The heat conductivity bears a very important relation to welding, inasmuch
as a metal with a high rate of conductance requires more protection from
cooling air currents and heat radiation than one not having this quality to
such a marked extent. A metal which conducts heat rapidly will require a
larger volume of flame, a larger nozzle, than otherwise, this being
necessary to supply the additional heat taken away from the welding point
by this conductance.
The relative rates of expansion of the various metals under heat should be
understood in order that parts made from such material may have proper
preparation to compensate for this expansion and contraction. Parts made
from metals having widely varying rates of expansion must have special
treatment to allow for this quality, otherwise breakage is sure to occur.
_Cast Iron._--All spoiled metal should he cut away and if the work is
more than one-eighth inch in thickness the sides of the crack should be
beveled to a 45 degree angle, leaving a number of points touching at the
bottom of the bevel so that the work may be joined in its original
relation.
The entire piece should be preheated in a bricked-up oven or with charcoal
placed on the forge, when size does not warrant building a temporary oven.
The entire piece should be slowly heated and the portion immediately
surrounding the weld should be brought to a dull red. Care should be used
that the heat does not warp the metal through application to one part more
than the others.
Pages:
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126