There are many different metals used in welding, however, we are going to be focusing on cast iron and its many uses. Cast iron is a very versatile metal that is used in thousands of products today. Its popularity rises from the strength that it offers and that it is an inexpensive metal to use.
Cast iron is an iron carbon alloy which comes in many different grades. Although some welders prefer other metals because some of the different grades of cast iron are known to be brittle; not all cast iron is brittle and not all cast iron can be welded.
There are many different grades of cast iron. The most common form of cast iron is Gray Iron, which comes in many different forms depending on the strength that is required. Gray irons are known for their high compressive strength.
Malleable iron is another type, it is close to gray iron in chemical composition, but it has different properties that make it closer to steel. Malleable iron cannot be fusion welded with the same results as gray iron. That is why it is recommended that malleable iron be braze welded. It is more successful using it in that manner.
Next we have Nodular iron, which has many of the same properties of malleable iron; thereby it is not recommended that you use fusion welding. Fusion welding weakens its original properties. A braze weld is recommended as long as the loss of some tensile strength can be tolerated.
With the different grades of cast iron there is bound to be one that will work for your particular situation as long as you keep in mind that not all of them can be welded in the same manner. Be sure to do your research and choose your cast iron wisely.