This master's thesis deals with the testing of a cerium-rich inoculant on a high-speed steel alloy used for the working layers of the rolls of a hot rolling mill. Two rolls were cast on an industrial scale at Valji d.o.o. company The aim of the master’s thesis was to investigate the influence of the inoculant on the microstructure of the aforementioned high-speed steel and thus its effects on the mechanical properties.
As part of the experimental work, two work rolls were cast with a working layer of high-speed steel. The melt of the working layer of one roll was inoculated with a cerium-based inoculant, while the melt of the working layer of the other roll was not inoculated. During the production process, simple thermal analyses were performed using the ATAS MetStar® software environment. In addition, simulations of the alloy solidification were carried out using the Thermo-Calc software. The microstructures of the working layer of both rolls were analysed in the as-cast state using optical and SEM microscopy. The size, shape, proportion and distribution of the carbides were compared. Subsequently, test specimens were produced from the machined segments of the working layer of both rolls after heat treatment in order to test the mechanical properties. Various tests of the mechanical properties were carried out, such as: tensile tests, impact toughness tests, wear tests, and bending tests.
When the results were analysed, it was found that the inoculation had an influence on the shape, size, and distribution of the MC carbides. In the inoculated sample, these carbides were larger, had a more spherical shape, and were more uniformly distributed. It was also observed that inoculation resulted in a reduction in the total content of M2C and M7C3 carbides. No significant differences were observed in the analysis of mechanical properties, except for the values of the elastic modulus and the amount of worn material during the wear test. The inoculation had a favourable influence on two properties mentioned.
|
