What is ASTM A691 3CR Pipe?

ASTM A691 3CR is a high-temperature EFW pipe alloy with 3% chromium and 1% molybdenum. This A691 3CR pipe is less likely to rust than pipes with lower chrome grades. It can handle higher temperatures as it has a higher chromium content. In environments where standard 1CR or 2.25CR grades are not strong enough to resist scaling, 3CR is the preferred choice. The material handles environments where oxidation is a major concern.

Specification of ASTM A691 3CR Pipe

To ensure proper material selection for high-temperature elevated service, refer to the ASTM A691 3CR pipe specifications detailed below:

Standard ASTM A691 / ASME SA691
Types ERW / Welded Pipes
Pipes Size 1/2” NB to 36” NB
Thickness 3mm – 12 mm
End Plain End, Beveled End, Treaded

Chemical Composition of ASTM A691 Grade 3CR Pipe

The following table outlines the chemical composition requirements for ASTM A691 Grade 3CR chrome-molybdenum pipe:

Designation C Mn P S Si Cr Mo
ASTM A691 3Cr 0.15 0.3-0.6 0.035 0.035 0.5 2.75 - 3.25 0.9 - 1.1

Heat Treatment

ASTM A691 Grade 3CR requires specific heat treatment processes to achieve the necessary properties for high-temperature applications. These requirements are outlined below:

  • Normalising: 900-950°C (1650-1740°F)
  • Tempering: 675-760°C (1250-1400°F)
  • Post-Weld Heat Treatment: Required per ASME code

Applications of ASTM A691 3CR Chrome Moly Pipe

The ASTM A691 3CR chrome moly pipe serves high-temperature industrial applications where enhanced oxidation resistance is needed.

High Temperature Service

Steam lines and piping systems operating at elevated temperatures use A691 3CR pipes. The combination of creep strength and oxidation resistance works well in these conditions. The higher chromium content provides better scaling resistance than 2.25CR. This makes 3CR the right choice for more demanding temperature environments. Facilities use this grade when lower chrome alloys show excessive oxidation.