Characterization of the austenite recrystallization by comparing double deformation and stress relaxation tests

A high amount of deformation below the non-recrystallization temperature (T-nr) is a common industrial practice to achieve a good combination of toughness and strength in microalloyed steels. To combine the industrially relevant optimum combination of high productivity and product quality, an accurate knowledge of T-nr and the recrystallization kinetics is required. Although a lot of literature data is available on the recrystallization behaviour of microalloyed steels, correlations are often difficult to be made due to the effect of different experimental setups, types of analysis and test schedules that are used to obtain this data. Although this would significantly improve the knowledge about these steels, so far, no systematic comparison has been presented in literature to correlate the different techniques and methods. In this study, different hot rolling simulation techniques, testing schedules and types of analysis were used to determine the recrystallization kinetics of a microalloyed steel. On the one hand, good agreement was found between the results from different test equipment for the double deformations tests. On the other hand, stress relaxation tests showed accelerated kinetics and appeared to be less effective

Izračunavanje otpora deformacije nisko ugljičnih čelika tijekom toplog valjanja

Deformation behaviour of low carbon steels under hot rolling service conditions is predicted utilising a combination of isothermic single step deformation test, anisothermic interrupted test and hot rolling simulation performed on torsion plastometer. The stress s0.05 at strain level e = 0.05 and the restoring factor fr are proposed to be used for the description of the strengthening / restoring process during repeated deformation.Deformacija nisko ugljičnih čelika tijekom toplog valjanja izračunava se kombinacijom jednokoračnog izotermnog testa na deformaciju, prekinutog testa i simulacije toplog valjanja izvedene na torzionom plastometru. za opis procesa jačanja/obnavljanja tijekom ponavljanja deformacije predlaže se uporaba naprezanja s0.05 na nivou deformacije e = 0.05 i faktora obnavljanja fr

Novi oblik jednadžbe za izračunavanje otpora deformacije u industrijskim uvjetima toplog valjanja

A new equation for the prediction of steel deformation resistance under industrial hot rolling conditions is proposed. This new expression can be used for more accurate description of material deformation behavior at service conditions utilizing data from laboratory plastometer experiments.Predlaže se nova jednadžba za izračunavanje otpora deformacije čelika u industrijskim uvjetima toplog valjanja. Novi izraz se može koristiti za točniji opis deformacije materijala u radnim uvjetima za što se koriste podaci dobiveni laboratorijskim eksperimentima s plastometrom

VVER long-term operation – A review based on the material studies results from past and ongoing EU-supported research projects

Safe and long-term operation (LTO) of nuclear power plants (NPP) with Water-Water Energetic Reactors (VVER) is essential for several central and eastern European countries to keep their energy supply security. During the last decades, several EU-supported projects in framework projects or Horizon2020 schemes have focused on the material degradation of pressurised water reactors (PWRs), especially VVERs. This paper aims to extract the most important results dominantly from EURATOM projects which support or could limit the long-term operation of this Soviet design of PWRs. The accent is given on ongoing projects such as FRACTESUS, STRUMAT-LTO, APAL, and ENTENTE. Actually, running project DELISA-LTO (2022–2026) comprises not only results from previous research in this area but also incorporates wide material databases coming from nuclear power plant V-1 in Jaslovské Bohunice (Slovakia), which was shut down after 28 years of operation and provides wide-range of original service-aged materials specimens for profound material studies having in mind lifetime extension of VVERs. Consolidated knowledge focused mainly on the reactor pressure vessel (RPV) material studies is summarised and supported by relevant references.</p