Steel 34CrMo4 is world widely used steel type for the variety of products, for example forgings, castings, shafts, bars etc. Desired mechanical properties of mentioned steel can be achieved by various treatments such as in a metallurgical process by titanium, niobium, vanadium, zircon or nitrogen microalloying. Another suitable way how to achieve desired mechanical properties is use of different heat treatment modes due to excellent hardenability and temperability of steel 34CrMo4 or combination of these methods in thermomechanical forming. To achieve the best combination of mechanical properties, the grain size is the one of the most important microstructural parameters. In this article, the development of 34CrMo4 steel grain size together with the microstructure after four treatments of the material including as hot rolled state, after normalization annealing, normalization annealing with subsequent quenching and tempering and as final treatment of quenching and tempering were evaluated in relation to achieved values of mechanical properties after each treatment. Except the grainsized and microstructural investigation, as it was mentioned, also the evaluation of mechanical properties was a part of the experimental procedures. This procedure revealed that the most favorable and balanced mechanical properties (tensile strength of 1172 MPa vs. 61 J·cm-2 of CVN (at - 50 °C) and elongation of 16.1 %) in case of the treatment based on the quenching and tempering processes applied after the hot forming were achieved. Other treatment types also showed favorable results of mechanical properties however always lower in comparison with the above mentioned treatment.Keywords: steel 34CrMo4, grainsized, mechanical properties, heat treatment
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