Predicting hardness profile of steel specimens subjected to Jominy test using an artificial neural network and electromagnetic nondestructive techniques

Based on relationships between electromagnetic properties and microstructural changes in steel, the current paper describes the development of an electromagnetic technique to determine steel hardenability, non-destructively. Performing Jominy end-quench test, magnetic hysteresis loop and eddy current methods have been applied to SAE 4140 standard steel samples to explore applicability of the non-destructive techniques for determining hardenability. Different hysteresis loop parameters (maximum magnetic flux density, coercivity, hysteresis loss and maximum differential permeability) as well as eddy current outputs (induced voltage, normalised impedance and phase angle) as a function of distance from the end-quenched surface were investigated and the results show a clear agreement with data obtained by traditional hardness testing. In addition, taking advantage of a generalised regression neural network, magnetic data obtained from hysteresis loop and eddy current methods could be used to accurately estimate results in the hardness profile of a given sample, using a few training data points. This paper shows that coupling the proposed non-destructive methods to Jominy end-quench test facilitates accurate non-destructive hardenability determination of steel samples while reducing time and cost of the test process.