ASTM A500 Square Tube

ASTM A500/A500M — Carbon steel cold-formed round and special-shaped cross-section welded square tubes and seamless square tubes for structural use

Square tube is a name for square pipe, which is a steel pipe with equal side lengths. Most square tubes are mostly steel tubes, mostly structural square tubes, decorative square tubes, construction square tubes, etc.

ASTM is the American Society for Testing and Materials standard, and ASTM A500 is a common production standard for square tubes.

ASTM A500 square tube & pipe is rolled from strip steel after process treatment. Generally, the strip steel is unpacked, flattened, curled, and welded into a round tube, which is then rolled into a square tube and then cut to the required length. Usually 50 pieces per pack. Square tubes are divided into seamless square tubes and welded (ERW) square tubes. Seamless square tubes are made by extruding seamless round tubes.

Features of ASTM A500 Square Tube:

1. Excellent Strength-to-Weight Ratio
Hollow, closed sections are highly efficient at carrying bending, torsion, and compression loads. Compared to solid steel bars, they offer equivalent or even greater structural strength at a lower weight, reducing material costs and the weight of the structure.

2. Economical
The cold-forming and welding process offers high production efficiency and material utilization, making A500 square tube one of the most cost-effective structural steels.

3. Clean Appearance and Easy Handling
The relatively smooth surface with sharp corners creates a neat appearance. Its symmetrical geometry makes it easier to handle during storage, transportation, and installation.

4. Excellent Bending and Torsional Rigidity
The square section has equal moments of inertia about both principal axes (X and Y), providing equal bending resistance in both directions. Its closed cross-section also offers excellent torsional rigidity.

5. Easy Processing and Joining
It can be cut, drilled, welded, and mechanically joined relatively easily. The flat surface facilitates connection to other components, such as steel plates.

6. Various Strengths
The A500 standard specifies different strength grades (primarily Gr. B and Gr. C), allowing designers to select the most economical material based on their strength requirements.

Grade B: Yield strength ≥ 42 ksi (290 MPa), tensile strength ≥ 58 ksi (400 MPa) - currently the most commonly used
Grade C: Yield strength ≥ 50 ksi (345 MPa), tensile strength ≥ 62 ksi (427 MPa)
Grade D: Yield strength ≥ 36 ksi (250 MPa) - primarily used for round tubes

7. Wide Range of Surface Treatment Options
It can be used directly as "black tube" (with a slight oxide scale and oil film) or can be treated with various surface treatments such as spray coating and hot-dip galvanizing.

Potential Disadvantages:
Corrosion Resistance: As carbon steel, it requires surface protection (such as paint or galvanizing) to prevent rust when exposed to moisture. 

Corner stress concentration: Stress concentration may exist at sharp corners and requires special consideration under cyclic loading or impact loading.

Dimensional tolerance for ASTM A500 square tube:

1. External Dimensions: External dimensions shall be measured at least 2 inches (5 cm) from the pipe end and shall not differ from the required external dimensions by the appropriate values given in Table 3, including tolerances for concave and convex.
2. Wall Thickness: The minimum wall thickness measured at any point on the pipe cannot be less than 10% of the required wall thickness. The maximum wall thickness including the welds of the pipe shall not exceed 10% of the required wall thickness. ASTM A500 square tube wall thickness applies only to the center location.

3. Length: Structural pipes are usually produced in indefinite lengths of 5 feet (1.5 meters), multiple lengths and specified lengths. 

4. Straightness: Structural pipe flatness tolerance is 1/8 inch times total length divided by 5 feet (10 mm times meters).
5. Square surface: ASTM A500 square tube has each adjacent side at 90°, with a maximum allowable deviation of +2%.
6. Corner radius: The outer corner of each interface of the ASTM A500 square tube cannot exceed 3 times the required wall thickness.
7. Bending: The allowable tolerance of bending of ASTM A500 square tube is shown in the table below. The degree of curvature is determined by fixing one end of the tube on the flat plate and measuring the height of each corner of the bottom from the opposite end of the tube, and calculating the degree of curvature (the different heights of these corners), except that the degree of curvature can be determined by using some suitable measuring tools. . Bend testing cannot be done 2 inches (5 cm) from the pipe end.

Typical Applications:

ASTM A500 square tubing has an extremely wide range of applications, covering virtually all areas requiring lightweight, high-strength structural members.

1. Building Structures
Commercial and Industrial Buildings: Used as columns, roof trusses, purlins, curtain wall support frames, etc.
Stadiums and Airports: Grids, trusses, and support systems for large space structures.

2. Heavy Equipment and Machinery
Agricultural Machinery: Tractor guards, harvester frames.
Construction Machinery: Crane booms, excavator attachments, conveyor supports.
Trucks and Trailers: Chassis components, vehicle frames.

3. Infrastructure and Utilities
Bridges: Beams and railings for pedestrian bridges. 

Transmission towers and light poles: Structural support.
Docks and offshore platforms: Auxiliary structures.

4. Warehousing and material handling
Racking systems: Columns and beams for heavy-duty storage racks.
Containers and cages.

5. Home and commercial products
Furniture: Contemporary tables, chairs, desks, and shelves.
Store displays.
Stairs and guardrails.

Conclusion:
ASTM A500 square tubing is one of the most versatile and economical components in modern steel construction. It offers an excellent balance of strength, weight, cost, and workability.

When purchasing or specifying ASTM A500 square tubing, please be aware of the following:
Shape: Square tubing.
Standard: ASTM A500.
Grade: Typically A500 Grade C (high strength, most commonly used) or Grade B. Dimensions: The outer wall dimensions (e.g., 2" x 2") and wall thickness (e.g., 1/4"). Wall thickness is usually expressed in inches.
Surface Requirements: Whether the pipe needs to be galvanized, painted, or left as black.

Go here to learn more about "ASTM A500 rectangular tube" or "Square tube manufacturing process"