Modeling of distortions after carburization and quenching processes of large gears

Abstract

A new finite element model is developed to predict the deformations, stresses, phase compositions and carbon concentration gradients that arise as a consequence of the physical processes involved in a carburization and quenching process of a large steel gear. Firstly, the diffusion of carbon at elevated temperatures in the austenitic range is studied in a diffusion model. Secondly, the calculated carbon concentration distribution is used as an input for a model that couples the thermal, metallographic and mechanical effects during the quenching process and calculates the evolution of the temperature, phase composition and deformation history at any point in the gear. Two effects typical for oil quenching of large gears are incorporated in the model. The first is the influence of the gear's own weight while hanging on chains before, during and after entering the quench bath. The second is the three-dimensional effect that it takes time between the moment the gear enters the oil quenching bath and the moment when the gear is fully immersed. The non-uniform temperature distribution over the gear's axis causes a non-homogeneous plastic deformation. A diffusion-thermo-metallo-mechanical model that takes these effects into account is compared with a model that does not. The results show that these effects should be incorporated.

Meshing Simulation and Strength Calculation of a Carburized Gear Pair

“…Kim and Bae [13] analysed the gear deformation in different quenching temperatures during carburizing-quenching simulation and provided process parameters for actual production. Decroos and Seefeldt [14] established a half-gear tooth finite element model to simulate the process of carburization and quenching, and predicted the gear stress and strain after this process. Li et al [15] simulated various residual stresses during carburization and quenching.…”

The Effect of Size on the Distortion Behavior After Carburisation and Quenching Processes of Gears

“…For a given alloy with a certain carbon concentration C, the transformation starting and finishing curves for each phase of the TTT diagram can be interpolated by a 2nd order polynomial giving the relationship between the logarithm of the time t as a function of the temperature T given by equation 11 [9]: (1 0.01) ( )…”

“…(17) Hereby f I is the transformed fraction, K is a constant, s ij is the deviatoric stress. In reference [9], it is explained how to implement TRIP in a commercial FE software package.…”

“…The way to implement phenomena, such as the calculation procedure for the carbon concentration, Transformation Induced Plasticity, and gravity in a commercial Finite Element code has been explained in reference [9]. In 3D FE analysis, one commonly assigns a material to a volume of the solid model.…”

“…Current research focusses on both large and small gears and includes effects that are typical for the 3 dimensional larger problems, like the gravitational effects, and the gear's immersion time in the quenching bath. Decroos et al showed how these effects, as well as the Transformation Induced Plasticity (TRIP) strain can be included in a commercial Finite Element software [9].…”