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General comment The starting format for manufacture of steel hollow profiles is mostly a coil of hot-rolled strip. The strip is de-coiled and after surface preparation, it is cut to an appropriate width, formed by bending to a round, square or rectangular shape and then welded longitudinally. The shaping operation can be performed either cold or on strip which has been heated. The procedure is carried out in a continuous line, the final operation being cutting to length. Hot-formed profiles have lower internal stresses than cold-formed which means that there is less risk for shape changes if they are cut, machined or welded. The principal advantages of cold-formed profiles are better dimensional tolerances and surface finish. Hollow profiles, especially those with square or rectangular section, are used as a complement to beam profiles in building construction and civil engineering. Compared with H- and I-beam profiles and U-channels, the closed shape of hollow profiles means that, for a given cross-sectional area, they have much better resistance to twisting. The steel grades used for cold- and hot-formed hollow profiles are most often weldable, low-carbon constructional steels with an iron content of 98% or more. As with other steel products, hollow profiles used in building and civil engineering constructions can at the end of their useful life be recovered and recycled to 100%. |
