Cutting Cast IronCast iron sometimes needs to be cut as preparation before being joined, built-up or repaired. Almost all cutting of cast iron is carried out using either oxygen cutting or plasma cutting, as these are usually the most freely available processes in the workshop. For some grades of cast iron powder cutting is used because of the carbon and alloying elements interfering with the exothermic reaction. The fuel gas is always acetylene and preheat is often necessary especially on thick sections. The most commonly encountered problems are cracking due to stresses set up by the local heating and formation of hard, brittle compounds in the HAZ of the cut. If the casting is porous some material may be ejected from the casting during cutting. Another process used for cutting up large cast iron items is thermic lancing. Although the process does not give the quality of cut needed to weld onto it is very useful for scrap cutting. Cutting is normally only carried out to put weld preparations in or to open up areas around fractures prior to repair. The main safety issues are flammable and compressed gases, hot metal, spatter, and, maybe, fume.
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