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Elektropločevina je material, ki se uporablja za proizvodnjo in pretvorbo električne energije v mehansko, njena glavna značilnost pa so nizke magnetne izgube in visoka relativna permeabilnost. Glede na magnetne lastnosti in področje uporabe jo delimo na orientirano in neorientirano pločevino. Slednja se uporablja za izdelavo jeder v elektromotorjih, ki so prisotni na različnih področjih našega vsakdana. Na izkoristek električnih naprav vplivajo različni dejavniki, kot so debelina pločevine, kemijska sestava, tekstura, velikost kristalnih zrn in drugo. V magistrski nalogi smo raziskovali vpliv toplotne obdelave na magnetne lastnosti statorskih paketov iz gotove neorientirane elektropločevine. Zanimalo nas je predvsem, kako različni parametri žarjenja vplivajo na skupne magnetne izgube. Uporabili smo statorske pakete iz gotove pločevine kvalitete M600-50A HP. Vzorce smo izpostavili različnim pogojem toplotne obdelave, in sicer nežarjeni, žarjeni v eksotermni atmosferi na 800 °C ter žarjeni v reduktivni atmosferi plinske mešanice sestave 80 % N2 in 20 % H2 na temperaturah 600 °C, 700 °C, 800 °C oziroma 840 °C. Meritve magnetnih in drugih fizikalnih lastnosti smo opravili na statorskih paketih na napravi Brockhaus MPG 200D in iz rezultatov izrisali krivulje relativne permeabilnosti ter krivulje skupnih izgub. Izdelali smo metalografske obruse in s svetlobnim mikroskopom določili velikostni razred kristalnih zrn ter si ogledali deformirana področja, nastala zaradi štancanja. Na vrstičnem elektronskem mikroskopu smo določili debelino vmesne plasti med dvema lamelama in analizirali mikrokemijsko sestavo. Z metodo uklona povratno sipanih elektronov smo analizirali teksturo in usmerjenost kristalnih zrn ter določili velikost zrn glede na delež površine. Izvedli smo tudi meritve trdote (HV0,1) od reznega roba proti notranjosti in določili razdiralno silo T segmentov ter držno silo sponk. Electrical steel sheet is a material widely used for production and conversion of electrical energy into mechanical. Its main characteristics are low magnetic losses and high relative permeability. Depending on the magnetic properties and purpose of use, electrical steels are classified into two groups, grain-oriented and non-grain-oriented. The latter is used for making cores for electric motors that can be found in various areas of our everyday life. The efficiency of electrical machines is influenced by different factors, such as sheet thickness, chemical composition, texture, grain size and other. In this master’s thesis, we researched heat treatment effect on magnetic properties of stator stacks from fully-finished non-oriented electrical steel sheets. The focus was on how different annealing parameters influence the total magnetic losses. We used stator stacks made from fully-finished electrical steel sheet, which grade was M600-50A HP. The samples were exposed to different heat treatment conditions, namely non annealed, annealed in exothermic atmosphere at 800 °C and annealed in a reductive atmosphere of gas mixture of 80 % N2 and 20 % H2 at temperatures of 600 °C, 700 °C, 800 °C and 840 °C, respectively. Measurements of magnetic and other physical properties were performed on stator stacks using Brockhaus MPG 200D machine. From results we then plotted the curves of relative permeability and total power losses. We prepared metallographic samples and determined their grain size classification using optical microscope. Deformed areas caused by punching were also observed. Furthermore, we determined the thickness of intermediate layer between the two lamellas and analysed its micro chemical composition with the help of scanning electron microscope. Using the electron backscatter diffraction method we analysed the texture and orientation of crystal grains and determined grain diameter in relation to area fraction. We also did the hardness measurements (HV0,1) from cutting edge towards the middle and determined the holding force of T segments and tear off force of interlock pins. |
