21 KB707 KB18 KB200020242013Bořuta, JosefKubina, TomášPernis, Rudolfštevilka:4letnik:47str. 519-523COBISSID:1005994ISSN:1580-2949URN:URN:NBN:SI:doc-SSUPGCZNenInštitut za kovinske materiale in tehnologijeMateriali in tehnologijebrassflow stresshot formabilitymedipower-dissipation mapsstrain ratetečenjetorsion testvroče preoblikovanje kovinConversion of the Ms70 alpha-brass torsion-test data into hot-forming processing maps| Pretvorba podatkov torzijskega preizkusa alfa medi Ms70 v procesne zemljevide vroče predelave|The present paper gives a summary of the plastic behaviour of the Ms70 deep-drawing cartridge brass under the hot-forming conditions explored by using a SETARAM-Vítkovice torsion plastometer. The specimens were cut from the hot-extruded and, subsequently, cold-drawn brass bars. Formability tests were performed on the diameter 6 mm specimens at (650, 700, 750, 800 and 850) °C and at the speeds of (16, 80, 400 and 800) r/min. These testing conditions are equivalent to the conditions of the ordinary industrial hot extrusion of brass: the single most problematic operation in the manufacturing process in terms of an occurrence of serious defects. The results of the torsion tests were converted into the conventional format: the maximum flow-stress levels vs. the peak-strain intensity. The points thus obtained can be used for finding the activation energy for forming Q, which is useful for determining the thermally compensated strain rate with the aid of the Zener-Hollomon Z parameter. The power-dissipation maps with the axes showing the deformation temperature and logarithmic strain rate were computed using a dynamic material model. The calculation of the dissipation efficiency was verified by comparing it with the known data on the 30 % zinc brass. The maps constructed in this manner allow the data from the torsion and compression plastometers tobe compared. The paper also includes a discussion of the changes in the processing maps at higher strains showing the optimum regions for the hot extrusion of brassV članku je povzetek plastičnega vedenja globokovlečne medi Ms70 pri vroči predelavi z uporabo torzijskega plastometra SETARAM-Vítkovice. Vzorci so bili izrezani iz vroče iztiskane in nato hladno vlečene palice iz medi. Preizkusi preoblikovalnosti so bili izvršeni na vzorcih premera 6 mm pri temperaturah (650, 700, 750, 800 in 850) °C in hitrostih (16, 80, 400 in 800) r/min. Te razmere pri preizkusih so enakovredne tistim pri navadnem industrijskem iztiskanju medi; najbolj problematični operaciji pri procesu izdelave zaradi pojava hujših poškodb. Rezultati torzijskih preizkusov so bili pretvorjeni v navadno obliko: maksimalne natezne napetosti proti največjemu raztezku. Tako dobljene točke se lahko uporabi za izračun aktivacijske energije preoblikovanja Q, ki je uporabna za določanje toplotno kompenzirane hitrosti trganja z uporabo Zener-Hollomon Z-parametra. Zemljevidi spreminjanja moči z osmi, ki prikazujejo temperaturo deformacije in logaritem hitrosti preoblikovanja, so bili izračunani z dinamičnim modelom materiala. Izračun spreminjanja učinkovitosti je bil preverjen s primerjavo poznanih podatkov za med s 30 % cinka. Tako konstruirani zemljevidi omogočajo primerjavo podatkov iz torzije in plastometra. Članek vključuje tudi razpravo sprememb v zemljevidih procesiranja pri višjih napetostih in prikazuje optimalna področja za vročo ekstruzijo mediTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije