ASTM A106 Grade B
UNS K03006
Seamless carbon steel pressure pipe for high-temperature service · ASTM A106/A106M-26 · ASTM A530/A530M-18 · ASME B36.10-2022 · ASME BPVC Section II, Part A, SA-106/SA-106M where ASME Code material is required
ASTM A106 Grade B is the principal seamless carbon steel pipe grade used in elevated-temperature power and process piping. It combines 240 MPa minimum yield strength with controlled carbon-manganese chemistry, but the designation alone does not establish pipe schedule, design allowable stress, impact toughness, corrosion suitability or maximum service temperature. Procurement must identify the standard edition, dimensions, manufacturing condition, pressure-integrity test route and any service-specific supplementary requirements.
- ASTM A106/A106M-26Current ASTM edition · Active edition published in 2026; contracts and legacy projects may invoke an earlier year-date.
- Seamless pipe onlyProduct route · A welded pipe cannot be certified solely as ASTM A106.
- 415 MPa [60 ksi]Minimum tensile strength · Room-temperature product requirement for Grade B.
- 240 MPa [35 ksi]Minimum yield strength · Not the allowable stress for pressure design.
- NPS 1/8–48 [DN 6–1200]Size scope · Nominal outside diameters and schedule wall thicknesses are normally selected from ASME B36.10.
- Hydrostatic test or permitted full-body electric NDEIntegrity test · Untested pipe marked “NH” is possible only when explicitly specified by the purchaser.
Overview
- Designation system
- ASTM product specification; adopted in the ASME BPVC as SA-106
- Product forms
- Seamless carbon steel pipe, NPS 1/8 to NPS 48 [DN 6 to DN 1200], Nipples cut from pipe conforming to the specification
- Condition
- Hot-finished, normally without mandatory heat treatment, Cold-drawn and heat treated after the final draw at 1200 °F [650 °C] or higher, Hot-finished and optionally heat treated at 1200 °F [650 °C] or higher
- Density
- 7.85 g/cm³ (Representative density for carbon steel; not a specified ASTM A106 acceptance requirement.)
What the designation defines
ASTM A106/A106M is a product specification for seamless carbon steel pipe intended for high-temperature service. Grade B identifies the applicable chemistry and room-temperature tensile requirements. It does not define a unique wall thickness, pressure rating or heat-treatment condition. Those characteristics depend on the ordered NPS or diameter, schedule or nominal wall, manufacturing route, options and governing construction code.
ASTM A530/A530M supplies general requirements such as test practices, permissible repairs and certification provisions unless A106/A106M states otherwise. ASME B36.10 supplies the standardized pipe dimensions. For ASME Boiler and Pressure Vessel Code construction, the applicable material specification is SA-106/SA-106M in Section II, Part A; the adopted ASME edition and the ASTM edition should not be assumed to be interchangeable without checking the governing Code edition.
Grade B chemical composition
| Element | Requirement | Technical significance |
|---|---|---|
| Carbon | 0.30 max | Principal strength and weldability control. |
| Manganese | 0.29–1.06 | The carbon-reduction rule can permit a higher manganese maximum. |
| Phosphorus | 0.035 max | Restricted for ductility, toughness and weld quality. |
| Sulfur | 0.035 max | Restricted for hot workability and integrity. |
| Silicon | 0.10 min | Consistent with killed-steel manufacture and deoxidation. |
| Chromium | 0.40 max | Residual-element limit. |
| Copper | 0.40 max | Residual-element limit. |
| Molybdenum | 0.15 max | Residual-element limit. |
| Nickel | 0.40 max | Residual-element limit. |
| Vanadium | 0.08 max | Residual-element limit. |
Chromium, copper, molybdenum, nickel and vanadium combined are limited to 1.00% maximum.
Unless the purchaser specifies otherwise, each 0.01 percentage-point reduction below the 0.30% carbon maximum permits manganese to exceed 1.06% by 0.06 percentage point, up to 1.65% maximum. Consequently, “A106 Grade B” does not guarantee low carbon equivalent or uniform weldability across all heats.
Room-temperature mechanical requirements
| Property or specimen condition | Longitudinal | Transverse | Applicability |
|---|---|---|---|
| Tensile strength, minimum | 415 MPa [60 ksi] | 415 MPa [60 ksi] | Specified room-temperature minimum. |
| Yield strength, minimum | 240 MPa [35 ksi] | 240 MPa [35 ksi] | Specified room-temperature minimum. |
| Basic elongation in 50 mm [2 in.] | 30% | 16.5% | Applies to transverse strip tests and small sizes tested in full section, subject to the specification's detailed provisions. |
| Standard round specimen elongation in 50 mm [2 in.] | 22% | 12% | Applies when a standard round tensile specimen is used. |
| Longitudinal strip specimen | Calculated | — | Minimum elongation is calculated from specimen area and specified tensile strength rather than represented by one universal percentage. |
Orientation, specimen geometry and wall thickness affect the applicable elongation requirement.
These are material acceptance properties, not piping-design stresses. Allowable stress, pressure-temperature capability, weld-joint factors, corrosion allowance and component thickness must be established under the governing construction code and design conditions.
Manufacture and delivery condition
| Product range or route | Requirement |
|---|---|
| NPS 1½ [DN 40] and smaller | May be supplied hot-finished or cold-drawn. |
| NPS 2 [DN 50] and larger | Normally supplied hot-finished; cold-drawn pipe requires agreement between manufacturer and purchaser. |
| Hot-finished pipe | No heat treatment is mandatory. If heat treated, the temperature must be at least 1200 °F [650 °C]. |
| Cold-drawn pipe | Must be heat treated after the final cold-drawing pass at 1200 °F [650 °C] or higher. |
| Steelmaking | Killed steel produced by an accepted primary melting process; ingot or strand casting is permitted. |
The usual microstructure is ferrite and pearlite, but ASTM A106 does not specify a metallographic phase balance or grain size for the base grade. Hot-finished and cold-drawn products can differ in dimensional finish, surface condition and residual stress even though both satisfy the same Grade B tensile minima. The manufacturing condition should therefore be retained on purchase documents and material certificates where it matters to fabrication or inspection.
Testing, integrity and workmanship
| Control | Base requirement or practical meaning |
|---|---|
| Heat analysis | An analysis of each heat is required and reported when certification is required. |
| Product analysis | Available at purchaser request; the base provision uses samples from finished-pipe lots. Supplementary Requirement S1 requires analysis of each length when ordered. |
| Tensile test | Normally one pipe from each defined lot. |
| Small-diameter bend test | For NPS 2 [DN 50] and smaller, one pipe from each lot is subjected to the specified cold-bend test. |
| Large, heavy-wall bend test | Required where outside diameter exceeds 25 in. [635 mm] and the specified diameter-to-wall ratio is 7.0 or less. |
| Flattening capability | The base pipe must be capable of meeting the stated criteria, but routine flattening testing is not mandatory unless a supplementary requirement is ordered. |
| Pressure-integrity examination | Each length is normally hydrostatically tested or receives a permitted full-body electric examination. |
| Omission of both integrity tests | Permitted only when specified by the purchaser; the pipe and certification are marked “NH.” |
Permitted electric examination methods include ultrasonic, eddy-current and flux-leakage techniques. Their calibration discontinuities establish rejection sensitivity; they do not represent a guaranteed minimum detectable flaw size in every orientation. Pipe-end regions can also be affected by the examination method's end effect. If critical defect orientations or complete end coverage matter, the purchase specification should define the required method, coverage and acceptance criteria.
A surface imperfection penetrating more than 12.5% of nominal wall thickness, or encroaching on minimum permissible wall, is treated as a defect. Disposition can include grinding, removal of the affected section, rejection or approved weld repair. Although the pipe is manufactured seamlessly, local repair welding is permitted only with purchaser approval and under the applicable A530/A530M provisions; “seamless” must not be interpreted as an absolute prohibition on all repair weld metal.
Dimensions and dimensional tolerances
| Characteristic | Requirement or consequence |
|---|---|
| Standard dimensions | Normally selected by NPS/DN and schedule or nominal wall from ASME B36.10. |
| Nonstandard dimensions | Permitted if all other specification requirements are satisfied and dimensions are clearly ordered. |
| Minimum wall thickness | At any point, not more than 12.5% below the specified nominal wall thickness. |
| Mass per unit length | Not more than 10% over or 3.5% under the specified mass. |
| Special OD tolerance | For pipe over 10 in. [250 mm] OD, ±1% may be ordered under the special outside-diameter provision. |
| Special ID tolerance | For pipe over 10 in. [250 mm] ID, ±1% may be ordered under the special inside-diameter provision. |
| Lengths | Specific, single-random or double-random lengths must be identified; jointed lengths are not permitted unless specified. |
General and size-dependent diameter tolerances must be checked in A106/A106M and A530/A530M for the exact ordered dimensions.
A schedule number is a dimensional series, not a material grade or pressure rating. The same A106 Grade B designation can be supplied in many schedules, and pressure capability changes with actual wall, diameter, design temperature, corrosion allowance and governing code rules.
Fabrication and service considerations
A106 pipe is intended to be suitable for welding, bending, flanging and similar forming operations, provided procedures are appropriate to the chemistry, dimensions and service. Grade B's carbon maximum and permitted manganese increase mean that welding procedure qualification, preheat and postweld heat treatment cannot be selected from the grade name alone. Actual heat chemistry, carbon equivalent, wall thickness, restraint, hydrogen control and the applicable construction code must be considered.
The specification is aimed at high-temperature service but does not assign a universal maximum operating temperature. At elevated temperature, allowable stress reduction, oxidation, corrosion, creep behavior and possible graphitization must be assessed under the applicable design and in-service inspection rules. ASTM specifically calls attention to possible graphitization. Process environment can control suitability more strongly than nominal metal temperature alone.
Impact testing is not a base A106 Grade B requirement. The grade should not be assumed suitable for low-temperature or brittle-fracture-sensitive service merely because its room-temperature tensile results comply. Minimum design metal temperature, thickness, heat treatment, fabrication and any applicable Code impact-test exemption must be evaluated separately.
A106 Grade B does not inherently establish sour-service compliance, resistance to hydrogen damage, HF-service suitability, corrosion allowance or internal cleanliness. These require service-specific material and inspection requirements.
Optional requirements for demanding service
| Supplement | Purpose | Key point |
|---|---|---|
| S1 | Enhanced chemistry verification | Product analysis on every pipe length. |
| S2 | Transverse tensile testing | Specified transverse tests on NPS 8 [DN 200] and larger. |
| S3 or S4 | Flattening tests | Standard or enhanced flattening-test regimes. |
| S5 | Macrostructure control | Etching examination for homogeneity and objectionable internal defects. |
| S6 | Carbon-equivalent control | CE limited to 0.50 maximum, or to a lower agreed value. |
| S7 | Heat-treated test specimens | Tensile testing after purchaser-specified stress relief or normalization. |
| S9 | Hydrofluoric-acid alkylation service | Adds tighter CE and residual-element controls, minimum carbon, repair-welding restrictions and “HF” marking. |
Supplementary requirements apply only when explicitly stated in the purchase order.
| Control | Requirement |
|---|---|
| Carbon equivalent | 0.43 max for specified wall ≤1 in. [25.4 mm]; 0.45 max for wall >1 in. [25.4 mm]. |
| Vanadium | 0.02% max. |
| Niobium | 0.02% max. |
| Vanadium plus niobium | 0.03% max. |
| Nickel plus copper | 0.15% max. |
| Carbon | 0.18% minimum. |
| Repair weld consumables | Low-hydrogen type; E60XX electrodes prohibited; resulting weld chemistry must meet the pipe chemistry requirements. |
| Identification | Pipe marked “HF.” |
S9 is an optional material control and does not replace the complete design, fabrication, operation and inspection requirements for HF alkylation units.
Specifying and purchasing the pipe
| Purchase-order item | Why it matters |
|---|---|
| Specification and year-date | State ASTM A106/A106M-26, or the project-required edition. Use SA-106/SA-106M where the governing ASME Code requires it. |
| Grade | State Grade B explicitly. |
| Quantity and length basis | Identify number of lengths or total length and specific, single-random or double-random length. |
| Dimensions | State NPS/DN and schedule, or OD/ID and nominal wall as applicable. |
| Manufacturing condition | State hot-finished or cold-drawn if the distinction is required. |
| End finish | State plain square, beveled, threaded or other project requirement. |
| Integrity-test route | Specify hydrostatic test, electric NDE, both, or—only if genuinely intended—neither with NH marking. |
| Certification | Require a material test report and any project-specific certificate format or traceability. |
| Supplementary requirements | List S1–S9 options individually; they do not apply automatically. |
| Design and service conditions | Provide end use and any low-temperature, sour, hydrogen, HF, cleanliness, corrosion or special examination requirements. |
| Special tolerances | Identify special OD or ID tolerances where fit-up, machining or component manufacture requires them. |
| Repair restrictions | If repair welding is prohibited or specially controlled, state this explicitly rather than relying on the word “seamless.” |
Receiving inspection should reconcile the purchase order, pipe marking and material test report for specification edition, grade, heat number, size, schedule or wall, manufacturing condition, heat analysis, mechanical results, integrity-test marking and all ordered supplementary requirements.
Sources
- ASTM A106/A106M-26 — Standard Specification for Seamless Carbon Steel Pipe for High-Temperature ServiceASTM International
- ASTM A106/A106M-19a — Standard Specification for Seamless Carbon Steel Pipe for High-Temperature ServiceASTM International
- ASTM A530/A530M-18 — General Requirements for Specialized Carbon and Alloy Steel PipeASTM International
- ASME B36.10-2022 — Welded and Seamless Wrought Steel PipeASME
- ASME BPVC Resources — Section II materials and stress-table resourcesASME
- API Recommended Practice 751 — Safe Operation of Hydrofluoric Acid Alkylation UnitsAmerican Petroleum Institute
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