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There are several methods of preheating; the choice will depend on many factors, including the size and shape of
the part, cost of fuel, and the need for slowest possible cooling after welding has been completed. Many types of
preheating torches are available which burn relatively inexpensive fuels such as kerosene or natural gas. They can
be used for local preheating on large castings, or for general heating of smaller pieces under a hood such as
illustrated in Fig. 12-7. It is not too difficult to build a temporary preheating furnace of firebrick, as shown in Fig 12-
8. Such a furnace is best heated with charcoal. If the casting is properly positioned in the furnace, welding can be
done without removing it from the furnace, and it can be allowed to cool slowly, under an asbestos paper cover,
after welding.
Fig. 12-8. How to construct a temporary preheating furnace out of loose fire brick and asbestos paper.
Floor Bricks
Draft Holes
Angle Iron Supports
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Holes Punched
in Asbestos
Paper
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