ASTM A335 P21 — Chemical Composition & Mechanical Properties
ASTM A335 P21 is a chrome-moly alloy steel grade for seamless pipe (UNS K31545). It is also known as 3Cr-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 P21 at a glance
| Specification | ASTM A335 P21 |
|---|---|
| Material family | Chrome-moly alloy steel |
| Product form | Seamless pipe |
| UNS number | K31545 |
| Also known as | 3Cr-1Mo |
| Document | TG-MG-140 · Rev. 1 · October 2026 |
Typical service
3Cr-1Mo high-temperature piping
Heat treatment
Annealed, or normalised and tempered 675 °C min
Chemical composition of ASTM A335 P21 (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 P21
All equivalents| Standard system | Nearest equivalent grade |
|---|---|
| USA — ASTM / ASME | ASTM A335 P21 · ASME SA-335 P21 |
| USA — UNS | K31545 |
| Japan — JIS | SFVAF21A |
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 F21 |
Standards for ASTM A335 P21
All material standardsFAQ
ASTM A335 P21: common questions
What is the minimum yield strength of ASTM A335 P21?
205 MPa, with a minimum tensile strength of 415 MPa.
What is the carbon content of ASTM A335 P21?
0.05–0.15 %.
How is ASTM A335 P21 heat treated?
Annealed, or normalised and tempered 675 °C min.
What is the JIS equivalent of ASTM A335 P21?
The nearest Japanese (JIS) equivalent is SFVAF21A.
Does Teshi Group supply ASTM A335 P21?
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.
Related products, data sheets and standards
Alloy Steel Pipe
Stockist & supplier
View online · PDFTechnical data sheetWeld Neck Flange
OEM manufacturer
View online · PDFTechnical data sheetButt Weld Elbow
OEM manufacturer
View online · PDFMaterial productsChrome-Moly Alloy Steel Flanges & Fittings — F5 to F91
Grades, sizes and standards we supply
ViewMaterial productsASTM A182 F11 / F22 Alloy Steel Flanges
Grades, sizes and standards we supply
ViewMaterial productsASTM A182 F5 / F9 / F91 Alloy Steel Flanges
Grades, sizes and standards we supply
View
Ready to build to spec?
Share your drawing, bill of materials or technical requirements with the Teshi team.