Material Standard
ASTM A335 Download
ASTM A335 (also known as ASME SA335) covers seamless ferritic alloy-steel pipe intended for high-temperature service in power generation, petrochemical, and refinery applications. These chrome-molybdenum (Cr-Mo) and chrome-molybdenum-vanadium (Cr-Mo-V) alloys provide excellent creep resistance, oxidation resistance, and thermal fatigue properties at elevated temperatures.
Zhengzhou Huitong (HT Pipe) supplies ASTM A335 / SA-335 compliant chrome-moly alloy steel pipes across all standard grades with full Mill Test Certificates (MTC) per EN 10204 3.1. Download the official standard PDF from our Download Center.
ASTM A335 covers seamless ferritic alloy-steel pipe in multiple grades for high-temperature service:
| Grade | Alloy Type | Max. Service Temp. | Heat Treatment |
|---|---|---|---|
| P1 | C-Mo Steel | 455°C | Normalized |
| P5 | 5Cr-0.5Mo | 550°C | Normalized & tempered |
| P9 | 9Cr-1Mo | 595°C | Normalized & tempered |
| P11 | 1.25Cr-0.5Mo | 550°C | Normalized & tempered |
| P22 | 2.25Cr-1Mo | 595°C | Normalized & tempered |
| P91 | 9Cr-1Mo-V | 650°C | Normalized & tempered (1040°C + 730-800°C) |
| P92 | 9Cr-W-Mo-V | 650°C | Normalized & tempered (1040°C + 730-800°C) |
| Designation | Issuing Body | Unit System | Dimension Standard | Latest Edition |
|---|---|---|---|---|
| ASTM A335 | ASTM International | Inch-Pound | ASME B36.10M | A335/A335M-18 |
| ASME SA-335 | ASME (BPVC Sec. II Part A) | Both | ASME B36.10M | 2023 Edition |
Values are maximum unless shown as a range. "—" = not required / not applicable. Heat analysis per ASTM A335-18.
| Grade | C% | Mn% | P% | S% | Si% | Cr% | Mo% | V% | Nb% | N% | W% |
|---|---|---|---|---|---|---|---|---|---|---|---|
| P5 | 0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.50 | 4.00-6.00 | 0.45-0.65 | — | — | — | — |
| P9 | 0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.25-1.00 | 8.00-10.00 | 0.90-1.10 | — | — | — | — |
| P11 | 0.05-0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.50-1.00 | 1.00-1.50 | 0.44-0.65 | — | — | — | — |
| P22 | 0.05-0.15 | 0.30-0.60 | 0.025 | 0.025 | 0.50 | 2.00-2.50 | 0.87-1.13 | — | — | — | — |
| P91 | 0.08-0.12 | 0.30-0.60 | 0.020 | 0.010 | 0.20-0.50 | 8.00-9.50 | 0.85-1.05 | 0.18-0.25 | 0.06-0.10 | 0.03-0.07 | — |
| P92 | 0.07-0.13 | 0.30-0.60 | 0.020 | 0.010 | 0.50 | 8.50-9.50 | 0.30-0.60 | 0.15-0.25 | 0.04-0.09 | 0.03-0.07 | 1.50-2.00 |
Note: Full chemistry ranges per ASTM A335-18 Table 1. Product analysis tolerances apply. P92 also contains 0.001-0.006% B (Boron).
All values are minimum requirements in the normalized and tempered condition. Per ASTM A335-18.
| Grade | Tensile Strength min MPa (ksi) |
Yield Strength 0.2% min MPa (ksi) |
Elong. min % |
Hardness max |
|---|---|---|---|---|
| P5 | 415 (60) | 205 (30) | 30 | — |
| P9 | 415 (60) | 205 (30) | 30 | — |
| P11 | 415 (60) | 205 (30) | 30 | — |
| P22 | 415 (60) | 205 (30) | 30 | — |
| P91 | 585 (85) | 415 (60) | 20 | 250 HBW |
| P92 | 620 (90) | 440 (64) | 20 | 250 HBW |
Note: P91 and P92 require microstructure verification (fully tempered martensite, no ferrite). Test requirements per ASTM A370.
| Grade | Chromium (%) | Molybdenum (%) | Max Temp (°C) | Primary Application |
|---|---|---|---|---|
| P1 | — | 0.44-0.65 | 455 | Low-temp/high-pressure |
| P5 | 4.00-6.00 | 0.45-0.65 | 550 | Refinery, petrochemical |
| P9 | 8.00-10.00 | 0.90-1.10 | 595 | High-temp refinery |
| P11 | 1.00-1.50 | 0.44-0.65 | 550 | Power boilers |
| P22 | 2.00-2.50 | 0.87-1.13 | 595 | Power, petrochemical |
| P91 | 8.00-9.50 | 0.85-1.05 | 650 | USC power boilers |
| P92 | 8.50-9.50 | 0.30-0.60 | 650 | USC, A-USC boilers |
| Parameter | Specification |
|---|---|
| Size Range | 1/2" - 48" (OD 21.3mm - 1219mm) |
| Wall Thickness | SCH 20 - SCH XXH |
| Application | Most common grade for power plant boilers |
| Features | Good creep strength and weldability |
| Parameter | Specification |
|---|---|
| Size Range | 1/2" - 48" (OD 21.3mm - 1219mm) |
| Features | Superior creep strength vs P11 |
| Application | Used in main steam lines and headers |
| Parameter | Specification |
|---|---|
| Size Range | 1/2" - 48" (OD 21.3mm - 1219mm) |
| Tensile Strength | min 585 MPa (ASME) |
| Features | Excellent creep resistance up to 650°C |
| Application | Widely used in Ultra-Supercritical (USC) plants |
| Parameter | Specification |
|---|---|
| Features | Higher creep strength than P91 |
| Strength | Up to 50% stronger than P91 |
| Application | Used in Advanced-USC (A-USC) plants |
| Parameter | Specification |
|---|---|
| Features | High chromium for oxidation resistance |
| Application | Preferred for refinery applications |
| Features | Good sulfur resistance |
| Feature | Description |
|---|---|
| High Temperature Strength | Maintains mechanical properties at elevated temperatures |
| Creep Resistance | Excellent long-term creep strength (critical for boiler tubes) |
| Oxidation Resistance | Chromium content provides scale resistance |
| Thermal Fatigue Resistance | Suitable for cyclic temperature operations |
| P91/P92 Benefits | Higher strength allows thinner walls, reducing weight and cost |
| Grade | Normalizing Temp (°C) | Tempering Temp (°C) |
|---|---|---|
| P5 | ≥900 | ≥700 |
| P9 | ≥900 | ≥700 |
| P11 | ≥900 | ≥675 |
| P22 | ≥900 | ≥675 |
| P91 | ≥1040 | 730-800 |
| P92 | ≥1040 | 730-800 |
| Grade | Preheat Temp (°C) | Min. Interpass Temp (°C) | PWHT Temp (°C) |
|---|---|---|---|
| P5, P9 | 150-200 | 200 | 675-750 |
| P11, P22 | 150-200 | 200 | 675-750 |
| P91 | 200-250 | 300 | 730-780 |
| P92 | 200-250 | 300 | 730-780 |
| Grade | Recommended Filler |
|---|---|
| P11 | E8018-B2, ER80S-B2 |
| P22 | E9018-B3, ER90S-B3 |
| P91 | E9018-B9, ER90S-B9 (matching composition) |
| P92 | Matching P92 or E9018-B9 filler |
| Test | Requirement | Reference Standard |
|---|---|---|
| Tensile Test | One per heat/lot | ASTM A370 |
| Flattening Test | Seamless pipe - one per end | ASTM A335 |
| Hardness Test | Brinell or Vickers | ASTM E10 / E18 |
| Hydrostatic Test | 100% of pipes | ASTM A335 |
| Microstructure Test | For P91, P92 (no prior-austenite grain boundary ferrite) | ASTM A335 |
| Impact Test | When specified (typically for P91/P92) | ASTM A370 |
For ASTM A335 P91 and P92, microstructure is critical for long-term creep strength:
| Requirement | Specification |
|---|---|
| Fully Tempered Martensite | Required microstructure |
| Prior Austenite Grain Size | ASTM 5 or finer (no coarse grain) |
| No Ferrite or Delta Ferrite | Not permitted |
| No Laves Phase | Precipitation controlled |
| Industry | Recommended Grades | Typical Pipe Sizes & Schedules |
|---|---|---|
| Power Generation | P11, P22, P91, P92 | NPS 2 - NPS 24; Sch 40-160 |
| Refinery and Petrochemical | P5, P9, P11, P22 | NPS 1 - NPS 20; Sch 40-80 |
| Oil and Gas | P11, P22 | NPS 2 - NPS 16; Sch 40-80 |
| Standard | Scope | Relationship to A335 |
|---|---|---|
| ASTM A213 | Seamless Ferritic and Austenitic Alloy-Steel Boiler Tubes | Tube version of A335 (smaller diameters) |
| ASTM A234 | Wrought Carbon and Alloy Steel Fittings | Compatible fittings for A335 pipe |
| ASTM A369 | Carbon and Alloy Steel Forged and Bored Pipe | Forged alternative to seamless A335 |
| ASME B31.1 | Power Piping Code | Governs design of A335 piping in power plants |
A: P11 has 1.25% Cr + 0.5% Mo; P22 has 2.25% Cr + 1% Mo. P22 has superior creep strength and is used for higher temperature/pressure applications. P11 is more economical for moderate conditions.
A: P91 offers ~50% higher tensile strength than P11/P22, allowing thinner walls. This reduces material costs, improves heat transfer, and enables higher operating temperatures (up to 650°C) for better plant efficiency.
A: No. P91 must be welded with matching or over-matched filler (E9018-B9 or ER90S-B9). Using P22 filler will result in a weaker weld with inferior creep properties.
A: ASTM A335 P91 is certified up to 650°C (1202°F) for creep rupture strength. However, actual design temperature depends on pressure, desired life, and code requirements (ASME B31.1, Section I).
A: Post-weld heat treatment at 730-780°C is essential to temper the hard martensite in the weld heat-affected zone (HAZ). Without proper PWHT, the HAZ will be excessively hard and susceptible to cracking.
The official ASTM A335/A335M-18 PDF is available from our HT Pipe Download Center. The document includes full chemical composition requirements, mechanical property tables, heat treatment specifications, and testing requirements.