difference between p11 and p22 material

P11 and P22 are both P-Numbers assigned to specific materials in the ASME Boiler and Pressure Vessel Code (BPVC) for welding purposes.

However, P11 and P22 refer to different materials with distinct characteristics. Here are the differences between P11 and P22 materials:

Chemical Composition

  • P11: P11 is a low alloy steel material that contains chromium and molybdenum as alloying elements. It typically has a composition of around 1% chromium and 0.5% molybdenum, along with other elements like carbon, manganese, and silicon.
  • P22: P22 is also a low alloy steel material, but it has a higher chromium content compared to P11. It typically contains around 2% chromium and 1% molybdenum, along with other elements such as carbon, manganese, and silicon.
Chemical PropertiesP11 MaterialP22 Material
Carbon (C)0.05-0.15%0.05-0.15%
Manganese (Mn)0.30-0.60%0.30-0.60%
Phosphorus (P)0.025% max0.025% max
Sulfur (S)0.025% max0.025% max
Silicon (Si)0.50-1.00%0.50-1.00%
Chromium (Cr)1.00-1.50%1.90-2.60%
Molybdenum (Mo)0.44-0.65%0.87-1.13%

Mechanical Properties

GradeTensile Strength (Mpa)Yield Strength (Mpa)Elongation (%)Hardness (HRB)

Material Specifications for p11 and p22 material

The grade P11 is designated as K11597 in the UNS system. The essential components of P11 pipes include carbon, manganese, phosphorus, sulfur, silicon, chromium, and molybdenum.

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The grade P22 is identified as K21590 in the UNS (Unified Numbering System) designation.

The material specifications for P11 and P22 are:

  1. ASTM A217
  2. ASTM A335
  3. ASTM A234
  4. ASTM A336
  5. ASTM A426

Temperature and Pressure Range

  • P11: P11 is suitable for moderate temperature and pressure applications. It is commonly used in power plants and refineries for components like headers, steam piping, and pressure vessels operating at temperatures up to around 600°C (1112°F).
  • P22: P22 is designed for higher temperature and pressure applications compared to P11. It is often used in power plants, petrochemical plants, and other high-temperature environments. P22 materials can withstand temperatures up to approximately 650°C (1202°F).

Weldability and Fabrication

  • P11: P11 materials have good weldability and can be easily fabricated using conventional welding techniques such as shielded metal arc welding (SMAW), gas tungsten arc welding (GTAW), and gas metal arc welding (GMAW).
  • P22: P22 materials also exhibit good weldability and can be welded using similar methods as P11. However, due to the higher chromium content, proper preheating and post-weld heat treatment may be required to prevent issues such as cracking and reduced corrosion resistance.
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P Number for P11 and P22 Material

P Number for P11 and P22 Material are:

  • P-11 Material P Number is 4.
  • P-22 Material P Number is 5A.

P11 and P22 Heat Treatment

Below are heat treatment requirements for P11 and P22 materials as per API 582.

Specific Applications

  • P11: P11 materials are commonly used in power plant piping systems, heat exchangers, and boilers, where moderate temperature and pressure conditions are encountered.
  • P22: P22 materials are often employed in high-temperature applications such as superheaters, reheaters, and steam piping systems in power plants and other industries.

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