Square and rectangular steel tubes, also known as hollow structural sections (HSS) or square hollow sections (SHS)/rectangular hollow sections (RHS), are widely used in the construction, engineering, and manufacturing industries. Their unique shape, strength, and versatility make them a preferred choice for various structural and architectural applications.

In this article, we’ll explore the classification, surface treatments, applications, and specifications of square and rectangular steel tubes, especially focusing on galvanised options.

 

1. What is a Rectangular or Square Steel Tube?

Rectangular and square steel tubes are hollow steel profiles with a rectangular or square cross-section. They are manufactured by rolling steel into shape and welding the seams.

These hollow sections offer high strength-to-weight ratios and aesthetic simplicity, making them ideal for load-bearing and visual applications.

 

2. Classification of Square and Rectangular Tubes

Depending on the manufacturing process and surface treatment, square and rectangular tubes can be classified into:

a. Hot Rolled Rectangular Tubes

• Made from hot-rolled steel

• Rougher surface finish

• Lower cost, suitable for heavy-duty structural uses

b. Cold Rolled Rectangular Tubes

• Better surface finish and dimensional tolerance

• Ideal for precision parts or visible applications

c. Pre-Galvanised Rectangular Tubes

• Zinc coating applied to the coil before forming

• Uniform surface and good corrosion resistance

d. Hot-Dip Galvanised Square Tubes

• Dipped in molten zinc after forming

• Thick zinc layer (up to 275g/m²)

• Best for outdoor or marine environments

 

3. Surface Treatment Options

Surface Type	Description	Application
Black (as-welded)	Untreated surface	Internal structures, welding bases
Pre-Galvanised (GI)	Zinc-coated before forming	Fencing, frames, and shelves
Hot-Dip Galvanized	Immersed in molten zinc	Bridges, guardrails, greenhouses
Powder Coated / Painted	Colored coating for aesthetics	Furniture, display stands
Oiled	Light oil layer to prevent temporary rust	Short-term indoor storage

 

4. Applications of Square and Rectangular Steel Tubes

Thanks to their versatility, square and rectangular steel tubes are used in:

• Construction

  • Steel structure frameworks

  • Purlins and columns

  • Roof trusses and wall systems

• Automotive and Machinery

  • Chassis components

  • Equipment frames

• Furniture

  • Table and chair frames

  • Storage racks

• Agricultural and Greenhouse Structures

  • Shelters and fencing

  • Plant supports

• Solar Mounting Systems

  • Rectangular galvanised tubes offer anti-corrosion and durability in outdoor setups

 

5. Common Specifications and Sizes

The dimensions of square and rectangular tubes are usually defined by:

• Outer Dimensions (OD): width × height (e.g. 50×50 mm, 40×60 mm)

• Wall Thickness: 1.2 mm – 10 mm

• Length: 5.8m, 6m, 11.8m, or custom cut

Example Sizes (Metric):

Type	Size (mm)	Thickness (mm)	Length (m)
Square	25×25	1.5 – 3.0	6
Square	50×50	2.0 – 5.0	6/12
Rectangular	40×60	1.5 – 6.0	6/11.8
Rectangular	100×200	3.0 – 10.0	Custom

 

Material Grades:

• Q195 / Q235 / Q345

• ASTM A500 Grade B / C

• EN 10219 S235 / S355

 

6. Quality and Certifications

 

At HHY Steel Group, we provide full quality assurance through:

• Mill Test Certificates (MTC)

• CE / ISO / EN / ASTM Certifications

• Zinc Coating and Dimensional Accuracy Reports

• Welding Strength Verification

We manufacture all rectangular and square steel tubes according to international standards and offer third-party inspection upon request.

 

7. Why Choose Galvanised Rectangular Tubes from HHY Steel Group?

 

• ✅ Advanced Forming and Galvanising Equipment

• ✅ Own Galvanising Lines for Uniform Zinc Coating

• ✅ ODM/OEM Services with Fast Delivery

• ✅ Technical Team Supporting Project Design and Optimisation

• ✅ Global Export Capability with Professional Logistics

 

8. Contact HHY Steel Group for Your Steel Tube Needs

Looking for high-quality square and rectangular steel tubes for your next project?

HHY Steel Group offers a wide range of hot-rolled, cold-rolled, and hot-dip galvanized hollow sections tailored to your structural and commercial needs.

📧 Email: info@hhysteelstructure.com

🌐 Website: www.hhysteelstructure.com