Coupled electromagnetic and thermal analysis of induction heating for the forging of marine crankshafts

The induction heating of heavy marine crankshaft preforms has been analyzed to evaluate the temperature distribution prior to forging. The preform has a cylinder shape with a ring groove region and is heated in sections by induction. Each section is then forged to produce a crankshaft pin journal and a web region with continuous grain flow using vertical and horizontal compressions. Since induction heating of the preform needs precise temperature control to prevent process-induced defects such as overheating or insufficient heating, an equivalent circuit model was adopted in conjunction with a coupled electro-magnetic and thermal analysis to evaluate the coil current induced in preforms with various dimensions, power levels, and frequencies. The magnetic permeability, which depends on temperature and magnetic field, was evaluated in an iterative manner and also considered in the analysis. The temperature distribution of the preform was numerically predicted and compared with experimental values. The experimental validation confirms that the suggested analysis method can be a practical tool to predict the temperature distribution in the induction heating for the forging of heavy marine crankshafts.