What Is A500 Grade B Tubing?
ASTM A500 Grade B is a cold-formed welded carbon steel structural tubing grade with a minimum yield strength of 290 MPa and a minimum tensile strength of 400 MPa. In square and rectangular shapes it is one of the most specified HSS products for structural engineering because of its strength, efficiency and clean appearance.
The tubing is formed from steel strip and welded by electric resistance welding, then cut to length with square ends ready for fabrication.
Mechanical Properties
| Property | Grade B Requirement |
|---|---|
| Yield strength, min | 290 MPa (42,000 psi) |
| Tensile strength, min | 400 MPa (58,000 psi) |
| Elongation | Per standard table |
| Wall thickness tolerance | About +/-10% |
The combination of strength and ductility allows Grade B tubing to be welded, drilled, punched and formed without cracking, which makes it a favorite of fabricators.
Dimensional Tolerances
Square and rectangular tubing is produced with controlled outside dimensions, wall thickness, straightness and corner configuration. Typical outside dimension tolerances are about plus or minus 0.020 inch for smaller sections, scaling with size. These tolerances ensure that connections, bolted splices and architectural details fit as designed.
Applications
| Field | Typical Use |
|---|---|
| Building structures | Columns, beams, roof trusses, bracing |
| Bridges and infrastructure | Guardrails, pedestrian structures, sign supports |
| Machinery | Frames, bases, gantries, conveyor supports |
| Fabrication | Fences, railings, racks, shelving, trailers |
The smooth interior and attractive exterior make the tubing suitable for exposed architectural steel and for applications requiring painting or powder coating.
Testing and Inspection
A500 Grade B tubing is verified by chemical analysis, tensile testing and flattening tests, with dimensional and surface inspection on every length. The weld seam is examined by non-destructive methods where specified, and mill certificates provide heat traceability.
FAQ
Q1. What is the yield strength of A500 Grade B square tubing?
The minimum yield strength is 42,000 psi, equal to 290 MPa, with a minimum tensile strength of 58,000 psi.
Q2. What sizes are available?
Square sections range from about 1/2 inch to 16 inches per side and rectangular sections from 1 by 2 inches upward, with walls from 0.065 to 0.625 inch.
Q3. Can Grade B tubing be galvanized?
Yes, A500 Grade B tubing is routinely hot-dip galvanized for outdoor structures such as guardrails, poles and fencing.
Q4. What is the difference between Grade B and Grade D?
Grade D provides 50,000 psi minimum yield for square and rectangular shapes, while Grade B provides 42,000 psi and is more economical for lighter loads.
Q5. Is A500 Grade B tubing weldable?
Yes, it welds easily with standard structural procedures, which is essential for field connections in building construction.
Q6. What is HSS 4 by 2 by 0.125?
It is a designation for rectangular hollow structural section, 4 inches by 2 inches outside with a 0.125 inch wall, commonly used for beams and columns.
