Previous studies have pointed out the need to properly characterize industrial quenching processes to account for the inherent heterogeneities of the process. This study focuses on the identification of thermal boundary conditions of a hollow cylinder quenched by immersion in mineralized oil previously subjected to a predefined air transfer step. The test specimen is instrumented with in-body thermocouples at multiple locations along the radial and azimuthal direction thus mapping the outer and inner surfaces of the hollow cylinder. Based on the experimentally acquired datasets, characteristic points of physical significance during the cooling regimes after immersion are identified to produce time dependent analytical cooling curves. An inverse identification method is applied to estimate heat flux and temperature dependent heat transfer coefficients at locations of interest in both inner bore and outer surfaces. Results demonstrate the non-homogeneous cooling of the specimen during the quenching process before immersion (air transfer) and after immersion in the quenchant, hence confirming the importance of accounting for the influence of the industrial environment. The results are also compared with previous characterization data obtained with a plate probe for the same facilities thus capturing the influence of probe geometry on the identification of thermal boundary conditions.

Standard laboratory test methods are useful to compare the cooling performance and cooling regimes of different quenchants under controlled environments where quenching occurs almost immediately. In reality, many industries rely on systems that require transferring through air from the austenitizing furnace to the quench tank. In this project, a special quench probe apparatus is used to characterize an industrial quenching process involving air transfer followed by quenching in low viscosity oil. The probe system allows investigation of the non-homogeneous condition before immersion. The heterogeneity of the process, through air and in the oil, is captured by modifying the position and orientation of the quench probes among many experiments. Multiple characteristic points were identified during the boiling stage due to its physical significance to produce time dependent analytical curves built up through piecewise polynomial interpolation while an optimization algorithm models the convective stage. Inverse analysis is carried out with the data captured by the probes to estimate time dependent temperature boundary conditions. The output can further be computed into a temperature dependent heat transfer coefficient curve. Results indicate that the phenomena occurring after immersion differ from laboratory results thus demonstrating the significance of characterizing the actual industrial process.