Figure 6-19.Braze welding cast iron, using the backhand method.
an example of tinning being used with the backhand
method of welding.
Temperature control is very important. If the base
metal is too hot, the filler metal bubbles or runs around
like beads of water on a hot pan. If the filler metal forms
little balls and runs off the metal, then the base metal is
After the base metal is tinned, you can start adding
beads of filler metal to the joint. Use a slight circular
motion with the torch and run the beads as you would
in regular fusion welding. As you progress, keep adding
flux to the weld. If the weld requires several passes, be
sure that each layer is fused into the previous one.
After you have completed the braze welding opera-
tion, heat the area around the joint on both sides for
several inches. This ensures an even rate of cooling.
When the joint is cold, remove any excess flux or any
other particles with a stiff wire brush or steel wool.
WEARFACING is the process you use to apply an
overlay of special ferrous or nonferrous alloy to the
surface of new or old parts. The purpose is to increase
their resistance to abrasion, impact, corrosion, erosion,
or to obtain other properties. Also, wearfacing also can
be used to build up undersized parts. It is often called
hard-surfacing, resurfacing, surfacing, or hardfacing.
As a Steelworker, there are times when you are
required to build up and wear-face metal parts from
various types of construction equipment. These parts
include the cutting edges of scraper or dozer blades,
sprocket gears, and shovel or clamshell teeth. You may
even wear-face new blades or shovel teeth before they
are put into service for the first time. There are several
different methods of wearfacing; however, in this dis-
cussion we only cover the oxygas process of wearfacing.
Wearfacing provides a means of maintaining sharp
cutting edges and can reduce wear between metal parts.
It is an excellent means for reducing maintenance costs
and downtime. These and other advantages of wearfac-
ing add up to increased service life and high efficiency
Wearfacing with the oxygas flame is, in many re-
spects, similar to braze welding. The wearfacing metals
generally consist of high-carbon filler rods, such as high
chromium or a Cr-Co-W alloy, but, in some instances,
special surfacing alloys are required. In either event,
wearfacing is a process in which a layer of metal of one
composition is bonded to the surface of a metal of
The process of hard-surfacing is suitable to all low-
carbon alloy and stainless steels as well as Monel and
cast iron. It is not intended for aluminum, copper, brass,
or bronze, as the melting point of these materials pro-
hibits the use of the hard-surfacing process. It is possible
to increase the hardness of aluminum by applying a
zinc-aluminum solder to the surface. Copper, brass, and
bronze can be improved in their wear ability by the
overlay of work-hardening bronze. Carbon and alloy
tool steels can be surface-hardened, but they offer diffi-
culties due to the frequent development of shrinkage and
strain cracks. If you do surface these materials, they
should be in an annealed, and not a hardened condition.
When necessary, heat treating and hardening can be
accomplished after the surfacing operation. Quench the
part in oil, not water.