ASTM A501 Hot-Formed Welded Structural Steel Pipe
Overview
ASTM A501 is the standard specification for hot-formed welded and seamless carbon steel structural tubing in round shape only. It is designed for structural applications under normal atmospheric temperatures, offering an alternative to the cold-formed ASTM A500 pipe.
Grades & Mechanical Properties
| Grade | Tensile Strength (min) | Yield Strength (min) | Elongation in 2" (min) |
|---|---|---|---|
| Grade A | 45,000 psi (310 MPa) | 33,000 psi (230 MPa) | 25% |
| Grade B | 58,000 psi (400 MPa) | 42,000 psi (290 MPa) | 23% |
Note: Grade B is the most commonly specified.
Chemical Composition (Maximum %)
| Element | Grade A | Grade B |
|---|---|---|
| Carbon | 0.26 | 0.26 |
| Manganese | 1.35 | 1.35 |
| Phosphorus | 0.05 | 0.05 |
| Sulfur | 0.05 | 0.05 |
| Copper (min) | 0.20* | 0.20* |
Minimum copper applies only when enhanced atmospheric corrosion resistance is specified.
Manufacturing Process
The ERW (Electric Resistance Welded) pipe is produced by hot-forming at elevated temperatures, followed by high-frequency welding. This differs from ASTM A500, which is cold-formed. The process results in different mechanical characteristics and is generally used for thicker-walled, larger diameter structural columns.
Common Sizes & Tolerances (Typical)
| Parameter | Typical Range | Tolerance |
|---|---|---|
| Outside Diameter | 4.5" to 24"+ | ±0.5% of OD |
| Wall Thickness | 0.188" to 1.000"+ | +12.5%, -10% of nominal |
| Length | Up to 65 ft | +1/4", -0" for cut lengths |
Testing Requirements
Tensile Test: 2 tests per heat, per wall thickness.
Flattening Test: For ductility verification (2 per lot).
Reverse Flattening Test: For ERW pipe weld inspection (1 per lot).
Bend Test: For material ≤ 0.180" thick.
No hydrostatic test required (structural application).
Primary Applications
Structural Columns & Posts (heavy construction, high-rises)
Bearing Piles
Heavy Truss Members
Industrial Support Structures
It is commonly used where larger diameters and thicker walls are needed compared to standard cold-formed A500 HSS.
Key Comparison: A501 vs. A500
| Feature | ASTM A501 | ASTM A500 |
|---|---|---|
| Forming Process | Hot-formed | Cold-formed |
| Available Shapes | Round only | Round, Square, Rectangular |
| Typical Size Range | Larger OD, heavier wall | Smaller to medium OD |
| Yield Strength (Grade B) | 42,000 psi | 46,000 psi |
| Common Use | Heavy columns, piles | General structural (beams, trusses, railings) |
| Surface Finish | Mill scale (hot-rolled) | Smoother (cold-rolled option) |
Summary
ASTM A501 ERW pipe is a hot-formed structural steel product best suited for heavy load-bearing columns and compression members. Its key advantage is the availability of large diameters with thick walls via a hot-forming process. For most general structural framing with square/rectangular sections or lighter members, ASTM A500 is typically preferred.
