ASTM A106 is the reference standard for seamless carbon steel pipe in high-temperature pressure service. Where ASTM A53 covers general-purpose piping up to 450°F, A106 is engineered specifically for the elevated temperatures found in refineries, petrochemical plants, and power generation — continuously rated to 1000°F (538°C). It is seamless only, no weld seam, and that is deliberate: at high temperature and pressure, the microstructural homogeneity of seamless pipe provides margins that welded pipe cannot reliably match.
ZC Steel Pipe manufactures ASTM A106 Grade B seamless pipe at our Hai'an City facility. We supply sizes from NPS ½ to NPS 24 with full MTRs, normalized heat treatment certification, and third-party inspection available. Our A106 Grade B material regularly goes into refineries and process plants across the Middle East and Africa.
CONTENTS
Standard Scope
Grade A, B & C — Mechanical Properties
Chemical Composition
Dimensions & Wall Thickness
High-Temperature Allowable Stress
Heat Treatment Requirements
ASTM A106 vs A53 vs A335 — When to Use Each
Sour Service Considerations
Applications
Frequently Asked Questions
1. Standard Scope
STANDARD DEFINITIONASTM A106 / A106M covers seamless carbon steel pipe for high-temperature service in nominal pipe sizes NPS ⅛ through NPS 48 (DN 6 through DN 1200). The ASME equivalent designation is SA-106, used when the pipe must comply with the ASME Boiler and Pressure Vessel Code.
The standard covers three grades — A, B, and C — differentiated by strength. Grade B is by far the most common commercial grade and accounts for the majority of A106 tonnage ordered globally. All three grades are seamless only: ASTM A106 has no provision for welded pipe. This distinguishes it clearly from ASTM A53, which covers ERW and furnace-welded pipe as well as seamless.
A106 pipe must be furnished in the hot-finished condition. When normalized heat treatment is required (mandatory for NPS 1½ and over in some applications), this must be specified at the time of order and will be reflected on the MTR.
2. Grade A, B & C — Mechanical Properties
| Property | Grade A | Grade B | Grade C |
| Tensile Strength (min) | 48,000 psi (330 MPa) | 60,000 psi (415 MPa) | 70,000 psi (485 MPa) |
| Yield Strength (min) | 30,000 psi (205 MPa) | 35,000 psi (240 MPa) | 40,000 psi (275 MPa) |
| Elongation in 2 in. (min) | 35% | 30% | 30% |
| Hardness (max) | Not specified | Not specified | Not specified |
| Hydrostatic Test | Required | Required | Required |
| Flattening Test | Required | Required | Required |
Engineering Insight — Why Grade B Dominates
Grade B strikes the right balance for most process piping applications — strong enough for typical operating pressures, ductile enough for field fabrication, and universally stocked. Grade C is used when design pressure is high and wall thickness must be minimized (e.g., in compact equipment nozzles). Grade A is rarely ordered for new process piping; its main advantage is ductility for tight-radius bends.
3. Chemical Composition
| Element | Grade A | Grade B | Grade C |
| Carbon (max) | 0.25% | 0.30% | 0.35% |
| Manganese | 0.27–0.93% | 0.29–1.06% | 0.29–1.06% |
| Phosphorus (max) | 0.035% | 0.035% | 0.035% |
| Sulfur (max) | 0.035% | 0.035% | 0.035% |
| Silicon (min) | 0.10% | 0.10% | 0.10% |
| Chromium (max) | 0.40% | 0.40% | 0.40% |
| Molybdenum (max) | 0.15% | 0.15% | 0.15% |
| Nickel (max) | 0.40% | 0.40% | 0.40% |
| Copper (max) | 0.40% | 0.40% | 0.40% |
| Vanadium (max) | 0.08% | 0.08% | 0.08% |
Field Note — Silicon Requirement
The mandatory 0.10% minimum silicon in A106 (vs. optional in A53 Type E) is not cosmetic. Silicon acts as a deoxidizer during steelmaking, improving microstructural cleanliness. In high-temperature service, a cleaner, fully killed steel resists graphitization (carbon migration to grain boundaries) — a failure mode that has caused catastrophic piping failures in refineries operating above 850°F over long periods.
4. Dimensions & Wall Thickness
ASTM A106 pipe dimensions conform to ASME B36.10M. Available in NPS ⅛ through NPS 48, with standard schedules from SCH 20 through SCH 160 and XXH. The most commonly ordered combination is NPS 1 through NPS 12 in SCH 40, SCH 80, and SCH 160 for process piping headers and branch connections.
| NPS (in) | OD (in) | SCH 40 WT (in) | SCH 80 WT (in) | SCH 160 WT (in) | XXH WT (in) |
| 1 | 1.315 | 0.133 | 0.179 | 0.250 | 0.358 |
| 1½ | 1.900 | 0.145 | 0.200 | 0.281 | 0.400 |
| 2 | 2.375 | 0.154 | 0.218 | 0.344 | 0.436 |
| 3 | 3.500 | 0.216 | 0.300 | 0.438 | 0.600 |
| 4 | 4.500 | 0.237 | 0.337 | 0.531 | 0.674 |
| 6 | 6.625 | 0.280 | 0.432 | 0.719 | 0.864 |
| 8 | 8.625 | 0.322 | 0.500 | 0.906 | 0.875 |
| 10 | 10.750 | 0.365 | 0.500 | 1.125 | 1.000 |
| 12 | 12.750 | 0.375 | 0.500 | 1.312 | 1.000 |
5. High-Temperature Allowable Stress
The primary reason engineers specify A106 Grade B over A53 Grade B is the elevated-temperature allowable stress rating. The ASME B31.3 allowable stress (S) for A106 Grade B at key temperatures:
| Temperature °F (°C) | Allowable Stress S (psi) | Notes |
| −20 to 100°F (−29 to 38°C) | 15,000 | Full ambient rating |
| 200°F (93°C) | 15,000 | No reduction yet |
| 400°F (204°C) | 14,400 | Slight reduction begins |
| 600°F (316°C) | 13,600 | Still substantial capacity |
| 800°F (427°C) | 11,800 | Approaching creep regime |
| 900°F (482°C) | 8,700 | Creep controls design |
| 1000°F (538°C) | 6,500 | Upper service limit for A106 |
Critical Engineering Point — Above 1000°F
Do not specify ASTM A106 for sustained service above 1000°F (538°C). Above this temperature, carbon steel undergoes accelerated creep and graphitization. The correct material step-up is ASTM A335 P11 (1¼Cr–½Mo) for 1000–1050°F, or P22 (2¼Cr–1Mo) for higher temperatures. This is a safety-critical decision — piping failures due to wrong material specification at high temperature are well-documented in the industry.
6. Heat Treatment Requirements
A106 pipe is furnished hot-finished. Normalization is not mandatory under the base standard, but it is commonly specified — particularly for larger diameters and heavier walls — to ensure uniform grain structure and to remove residual stresses from the hot-piercing process.
When to Specify Normalized
Sour service applications (NACE MR0175) — normalized condition ensures hardness compliance
Heavy wall pipe (wall thickness > 0.5 in / 12.7 mm) — more critical to control grain structure
Cryogenic service (when combined with impact testing per supplementary requirements)
Projects where the engineering specification explicitly requires normalized A106
Procurement Note — Specifying Heat Treatment
If you need normalized A106, state it explicitly in your purchase order: "ASTM A106 Grade B, Seamless, Normalized, per ASME SA-106." Pipe supplied without this note will typically be hot-finished only. The heat treatment certification must appear on the MTR — not just the chemical and mechanical test results.
7. ASTM A106 vs A53 vs A335 — When to Use Each
| Standard | Type | Max Temp | Key Grades | Best For |
| ASTM A53 Gr. B | Seamless + ERW | 450°F (232°C) | A, B | Water, gas, general industrial |
| ASTM A106 Gr. B | Seamless only | 1000°F (538°C) | A, B, C | Refineries, power plants, high-temp process |
| ASTM A335 P11 | Seamless only | 1100°F (593°C) | P1, P11, P22 | High-temp steam, boiler headers |
| ASTM A335 P22 | Seamless only | 1200°F (649°C) | P22, P91 | Very high-temp service, ultra-supercritical steam |
| API 5L Gr. B/X52 | Seamless + Welded | 300°F (149°C) | Gr.B, X42–X80 | Onshore/offshore pipelines, gas transmission |
8. Sour Service Considerations
ASTM A106 Grade B is routinely used in sour service (H₂S-containing environments) across refinery and upstream applications. The key compliance requirement is NACE MR0175 / ISO 15156-2, which sets maximum hardness limits to prevent sulfide stress cracking (SSC).
Maximum hardness: HRC 22 (237 HBW) per NACE MR0175
Heat treatment: Normalized condition strongly preferred; reduces hardness variation from the hot-piercing process
Testing: Request Brinell hardness testing (BHN) on the MTR; not required by default under A106 but is required for sour service
No grade restriction: All three grades (A, B, C) are permissible if hardness requirements are met
Critical Engineering Point — Hardness on MTR
ASTM A106 does not mandate hardness testing as standard. If your project specification requires NACE compliance, you must add a supplementary requirement to the purchase order requesting hardness testing (e.g., "S9 — Hardness Testing" or specific BHN per heat). Receiving A106 pipe without hardness certification for sour service is a procurement error that can shut down a project.
9. Applications
Refinery Process Piping
ASTM A106 Grade B is the workhorse material for carbon steel process piping in crude distillation units, hydrotreaters, and reformers where operating temperatures reach 600–900°F. It is specified under ASME B31.3 and commonly runs from pump nozzles through heat exchanger headers to fractionation columns.
Power Generation
Under ASME B31.1 (Power Piping), SA-106 Grade B covers steam lines, feedwater piping, and drain headers in conventional coal and gas power plants up to approximately 900°F. For ultra-supercritical plants above this temperature, P91 chrome-moly takes over.
Petrochemical & Gas Processing
LNG facilities, gas processing plants, and petrochemical complexes use A106 Grade B extensively in utility and process services. The seamless construction provides confidence in applications where external corrosion, vibration, and thermal cycling combine.
Boiler Connections & Pressure Vessels
SA-106 Grade B is listed in ASME Section II and Section VIII for pressure vessel nozzles, shell connections, and boiler tubes in low-to-moderate temperature service. Where higher temperature or cyclic service demands more, ASTM A335 alloy pipe takes over.
10. Frequently Asked Questions
What is ASTM A106 pipe used for?
ASTM A106 seamless carbon steel pipe is used for high-temperature and high-pressure service in refineries, petrochemical plants, and power generation. Rated to 1000°F (538°C), it is the standard specification for boiler steam lines, heat exchanger connections, and process headers under ASME B31.1 and B31.3.
What is the difference between ASTM A106 Grade A, Grade B, and Grade C?
Grade B is the most common: 60,000 psi tensile, 35,000 psi yield. Grade A is lower strength (48,000 psi tensile) but more ductile for forming. Grade C is highest strength (70,000 psi tensile, 40,000 psi yield) for maximum pressure capacity in compact designs. Grade B accounts for the vast majority of A106 orders.
Is ASTM A106 Grade B seamless only?
Yes. ASTM A106 covers seamless pipe exclusively — there is no welded option under this standard. This is a key difference from ASTM A53, which covers both seamless and ERW pipe. If your project requires welded pipe for high-temperature service, look to API 5L or ASTM A671/A672.
Can ASTM A106 Grade B be used for sour service?
Yes, provided it meets NACE MR0175/ISO 15156 requirements. Key controls are maximum hardness (HRC 22 / 237 HBW) and normalized heat treatment condition. Always request hardness testing as a supplementary requirement on your purchase order when specifying A106 for H₂S service.
What is the maximum temperature for ASTM A106 pipe?
ASTM A106 Grade B is rated for continuous service up to 1000°F (538°C) per ASME B31.1 and B31.3 allowable stress tables. Above this temperature, creep rate becomes excessive and chrome-moly alloy steels (ASTM A335 P11 or P22) should be specified instead.
Request ASTM A106 Grade B Seamless Pipe — ZC Steel Pipe
ZC Steel Pipe manufactures and exports ASTM A106 Grade B seamless carbon steel pipe from our mill in Hai'an City, China. Sizes NPS ½ to NPS 24. Full MTRs, normalized certification, hydrostatic testing, and third-party inspection available. Experienced in refinery and infrastructure projects across the Middle East and Africa.
Contact us: mandy.w@zcsteelpipe.com | WhatsApp: +86-139-1579-1813
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