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Machining Different Types of Cast Iron

Across a wide range of industries Cast Parts are used as a process to create a wide range of components. Cast iron is one of the most free-machining ferrous materials meaning that a good surface finish can be achieved without using a lot of time/power/cutting force during the machining process. This is not to say it is without its challenges as different types of cast iron have their own machining properties.

Ductile Iron: As its name suggests Ductile Iron is easy to machine, but due to a higher ferrite content will build up around the cutting tool during machining. Certain grades of Ductile Iron like Grade GGG60 will wear cutting tools due to their pearlite content. Ductile Iron is popularly used in the automotive industry for components such as crankshafts and camshafts.

Austempered Ductile Iron: Austempered Ductile Iron is created through the addition of alloys to Ductile Iron and then performing a heat treatment. These alloys include Molydenum, Copper and Nickel. This process increases the metal’s ductility to 12-22% as well as producing a stronger and tougher material. As such Austempered Ductile Iron will take longer to machine and is also linked to rapid tool wear in the same manner as Ductile Iron.

Grey Iron: Grey Iron offers excellent machinability making it one of the most used Cast Iron materials. It provides excellent wear resistance as well as dampening abilities. It’s popular with a wide range of components but most noticeably engine blocks, brake discs and housings for automotive parts.

Compacted Graphite Iron: Compacted Graphite Iron has a similar makeup to Grey Iron, only with a slightly higher thermal conductivity and damping abilities. It offers similar machinability to Grey Iron and is growing in popularity where components have to perform at higher temperatures.

White Iron: White Iron is the most difficult to machine of the cast Irons, and as such will take longer to machine and will result in higher tool wear rates. As a material it does offer extreme resistance to factors such as abrasive wear, high temperatures and corrosion resistance, and is a non-magnetic metal. This makes it suitable for oil and gas components that often need to perform in taxing environments.

Every type and grade of Cast Iron is unique, and machining of this material is not so straight forward to those unfamiliar with it. As a sub-contract machinist, Bronte Precision are used to working with a very wide range of metals and have experienced staff who understand how to best run our machines in order to manufacture components to your spec. We specialise in complex machining where parts have intricate geometries require multiple bores, tapping and multiple processes. We are based in Bradford and fully ISO certified. Contact us today about the machining of your cast parts.