Investigation into oil quenching processes of steels to improve sustainability by experiments and multi-physical modelling

The work in this thesis centres around the quenching process, a specific phase in the manufacturing of metal components. This integral industrial task is analysed and discussed in the context of sustainability in manufacturing using the recently developed framework known as the 6R theory, which individuates the six pillars of Reduce; Reuse; Recover; Redesign; Re-manufacture; Recycle. The research and experimentation discussed concentrate on a virtualisation of the quenching process to investigate different methods and materials and the possible implications their adoption could have for industry. Findings are framed in the construct of 6R theory, in particular the Reduce factor. The research projects presented were conducted at length, in-depth and often manually carried out, focussing on the dimensional and shape variations induced by quenching processes and aiming to precisely define machining allowances and reduce the amount of raw-material utilised to achieve final design requirements. A multi-physical quenching model was realised to predict the distortions occurring in a standard manufacturing cycle. The model, aided by physical experimental activities, focused on the evaluation of deformations and took into account part geometries and steel types. A comparison between mineral and vegetable quenching oily mediums was also conducted. The software application employed was tailor-made, using a layered physics approach to predict the behaviour of the processed part. Results show that the calculated deformations throughout the virtual quenching cycle accurately reflect the trends of the experimental distortions. A large amount of data was collected allowing for accurate tuning of the mathematical model to fully replicate the experimental findings. Both hardening and carburising materials were experimentally investigated to highlight differences in terms of their behaviour and dimensional variations. A comparison between traditional and die assisted oil quenching processes was also carried out, assessing the extent of dimensional and shape variations induced by the mould-aided process.