Metallic materials, especially steels, are undertaken to different heat treatment processes in industry and cooling and heating times are of great importance. In this study, influence of variable physical properties of ANSI 1025 and AISI 304 steels and different boundary conditions namely forced convection, free convection and radiation on the calculation of cooling process was investigated. Governing differential equations were solved numerically for non-steady cases. It was found that variable properties should be taken into consideration for ANSI 1025, while the physical properties determined at an average temperature can be used for AISI 304. Another conclusion is that free convection can be neglected compared with radiation especially if forced convection coefficient is low. (c) 2005 Elsevier Ltd. All rights reserved.