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How to Weld MIG Cast

Cast iron is used in industry due to its low melting point, fluidity and simplicity of manufacture. Cast iron can be machined easier and at higher speeds than steel, meaning that it can be readily and easily manufactured into useful machinery. However, on account of its brittleness, cast iron is particularly difficult, and often called "impossible," to MIG weld. Therefore, most welding of cast iron is done for repair purposes, rather than for formative purposes.

MIG welder
Electric oven
Sealing compound
Drill
Studs

Instructions

- 1
  Preheat your cast metal, within its optimal temperatures, to minimize stress during welding. In the case of iron, you should preheat it between 500 and 1,200 degrees Fahrenheit. Keeping it between 150 and 500 degrees Fahrenheit causes brittleness, whereas iron will crack above 1,400 degrees Fahrenheit.
- 2
  Use the MIG welder to make small welds, about 1 inch long, in the cast metal. MIG welding results in small cracks in certain kinds of cast metal--particularly iron--so apply a sealing compound to any joints that need to be watertight.
- 3
  Drill holes into any particularly large cracks. Screw in studs, 5 to 5 mm above the surface, and weld the studs in place.

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