What is the composition of P11 material

P11 is a chromium-molybdenum (Cr-Mo) low-alloy steel, with its main alloying elements including approximately 1.25% chromium (Cr) and 0.5% molybdenum (Mo), along with elements such as carbon (C), silicon (Si), and manganese (Mn). Chromium imparts excellent corrosion and oxidation resistance, while molybdenum enhances high-temperature strength and creep resistance. The synergistic effect of these elements gives P11 its superior overall performance.

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Alloy Steel Grade P11 Pipes Chemical Composition

Alloy Steel P11	C	Cr	Mn	Mo	P	S	Si
	0.05 – 0.15	1.00 – 1.50	0.30 – 0.60	0.44 – 0.65	0.025 max	0.025 max	0.50 – 1.00

•  Carbon (C) 0.05%-0.15%: Ensures basic strength while controlling weld sensitivity
•  Chromium (Cr) 1.00%-1.50%: Improves high-temperature oxidation resistance and corrosion resistance
•  Molybdenum (Mo) 0.44%-0.65%: Enhances high-temperature creep resistance and temper brittleness resistance
•  Manganese (Mn) 0.30%-0.60%: Deoxidizer and solid solution strengthening element
•  Silicon (Si) 0.50%-1.00%: Improves casting fluidity and high-temperature stability
•  Phosphorus (P) ≤0.025%, Sulfur (S) ≤0.025%: Strictly controls impurity content

 

Special requirements include:

1. Residual element copper (Cu) ≤0.25%

2. Vanadium (V) + Titanium (Ti) + Zirconium (Zr) ≤0.15%

3. Both smelting analysis and finished product analysis reports are required.

 

A335 P11 Alloy steel pipe Production Process and Key Technical Points

1. Smelting and Continuous Casting
Electric arc furnace or converter smelting is used. Gas content is strictly controlled ([H]≤2ppm, [O]≤20ppm) through LF refining and VD vacuum degassing. Electromagnetic stirring is required for the continuous casting blanks to reduce segregation and ensure compositional uniformity.

2. Hot Rolling and Piercing
After the blank is heated to 1200-1250°C, it is formed using a Mannesmann piercing mill. Key control points include:

- Piercing mandrel life management (replace every 50 pieces)

- Rolling speed ≤0.8m/s to avoid cracks on the inner and outer surfaces

- Final rolling temperature ≥850°C to prevent work hardening

3. Cold Working and Heat Treatment
For thin-walled tubes (wall thickness <20mm), cold drawing is commonly used, with deformation controlled at 30%-40%. Heat treatment must meet the following requirements:

- Normalizing temperature 900-950°C, holding time 1.5 min/mm

- Tempering temperature 720-750°C, holding time 2 min/mm

- Hardness controlled at 140-190 HBW

4. Non-destructive testing
100% eddy current testing (ET) and ultrasonic testing (UT), with a defect detection sensitivity of 1.6 mm flat-bottom holes. High-pressure boiler tubes also require a hydrostatic test. The test pressure calculation formula is:

P=2St/(D-0.8t), where S is the allowable stress, D is the outer diameter, and t is the wall thickness.

 

A335 P11 Seamless Pipe Manufacturing Process Standards

1. Smelting Process:

- Must use electric arc furnace + LF refining or converter + RH vacuum degassing process

- Hydrogen content control < 2ppm

2. Piercing Forming:

- Hot rolling temperature range 900-1200℃

- Final rolling temperature not lower than 870℃

- Cold drawn tubes require intermediate annealing (temperature 720-750℃)

3. Heat Treatment:

- Normalizing temperature 900-925℃ (austenitization)

- Tempering temperature not lower than 675℃ (holding time 2.5min/mm wall thickness)

4. Non-destructive Testing:

- 100% ultrasonic testing (compliant with ASTM E213 standard)

- Eddy current testing or magnetic flux leakage testing optional

- Hydrostatic test pressure = 2 times design pressure (held ≥ 10 seconds)

 

A335 P11 Alloy steel seamless pipe Dimensional Tolerance Requirements

Outer Diameter Tolerance:

- Hot-rolled tube: ±1.0% (DN≥114mm)

- Cold-drawn tube: ±0.5% (precision grade)

Wall thickness tolerance:

- +20%/-12.5% ​​(standard grade)

- ±10% (special orders)

Bending:

- ≤1.5mm/m (cold-drawn tube)

- ≤3mm/m (hot-rolled tube)

 

A335 P11 boiler tube Application Areas

A335 P11 alloy pipes are widely used in multiple fields due to their unique performance characteristics:

• Energy and Power Systems: Such as high-pressure steam pipelines in thermal power plants and main circuit cooling systems in nuclear power plants, their radiation resistance has been certified.
• Petrochemical Equipment: Such as hydrogenation reactor pipelines in refining plants and ultra-high-pressure steam pipelines in ethylene projects, effectively resisting the corrosion of corrosive media.
• High-End Manufacturing Fields: Such as high-temperature component substrates for aero-engines and core components of high-pressure hydraulic systems, meeting the requirements of lightweight design and high-pressure working environments.

 

A335 P11 Heat Exchanger Tube factory

 

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