What Is A691 Pipe Material?
ASTM A691 longitudinal welded pipe is a chromium-molybdenum (Cr-Mo) alloy electric-fusion-welded (EFW) steel pipe for high-temperature, high-pressure pipeline systems. It is extensively used in the petroleum, chemical and power industries, offering high-temperature resistance, high-pressure endurance and corrosion resistance.
astm a691 chemical composition
| 1CR | 1-1/4CR | 2-1/4 CR | 5 CR | 9 CR | 91 | |
| C | 0.05-0.17 | 0.05-0.17 | 0.05-0.15 | 0.15 | 0.15 | 0.08-0.12 |
| Mn | 0.40-0.65 | 0.40-0.65 | 0.30-0.60 | 0.30-0.60 | 0.30-0.60 | 0.30-0.60 |
| P | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | 0.020 |
| S | 0.025 | 0.025 | 0.025 | 0.025 | 0.025 | 0.010 |
| Si | 0.15-0.40 | 0.50-0.80 | 0.50 | 0.50 | 1.00 | 0.20-0.50 |
| Cr | 0.80-1.15 | 1.00-1.50 | 2.00-2.50 | 4.00-6.00 | 8.00-10.00 | 8.00-9.50 |
| Mo | 0.45-0.60 | 0.45-0.65 | 0.90-1.10 | 0.45-0.65 | 0.90-1.10 | 0.85-1.05 |
| V | – | – | – | – | 0.04 | 0.18-0.25 |
ASTM A691 Equivalent
ASTM A691 V.S ASTM A671
| Comparison | ASTM A691 | ASTM A671 |
|---|---|---|
| Core purpose | Cr-Mo alloy EFW pipe for high-temperature, high-pressure service | Carbon/carbon-manganese EFW pipe for lower-temperature service |
| Material type | Cr-Mo alloy (e.g. 1.25Cr-0.5Mo) | Carbon steel / carbon-manganese steel |
| Typical service temperature | Up to about 650 C | Up to about 300 C |
| Strength class | Per A691 class system (e.g. CM-65, CM-70, CMSH-70) | Grade 60/65 class (415-485 MPa reference) |
| Key process | Mandatory normalizing (grain refinement) | Controlled rolling or normalizing (optional) |
| Inspection | High-temperature tensile test, hardness scan | Low-temperature impact test (-46 C) |
| Corrosion resistance | Oxidation/sulfidation resistance from Cr-Mo alloy | Relies on coatings or corrosion inhibitors |
Applications of A691 Steel Pipes
- Oil and Gas Industry: A691 steel pipes are widely used in oil and gas transmission pipelines, undertaking critical transportation tasks and ensuring the stability of energy supply.
- Chemical Industry: Due to its strong corrosion resistance, A691 steel pipes are widely used in chemical process pipelines to ensure the safe and stable operation of production facilities.
- Construction Engineering: In the construction industry, A691 steel pipes are used for structural support and other applications, providing reliable protection for construction projects due to their strength and stability.
- Machinery Manufacturing: As a material for mechanical parts, A691 steel pipes are used in the manufacture of various mechanical equipment, ensuring the normal operation and service life of the machinery.
A691 Alloy Steel Pipes factory
