ANALYTICAL FINITE-ELEMENT MODELING AND EXPERIMENTAL-VERIFICATION OF SPRAY-COOLING PROCESS IN STEEL/

An atomizer is a helpful tool that can be used to tailor the cooling r ate of steel from the processing temperature in order to get desired p roperties. It is important to determine the temperature distribution i n a specimen subjected to cooling by an atomized spray. A finite-eleme nt model for transient heat transfer and thermal-stress analysis is de veloped to determine the temperature and thermal-stress distribution. The results of the finite-element heat-transfer model are compared wit h a finite-difference model. The heat-transfer model describes the hea t-transfer processes in an AISI 4140 steel cylinder subjected to contr olled atomized spray cooling from an initial temperature of 1273 K. Th e temperature fields predicted by the model are used both to predict t he resulting microstructure using continuous cooling transformation (C CT) diagrams and as an input for the thermal-stress model to predict t he occurrence of quench cracks. The thermal-stress model incorporates temperature-dependent material properties, heat generation due to phas e changes, elastoplastic behavior of steel, and the volumetric expansi on associated with the formation of martensite. The results of the fin ite-element model are verified experimentally by recording temperature profiles, obtaining micrographs, and recording the occurrence of quen ch cracks.