There are several ways to weld cast iron, two of the most common are Cold welding and Hot welding. Both of these processes require the use of an electrode designed specifically for cast iron. Other rods have been used with moderate success, to be 100% successful, use the rods designed for cast iron only. They are available at all welding supply stores. Both welds will require proper preperation of the piece. Grind it so you can weld from both sides and achieve full penetration. When welding cast iron it is beneficial to keep the welds short and do not weave very much, if at all. This applies to both cold and hot welding. Hot welding requires a preheat between 500 deg. F and 900 deg. F and maintenance of the interpass temp. of at least 500 deg. F. It also requires controlled slow cooling. A welding blanket or burying it in sand will help if you do not have an oven. Cold welding requires you to keep the temp. below about 200 deg. F, and to use only short, small welds. You must let the piece cool after each weld and never let the temp. go above 200 deg. F. You will need to jump around with your short, little welds as much as possible. There are no shortcuts to welding cast iron. Follow the procedure or you will have only moderate or no success. It is important to have a good means of monitoring the temperature as you go. Temp. sticks or a thermometer of some sort is essential.