DIAGRAMS OF THE HOT AND WARM DEFORMATION AND STRAIN AGING OF NITROGEN-BEARING AUSTENITIC STEELS

Current requirements on the quality of metal products and structures are leading to a rapid increase in the production of alloy steels as a percentage of all of the iron alloys that are made. Recent years have seen significantly more interest being shown in high-nitrogen alloy steels (HNSs), particularly those that are resistant to corrosion [1]. One of the main advantages of these steels compared to analogous conventional steels is their higher strength. This makes it possible to reduce the volume of production of high-alloy steels 10 – 20% as a result of a reduction in the working cross section of machine parts, mechanisms, and structures, since such a reduction also decreases the amount of material that these elements contain. The process of alloying iron alloys with nitrogen in large quantities requires the use of special production processes, which is one of the factors that raises the steelmaking costs. However, since nitrogen has a high capacity for stabilizing austenite, alloying with nitrogen makes it possible to reduce stainless steels’ content of austenite-forming elements — nickel and manganese — by a factor of 1.5 – 2 or even avoid adding these elements at all. The introduction of nitrogen into steel not only makes them stronger and saves alloying elements, but it also solves environmental problems. Being a component of air, nitrogen is inexpensive, and the process of extracting it from air does not require the surface and subsurface mining necessary to obtain ores. At the same time, strengthening austenitic steels with nitrogen inevitably increases the load on the equipment that is used to process those steels. The high nitrogen content can significantly alter aging processes — particularly strain aging — in high-alloy steels and thus influence the choices made for the processing regimes and areas of application. In particular, the high nitrogen content can affect decisions to use such steels in applications which require that the steel have high ratings for certain special properties — especially resistance to corrosion. The goal of the investigation being discussed in this article was to study how commercial nitrogen-bearing austenitic steels alloyed by different systems behave mechanically during hot and warm deformation.