Effect of sample geometry on tensile properties of chomium alloyed middle carbon steel

42SiCr steel is a middle carbon, low alloyed steel with (in wt. %) 0.4C, 1.3Cr, 0.6Mn and 2Si. In this work, the steel was used in hot rolled state, possessing bainite-based microstructure. In development and optimization of heat and thermo-mechanical treatments, small volumes of materials are commonly processed in various simulators or dilatometers. This means that smaller samples for mechanical testing are also necessary and question arise how exactly various sample geometries affects measured mechanical properties, particularly ductility. Four types of samples for tensile test were used for the comparison. Three of them were flat, with various cross sections and active lengths of 15, 20 and 50 mm. The same thickness of 1.2 mm was kept for all three types of flat samples. For a reference, a sample with circular cross section with 5 mm diameter and 25 mm active length was tested as well. Zwick Roell Z250 was used to perform tensile tests, according to ČSN EN ISO 6892-1. Six samples of each dimension were tested and used for calculation of average values of tensile properties. Following intervals of tensile properties were obtained: yield strengths of 721-766 MPa, ultimate tensile strengths of 1205 - 1335 MPa and total elongation of 15-19%. The highest elongation was measured for circular samples, while the highest ultimate tensile strength was achieved in the flat sample with active length of 20 mm