Ductile Iron Good as Steel

A study jointly conducted by Simpson Industries Inc., Ricardo Inc. and Intermet Corp. reveals that a crankshaft manufactured from cast ductile iron installed in an aluminum V-6 engine displays characteristics on par with one made of forged steel. The trend has been to move away from iron because of a perception that steel produces less torsional and bending vibrations than iron, resulting in reduced noise, vibration and harshness (NVH). The study shows that engine designers often overlook the fact that ductile iron, with its lower weight, has less rotating mass than an equivalent crank made from steel. Less rotating mass naturally produces fewer torsional vibrations, the study points out. Also, the use of vibration dampers do a good job of absorbing the energy produced by both torsional and bending vibrations. Another benefit of using a ductile iron crankshaft is the reduced cost of manufacture due to lower material, production and machining costs, the study says.