BRASS WELDING
(=112=) It is difficult for the beginner to accustom himself to brass
welding, especially on large work. While he has been taught to believe
that brass has a much lower melting-point than iron or steel, yet when
he comes face to face with the actual problem of melting it, he will
find that it is necessary to hold his flame in contact with his piece
much longer, on brass work than on either of the other two, before
the melting point is reached. This can be accounted for by the great
conductivity of brass. On cast iron and steel the heat was rather
local, but on brass work it is transmitted to all parts of the piece as
rapidly as it is introduced, and this absorbing process continues until
practically the entire piece is near the melting point.
(=113=) Brass has for its base, copper to which an alloy of zinc has
been added. Now the most difficult part of fusing brass work, is to
add more metal from the filler-rod to the parts which are to be fused,
without burning up any more of the alloy, than is absolutely necessary.
Seeing that the copper and zinc have different melting points, it is a
very difficult feat and requires considerable practice. Much of this
trouble can be eliminated by the use of a filler-rod which has the
correct proportion of alloy added, so that it may take care of and
replace any that has been destroyed by the flame.
(=114=) Brass work is “V-ed” out when welding is to be done, in
practically the same way as cast iron. Only under no circumstances
should the ends of the parts be burned off, when “V-ing,” as the heavy
oxide which is deposited on the remaining metal is very hard to combat
with the welding flame. The ends of the work are brought to a red heat
with the flame that is slightly carbonizing. This is held directly in
contact with the work during the preheating stages, in much the same
manner as on cast iron, and a small layer of carbon may be seen to
accumulate around the weld. Now, in theory, this would seem the worst
thing possible to have present, but in practice a small quantity of
this soot acts as an aid in making the weld, besides making the flame
less intense, which saves much of the alloy, from being burned when the
fusion occurs. When the ends have become red hot, the same procedure
is used as in working steel, except that the torch is given a slightly
greater angle and a brass flux is used.
(=115=) Contrary to most authorities we find that an abundance of good
flux is desirable on brass work and that it is almost impossible to
use too much. It is desirable to use only the best welding fluxes, for
the best welds are to be insured only under ideal conditions. If a
welder were to run short of flux, however, he might use powdered borax
of the 20 Mule Team variety, to tide him over until he could get a
new supply. The flux is added in the same way as the cast-iron flux,
that is, by dipping the heated end of the filler-rod into the flux
container. Enough will adhere, and when added will clear up the metal
in the vicinity of the weld. It should be added as often as a welder
notices his metal needs cleaning and this will vary depending upon
whether there is a slow or rapid worker behind the torch. A man must
use his own judgment in cases of this kind. Remember that the flux is
a cleaning agent and if the surface is clean, no additional flux is
necessary, but if the contrary is true, that is, if the surface is full
of oxide and the filler refuses to flow easily, flux is necessary and
should be added.
(=116=) During the welding, dense white fumes will come from the fusing
brass. This is the burning out of the alloy, that is, the zinc. These
fumes are injurious to the welder and should be avoided, if possible,
by proper ventilation. The use of a proper filler-rod and rapid work
will largely tend to overcome the presence of these fumes, but if the
operator is very slow, they will appear, and are followed by a porous
and brittle weld, which if broken afterwards will show a large number
of blow holes. The most difficult part of brass welding as a whole is
to add the filler-rod, being certain of a fusion, without burning out
the zinc. When brass is in a heated condition, it is very fragile and
will crack readily if disturbed. All precautions should be taken to see
that no sudden jarring is given the piece until the weld has completely
set. When this work is done many welders plunge their work in water, in
an effort to make it more ductile and easier to machine. While this,
of course, is condemned by theorists and rightly so, in practice there
seems to be no injury results.