ASTM A106 Grade B Pipe Specifications
ASTM A106 Grade B is the most widely specified seamless carbon steel pipe material in refinery, petrochemical, and power generation piping. It is a seamless-only specification designed for high-temperature service up to approximately 427 degC (800 degF). Grade B occupies the middle ground of the A106 specification, offering higher strength than Grade A with better weldability than Grade C, making it the default choice for process piping in ASME B31.3 and ASME B31.1 systems.
When ASTM A106 Grade B Is Specified
A106 Gr.B is the standard pipe material for high-temperature process piping, boiler feed lines, steam service (up to 427 degC), heat exchanger connections, and any application requiring seamless carbon steel pipe with good elevated-temperature properties. It is the default “line pipe” in most refinery piping classes.
ASTM A106 Grade B Specifications Table
| Property | ASTM A106 Grade B |
|---|---|
| Specification | ASTM A106 / ASME SA-106 |
| Grade | B |
| Manufacturing | Seamless (hot-finished or cold-drawn) |
| Carbon (max) | 0.30% |
| Manganese | 0.29-1.06% |
| Phosphorus (max) | 0.035% |
| Sulfur (max) | 0.035% |
| Silicon (min) | 0.10% |
| Chromium (max) | 0.40% |
| Molybdenum (max) | 0.15% |
| Nickel (max) | 0.40% |
| Copper (max) | 0.40% |
| Min. tensile strength | 415 MPa (60 ksi) |
| Min. yield strength | 240 MPa (35 ksi) |
| Min. elongation | 30% (in 2 inches) |
| Max. service temperature | ~427 degC (800 degF) |
| Size range | NPS 1/4 to NPS 26 |
| Heat treatment | Hot-finished; or cold-drawn and normalized/stress-relieved |
Comparison: ASTM A106 Grade A vs B vs C
| Property | Grade A | Grade B | Grade C |
|---|---|---|---|
| Min. yield strength | 205 MPa (30 ksi) | 240 MPa (35 ksi) | 275 MPa (40 ksi) |
| Min. tensile strength | 330 MPa (48 ksi) | 415 MPa (60 ksi) | 485 MPa (70 ksi) |
| Carbon (max) | 0.25% | 0.30% | 0.35% |
| Weldability | Excellent | Very good | Good (preheat may be required) |
| Common use | Low-stress service | Standard process piping | High-pressure, thick-wall |
Testing Requirements
ASTM A106 requires the following tests on each lot:
- Tensile test: One test per heat or per lot
- Flattening test: For pipe NPS 2 and under (one per lot)
- Bend test: Alternative to flattening test
- Hydrostatic test: Mandatory unless waived by purchaser (test pressure per ASTM A106 Table 4)
Supplementary requirements that can be added to the purchase order include product analysis (S1), transverse tension test (S2), flattening test (S3), metallographic examination (S4), Charpy impact test (S5), and grain size requirements (S6).
Dual Certification with API 5L
Many pipe mills dual-certify A106 Grade B seamless pipe to both ASTM A106 and API 5L Grade B (PSL1, seamless). The chemistry and mechanical properties overlap, and dual certification provides procurement flexibility; the same pipe can be used for both process piping and pipeline applications.
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