ASTM A36 Electric Resistance Welded (ERW) Pipe
Basic Overview
A standard specification for carbon structural steel that is commonly used in welded pipe form for general structural applications. ASTM A36 is primarily a plate and structural shape standard that has been widely adapted for ERW pipe manufacturing for construction and general fabrication purposes.
Name Explanation
| Part | Meaning |
|---|---|
| ASTM | ASTM International |
| A36 | Standard specification for carbon structural steel |
| Electric Resistance Welded | Manufacturing process – pipe formed from plate/sheet and welded longitudinally |
Key Features of A36 ERW Pipe
| Feature | Description |
|---|---|
| Material Type | Carbon Structural Steel |
| Manufacturing | Electric Resistance Welded (ERW) – longitudinal weld seam present |
| Primary Use | Structural applications – building frames, bridges, general fabrication |
| Key Properties | Good strength, excellent weldability, moderate ductility |
| Common Forms | Round, square, rectangular sections |
| Designation Origin | Originally a plate/beam standard, widely adopted for pipe/tube applications |
Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.25–0.29% max (varies by thickness) |
| Silicon (Si) | 0.15–0.40% |
| Manganese (Mn) | 0.80–1.20% |
| Phosphorus (P) | 0.04% max |
| Sulfur (S) | 0.05% max |
| Copper (Cu) | 0.20% min (when copper steel is specified) |
Note: Composition varies slightly depending on thickness. Thicker sections allow slightly higher carbon .
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength | 250 MPa (36,000 psi) minimum |
| Tensile Strength | 400–550 MPa (58–80 ksi) |
| Elongation | 20–23% minimum (depends on thickness) |
Note: Yield strength may decrease slightly as material thickness increases beyond 200mm .
Comparison Table: A36 vs. Other Structural/Welded Pipe Grades
| Aspect | ASTM A36 ERW | ASTM A500 Gr.C (HSS) | ASTM A53 Gr.B |
|---|---|---|---|
| Primary Origin | Plate/structural standard | Structural tubing standard | Pipe standard |
| Yield Strength | 250 MPa (36 ksi) | 317 MPa (46 ksi) | 240 MPa (35 ksi) |
| Tensile Strength | 400–550 MPa | 427 MPa (62 ksi) min | 415 MPa (60 ksi) min |
| Primary Market | General fabrication | Structural framing | Fluid conveyance |
| Common Applications | Beams, columns, welded structures | Building columns, trusses | Plumbing, low-pressure lines |
| Weldability | Excellent | Good | Good |
Common Applications
| Industry | Applications |
|---|---|
| Construction | Building frames, columns, beams, scaffolding, bridge structures |
| Infrastructure | Signage poles, light standards, highway barriers |
| Industrial | Equipment frames, machine bases, conveyor systems |
| Agriculture | Greenhouse frames, irrigation supports, livestock equipment |
| General Fabrication | Handrails, fencing, structural supports, platforms |
| Mechanical | Light machinery frames, guards, supports |
ERW Manufacturing & Availability
| Parameter | Typical Range |
|---|---|
| Outer Diameter | 12.7mm to 325mm (up to 1200mm available from some mills) |
| Wall Thickness | 1.2mm to 22mm |
| Length | 6m to 12m standard (customizable) |
| Surface Finish | Black (mill finish), painted, galvanized, oiled |
| Shapes | Round, square, rectangular |
International Equivalents
| Standard | Grade Equivalent |
|---|---|
| China | Q235 |
| Japan | SS400 |
| Europe | S235JR |
| Germany | ST37-2 |
Fabrication & Weldability
| Aspect | Rating |
|---|---|
| Weldability | Excellent – suitable for all common welding methods |
| Cutting | Good machinability, clean cuts |
| Forming | Good for bending, rolling, shaping |
| Welding Methods | SMAW, GMAW, GTAW, SAW all suitable |
| Preheat | Generally not required for typical thicknesses |
Industry Context & Selection Notes
1. Not a Traditional Pipe Standard
Important: ASTM A36 is technically a plate and structural shape standard that has been widely adopted for pipe and tube manufacturing . It is not originally a pipe specification like A53 or A106.
2. Why Specify A36 ERW Pipe?
Familiarity – widely recognized by fabricators and engineers
Availability – commonly produced by mills worldwide
Cost-effective – economical for structural applications
Good properties – balanced strength and weldability
3. When to Choose A36 ERW
Select A36 ERW for:
General structural framing and supports
Non-code welded structures
Fabrication projects where A36 plate/beam is already specified
Applications where ASTM A500 structural tubing is not required
4. When to Choose Alternatives
Consider ASTM A500 Gr.C for:
Higher strength requirements (46 ksi vs. 36 ksi)
Hollow Structural Section (HSS) design
Building code compliance requiring specific HSS standards
Consider ASTM A53 Gr.B for:
Pressure applications or fluid conveyance
Piping system code compliance
Coating & Protection Options
| Coating Type | Typical Application |
|---|---|
| Black (bare) | Indoor use, further processing |
| Primer-painted | Temporary rust protection |
| Galvanized | Outdoor corrosion protection |
| Varnish/oiled | Short-term transit protection |
| PE-coated | Buried or harsh environments |
Testing & Quality
| Test Type | Purpose |
|---|---|
| Chemical Analysis | Verify composition |
| Tensile Test | Confirm yield and tensile strength |
| Flattening Test | Check ductility |
| Bend Test | Verify formability |
| Hydrostatic Test | Optional – not typically required for structural use |
| Ultrasonic Examination | Detect internal defects (when specified) |
Final Takeaway: ASTM A36 ERW Pipe is a carbon structural steel pipe widely used for general fabrication and construction applications. Originally a plate and beam standard, A36 has been adapted for ERW pipe manufacturing and is valued for its good strength, excellent weldability, and cost-effectiveness. It is commonly specified for building frames, supports, infrastructure projects, and general structural work where higher-strength HSS tubing (A500) is not required. For pressure applications, however, ASTM A53 or A106 should be specified instead.
