Browsing by Author "CABRERA CONTRERAS, MANUEL JOSÉ"
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Thesis OBTENCIÓN DE MICROESTRUCTURAS AUSFERRITICAS EN ACEROS FUNDIDOS DE MEDIO CARBONO Y BAJA ALEACIÓN(Universidad Técnica Federico Santa María, 2016) Pérez Franco, Jemael Sidharta; Universidad Tecnica Federico Santa Maria UTFSM DEPARTAMENTO DE INGENIERÍA METALÚRGICA Y DE MATERIALES; CABRERA CONTRERAS, MANUEL JOSÉ; TELLO ARAYA, KAREM EVAAs the mining industry in Chile continues increasing the necessity of milling equipment becomes larger. As an example, currently SAG mills liners undergo higher impact and abrasion wear which requires higher hardness and toughness. Both composition and microstructures of the steels have varied very little along the year to adjust to the new conditions of performance. The microstructures range from pearlite (fine to coarse) to tempered martensite. Current heat treatments of these steels seek to avoid bainite formation which is a complex task because larger parts have higher thermal inertia resulting in different microstructures between the surface and the interior of a component. A microstructure that could improve the performance and satisfy the demands of SAG mill liners could be ausferrite; which is a low cost microstructure, biphasic that combines high strength and toughness. Ausferrite is formed by relatively rapid cooling from the austenite phase. The high strength of ausferrite is achieved by avoiding carbide formation, which is accomplish by using silicon or aluminum as alloy elements that delays the formation of carbides. Ausferrite was obtained in several samples of steel after modifying a base alloy used in mill liners. This was accomplished by increasing the silicon content above 1 wt.%. Samples were cast and then subjected to subjected to isothermal heat treatment in the bainitic transformation temperature range. Later, the microstructure was characterize using optical microscopy and hardness profiles were obtained from representative samples. The best results were obtained after isothermal treatment at 300 °C, with ferrite plates of less than 2 microns thick and less than 100 microns long. This steels with ausferrite in their microstructure could replace the steel used currently in SAG mill liners.
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