26 SCIENTIA AGRICULTURAE BOHEMICA, 46, 2015 (1): 26–32 AGRICULTURAL ENGENEERING INTRODUCTION Quenching is a thermal process frequently used to obtain good mechanical properties of steel and other metal alloy materials. The quenching application of the material is subjected to heat treatment above the austenitization temperature (approximately 900°C) involving continuous and rapid cooling in a quenching media including water, air, and oil (C h o t ě b o r s k ý , 2013). Based on the heat treatment of the material, S u g i a n t o et al. (2009) compared two different tech- niques of heat transfer capacity (HTC) determination. These include the lumped heat capacity method and the inverse heat transfer method. B u c z e k , T e l e j k o (2004) performed experiments under various cooling conditions through position of the active surface of the sample, its initial temperature and water temperature. Heat transfer of the sample–quenchant interface in other media than water was investigated using brine, water, mineral, and palm oils and other vegetable oils (F e r n a n d e s , P r a b h u , 2007, 2008). Quenching fluids such as polymer–water solutions and nanoflu- ids have also been used by some authors (C o u r s e y et al., 2008; B a b u , P r a s a n n a K u m a r , 2011; E s h r a g h i - K a k h k i et al., 2011). However, the quenching fluids that have been used were defined by the quenchant temperature and the heat transfer coef- ficient at the cooling surface. During quench hardening, heat flux transfers rapidly to the coolant which varies in time, hence the HTC cannot be calculated or measured by standard techniques. In such cases, the most suitable procedure is the formulation of the boundary inverse heat conduction (B u c z e k , T e l e j k o , 2013). This method consists of numerical selection of boundary conditions to provide temperature distribution in the material within limits of accuracy based on known data. The temperature profile is measured by sensors placed at selected internal points of the material during cooling. To determine the heat transfer coefficients of the material at the cooling surface, lumped heat capacity approximate technique has been applied at constant work piece temperature. K o b a s k o et al. (2004) experimen tally determined the first and second critical heat flux densities to characterize the quenching process. Most useful method for obtaining the realistic metal/quenchant interfacial heat transfer properties is the inverse modelling which allows the determination of boundary conditions by the coupling of numerical methods with simple temperature mea- surements inside the quench probe. The objective of * Supported by the Internal Grant Agency of the Faculty of Engineering, Czech University of Life Sciences Prague (IGA), Project No. 2014: 31200/1312/3130. PREDICTION OF MECHANICAL PROPERTIES OF QUENCH HARDENING STEEL * R. Chotěborský, M. Linda Czech University of Life Sciences Prague, Faculty of Engineering, Prague, Czech Republic The present study investigated the application of finite element method for prediction of mechanical properties of quench hardening steel. Based on the experimental results obtained, a numerical model for simulation of continuous cooling of quench hardening steel was developed. For the simulation of the kinetics of diffusion phase transformations, the Avrami equa- tion and additive rule were applied. A new model was also developed for martensitic transformation which was validated using metallographic analysis and hardness tests. Experimental and simulation results indicated a good agreement. The devel- oped model information provided here could be used for simulation of continuous cooling and kinetics phase transformation as well as for prediction of final distribution of microstructures and hardness of alloy steels. finite element model; heat flux; microstructure; hardness; continuous cooling doi: 10.1515/sab-2015-0013 Received for publication on March 24, 2014 Accepted for publication on January 14, 2015