Cold-formed Circular Hollow Sections
to spec BS EN10219: 2006 S235JRH
Od – Outside diameter
Wt – Wall thickness
Kg/m – Kilos per linear metre
L – Standard bar length
Contact Harris Steels if you would like to request a price, place an order, or have any further questions about our Cold-formed Circular Hollow Section steel stock range.
About this product
Cold formed circular hollow section (CHS) is formed from hot rolled coil and has a smooth blue/grey coloured finish and a raised internal weld seam that can vary greatly depending on the mill of manufacture. Coils vary in size up to around 25 tonnes and 2 metres wide. Coil is first decoiled through slitting knives and re-coiled for storage until the mill rolling program requires the size. Multiple widths are slit from one coil to minimise scrap.
For the coil to become hollow section the slit coil is decoiled through a long series of mating rolls which gradually bring the two edges together to form the desired dimensions. An inline electric resistance welder seals the two edges together and the weld seam is then removed back to the outside wall of the section. Internal weld seams can be removed from the section with extra processing at the point of manufacture, this is not common practice however due to the end use of the general product.
Due to the nature of the cold forming process, stresses can build up in the material which are controlled by the corner radius. Ordinarily the rolling stress will never become apparent through normal working (sawing, drilling, welding, bending etc). Hot dip galvanising of cold formed products can release some material stresses due to the relatively high melting point of zinc (420°c) even though stress relieving of steel is generally carried out between 550°c and 650°c.
To overcome material stress from cold working/rolling material, hot finished hollow sections are available to a different standard. Hot finished hollow sections are first cold rolled to a circular profile as above but are then heated to the steels normalising temperature of around 900°c+, the tubes are then passed through forming rolls individually and air cooled to further relieve material stresses. For this reason hot finished hollow sections are more expensive by comparison to the same sizes in cold formed. Hot finished hollow sections are typically characterised by having a smaller radius and thicker wall to section ratio than cold formed hollow sections.
Section tolerances differ but are typically +/- 10% with a minimum of 0.5 mm. Cold formed hollow sections are strong and light weight and are used by a huge range of sectors and businesses from large scale construction companies building national stadiums, to companies manufacturing frames or washing lines. Most of the hollow section sold throughout the UK is imported from Turkey in 7.5 metre length, sections rolled in Europe are 6 or 12 metre lengths however 10 metre lengths and longer are sometimes available. We try to source material rolled in the UK wherever possible, unfortunately this is not always possible with hollow sections due to the limited number of existing hollow section mills in the UK.
21.3 x 3 up to 168.3 x 5 mm