Comparison of Metallurgical Models During Quenching Using Open Source Software

Abstract

Quenching process is applied to steels pieces to improve their mechanical properties, enhance hardness and strength, obtaining desired microstructure distribution, while maintaining geometrical distortion and residual stresses within specification. This type of heat treatment is widely used in metal-mechanic industry.
The quenching process involves different physical fields: thermal, metallurgical and mechanical. Problem complexity increases as a consequence of physical fields interaction. Therefore, affecting mechanisms must be completely determined, and appropriate models elaborated if accurate predictions are pursued.
Waeckel’s metallurgical transformation model is based on the numerical integration of the phase transformation’s rate. Phase fraction evolution is solved by considering continuous cooling diagrams (CCT) and interpolating already known experimental thermo-metallurgical histories. On the other hand, Johnson-Mehl-Avrami-Kolmogorov (JMA-K) isothermal transformation model, is applied to continuous cooling by discretizing it as a succession of isothermal steps, in addition to an additivity rule to define the onset of transformation.
This article focuses on the resolution of an eutectoid steel piece. The effect of different metallurgical transformation models on final properties after quenching is assessed. Open-source thermo-mechanical and metallurgical software, Code_Aster, which already has Waeckel’s transformation model built-in, is adapted to implement the JMA-K scheme.