This peculiarity is found to the greatest extent in copper,
aluminum and brass.
Should a hole be blown through the work, it may be closed by withdrawing
the flame for a few seconds and then commencing to build additional metal
around the edges, working all the way around and finally closing the small
opening left at the center with a drop or two from the welding rod.
WELDING VARIOUS METALS
Because of the varying melting points, rates of expansion and contraction,
and other peculiarities of different metals, it is necessary to give
detailed consideration to the most important ones.
_Characteristics of Metals._--The welder should thoroughly understand
the peculiarities of the various metals with which he has to deal. The
metals and their alloys are described under this heading in the first
chapter of this book and a tabulated list of the most important points
relating to each metal will be found at the end of the present chapter.
All this information should be noted by the operator of a welding
installation before commencing actual work.
Because of the nature of welding, the melting point of a metal is of great
importance. A metal melting at a low temperature should have more careful
treatment to avoid undesired flow than one which melts at a temperature
which is relatively high. When two dissimilar metals are to be joined, the
one which melts at the higher temperature must be acted upon by the flame
first and when it is in a molten condition the heat contained in it will in
many cases be sufficient to cause fusion of the lower melting metal and
allow them to unite without playing the flame on the lower metal to any
great extent.
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