What ASTM A106 Grade B Covers
ASTM A106 Grade B is the most widely specified grade of ASTM A106/A106M, the material specification for seamless carbon steel pipe intended for high-temperature service. The grade is defined by a minimum tensile strength of 415 MPa (60,000 psi) and a minimum yield strength of 240 MPa (35,000 psi), which makes it suitable for steam, condensate, process fluid and gas lines operating at elevated temperature and pressure. Pipe to this specification is produced by the seamless process only, from killed steel, and is supplied in nominal wall thickness with ends suitable for bending, flanging and similar forming operations.
Because its chemistry and strength level overlap with other general-purpose carbon steel pipes, A106 Grade B is frequently used as the default material for refinery, power plant and chemical processing piping, and it is cross-referenced in project specifications with ASTM A53 Grade B and API 5L Grade B.
Chemical Composition and Mechanical Properties
| Property | ASTM A106 Grade B |
|---|---|
| Carbon, max | 0.30% |
| Manganese | 0.29-1.06% |
| Phosphorus, max | 0.035% |
| Sulfur, max | 0.035% |
| Silicon, min | 0.10% |
| Tensile strength, min | 415 MPa (60,000 psi) |
| Yield strength, min | 240 MPa (35,000 psi) |
| Elongation, min | 30% in 50 mm |
The silicon minimum of 0.10% separates A106 Grade B from A53 Grade B and improves resistance to scaling at high temperature, while the low phosphorus and sulfur limits protect weldability and notch toughness.
Grade A, Grade B and Grade C Compared
| Grade | Carbon, max | Manganese | Tensile, min | Yield, min |
|---|---|---|---|---|
| A | 0.25% | 0.27-0.93% | 330 MPa (48,000 psi) | 205 MPa (30,000 psi) |
| B | 0.30% | 0.29-1.06% | 415 MPa (60,000 psi) | 240 MPa (35,000 psi) |
| C | 0.35% | 0.29-1.06% | 485 MPa (70,000 psi) | 275 MPa (40,000 psi) |
Grade B sits between the lower-strength Grade A and the higher-strength Grade C. Grade A is selected where forming is demanding and pressure is moderate, and Grade C where heavier wall and higher pressure duty justify the tighter carbon control.
Equivalent and Cross-Referenced Grades
ASTM A53 Grade B - comparable chemistry and strength, but A53 also permits welded pipe.
API 5L Grade B - similar mechanical properties for line pipe service.
EN 10216-2 P265GH - European seamless pressure pipe grade of comparable strength level.
DIN 17175 St35.8 - older German elevated-temperature grade still shown on legacy drawings.
JIS G3454 STPG 370 and BS 3601 360A - Japanese and British pressure service equivalents.
These grades are equivalent in strength class and chemistry family only, not identical. A substitution must be checked against dimensional tolerances, testing requirements and the applicable design code before it is accepted.
Heat Treatment, Testing and Inspection
A106 pipe is normally supplied as rolled. Where heat treatment is applied, the minimum temperature is 1200 degrees F (650 degrees C). Each length receives a hydrostatic test, or the purchaser may specify non-destructive electric examination by ultrasonic or eddy current methods instead of the hydrostatic test. Tensile, bend and flattening tests are performed on a lot basis and the results are reported on the mill test certificate.
Hardness is not a specified acceptance requirement of ASTM A106. Where a maximum hardness must be guaranteed, for example in wet sour service, it has to be stated in the purchase order and verified by test on the delivered pipe.
Frequently Asked Questions
Q: Is ASTM A106 Grade B the same as ASME SA-106 Grade B?
Yes. ASME Boiler and Pressure Vessel Code Section II adopts the ASTM specification with essentially identical technical requirements, and the SA prefix indicates acceptance for boiler and pressure vessel construction.
Q: Can A106 Grade B pipe be welded?
Yes. The controlled carbon and manganese levels give good weldability, and the pipe is routinely joined by GTAW, SMAW and GMAW processes under qualified procedures with suitable preheat and interpass control.
Q: What is the maximum service temperature of A106 Grade B?
Allowable stress values for the grade are tabulated up to 425 degrees C (800 degrees F) in the ASME piping codes. Long-term scaling resistance depends on silicon content, atmosphere and stress level.
Q: What is the difference between A106 Grade A and Grade B?
Grade B allows higher carbon and manganese, which raises minimum tensile strength from 330 MPa to 415 MPa and minimum yield strength from 205 MPa to 240 MPa, so it is selected for higher pressure duty.
Q: Is A106 Grade B killed steel?
Yes. A106 pipe is made from killed steel, giving a fully deoxidised and homogeneous structure with consistent properties for high-temperature service.
Q: Is welded pipe available to ASTM A106 Grade B?
No. ASTM A106 covers seamless pipe only. Welded carbon steel pipe for high-temperature duty is normally ordered to other specifications covering welded construction.