies this grade as a stockist and supplier, and manufactures matching flanges and fittings. Send your size, rating and quantity to info@teshigroup.com for a quotation with EN 10204 3.1 certificates.
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