ASTM A234 WP1 — Chemical Composition & Mechanical Properties
ASTM A234 WP1 is a chrome-moly alloy steel grade for wrought butt-weld fittings (UNS K12821, EN / W.Nr ≈ 1.5415 (16Mo3)). It is also known as C-½Mo. 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 WP1 at a glance
| Specification | ASTM A234 WP1 |
|---|---|
| Material family | Chrome-moly alloy steel |
| Product form | Wrought butt-weld fittings |
| UNS number | K12821 |
| EN / W.Nr equivalent | ≈ 1.5415 (16Mo3) |
| Also known as | C-½Mo |
| Document | TG-MG-143 · Rev. 1 · October 2026 |
Typical service
Carbon-moly butt-weld fittings for P1 piping
Heat treatment
Annealed, normalised and tempered, or quenched and tempered
Chemical composition of ASTM A234 WP1 (weight %)
Single values are maximums unless shown as a range or “min”.
Mechanical properties
| Tensile strength, min | 380 MPa |
|---|---|
| Yield strength (0.2 % offset), min | 205 MPa |
| Elongation, min | 22 % |
| Tensile strength, max | 550 MPa |
| Hardness | 197 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 WP1
All equivalents| Standard system | Nearest equivalent grade |
|---|---|
| USA — ASTM / ASME | ASTM A234 WP1 · ASME SA-234 WP1 |
| USA — UNS | K12821 |
| Europe — EN designation | 16Mo3 |
| Europe — W.Nr | 1.5415 |
| Japan — JIS | STPA12 / SFVAF1 |
| China — GB / NB | 15MoG / 20MoG (GB/T 5310) |
| China — old GB designation | 16Mo |
| UK — BS (withdrawn) | BS 3059-2 243 |
Equivalents are the nearest commonly cited grades. Chemistry, mechanical properties and testing differ between standards — compare them before substituting one for another.
Standards for ASTM A234 WP1
All material standardsFAQ
ASTM A234 WP1: common questions
What is the minimum yield strength of ASTM A234 WP1?
205 MPa, with a minimum tensile strength of 380 MPa.
What is the carbon content of ASTM A234 WP1?
0.28 max %.
What is the UNS number and EN equivalent of ASTM A234 WP1?
UNS K12821; the nearest European designation is W.Nr ≈ 1.5415 (16Mo3). Equivalents are close but not identical — check the specification if substituting.
How is ASTM A234 WP1 heat treated?
Annealed, normalised and tempered, or quenched and tempered.
What is the Chinese (GB) equivalent of ASTM A234 WP1?
The nearest Chinese equivalent is 15MoG / 20MoG (GB/T 5310), formerly 16Mo. Equivalents are close but not identical — compare chemistry and properties before substituting.
What is the JIS equivalent of ASTM A234 WP1?
The nearest Japanese (JIS) equivalent is STPA12 / SFVAF1.
Does Teshi Group supply ASTM A234 WP1?
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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