Investigation of microstructural and mechanical properties of hot forged 31Mn4 dual phase steel with computer-aided simulations

Abstract

ABSTRACT In this study, it is aimed to realise the hot forging process design and prototype production of the steel yielding support connection clamp, the critical safety element of underground mining ground support systems, by using 31Mn4 dual phase steel. In this context, at the end of the forging and deburring processes, air cooling was designed, simulated and cooling rates were obtained. The cooling curve was integrated into the continuous cooling transformation diagram and phase formation was predicted. The distribution of pearlitic, ferritic, bainitic structures and formation rates, hardness distributions, strength data were also obtained. The hardness and tensile strength calculations, microstructural examinations and SEM analysis were carried out for validation. It has been determined that pearlitic-ferritic microstructures are formed in regions where the cooling rate is slow. In thinner sections where the cooling rate is around 1.2°C/sec, ferritic structures become smaller and bainite phase was observed. As a result, the average tensile strength in 1st and 2nd regions were recorded as 684.5, 690 MPa in simulation, while these values were recorded as 688.45 and 694.15 MPa in tensile tests. It has been determined that this result corresponds to the 99.4% accuracy rate of the prototype obtained by simulation-supported and real productions.