ASTM A252: Standard Specification for Welded and Seamless Steel Pipe Piles
ASTM A252 covers seamless, electric-resistance welded, and welded (double- and single-submerged arc welded) steel pipe piles. As the name implies, these pipes are specifically designed for use as structural foundations (piles) to be driven into the ground to support buildings, bridges, and other structures.
Longitudinal Submerged Arc Welding (SAW) is one of the primary and most common manufacturing methods for large-diameter, thick-walled pipe piles under this specification. The SAW process produces a robust, high-integrity longitudinal seam capable of withstanding the immense stresses of pile driving.
Key Characteristics and Applications
Primary Use: Foundation Piling. The pipe is driven into the soil, often filled with concrete to form a composite structural column. It is not intended for pressure service or fluid transport.
Driving Method: Designed to be driven by impact or vibratory hammers. The weld seam, ends, and material must have sufficient toughness to resist cracking during installation.
Surface Condition: Typically supplied in a bare (uncoated), as-welded condition. It may have a light mill varnish or primer but is not galvanized or painted for corrosion protection in most soil applications.
Common Sizes: Available in a wide range of diameters and wall thicknesses to meet engineering load requirements. Outer Diameters commonly range from 10 inches (254 mm) to over 48 inches (1200 mm), with walls often exceeding 0.5 inches (12.7 mm).
Technical Specification Tables
Table 1: Grades and Mechanical Properties
These are the minimum requirements for the finished pipe.
| Grade | Yield Strength, min (psi / MPa) | Tensile Strength, min (psi / MPa) |
|---|---|---|
| 1 | 30,000 / 205 | 50,000 / 345 |
| 2 | 35,000 / 240 | 60,000 / 415 |
| 3 | 45,000 / 310 | 66,000 / 455 |
*Note: Elongation is not a specified requirement in ASTM A252. The focus is on strength for load-bearing capacity and weld integrity for driveability.*
Table 2: Chemical Composition (Heat Analysis, Maximum %)
Chemical requirements are minimal, as strength and weldability are the primary concerns.
| Grade | Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) |
|---|---|---|---|---|
| 1, 2, 3 | 0.26 | 1.35 | 0.04 | 0.05 |
*Note: Grades 2 and 3 achieve their higher strength through alloying (primarily higher Manganese) and/or controlled rolling practices, within the maximum limits.*
Table 3: Manufacturing Processes and Weld Seam Types
This standard allows for multiple manufacturing methods.
| Process Type | Description | Typical Wall Thickness / Size |
|---|---|---|
| Seamless (S) | Produced by piercing a solid billet. No longitudinal weld. | All, but may be cost-prohibitive for very large diameters. |
| Electric Resistance Welded (ERW) | Formed from coil and welded using electrical resistance heat and pressure. | Smaller diameters and thinner walls common for piling. |
| Double Submerged Arc Welded (DSAW) | The most common for large piles. Plate is formed and welded with one SAW pass on the inside and one on the outside of the seam. | Standard for heavy-wall, large-diameter pipe piles (e.g., NPS 16" and up). |
| Single Submerged Arc Welded (SSAW) | Plate is formed and welded with a single SAW pass, typically from the outside. May be used for specific applications or smaller sizes. | Varies. |
Table 4: Key Testing Requirements
| Test Name | Description | Purpose for Piling |
|---|---|---|
| Flattening Test | A ring sample is flattened to a specified distance (H) between plates. No weld opening or crack is permitted. | Crucial test. Demonstrates the weld ductility and ability of the pipe to withstand the bending stresses of driving without seam failure. |
| Hydrostatic Test | Optional, unless specified by the purchaser. If performed, the test pressure is calculated based on wall thickness and a stress level not exceeding the specified yield. | Not a routine requirement for non-pressure applications like piling. |
| Transverse Tension Test | A specimen cut perpendicularly across the weld is pulled to failure. The weld metal must meet the minimum tensile strength of the pipe grade. | Verifies the weld strength is equal to or greater than the pipe body. |
| Bend Test | A guided bend test specimen from the weld area is bent around a mandrel. The convex surface must show no open defects >1/8 in (3.2 mm). | Demonstrates soundness and ductility of the weld and heat-affected zone. |
Important Distinctions and Marking
ASTM A252 vs. ASTM A53 / API 5L: This is a critical distinction.
A252: A structural product standard for foundation piles. Its properties are optimized for axial compression loads and impact driving.
A53 / API 5L: Pipe standards primarily for fluid conveyance under pressure. They have different chemical balances, mandatory pressure testing, and often stricter elongation requirements.
Grade Selection:
Grade 1: For low load requirements or easy driving conditions.
Grade 2: The most commonly specified grade for general piling applications.
Grade 3: For high-load applications or where harder driving conditions are expected, requiring higher strength.
Marking: Pipe piles are typically stenciled with:
ASTM A252
Grade (e.g., GR 2)
Manufacturer's Name or Symbol
Size (Nominal Pipe Size or Outside Diameter and Wall Thickness)
Heat Number (for traceability)
Process (often implied by the standard, but may be noted as DSAW)
In summary, ASTM A252 Longitudinally Submerged Arc Welded Pipe is a high-strength, heavy-duty structural product engineered specifically for deep foundation piling. The Double Submerged Arc Welding (DSAW) process is the industry-preferred method for manufacturing these large-diameter, thick-walled piles due to the exceptional strength and reliability of its weld seam.
