20.500.12556/RUL-142919 Poškodbe jeklenih valjev s povišano vsebnostjo kroma med vročim valjanjem diplomsko delo Damage in the high chromium steel work during hot rolling diploma work Namen diplomske naloge je bil raziskati vpliv štirih različnih postopkov nadaljevanja procesa valjanja po odpravi tehnološkega zastoja na nastanek termičnih razpok valjev. Preizkus smo izvedli na termomehanskem simulatorju metalurških stanj Gleeble 1500D. Vzorci so bili odvzeti iz valjev s povišano vrednostjo roma. Razpoke se tvorijo zaradi tlačne in natezne napetosti, ki nastanejo zaradi segrevanja in ohlajanja materiala. Sama razpoka se pa širi po karbidih pri čemer njeno rast dodatno pospešijo oksidi. Vzorce smo termično utrujali pri temperaturah 500 °C, 600 °C in 700 °C. Simulirali smo štiri možne načine ohlajanja valjev po zastoju ter nadaljevanju valjanja: po zastoju, ohlajanje in pred izgraditvijo ohlajanje enkrat z zrakom drugič z vodo oziroma nadaljevanje valjanja po zastoju brez vmesnega ohlajanja ter končno ohlajanje valjev pred izgraditvijo z vodo ali z zrakom. Z uporabo mikroskopa smo prešteli število, izračunali gostoto ter določili povprečno dolžino razpok. The purpose of the diploma thesis was to investigate the influence of four different procedures for continuing the rolling process after the elimination of technological stagnation on the formation of thermal cracks in the rolls. The test was performed on the Gleeble 1500D thermo-mechanical metallurgical state simulator. Samples were taken from cylinders with an elevated chromium value. Cracks are formed due to compressive and tensile stresses that occur due to heating and cooling of the material. The crack itself spreads along the carbides, and its growth is further accelerated by the oxides. The samples were fatigued at temperatures of 500 °C, 600 °C and 700 °C. We simulated four possible ways of cooling the rolls after a standstill and resuming rolling: after stagnation with air and at the end with air, after stagnation with water and at the end with water, without cooling after stagnation and at the end with air and without cooling after stagnation and in the and with water. With the use of microscope, we counted the number of cracks, calculated the crack density and determined the average length of the cracks. delovni valj toplotno utrujanje razpoke karbidi. work roll thermal fatigue cracks carbides. true false false [M. Mulh] Slovenski jezik Angleški jezik Diplomsko delo/naloga 2022-12-02 09:00:03 2022-12-02 09:00:22 2022-12-05 13:46:08 0000-00-00 00:00:00 2022 0 Ljubljana 0 Ljubljana IX, 28 str. 0000-00-00 NiDoloceno NiDoloceno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 1970-01-01 669 90526 132331523 13285.pdf 13285.pdf 1 2CA1AB34ED0C3426FF1D161241FD901A 2df26ad92057fdd49a92a39cca56f901d0f290e9b2598938f62385afa86dca0c 3a4bcf51-7217-11ed-9c94-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=164462 Naravoslovnotehniška fakulteta 0 0 0