Kent Henry 
Former EASA Technical Support Specialist

In the power transmission indus­try, a fair amount of cast iron is used. Whether it’s for motors, pumps, or gear reducers, many use cast iron for the bulk of their structure. This variety of usage results in service opportunities involving the repair of cast iron components. 

Cast iron has a very high carbon content, so much so that the concen­trations of carbon form graphite flakes that result in a high resistance to wear. The drawback of cast iron is that the high carbon content also makes castings brittle. Examples of brittle castings are terminal boxes and fan covers. If a forklift operator rounded a corner a little wider than normal and bumped into the terminal box and fan cover of a Totally Enclosed Fan Cooled (TEFC) motor made from steel, the impact would bend the steel components. Steel is a fairly ductile material. The repair of these parts may Figure 1. Example of crack prepared for welding. and fully weld this side of the be limited to hammering out dents in the terminal box and fan cover. If the same collision happened with cast iron components, the damage would be quite different. They would likely be cracked or even break into pieces due to the brittleness.