Formation of the structure of steel 08KH18N10t during pilgrim rolling and following annealing

In this work was studied kinetics of post-deformation softening of 08Kh18N10T steel (analog of AISI 321) in the temperature range 1000-1200 °C by the double deformation method. Samples made from the steel of fusil with a relatively high mass fraction of carbon (%C = 0,07) and titanium (%Ti = 0,50). The two-pass hot compressive tests were performed on a Gleeble 3800 thermo-mechanical simulator. It is shown that at temperatures around of 1000 °C in 08Kh18N10T steel with considered chemical composition, both dynamic recrystallization and post-deformation recrystallization are suppressed. Also was shown that at bigger temperature, namely at 1100 °C, and moreover 1200 °C post-deformation recrystallization going faster, and for full recrystallization needs only a few ten seconds. According to the results of industrial observations, due to the contact of the workpiece body with a massive mandrel, the inner surface of the workpiece metal cool down, as a result of which their deformation occurs at a temperature around at 1000 °C. This circumstance is the reason for the preservation of large deformed grains in the structure of seamless pipes near their inner surface. An increase in deformation to a value of 1.3 by von Mises in model experiments increases the driving force of post-deformation recrystallization and provides a completely recrystallized structure in steel after annealing at 1000 °C. On the basis of the results obtained, changes in the technology of rolling seamless pipes made of 08Kh18N10T steel for the needs of nuclear power are proposed. These changes imply an increase in the deformation value up to 1.1 von Mises (only up to 1.1 due to the technical limitations of the mill), which made it possible to exclude rejection by grain size. Rolling pipes along an experimental route has shown its effectiveness.