ASTM A252 Grade 2 Spiral Welded Steel Pipe (SSAW)
Basic Overview
ASTM A252 Grade 2 Spiral Submerged Arc Welded (SSAW) steel pipe is the most commonly used grade for foundation piling applications. It offers a balanced combination of strength, weldability, and cost-effectiveness, making it the standard choice for medium to high-load-bearing structures such as bridge foundations, marine piling, and building supports .
Name Explanation
| Part | Meaning |
|---|---|
| ASTM | ASTM International |
| A252 | Standard specification for welded and seamless steel pipe piles |
| Grade 2 | Intermediate strength grade – most commonly specified for general piling applications |
| SSAW | Spiral Submerged Arc Welding – double-sided welding with filler metal; weld seam runs continuously in a spiral along the pipe length |
Key Specifications
| Attribute | Description |
|---|---|
| Standard | ASTM A252 / A252M – "Standard Specification for Welded and Seamless Steel Pipe Piles" |
| Primary Function | Structural foundation support – permanent load-carrying members or shells for cast-in-place concrete piles |
| Manufacturing Process | Spiral Submerged Arc Welding (SSAW) – double-sided automatic welding |
| Minimum Yield Strength | 240 MPa (35,000 psi) |
| Minimum Tensile Strength | 415 MPa (60,000 psi) |
| Minimum Elongation | 25% |
| Size Range (SSAW) | 219 mm to 4064 mm (8" to 160") OD |
| Wall Thickness | 3.2 mm to 60 mm (common range 6-25.4 mm) |
| Length | 6 m to 32 m standard; up to 24 m typical |
| End Finishes | Plain ends (PE) standard; beveled ends for field welding (30° bevel) |
Chemical Composition
ASTM A252 specifies only maximum limits for phosphorus. All three grades share the same composition limits :
| Element | Maximum % |
|---|---|
| Carbon (C) | 0.26% (typical, not mandated) |
| Manganese (Mn) | 1.60% (typical, not mandated) |
| Silicon (Si) | 0.45% (typical, not mandated) |
| Phosphorus (P) | 0.050% (mandatory) |
| Sulfur (S) | 0.030% (typical) |
Note: The standard focuses on mechanical properties rather than strict chemical composition. The steel shall contain no more than 0.050% phosphorus .
Mechanical Properties Comparison
| Grade | Yield Strength (min) | Tensile Strength (min) | Elongation (min) | Strength vs. Grade 1 |
|---|---|---|---|---|
| Grade 1 | 205 MPa (30,000 psi) | 345 MPa (50,000 psi) | 30% | Baseline |
| Grade 2 | 240 MPa (35,000 psi) | 415 MPa (60,000 psi) | 25% | +17% yield |
| Grade 3 | 310 MPa (45,000 psi) | 455 MPa (66,000 psi) | 20% | +51% yield |
Source:
Dimensional Tolerances
| Parameter | Tolerance |
|---|---|
| Outside Diameter (OD ≤ 508mm) | ±1% or ±1.0mm (whichever is greater) |
| Outside Diameter (OD > 508mm) | ±1% or ±4.0mm (whichever is greater) |
| Wall Thickness | +15% / -12.5% of nominal |
| Weight | +15% / -5% of theoretical weight |
| Straightness | ≤ 0.1% of total length |
Typical Size Availability (SSAW):
| OD (inch) | OD (mm) | Wall Thickness Range (mm) |
|---|---|---|
| 16" | 406 | 6.0 - 14.0 |
| 20" | 508 | 6.0 - 16.0 |
| 24" | 610 | 6.0 - 18.0 |
| 30" | 762 | 7.0 - 21.0 |
| 36" | 914 | 8.0 - 24.0 |
| 40" | 1016 | 8.0 - 26.0 |
| 48" | 1219 | 9.0 - 28.0 |
| 56" | 1422 | 10.0 - 29.0 |
| 60" | 1524 | 10.0 - 29.0 |
| 64" | 1626 | 10.0 - 30.0 |
| 72" | 1829 | 10.0 - 30.0 |
SSAW Manufacturing Process
Spiral welded pipes under ASTM A252 are produced using the following process :
| Step | Description |
|---|---|
| 1. Raw Material Preparation | Steel coils meeting ASTM A252 requirements are leveled and edge-milled |
| 2. Edge Preparation | Strip edges are milled for proper welding |
| 3. Spiral Forming | Steel strip is continuously formed into a cylindrical shape at a specific helix angle |
| 4. Submerged Arc Welding | Double-sided automatic submerged arc welding (inside and outside) creates the spiral seam |
| 5. Weld NDT | 100% ultrasonic inspection of the weld seam |
| 6. Hydrostatic Testing | Each pipe tested (optional per ASTM A252, but standard practice) |
| 7. End Finishing | Plain or beveled ends for field welding |
Testing & Inspection Requirements
| Test Type | Requirement | Notes |
|---|---|---|
| Chemical Analysis | Per heat lot | Phosphorus limit enforced |
| Tensile Test | Per lot | Verifies yield and tensile strength |
| Flattening Test | Required | Checks ductility and weld integrity |
| Bend Test | Mandatory – 180° bend test on weld specimen | Verifies weld ductility |
| Hydrostatic Test | Optional per ASTM A252 | Not mandatory for piling pipes |
| Ultrasonic Inspection | 100% of weld seam | Standard practice for SSAW |
| Dimensional Inspection | 100% | Per ASTM A252 tolerances |
| Mill Test Certificate | EN 10204 Type 3.1B | Provided with full test results |
Applications
Grade 2 is the standard choice for most piling applications :
| Application | Description |
|---|---|
| Bridge Foundations | Pier and abutment support for cross-river/sea bridges |
| Building Foundations | Medium to high-rise building deep foundations |
| Marine Structures | Ports, docks, wharves requiring corrosion-resistant coatings |
| Industrial Plant Foundations | Heavy equipment foundation piles |
| Land Reclamation | Coastal embankments, reclamation bulkheads |
| Retaining Walls | Lateral soil pressure resistance |
| Temporary Works | Foundation pit support for subways/buildings |
Grade Selection Guidance
| Grade | Yield Strength | Best For |
|---|---|---|
| Grade 1 | 205 MPa (30 ksi) | Light-load applications, good soil conditions, temporary structures, most economical |
| Grade 2 | 240 MPa (35 ksi) | Most common – medium-rise buildings, bridge foundations, general piling, marine structures |
| Grade 3 | 310 MPa (45 ksi) | Heavy-load applications, large bridges, offshore platforms, seismic zones |
For most general foundation applications, Grade 2 is the recommended default.
Advantages of SSAW for Grade 2 Piling
| Advantage | Description |
|---|---|
| Optimal Strength-to-Cost Ratio | Grade 2 offers the best balance among A252 grades – 17% higher strength than Grade 1 at modest cost premium |
| Large Diameter Capability | SSAW produces pipes from 8" to 160" OD – ideal for large-diameter piling applications |
| Long Lengths | Up to 32m lengths reduce field splicing requirements |
| High Weld Integrity | 100% UT inspection of weld seam ensures quality |
| Spiral Stress Distribution | Spiral weld disperses stress more evenly during pile driving |
| Material Efficiency | Can use narrower steel strips to produce large-diameter pipes |
| Corrosion Protection Options | FBE, 3LPE, coal tar epoxy, concrete weight coating available |
Important Considerations
1. Grade 2 vs. Grade 1 and Grade 3
Grade 1: Light-load applications, good soil conditions, temporary structures
Grade 2: Most common grade – medium-rise buildings, bridge foundations, industrial plants, marine structures
Grade 3: Heavy-load applications, large bridges, offshore platforms, seismic zones
2. No Mandatory Hydrostatic Testing
ASTM A252 does not require hydrostatic testing because piling pipes are filled with concrete and not used for fluid conveyance
However, most manufacturers provide hydrostatic testing as standard practice
3. Bend Test is Critical
The 180° bend test is mandatory for piling pipes and directly assesses the weld's ductility under bending stresses similar to those during installation
4. Corrosion Protection
For permanent structures, specify appropriate coatings based on environmental conditions:
FBE/3LPE: For buried piles and harsh environments (50+ year service life)
Coal Tar Epoxy: For marine applications
Concrete Weight Coating (CWC): For offshore/subsea piles
Galvanized: For above-ground applications
5. End Reinforcements
For hard driving conditions, specify end reinforcements :
Driving shoe: Protects pile tip during driving through dense layers
Driving band: External ring at tip to reinforce end
Internal stiffeners: Prevent buckling under hard driving
6. Supplementary Requirements
ASTM A252 includes optional supplementary requirements that can be specified for critical applications :
S1: Charpy V-Notch Impact Test (for low-temperature applications)
S2: Drop-Weight Test (fracture toughness verification)
S3: Microstructure Examination (weld and HAZ quality check)
S4: Ultrasonic Lamination Test (detect plate imperfections)
7. Third-Party Inspection
Available inspection services include SGS, BV, Lloyds
Summary
ASTM A252 Grade 2 Spiral Submerged Arc Welded (SSAW) steel pipe is the standard, most commonly used grade for foundation piling applications. With minimum yield strength of 35,000 psi (240 MPa) – 17% higher than Grade 1 – and tensile strength of 60,000 psi (415 MPa), Grade 2 offers the optimal balance of strength, weldability, and cost-effectiveness for medium to high-load-bearing applications .
Key features:
Material standard: ASTM A252 Grade 2 – most common grade for general piling
Yield strength: 240 MPa (35,000 psi) minimum – +17% vs Grade 1
Tensile strength: 415 MPa (60,000 psi) minimum
Elongation: 25% minimum – good ductility for installation
SSAW manufacturing produces pipes from 8" to 160" OD with wall thickness up to 60 mm
Double-sided welding creates a single high-quality weld nugget
100% ultrasonic inspection of weld seam ensures quality
Bend test mandatory – critical for piling applications
Cost-effective – best balance of performance and economy
Common applications include:
Bridge foundations and pier supports
Medium to high-rise building foundations
Marine structures (docks, wharves, ports)
Industrial plant foundations
Land reclamation and coastal embankments
Retaining walls and temporary shoring
When ordering, specify: ASTM A252 Grade 2, SSAW (Spiral Submerged Arc Welded), Size (OD x WT), Length, End Finish (plain/beveled), Coating Requirements (if needed), and Mill Test Certificate to EN 10204 Type 3.1B. For most general piling applications, Grade 2 is the recommended default .
