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Steel Designers' Manual - 6th Edition (2003)
Fig. 32.5 Hand flame cutting
hand flame
cut edge pre—drilled
hole
incorrect correct
Cutting 959
characteristics. Notching or coping of beam ends can now be carried out by computer-controlled
machines which burn the webs first and create the radiused corner
then cut the flanges with a cut which coincides with the web cut. Numerically
controlled coping machines can cut top and bottom notches simultaneously, and
the notches can be of different dimensions.
Castellated beams were traditionally formed by cutting a multi-linear, castellated
pattern along a UB or UC section followed by realignment and rewelding. The web
cutting is always machine controlled to ensure accurate fit-up and an edge which is
suitable for subsequent welding.
More recently, a two-cut process has been developed that creates beams with circular
openings, frequently called Cellform beams. These beams have proved to be
very popular both for long span roof structures where the steelwork is exposed and
as primary and secondary beams in composite floors. In the latter case, further
economy may be achieved by cutting the top tee sections from a lighter rolling than
the bottom.
Arc plasma cutting
Plates may be cut by arc plasma techniques. In this case the cutting energy is produced
electrically by heating a gas in an electric arc produced between the tungsten
electrode and the workpiece which ionizes the gas, enabling it to conduct an electric
current.The high-velocity plasma jet melts the metal of the workpiece and blows
it away. The cut so produced is very clean, and its quality can be improved by using
a water injection arc plasma torch. Plasma cutting can be used on thicknesses up to
about 150 mm but the process is then substantially reduced in speed.
Shearing and cropping
Sections can be cut to length or width by cropping or shearing using hydraulic
shears. Heavy sections or long plates can be shaped and cut to length by specialist
plate shears. These are large and very expensive machines normally to be found in