The
consumption of acetylene is about 75 litres per hour for each millimetre
of thickness in the sheet treated, and the normal consumption of oxygen
is 1.7 times as much; a joint 6 metres long can be burnt in 1 millimetre
plate per hour, and one of 1.5 metres in 10 millimetre plate. In certain
cases it is found economical to raise the metal to dull redness by other
means, say with a portable forge of the usual description, or with a
blowpipe consuming coal-gas and air. There are other forms of low-
pressure blowpipe besides the Fouche, in some of which the oxygen also is
supplied at low pressure. Apart from the use of cylinders of dissolved
acetylene, which are extremely convenient and practically indispensable
when the blowpipe has to be applied in confined spaces (as in repairing
propeller shafts on ships _in situ_), acetylene generators are now
made by several firms in a convenient transportable form for providing
the gas for use in welding or autogenous soldering. It is generally
supposed that the metal used as solder in soldering iron or steel by this
method must be iron containing only a trifling proportion of carbon (such
as Swedish iron), because the carbon of the acetylene carburises the
metal, which is heated in the oxy-acetylene flame, and would thereby make
ordinary steel too rich in carbon.
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