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Mechanical & Structural Tubes

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Mechanical Structural Tube

Structural Hollow Sections (SHS) are very effective in resisting buckling loads, resulting in a high strength-to-mass ration. High flexural stiffness in all directions is combined with high torsional stiffness.

When used as beams, the need for lateral support is reduced. Columns and beams do not need to be checked for torsional-flexural buckling if they fall within the limits of the slenderness ratio or when the height-to-breadth ratio of these sections does not exceed 2 to 1.

The result is less material usage and a competitive engineering solution. The lighter, yet stiffer structural members simplify the erection as longer spans can be pre-fabricated. Connecting members are typically joined by welding under strict factory conditions.

Structatube 355

Material specification

Grade 355 Tubes, also commonly known as Structural Hollow Sections, was launched in February. Previously Grade 300 Tube, launched in June 1997, was available. Engineers can now use an increase minimum yield stress of 355MPa yield and an Ultimate yield tensile stress of 450MPa for designs.
Grade 355 Tube will enhance the benefits of Structural Hollow Sections and then will allow Tubes to compete on an equal footing with other steel sections.  Furthermore it will assist Tubular steel in competing with other construction materials.

Chemical Composition – Maximum

  • Carbon Equivalent – 0.39
  • Carbon – 0.22
  • Mn – 1.6
  • Si – 0.25

Mechanical Properties – Minimum

  • Yield Strength – 355MPa
  • UTS – 460MPa
  • Elongation – 20%

Standard Lengths

Structural and Mechanical tube is stocked in standard lengths of 6 metres, exceptions are:

  • 193.7mm round in thicknesses of 3.5 and 6.0 mm where the stocked lengths are 6.1.
  • 219mm round in a thickness 3.5 mm where the stocked length is 6.1 metres.
  • 219mm round in thicknesses of 4.5 and 6.0mm where the stocked lengths are 6.1 and 9.144 metres.
  • Selected sizes in the structural tube range are available in 9.144 metre lengths.

Other lengths may be supplied on request, but are subject to minimum order quantities.

Dimensions – Mechanical and Structural Rounds

Nominal diameter in mm Outside diameter in mm
Maximum Minumum
21 21.70 20.90
25 25.50 24.70
27 27.3 26.50
32 32.20 31.40
34 34.10 33.30
38 38.40 37.60
42 42.80 42.00
48 48.70 47.90
51 51.40 50.60
57 57.40 56.60
60 60.70 59.90
63 63.90 63.10
76 76.50 45.50
89 89.30 88.50
95 95.40 94.60
102 102.00 101.20
114 114.90 113.70
127 127.60 126.70
140 140.20 139.10
152 153.00 151.80
165 165.70 164.50
178 178.40 177.20
193 194.30 193.10
219 219.50 218.50

Wall thickness

The wall thickness of the tubes shall be in the range of 1.2 – 6.0mm as required. the tolerance on wall thickness shall comply with that of the steel manufacturer and is typically as follows:

Thickness in mm Tolerance in mm
1.5 to 2.0 ± 0.15
>2.0 to 2.5 ± 0.18
>2.5 to 4.0 ± 0.20
>4.0 to 6.0 ± 0.28

Squareness

The angle at each corner of a tube must measure 90o + 1o.

Outside Corner Radius

The outside corner radius of each corner must not exceed 2.5 times the wall thickness.

Twist

The twist of a square or rectangular section must not exceed 2mm plus 0.5mm per metre length of tube i.e. the maximum twist in a 6.0m length may be 1mm + 6mm = 18mm.

Concavity / Convexity

The concavity / convexity must not exceed 0.8% of the outside dimension H (Height) or B (Breadth), with a minimum of 0,5mm.

Straightness

The straightness tolerance for mechanical and structural round tubing is 2mm/metre length.

Colour Coding

At least one face of round, square and rectangular tubes shall be colour coded as per the table below:

Wall Thickness (mm) Colour Code
1.6 Red
2.0 Green
2.5 White
2.8 Pink
3.0 Yellow
3.5 Blue
4.0 Purple
4.5 Khaki Brown (Sahara)
5.0 Dark Brown
5.5 Orange
6.0 Grey

Mechanical and Structural Tube Range – Rounds

Mechanical and Structural Tube Range – Squares

Mechanical and Structural Tube Range – Rectangles