Simulation of manufacturing processes to predict properties of fossil-free steel alloys

In this part of the project, the developed material, microstructure, and diffusion models from project activity 1.5 are applied in a welding simulation. These models allow for the prediction of the final properties of the steel after the welding process. The welding simulation consists of a thermomechanical model. In the thermal part of the model, the temperature history of the entire sheet is simulated during and after welding. By linking the thermal model to the mechanical model, it is possible to predict deformations and residual stresses that arise in the welded plates.

With the developed simulation model, it is possible to better understand why the properties change in a certain way and how they are influenced by different process parameters. To achieve the correct material behaviour in the material model, accurately predicted temperature histories are required, which are verified through experiments. The temperature history also determines which phase transformations will occur and how quickly they take place. Additionally, temperature affects the diffusion rate of hydrogen, which can be linked to the risk of hydrogen embrittlement. In the welding simulation, the microstructure and diffusion models are integrated into the material model to improve the accuracy of predicting deformations and residual stresses in the welding process.

Welding tests have been carried out in collaboration with SSAB Oxelösund to develop and validate the models. In the welding tests, two spot-welded sheets are welded in a butt joint. Since one of the sheets is fixed, the other sheet deforms by bending upwards. The deformations are measured and will then be compared with the modelling results. Temperatures are also measured using thermocouples.