24 KB725 KB23 KB200020242004Bosnjak, BrankaRadulović, Brankoletnik:38številka:66 stranistr. 307-312ISSN:1580-2949COBISSID:364714URN:URN:NBN:SI:doc-8P1G0RE5enInštitut za kovinske materiale in tehnologijeMateriali in tehnologijeavstenitizacijamikrostrukturanodularna litinaEffect of austenitising temperature on austempering kinetics of Ni-Mo alloyed ductile iron|The effect of austenitising temperature on the transformation kinetics of Fe-3.2C-2.68Si-0.07Mn-0.022P-0.003S-0.02Cu-0.12Cr-0.8Ni-0.25Mo mass fractions ductile iron was investigated. X-ray diffraction and optical microscopy were used to determine the transformation kinetics during the austempering at 350 compositumC after austenitising at 850 compositumC and 930 compositumC for 120 min. The stage I reaction of austempering occurs in two steps, first in eutectic cells and than in the intercellular area. Decreasing the austenitising temperature is shown to increase the driving force for the stage I reaction but to have little effect on the stage II reaction. By lower austenitising temperature the rate of transformation is greater, a more uniform microstructure is obtained, while the austemperability is smaller. These changes shift the processing window for Ni-Mo ductile iron for selected austenitising temperatureRaziskan je bil vpliv temperature avstenitizacije na kinetiko premene nodularne litine Fe-3,2C-2,68Si-0,07Mn-0,022P-0,003S-0,02Cu-0,12Cr-0,8Ni-0,25Mo. Kinetika premene pri 350 kompozitumC po avstenitizaciji pri 850 kompozitumC, 900 kompozitumC in 930 kompozitumC je bila določena z optični mikroskopijo in difrakcijo rentgenskih žarkov. Prva stopnja premene se izvrši v dveh fazah, najprej v evtektičnih celicah in nato med temi celicami. Pri znižanju temperature avstenitizacije se poveča gonilna sila za prvo stopnjo premene, ki ima majhen vpliv na drugo stopnjo premene. Pri nižji temperaturi avstenitizacije je večja hitrost premene in nastane bolj enakomerna mikrostruktura, vendar je manjša sposobnost litine za avstempering. Te spremembe premaknejo procesno okno za nodularno litino Ni-Mo za izbrano temperaturo avstenitizacijeTEXTznanstveno časopisjejournalsSlovenian National E-content AggregatorNational and University Library of SloveniaInštitut za kovinske materiale in tehnologije