Cast Iron Plate Preparation; Welding Cast Iron - Lincoln Electric AC-235 Manual

NOTE: The quenching of the roller (or idler) has another
purpose: It increases the hardness — and thus the service
life — of the deposit.
The hardfacing of the rails is a lot easier:
1. Place the rails with the side that rides on the rollers and
idlers upwards.
2. Use Jet-LH BU-90 electrodes. Same ampere setting as
on the idlers and rollers.
3. Build-up to size.
4. Do not quench. This will make the deposit slightly soft-
er than the deposit on the idlers and rollers. That means
that the wear will primarily be on the rails, which are a
lot easier and less time-consuming and cheaper to build-
up.
NOTE: The same electrode — BU-90 — will give the
operator two desired hardnesses, just by a difference in
cooling rate, making it possible to put the hardest deposit
on the most expensive parts.
NOTE: The outside of the rails (the side that comes in con-
tact with the ground) should be surfaced with Abrasoweld,
since this side has Metal to Ground wear.

Welding Cast Iron

When welding on a piece of cold cast iron, the tremendous
heat from the arc will be absorbed and distributed rapidly
into the cold mass. This heating and sudden cooling creates
WHITE, BRITTLE cast iron in the fusion zone.
This is the reason why welds in cast iron break. Actually,
one piece of the broken cast iron has the entire weld on it,
and the other piece has no weld on it.
In order to overcome this, the welding operator has two
choices:
1. He can preheat the entire casting to 500-1200°F. (260-
649°C). If the cast iron is hot before welding, there will
be no sudden chilling which creates brittle white cast
iron. The entire casting will cool slowly.
2. He can weld 1/2" (12.7mm) at a time, and not weld at that spot
again until the weld is completely cool to the touch.
In this way no large amount of heat is put into the mass.
Most inexperienced welders will probably use the second
method, because they have no way of preheating large cast-
ings. Smaller castings can easily (and should) be preheated
before welding. A forge, stove, a fire, or the Arc Torch are
all excellent means of preheating.
When using the 1/2" (12.7mm) at a time method, it is rec-
ommended to start 1/2" (12.7mm) away from the previous
bead and weld into the previous bead (backstepping).
After welding Cast Iron, protect the casting against fast
cooling. Put it in a sand (or lime) box.
If sand or lime is not available, cover it with sheet metal or
any other non-flammable material that will exclude drafts
and retain heat.

Cast Iron Plate Preparation

Wherever practical, the joint to be welded should be "veed"
out by grinding or filing to give complete penetration. This
is especially important on thick castings where maximum
strength is required. In some instances a back-up strip may
be used and plates may be gapped 1/8" (3.2mm) or more.
On sections where only a sealed joint is required and
strength is not important, the joint may be welded after
slightly veeing out the seam as shown.
Cutting
Do not exceed the Duty Cycle — See
page 8)
The arc welder and the electrode can be used for cutting
steel and cast iron. Follow this procedure:
1. Use 1/8:" (3.2mm) or 5/32" (4.0mm) Fleetweld 180 electrode.
2. Set welder on maximum (235 amps).
3. Hold long arc on edge of metal, melting it.
4. Push the arc through the molten metal, forcing it to fall
away.
5. Raise the electrode, and start over again.
The important thing is to continue this up-and-down, saw-
ing motion, melting the metal and pushing it away.
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