Numerical model of controlled cooling in production of steel hot rolled bars was developed. By numerical model of controlled cooling is possible to predict a transient temperature field, microstructure evolution and hardness of rectangular steel bars during their cooling in cooling beds. The numerical model of transient temperature field is based on control volume method. The algorithm for prediction of hardness and microstructure distribution in steel bars is based on continues cooling transformation, (CCT) diagrams and real chemical composition. The numerical model and algorithm is completed to solve problems in controlled cooling of hot rolled bars in cooling beds. The controlled cooling are performed by special placement of hot rolled bars on cooling beds. Numerical model and computer program was experimentally verified by simulation of real industrial production of low alloyed steel bars. The verification of developed numerical model was performed by comparison of simulated hardness with experimentally evaluated results.

The mathematical model and computer simulation for the prediction of mechanical properties in quenched and tempered steel specimen was developed. In addition, mathematical model for prediction of microstructure composition of quenched and tempered steel was developed. In calculation of both, mechanical properties and microstructure composition the history of cooling was taken in account. Hardness of quenched and tempered steel was expressed as function of maximal hardness of actual steel and representatives of chemical diffusivity. After that, distribution of other relevant mechanical properties can be obtained. The mathematical model is developed for carbon and low alloyed steel. The studied model is based on Jominy test results. The established procedure was applied in computer simulation of quenched and tempered steel workpiece.