What ASTM A500 Covers
ASTM A500/A500M is the standard specification for cold-formed welded and seamless carbon steel structural tubing in round, square and rectangular shapes. The tubing is produced by cold forming strip or plate into a hollow section with a continuous weld, or as a seamless product, and it is used as a structural member rather than as a pressure or mechanical tube. The specification defines grades A, B, C and D and assigns separate mechanical values to round sections and to shaped, that is square and rectangular, sections.
Because the tubing is cold formed, the standard treats the delivered wall thickness as a nominal value with a permitted minus tolerance, and structural design practice compensates by using a reduced design wall thickness in section property calculations.
Cross-Standard Comparison
| Standard | Product | Example grade | Min yield | Tensile | Impact |
|---|---|---|---|---|---|
| ASTM A500/A500M | Cold-formed welded and seamless structural tubing | Grade C, shaped sections | 345 MPa | 427 MPa min | Not required |
| EN 10219-1 | Cold formed welded structural hollow sections | S355J2H | 355 MPa | 470-630 MPa | 27 J at -20 degrees C |
| EN 10210-1 | Hot finished structural hollow sections | S355J2H | 355 MPa | 470-630 MPa | 27 J at -20 degrees C |
| JIS G3444 | Carbon steel tubes for general structural purposes | STK400 | 235 MPa | 400 MPa min | Not required |
| CSA G40.21 | Structural quality steel | 350W | 350 MPa | 450-650 MPa | Per class suffix |
| GB/T 6728 | Cold-formed hollow sections for general structures | Q355 of GB/T 1591 | 355 MPa | 470-630 MPa | Per grade quality |
Two points explain most of the differences in the table. First, the EN, JIS and GB systems publish yield and tensile values that change with wall thickness, while ASTM A500 states a single minimum value for a grade and section type. Second, the EN 10219 and EN 10210 grades in the H quality carry a guaranteed Charpy value, so a designer working to the European system obtains notch toughness as part of the grade designation rather than as a supplementary requirement.
Wall Tolerance and Design Consequences
The wall thickness tolerance in ASTM A500 is a minus tolerance of 10% of nominal. Structural design codes therefore require a design thickness reduction: calculations for square and rectangular sections are typically based on 0.93 times the nominal wall thickness, and the rounded corners of the section, which are a product of cold forming, affect the calculated section properties as well. A designer converting a project from an EN grade to A500, or the reverse, must repeat the section capacity check rather than assume that similar nominal dimensions give the same result.
Can Other Tube Standards Substitute for A500?
Pipe made to ASTM A53 is intended for mechanical and pressure duties and carries lower yield strength than structural tubing; it is not recommended as a direct substitute in structural applications.
Tubing made to ASTM A513 is a mechanical tubing specification in which dimensional tolerance is controlled but strength is not guaranteed unless it is separately specified, so it does not replace A500 in a designed structural member.
ASTM A1085 is a newer structural tubing specification that sets a single 50 ksi yield grade with a higher minimum tensile strength and a mandatory notch toughness requirement, together with a tighter wall tolerance than A500.
EN 10219-1 S355J2H, JIS G3444 STK490 and GB/T 6728 Q355 hollow sections can all serve the same structural purpose, but each carries its own thickness dependent strength values and tolerance rules.
Testing and Ordering Points
ASTM A500 requires tension tests and flattening tests on specimens from the finished tubing, and chemical limits apply to carbon, manganese, phosphorus, sulphur and copper.
Impact testing is not part of the base A500 requirement, so a project needing notch toughness must order it as a supplementary requirement.
State the grade, the section shape and size, the nominal wall thickness and the length, and confirm whether welded or seamless tubing is required.
Where a project mixes standards, record the equivalent grade relationship and the basis of the substitution in the design documentation.
Check the mill certificate for the actual wall thickness and the test results, since the design capacity of a structural tube depends on the delivered wall.
FAQ
Q: Can ASTM A53 pipe be used instead of A500 tubing in a structure?
It is not recommended. A53 is made for mechanical and pressure service and has lower yield strength, so it is less efficient and does not match the design basis of a structural member.
Q: What is the European equivalent of ASTM A500?
Cold formed welded structural hollow sections to EN 10219-1, commonly in grade S355J2H, are the usual European counterpart, with guaranteed notch toughness values.
Q: Why do designers reduce the wall thickness of A500 tubing?
Because the specification permits a minus tolerance of 10% on nominal wall, design codes require calculations based on a reduced design thickness, typically 0.93 times the nominal value.
Q: Does A500 require impact testing?
No. Notch toughness is not part of the base specification and must be ordered as a supplementary requirement when the design or the client demands it.
Q: Is ASTM A500 still current?
Yes. A500/A500M remains an active international standard, and its grades are recognised and adopted by standards bodies outside the United States.
Q: What tests does A500 require on the finished tube?
Tension tests and flattening tests are required, together with conformity to the chemical composition limits set out in the specification.
