After welding, the work should be slowly cooled by
covering with ashes, slaked lime, asbestos fibre or some other
non-conductor of heat. These precautions are absolutely essential in the
case of cast iron.
A neutral flame, from a nozzle proportioned to the thickness of the work,
should be held with the point of the blue-white cone about one-eighth inch
from the surface of the iron.
A cast iron rod of correct diameter, usually made with an excess of
silicon, is used by keeping its end in contact with the molten metal and
flowing it into the puddle formed at the point of fusion. Metal should be
added so that the weld stands about one-eighth inch above the surrounding
surface of the work.
Various forms of flux may be used and they are applied by dipping the end
of the welding rod into the powder at intervals. These powders may contain
borax or salt, and to prevent a hard, brittle weld, graphite or
ferro-silicon may be added. Flux should be added only after the iron is
molten and as little as possible should be used. No flux should be used
just before completion of the work.
The welding flame should be played on the work around the crack and
gradually brought to bear on the work. The bottom of the bevel should be
joined first and it will be noted that the cast iron tends to run toward
the flame, but does not stick together easily. A hard and porous weld
should be carefully guarded against, as described above, and upon
completion of the work the welded surface should be scraped with a file,
while still red hot, in order to remove the surface scale.
Pages:
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127