Overview
ASTM A106 is the premier material specification for seamless carbon steel nominal wall pipe intended for high-temperature and high-pressure service. It is the primary workhorse material across petroleum refineries, petrochemical plants, power generation plants, and industrial steam systems. Engineered for continuous operation under severe elevated thermal and pressure conditions, its dimensional geometry is governed by **ASME B36.10M**, covering nominal pipe sizes from **NPS 1/8 (DN 6)** through **NPS 48 (DN 1200)**. The standard specifies three strength grades—**Grade A, Grade B, and Grade C**. Grade B serves as the global industry standard (accounting for over 90% of process piping installations) due to its optimal balance of mechanical tensile strength and field weldability. Crucially, ASTM A106 mandates deoxidized **killed steel** (minimum Silicon content of Si ≥ 0.10%) and 100% seamless hot-finished or cold-drawn manufacturing to eliminate longitudinal weld seam defects and ensure long-term microstructural stability.
Scope & Applicability
Applies To Industries
Covers — seamless carbon steel pipe for elevated temperature service:
- Sizes from NPS 1/8 (DN 6) to NPS 48 (DN 1200).
- Grades A, B, and C (Grade B is overwhelmingly the global industry standard).
- Hot-finished or cold-drawn seamless manufacturing.
- Suitable for bending, flanging (vanstoning), field welding, and thermal forming operations.
Does NOT cover (exclusions) — the following are governed elsewhere:
- Welded Carbon Steel Pipe: Electric Resistance Welded (ERW) or Furnaced Welded pipe → ASTM A53 or API 5L.
- Low-Temperature Cryogenic Service: Sub-zero impact-tested pipe for temperatures below -20°F (-29°C) → ASTM A333 Grade 6.
- High-Temperature Alloy Piping (Above 800°F / 427°C): Chrome-Moly alloy pipe to prevent graphitization → ASTM A333 or ASTM A335 (P11, P22, P91).
- Dimensional Sizing (OD and Schedule Wall Thickness): Geometry governed by ASME B36.10M.
Key Requirements
ASTM A106 establishes key material, chemical, and testing baseline requirements:
- 100% Seamless Construction: Must be manufactured by a seamless process (hot-finished or cold-drawn). Weld repairs of the pipe body are strictly prohibited.
- Killed Steel Requirement: Steel must be deoxidized ("killed steel") with a minimum Silicon content of 0.10% to produce a stable, deoxidized grain structure for elevated temperatures.
- Chemical Limits (Grade B Baseline):
- Carbon (C) max 0.30%, Manganese (Mn) 0.29–1.06%, Phosphorus (P) max 0.035%, Sulfur (S) max 0.035%, Silicon (Si) min 0.10%.
- Limits combined trace elements (Cr, Cu, Ni, Mo, V) to max 1.00%.
- Mechanical Tensile Requirements:
- Grade A: Tensile Strength min 48 ksi (330 MPa), Yield Strength min 30 ksi (205 MPa).
- Grade B: Tensile Strength min 60 ksi (415 MPa), Yield Strength min 35 ksi (240 MPa).
- Grade C: Tensile Strength min 70 ksi (485 MPa), Yield Strength min 40 ksi (275 MPa).
- Mandatory Quality Integrity Testing: Every pipe length must undergo Hydrostatic Testing or Non-Destructive Electric Testing (Eddy Current or Ultrasonic Inspection).
Technical Details
ASTM A106 is the primary material standard for seamless carbon steel pressure piping used in high-temperature industrial environments.
1. ASTM A106 Chemical Composition Limits Table
| Element (%) | Grade A | Grade B (Industry Workhorse) | Grade C |
|---|---|---|---|
| Carbon (C), max | 0.25% | 0.30% | 0.35% |
| Manganese (Mn) | 0.27 – 0.93% | 0.29 – 1.06% | 0.29 – 1.06% |
| Phosphorus (P), max | 0.035% | 0.035% | 0.035% |
| Sulfur (S), max | 0.035% | 0.035% | 0.035% |
| Silicon (Si), min | 0.10% | 0.10% | 0.10% |
| Chromium (Cr), max | 0.40% | 0.40% | 0.40% |
| Copper (Cu), max | 0.40% | 0.40% | 0.40% |
| Nickel (Ni), max | 0.40% | 0.40% | 0.40% |
| Molybdenum (Mo), max | 0.15% | 0.15% | 0.15% |
2. Mechanical Tensile & Yield Strength Comparison Table
| Grade Designation | Tensile Strength, min (ksi / MPa) | Yield Strength, min (ksi / MPa) | Primary Application / Weldability |
|---|---|---|---|
| Grade A | 48 ksi / 330 MPa | 30 ksi / 205 MPa | High ductility; ideal for severe cold bending and coiling |
| Grade B | 60 ksi / 415 MPa | 35 ksi / 240 MPa | Universal industry standard; balanced strength and excellent weldability |
| Grade C | 70 ksi / 485 MPa | 40 ksi / 275 MPa | High strength for high pressure; requires preheat for welding |
3. Comparison Matrix: ASTM A106 vs ASTM A53 vs API 5L
| Feature / Standard | ASTM A106 Grade B | ASTM A53 Grade B | API 5L Grade B (PSL1/PSL2) |
|---|---|---|---|
| Seam Construction | 100% Seamless only | Seamless (Type S) or Welded (Type E/F) | Seamless or Welded (ERW/SAW) |
| High Temp Focus | Yes (Killed steel, Si ≥ 0.10%) | No (General utility/low pressure) | Pipeline transmission |
| Silicon Content | Mandatory min 0.10% | Not specified for Type E/F | Controlled per PSL rating |
| Hydrotest / NDE | Mandatory 100% | Mandatory 100% | Mandatory 100% |
Engineering Notes
Crucial engineering guidance and common design/procurement pitfalls for ASTM A106 pipe:
1. The 800°F (427°C) Graphitization Risk Barrier
Although ASTM A106 is rated for "high-temperature service", prolonged operation above 800°F (427°C) causes the iron carbide (cementite) phase in carbon steel to decompose into graphite nodules (graphitization).
[!WARNING] Graphitization leads to catastrophic brittle rupture of the pipe wall without warning! For operating temperatures exceeding 800°F (427°C), ASME B31.3 and ASME B31.1 require switching from carbon steel to Chromium-Molybdenum alloy steel pipe such as ASTM A335 Grade P11, P22, or P91.
2. Sub-Zero Low-Temperature Brittle Fracture (< -20°F / -29°C)
ASTM A106 does NOT require impact testing. Carbon steel undergoes a dramatic ductile-to-brittle transition at low temperatures.
- Design Rule: Do NOT use A106 pipe for operating or upset temperatures below -20°F (-29°C). For sub-zero cryogenic or low-temperature services (e.g. LPG, ethylene, cold climates), specify ASTM A333 Grade 6 (which requires Charpy V-notch impact testing at -50°F / -45°C).
3. Dual / Triple Stamped Pipe Pitfall (A106-B / A53-B / API 5L-B)
Pipe manufacturers frequently mark pipe with multiple material specifications (e.g., "ASTM A106-B / ASTM A53-B / API 5L-B").
- Engineering Audit: Dual-stamped pipe is acceptable for A106 service ONLY if the Mill Test Report (MTR) explicitly certifies that the pipe is Seamless (Type S) and contains a minimum Silicon content of 0.10%. Electric Resistance Welded (ERW) A53 pipe can NEVER be used for A106 high-temperature service.
4. Hydrostatic Testing vs NDE Substitution
ASTM A106 permits pipe manufacturers to substitute non-destructive electric testing (Ultrasonic or Eddy Current) in place of hydrostatic pressure testing.
- Quality Control Rule: If full hydrostatic pressure testing is required by project specifications or boiler codes (ASME Section I), the purchase order MUST explicitly state: "Hydrostatic testing per ASTM A106 Section 15 is required."
5. Welding Preheat Requirements for Grade C
While Grade B is easily welded with standard E7018 electrodes without preheat (above 50°F / 10°C), Grade C contains up to 0.35% Carbon.
- Welding Caution: Grade C has a higher Carbon Equivalent ($CE$), increasing the risk of hydrogen-assisted cold cracking in the Heat-Affected Zone (HAZ). Preheat to 200°F–300°F (93°C–149°C) is mandatory for Grade C wall thicknesses over 0.5 inches.
Source, Edition & Status
- Publisher
- ASTM
- Industries
- Refinery, Petrochemical, Power Plant, General Industry, Pipeline
- Last Reviewed
- 2026-07-01
- Last Updated
- 2026-07-01
- Verified By
- Engineering content reviewer
- Content Status
- reviewed