Graduate School

Projekt B3: Development of residual stresses and distortion during the heating step of case hardening

Person in Charge: Dipl.-Ing. Daniela Stancheva-Schwind
  Motivation and Objectives:
For the minimisation of the hard machining cost after the case hardening, it is necessary to predict the residual stresses and the distortion, resulting out of the combination of soft machining and heat treatment. Therefore, the intention of this project is to attach the single process steps of broaching and heat treatment, trough transferring the component condition after soft machining to the simulation model of the case hardening. Subsequently, the development of residual stresses and distortion during heating will be analysed by using the Finite Element Method.
Investigations Results
  • Parameter identification of SAE 5120 via tensile, compressive, torsion and high-speed tests
  • Dilatometer tests for the determination of ttt-diagrams of the initial state of SAE 5120 and the carburized states of 0.5 and 0.8 mass percentage carbon
  • Dilatometer tests to analyse the temperature-time-transformation behaviour of ferritc pearlitic SAE 5120 into austenite
  • Thermal aging tests to examine the thermal relaxation during heating
  • Mapping of the residual stresses and the distortion after soft machining onto the simulation model of case hardening
  • FEM-Simulation of the heating step of case hardening
  • Material modelling: ferritic pearlitic matrix (0.25 ferrite, 0.75 pearlite)
  • Thermal Relaxation at T > 100°C, change of the mechanism at  400°C (dislocation diffusion → volume diffusion)
  • Development of a MATLAB-tool for the mapping of residual stresses and distortion in cooperation with project C1