P11 / T11 / F11 / 10CrMo5-5 / 1.7338 Cr-Mo Alloy Steel
P11, T11, F11 and EN 10CrMo5-5 / 1.7338 belong to the same general chromium-molybdenum alloy steel family used for elevated-temperature pressure service.
These materials contain approximately 1.0–1.5% chromium and 0.45–0.65% molybdenum, providing improved high-temperature strength, oxidation resistance and creep performance compared with conventional carbon steel.
Different grade designations are used according to product form and material standard.
Typical products include seamless pipe, boiler and heat-exchanger tube, forged flanges, forged fittings, butt-weld fittings and other high-temperature piping components.
Material Overview
| Item | Designation |
|---|---|
| Material Family | Cr-Mo Alloy Steel |
| Common Alloy Description | 1.25Cr-0.5Mo |
| ASTM A335 Pipe Grade | P11 |
| ASTM A213 Tube Grade | T11 |
| ASTM A182 Forging Grade | F11 |
| ASTM A234 Fitting Grade | WP11 |
| UNS | K11597 |
| EN Steel Name | 10CrMo5-5 |
| EN Material Number | 1.7338 |
| Main Alloying Elements | Cr, Mo |
| Typical Service | Elevated-Temperature Pressure Service |
What Is P11 Alloy Steel?
P11 is a ferritic chromium-molybdenum alloy steel used for seamless pressure pipe in elevated-temperature service.
The addition of chromium and molybdenum improves its performance compared with plain carbon steel.
Typical characteristics include:
- Good elevated-temperature strength
- Improved creep resistance
- Improved oxidation resistance
- Good pressure-service performance
- Good weldability with controlled procedures
- Suitable for refinery and steam piping
- Suitable for petrochemical and power-generation systems
P11 is commonly used where carbon steel no longer provides sufficient long-term performance at elevated temperatures.
P11, T11, F11 and WP11
The grade designation changes according to the product form.
| Product Form | Standard | Grade |
|---|---|---|
| Seamless Pipe | ASTM A335 / ASME SA-335 | P11 |
| Boiler / Heat Exchanger Tube | ASTM A213 / ASME SA-213 | T11 |
| Forged Flanges / Forged Fittings | ASTM A182 / ASME SA-182 | F11 |
| Butt-Weld Fittings | ASTM A234 / ASME SA-234 | WP11 |
These grades belong to the same general chromium-molybdenum alloy family but are governed by different product specifications.
The correct grade should therefore be selected according to the actual component being ordered.
10CrMo5-5 / 1.7338
10CrMo5-5 is a European chromium-molybdenum alloy steel designation.
Its EN material number is:
1.7338
10CrMo5-5 is used for pressure equipment and seamless tubes with specified elevated-temperature properties.
Its chemistry is similar to the ASTM P11 / T11 material family, but the ASTM and EN specifications have different manufacturing, testing and mechanical-property requirements.
For international procurement, the correct standard should always be stated rather than relying only on an equivalent-material description.
Chemical Composition
Typical chemistry for the 1.25Cr-0.5Mo alloy family is:
| Element | Typical Range |
|---|---|
| Carbon, C | 0.05–0.15% |
| Manganese, Mn | 0.30–0.60% |
| Silicon, Si | 0.50–1.00% |
| Chromium, Cr | 1.00–1.50% |
| Molybdenum, Mo | 0.44–0.65% |
| Phosphorus, P | 0.025% max |
| Sulfur, S | 0.025% max |
For EN 10CrMo5-5 / 1.7338, the chemistry is also based on approximately:
- 1.0–1.5% chromium
- 0.45–0.65% molybdenum
Actual heat chemistry should be verified against the ordered product standard and Material Test Certificate.
Effect of Chromium and Molybdenum
Chromium
Chromium contributes to:
- Oxidation resistance
- Improved hardenability
- Better elevated-temperature strength
- Improved resistance to high-temperature scaling
Molybdenum
Molybdenum contributes to:
- Improved creep resistance
- Better elevated-temperature strength
- Reduced high-temperature softening
- Improved long-term pressure performance
The combination of chromium and molybdenum is the main reason this material family is widely used in high-temperature process piping.
Mechanical Properties
Mechanical properties vary according to product standard, thickness, heat treatment and manufacturing condition.
For ASTM A335 P11 pipe, typical minimum room-temperature values include:
| Property | Typical Minimum |
|---|---|
| Tensile Strength | 415 MPa |
| Yield Strength | 205 MPa |
| Elongation | According to applicable specification |
For EN 10CrMo5-5 / 1.7338, typical room-temperature properties may include:
| Property | Typical Requirement |
|---|---|
| Tensile Strength | 410–560 MPa |
| Yield / Proof Strength | Approximately 265–275 MPa depending on thickness |
| Elongation | Approximately 20–22% depending on orientation |
Mechanical properties should always be checked against the applicable product specification.
Heat Treatment
P11-family Cr-Mo steels require controlled heat treatment.
Depending on product form and section thickness, treatment may include:
- Normalizing
- Tempering
- Normalizing and tempering
- Other permitted heat-treatment conditions
For fabricated piping systems, post-weld heat treatment may also be required depending on:
- Wall thickness
- Welding procedure
- Design code
- Service temperature
- Project specification
Heat-treatment records can be supplied when required.
High-Temperature Performance
P11 / T11 / F11 / 10CrMo5-5 materials are primarily used for elevated-temperature pressure service.
Compared with conventional carbon steel, they offer improved:
- Creep resistance
- High-temperature strength
- Oxidation resistance
- Long-term pressure-service performance
The allowable design temperature is not determined by the material name alone.
Final design conditions depend on:
- Applicable piping or pressure-vessel code
- Product form
- Material condition
- Design pressure
- Wall thickness
- Welding
- Heat treatment
- Required service life
ASTM A335 P11 Seamless Pipe
ASTM A335 P11 is used for seamless ferritic alloy-steel pipe for elevated-temperature service.
Typical applications include:
- Refinery piping
- Petrochemical piping
- Steam lines
- Boiler piping
- Power plants
- High-temperature process systems
Available dimensions can include standard and heavy-wall schedules according to project requirements.
ASTM A213 T11 Tube
ASTM A213 T11 is used for seamless alloy-steel tubes in:
- Boilers
- Superheaters
- Heat exchangers
- High-temperature thermal equipment
T11 should be specified when the product form is tube rather than pressure pipe.
ASTM A182 F11 Forged Flanges and Fittings
ASTM A182 F11 is used for forged or rolled alloy-steel piping components.
Available products can include:
- ASTM A182 F11 Weld Neck Flange
- ASTM A182 F11 Blind Flange
- ASTM A182 F11 Slip-On Flange
- ASTM A182 F11 Socket Weld Flange
- ASTM A182 F11 Threaded Flange
- Forged Fittings
- Valve Components
F11 may be supplied in different classes depending on the applicable specification and required mechanical properties.
The ordered class should be clearly stated in the purchase specification.
ASTM A234 WP11 Butt-Weld Fittings
ASTM A234 WP11 covers wrought alloy-steel fittings for moderate and elevated-temperature pressure service.
Available products include:
- 90° Elbows
- 45° Elbows
- Equal Tees
- Reducing Tees
- Concentric Reducers
- Eccentric Reducers
- Caps
These fittings are commonly used together with ASTM A335 P11 pipe in process piping systems.
EN 10CrMo5-5 / 1.7338 Products
EN 10CrMo5-5 / 1.7338 can be supplied for pressure and elevated-temperature applications under applicable EN product specifications.
Typical product forms can include:
- Seamless Tubes
- Butt-Weld Fittings
- Pressure Components
- Custom Fabricated Parts
For EN projects, the required EN product standard and inspection requirements should be stated directly.
ASTM P11 vs EN 10CrMo5-5
P11 and 10CrMo5-5 are closely related chromium-molybdenum alloy steels, but they should not automatically be treated as fully interchangeable.
| Item | ASTM P11 Family | EN 10CrMo5-5 |
|---|---|---|
| System | ASTM / ASME | EN |
| Material Type | 1.25Cr-0.5Mo | Cr-Mo Steel |
| Chromium | 1.00–1.50% | 1.00–1.50% |
| Molybdenum | 0.44–0.65% | 0.45–0.65% |
| Pipe / Tube Standard | A335 | EN 10216-2 |
| Material Number | UNS K11597 | 1.7338 |
| Main Application | Elevated-temperature pressure service | Elevated-temperature pressure service |
The chemistry is similar, but mechanical properties, testing, dimensions and certification requirements depend on the ordered standard.
P11 vs P22
P11 and P22 are both Cr-Mo steels, but P22 contains higher chromium and molybdenum.
| Item | P11 | P22 |
|---|---|---|
| Cr | 1.00–1.50% | Approximately 2.0–2.5% |
| Mo | 0.44–0.65% | Approximately 0.9–1.1% |
| Common Description | 1.25Cr-0.5Mo | 2.25Cr-1Mo |
| High-Temperature Strength | Good | Higher |
| Oxidation Resistance | Good | Higher |
Material selection should follow actual design conditions and code requirements.
Typical Applications
P11 / T11 / F11 / 10CrMo5-5 / 1.7338 materials are widely used in:
- Oil refineries
- Petrochemical plants
- Power plants
- Boiler systems
- Steam piping
- Heat exchangers
- Superheaters
- High-temperature process piping
- Pressure equipment
- Valves
- Pumps
- Thermal processing systems
Welding and Fabrication
The material can be welded using qualified welding procedures.
Important considerations include:
- Preheat
- Interpass temperature
- Welding filler metal
- Heat input
- Post-weld heat treatment
- Hardness control
- Welding procedure qualification
The applicable welding procedure should follow the design code and project requirements.
Inspection and Certification
Products can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Chemical Analysis
- Tensile Testing
- Hardness Testing
- Heat-Treatment Records
- PMI
- Dimensional Inspection
- Visual Inspection
- UT
- MT
- PT where applicable
- Hydrostatic Testing for pipe and tube
- Third-Party Inspection
- Full Heat-Number Traceability
Frequently Asked Questions
Is P11 the same as T11?
P11 and T11 have similar chromium-molybdenum chemistry but apply to different product forms.
P11 is used for ASTM A335 pipe, while T11 is used for ASTM A213 boiler and heat-exchanger tubes.
What is ASTM A182 F11?
ASTM A182 F11 is the forged-product grade used for Cr-Mo flanges, forged fittings and related pressure components.
What is 1.7338?
1.7338 is the EN material number for 10CrMo5-5 chromium-molybdenum alloy steel.
Is 11CrMo5-5 the same as 1.7338?
No. The recognized designation for material number 1.7338 is 10CrMo5-5.
Is 10CrMo5-5 equivalent to ASTM P11?
10CrMo5-5 and ASTM P11 have similar Cr-Mo chemistry and are often treated as corresponding material families for international comparison.
However, they are governed by different standards and should not be substituted without checking chemistry, mechanical properties, testing and project requirements.
What products are available in the P11 material family?
Available products can include:
- ASTM A335 P11 Seamless Pipe
- ASTM A213 T11 Tube
- ASTM A182 F11 Weld Neck Flange
- ASTM A182 F11 Blind Flange
- ASTM A234 WP11 Butt-Weld Fittings
- EN 10CrMo5-5 / 1.7338 Tubes
- Forged Components
- Custom Alloy-Steel Components
P11 / T11 / F11 / 10CrMo5-5 Products
We supply Cr-Mo alloy steel products for refinery, petrochemical, boiler, power-generation and elevated-temperature pressure applications.
Available products include:
- ASTM A335 P11 Seamless Pipe
- ASME SA213 T11 Boiler and Heat Exchanger Tube
- ASTM A182 F11 Weld Neck Flanges
- ASTM A182 F11 Blind Flanges
- ASTM A234 WP11 Elbows
- ASTM A234 WP11 Tees
- ASTM A234 WP11 Reducers
- 10CrMo5-5 / 1.7338 Pipes
- Forged Components
- Custom Alloy-Steel Parts
For quotation, please provide the product type, material standard, grade, size, wall thickness, quantity and inspection requirements.