1. Standard Overview
ASTM A106/A106M is the standard specification for seamless carbon steel pipe designed for high-temperature and moderate-pressure service. It covers three core grades: Grade A, Grade B and Grade C, classified by different carbon content and mechanical strength. The pipes are hot-finished or cold-drawn seamless hollow products, widely used for transporting steam, water, oil and gas in power plants, refineries and general industrial piping systems.
2. Full Size & Dimensional Specifications
2.1 Outer Diameter Range
Nominal pipe sizes (NPS) from 1/8” up to NPS 48; corresponding outer diameters range from 10.3 mm to 1219 mm.
2.2 Wall Thickness
Available in standard wall (STD), extra strong (XS), double extra strong (XXS), and custom minimum/nominal wall thickness as per customer requirements. Wall thickness tolerance: +15% / -12.5% of specified nominal wall.
2.3 Length Options
- Random mill lengths: 4–7 meters for hot-finished pipes; 2–6 meters for cold-drawn pipes
- Fixed cut lengths, double random lengths, or custom U-cut lengths upon request
2.4 Dimensional Tolerance
- Outside diameter: ±0.75% for hot-finished pipes; tighter ±0.5% tolerance for cold-drawn versions
- Straightness, ovality and end squareness are strictly controlled for welding and assembly.
2.5 Pipe End Treatments
Standard plain cut ends; optional bevelled ends for welding, plastic capped ends for export anti-dust protection.
3. Chemical Composition Parameters (Max Content, %)
| Element | Grade A | Grade B | Grade C |
|---|
| Carbon | 0.25 | 0.30 | 0.35 |
| Manganese | 0.27–0.93 | 0.29–1.06 | 0.29–1.06 |
| Phosphorus | 0.035 | 0.035 | 0.035 |
| Sulfur | 0.035 | 0.035 | 0.035 |
Silicon content ranges 0.10–0.40% for all grades to improve oxidation resistance at elevated temperatures.
4. Mechanical Property Technical Index (Room Temperature)
| Mechanical Index | Grade A | Grade B | Grade C |
|---|
| Minimum Tensile Strength | 330 MPa (48 ksi) | 415 MPa (60 ksi) | 485 MPa (70 ksi) |
| Minimum Yield Strength | 205 MPa (30 ksi) | 240 MPa (35 ksi) | 275 MPa (40 ksi) |
| Minimum Elongation (50mm gauge) | ≥35% | ≥30% | ≥30% |
| Max Brinell Hardness | 121 HB | 137 HB | 156 HB |
- Grade B is the most widely used due to balanced strength and ductility.
- Higher carbon Grade C provides greater tensile strength for heavier pressure loads.
5. Core Performance Characteristics
- High-temperature resistance
Stable mechanical performance under continuous service temperature up to 425°C, suitable for steam boiler piping and high-temperature fluid transmission. - Excellent formability
Good ductility supports bending, flaring, expanding, cold forming and hot rolling without cracking during fabrication. - Reliable weldability
Low controlled carbon content enables easy welding with standard carbon steel welding consumables, no strict preheating required for thin-wall pipes. - Uniform seamless structure
No longitudinal weld seam eliminates leakage risks under cyclic pressure, superior to welded steel pipe for critical pressure circuits. - Cost-effective general corrosion resistance
Satisfactory anti-rust performance for clean steam, water, oil and natural gas; suitable for non-strong acid/alkali medium delivery.
6. Mandatory Factory Test Standards
Every batch of ASTM A106 pipes must pass the following inspections in compliance with the standard:
- Tensile test & hardness test to verify mechanical indicators
- Flattening test to check ductility and internal defects
- Hydrostatic test: full-length water pressure test without leakage; alternative eddy current non-destructive testing is acceptable
- Visual and dimensional inspection for surface scratches, dimensional deviation
- Heat chemical analysis to confirm elemental composition meets grade limits
7. Main Service Applications
- Power station boiler main steam pipelines, feedwater delivery pipes and auxiliary heating circuits
- Petrochemical refinery process pipelines for oil, fuel and medium-temperature steam
- General industrial fluid piping for water, compressed air and natural gas transportation
- Heating system pipelines, municipal thermal heating network pipes
- Low & medium pressure process header and manifold piping
8. Summary Paragraph
ASTM A106 is a globally recognized seamless carbon steel pipe standard with three strength grades (A/B/C) covering a full range of diameters and wall thicknesses under precise dimensional tolerances. With strictly regulated chemical composition and standardized mechanical property parameters including tensile strength, yield strength and elongation, these seamless pipes exhibit reliable high-temperature stability, good weldability and superior formability. All products undergo mandatory hydrostatic, tensile and flattening tests to ensure structural integrity. Cost-efficient and easy to fabricate, ASTM A106 Grade B as the mainstream product is extensively applied in power plant boiler piping, petrochemical fluid transport lines and industrial medium-temperature pressure piping systems for long-term stable service under moderate high temperature and pressure operating conditions.
