Nodular cast iron, also called ductile iron, is a special type
of cast iron that has inclusions of carbon within its structure
in order to increase the strength of the metal while at the same
time retaining the ductility inherent in typical cast iron.
Unfortunately, this produces some problems when attempting to
weld the material. Like standard cast iron, nodular cast iron
can be welded, but the strength inherent in the metal where it
is welded is lost because you cannot impregnate carbon into the
fusion welding process. That makes welding nodular cast iron
only good for non-load-bearing welds or welds in which it
doesn't matter that the strength of the weld is less than the
material being welded.
1. Clamp the nodular cast iron parts together in the way they
are to be welded. This will leave your hands free to manipulate
the direction of the welding gun or to steady your welding hand.
2. Turn on the welder and set it for the power and wire feed
speed necessary for the width of the cast iron being welded.
This information can usually be found on the inside panel of the
welder or in the welder's owner's manual.
3. Attach the negative ground clamp to the nodular cast iron
work piece, then lower your welding helmet.
4. Position the welding electrode at the end of the welding gun
approximately 1/4 inch from the seam between the two parts being
5. Pull the trigger of the welder. As the electrode strikes the
nodular cast iron parts, you will notice the formation of a pool
of molten metal. Using tiny circles, build up this weld pool
until it is approximately 1/4 inch across, then begin to move
the pool across the seam between the metal while you continue to
work the electrode in small circles. In this fashion, complete
6. Turn off the welder and inspect the part. The weld bead
should be no more than 1/8 inch above the welded parts and no
wider than 1/4 inch. This type of weld will produce sufficient
strength to hold the two parts together.
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