ASTM A500: Longitudinally Submerged Arc Welded Pipe - Technical Clarification and Specification
It is critically important to clarify that ASTM A500 does not cover pipe manufactured using the longitudinal Submerged Arc Welding (SAW) process. The standard explicitly defines its scope as covering cold-formed welded and seamless carbon steel round, square, rectangular, or special shape structural tubing, where the welding process is electric-welding (ERW/HFI).
Therefore, the term "ASTM A500 Longitudinally Submerged Arc Welded Pipe" is non-standard. In practice, this request typically means the user wants structural tubing with the mechanical and chemical properties of ASTM A500 but fabricated using the higher-strength SAW process, often for large, heavy-walled sections. The correct standard for such a product would typically be ASTM A1085 or a project-specific specification.
The information below provides a hypothetical specification for SAW structural tubing that meets or exceeds the core requirements of ASTM A500.
Hypothetical Product: SAW Structural Tubing to ASTM A500 Properties
This describes a longitudinally welded structural tube made from plate/coil, welded via the Submerged Arc Welding (SAW) process, and produced to meet the dimensional tolerances, chemical composition, and mechanical properties of ASTM A500.
Primary Use: Heavy structural applications requiring superior weld integrity and load-bearing capacity, such as bridge girders, high-rise building columns, heavy-duty support frames, and crane booms. Used where standard electric-welded (ERW) A500 tubing may not suffice due to wall thickness or critical weld performance requirements.
Key Advantage: The SAW weld seam has excellent penetration and toughness, often matching or exceeding the strength of the base metal, which is crucial for highly stressed structural members.
Common Shapes: Primarily square (HSS) and rectangular (HSS) hollow structural sections, though large-diameter circular sections are also possible.
Condition: Supplied as-welded. Stress relieving may be specified for severe service conditions.
Technical Specification Tables (Based on ASTM A500 Requirements)
Table 1: Grades and Mechanical Properties (Minimum)
(These are the standard A500 requirements which the SAW product would meet.)
| Grade (Shape) | Tensile Strength, min (ksi / MPa) | Yield Strength, min (ksi / MPa) |
|---|---|---|
| Grade A (Round) | 45 / 310 | 39 / 270 |
| Grade B (Round) | 58 / 400 | 46 / 315 |
| Grade C (Round) | 62 / 425 | 50 / 345 |
| Grade A (Square/Rect.) | 45 / 310 | 39 / 270 |
| Grade B (Square/Rect.) | 58 / 400 | 46 / 315 |
| Grade C (Square/Rect.) | 62 / 425 | 50 / 345 |
Note: Elongation requirements also apply per ASTM A500 and vary by grade and wall thickness.
Table 2: Chemical Composition (Heat Analysis, Maximum %)
(Standard A500 limits which the base plate for SAW tubing would adhere to.)
| Grade | Carbon (C) | Manganese (Mn) | Phosphorus (P) | Sulfur (S) | Copper (Cu) min* |
|---|---|---|---|---|---|
| A | 0.26 | 1.35 | 0.035 | 0.035 | 0.20 |
| B | 0.26 | 1.35 | 0.035 | 0.035 | 0.20 |
| C | 0.23 | 1.35 | 0.035 | 0.035 | 0.20 |
*When steel with a specified minimum copper content is required.
Table 3: Manufacturing Process & Key Tests for SAW Tubing
(Proposed quality control for a SAW product.)
| Aspect | Description |
|---|---|
| Primary Process | Plate or strip is cold-formed into the desired shape (round, square, rectangular). The longitudinal seam is welded using the Submerged Arc Welding (SAW) process, typically as a double-pass (inside and outside) weld for heavy sections. |
| Flattening Test | Mandatory. A specimen is flattened to demonstrate the weld and base metal's ductility. For SAW tubing, this test is crucial to prove the weld will not open under bending loads. |
| Weld Tensile Test | Transverse tension specimens taken across the weld must exhibit a tensile strength not less than the minimum specified for the grade of tubing. The fracture location is often required to be outside the weld zone, demonstrating the weld's overmatching strength. |
| Non-Destructive Examination (NDE) | Ultrasonic Testing (UT) or Radiographic Testing (RT) of the entire weld seam is standard and highly recommended for critical structural SAW seams to ensure internal soundness. |
| Dimensional Tolerances | Must conform to the stringent outer dimensions, wall thickness, and squareness/rectangularity tolerances specified in ASTM A500 for cold-formed structural tubing. |
Comparison and Correct Standards
| Feature | Standard ASTM A500 Tubing | "A500-Spec" SAW Tubing (Hypothetical) | Correct Standard for SAW Structural Tubing |
|---|---|---|---|
| Primary Process | Electric Resistance Welding (ERW) or Seamless | Longitudinal Submerged Arc Welding (SAW) | ASTM A1085, ASTM A1065, or project specifications |
| Typical Application | General construction, frames, supports | Heavy column, bridge, or high-stress structural applications | Same as hypothetical |
| Weld Quality | Good, suitable for standard loads | Excellent, deep penetration, high toughness | Excellent |
| Common Wall Thickness | Light to moderate | Moderate to very heavy | Moderate to very heavy |
| Key Standard Reference | ASTM A500 | Project-specific specification citing A500 properties + SAW process | ASTM A1085 (allows continuous weld processes) |
Conclusion and Recommendation
While a product described as "ASTM A500 SAW Pipe" is not covered by the A500 standard itself, it represents a logical demand for high-performance structural tubing. For procurement:
For square/rectangular sections: Specify ASTM A1085, which is the modern successor to A500 and explicitly allows for continuously welded products (which can include SAW). It has higher minimum yield strengths (50 ksi for all shapes) and stricter quality provisions.
For circular sections: Specify ASTM A53 Grade B for structural purposes, or ASTM A252 for piling, with the understanding it will be SAW welded.
For custom projects: Create a project specification that states: *"Structural tubing shall meet all mechanical properties, chemical requirements, and dimensional tolerances of ASTM A500, Grade C. The tubing shall be manufactured using the double-sided longitudinal Submerged Arc Welding (SAW) process. The entire weld seam shall be 100% ultrasonically inspected..."*
In summary, "ASTM A500 Longitudinally Submerged Arc Welded Pipe" is a market-driven description for a high-strength, welded structural section. The correct approach is to use standards like ASTM A1085 or to write a clear, performance-based specification that references the desired properties of A500 while mandating the SAW process and appropriate testing.
