Modely deformačních odporů nástrojové oceli 19 552 za tepla

Abstract

Steel 19 552 ranks among the most used tool steels intended for working in the hot state. The steel is used for tools intended for hot pressing and moulds intended for casting under ressure, especially in the field of processing of light metals. The main objective of this diploma work was based on an experiment to get the model mean flow stress (MFS). Deformation resistance values were obtained from the measured rolling forces when the flat staggered samples had been rolled at temperatures 800 – 1150 °C and strain rates 8 – 88 s-1 in laboratory mill Tandem. The resulting model describes with a good accuracy MFS values of the investigated steel in relation to temperature, strain and strain rate. Utilization of possibilities of torsion plastometer in Vítkovice – Výzkum a vývoj, s.r.o. company led after evaluation of measured results to obtaining the required information about deformation resistance and kinetics of dynamic recrystallization of examined material. Activation energy for the type of steels was determined on the basis of performed set of plastometric hot tests. The final part is concerned MFS compared with the torsion test model that was applied in the laboratory rolling. This comparison showed a not very good conclusion. The main reason lies in the strain rates, which were used in torsion tests.