ASTM A500 Rectangular Tube

What is ASTM A500 rectangular tube?

Rectangular tube is a hollow long steel material, also known as flat tube, flat square tube or square flat tube (as the name implies). When the bending and torsional strength are the same, the weight is lighter, so it is widely used in manufacturing mechanical parts and engineering structures.

ASTM A500 is the American Society for Testing and Materials (ASTM) standard specification for cold-formed welded and seamless carbon steel structural tubing. ASTM A500 rectangular tubing specifically refers to hollow structural steel sections with a rectangular cross-section that conform to this standard. ASTM A500 Gr. B rectangular tubing is the most commonly used and standard rectangular hollow structural steel section in North America and internationally for building and structural engineering.

Features and advantages of ASTM A500 rectangular tubes:

As a widely used structural material in the construction and engineering fields, ASTM A500 Rectangular tubes have the following significant features and advantages:

1. Excellent structural strength
Made by cold forming process, with higher yield strength and tensile strength (B-grade yield strength ≥ 290MPa)
Rectangular cross-section design provides better bending and torsion resistance
Particularly suitable for structural applications that bear multi-directional loads

2. High dimensional accuracy
Strict dimensional tolerance control (±0.5% outer diameter, ±10% wall thickness)
Right-angle edge design ensures precise docking during assembly
High surface flatness for easy subsequent processing and welding

3. Great design flexibility
Provide a variety of wall thickness options
Wide range of sizes
Special sizes can be customized according to project requirements

4. Strong construction convenience
Flat surface is easy to paint and anti-corrosion treatment
Right-angle design simplifies the connection node structure
Light weight but high strength, reducing transportation and installation costs

5. Outstanding economy
Compared with hot-rolled steel, the material utilization rate is higher
Cold forming process reduces production costs
Long size reduces the number of on-site joints

Material Grades and Mechanical Properties:

ASTM A500 specifies different strength grades (primarily Grades B and C), allowing designers to select the most economical material based on their strength requirements. The mechanical properties of different grades are as follows:

Grade A: Yield strength ≥ 39 ksi (269 MPa), tensile strength ≥ 45 ksi (310 MPa)
Grade B: Yield strength ≥ 42 ksi (290 MPa), tensile strength ≥ 58 ksi (400 MPa)—This is the most commonly used grade, offering an excellent balance of strength and formability, suitable for most building structures. Grade C: Yield strength ≥ 50 ksi (345 MPa), tensile strength ≥ 62 ksi (427 MPa)—Higher strength, used in heavy-loaded structures and where weight reduction is required.
Grade D: Yield strength ≥ 36 ksi (250 MPa)—Mainly used for round tubes.

Approximate Comparisons:
The strength of A500 Gr. B is very close to that of the Chinese standard Q345 or the European standard S355.
The strength of A500 Gr. C is similar to that of the Chinese standard Q390.

Note: ASTM A500 focuses more on ensuring mechanical properties (minimum yield strength and tensile strength) rather than strict chemical composition control.

Common Specification Notation:

In North America, rectangular tube specifications are typically expressed in inches, using the format: long side outside dimension × short side outside dimension × wall thickness.

Common Abbreviations:
In engineering drawings and documents, it is often designated as HSS (Hollow Structural Sections), for example, HSS 6x4x1/4.

Common Size Range:
Long Side: From 2 inches to 20 inches or even larger.
Wall Thickness: From 0.125 inches to 0.5 inches or thicker.

Application of ASTM A500 rectangular tubes:

1. Building and steel structure
Building frame: used for beams, columns and supporting structures of high-rise buildings and industrial plants, providing excellent compression and bending resistance.
Roof truss system: suitable for large-span structures such as stadiums and airport terminals to ensure stability and load-bearing capacity.
Enclosure structure: as the supporting skeleton of curtain walls and roofs, it has both beauty and strength.

2. Bridges and infrastructure
Bridge structure: used for bridge main beams, guardrails, and supporting structures, with high seismic resistance and fatigue resistance.
Tunnel and subway engineering: as tunnel support and platform structure, adapt to complex geological conditions.

3. Machinery manufacturing and equipment
Engineering machinery: used for the frame of equipment such as cranes, excavators, conveyors, etc., providing high rigidity and wear resistance.
Automobile manufacturing: used for truck chassis and trailer structures, with both lightweight and high strength.
Agricultural machinery: such as tractor and harvester frames, adapt to high-load working environments.

4. Transportation
Railway vehicles: used for train carriages and rail sleeper support structures to improve durability.
Shipbuilding and marine engineering: used as ship hull reinforcement structure and offshore platform support, corrosion-resistant and impact-resistant.

5. Other industrial applications
Power and energy: used for transmission towers and solar brackets, adapting to harsh outdoor environments.
Furniture and decoration: high-end metal furniture and exhibition stand structures, both beautiful and load-bearing.

Purchasing and Usage Notes:

1. Specify the grade: Be sure to specify the desired grade (e.g., A500 Gr. B) on your order, as prices and performance vary significantly between grades.

How to Choose?
a. For most general building and structural applications, ASTM A500 Grade B is the default and most cost-effective choice.
b. When design loads are particularly high or when minimizing the structure's deadweight is necessary (e.g., high-rise buildings or long-span structures), consider ASTM A500 Grade C.

2. Alternative Standards: For projects requiring higher performance, tighter tolerances, and greater toughness, consider its upgraded version, ASTM A1085.

3. Surface Condition: Typically supplied uncoated (black steel), it may require subsequent anti-corrosion treatments such as painting or hot-dip galvanizing.
4. Connection Design: Joint design and welding should follow the design specifications of authoritative organizations such as the AISC (American Institute of Steel Construction).

In summary, when using rectangular tubing in North American or international projects, ASTM A500 Grade B is generally the default and safest and most reliable choice.

Read more: ASTM A500 Square Tube or Square tube vs Round tube: Which is better?