Development of High Strength Cast Steel for Semi-built up Type Crankshaft of Low Speed Diesel Engine, and Stress Measurement and Evaluation of Crankshaft

High strength cast steel, Throw Grade 5, has been developed for semi-built-up crankshafts to cover all current types of low speed diesel engines. Material test results with test pieces taken from a full-scale crankthrow are reported. Manufacturing approvals for this material have been taken from major classification societies. Prior to the application of this cast steel to an actual crankshaft, the crank pin fillet stresses at several points were measured in the workshop. The dynamic stress of each point, as analyzed with the finite element method, corresponds well with the measured data. Finally, application of this material to the crankshaft of an engine in a severe vibratory condition is introduced to show effective use of the material.