Square Tube Sections: Mass of 1 m and Section Properties

Square tubes: GOST 8639-82 and HSS to EN 10219

The square tubes are given in two ranges. The first, GOST 8639-82, covers sizes from 20×20 to 200×200 mm. The second, EN 10219:1997, describes HSS (hollow structural sections); the table runs from 60×60 to 200×200 mm.

The designation 40×40×3 means a 40 mm side and a 3 mm wall. The European range writes the same as 40X40X3 and puts the letters HSS in front.

Square steel tubes · ГОСТ 8639-82

b is the side of the square, s the wall thickness (t in HSS), r1 the outer corner radius, in mm. A is the section area; J, W, i are the moment of inertia, section modulus and radius of gyration (the same about both axes).

Square hollow sections (HSS) · EN 10219:1997

b is the side of the square, t the wall thickness, r1 and r2 the outer and inner corner radii, in mm. A is the section area; J, W, i are the moment of inertia, section modulus and radius of gyration about any axis through the centre.

Why J and W are single figures

A square is symmetrical, so the moment of inertia Jy equals Jz and the section modulus Wy equals Wz. That is why the tables have one column each for J, W and i instead of two.

Equal stiffness in both directions is the main difference from a rectangular tube. Square tube suits posts, columns and frames where the load can act from different sides. For purlins and beams loaded in one plane, a rectangular tube is often the better choice.

Corner radii and the mass of one size

The corners of a hollow section are rounded. In the GOST 8639-82 table the outer radius r1 is twice the wall thickness: 4 mm for s = 2 mm and 8 mm for s = 4 mm. In the HSS table the 80X80X4 tube has a 6 mm outer and a 4 mm inner radius.

Because the radii differ, the section area differs slightly between the ranges, and so does the mass. An 80×80×4 tube to GOST weighs 9.22 kg/m, while 80X80X4 to EN 10219 weighs 9.41 kg/m. For 100×100×4 it is 11.73 and 11.9 kg/m, for 120×120×4 14.25 and 14.4 kg/m.

The gap is small, but a specification should name the standard the mass was calculated by.

How to get the mass of a tube from the table

The mass is the mass per metre times the length. An 80×80×4 tube is 9.22 kg/m, so a six-metre length weighs 55.3 kg, and a tonne holds 108.5 m. For 40×40×3 (3.3 kg/m) a tonne holds 303 m.

The “Metres per tonne” column helps when metal is bought by weight: divide the length you need by this figure to get the mass in tonnes.

Where square tubes are used

Square tube is chosen where equal stiffness in two directions and flat faces for welding and fixing are needed: posts, columns, frames, fences and support frames. For outdoor products it can be galvanized: hot-dip galvanizing protects both the outer surfaces and the inner cavity.

Calculator and ordering

How much a batch of square tubes weighs is shown by the rolled metal calculator. Other profiles are in the rolled metal handbook. Tubes in a frame need welding to a drawing, so send a drawing or a specification. The POLYGONAL company makes steel structures to the customer’s drawings, prepares KM and KMD drawings and galvanizes the products.