What is ASTM A691 2.25CR Pipe?

ASTM A691 2.25CR is a chromium-molybdenum alloy with 2.25% Cr and 1% Mo. This specification covers electric fusion-welded pipe for high-temperature service. The A691 2.25CR pipe is equivalent to P22 or Grade 22 material. This is the most widely used Cr-Mo grade for power plant piping. The elevated chromium content provides oxidation resistance at elevated temperatures. Molybdenum improves creep strength so the material can handle long-term service under stress. Power plants choose this grade when both temperature and reliability matter.

Specification of ASTM A691 2.25CR Pipe

Technical specifications for ASTM A691 Grade 2.25CR alloy steel pipes are as follows:

Standard ASTM A691 / ASME SA691
Types ERW / Welded Pipes
Pipes Size 1/8"NB TO 30"NB IN
Thickness 0.3mm – 50 mm
End Plain End, Beveled End, Treaded

Chemical Composition of ASTM A691 2.25CR Pipe

Chemical composition limits as per the ASTM A691 standard for Grade 2.25CR chrome-moly pipe are presented below:

Specification C % Mn % P % Max S % Max Si % Cr % Mo %
ASTM ASTM A691 2.25CR 0.05–0.15% 0.30–0.60% 0.025% 0.025% 0.15–0.50% 2.00–2.50% 0.90–1.10%

Mechanical Properties of ASTM A691 2.25CR Pipe

ASTM A691 Grade 2.25CR must meet specific mechanical performance criteria for high-temperature service. The minimum requirements are outlined in the table below:

Grade Yield Strength (Min) Tensile Strength (Min) Elongation (%)
GR 2.25 CR 310 MPa 485–690 MPa 18%

Heat Treatment

To ensure optimal microstructure and mechanical properties for elevated temperature service, the following heat treatment parameters are needed for ASTM A691 2.25CR:

  • Normalising: 900-940°C (1650-1725°F)
  • Tempering: 675-745°C (1250-1375°F)
  • Post-Weld Heat Treatment: Required per ASME code

Applications of ASTM A691 2.25CR P22 pipe

The ASTM A691 2.25CR P22 pipe serves high-temperature power generation and petrochemical applications where reliability is critical.

Main Steam Lines

High-temperature main steam and reheat piping in power plants use 2.25CR pipes due to their excellent creep strength. Oxidation resistance remains effective even at elevated temperatures. These pipes are the industry standard for critical steam transport systems.

Petrochemical Heaters

Process heater piping and high-temperature refinery service rely on 2.25Cr-1Mo alloy. The combination of strength and corrosion resistance makes this grade suitable for harsh petrochemical environments.

Boiler Components

Headers and connecting piping in utility boilers use ASTM A691 2.25CR for reliable long-term service. These components operate under high temperature and pressure continuously. The material properties ensure consistent performance throughout the boiler's service life.