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Nodular Cast Iron Welding Process, Ductile Iron Welding


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 welded.

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 the weld.

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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