Poškodbe jeklenih valjev s povišano vsebnostjo kroma med vročim valjanjem : diplomsko delo

Mulh, Miha (author), Fajfar, Peter (mentor), Drobne, Matej (co-mentor)

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.

• Language: Slovenian
• Keywords: delovni valj, toplotno utrujanje, razpoke, karbidi.
• Work type: Bachelor thesis/paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: NTF - Faculty of Natural Sciences and Engineering
• Place of publishing: Ljubljana
• Publisher: [M. Mulh]
• Year: 2022
• Number of pages: IX, 28 str.
• PID: 20.500.12556/RUL-142919
• UDC: 669
• COBISS.SI-ID: 132331523
• Publication date in RUL: 02.12.2022

Secondary language

• Language: English
• Title: Damage in the high chromium steel work during hot rolling : diploma work

Abstract

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.

• Keywords: work roll, thermal fatigue, cracks, carbides.