What a Square Hollow Section Is
A square hollow section (SHS) is a cold-formed or hot-finished welded tube with a square cross-section. Because the material is distributed around the perimeter, an SHS resists bending, torsion and compression efficiently in all directions, which makes it ideal for columns, frames and members that can be loaded from any direction.
Manufacture and Standard
Q235 square tubes are formed from strip steel and welded by high-frequency resistance welding or submerged arc welding, then sized and straightened. Cold-formed sections are produced to GB/T 6728, and the grade Q235 follows GB/T 700-2006 with a minimum yield of 235 MPa and tensile range of 370-500 MPa. The weld seam is tested and the section is verified for dimensional accuracy.
Size Range
Square hollow sections are available from 20 x 20 mm to 400 x 400 mm, with wall thicknesses from about 1.0 mm to 16 mm. Standard lengths are 6 m and 12 m, and the sections can be supplied black, oiled or hot-dip galvanized.
Fabrication
SHS members are cut, drilled, mitred and welded with standard practice. The closed section makes corner joints and end plates simple to detail, and connections to other members are made by welding or by bolting through the walls. Cutting with a saw or abrasive wheel gives a clean, square end for assembly.
Applications in Durable Structures
Columns and posts for buildings, canopies and pergolas
Frames for gates, fences and barriers
Handrails and guardrails
Trailers, chassis and equipment frames
Solar, sign and lighting support structures
Corrosion Protection
For outdoor service, hot-dip galvanizing to BS EN ISO 1461 protects the tube, its cut ends and welds for decades. Painted systems are used indoors or where a specific colour is required, and the smooth square face takes coatings cleanly.
Frequently Asked Questions
Q: What is the difference between SHS and RHS?
SHS is a square hollow section with equal sides, while RHS is a rectangular hollow section with unequal sides. Both are produced as welded tube.
Q: What sizes are available?
Square tubes range from 20 x 20 mm to 400 x 400 mm with wall thicknesses from about 1.0 mm to 16 mm, in 6 m and 12 m lengths.
Q: Is the weld seam visible?
The longitudinal weld seam is normally smooth and may be visible as a slight line; the tube is sized after welding for a uniform section.
Q: Can square tube be galvanized?
Yes, hot-dip galvanizing to BS EN ISO 1461 is recommended for outdoor and wet service, including the interior where accessible.
Q: What is Q235 square tube used for?
Columns, frames, gates, handrails, trailers and support structures where durability and clean appearance are required.
Q: Are mill certificates supplied?
Yes, certificates record the grade, chemistry, mechanical properties and weld test results for traceability.