Metal inert gas (MIG) welding is a type of welding in which a consumable wire electrode and shielding gas is fed continuously through a welding gun. Cast iron has a carbon content of at least two percent, which is more than steel. This makes it more brittle than most steels and consequently more difficult to weld. Cast iron also has a lower melting point, making it easier to manufacture when an electric furnace is not available. Most cast iron welding involves repairs to existing castings instead of forming new castings.
Instructions
1. Keep cast iron out of the 150 to 500 degree Fahrenheit range while welding, where it's at its most brittle stage. Use preheating if possible, but cooling can work also. Don't change methods in the middle of a weld.
2. Preheat the entire casting slowly and uniformly, if you're using preheating. The 500 to 1200 degree Fahrenheit range is best as cast iron usually begins to crack above 1400 degrees Fahrenheit. Use a low current to minimize the stress on the casting.
3. Keep the cast iron cool but not cold, if you're using cooling. The casting should never get too hot to touch with your bare hand. If the casting is part of some type of machinery, it may be possible to run the machine for a short time in to order to achieve the needed temperature.
4. Make short welds approximately 1 inch long in order to avoid overheating the casting. There will be small cracks when you MIG weld cast iron, even when you do it correctly. You will need to apply a sealing compound to joints that need to be water tight.
5. Use studding to repair major cracks in cast iron. Drill and tap holes in the surface to be welded and screw in the studs, so that they are five to six millimeters above the surface. Weld the studs into place.
Tags: cast iron, cast iron, Cast iron, degree Fahrenheit, degree Fahrenheit range
