ASTM A234 WP9 Cl.1 — Chemical Composition & Mechanical Properties
ASTM A234 WP9 Cl.1 is a chrome-moly alloy steel grade for wrought butt-weld fittings (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 manufactures flanges and fittings in this grade.
ASTM A234 WP9 Cl.1 at a glance
| Specification | ASTM A234 WP9 Cl.1 |
|---|---|
| Material family | Chrome-moly alloy steel |
| Product form | Wrought butt-weld fittings |
| UNS number | K90941 |
| EN / W.Nr equivalent | 1.7386 |
| Also known as | 9Cr-1Mo |
| Document | TG-MG-117 · Rev. 1 · October 2026 |
Typical service
9Cr-1Mo butt-weld fittings
Heat treatment
Annealed, or normalised and tempered
Chemical composition of ASTM A234 WP9 Cl.1 (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 | 22 % |
| Hardness | 217 HBW max |
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 A234 WP9 Cl.1
All equivalents| Standard system | Nearest equivalent grade |
|---|---|
| USA — ASTM / ASME | ASTM A234 WP9 Cl.1 · ASME SA-234 WP9 Cl.1 |
| 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| UK — BS (withdrawn) | BS 3604 629 |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 |
| Seamless pipe | ASTM A335 P9 |
Standards for ASTM A234 WP9 Cl.1
All material standardsFAQ
ASTM A234 WP9 Cl.1: common questions
What is the minimum yield strength of ASTM A234 WP9 Cl.1?
205 MPa, with a minimum tensile strength of 415 MPa.
What is the carbon content of ASTM A234 WP9 Cl.1?
0.15 max %.
What is the UNS number and EN equivalent of ASTM A234 WP9 Cl.1?
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 A234 WP9 Cl.1 heat treated?
Annealed, or normalised and tempered.
What is the Chinese (GB) equivalent of ASTM A234 WP9 Cl.1?
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 A234 WP9 Cl.1?
The nearest Japanese (JIS) equivalent is STPA26 / SFVAF9.
Does Teshi Group supply ASTM A234 WP9 Cl.1?
Teshi Group manufactures flanges and fittings in this grade. Send your size, rating and quantity to info@teshigroup.com for a quotation with EN 10204 3.1 certificates.
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